applied physiology & chemistry

Applied Physiology & Applied Physiology & ChemistryChemistry

RT 210RT 210

Unit BUnit B

Mechanics of Ventilation: Mechanics of Ventilation: Ventilation & RespirationVentilation & Respiration

Ventilation is air movement in and out of the Ventilation is air movement in and out of the lungs to allow external respiration to occurlungs to allow external respiration to occur

Respiration is gas exchange across a Respiration is gas exchange across a permeable cellular membranepermeable cellular membrane

External respiration is gas exchange External respiration is gas exchange between alveolar gas (between alveolar gas (airair) and capillaries ) and capillaries ((bloodblood))

Internal respiration is gas exchange Internal respiration is gas exchange between capillaries and the tissuesbetween capillaries and the tissues

The Lung - Thorax The Lung - Thorax RelationshipRelationship

Two opposing forcesTwo opposing forces Lungs tend to collapse due to elasticityLungs tend to collapse due to elasticity Chest wall tends to spring outChest wall tends to spring out Linked together by the pleura Linked together by the pleura

Negative pressure -4 to -5 cm H2ONegative pressure -4 to -5 cm H2O Parietal pleura lines chest wallParietal pleura lines chest wall Visceral pleura covers lungVisceral pleura covers lung Potential space between with small amount of Potential space between with small amount of

lubricant/pleural fluid between layerslubricant/pleural fluid between layers

Normal ventilation Normal ventilation pressurespressures

Inspiration, (intrapleural = -10 cm Inspiration, (intrapleural = -10 cm H2O, intrapulmonary -3 cm H2O)H2O, intrapulmonary -3 cm H2O)

Diaphragm contracts and flattensDiaphragm contracts and flattens Chest cavity expandsChest cavity expands Negative intrapulmonary pressureNegative intrapulmonary pressure Negative transairway pressureNegative transairway pressure Gas flows in through the mouthGas flows in through the mouth

Normal ventilation Normal ventilation pressurespressures

Expiration, (intrapleural = -5 cm H2O, Expiration, (intrapleural = -5 cm H2O, intrapulmonary = +3 cm H2O)intrapulmonary = +3 cm H2O)

Diaphragm relaxesDiaphragm relaxes Chest cavity recoils and decreases in sizeChest cavity recoils and decreases in size Slight positive intrapulmonary pressureSlight positive intrapulmonary pressure Gas flows out through the mouth Gas flows out through the mouth

Physics of VentilationPhysics of Ventilation

Law of LaplaceLaw of Laplace P = 2 ST/rP = 2 ST/r surface tension tends to collapse alveolisurface tension tends to collapse alveoli Surfactant allows different sized alveoli to Surfactant allows different sized alveoli to

be connected without smaller emptying into be connected without smaller emptying into the larger alveoli and collapsingthe larger alveoli and collapsing

PhospholipidPhospholipid Decreases surface tension of the alveoli Decreases surface tension of the alveoli Allows critical volume to be variable from alveoli Allows critical volume to be variable from alveoli

to alveolito alveoli

Compliance-measures Compliance-measures dispensability of the lungdispensability of the lung

Compliance of the Lung = change in Compliance of the Lung = change in volume divided by change in volume divided by change in pressure pressure

)(

)(

2OHcmpressure

litersvolumeCL


Total compliance = lung and thorax Total compliance = lung and thorax (lung is not measured out of thorax)(lung is not measured out of thorax)

Pulmonary compliance = 0.2L/cm H2OPulmonary compliance = 0.2L/cm H2O Thoracic compliance = 0.2L/cm H2OThoracic compliance = 0.2L/cm H2O Total compliance = 0.1 L/cm H2OTotal compliance = 0.1 L/cm H2O

thoracicCpulmonaryCtotalC

111


pressurepeak

volumeDynamic

Pressure is peak pressure during gas flow

pressureplateau

volumeStatic


Decreased or less compliance seen in:Decreased or less compliance seen in: Pulmonary consolidationPulmonary consolidation Pulmonary edemaPulmonary edema PneumothoraxPneumothorax Abdominal distensionAbdominal distension ARDSARDS Pulmonary fibrosisPulmonary fibrosis Thoracic deformitiesThoracic deformities Complete airway obstructionComplete airway obstruction


Compliance increasesCompliance increases Alveolar distensionAlveolar distension Alveolar septal defectAlveolar septal defect Obstructive disorders-CBABEObstructive disorders-CBABE

C = Cystic FibrosisC = Cystic Fibrosis B = BronchitisB = Bronchitis A = AsthmaA = Asthma B = BronchiectasisB = Bronchiectasis E = EmphysemaE = Emphysema

Compliance is inversely related to Compliance is inversely related to elastanceelastance Elastance is the property of resisting deformationElastance is the property of resisting deformation

Resistance Resistance

Resistance = Resistance =

Flow

essurePr

ResistanceResistance

LaminarLaminar Poiseuille’s Law states that flow rate Poiseuille’s Law states that flow rate

varies directly with radius of a tubevaries directly with radius of a tube Small changes in airway radius will Small changes in airway radius will

dramatically affect flow and resistancedramatically affect flow and resistance ½ decrease in diameter increases resistance by ½ decrease in diameter increases resistance by

16 times16 times Turbulent (non laminar or eddy flow)Turbulent (non laminar or eddy flow)

The higher the flow the more resistanceThe higher the flow the more resistance Resistance is also directly proportional to gas Resistance is also directly proportional to gas

densitydensity


TransitionalTransitional Tracheobronchial tree has both laminar Tracheobronchial tree has both laminar

and turbulent flow caused in part by the and turbulent flow caused in part by the directional changes in the conductive directional changes in the conductive airwayairway

Reynold’s numberReynold’s number Less than 2000 is laminar flowLess than 2000 is laminar flow 2000-4000 is laminar and turbulent or mixed 2000-4000 is laminar and turbulent or mixed

flowflow Greater than 4000 is turbulent flowGreater than 4000 is turbulent flow


ViscosityViscosity Pressure GradientPressure Gradient Bernoulli’s PrincipleBernoulli’s Principle Coanda EffectCoanda Effect

Lung VolumesLung Volumes

Relate to lung/thorax relationship, Relate to lung/thorax relationship, compliance and surface tensioncompliance and surface tension

Four volumes and four capacitiesFour volumes and four capacities IRV - Inspiratory Reserve VolumeIRV - Inspiratory Reserve Volume

Maximum inhalation following quiet inhalationMaximum inhalation following quiet inhalation Normally 3.1 LNormally 3.1 L

VT - Tidal VolumeVT - Tidal Volume Volume inspired or expired during quiet Volume inspired or expired during quiet

breathingbreathing Normally 0.5LNormally 0.5L


Four volumes and four capacities Four volumes and four capacities (cont)(cont)

ERV - Expiratory Reserve VolumeERV - Expiratory Reserve Volume Maximum exhalation following quiet exhalationMaximum exhalation following quiet exhalation Normally 1.2LNormally 1.2L

RV - Residual VolumeRV - Residual Volume Gas remaining in lung after maximum exhalationGas remaining in lung after maximum exhalation Normally 1.2LNormally 1.2L


Capacities - consist of 2 or more Capacities - consist of 2 or more volumes or capacitiesvolumes or capacities

IC - Inspiratory CapacityIC - Inspiratory Capacity Made of IRV and VTMade of IRV and VT Maximum inhalation following quiet exhalationMaximum inhalation following quiet exhalation Normally 3.6LNormally 3.6L

FRC - Functional Residual CapacityFRC - Functional Residual Capacity Made of ERV and RVMade of ERV and RV Gas in lung following quiet exhalationGas in lung following quiet exhalation Normally 2.4L Normally 2.4L


Capacity (cont)Capacity (cont) VC - Vital CapacityVC - Vital Capacity

Made of IRV, VT, and ERVMade of IRV, VT, and ERV Maximum exhalation following a maximum Maximum exhalation following a maximum

inspirationinspiration Normally 4.8LNormally 4.8L

TLC - Total Lung CapacityTLC - Total Lung Capacity Made of IRV, VT, ERV and RVMade of IRV, VT, ERV and RV Gas in the lung following maximum inhalationGas in the lung following maximum inhalation Normally 6LNormally 6L

FRC and Lung ComplianceFRC and Lung Compliance FRC is most consistent volume - FRC is most consistent volume -

diaphragm at restdiaphragm at rest At FRC, equalization of opposing forces of At FRC, equalization of opposing forces of

pulmonary and thoracic elasticitypulmonary and thoracic elasticity As elasticity changes, FRC changesAs elasticity changes, FRC changes At FRC, intrapleural pressure is normal -5 cm At FRC, intrapleural pressure is normal -5 cm

H2OH2O At FRC, intrapulmonary pressure equals At FRC, intrapulmonary pressure equals

ambient pressureambient pressure With an increase in compliance, (decrease With an increase in compliance, (decrease

elasticity), an increase in ease of inspiration elasticity), an increase in ease of inspiration but difficulty in expirationbut difficulty in expiration

Decrease in compliance, decrease the ease of Decrease in compliance, decrease the ease of inspiration inspiration

Classification of VentilationClassification of Ventilation

VE = Minute VentilationVE = Minute Ventilation The amount of gas moved in 1 minuteThe amount of gas moved in 1 minute Calculated by VT times (*) fCalculated by VT times (*) f Can be measured by a respirometerCan be measured by a respirometer

Vane- Draeger, WrightVane- Draeger, Wright Volume bellows spirometerVolume bellows spirometer Venticomp bagVenticomp bag Vortex principle- Boum’s LS 75Vortex principle- Boum’s LS 75 Use a respirometer with a filter attached to Use a respirometer with a filter attached to

demonstrate measuring VEdemonstrate measuring VE


VD= Dead spaceVD= Dead space Part of min. ventilation is "wasted", does Part of min. ventilation is "wasted", does

not reach alveoli where external not reach alveoli where external respiration occursrespiration occurs

Anatomical (VDanat)Anatomical (VDanat) Fills space in the conductive airwaysFills space in the conductive airways

Alveolar (VDalv)Alveolar (VDalv) Alveoli that are not perfusionAlveoli that are not perfusion

Physiologic (VDphys)Physiologic (VDphys) All dead space combination of VDanat and VDalvAll dead space combination of VDanat and VDalv


Dead space (cont)Dead space (cont) MechanicalMechanical

Added dead spaceAdded dead space Normally 1 cc per pound ideal weight Normally 1 cc per pound ideal weight

(approx. 150cc)(approx. 150cc) Volume rebreathedVolume rebreathed


VA = Alveolar ventilationVA = Alveolar ventilation Gas in perfused alveoliGas in perfused alveoli Participates in external respirationParticipates in external respiration VA= (VT - VD)VA= (VT - VD)

Classification of VentilationClassification of Ventilation Terms relating to dead spaceTerms relating to dead space

Normal ventilationNormal ventilation Adequate ventilation to meet metabolic needsAdequate ventilation to meet metabolic needs

HypoventilationHypoventilation Decreased alveolar ventilationDecreased alveolar ventilation Can be caused by increased VD or decreased VTCan be caused by increased VD or decreased VT Ventilation less than that necessary to meet Ventilation less than that necessary to meet

metabolic needs; signified by a PCO2 greater metabolic needs; signified by a PCO2 greater than 45 mmHg in the arterial bloodthan 45 mmHg in the arterial blood

HyperventilationHyperventilation Increased alveolar ventilationIncreased alveolar ventilation Caused by decreased VD or increased VTCaused by decreased VD or increased VT Ventilation more than necessary to meet Ventilation more than necessary to meet

metabolic needs, signified by a PCO2 less than metabolic needs, signified by a PCO2 less than 35 mmHg in the arterial blood35 mmHg in the arterial blood

Ventilation and PerfusionVentilation and Perfusion

Ventilation = alveolar minute Ventilation = alveolar minute ventilationventilation

VA = (VT - VD)* fVA = (VT - VD)* f Perfusion = blood flow to the tissuesPerfusion = blood flow to the tissues

Ventilation and PerfusionVentilation and Perfusion External respiration = gas exchange External respiration = gas exchange

between the alveoli and capillariesbetween the alveoli and capillaries Carbon dioxide leaves bloodCarbon dioxide leaves blood Oxygen enters the bloodOxygen enters the blood Respiratory Quotient -unequal exchange of Respiratory Quotient -unequal exchange of

CO2 produced vs. oxygen uptake or utilizationCO2 produced vs. oxygen uptake or utilization

200 ml CO2 produced by 250 ml O2 used due to 200 ml CO2 produced by 250 ml O2 used due to normal metabolism in the Kreb’s cycle (CARC page normal metabolism in the Kreb’s cycle (CARC page

154 & 389).154 & 389).

8.0250

200

/5

/4

2

2

2

2 Oml

COmlor

Ovol

COvolRQ

Gas exchange unitGas exchange unit

Normal unitNormal unit Alveoli with capillary—relationship between Alveoli with capillary—relationship between

ventilation and gas flow are relatively equalventilation and gas flow are relatively equal Dead space unitDead space unit

ventilation without or in excess of perfusionventilation without or in excess of perfusion ShuntShunt

Perfusion without or in excess of ventilationPerfusion without or in excess of ventilation Silent unitSilent unit

No perfusion, no ventilationNo perfusion, no ventilation

Regional Differences in Regional Differences in Ventilation & PerfusionVentilation & Perfusion

More ventilation to the basesMore ventilation to the bases 4 times more ventilation to bases than apices4 times more ventilation to bases than apices

Due to gravity’s effect on pleural pressuresDue to gravity’s effect on pleural pressures On inspiration the transpulmonary pressure is On inspiration the transpulmonary pressure is

greater at the basesgreater at the bases More perfusion to basesMore perfusion to bases

Due to gravityDue to gravity 20 times more perfusion to bases than apices20 times more perfusion to bases than apices

Ventilation/Perfusion ratio (V/Q)Ventilation/Perfusion ratio (V/Q) V/Q = 4L alveolar minute volume 5L minute V/Q = 4L alveolar minute volume 5L minute

cardiac outputcardiac output Overall for the lung is 4:5 or 0.8Overall for the lung is 4:5 or 0.8

Regional Differences in Regional Differences in Ventilation & PerfusionVentilation & Perfusion

DiffusionDiffusion Whole Body Diffuision GradientsWhole Body Diffuision Gradients Determinants of Alveolar Gas TensionsDeterminants of Alveolar Gas Tensions Mechanism of DiffusionMechanism of Diffusion Systemic Diffusion GradientsSystemic Diffusion Gradients AbnormalitiesAbnormalities

Impaired oxygen DeliveryImpaired oxygen Delivery Impaired Carbon Dioxide RemovalImpaired Carbon Dioxide Removal

Shunting Shunting Unoxygenated blood entering the left Unoxygenated blood entering the left

side of the heartside of the heart Anatomical shuntAnatomical shunt

Normally 2-5% of cardiac outputNormally 2-5% of cardiac output Bronchial veins drains bronchial circulationBronchial veins drains bronchial circulation Pleural veins drains pleural circulationPleural veins drains pleural circulation

Thebesian veins drains heart circulationThebesian veins drains heart circulation

Absolute capillary shuntAbsolute capillary shunt Alveoli perfused but not ventilatedAlveoli perfused but not ventilated ““True Shunt”True Shunt” Refractory to O2 therapyRefractory to O2 therapy

ShuntingShunting

Relative capillary shuntRelative capillary shunt V/Q mismatchV/Q mismatch Areas where perfusion is in excess of Areas where perfusion is in excess of

ventilationventilation Physiological shuntPhysiological shunt

Sum of anatomical, absolute and relative shuntsSum of anatomical, absolute and relative shunts CausesCauses

Decrease in ventilationDecrease in ventilation An increase in perfusion (increased CO)An increase in perfusion (increased CO)

Dead SpaceDead Space "Wasted" ventilation"Wasted" ventilation TypesTypes

AnatomicalAnatomical Conducting airways in tracheobronchial treeConducting airways in tracheobronchial tree

Alveolar: Alveoli that have decreased perfusionAlveolar: Alveoli that have decreased perfusion Physiological: Sum of anatomical and alveolarPhysiological: Sum of anatomical and alveolar Mechanical – added dead spaceMechanical – added dead space CausesCauses

An increase in ventilationAn increase in ventilation A decrease in perfusion (decreased CO)A decrease in perfusion (decreased CO)

EffectEffect Increased VD will decrease VA if VE remains constantIncreased VD will decrease VA if VE remains constant

Effects of exercise & of high Effects of exercise & of high pressure environspressure environs

ExerciseExercise Increases CO2 production and O2 Increases CO2 production and O2

consumptionconsumption Aerobic versus anaerobicAerobic versus anaerobic

Oxygen consumption correlates to alveolar Oxygen consumption correlates to alveolar ventilationventilation

At rest 250ml rises to 3500ml/minute At rest 250ml rises to 3500ml/minute (untrained) to 5000ml/minute (trained (untrained) to 5000ml/minute (trained athlete)athlete)

PaO2, PaCO2 and pH remain constantPaO2, PaCO2 and pH remain constant


Exercise (cont)Exercise (cont) CirculationCirculation

Increased sympathetic impulses stimulates heart Increased sympathetic impulses stimulates heart rate and perfusion to working musclesrate and perfusion to working muscles

Frank-Starling mechanismFrank-Starling mechanism Maximal heart rateMaximal heart rate

Muscle Work, Oxygen Consumption, and Muscle Work, Oxygen Consumption, and Cardiac Output InterrelationshipsCardiac Output Interrelationships

The Training InfluenceThe Training Influence Body Temperature: Cutaneous Blood Flow Body Temperature: Cutaneous Blood Flow

RelationshipRelationship


High altitudeHigh altitude AcclimatizationAcclimatization Major cardiopulmonary responsesMajor cardiopulmonary responses

increased alveolar ventilation via peripheral increased alveolar ventilation via peripheral chemoreceptor stimulationchemoreceptor stimulation

Secondary polycythemia, increased RBC production Secondary polycythemia, increased RBC production due to low oxygen levelsdue to low oxygen levels

Development of respiratory alkalemia, due to the Development of respiratory alkalemia, due to the increased alveolar ventilation and carbon dioxide increased alveolar ventilation and carbon dioxide eliminationelimination

Increased oxygen diffusion capacity in native high Increased oxygen diffusion capacity in native high dwellers, due to increased lung sizedwellers, due to increased lung size


Major cardiopulmonary responses (cont)Major cardiopulmonary responses (cont) Increased alveolar arterial oxygen differenceIncreased alveolar arterial oxygen difference Improved ventilation perfusion ratioImproved ventilation perfusion ratio Increased cardiac output of non-acclimatized Increased cardiac output of non-acclimatized

individualsindividuals Increased pulmonary hypertension as a result of Increased pulmonary hypertension as a result of

hypoxic vasoconstrictionhypoxic vasoconstriction

SolutionsSolutions

DefinitionDefinition Concentration Concentration Osmotic pressureOsmotic pressure Quantifying solute content and activityQuantifying solute content and activity Calculating solute contentCalculating solute content Quantitative classification of solutionsQuantitative classification of solutions

Electrolytic Activity and Acid Electrolytic Activity and Acid Base BalanceBase Balance

Characteristics of acids, bases, and Characteristics of acids, bases, and saltssalts

Designation of acidity and alkalinityDesignation of acidity and alkalinity

Body Fluids and ElectrolytesBody Fluids and Electrolytes

FluidsFluids Electrolytes Electrolytes

Blood GasesBlood Gases

DefineDefine Kreb’s [TCA] CycleKreb’s [TCA] Cycle

Oxygen TransportOxygen Transport

DissolvedDissolved Henry's Law - weight of gas dissolving Henry's Law - weight of gas dissolving

in liquid is proportional to the partial in liquid is proportional to the partial pressure of a gaspressure of a gas

Bunsen solubility coefficient for O2Bunsen solubility coefficient for O2 0.023ml of O2 can be dissolved in 1ml of plasma 0.023ml of O2 can be dissolved in 1ml of plasma

at 37°C and 760mmHg PO2at 37°C and 760mmHg PO2 This allows us to determine the amount of O2 This allows us to determine the amount of O2

(expressed in ml) dissolved in 1ml of plasma (expressed in ml) dissolved in 1ml of plasma using the formula: 0.003 * PaO2using the formula: 0.003 * PaO2

(ex: PaO2 of 100 mmHg = 0.3ml of dissolved O2 (ex: PaO2 of 100 mmHg = 0.3ml of dissolved O2 in plasma)in plasma)


Graham's Law – rate of diffusion of a Graham's Law – rate of diffusion of a gas is directly proportional to its gas is directly proportional to its solubility coefficient and inversely solubility coefficient and inversely proportional to the square root of its proportional to the square root of its densitydensity

CO2 is 20 times more diffusible than O2CO2 is 20 times more diffusible than O2 CO is 200 times more diffusible than O2CO is 200 times more diffusible than O2 Hemoglobin’s affinity for CO is 200 times Hemoglobin’s affinity for CO is 200 times

more than for oxygen.more than for oxygen.


Combined with hemoglobinCombined with hemoglobin Carries the most oxygen to the tissuesCarries the most oxygen to the tissues Doesn't exert a gas pressureDoesn't exert a gas pressure Calculate 1.34 * Hb * SaO2Calculate 1.34 * Hb * SaO2 Total oxygen content is sum of Total oxygen content is sum of

dissolved and combineddissolved and combined


Oxyhemoglobin dissociation curve Oxyhemoglobin dissociation curve Curve is sigmoidal due to Hb affinity Curve is sigmoidal due to Hb affinity

for O2 at each of 4 binding sitesfor O2 at each of 4 binding sites Last site has less affinity than 2nd & 3rd Last site has less affinity than 2nd & 3rd In the steep portion minimal changes in In the steep portion minimal changes in

PO2 will cause drastic changes in PO2 will cause drastic changes in saturation and total O2 contentsaturation and total O2 content

P50 is where Hb is 50% saturated with O2 P50 is where Hb is 50% saturated with O2 and is normally a PaO2 of 27mm/Hgand is normally a PaO2 of 27mm/Hg


Oxyhemoglobin dissociation curve Oxyhemoglobin dissociation curve (cont)(cont)

A shift to right causes a decreased A shift to right causes a decreased affinity for O2, resulting in decreased affinity for O2, resulting in decreased saturation but increased O2 to tissues saturation but increased O2 to tissues

Factors causing shift to the rightFactors causing shift to the right Increased PCO2Increased PCO2 Increased H+ (decreased pH)Increased H+ (decreased pH) Increased 2, 3 DPGIncreased 2, 3 DPG Increased temperatureIncreased temperature


Oxyhemoglobin dissociation curve Oxyhemoglobin dissociation curve (cont)(cont)

A shift to the left causes increased affinity A shift to the left causes increased affinity for O2, resulting in increased saturation for O2, resulting in increased saturation but decreased O2 to the tissuesbut decreased O2 to the tissues

Factors causing shift to the leftFactors causing shift to the left Decreased PCO2Decreased PCO2 Decreased H+ (increased pH)Decreased H+ (increased pH) Decreased temperatureDecreased temperature Decreased 2, 3, DPGDecreased 2, 3, DPG

Oxygen TransportOxygen Transport Oxyhemoglobin dissociation curve Oxyhemoglobin dissociation curve

(cont)(cont) Bohr effect – the effect of H+ or CO2 on Bohr effect – the effect of H+ or CO2 on

Hb affinity for O2Hb affinity for O2 At lungs – PCO2 is lowAt lungs – PCO2 is low

Shifts curve to leftShifts curve to left Increased affinity for O2Increased affinity for O2 pH increased in lungs causing shift to the left with pH increased in lungs causing shift to the left with

an uptake of oxygen into the bloodan uptake of oxygen into the blood At tissues - PCO2 is highAt tissues - PCO2 is high

Shifts curve to the rightShifts curve to the right Decreases affinity for O2Decreases affinity for O2 pH decreased in tissue causing shift to right pH decreased in tissue causing shift to right

releasing oxygen to the tissuereleasing oxygen to the tissue

Shift to Left (increased affinity)

Shift to Right (decreased affinity)

H+ ( pH) H+ ( pH) PCO2 PCO2 Temperature Temperature

2-3 DPG 2-3 DPG P50 <27 P50 >27 ↑ SaO2 ↓ Sao2


Total O2 content is determined by Total O2 content is determined by adding the combined oxygen adding the combined oxygen content with the dissolved oxygen content with the dissolved oxygen contentcontent

CaO2 = (0.003 * PaO2) + (1.34 * Hb * CaO2 = (0.003 * PaO2) + (1.34 * Hb * SaO2)SaO2)

HypoxemiaHypoxemia

Deficiency of oxygen in the arterial Deficiency of oxygen in the arterial bloodblood

Causes of hypoxemiaCauses of hypoxemia Decreased alveolar oxygen tensionDecreased alveolar oxygen tension

Alveolar air equationAlveolar air equation

RQ

PaCOvaporOPHPBarOFPAO 2

2212 )(

HypoxemiaHypoxemia

Causes of hypoxemiaCauses of hypoxemia Alveolar hypoventilationAlveolar hypoventilation Decreased hemoglobin saturationDecreased hemoglobin saturation Alveolar hypoventilation due to V/Q Alveolar hypoventilation due to V/Q

abnormalitiesabnormalities Intrapulmonary shunting: blood going from Intrapulmonary shunting: blood going from

right to left heart without oxygenationright to left heart without oxygenation

HypoxemiaHypoxemia

Responses to hypoxemiaResponses to hypoxemia Increased ventilationIncreased ventilation Increased cardiac outputIncreased cardiac output TypesTypes

HypoxicHypoxic AnemicAnemic StagnantStagnant HistotoxicHistotoxic

HypoxiaHypoxia

Decreased oxygen to the tissuesDecreased oxygen to the tissues Hypoxemic Hypoxia or Ambient HypoxiaHypoxemic Hypoxia or Ambient Hypoxia

PaO2 decreasedPaO2 decreased Anemic Hypoxia or Hemic Hypoxia Anemic Hypoxia or Hemic Hypoxia

Hb decreasedHb decreased inability to accept O2 (CO poisoning)inability to accept O2 (CO poisoning)

Hb has 200 times more affinity for CO than O2Hb has 200 times more affinity for CO than O2 Normal HbCO is 0.5%Normal HbCO is 0.5% HbCO of 5-10% occurs after smokingHbCO of 5-10% occurs after smoking HbCO of 40-60% can cause deathHbCO of 40-60% can cause death

HypoxiaHypoxia

Stagnant Hypoxia or Circulatory HypoxiaStagnant Hypoxia or Circulatory Hypoxia Heart unable to deliver oxygenated blood to Heart unable to deliver oxygenated blood to

tissues (low CO)tissues (low CO) Histotoxic HypoxiaHistotoxic Hypoxia

cells unable to accept or use oxygen cells unable to accept or use oxygen (cyanide poisoning)(cyanide poisoning)

ResultsResults Anaerobic metabolismAnaerobic metabolism Production of lactic acids is a by product of Production of lactic acids is a by product of

CO2 metabolismCO2 metabolism

Alveolar-Arterial Oxygen Alveolar-Arterial Oxygen Difference P(A-a)O2Difference P(A-a)O2

Measurement of the pressure difference Measurement of the pressure difference between the alveoli and the arterial between the alveoli and the arterial bloodblood

In normal lungs O2 is readily transferred In normal lungs O2 is readily transferred from alveoli to blood and only a small PO2 from alveoli to blood and only a small PO2 difference is presentdifference is present

Diseased lungs often have larger P(A-a)O2 Diseased lungs often have larger P(A-a)O2 because of diffusion defectsbecause of diffusion defects

Has been used to estimate the percent Has been used to estimate the percent intrapulmonary shuntintrapulmonary shunt On 100% O2, every 50 mmHg difference in P(A-On 100% O2, every 50 mmHg difference in P(A-

a)O2 approximates a 2% shunta)O2 approximates a 2% shunt

Alveolar-Arterial Oxygen Alveolar-Arterial Oxygen Difference P(A-a)O2Difference P(A-a)O2

An increase in P(A-a)O2 is strictly An increase in P(A-a)O2 is strictly an indication of respiratory defects an indication of respiratory defects in oxygenation abilitiesin oxygenation abilities

Most respiratory dysfunctions that produce Most respiratory dysfunctions that produce hypoxemia are accompanied by an hypoxemia are accompanied by an increase in P(A-a)O2increase in P(A-a)O2

Normal value on room air is 10 to Normal value on room air is 10 to 15 mmHg15 mmHg

CO2 TransportCO2 Transport

Carbon DioxideCarbon Dioxide Produced from normal metabolismProduced from normal metabolism The burning of glucose with O2 is The burning of glucose with O2 is

carried in plasma and in red blood cellscarried in plasma and in red blood cells


In plasmaIn plasma Dissolved: approximately 8% of CO2Dissolved: approximately 8% of CO2 As Bicarbonate (HCO3): As Bicarbonate (HCO3):

CO2 + H2O form carbonic acid (H2CO3)CO2 + H2O form carbonic acid (H2CO3) dissociates into bicarbonate and hydrogen ionsdissociates into bicarbonate and hydrogen ions Equation Equation H2O + CO2 = H2CO3H2O + CO2 = H2CO3H+ + HCO3¯H+ + HCO3¯

about 80% of C02 is transported as about 80% of C02 is transported as bicarbonatebicarbonate

Attached to plasma proteins about 12%Attached to plasma proteins about 12%


In the red blood cellsIn the red blood cells DissolvedDissolved As HCO3¯As HCO3¯

HCO3¯ produced by hydrolysis of CO2HCO3¯ produced by hydrolysis of CO2 HCO3¯ diffuses out of cellHCO3¯ diffuses out of cell creates an electrical imbalancecreates an electrical imbalance Cl¯ enters the cell to bring balanceCl¯ enters the cell to bring balance called the chloride shift or Hamburger called the chloride shift or Hamburger

phenomenonphenomenon Attached to the Hb moleculeAttached to the Hb molecule


Haldane EffectHaldane Effect The effect of O2 on CO2 transportThe effect of O2 on CO2 transport

At the lungs, PO2 is increased & CO2 is At the lungs, PO2 is increased & CO2 is unloaded off Hbunloaded off Hb

At the tissues, PO2 is decreased & CO2 is At the tissues, PO2 is decreased & CO2 is loaded on Hbloaded on Hb


Terms relating to PaCO2Terms relating to PaCO2 Hypocapnia or hyporcarbiaHypocapnia or hyporcarbia

CO2 below 35 mmHgCO2 below 35 mmHg Hypercapnia or hypercarbiaHypercapnia or hypercarbia

CO2 above 45 mmHgCO2 above 45 mmHg EucapneaEucapnea

Normal CO2 (35-45 mmHg)Normal CO2 (35-45 mmHg)

Buffer Systems (Acid Base Buffer Systems (Acid Base Balance) Balance)

Purpose is to maintain the pHPurpose is to maintain the pH Prevent rapid changesPrevent rapid changes

Buffer systemsBuffer systems Open/BicarbonateOpen/Bicarbonate

Mainly the HCO3/H2CO3Mainly the HCO3/H2CO3 VentilatoryVentilatory About 60%About 60%

HbHb RenalRenal About 30%About 30%

Buffer Systems (Acid Base Buffer Systems (Acid Base Balance) Balance)

Closed/NoncarbonateClosed/Noncarbonate BloodBlood

IntracellularIntracellular Phosphates, proteins, sulfates and Phosphates, proteins, sulfates and

ammonia groupsammonia groups Physiological roles of buffer systemsPhysiological roles of buffer systems

BicarbonateBicarbonate NoncarbonateNoncarbonate

Henderson-Hasselbalch Henderson-Hasselbalch EquationEquation

pH = pk + logpH = pk + log

pk = 6.10 pk = 6.10 normally HCO3¯= 24 mEq/Lnormally HCO3¯= 24 mEq/L normally H2CO3 = 1.2 mEq/Lnormally H2CO3 = 1.2 mEq/L

log of 20 = 1.3log of 20 = 1.3 6.1 + 1.3 = 7.4 normal pH6.1 + 1.3 = 7.4 normal pH 10/1 = acidemia10/1 = acidemia 30/1 = alkalemia30/1 = alkalemia

)(

)(

32

3

COH

HCO

1

20

32

3

COH

HCO

Normal Values (Arterial)Normal Values (Arterial)

AbsoluteAbsolute RangeRange pHpH 7.47.4 7.35-7.457.35-7.45 PaCO2 PaCO2 40 mmHg40 mmHg 35-4535-45 PaO2PaO2 100 mmHg100 mmHg 80-10080-100 HCO3HCO3 24 mEq/L24 mEq/L 22-2622-26 BaseBase 00 00 + or – 2+ or – 2 HbHb 14 gm %14 gm % 12-1512-15 O2 SatO2 Sat 97.5 %97.5 % 95 - 100%95 - 100% O2 contentO2 content 20 volume %20 volume % 18-20 volume 18-20 volume

%%

Normal Values (Venous)Normal Values (Venous)

AbsoluteAbsolute pHpH 7.367.36 PvCO2PvCO2 4646 PvO2PvO2 4040 HCO3HCO3 2424 BaseBase 00 HbHb 14 14 O2 SatO2 Sat 75 75 O2 contentO2 content 15 volume %15 volume %

Acid Base EffectsAcid Base Effects

Increased CO2 causes a decreased Increased CO2 causes a decreased pHpH

Decreased CO2 causes an increased Decreased CO2 causes an increased pHpH

Increased HCO3 causes an increased Increased HCO3 causes an increased pHpH

Decreased HCO3 causes a Decreased HCO3 causes a decreased pHdecreased pH

CompensationCompensation

KidneysKidneys Excrete H+ which increase HCO3 to Excrete H+ which increase HCO3 to

compensate for an increased CO2compensate for an increased CO2 Excrete less H+ and more HCO3 to Excrete less H+ and more HCO3 to

compensate for decreased PCO2compensate for decreased PCO2 May take 3 days to compensateMay take 3 days to compensate Excess Hydrogen Ion excretion & role Excess Hydrogen Ion excretion & role

of urinary buffersof urinary buffers

CompensationCompensation

LungsLungs Increases CO2 to compensate for an Increases CO2 to compensate for an

increased HCO3 (short term only)increased HCO3 (short term only) PharmacologicallyPharmacologically

Administer sodium bicarbonate Administer sodium bicarbonate (NaHCO3) to increase pH(NaHCO3) to increase pH

Administer ammonium chloride Administer ammonium chloride (NH3Cl) to decrease pH(NH3Cl) to decrease pH

InterpretationInterpretation

Method for interpretationMethod for interpretation Categorize pHCategorize pH Determine Respiratory InvolvementDetermine Respiratory Involvement Determine Metabolic InvolvementDetermine Metabolic Involvement Assess for CompensationAssess for Compensation

InterpretationInterpretationA. Values

pH PCO2 HCO3 B.E. Respiratory Acidosis

1. Uncompensated - + N N 2. Partially Compensated - + + + 3. Compensated N + + +

Respiratory Alkalosis 4. Uncompensated + - N N 5. Partially Compensated + - - - 6. Compensated N - - -

Metabolic Acidosis 7. Uncompensated - N - - 8. Partially Compensated - - - - 9. Compensated N - - -

Metabolic Alkalosis 10. Uncompensated + N + + 11. Partially Compensated + + + + 12. Compensated N + + +


StatesStates Respiratory AcidosisRespiratory Acidosis

CausesCauses CompensationCompensation CorrectionCorrection

Respiratory AlkalosisRespiratory Alkalosis CausesCauses Clinical SignsClinical Signs CompensationCompensation CorrectionCorrection Alveolar Hyperventilation Superimposed on Alveolar Hyperventilation Superimposed on

Compensated Respiratory AcidosisCompensated Respiratory Acidosis


ValuesValuespHpH PCO2PCO2 HCO3HCO3 B.E. B.E.

Respiratory AcidosisRespiratory Acidosis Uncompensated Uncompensated -- ++ NN N N Partially CompensatedPartially Compensated -- ++ ++ ++ CompensatedCompensated NN ++ ++ ++

Respiratory AlkalosisRespiratory Alkalosis UncompensatedUncompensated ++ -- NN NN Partially CompensatedPartially Compensated ++ -- -- -- CompensatedCompensated NN -- -- --

Metabolic AcidosisMetabolic Acidosis UncompensatedUncompensated -- NN -- -- Partially CompensatedPartially Compensated -- -- -- -- CompensatedCompensated NN - - -- --

Metabolic AlkalosisMetabolic Alkalosis UncompensatedUncompensated ++ NN ++ ++ Partially CompensatedPartially Compensated ++ ++ ++ ++ CompensatedCompensated NN ++ ++ ++


Metabolic AcidosisMetabolic Acidosis CausesCauses Anion GapAnion Gap CompensationCompensation SymptomsSymptoms CorrectionCorrection

Metabolic AlkalosisMetabolic Alkalosis Causes Causes CompensationCompensation CorrectionCorrection

Metabolic Acid-Base IndicatorsMetabolic Acid-Base Indicators Standard BicarbonateStandard Bicarbonate Base ExcessBase Excess

Assessment of HypoxemiaAssessment of Hypoxemia

On room air with normal Hb and under On room air with normal Hb and under 60 years old (PaO2 above 80mmHg = 60 years old (PaO2 above 80mmHg = no hypoxemia)no hypoxemia)

Normal = 80-100mmhgNormal = 80-100mmhg Mild hypoxemia = PaO2 = 60-79mmHgMild hypoxemia = PaO2 = 60-79mmHg Moderate hypoxemia = PaO2 = 40-Moderate hypoxemia = PaO2 = 40-

59mmHg59mmHg Severe hypoxemia PaO2 = less than Severe hypoxemia PaO2 = less than

40mmHg40mmHg


O2 contentO2 content Mild hypoxemia 15-17 volume % (17)Mild hypoxemia 15-17 volume % (17) Moderate hypoxemia = 12-14 volume % (15)Moderate hypoxemia = 12-14 volume % (15) Severe hypoxemia = 12 volume % (12)Severe hypoxemia = 12 volume % (12)

Over 60 years oldOver 60 years old Subtract 1 mmHg for every year over 60Subtract 1 mmHg for every year over 60 Severe hypoxemia is still PaO2 <40mmHgSevere hypoxemia is still PaO2 <40mmHg

**Review Table 7-2 CARC p122 “Relationship between Age and Review Table 7-2 CARC p122 “Relationship between Age and Normal Predicted PaCO2Normal Predicted PaCO2


Patients with abnormal HbPatients with abnormal Hb Calculate total O2 contentCalculate total O2 content

(Hb * 1.34 * SaO2) + (0. 003 * PaO2)(Hb * 1.34 * SaO2) + (0. 003 * PaO2) Mild hypoxemia = CaO2 17 volume %Mild hypoxemia = CaO2 17 volume % Moderate hypoxemia = CaO2 15 Moderate hypoxemia = CaO2 15

volume %volume % Severe hypoxemia = CaO2 12 volume Severe hypoxemia = CaO2 12 volume

%%

Other Oxygenation Other Oxygenation AssessmentsAssessments

Oxygen Saturation (SaO2)Oxygen Saturation (SaO2) Arterial Oxygen Content (CaO2)Arterial Oxygen Content (CaO2) Alveolar-Arterial Oxygen Difference [P(A-Alveolar-Arterial Oxygen Difference [P(A-

a)O2]a)O2] Partial Pressure of Oxygen in Mixed Partial Pressure of Oxygen in Mixed

Venous Blood (PvO2)Venous Blood (PvO2) Arteriovenous Oxygen Content Difference Arteriovenous Oxygen Content Difference

C(a-v)O2C(a-v)O2 Carboxyhemoglobin (HbCO)Carboxyhemoglobin (HbCO)

Assessment of Acid Base Assessment of Acid Base BalanceBalance

Hydrogen Ion Concentration (pH)Hydrogen Ion Concentration (pH) Partial Pressure of Arterial Carbon Partial Pressure of Arterial Carbon

Dioxide (PaCO2)Dioxide (PaCO2) Arterial Blood Bicarbonate (HCO3-)Arterial Blood Bicarbonate (HCO3-) Base Excess & Base DeficitBase Excess & Base Deficit

Control of Ventilation Control of Ventilation

VentilationVentilation Under control of autonomic or involuntary Under control of autonomic or involuntary

nervous systemnervous system Is controlled by central and peripheral Is controlled by central and peripheral

chemoreceptorschemoreceptors Central chemoreceptorsCentral chemoreceptors

Influenced by contents of the cerebrospinal Influenced by contents of the cerebrospinal fluid (CSF)fluid (CSF)

CO2 diffuses freely in CSFCO2 diffuses freely in CSF Increased CO2 in CSF will cause increased H+Increased CO2 in CSF will cause increased H+ Causes a stimulation of the inspiratory centerCauses a stimulation of the inspiratory center

Control of VentilationControl of Ventilation

Central chemoreceptors (cont)Central chemoreceptors (cont) Areas of the medullary centerAreas of the medullary center

Apneustic or pontine centerApneustic or pontine center Allows deep inspirationAllows deep inspiration

Pneumontaxic centerPneumontaxic center Limits inspiration from inspiration centerLimits inspiration from inspiration center Causes decreased rate of timeCauses decreased rate of time Hering-Breuer (stretch receptors)Hering-Breuer (stretch receptors)

Inflation reflex message carried to brain via Vagus Inflation reflex message carried to brain via Vagus nervenerve

Located in smooth muscle of both large and small Located in smooth muscle of both large and small airwaysairways

Limits inspirationLimits inspiration

Peripheral ChemoreceptorsPeripheral Chemoreceptors

Carotid bodiesCarotid bodies Responds to hypoxemiaResponds to hypoxemia Increases ventilationIncreases ventilation Located in the bifurcations of the common Located in the bifurcations of the common

carotid arteriescarotid arteries Aortic bodiesAortic bodies

Responds to hypoxemiaResponds to hypoxemia Usually effects heart more than ventilationUsually effects heart more than ventilation Located in the aortic archLocated in the aortic arch

Handle Gas Cylinders With Care

States of MatterStates of Matter

EnergyEnergy PotentialPotential KineticKinetic TemperatureTemperature

Absolute ZeroAbsolute Zero ScalesScales

Heat TransferHeat Transfer


FormsForms SolidSolid Liquid (Properties)Liquid (Properties)

PressurePressure BuoyancyBuoyancy ViscosityViscosity Cohesion & AdhesionCohesion & Adhesion Surface TensionSurface Tension Capillary ActionCapillary Action

GasGas


ChangesChanges Liquid to SolidLiquid to Solid

MeltingMelting FreezingFreezing

Liquid to Gas (Vapor)Liquid to Gas (Vapor) EvaporationEvaporation Vapor PressureVapor Pressure HumidityHumidity

Water Water How its behavior is different from other compounds How its behavior is different from other compounds

when it freezes or meltswhen it freezes or melts

GasesGases

Molecules continuously movingMolecules continuously moving Avogadro’s lawAvogadro’s law

1 gram atomic weight of any 1 gram atomic weight of any substance 6.02 * 10substance 6.02 * 102323 atoms atoms

This is known as 1 mole.This is known as 1 mole. 1 mole of a gas at STPD occupies 22.4 1 mole of a gas at STPD occupies 22.4

LL

PressurePressure

PB= barometric pressurePB= barometric pressure Normal barometric pressure isNormal barometric pressure is

760mmHg 760mmHg 14.7 PSI 14.7 PSI 1034cm H2O1034cm H2O 33ft of water33ft of water

Water vapor (or humidity) exerts Water vapor (or humidity) exerts pressurepressure

Partial pressure of H2O (PH2O) at 100% RH at Partial pressure of H2O (PH2O) at 100% RH at 37 degrees C = 47mmHg37 degrees C = 47mmHg

PressurePressure

Dalton's lawDalton's law The sum total of the individual partial The sum total of the individual partial

pressures of gases in the atmosphere pressures of gases in the atmosphere are equal to the barometric (PB = PN2 are equal to the barometric (PB = PN2 + PO2 +PTrace gases)+ PO2 +PTrace gases)

The pressure of each gas will be The pressure of each gas will be exerted when separated from a exerted when separated from a mixture (PN2 = PB * %N2)mixture (PN2 = PB * %N2)

Concentrations of Atmospheric Concentrations of Atmospheric GasesGases

Oxygen 20.95%Oxygen 20.95% Nitrogen 78.08%Nitrogen 78.08% Argon 0.93%Argon 0.93% Carbon Dioxide 0.03%Carbon Dioxide 0.03% Trace Gases 0.01 %Trace Gases 0.01 %

Application of Dalton's Law To Application of Dalton's Law To The LungThe Lung

Partial pressure of a gas equals Pbar * Partial pressure of a gas equals Pbar * concentration (example: 760mmHg * 0.21 concentration (example: 760mmHg * 0.21 = 159mmHg for O2)= 159mmHg for O2)

In the lung the water vapor exerts a In the lung the water vapor exerts a pressure of 47mmHg thus it changes the pressure of 47mmHg thus it changes the pressure of the atmospheric gases in the pressure of the atmospheric gases in the alveoli (example: Pbar= 760mmHg – alveoli (example: Pbar= 760mmHg – 47mmHg = 713mmHg)47mmHg = 713mmHg)

Because of the change in the barometric Because of the change in the barometric pressure in the alveoli the partial pressure pressure in the alveoli the partial pressure of O2 also changes (example: PO2 = of O2 also changes (example: PO2 = 713mmHg * 0.21 = 149mmHg)713mmHg * 0.21 = 149mmHg)


In the lungs the CO2 is higher than in the In the lungs the CO2 is higher than in the atmosphere and affected by the atmosphere and affected by the respiratory quotient (the unequal respiratory quotient (the unequal exchange of O2 for CO2)exchange of O2 for CO2)

Example: 149mmHg – 50mmHg = Example: 149mmHg – 50mmHg = 99mmHg (99mmHg is alveolar partial 99mmHg (99mmHg is alveolar partial pressure of oxygen)pressure of oxygen)

8.0149 2PaCO


Ideal Alveolar Gas EquationIdeal Alveolar Gas Equation In addition to the effects of PH2O on partial In addition to the effects of PH2O on partial

pressure of gases in the alveoli, the carbon pressure of gases in the alveoli, the carbon dioxide diffusing from the bloodstream into dioxide diffusing from the bloodstream into the alveoli will further decrease alveolar PO2the alveoli will further decrease alveolar PO2

Since carbon dioxide is leaving the Since carbon dioxide is leaving the bloodstream, (a closed system), and entering bloodstream, (a closed system), and entering the respiratory tract, (an open system), there the respiratory tract, (an open system), there is an indirect relationship between the is an indirect relationship between the pressures of carbon dioxide and oxygenpressures of carbon dioxide and oxygen


Ideal Alveolar Gas Equation (cont)Ideal Alveolar Gas Equation (cont) Increases in PACO2 result in decreases Increases in PACO2 result in decreases

in PAO2in PAO2 This indirect relationship basically This indirect relationship basically

involves only carbon dioxide and involves only carbon dioxide and oxygen because they are the only oxygen because they are the only metabolically active gasesmetabolically active gases

Dalton's Law must be modified to Dalton's Law must be modified to account for incoming carbon dioxide account for incoming carbon dioxide when applied to alveolar when applied to alveolar


Ideal alveolar gas equationIdeal alveolar gas equation

PAO2 = FIO2 * (Pb - PH2O) - PCO2 / RQPAO2 = FIO2 * (Pb - PH2O) - PCO2 / RQ PAO2 = pressure of O2 in the alveoliPAO2 = pressure of O2 in the alveoli Pb = barometric pressurePb = barometric pressure PH2O = water pressurePH2O = water pressure FIO2 = fraction of inspired oxygenFIO2 = fraction of inspired oxygen PACO2 = pressure of CO2 in the alveoliPACO2 = pressure of CO2 in the alveoli RQ = respiratory quotientRQ = respiratory quotient


A modification of the above equation A modification of the above equation maybe used with reasonably accurate maybe used with reasonably accurate resultsresults

PAO2 = (PB - PH2O)(FIO2) - PACO2PAO2 = (PB - PH2O)(FIO2) - PACO2 In both equations, PaCO2 is always In both equations, PaCO2 is always

considered equal to PACO2 because of considered equal to PACO2 because of the rapid equilibration of carbon the rapid equilibration of carbon dioxide (20 * faster or easier than O2)dioxide (20 * faster or easier than O2)

Gas LawsGas Laws

Ideal Gas LawIdeal Gas Law If mass is constant thenIf mass is constant then

2

22

1

11

T

VP

T

VP

Gas LawsGas Laws

Boyle's LawBoyle's Law If temperature and mass are constant If temperature and mass are constant

then volume and pressure are then volume and pressure are inversely proportionalinversely proportional

P1V1 = P2V2

Gas LawsGas Laws

Charles' LawCharles' Law If pressure and mass are constant then If pressure and mass are constant then

temperature and volume are directly temperature and volume are directly proportionalproportional

2

2

1

1

T

V

T

V

Gas LawsGas Laws

Gay-Lussac's LawGay-Lussac's Law If volume and mass remain constant, If volume and mass remain constant,

pressure and temperature are directly pressure and temperature are directly proportionalproportional

The triangle demonstrates the The triangle demonstrates the relationshiprelationship

2

2

1

1

T

P

T

P

Gas LawsGas Laws

All gas laws use temperature in All gas laws use temperature in Kelvin (absolute temperature scale)Kelvin (absolute temperature scale)

C + 273 = KelvinC + 273 = Kelvin

Relationships of Gas LawsRelationships of Gas Laws

Volume

Boyle’s Charles’m(constant)

Pressure TemperatureGay-Lussac’s

ExamplesExamples Ideal Gas EquationIdeal Gas Equation

A gas system has volume, moles, and temperature of A gas system has volume, moles, and temperature of 9160ml, 0.523 moles & 324K, respectively. What is the 9160ml, 0.523 moles & 324K, respectively. What is the pressure in torr?pressure in torr?P = xP = xV = 9160ml = 9.16LV = 9160ml = 9.16Ln = 0.523 molesn = 0.523 molesT = 324KT = 324K

(0.523 * 62.4 * 324) ÷ 9.16 = 1160 torr(0.523 * 62.4 * 324) ÷ 9.16 = 1160 torr How many moles of gas are contained in 890 ml at How many moles of gas are contained in 890 ml at

21°C and 750 mmHg pressure?21°C and 750 mmHg pressure?n = PV/RTn = PV/RT(750 mmHg ÷ 760mmHg atm-1)(0.89L) ÷ (0.08206L at (750 mmHg ÷ 760mmHg atm-1)(0.89L) ÷ (0.08206L at mol-1K-1)(294K)mol-1K-1)(294K)(0.9868) * (0.89) ÷ (24.12564)(0.9868) * (0.89) ÷ (24.12564)0.878252 ÷ 24.125640.878252 ÷ 24.12564n = 0.0364n = 0.0364

*Division of 750 by 760 is to convert mmHg to atm*Division of 750 by 760 is to convert mmHg to atm

ExamplesExamples

Boyle’s LawBoyle’s Law A gas system has initial pressure and volume A gas system has initial pressure and volume

of 3.69 atm and 5440ml. If the pressure of 3.69 atm and 5440ml. If the pressure changes to 2.38 atm, what will the resultant changes to 2.38 atm, what will the resultant volume be in ml?volume be in ml?

P1(V1) = P2 (V2)P1(V1) = P2 (V2)

3.69 * 5440 = 2.38x3.69 * 5440 = 2.38x

20073.6 = 2.38x20073.6 = 2.38x

x = 8434.29x = 8434.29

ExamplesExamples

Boyle’s Law (cont)Boyle’s Law (cont) A gas occupies 12.3L at a pressure of 40.0 A gas occupies 12.3L at a pressure of 40.0

mmHg. What is the volume when the mmHg. What is the volume when the pressure is increased to 60mmHg?pressure is increased to 60mmHg?40 * 12.3 = 60x40 * 12.3 = 60xx = 8.2Lx = 8.2L

If a gas at 25°C occupies 3.6L at a pressure If a gas at 25°C occupies 3.6L at a pressure of 1atm, what will be its volume at a pressure of 1atm, what will be its volume at a pressure of 2.5atm?of 2.5atm?1atm * 3.6L = 2.5x1atm * 3.6L = 2.5xx = 1.44Lx = 1.44L

ExamplesExamples

Charles’ LawCharles’ Law A gas system has an initial temperature A gas system has an initial temperature

of 308.9K with the volume unknown. of 308.9K with the volume unknown. When the temperature changes to -When the temperature changes to -230.4°C the volume is found to be 230.4°C the volume is found to be 1.67L. What was the initial volume in L?1.67L. What was the initial volume in L?

-230.4°C =>42.6K-230.4°C =>42.6K

11.12

863.5156.426.42

67.1

9.308

x

x

x

ExamplesExamples

Charles’ Law (cont)Charles’ Law (cont) Calculate the decrease in temperature Calculate the decrease in temperature

when 2L at 20°C is compressed to 1L.when 2L at 20°C is compressed to 1L.2L * 293 = 1x2L * 293 = 1xx = 146.5x = 146.5

A 600ml sample of nitrogen is warmed A 600ml sample of nitrogen is warmed from 77°C to 86°C. Find its new volume from 77°C to 86°C. Find its new volume if the pressure remains constant.if the pressure remains constant.600ml ÷ 350 = 359K 600ml ÷ 350 = 359K

ExamplesExamples

Guy-Lussac’s LawGuy-Lussac’s Law A container is initially at 47mmHg and 77K A container is initially at 47mmHg and 77K

(liquid nitrogen temperature). What will the (liquid nitrogen temperature). What will the pressure be when the container warms up to pressure be when the container warms up to room temperature of 25°C?room temperature of 25°C?Ans: 180mmHgAns: 180mmHg

A gas thermometer measures temperature by A gas thermometer measures temperature by measuring the pressure of a gas inside the measuring the pressure of a gas inside the fixed volume container. A thermometer reads a fixed volume container. A thermometer reads a pressure of 248 torr at 0°C. What is the pressure of 248 torr at 0°C. What is the temperature when the thermometer reads a temperature when the thermometer reads a pressure of 345 torr?pressure of 345 torr?Ans: 107Ans: 107°C°C

ExamplesExamples

Guy-Lussac’s Law (cont)Guy-Lussac’s Law (cont) A vessel has a pressure of 18.9 lb/in2 A vessel has a pressure of 18.9 lb/in2

at 20°C. What temperature is at 20°C. What temperature is necessary to lower the pressure to necessary to lower the pressure to 14.2 lb/in2?14.2 lb/in2?

Ans: -53°CAns: -53°C

Review Characteristics of Review Characteristics of Medical Gases Medical Gases

OxygenOxygen AirAir Carbon DioxideCarbon Dioxide HeliumHelium Nitrous OxideNitrous Oxide Nitric OxideNitric Oxide

Agencies Regulating Gas Agencies Regulating Gas AdministrationAdministration

DOT - Department of TransportationDOT - Department of Transportation Before 1970, was called ICC – Interstate CommissionBefore 1970, was called ICC – Interstate Commission Regulates construction, transport and testing of Regulates construction, transport and testing of

cylinderscylinders HHS - Department. of Health & Human ServicesHHS - Department. of Health & Human Services

Formerly called HEW - Department. of Health, Formerly called HEW - Department. of Health, Education and WelfareEducation and Welfare

FDA - Food & Drug Administration - is part of HHS - FDA - Food & Drug Administration - is part of HHS - regulates the purity of gases regulates the purity of gases

OSHA Occupational Safety & Health OSHA Occupational Safety & Health Administration - responsible for occupational Administration - responsible for occupational safetysafety

Recommending BodiesRecommending Bodies

CGA - Compressed Gas Association - created CGA - Compressed Gas Association - created safety systemssafety systems

NFPA - National Fire Protection Assn.NFPA - National Fire Protection Assn. Fire preventionFire prevention Governs storageGoverns storage

Z-79 – Committee of American National Z-79 – Committee of American National Standards for Anesthetic Equipment, which Standards for Anesthetic Equipment, which includesincludes

Ventilator devicesVentilator devices Reservoir bagsReservoir bags Trachea tubes and their connectorsTrachea tubes and their connectors HumidifiersHumidifiers Other related equipmentOther related equipment

Safety Systems for Safety Systems for CylindersCylinders

Color coding for E cylinders (not Color coding for E cylinders (not mandatory for larger cylinders)mandatory for larger cylinders)

Oxygen – green (white internationally)Oxygen – green (white internationally) Carbon dioxide – greyCarbon dioxide – grey Nitrous oxide – blueNitrous oxide – blue Cyclopropane – orangeCyclopropane – orange Helium – brownHelium – brown Ethylene – redEthylene – red Air – yellowAir – yellow Nitrogen – blackNitrogen – black


Pin Index Safety SystemPin Index Safety System E cylinders and smallerE cylinders and smaller High pressure (greater than 200psi)High pressure (greater than 200psi) Yoke & pin connectionsYoke & pin connections Oxygen 2-5 positionOxygen 2-5 position Air 1-5 positionAir 1-5 position CO2 1-6 positionCO2 1-6 position


American Standard Safety SystemAmerican Standard Safety System Larger than E cylindersLarger than E cylinders High pressureHigh pressure Nipple & threaded nutNipple & threaded nut


Diameter Index Safety SystemDiameter Index Safety System Low pressures (less than 200 PSI)Low pressures (less than 200 PSI) All connections after the regulatorAll connections after the regulator Threaded nut & nippleThreaded nut & nipple

Qualities of cylinder gasesQualities of cylinder gases

Flammable Gases Flammable Gases EthyleneEthylene CyclopropaneCyclopropane

Nonflammable GasesNonflammable Gases NitrogenNitrogen Carbon dioxideCarbon dioxide HeliumHelium

Qualities of cylinder gasesQualities of cylinder gases

Gases that support combustionGases that support combustion OxygenOxygen Oxygen mixturesOxygen mixtures

Helium/oxygen – helioxHelium/oxygen – heliox Oxygen/carbon dioxide – carbogenOxygen/carbon dioxide – carbogen Oxygen/nitrogenOxygen/nitrogen Oxygen/nitrous oxideOxygen/nitrous oxide

Nitrous oxideNitrous oxide

Qualities of oxygenQualities of oxygen

ColorlessColorless OdorlessOdorless TastelessTasteless Atomic weight = 16gmsAtomic weight = 16gms Molecular weight = 32gmsMolecular weight = 32gms Critical temperatureCritical temperature -118.8ºC or -181.1ºF at 49.7 atm-118.8ºC or -181.1ºF at 49.7 atm Above this temperature it cannot remain a Above this temperature it cannot remain a

liquidliquid Fractional distillationFractional distillation

Cylinder marking and Cylinder marking and testingtesting

FrontFront DOT-3AA 2015 PSI– these are DOT DOT-3AA 2015 PSI– these are DOT

specifications and service pressurespecifications and service pressure Serial numberSerial number Ownership markingsOwnership markings Manufacturers markManufacturers mark

Cylinder marking and Cylinder marking and testingtesting

BackBack Original hydrostatic testingOriginal hydrostatic testing SpecificationsSpecifications Retest datesRetest dates Inspectors mark and specificationsInspectors mark and specifications

Cylinders are filled to 5/3 maximum Cylinders are filled to 5/3 maximum pressure every 5-10 years pressure every 5-10 years (hydrostatic testing)(hydrostatic testing)

Cylinder Filling and DurationCylinder Filling and Duration

Can be overfilled by 10% to hold Can be overfilled by 10% to hold 2200 PSI2200 PSI

Duration of flow in minutes =Duration of flow in minutes =

flowliter

factorTankpressureTank

Cylinder Filling and DurationCylinder Filling and Duration

Tank factors for O2 duration of flowTank factors for O2 duration of flow E = 0.28E = 0.28 G = 2.41G = 2.41 H = 3.14H = 3.14

These factors are used to calculate absolute These factors are used to calculate absolute duration times; however, in practice a safety factor duration times; however, in practice a safety factor must be utilized to insure no interruptions in gas must be utilized to insure no interruptions in gas therapy to the patienttherapy to the patient

Cylinder capacitiesCylinder capacities E = 22 ft3 or 616 liters @ 2200 psig E = 22 ft3 or 616 liters @ 2200 psig G = 187 ft3 or 5308 liters @ 2200 psig G = 187 ft3 or 5308 liters @ 2200 psig H = 244 ft3 or 6908 liters @ 2200 psigH = 244 ft3 or 6908 liters @ 2200 psig

Cylinder HandlingCylinder Handling

Keep in carrier or standKeep in carrier or stand No flames/smokingNo flames/smoking Proper technique in attaching regulatorsProper technique in attaching regulators

Remove capRemove cap Turn on gas momentarily (away from people) Turn on gas momentarily (away from people)

“cracking”“cracking” Place and tighten regulatorPlace and tighten regulator Turn on gasTurn on gas Adjust flowAdjust flow Bleed off pressure when not in useBleed off pressure when not in use

Cylinder HandlingCylinder Handling

Store with cap on to prevent Store with cap on to prevent breaking stembreaking stem

Cylinder testingCylinder testing Every 5- 10 yearsEvery 5- 10 years Water displacement measured to Water displacement measured to

check for expansion with 5/3 maximum check for expansion with 5/3 maximum pressurepressure

Gaseous bulk systems three Gaseous bulk systems three general typesgeneral types

StandardStandard Large H or K size cylinders banked into a Large H or K size cylinders banked into a

manifold systemmanifold system Primary bankPrimary bank Reserve bank (automatically switches to this Reserve bank (automatically switches to this

when primary system drops to a preset lower when primary system drops to a preset lower pressure limitpressure limit

Six or more cylinders manifolded together. Six or more cylinders manifolded together. Alarms are activated when reserve switches Alarms are activated when reserve switches on or malfunction occur. Cylinders are on or malfunction occur. Cylinders are replaced as needed.replaced as needed.


Fixed cylindersFixed cylinders Large bank of permanently fixed cylinders Large bank of permanently fixed cylinders

(up to 75)(up to 75) Refilled on site by a liquid O2 truck that Refilled on site by a liquid O2 truck that

converts the liquid into gas to fill tanksconverts the liquid into gas to fill tanks Trailer units (2200 PSI)Trailer units (2200 PSI)

Very large cylinders mounted on trailers Very large cylinders mounted on trailers towed to a central location for connectiontowed to a central location for connection

When low or in need of maintenance replaced When low or in need of maintenance replaced with fresh trailerwith fresh trailer


Liquid Oxygen SystemsLiquid Oxygen Systems Liquid O2 is stored at -183°C or -297°F in thermos Liquid O2 is stored at -183°C or -297°F in thermos

bottle type storage vessels (inner and outer steel bottle type storage vessels (inner and outer steel shells separated by a vacuum)shells separated by a vacuum)

Pressure readings do not indicate remainder of O2 Pressure readings do not indicate remainder of O2 because the liquid O2 doesn't exert gas pressurebecause the liquid O2 doesn't exert gas pressure

Weight will indicate remainder of O2Weight will indicate remainder of O2 Pressures not to exceed 250 PSI in containers in LOX Pressures not to exceed 250 PSI in containers in LOX

containerscontainers Specifications for bulk systems by NFPASpecifications for bulk systems by NFPA Piping systemsPiping systems

Locate zone valves in hospitalLocate zone valves in hospital Do not turn off unless directed by fire chiefDo not turn off unless directed by fire chief


Liquid Oxygen Systems (cont)Liquid Oxygen Systems (cont) Most economicalMost economical

1 ft3 of liquid O2 = 860 ft3 of gaseous O2 @ 1 ft3 of liquid O2 = 860 ft3 of gaseous O2 @ ambient temperatureambient temperature

Liquid O2 cylinders are used when usage too large Liquid O2 cylinders are used when usage too large for and not large enough for a permanently liquid for and not large enough for a permanently liquid vessel (come in various sizes see textbook)vessel (come in various sizes see textbook)

Fixed station (stand tanks) are large spherical with Fixed station (stand tanks) are large spherical with gaseous equivalents up to 130,000 cubic feet. gaseous equivalents up to 130,000 cubic feet. Refilled by service tank trucks.Refilled by service tank trucks.

All liquid O2 tank containers are equipped with 50 All liquid O2 tank containers are equipped with 50 PSI reducing valves.PSI reducing valves.

Liquid O2 duration (in minutes)Liquid O2 duration (in minutes)Pounds of liquid O2 * 344 =Pounds of liquid O2 * 344 =Liters per minuteLiters per minute


Safety precautions for bulk O2Safety precautions for bulk O2 Must have 24 hour reserve or back-up supplyMust have 24 hour reserve or back-up supply Procedure for total system failure should be knownProcedure for total system failure should be known

Oxygen ConcentratorsOxygen Concentrators MembraneMembrane

Thin membrane-1 µm thickThin membrane-1 µm thick Oxygen and H2O pass through membrane faster than Oxygen and H2O pass through membrane faster than

nitrogennitrogen Delivers an FIO2 of about 40%Delivers an FIO2 of about 40%

Molecular SieveMolecular Sieve Uses a sieve filled with sodium-aluminum silicateUses a sieve filled with sodium-aluminum silicate Air is forced through the sieveAir is forced through the sieve The nitrogen is scrubbed from the airThe nitrogen is scrubbed from the air Delivers an FIO2 of about 90% at 2 LPMDelivers an FIO2 of about 90% at 2 LPM At higher flows the FIO2 decreasesAt higher flows the FIO2 decreases

RegulatorsRegulators

Reduce high tank pressure to low Reduce high tank pressure to low working pressureworking pressure

Usually 50 PSIUsually 50 PSI Single stage regulatorSingle stage regulator

Reduces tank pressure to 50 PSI in 1 Reduces tank pressure to 50 PSI in 1 stepstep

Has one pressure relief valve (about Has one pressure relief valve (about 200 PSI)200 PSI)


Multi-stage regulatorMulti-stage regulator Reduces tank pressure to working pressure in Reduces tank pressure to working pressure in

2 or more steps2 or more steps Each stage has a pressure relief valveEach stage has a pressure relief valve The more stages the less fluctuation of The more stages the less fluctuation of

working pressureworking pressure Preset regulatorPreset regulator

Single or multi-stage regulator that is set to Single or multi-stage regulator that is set to have pressure reduced to set working have pressure reduced to set working pressure (usually 50 PSI)pressure (usually 50 PSI)

Has no way to adjust working pressureHas no way to adjust working pressure


Adjustable regulatorAdjustable regulator Single or multi-stage regulator in which Single or multi-stage regulator in which

working pressure may be set variablyworking pressure may be set variably

FlowmetersFlowmeters

Control and indicate flowControl and indicate flow Thorpe TubeThorpe Tube

Vertical funnel shape tube with floatVertical funnel shape tube with float Must be kept vertical to be accurateMust be kept vertical to be accurate


Compensated Thorpe Tube FlowmeterCompensated Thorpe Tube Flowmeter Needle valve adjustment is distal (after Needle valve adjustment is distal (after

or downstream) to the floator downstream) to the float Indicated flow is accurate in the presence Indicated flow is accurate in the presence

of back pressure to check for of back pressure to check for compensation:compensation:

Label calibrated at 70ºF, 50 PSILabel calibrated at 70ºF, 50 PSI Visualize needle valve placementVisualize needle valve placement Turn unit off and plug into pressureTurn unit off and plug into pressure Float will rise, then fallFloat will rise, then fall


Uncompensated Thorpe Tube Uncompensated Thorpe Tube FlowmeterFlowmeter

Needle is proximal (upstream or Needle is proximal (upstream or before) the floatbefore) the float

Flow meter reading will be lower than Flow meter reading will be lower than what is delivered to the patient if back what is delivered to the patient if back pressure is presentpressure is present


Kinetic FlowmeterKinetic Flowmeter Has plunger instead of floatHas plunger instead of float All other areas of Thorpe tubes applyAll other areas of Thorpe tubes apply


Bourdon GaugeBourdon Gauge Measures pressure but reads flowMeasures pressure but reads flow Flow delivered to patient is less than Flow delivered to patient is less than

flow shown on the gauge if back flow shown on the gauge if back pressure is present pressure is present

Works in any positionWorks in any position


Use of oxygen flowmeters with Use of oxygen flowmeters with heliumhelium

Due to density of gases flow will not be Due to density of gases flow will not be accurateaccurate

80% helium, 20% O2 flow will be 1.8 80% helium, 20% O2 flow will be 1.8 times the meter readingtimes the meter reading

70% helium, 30% O2 flow will be 1.6 70% helium, 30% O2 flow will be 1.6 times the meter readingtimes the meter reading

CompressorsCompressors

PistonPiston DiaphragmDiaphragm CentrifugalCentrifugal Assembly & Troubleshooting (White Assembly & Troubleshooting (White

p15)p15)

ValvesValves

Direct ActingDirect Acting DiaphragmDiaphragm Safety FeaturesSafety Features ReducingReducing

Single stageSingle stage Modified Single stageModified Single stage MultistageMultistage Safety FeaturesSafety Features


ConservationConservation

List current manufacturer and List current manufacturer and modelmodel

Describe how each acts as a Describe how each acts as a conservation optionconservation option

BlendersBlenders

See textbookSee textbook

applied physiology & chemistry

Documents

lungtotal compliance

thoraxpulmonary compliance

gas exchange

lcm h2ototal compliance

lcm h2othoracic compliance

larger alveoli

alveoli surfactant

alveolar gas air