breathing and exercise
DESCRIPTION
Breathing and Exercise. Respiration Requires the Interaction of Physiological Systems. Ventilation (1). Gas Exchange (2). Gas Transport (3). Gas Exchange (4). Cell Respiration (5). Conducting Zone: Structure-Function. Nasal Cavity is rich in blood supply which warms inspired air. - PowerPoint PPT PresentationTRANSCRIPT
Breathing and Exercise
Ventilation (1)
Gas Exchange (2)
Gas Transport (3)
Gas Exchange (4)
Cell Respiration (5)
Respiration Requires the Interaction of Physiological Systems
Respiration Requires the Interaction of Physiological Systems
Conducting Zone: Structure-FunctionConducting Zone: Structure-Function
• Nasal Cavity is rich in blood supply which warms inspired air.
• Moist lining humidifies.• Upper airways are mainly cartilaginous plates
that are ‘stiff’ and conduct air efficiently.• Lower airways contain more smooth muscle
which can regulate airflow by relaxing and expanding.
• Mucociliary ‘elevator’ filters.
Respiratory Zone - Structure-FunctionRespiratory Zone - Structure-Function
• Type 1 epithelial cells are thin (0.1 to 0.5 µm) making gas exchange with blood efficient.
• Type 2 epithelial cells make surfactant which keep alveoli ‘open’.
• Alveolar macrophages remove bacteria and other contaminants.
• Highly branched allows for great surface area for gas exchange.
(Patm - Palv)
Airway ResistanceFlow =
End-Expiration
(Patm - Palv)
Airway ResistanceFlow =
Inspiration
(Patm - Palv)
Airway ResistanceFlow =
Expiration
InspirationInspiration
Inspiratory Muscle Action
Expiration
Expiration
Vol
ume
(lit
ers)
0
2
4
6
Time
Lung Volumes and Capacities in Healthy Subjects
Males Females
Measures (20-30 yrs) (20-30 yrs)
VC 4800 3200
RV 1200 1000
FRC 2400 1800
TLC 6000 4200
RV/TLC x 100 20% 24%
Measurements are in ml except where indicated.
Lung Volumes and Capacities in Healthy Subjects
Males Females Males
Measures (20-30 yrs) (20-30 yrs) (50 to 60 yrs)
VC 4800 3200 3600
RV 1200 1000 2400
FRC 2400 1800 3400
TLC 6000 4200 6000
RV/TLC x 100 20% 24% 40%
Measurements are in ml except where indicated.
Dead Space
• Anatomical Dead Space (ADS) is the volume of air needed to fill the conducting zone.
• Physiological Dead Space (PDS) is ADS + nonfunctional alveoli.
• Healthy people: ADS = PDS• Some pulmonary diseases: ADS < PDS
Ventilation of Dead Space and Alveoli
VT is volume required to fill dead space (VD) + alveoli (VA).
In healthy subjects:
VT = ~500 ml
VD = ~150 ml
VA = ~350 ml
Ventilatory Adjustments and Respiratory Efficiency
• Increase tidal volume– alveolar ventilation increases– dead space ventilation is unchanged
• Increase respiratory frequency– alveolar ventilation increases– dead space ventilation increases
• Increasing tidal volume more efficient!!!
What Determines the Work of
Breathing?
• Lung and Chest Wall Compliance
• Tissue and Airway Resistance
Elastic Properties of the Lung are a Determinant of Compliance
Elastic Properties of the Lung are a Determinant of Compliance
Lung Volume
Transpulmonary Pressure
Compliance = y/x
Lung Volume is a Determinant of ComplianceLung Volume is a Determinant of Compliance
Lung Volume(% Total Lung Capacity)
Transpulmonary Pressure (cm H2O)
Total Lung Capacity (elastic elements
are stretched)
Functional Residual Capacity
Residual Volume(airways are compressed)
Resistance
• Tissue resistance (~20% of total resistance)
• Airway resistance (~80% of total resistance)
– Airway dimensions
– Smooth muscle contraction
– Intrapleural pressure
Regulation of Airway Smooth Muscle
Airways constricted by:Parasympathetic
stimulationAcetylcholineHistamineLeukotrienesThromboxane A2Serotonin-adrenergic agonists
Decreased PCO2
Airways dilated by:Sympathetic stimulation
(2 receptors)
Circulating 2 agonists
Nitric oxide
Increased PCO2 in small airways
Decreased PO2 in small airways
Lung Volume is Invesrsely related to Airway Resistance
Lung Volume
AirwayResistance
High Intrapleural PressuresCompress Airways
Low Intrapleural PressuresDistend Airways
Airway Compression and Intrapleural Pressure
Ventilation (1)
Gas Exchange (2)
Gas Transport (3)
Gas Exchange (4)
Cell Respiration (5)
Respiration Requires the Interaction of Physiological Systems
Respiration Requires the Interaction of Physiological Systems
Regulation of Pulmonary Vascular Blood Flow
• Pulmonary artery pressure• Extravascular events• Chemical regulation of pulmonary vascular
smooth muscle• Gravity
Pulmonary Vascular Resistance
Mean Pulmonary Artery Pressure (mmHg)
Increased Pressure decreases Vascular Resistance in the Pulmonary Circulation
Recruitment Distension
Ventilation-Perfusion Matching
• Regional Ventilation– Increased by high
CO2
• Regional Circulation– Decreased by low O2
Ensures regions of the lung that are well ventilated are also well perfused
Ventilation (1)
Gas Exchange (2)
Gas Transport (3)
Gas Exchange (4)
Cell Respiration (5)
Respiration Requires the Interaction of Physiological Systems
Diffusion of Gases
O2
CO2
T
P1
P2
A
( )VA DT
P Pgas 1 2
Surface Area for Pulmonary Gas Exchange is Influenced by:
• Body position• Body size
• Exercise• Some pulmonary diseases
Atmospheric
Air
(mmHg)
Humidified
Air
(mmHg)
Alveolar
Air
(mmHg)
Expired
Air
(mmHg)
N2 597.0 (78.6%) 563.4 (74.1%) 569.0 (74.9%) 566.0 (74.5%)
O2 159.0 (20.8%) 149.3 (19.7%) 104.0 (13.6%) 120.0 (15.7%)
CO2 0.3 (0.04%) 0.3 (0.04%) 40.0 (5.3%) 27.0 (3.6%)
H2O 3.7 (0.5%) 47.0 (6.2%) 47.0 (6.2%) 47.0 (6.2%)
Total 760 (100.0%) 760 (100.0%) 760 (100.0%) 760 (100.0%)
Partial Pressures of Respiratory Gases as they Enterand Leave the Lungs at Sea Level
Partial Pressures of Respiratory Gases as they Enterand Leave the Lungs at Sea Level
Gas Pressure Gradients in the LungGas Pressure Gradients in the Lung
Values are PO2 and PCO2 in mmHg
PulmonaryCapillary
AlveoliEnvironment
TissueMetabolism
Air-Blood Barrier
Artery
Vein
O2
CO2
0.03159
40104
40104
45 40
Gas Pressure Gradients in the Lung:Light to Moderate Exercise
Gas Pressure Gradients in the Lung:Light to Moderate Exercise
Values are PO2 and PCO2 in mmHg
PulmonaryCapillary
AlveoliEnvironment
TissueMetabolism
Air-Blood Barrier
Artery
Vein
O2
CO2
0.03159
40104
40104
6025
5 O2 molecules are dissolved in solution on both sides of the semi-permeable membrane (no net movement).
DissolvedO2 = 5
DissolvedO2 = 5
Hemoglobin as an O2 Carrier
Hemoglobin now binds 4 O2 molecules, leaving only one in solution. There is now a 5:1 dissolved O2 ratio (O2 now moves from left to right).
Hb
DissolvedO2 = 5
DissolvedO2 = 1
Hemoglobin as an O2 Carrier
5 O2 molecules are dissolved in solution on both sides of the semi-permeable membrane (no net movement).
DissolvedO2 = 5
DissolvedO2 = 5
Hemoglobin as an O2 Carrier
RBC transit in pulmonary capillary at rest is 1.0 sec
RBC transit in pulmonary capillary during exercise is as little as 0.5 sec
RBC transit in pulmonary capillary at rest is 1.0 sec
RBC transit in pulmonary capillary during exercise is as little as 0.5 sec
Diffusion - Limited Transfer in the Lung
Presence of an end capillary to alveolus partial pressure difference
Perfusion-Limited Transfer in the Lung
• Absence of an end capillary partial pressure difference
• An increase in blood flow increases gas exchange with air by sending more blood through pulmonary capillaries.
Diffusion of O2 to TissuesDiffusion of O2 to Tissues
Diffusion-Limited
Diffusion of CO2 from TissuesDiffusion of CO2 from Tissues
Perfusion-Limited
Transport of O2 in the Blood
O2 Carrying Capacity of Blood
Capacity of Blood to Transport O2 is determined byCharacteristics of the Hb-O2 Dissociation Cure
Capacity of Blood to Transport O2 is determined byCharacteristics of the Hb-O2 Dissociation Cure
‘S’ Shape of Hb-O2 Dissociation Curve‘S’ Shape of Hb-O2 Dissociation Curve
• Caused by interaction of 4 Hb subunits as they bind O2.
• Hb subunits associate with O2 sequentially with each successive binding facilitating the next.
• Flat upper portion insures consistent and adequate O2 delivery over a broad range of alveolar and arterial PO2.
• Steep portion permits rapid unloading of O2 from Hb during times of need, when PO2 is low.
Hb-O2 Binding Affinity is Influenced by Many Factors
Hb-O2 Binding Affinity is Influenced by Many Factors
Venous Blood has a Decreased O2 Carrying Capacity
Venous Blood has a Decreased O2 Carrying Capacity
Bohr EffectBohr Effect
Tissues:
High CO2 or reduced pH decrease Hb affinity for O2 and facilitates O2 unloading from blood.
Lungs:
Reduced CO2 or increased pH increase Hb affinity for O2 and facilitate O2 uptake by the blood.
Transport of CO2 in the Blood
Blood CO2 Transport
• CO2 ~ 7%
• HbCO2 ~ 23%
• HCO3- ~ 70%
Haldane Effect describes the Reduced Capacityof Arterial Blood to Transport CO2
Haldane Effect describes the Reduced Capacityof Arterial Blood to Transport CO2
Blood CO2
(ml/dl)
Blood PCO2 (mmHg)
Haldane Effect
Tissues:Deoxygenated Hb affinity for CO2 is higher than Hb-O2
affinity for CO2. This results in an increased capacity of blood to carry CO2.
Lungs:Hb-O2 has decreased affinity for CO2 and is more acidic than deoxygenated Hb. This facilitates CO2 removal from the pulmonary capillaries.
Control of Breathing Requires Three Elements:One that Senses the 'Internal Climate',One that Integrates Sensory Info and Central Commands,One that Carries Out the Order
Central Controller
pons, medulla,other parts of brain
Sensors EffectorsNegative Feedback
chemical, mechanical,and other receptors
inspiratory andexpiratory muscles
Input Output
Medullary Respiratory Centers
Figure 22.25
Depth and Rate of Breathing: PCO2
Peripheral and Central Chemoreceptors have different Response Characteristics
Breathing is stimulated by:
• Peripheral - PCO2, pH, PO2
• Central - pH, PCO2 (indirect)
Central response to arterial PCO2 is of greater magnitude.
Peripheral response to arterial PCO2 is faster.
Ventilation(liters/min)
Time (sec)
Sole Source of Ventilatory Drive to Hypoxia Comes from Peripheral Chemoreceptors
Sole Source of Ventilatory Drive to Hypoxia Comes from Peripheral Chemoreceptors
Hypoxia
Peripheral Chemoreceptorafferent nerves intactor denervated
• Respiratory adjustments are geared to both the intensity and duration of exercise
• During vigorous exercise:
– Ventilation can increase 20 fold
– Breathing becomes deeper and more vigorous, but respiratory rate may not be significantly changed (hyperpnea)
• Exercise-enhanced breathing is not prompted by an increase in PCO2 or a decrease in PO2 or pH
– These levels remain surprisingly constant during exercise
Respiratory Adjustments: Exercise
• As exercise begins:– Ventilation increases abruptly, rises slowly, and
reaches a steady state• When exercise stops:
– Ventilation declines suddenly, then gradually decreases to normal
Respiratory Adjustments: Exercise
Pulmonary Response to Constant Load Exercise
Exercise-Induced Lactic Acidosis
H20 + C02 H2C03 H+ + HC03
-
CA
Incremental Exercise Test
• Acclimatization – respiratory and hematopoietic adjustments to altitude include:– Increased ventilation – 2-3 L/min higher than at
sea level– Chemoreceptors become more responsive to
PCO2
– Substantial decline in PO2 stimulates peripheral chemoreceptors
Respiratory Adjustments: High Altitude