Gas Exchange Gas Exchange IIIIII

Utilization Coefficient Utilization Coefficient

The OThe O22 being utilized by the body being utilized by the body At rest 25% for skeletal muscle while for At rest 25% for skeletal muscle while for

cardiac muscle = 70%cardiac muscle = 70% In exercise increased to 75 – 85%In exercise increased to 75 – 85% %age of blood that gives up its oxygen while %age of blood that gives up its oxygen while

passing through peripheral tissue capillariespassing through peripheral tissue capillaries

Oxygen transport in dissolved stateOxygen transport in dissolved state 3%3% 0.17 ml/dl of blood0.17 ml/dl of blood Hb-CO COMBINATION:Hb-CO COMBINATION: CO affinity for Hb is 250 times more as compared CO affinity for Hb is 250 times more as compared

to oxygento oxygen CO poisoning can be lethal , oxygen Pp is normal, CO poisoning can be lethal , oxygen Pp is normal,

no clinical signs of hypoxemia (cyanosis)no clinical signs of hypoxemia (cyanosis)

Due to lack of oxygen patient becomes Due to lack of oxygen patient becomes disoriented and un consciousdisoriented and un conscious

No feedback mechanisms to correct deficiency No feedback mechanisms to correct deficiency of oxygenof oxygen

Patient can get benefit from oxygen and CO2 Patient can get benefit from oxygen and CO2 therapytherapy

Transport of COTransport of CO22

COCO22 20% more dissolvable than O 20% more dissolvable than O22 in body fluids in body fluids

COCO22 produced in more quantity than can be dissolved produced in more quantity than can be dissolved

4 ml CO4 ml CO22 given out at lung level given out at lung level

COCO22 transported in three ways transported in three ways

PCOPCO22 of venous blood = 45 mmHg – CO of venous blood = 45 mmHg – CO22 dissolved = dissolved =

2.7 ml/dl2.7 ml/dl PCOPCO22 of arterial blood = 40 mmHg – CO of arterial blood = 40 mmHg – CO22 dissolved is dissolved is

2.4 ml/dl2.4 ml/dl

So only 0.3 ml of COSo only 0.3 ml of CO22 transported as dissolved transported as dissolved

form in plasma = 7%form in plasma = 7% 93% CO93% CO22 diffused into RBCs. diffused into RBCs. In RBC – either binds directly with Hb to form In RBC – either binds directly with Hb to form

Hb-COHb-CO22 or converted to HCO or converted to HCO33 ion ion

23% CO23% CO22 form Hb-CO form Hb-CO22

70% CO70% CO22 form HCO form HCO33 ion ion

Formation of HCOFormation of HCO33 ion ion → →

a – COa – CO22 transportation transportation

b – Buffers metabolic acids b – Buffers metabolic acids

In RBC – COIn RBC – CO22 + H + H22O O → H→ H22COCO33 → H+ +HCO → H+ +HCO33 - - Reaction – Reversible and obeys the law of mass Reaction – Reversible and obeys the law of mass

actionaction To keep the reaction move on – H+ HCOTo keep the reaction move on – H+ HCO33 removed as removed as

H+Hb → H.Hb & HCOH+Hb → H.Hb & HCO33 gets out from RBC into gets out from RBC into

plasmaplasma Done by chloride shift – Antiport transport – Also Done by chloride shift – Antiport transport – Also

called Hamburgs shiftcalled Hamburgs shift Exchange of one Cl- & one HCOExchange of one Cl- & one HCO33 - - Cl inside RBC – RBC size biggerCl inside RBC – RBC size bigger Venous blood – MCV ↑, Hematocrit 3%greater than Venous blood – MCV ↑, Hematocrit 3%greater than

of arterial blood of arterial blood

At lung level – dissolved COAt lung level – dissolved CO22 diffused out, diffused out,

draws dissolved COdraws dissolved CO22 from RBC from RBC → CO→ CO22 – –

HCOHCO33 balance disturbed – law of Mass action balance disturbed – law of Mass action

Cl – HCOCl – HCO33 exchange in reverse direction exchange in reverse direction CarbaminohemoglobinCarbaminohemoglobin 23% directly attached with Hb23% directly attached with Hb Also attached with other plasma proteins but Also attached with other plasma proteins but

not significant not significant

HELDANE EFFECTHELDANE EFFECT

Combination of OCombination of O22 with Hb – forming Hb a strong with Hb – forming Hb a strong

acid acid → CO→ CO22 displacement( at level of lungs) displacement( at level of lungs)

a – Acidic Hb – less affinity for COa – Acidic Hb – less affinity for CO22

b – Acidic Hb → release of H+ ion to b – Acidic Hb → release of H+ ion to form form HH22COCO33 & then CO & then CO22 which is which is released into released into

lunglung At tissue level – OAt tissue level – O22 removed and so more affinity removed and so more affinity

for COfor CO22 (Bohr effect). (Bohr effect).

Respiration During ExerciseRespiration During Exercise

Pulmonary ventilation Pulmonary ventilation ↑↑ Rate & Depth of respiration ↑Rate & Depth of respiration ↑ Temp → Respiration ↑Temp → Respiration ↑ Metabolic rate → respiration ↑Metabolic rate → respiration ↑

Body consumption of OBody consumption of O22 at rest 250ml/mints, In at rest 250ml/mints, In exercise 4 – 5L/mintsexercise 4 – 5L/mints

OO22 extraction ratio 25%, in exercise 75 – 80% extraction ratio 25%, in exercise 75 – 80%

Oxygen diffusing capacity inc. – Oxygen diffusing capacity inc. – 65ml/min/mmHg65ml/min/mmHg

CO2 diffusing capacity inc. – 1200 CO2 diffusing capacity inc. – 1200 ml/min/mmHg.ml/min/mmHg.

OO22 Debt Debt

Usual body storage of OUsual body storage of O22 = 2L = 2L

1 – 0.3 L in muscle fibers to Myoglobin 1 – 0.3 L in muscle fibers to Myoglobin 2 – 1L to Hb 2 – 1L to Hb 3 – 0.5L in Alveolar air 3 – 0.5L in Alveolar air 4 – 0.25L in dissolved form in body fluids 4 – 0.25L in dissolved form in body fluids

After exercise this 2L reservoir of OAfter exercise this 2L reservoir of O22 must be must be

replenished by breathing over & above the replenished by breathing over & above the normal requirement normal requirement

In addition 8 – 9 L needed to reconstitute In addition 8 – 9 L needed to reconstitute ATPs consumed during exercise ATPs consumed during exercise

So total 10-12 L of OSo total 10-12 L of O22 needed after exercise to needed after exercise to

be at normal – called Obe at normal – called O22 debt debt

OO22 debt repaid during 90 minutes rapid debt repaid during 90 minutes rapid

breathing after exercisebreathing after exercise During exercise both nervous & chemical During exercise both nervous & chemical

stimulation of respirationstimulation of respiration

The additional oxygen that must be taken in to The additional oxygen that must be taken in to body after vigorous exercise to restore all body after vigorous exercise to restore all systems to their normal states is called oxygen systems to their normal states is called oxygen debt. After exercise 4 tasks need to be debt. After exercise 4 tasks need to be completedcompleted

Replenishment of ATPReplenishment of ATP Removal of lactic acidRemoval of lactic acid Replenishment of myoglobin with oxygenReplenishment of myoglobin with oxygen Replenishment of glycogenReplenishment of glycogen

High altitude Changes High altitude Changes

Atmosph. Pressure at sea level=760mmHg and Atmosph. Pressure at sea level=760mmHg and PO2=160mmHg PO2=160mmHg

As one ascends – Atmosph. pressure keeps on As one ascends – Atmosph. pressure keeps on decreasing decreasing

Composition or percentage of constituent gases Composition or percentage of constituent gases remains sameremains same

At 10,000 feet = 523 mmHg , PO2 in air=110mmHg At 10,000 feet = 523 mmHg , PO2 in air=110mmHg At 50,000 feet = 87 mmHg, PO2 in air=18mmHgAt 50,000 feet = 87 mmHg, PO2 in air=18mmHg Acclimatization – try to be normal at high altitude Acclimatization – try to be normal at high altitude

despite low levels of oxygen.despite low levels of oxygen.

AcclimatizationAcclimatization At 10,000 feet, atmosph pressure = 523 and At 10,000 feet, atmosph pressure = 523 and

alveolar POalveolar PO22 = 67mmHg = 67mmHg The changes in body in response to hypoxia The changes in body in response to hypoxia

if somebody stays at high altitude for if somebody stays at high altitude for sometime aresometime are

1.1. Great increase in pulmonary ventilationGreat increase in pulmonary ventilation2.2. Increases RBCs numberIncreases RBCs number3.3. Increased diffusing capacity of lungsIncreased diffusing capacity of lungs4.4. Increased vascularity of the tissueIncreased vascularity of the tissue5.5. Increased ability of tissue cells to use oxygen Increased ability of tissue cells to use oxygen

despite low POdespite low PO22

Increased Pulmonary VentilationIncreased Pulmonary Ventilation

Hypoxic stimulation of resp. center by Hypoxic stimulation of resp. center by peripheral Chemoreceptorsperipheral Chemoreceptors

Immediate compensation to Immediate compensation to ↓PO↓PO22 by, ↑ by, ↑ alveolar ventilation to alveolar ventilation to →↑ CO→↑ CO22 exhalation. exhalation.

This decreased PCOThis decreased PCO22 → inhibitory effect on → inhibitory effect on resp. center, opposing the stimulatory effect of resp. center, opposing the stimulatory effect of dec. PO2dec. PO2

After a few days stimulatory effect After a few days stimulatory effect overwhelms inhibitory effect b/c of ↓ HCOoverwhelms inhibitory effect b/c of ↓ HCO33 ions in brain(kidneys excrete bicarbs)ions in brain(kidneys excrete bicarbs)

Increased RBCs CountIncreased RBCs Count

Hypoxia Hypoxia → erythropoietin →↑ RBC → erythropoietin →↑ RBC productionproduction

Hct from normal (40-45) to 60-65Hct from normal (40-45) to 60-65

Hb from normal (15mg/dl) to 20-22 g/dlHb from normal (15mg/dl) to 20-22 g/dl

Increased Diffusing CapacityIncreased Diffusing Capacity

↑ ↑ Pulmonary capillary blood vol. → capillaries Pulmonary capillary blood vol. → capillaries expanding → ↑ surface areaexpanding → ↑ surface area

Also inc in air vol. → ↑ surface areaAlso inc in air vol. → ↑ surface area Inc in pulm. artery blood pressure– more perfusionInc in pulm. artery blood pressure– more perfusion So diffusing capacity for OSo diffusing capacity for O22 from normal from normal

(21 ml/mint/mmHg) to 65 ml/mint/mmHg (21 ml/mint/mmHg) to 65 ml/mint/mmHg

Increased Vascularity of Tissue Increased Vascularity of Tissue (Circulatory Changes)(Circulatory Changes)

Initially Initially ↑ cardiac out by 30% approx.↑ cardiac out by 30% approx. As Hct ↑ - C.O. becomes normal As Hct ↑ - C.O. becomes normal ↑ ↑ in number of capillaries in non-pulmonary in number of capillaries in non-pulmonary

areas – called increased capillarity areas – called increased capillarity (angiogenesis)(angiogenesis)

Hypoxia → pulmonary vasoconstriction → Hypoxia → pulmonary vasoconstriction → Retrograde pressure on Rt heart → Rt Retrograde pressure on Rt heart → Rt ventricular hypertrophy ventricular hypertrophy

Pulmonary vasoconstriction → pulmonary Pulmonary vasoconstriction → pulmonary hypertension hypertension

Cellular AcclimatizationCellular Acclimatization

More capillary formation in tissues More capillary formation in tissues → ↑ → ↑ vascularity vascularity

Also ↑ number of mitochondria & Cytochrome Also ↑ number of mitochondria & Cytochrome oxidase enzyme oxidase enzyme

Acute Mountain SicknessAcute Mountain Sickness

May be nausea, vomiting, headache, Irritability, May be nausea, vomiting, headache, Irritability, dyspnoea, at 12000ftdyspnoea, at 12000ft

At 18000 ft - twitching, seizuresAt 18000 ft - twitching, seizures At 23000 ft – coma leading to deathAt 23000 ft – coma leading to death Cerebral vasodilatation in response to hypoxia Cerebral vasodilatation in response to hypoxia

→fluid leakage into cerebral tissue → cerebral →fluid leakage into cerebral tissue → cerebral edema → disorientation & other cerebral edema → disorientation & other cerebral dysfunctiondysfunction

Pulmonary edema – exact cause not knownPulmonary edema – exact cause not known Takes 8-24 hrs to develop Takes 8-24 hrs to develop

Chronic Mountain SicknessChronic Mountain Sickness RBC count RBC count ↑ - so Hct ↑ ↑ - so Hct ↑ Pulmonary arterial pressure ↑Pulmonary arterial pressure ↑ Rt heart – hypertrophy failure Rt heart – hypertrophy failure ↑ ↑ Hct → ↑ blood viscosity → sluggish circulation → Hct → ↑ blood viscosity → sluggish circulation →

decreased Odecreased O2 2 supply to peripheral tissuessupply to peripheral tissues Natives at high altitude – Natives at high altitude –

Chest barrel shaped – chest largerChest barrel shaped – chest larger Body size decreased- high ratio of ventilatory capacity to Body size decreased- high ratio of ventilatory capacity to

body massbody mass Aortic & carotid bodies of bigger sizeAortic & carotid bodies of bigger size Pulmonary hypertension & Rt ventricular hypertrophy Pulmonary hypertension & Rt ventricular hypertrophy ↑ ↑ RBC count with ↑ HctRBC count with ↑ Hct

Deep Sea Diving & Hyperbaric ConditionDeep Sea Diving & Hyperbaric Condition

Atmospheric pressure = 760 mmHgAtmospheric pressure = 760 mmHg Deep into sea, at every 33 feet pressure rises Deep into sea, at every 33 feet pressure rises

by 1 atmosphere by 1 atmosphere Vol. of air compressed & pressure increased Vol. of air compressed & pressure increased

along with depthalong with depth Deep sea diver – breath high pressure airDeep sea diver – breath high pressure air

Nitrogen Narcosis at High Nitrogen Nitrogen Narcosis at High Nitrogen PressurePressure

About 4/5About 4/5thth of air – nitrogen of air – nitrogen At sea level no ill effect of nitrogen but at high At sea level no ill effect of nitrogen but at high

pressure (deep in sea) varying degree of pressure (deep in sea) varying degree of narcosisnarcosis

First symptom of narcosis joviality, at 120 feet First symptom of narcosis joviality, at 120 feet deep, after remaining for some timedeep, after remaining for some time

At 150 – 200 feet – Drowsy At 150 – 200 feet – Drowsy At 200 – 250 feet – Strength wanes,At 200 – 250 feet – Strength wanes, Beyond 250 feet – person can’t moveBeyond 250 feet – person can’t move

Nitrogen narcosis is like alcohol intoxication, Nitrogen narcosis is like alcohol intoxication, impaired memory, impaired thought making impaired memory, impaired thought making

Nitrogen mech. Same as that of gas anesthesia Nitrogen mech. Same as that of gas anesthesia Nitrogen 5 time more soluble in fat than in waterNitrogen 5 time more soluble in fat than in water At sea level 1 L of nitrogen dissolved in entire body, At sea level 1 L of nitrogen dissolved in entire body,

half in body fluids & half in fat ( though fat half in body fluids & half in fat ( though fat constitutes 15% of total body)constitutes 15% of total body)

At 33 feet deep – 2 L of nitrogen get dissolved in At 33 feet deep – 2 L of nitrogen get dissolved in bodybody

At 100 feet deep 4 L of nitrogen At 100 feet deep 4 L of nitrogen Nitrogen can not be metabolized in body Nitrogen can not be metabolized in body Diver ascends slowly to sea level Diver ascends slowly to sea level In case of rapid ascent In case of rapid ascent → decompression sickness→ decompression sickness

Decompression SicknessDecompression Sickness Also called bends, compressed air sickness, caisson Also called bends, compressed air sickness, caisson

disease, divers paralysis, dysbarism disease, divers paralysis, dysbarism During rapid ascent, sufficient amount of nitrogen During rapid ascent, sufficient amount of nitrogen

bubbles develop in body fluids either extra or intra bubbles develop in body fluids either extra or intra cellularly cellularly

Depending upon the no. & size of nitrogen bubble, Depending upon the no. & size of nitrogen bubble, any area of the body can get damageany area of the body can get damage

Bubble formation in brain vessels Bubble formation in brain vessels → paralysis; → paralysis; Around nerves → paraesthesia itching, severe pain; Around nerves → paraesthesia itching, severe pain; Around joints → severe pain in joints (called Around joints → severe pain in joints (called bends); In pulmonary vessels → Dyspnoea & bends); In pulmonary vessels → Dyspnoea & chokes, coronary arteries → cardiac damage chokes, coronary arteries → cardiac damage

Treatment of rapid ascent to sea levelTreatment of rapid ascent to sea level

Recompression of divers with the same Recompression of divers with the same ↑ ↑ pressure under which they remain in the seapressure under which they remain in the sea

Then decompression done graduallyThen decompression done gradually

Respiratory Exchange RatioRespiratory Exchange Ratio

R = Respiratory exchange ratio, betweenR = Respiratory exchange ratio, between

OO22 transport & CO transport & CO22 transport = 4/5 = 0.8 transport = 4/5 = 0.8

Respiratory Quotient (RQ)Respiratory Quotient (RQ)

Almost similar to RAlmost similar to R Ratio of CORatio of CO22 output and O output and O22 consumed per consumed per

units time, same as exchange ratio = 0.8units time, same as exchange ratio = 0.8 RQ RQ ↑ - when on carbohydrate rich diet ↑ - when on carbohydrate rich diet RQ ↓ - when on fat rich dietRQ ↓ - when on fat rich diet R & RQ - ↑ in hyperventilation, severe R & RQ - ↑ in hyperventilation, severe

exercise, metabolic acidosis,exercise, metabolic acidosis, R & RQ - ↓ - Metabolic alkalosis, R & RQ - ↓ - Metabolic alkalosis,

hypoventilation or just after the exercise. hypoventilation or just after the exercise.