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Pulmonary Ventilation during Exercise. Ventilation in Steady Rate Exercise During light & moderate steady rate exercise, V E :VO 2 linear relationship.

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Presentation on theme: "Pulmonary Ventilation during Exercise. Ventilation in Steady Rate Exercise During light & moderate steady rate exercise, V E :VO 2 linear relationship."— Presentation transcript:

1 Pulmonary Ventilation during Exercise

2 Ventilation in Steady Rate Exercise During light & moderate steady rate exercise, V E :VO 2 linear relationship. During light & moderate steady rate exercise, V E :VO 2 linear relationship. Ventilatory equivalent for oxygen (V E :VO 2 ): ratio of minute ventilation to oxygen uptake. Ventilatory equivalent for oxygen (V E :VO 2 ): ratio of minute ventilation to oxygen uptake. –Usually 25 : 1 during submaximal exercise up to 55% max.

3 Ventilation in Steady Rate Exercise Ventilatory response to fixed level of submaximal exercise can be divided into 4 phases. Ventilatory response to fixed level of submaximal exercise can be divided into 4 phases. 1.Sudden increase at onset. 2.Ventilation gradually increases to higher steady- rate level. 3.Steady state level of ventilation maintained. 4.Recovery period gradual return to resting levels. Phase IV higher than resting levels coincide with EPOC. Phase IV higher than resting levels coincide with EPOC.

4 Ventilation in Steady Rate Exercise Ventilatory equivalent for carbon dioxide (V E :VO 2 ): ratio of minute ventilation to carbon dioxide produced. Ventilatory equivalent for carbon dioxide (V E :VO 2 ): ratio of minute ventilation to carbon dioxide produced. –Remains constant during steady rate exercise because pulmonary ventilation eliminates CO 2.

5 Ventilation in Non-Steady-Rate Exercise Minute ventilation (V E ) increases in proportion to oxygen consumption over range from rest to moderate exercise. Minute ventilation (V E ) increases in proportion to oxygen consumption over range from rest to moderate exercise. V E increases dispropor- tionately to oxygen consumption over range from moderate to strenuous. V E increases dispropor- tionately to oxygen consumption over range from moderate to strenuous.

6 Ventilation in Non-Steady-Rate Exercise The point at which ventilation increases disproportionately with oxygen uptake during incremental exercise is termed: ventilatory threshold (VT). The point at which ventilation increases disproportionately with oxygen uptake during incremental exercise is termed: ventilatory threshold (VT).

7 Ventilation in Non-Steady-Rate Exercise Lactic acid generated during anaerobic glycolysis is buffered in blood by sodium bicarbonate. Lactic acid generated during anaerobic glycolysis is buffered in blood by sodium bicarbonate. Lactic acid + NaHCO 3 → Na Lactate + H 2 CO 3 → H CO 2

8 Ventilation in Non-Steady-Rate Exercise The excess, non- metabolic CO 2 stimulates ventilation. The excess, non- metabolic CO 2 stimulates ventilation. Recall that metabolic CO 2 is produced in Krebs Cycle in oxidation of acetyl CoA. Recall that metabolic CO 2 is produced in Krebs Cycle in oxidation of acetyl CoA.

9 Ventilation in Non-Steady-Rate Exercise The non-metabolic CO 2 from buffering HLa drives increased V E to eliminate it, so V E : VCO 2 remains constant. The non-metabolic CO 2 from buffering HLa drives increased V E to eliminate it, so V E : VCO 2 remains constant. The increased in V E exceeds increase in VO 2 disproportionately. The increased in V E exceeds increase in VO 2 disproportionately. The point at which V E O 2 breaks with linearity is the ventilatory threshold. The point at which V E O 2 breaks with linearity is the ventilatory threshold. RER = 1 where two lines intersect. R values > 1 indicate CO 2 production exceeds O 2 consumption, evidence of non-metabolic CO2 production.

10 Ventilation in Non-Steady-Rate Exercise As exercise intensity increases, blood lactate begins to systematically increase over a baseline value of 4 mM/L termed onset of blood lactate. As exercise intensity increases, blood lactate begins to systematically increase over a baseline value of 4 mM/L termed onset of blood lactate. Blood lactate accumulation associated with changes in CO 2 production, blood pH, bicarbonate, [H + ], RER. Blood lactate accumulation associated with changes in CO 2 production, blood pH, bicarbonate, [H + ], RER.

11 Ventilation in Non-Steady-Rate Exercise Although variables (CO 2 production, blood pH, bicarbonate, [H + ], RER) are related to OBLA, doubtful that VT can be used to denote onset of anaerobic metabolism. Although variables (CO 2 production, blood pH, bicarbonate, [H + ], RER) are related to OBLA, doubtful that VT can be used to denote onset of anaerobic metabolism. OBLA directly assessed by measuring lactate level in blood. OBLA directly assessed by measuring lactate level in blood.

12 Ventilation in Non-Steady-Rate Exercise Common practice to use “bloodless” techniques e.g. R >1, or break in ventilatory equivalent for oxygen to denote anaerobic threshold. Common practice to use “bloodless” techniques e.g. R >1, or break in ventilatory equivalent for oxygen to denote anaerobic threshold.

13 Does Ventilation Limit Aerobic Capacity for Average Person? If inadequate breathing capacity limited aerobic capacity, ventilatory equivalent for oxygen would decrease. If inadequate breathing capacity limited aerobic capacity, ventilatory equivalent for oxygen would decrease. Actually, healthy person tends to over-breathe in relation to VO 2. Actually, healthy person tends to over-breathe in relation to VO 2. In strenuous exercise, decreases arterial PCO 2 & increase Alveolar PO 2. In strenuous exercise, decreases arterial PCO 2 & increase Alveolar PO 2.

14 Work of Breathing Two major factors determine energy requirements of breathing Two major factors determine energy requirements of breathing 1.Compliance of lungs 2.Resistance of airways to smooth flow of air As rate & depth of breathing increase during exercise, energy cost of breathing increases too. As rate & depth of breathing increase during exercise, energy cost of breathing increases too. At maximal exercise when V E = 100 L/m, oxygen cost of breathing represents 10-20% of total VO 2. At maximal exercise when V E = 100 L/m, oxygen cost of breathing represents 10-20% of total VO 2.

15 Work of Breathing Acute effects of 15 puffs on a cigarette during a 5- minute period Acute effects of 15 puffs on a cigarette during a 5- minute period –3 fold increase in airway resistance –Lasts an average 35 minutes Smokers exercising at 80% Smokers exercising at 80% –Energy requirement of breathing after smoking was 14% of oxygen uptake –Energy requirement of breathing no cigarettes was only 9%.

16 References Axen and Axen Illustrated Principles of Exercise Physiology. Prentice Hall. Axen and Axen Illustrated Principles of Exercise Physiology. Prentice Hall. Kapit, Macey, Meisami Physiology Coloring Book. Harper & Row. Kapit, Macey, Meisami Physiology Coloring Book. Harper & Row. McArdle, Katch, Katch Image Collection Essentials of Exercise Physiology, 3 rd ed. Lippincott William & Wilkens. McArdle, Katch, Katch Image Collection Essentials of Exercise Physiology, 3 rd ed. Lippincott William & Wilkens.


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