V ENTILATORY AND B LOOD G AS R ESPONSE TO E XERCISE.
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Transcript of V ENTILATORY AND B LOOD G AS R ESPONSE TO E XERCISE.
VENTILATORY AND BLOOD GAS RESPONSE TO EXERCISE
REST TO WORK TRANSITIONS Change in pulmonary ventilation Observed below lactate threshold
REST TO WORK TRANSITIONS Transition from rest constant-load-submaximal
exercise
Arterial tensions of PCO2 and PO2 are relatively unchanged during transition during submaximal exercise
BUT: arterial PO2 decreases & PCO2 increases slight in transition from rest steady-state exercise
Therefore: at the start of exercise: Increase in ventilation is NOT as fast as increase in metabolism
REST TO WORK TRANSITIONS
At the onset of constant-load submaximal exercise: Initially, ventilation increases rapidly
Then, a slower rise toward steady-state
PO2 and PCO2 are maintainedSlight decrease in PO2 and increase in PCO2
CHANGES IN VENTILATION, PO2 AND PCO2 IN TRANSITION FROM REST TO STEADY STATE SUBMAXIMAL EXERCISE
PROLONGED EXERCISE IN A HOT ENVIRONMENT
Cool, low humidity environment = 19°C, 45% humidity
Hot, high humidity = from 28°C, 75% humidity
Hot environments hamper heat loss from the body
Increase in body temperature which directly affects respiratory control centre
= Minute ventilation increases (with increased breathing frequency)
PROLONGED EXERCISE IN A HOT ENVIRONMENT
During prolongedsub maximal exercise:
Ventilation tends to drift upwards
Little change in PCO2
Higher ventilation not due to increased PCO2
INCREMENTAL EXERCISE
Linear increase in ventilation- Up to 50 – 75% VO2max
Exponential increase beyond this point
Ventilatory threshold- Point where minute ventilation increases exponentially
VENTILATORY THRESHOLD Reflects aerobic fitness without the need to
directly measure maximal oxygen uptake Point during exercise training at which
pulmonary ventilation becomes disproportionately high with respect to oxygen consumption during an incremental exercise test
Used as a guide to determine exercise intensity
Therefore: Ventilatory threshold = intensity of exercise that shows a larger ventilation than required to do work.
At this point, the contribution of anaerobic metabolism becomes significant to produce larger concentrations of lactic acid.
Lactic acid accumulates, reducing pH & increasing metabolic acidosis.
Because one of the functions of the respiratory system is acid-base balance, respiration must increase to compensate for the increased acidosis.
The point were ventilation deviates from linearity
is termed the ventilatory threshold (TVENT).
VENTILATORY RESPONSE TO EXERCISE
Trained vs. Untrained:
Trained:- Decrease in arterial PO2 near exhaustion- pH maintained at a higher work rate- Ventilatory threshold occurs at higher work
rate
EFFECT OF TRAINING ON VENTILATION
Untrained: able to maintain PO2 in arteries within 10–12 mmHg of resting value
Trained: PO2 decreases by 30- 40 mmHg during heavy exercise
*low arterial PO2 vales during exercise = exercise induced hypoxemia
* Low arterial Po2 values are also seen in patients with severe lung disease
MALES VS. FEMALE ATHLETES
50% of highly trained male endurance athletes develop exercise induced hypoxemia
Females are suggested to have experience exercise induced hypoxemia more often than males
CAUSES Failure of pulmonary system?
Ventilation perfusion mismatch?Indicates matching of blood flow to ventilation Ideal: ~1.0Light exercise improvesHeavy exercise = inequality
Diffusion limitations during exercise ?Reduced amount of time that red blood cells spend in the pulmonary capillaries...caused by high cardiac outputs from athletes less time for gas equilibrium to be achieved
VENTILATORY RESPONSE TO EXERCISE: TRAINED VS. UNTRAINED
REVISION QUESTIONS
1. Describe the changes in PO2 and PCO2 with different exercises. (6)
2. What happens during prolonged sub maximal exercise? Why does this occur? (6)
3. What happens during incremental exercise? (3)4. Explain the Ventilatory Threshold (8)5. How do trained and untrained athlete’s ventilatory
responses differ? (6)6. How do male and female ventilatory responses
differ? (2)7. What is hypoxemia and how does it relate to
exercise? (4)8. What are the suggested causes to hypoxemia
in athletes? (6)