Ventilatory Response to Exercise - Forster (slides) Flashcards
What is the effect of the normal exercise response on alveolar O2 and CO2? What is the significance of this?
How does this change with increased airway resistance?
Exercise normally has little to no effect on alveolar O2 and CO2. This indicates that increased metabolic demands are met by increased alveolar ventilation.
With increased airway resistance, the body cannot maintain homeostasis of alveolar gases - therefore O2 falls and CO2 rises.
What is the alveolar response at…
- Low workloads
- High workloads
- Low workload response is to increase tidal volume (VT), resulting in more atmospheric air reaching the alveoli, decreasing the deadspace:tidal volume ratio
- High workload response is due to diminishing returns in increased tidal volume (the lung becomes less compliant at higher volumes). At these levels, most compensation is achieved through increased respiratory rate.
Aterial blood gases homeostasis is maintained up until approximately what percentage of maximal metabolic rate?
Why is this significant (think hyperpnea of exercise)
Above 60%, what accounts for the decrease in arterial pH?
~60%
the signal for hyperpnea from exercise cannt be derived from chemoreceptor signalling
Lactic acid production
What physiologic measure is a good index of exercise work load?
heart rate
What causes the increase in DLco during exercise?
At high workloads, the DLco no longer increases proportionally to work. However, PaO2 is maintained at normal levels. How?
Increased recruitment of alveolar-capillary units increases the surface area for gas exchange
Hyperventilation - increases PAO2, increasing the alveolar-capillary driving force
Explain the initial rapid increase in ventilation early in exercise. Is this a metabolic process?
No - not a metabolic process. Likely due to brain signaling, although the reason for this is not completely understood.
