Average resting tidal volume (TV) is 500 mL (0.5 L) and resting breathing freque

Question

Average resting tidal volume (TV) is 500 mL (0.5 L) and resting breathing frequency is 12 breaths per minute (bpm).

What would be the ideal way to increase ventilation to 12 L/min?

How would this change alveolar ventilation?

If arterial PO2 falls by 10% (from 95 mmHg to 85.5 mmHg) what will happen to ventilation?

H+ and O2 both bind to the same place on hemoglobin. If you have more H+ than O2, what happens to the oxyhemoglobin saturation?

What is the resting PO2 difference between arterial blood and muscle tissue?

How does this difference change during exercise and why?

If you increase tidal volume during exercise, what happens to the PO2 in the alveoli?

Atmospheric air is 20.95% O2 and 0.04% CO2, what is PO2 and PCO2 when the atmospheric pressure is 622 mmHg (Denver, CO)?

How would this change diffusion of O2 and CO2 in the lungs?

Explanation / Answer

To increase minute alveolar ventilation volume, the body increases both- rate of ventilation and volume of ventilation. The body brings into play, the inspiratory reserve volume and also increase the number of breaths by making expiration also an active process.

If arterial PO2 falls along with arterial PCo2 increase, then rate of ventilation is increased but if only arterial PO2 falls and all other parameters remain unaffected then no change in rate of ventilation is observed. This is because chemoreceptors in body are not sensetive to oxygen concentration but only to carbon dioxide and H+.

OxyHb saturation curve downshifts in acidic pH. In other words, the affinity for oxygen on Hb decreases in acidic pH. Thus less oxygen will bind to Hb if more H+ is present.

The resting difference between arterial and muscular oxygen partial pressures is about 55 mm Hg- arterial pressure at around 95 and muscular at about 40.
During exercise, this difference widens as muscles take up more oxygen from arteries. The muscular oxygen also deplete.

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