Assuming a dead space volume of 150 mL, which of the following would yield the lowest minute alveolar ventilation?

To determine which combination yields the lowest minute alveolar ventilation, it's essential to understand how to calculate it. Minute alveolar ventilation is defined as the volume of fresh air that reaches the alveoli per minute, which can be calculated using the formula:

Minute Alveolar Ventilation = (Tidal Volume - Dead Space Volume) × Respiratory Rate.

Given a dead space volume of 150 mL, we can assess each option by calculating the effective tidal volume (the volume that contributes to alveolar ventilation) and then applying it in the formula.

For each choice:

• In the first option, with a respiratory rate of 10 breaths/min and a tidal volume of 500 mL, the effective tidal volume is 500 mL - 150 mL = 350 mL. Therefore, the minute alveolar ventilation is 350 mL × 10 = 3500 mL/min.

• The second choice presents a respiratory rate of 16 breaths/min with a tidal volume of 300 mL. The effective tidal volume here is 300 mL - 150 mL = 150 mL. Thus, the minute alveolar ventilation calculates to 150 mL × 16 = 2400 mL/min.