Which combination represents adequate spontaneous ventilation in an adult?

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Multiple Choice

Which combination represents adequate spontaneous ventilation in an adult?

Adequate spontaneous ventilation means enough alveolar ventilation to support gas exchange, which depends on both tidal volume and rate. In adults, a practical rest range is about 500 mL per breath with roughly 12 breaths per minute, giving roughly 4–7 L/min of alveolar ventilation after accounting for dead space. The best choice here uses a tidal volume of 600 mL at 12 breaths per minute. With an estimated dead space of about 150 mL, alveolar ventilation per breath is 600 − 150 = 450 mL. Multiplying by 12 breaths per minute gives about 5.4 L/min of alveolar ventilation, which is adequate for gas exchange at rest. The other options fall short because their alveolar ventilation is too low: 500 mL at 8/min yields around 2.8 L/min; 300 mL at 16/min yields around 2.4 L/min; and 100 mL at 40/min provides negligible alveolar ventilation despite the high rate. That makes them inadequate for maintaining proper CO2 removal and O2 delivery.

Adequate spontaneous ventilation means enough alveolar ventilation to support gas exchange, which depends on both tidal volume and rate. In adults, a practical rest range is about 500 mL per breath with roughly 12 breaths per minute, giving roughly 4–7 L/min of alveolar ventilation after accounting for dead space.

The best choice here uses a tidal volume of 600 mL at 12 breaths per minute. With an estimated dead space of about 150 mL, alveolar ventilation per breath is 600 − 150 = 450 mL. Multiplying by 12 breaths per minute gives about 5.4 L/min of alveolar ventilation, which is adequate for gas exchange at rest.

The other options fall short because their alveolar ventilation is too low: 500 mL at 8/min yields around 2.8 L/min; 300 mL at 16/min yields around 2.4 L/min; and 100 mL at 40/min provides negligible alveolar ventilation despite the high rate. That makes them inadequate for maintaining proper CO2 removal and O2 delivery.

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