The record of a patient on mechanical ventilation reveals the following information: VE = 10 L/min, PaCO₂= 43 mm Hg $ \mathrm{P}_{\overline{\mathrm{E}}} \mathrm{CO}_{2} $ , = 17 mm Hg, PaO₂ = 70 mm Hg.Can ventilation be considered efficient for this patient?

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Quizplus · Accepted Answer

Using appropriate data from above, VD/VE = (43 - 17)/43 VD/VE = 26/43 VD/VE = 0.6 This meAnswer 0.6, or 60%, of the VE is dead space ventilation, leaving 40% for VA. Specifically, VD = 0.6(10 L/min) = 6 L/min VA = 0.4(10 L/min) = 4 L/min A normal VD/VT or VD/VE is about 0.25 to 0.40. An abnormally high amount of this patient's VE is used to ventilate nonperfused dead space. Thus ventilation is relatively inefficient; a high minute ventilation is required to maintain a normal PaCO₂ of 43 mm Hg (see previous patient data). The patient may have difficulty breathing spontaneously because the work of breathing required to sustain a normal PaCO₂ is abnormally high.

The Record of a Patient on Mechanical Ventilation Reveals the Following