Isocapnic hyperventilation increases carbon monoxide elimination and oxygen delivery

Hyperventilation with mixtures of O-2 and CO2 has long been known to enhanc e carbon monoxide (CO) elimination at low HbCO levels in animals and humans . The effect of this therapy on oxygen delivery (Dol) has not been studied. Isocapnic hyperventilation utilizing mechanical ventilation may decrease c ardiac output and therefore decrease Do, while increasing CO elimination. W e studied the effects of isocapnic hyperventilation on five adult mechanica lly ventilated sheep exposed to multiple episodes of severe CO poisoning. F ive ventilatory patterns were studied: baseline minute ventilation (RR . VT ), twice (2 . RR) and four times (4 . RR) baseline respiratory rate, and tw ice (2 . VT) and four times (4 . VT) baseline tidal volume. The mean carbox yhemoglobin (HbCO) washout half-time (t(1/2)) was 14.3 +/- 1.6 min for RR . VT, decreasing to 9.5 +/- 0.9 min for 2 . RR, 8.0 +/- 0.5 min for 2 . VT, 6.2 +/- 0.5 min for 4 . RR, and 5.2 +/- 0.5 min for 4 . VT. Do(2) was incre ased during hyperventilation compared with baseline ventilation for 2 . VT, 4 . RR, and 4 . VT ventilatory patterns. Isocapnic hyperventilation, in ou r animal model, did not alter arterial or pulmonary blood pressures, arteri al pH, or cardiac output. Isocapnic hyperventilation is a promising therapy for CO poisoning.