Am. J. Respir. Crit. Care Med.,
Volume 163, Number 2, February 2001, 458-462
Isocapnic Hyperventilation Increases Carbon Monoxide
Elimination and Oxygen Delivery
THOMAS C.
KRECK,
ERIN D.
SHADE,
WAYNE J. E.
LAMM,
STEVEN E.
MCKINNEY,
and
MICHAEL P.
HLASTALA
Departments of Medicine, Physiology, and Biophysics, University of Washington, Seattle, Washington
Hyperventilation with mixtures of O2 and CO2 has long been known
to enhance carbon monoxide (CO) elimination at low HbCO levels in animals and humans. The effect of this therapy on oxygen delivery (DO2) has not been studied. Isocapnic hyperventilation utilizing mechanical ventilation may decrease cardiac output and therefore decrease DO2 while increasing CO elimination. We studied the
effects of isocapnic hyperventilation on five adult mechanically
ventilated sheep exposed to multiple episodes of severe CO poisoning. Five ventilatory patterns were studied: baseline minute
ventilation (RR · VT), twice (2 · RR) and four times (4 · RR) baseline
respiratory rate, and twice (2 · VT) and four times (4 · VT) baseline
tidal volume. The mean carboxyhemoglobin (HbCO) washout
half-time (t1/2) 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. DO2 was increased during hyperventilation compared with baseline ventilation for 2 · VT, 4 · RR, and 4 · VT ventilatory patterns. Isocapnic hyperventilation, in our animal model, did not alter arterial or pulmonary blood pressures, arterial pH, or cardiac output. Isocapnic hyperventilation is a promising therapy for CO poisoning.
