Effects of hyperventilation on the inspiratory to end-tidal oxygen difference

Abstract

We assessed the inspiratory to end-tidal oxygen difference during voluntary hyperventilation in 10 healthy male volunteers. The oxygen difference was measured with a fast-response paramagnetic differential oxygen sensor. As simultaneous changes in metabolism and cardiac output also influence oxygen uptake was measured with indirect calorimetry and noninvasive transthoracic electrical bioimpedance was used for measurement of cardiac output. After a rest period, subjects were instructed to double their minute ventilation volume (VE) and after 5 min triple their resting VE for another 5 min. decreased from a zero value of 6.4 kPa to 3.9 kPa at 5min (P < 0.01) and 2.9kPa at 10min (P < 0.01). At 15min (i.e. 5min after the end of hyperventilation) there was an increase in to 8.3 kPa (P < 0.05). Regression analysis between (kPa) and VE (litre m-2 min-1) gave the formula: , r = -0.92, n = 158. Oxygen uptake and cardiac output did not change significantly during hyperventilation, but decreased in the post-hyperventilation period. An oxygen difference of more than 8 kPa was associated with significant arterial desaturation. © 1994 British Journal of Anaesthesia.