Abstract
Objective. Fast paramagnetic oxygen analyzers have made it possible to measure inspiratory to end-tidal oxygen concentration difference (P(i-et)O2) breath-by-breath. It is now frequently displayed on monitors during routine anesthesia. We wanted to study the effects of major changes in metabolism, ventilation and circulation on P(i-et)O2. Methods. Ten healthy male volunteers were studied under exercise. P(i-et)O2 was measured with a fast-response paramagnetic differential oxygen sensor. Cardiac output was measured with non-invasive transthoracic electrical bioimpedance. Metabolism was measured with indirect calorimetry and ventilation with a side stream spirometer. After a rest period, the subjects cycled at 30W and 60W, 6 minutes on each work load and were then observed during 10 minutes of rest. Results. P(i-et)O2 corresponded well to V̇O2/V̇a (the oxygen uptake to alveolar ventilation quotient) correlation showed r = 0.79. P(i-et)O2 was influenced by changes in cardiac output which occurred primarily at the start and at the end of exercise. Expired minute ventilation (V̇e) multiplied by P(i-et)O2 was related to cardiac output with a high intrapersonal correlation. Conclusion. P(i-et)O2 is a good measure of adequate ventilation in relation to the oxygen consumption level and multiplied by V̇e it might offer a non-invasive bedside parameter indicating changes in cardiac output.
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Bengtsson, J., Bengtson, J.P. The inspiratory to end-tidal oxygen difference during exercise. Int. J. Clin. Mon. Comp. 14, 217–223 (1997). https://doi.org/10.1007/BF03356566
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DOI: https://doi.org/10.1007/BF03356566