Propofol infusion for coronary artery bypass surgery in a patient with suspected malignant hyperpyrexia

0.29), WcoZ (after a single large breath) is 5.15 kPa (SEM 0.30), and (a E ’ ) P c ~ ~ is 0.22 kPa (SEM 0.04). There is a significant difference, as stated by the author, between Paco, and pElcoz in the group of patients studied by him. Therefore, the conclusion derived by the author, ‘in a small group of critically ill patients receiving high frequency jet ventilation, measurement of end-tidal CO, tension following a single large breath did not differ significantly from arterial CO, levels measured simultanously’, is inappropriate and misleading. It might be inferred from this statement that institution of high frequency jet ventilation in critically ill patients leads to near perfect ventilation/perfusion matching which results in PE’co, approaching Paco, in all patients. This is not true. The (a E’)Pco~ value increases in critically ill patients and, with the institution of high frequency jet ventilation, there is an improvement of ventilation/ perfusion matching which results in a reduced (a E’)PCO, difference (0.22 kPa, SEM 0.04 in the group studied by the author, with maximum value of 0.52 kPa). However, the correlation between Paco, and Wco2 (after a single large breath) is good (r = 0.989) and therefore Wco2 (after a single large breath) can be used to predict Pdco, taking into consideration the arterial to end-tidal CO, difference as 0.22 kPa. There is a possibility that this difference could be zero during high frequency jet ventilation in patients with normal cdrdiorespiratory function, in which case the authors’ conclusion would be valid.