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RESEARCH PRODUCT

Blood CO2 and pH Transients During Apnoea after O2 Breathing in Patients

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description

Endotracheal intubation always is combined with an apnoea the duration of which is dependent on the technique used, the skills of the intubator, and the anatomical situation. The resulting typical potential risks may be (among others) both hypoxaemia and hypercapnia. Therefore the tolerable apnoea time for an intubation procedure is limited in clinical practice to 1 – 2 minutes. It must be noted that the developing hypercapnia is inevitable, whereas hypoxaemia may be avoided even in prolonged apnoea (e.g. >2 min) with “adaequate” preoxygenation [Duda et al., 1988]. Using de-nitrogenation techniques (breathing pure oxygen for 30 to 60 min) “anaesthetized and curarized normal subjects tolerate total apnoea for up to 55 min” [Siggaard-Andersen, 1974]. According to Mertzlufft et al. (1987), paCO2 does not increase linearly during a short-termed (3 min) apnoea. A fast initial increase in the first minute is followed by a slower increase during the ensuing minutes. This fact inspired previous investigations on arterial and mixed-venous acid-base and oxygen status [Brandt et al., 1987]. It could be demonstrated that, in contrast to paCO2, the development of pvCO2 was almost linear from the onset of apnoea.