Arterial oxygen tension changes in elderly patients undergoing upper gastrointestinal endoscopy. I. Possible causes.

Measurement of arterial oxygen tensions in elderly patients undergoing upper gastrointestinal endoscopy and in a matched control group undergoing colonoscopy showed a slight but significant fall in the PaO2 in both groups following premedication. The initial fall in PaO2 was probably due to the intravenous atropine, diazepam, and meperidine, mainly the latter. This fall of the oxygen tension continued in the gastroscopy group until the instrument was removed, while the controls rapidly returned to basal levels. This persistently reduced PaO2 in the former group is therefore most likely due to the physical presence of the endoscope in the pharynx. To minimize the occurrence of hypoxemia during gastroscopy, narcotics should probably not be used in the premedication of elderly patients. The procedure should be carried out after optimal oxygenation of the patient and be of short duration, and a narrow instrument may be useful in this group.