The effect of upper gastrointestinal endoscopy on arterial O2 tension in smokers and nonsmokers with and without premedication.

Fiberoptic upper gastrointestinal endoscopy has become an accepted procedure with recognized and acceptable complication rates. Recently, significant hypoxemia during upper gastrointestinal endoscopy has been identified. This report evaluates changes in arterial blood gases and investigates the effects of drugs, smoking, and length of procedure. Upper gastrointestinal endoscopy was performed on 60 patients--15 patients in four different groups. Group I and II were smokers and nonsmokers who received sedation; groups III and IV were smokers and nonsmokers who received no sedation. A significant drop in PaO2 was noted in each group. Sedation, length of procedure, or smoking did not affect the PaO2 levels significantly. No significant change in PaCO2 was noted in any of the four groups. A V/Q mismatch related to vasospasm and/or bronchospasm is proposed as the main reason for the hypoxemia.