Effects of supplemental oxygen on cardiac rhythm during upper gastrointestinal endoscopy: a randomised controlled double blind trial.

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Abstract
To investigate the effects of supplemental oxygen on cardiac rhythm during gastroscopy, 103 patients aged over 60 were randomised to receive either supplemental oxygen or air at 2 litres/minute during the procedure. Pulse rate, blood pressure, oxygen saturation, and a Holter cardiac trace were monitored before, during, and for one hour after the gastroscopy. A wide range of electrocardiographic abnormalities were recorded in both oxygen and air groups, of which ventricular and supraventricular ectopic beats were the most common. There were no significant differences in the rate of occurrence of any clinically important cardiac abnormality either between the oxygen and air groups or between the three monitored periods before, during, and after gastroscopy. There were significantly fewer patients, however, with supraventricular extra systoles when oxygen was given during gastroscopy (p < 0.05). Although supplemental oxygen during gastroscopy significantly improved oxygen saturation (p < 0.001; 95% confidence intervals for the difference between the means: 2.9 to 4.7), there was no correlation between oxygen saturation and any electrocardiographic changes. It is concluded that electrocardiographic abnormalities are common in patients over 60, but this study found no evidence that they are induced by gastroscopy. Supplemental oxygen increases oxygen saturation but does not reduce the incidence of clinically important cardiac arrhythmias.