NO EFFECT OF OXYGEN-THERAPY ON MYOCARDIAL-ISCHEMIA DURING GASTROSCOPY

Background: Myocardial ischaemia (defined as an ST-segment depression on EGG) may occur during upper gastrointestinal endoscopy, but the mec hanism is still unknown. The aim of our study was to evaluate the effe ct of oxygen therapy and tachycardia on the occurrence of ST-segment d epression during routine diagnostic esophagogastroduodenoscopy. Method s: Eighty-nine consecutive patients were randomized to receive either oxygen (21/min by nasal prongs) or nothing during endoscopy, in which arterial oxygen saturation was measured by continuous pulse oximetry, and ECG was measured continuously with a Holter tape recorder. Results : A total of 28 patients (12 receiving oxygen) developed ST-segment de pression (>0.1 mV) during endoscopy. In 22 patients (12 receiving oxyg en) ST depression was related to tachycardia, and in 5 of these (none receiving oxygen) simultaneous episodic hypoxaemia was present during the event. Thus, in every case of ST depression related to episodic hy poxaemia there was simultaneous tachycardia. In six patients developin g ST depression during endoscopy we did not find tachycardia or hypoxa emia. All patients had increased heart rate during endoscopy compared with preendoscopy levels, and 63 patients (29 receiving oxygen) develo ped tachycardia during the procedure (rate >100 min(-1)). Conclusions: Oxygen therapy had no significant effect on the occurrence of ST-segm ent depression during upper gastrointestinal endoscopy. The results su ggest that tachycardia is more important than hypoxaemia in the pathog enesis of ST depression during gastroscopy.