Should all patients undergoing cardiac catheterization or percutaneous transluminal coronary angioplasty receive oxygen?

BACKGROUND Supplemental oxygen is routinely administered to patients with acute coronary syndromes. The risk of significant morbidity during cardiac catheterization or coronary angioplasty has been well described; however, to our knowledge, the need for routine oxygen supplementation in these patients has not been investigated. METHODS In phase 1, we prospectively studied 142 patients undergoing diagnostic cardiac catheterization (n = 94) or percutaneous transluminal coronary angioplasty (PTCA) (n = 48) to determine the incidence of procedure-related hypoxemia (pulse oximetry derived oxygen saturation [SpO2] < 90 percent of > 1 min duration) while breathing room air (RA). In phase 2, 134 patients undergoing diagnostic cardiac catheterization (n = 78) or PTCA (n = 56) were randomly allocated to breathe either RA or supplemental oxygen (O2, 6 L/min by nasal cannula) to determine the effect of oxygen administration on procedure-related hypoxemia. Oximetry results were compared with pertinent clinical and procedural data that might predispose patients to develop hypoxemia. RESULTS Phase 1--Moderate to severe hypoxemia occurred in 36 percent (34/94) of patients undergoing diagnostic catheterization and in 56 percent (27/48) of patients undergoing PTCA. In the diagnostic catheterization group, there were a total of 25 episodes of moderate hypoxemia (SpO2 85 to 89 percent) lasting 4.0 +/- 4.3 min and 11 episodes of severe hypoxemia (SpO2 < 85 percent) of greater duration, 11.7 +/- 7.5 min (p < 0.008). In the PTCA group, there were 24 episodes of moderate hypoxemia and six episodes of severe hypoxemia lasting 4.8 +/- 4.3 min and 8.2 +/- 3.8 min, respectively. A history of chronic lung disease was associated with hypoxemia (p < 0.05) in the diagnostic group. In addition, 11 patients undergoing diagnostic catheterization who had baseline SpO2 < 95 percent all developed hypoxemia during the procedure. In this subset of patients, there was a higher incidence of cigarette smoking (p = 0.02), chronic lung disease (p = 0.04), higher left ventricular diastolic pressure (p = 0.02), and lower ejection fraction (p = 0.002) when compared with the 83 remaining patients undergoing diagnostic catheterization with a baseline SpO2 > 95 percent. Phase 2--Oxygen therapy was associated with a reduction in the incidence of hypoxemia from 42 percent to 5 percent (RA vs O2, p < 0.001) in the diagnostic catheterization group and 39 percent to 11 percent (RA vs O2, p < 0.03) in the PTCA group. CONCLUSIONS Significant hypoxemia is a common finding among patients undergoing cardiac catheterization or angioplasty despite the absence of predictive risk factors. Severe and prolonged hypoxemic episodes occurred in 10 percent (14/142, phase 1) of patients breathing room air. Patients undergoing diagnostic catheterization with history of chronic lung disease or a baseline SpO2 < 95 percent are at high risk to develop moderate-severe hypoxemia. Oxygen therapy significantly reduced the incidence and severity of procedure-induced hypoxemia in both groups. Our data support the use of both pulse oximetry and oxygen supplementation in patients undergoing cardiac catheterization and PTCA.