Objective: To observe the correlation of duration of hypoxia and degree of arrhythmia in patients with and without past history of cardiac disease, in order to provide a warning value supplied by pulse oxygen saturation (SpO2) monitoring for clinical surveillance.
Methods: A prospective study was conducted. Patients with arrhythmia induced solely by hypoxia were included, and they were grouped into cardiac diseases group (n=487) and non-cardiac diseases group (n=13) according to whether or not they had cardiac diseases. Both groups were undergoing mechanical ventilation, and the real time monitoring of electrocardiogram (ECG) and the SpO2 were monitored. The types of arrhythmia and duration and severity of hypoxia were observed. The method of logistic regression was conducted to find the affecting factors of arrhythmia.
Results: There were significant differences in SpO2 (0.82±0.12 vs. 0.50±0.10) and duration of arrhythmia (2.55±1.02 minutes vs. 17.13±1.45 minutes) between the cardiac disease group and the non-cardiac disease group (both P<0.01). The multifactor logistic regression analysis on the affecting factors in patients with cardiac arrhythmia indicated that cough during sputum suction [odds ratio (OR)=3.078, 95% confidence interval (95%CI) 1.756 - 6.235], long duration of tracheal intubation (OR=0.267, 95%CI 0.122 - 0.573), over anesthesia (OR=2.541, 95%CI 1.039 - 6.615), inadequate tidal volume (OR=4.360, 95%CI 2.187 - 9.443), low respiratory frequency (OR=0.297, 95%CI 0.069 - 1.113) were all risk factors of arrhythmia (P<0.05 or P<0.01).
Conclusions: The hypoxemia (lowering of SpO2) is the independent risk factor leading to arrhythmia. Healthy heart can tolerate hypoxia better, and the SpO2 warning value is ≤0.60. Compared with the non-cardiac disease group, patients in cardiac disease group has significantly lower toleration ability against hypoxia, and its SpO2 warning value is lower than 0.95.