Effects and Its Factors on Exercise Capacity of Oxygen Conserving Devices in COPD Patients

Abstract

Background: The newly developed oxygen conserving devices SmartDoze, is designed to automatically adjust the oxygen pulse dose according to the respiration rate and is automatically reduced the flow at rest. Therefore, we compared the conventional oxygen conserving devices with SmartDoze in the 6-minute walk (6MWD) test, and examined the influence on exercise tolerance and its factors. Methods: The subjects were 29 patients with COPD (mean age: 75.5 ± 5.6 y). The pulmonary function and respiratory muscle strength of the study patients were as follows (FVC: 2.68 ± 0.77 L, FEV 1:1.13 ± 0.55, FEV 1%: 41.7 ± 17.0%, PI max: 64.2 ± 21.4 cm H₂O, PE max: 70.8 ± 22.6 cm H₂O). 6MWD test was conducted using both oxygen synchronizers, and transcutaneous oxygen saturation, breathing frequency, heart rate, dyspnea and lower limb muscle fatigue by Borg scale, and blood pressure were compared before and after. Among the factors, we examined what influences walking with oxygen conserving device. This research is conducted after obtaining approval from the Kyorin University Ethics Review Committee. Results: The 6MWD by the conventional oxygen conserving devices was 366.2 ± 130.2 m, and the 6MWD when using SmartDoze was significantly improved to 378.3 ± 96.0 m (P < .05). In addition, after 6 minutes of walking, dyspnea showed a significantly lower value of 4.7 ± 2.6 for Smart Doze, compared with 5.6 ± 2.8 for the conventional oxygen conserving device (P < .01). Similar results were obtained after 3 minutes. Furthermore, it was found that Smart Doze showed a quick recovery of 1.0 ± 1.5 for Smart Doze, as compared with 1.4 ± 1.6 for leg muscle fatigue at 3 minutes after the end (P < .001). As a result of the multiple regression analysis, the factors that affect the 6MWD were lower extremity muscle fatigue and expiratory muscle strength at rest with conventional oxygen conserving devices, dyspnea and inspiratory muscle strength with SmartDoze. Conclusions: The new oxygen synchronizer improves exercise capacity, oxygenation and dyspnea by providing an amount of oxygen synchronized to the increase in working respiration rate. Lower extremity muscle is the most important factor that affects gait by using conventional oxygen conserving devices, dyspnea is the most important factor in SmartDoze, and it is recognized that recovery of dyspnea after walking is quick in SmartDoze.