Effekte der zusätzlichen Sauerstoffzufuhr über ein Demandsystem im Vergleich zum Dauerflusssystem bei körperlicher Belastung hypoxämischer COPD-Patienten

Chronic Obstructive Pulmonary Disease (COPD) is a preventable and treatable pulmonary disease which is associated with not fully reversible, progressive respiratory symptoms, and airflow limitation. It is one of the leading causes of morbidity and mortality and is projected to be the third leading cause of death by 2020. A premature therapeutic treatment is essential, as it alleviates symptoms, improves the quality of life, and slows down the progression of the disease. Long-term oxygen therapy is a recommended therapy option for hypoxemic COPD patients and improves the chances of survival significantly. Patients with chronic hypoxemia and chronic respiratory insufficiency of stage IV benefit from 16 – 24 hours long-term oxygen therapy per day as it increases lifespan and improves exercise intensity and duration. In clinical practice, two different oxygen-delivery systems are used for long-term oxygen therapy: a continuous-oxygen-flow system and a demand-oxygen-delivery system. Both systems are small, handy, portable, and allow good mobility for the patients. The continuous-oxygen-flow system is associated with higher consumption of oxygen because oxygen is supplied continuously during both inspiration and expiration. The demand-oxygen-delivery system delivers a bolus of oxygen during early inspiration and needs to be triggered by the patient’s inspiratory effort, but no oxygen is supplied during expiration. There is, however, a lack of evidence with respect to which oxygen-delivery system is most suitable during exercise. In fact, there are various studies that have already examined the effect of a continuous-oxygen-flow system during exercise. However, there is no study that compared the effects of the continuous-oxygen-flow system and the demand-oxygen-delivery system using a standardized, externally paced walk-test procedure in a sufficiently large sample of hypoxemic patients. This is the first study which examines the effects of supplemental oxygen delivery with a demand-oxygen-delivery system compared to a continuous-oxygen-flow system during a standardized, externally paced walk-test procedure in form of an Endurance Shuttle Walking Test at isotime in a large sample of hypoxemic COPD patients. Compared to the 6-minute walk test the Endurance Shuttle Walking Test provides a better standardization, is well validated, and offers high reliability for measuring endurance-walk capacity in COPD patients. It is therefore comparable to the intensity of typical daily activities. In total, 77 hypoxemic COPD patients with long-term oxygen therapy were enrolled in the monocentric, randomized, single-blinded, controlled crossover trial that was conducted during a three-week inpatient pulmonary rehabilitation program at the Schön Klinik Berchtesgadener Land in Schönau am Königssee, Germany. Out of the initial 77 participants, 70 hypoxemic COPD patients were included in the analysis. For this study, an Incremental Shuttle Walking Test was initially performed by the patients. At least 24 hours thereafter, patients participated in two additional walking tests (Endurance Shuttle Walking Test) with two oxygen-delivery systems in randomized order. There was a wash-out phase of 24 hours between these two Endurance Shuttle Walking Tests. The primary outcome was the oxygen saturation during the exercise at isotime. Secondary outcomes were transcutaneous partial pressure of carbon dioxide, breathing frequency, and pulse rate, as well as dyspnea and walking distance. Furthermore, patients were analyzed with respect to secondary target parameters (gender, BMI, and use of a rollator) in order to identify potential predictors for the use of a specific oxygen-delivery system. The results of this study show that under these standardized workload conditions, there are neither statistically significant nor clinically relevant differences between the continuous-oxygen-flow system and the demand-oxygen-delivery system concerning oxygen saturation in hypoxemic COPD patients during the entire exercise. A separate subgroup analysis merely reveals a general trend in which more patients benefited from oxygen saturation using the continuous-oxygen-flow system since some of these patients had a significantly higher oxygen saturation (up to 13 %) and the difference in oxygen saturation between the continuous-oxygen-flow system and the demand-oxygen-delivery system reached the required clinical-relevance level of 4 %. However, the majority of participants in this subgroup analysis did not show any clinically relevant difference in oxygen saturation at isotime. Additionally, the results of the analysis identifying potential predictors did not show any statistically significant differences between the continuous-oxygen-flow system and the demand-oxygen-delivery system with respect to oxygen saturation at isotime. In summary, no clinically relevant differences in primary and secondary outcomes could be identified when comparing the scrutinized oxygen-delivery systems among hypoxemic COPD patients, and thus both may be considered equivalent with respect to the physiological impact. From a practical point of view, the demand-oxygen-delivery system used in this study offers a bigger advantage compared to the continuous-oxygen-flow system as it is smaller and lighter and has a longer operating life. Based on the results analyzed in this present study, hypoxemic COPD patients are advised to individually adapt to one of these oxygen-delivery systems in order to evaluate and configure the type of oxygen delivery as well as the oxygen-flow adjustment for each patient. Only this way efficiency and the intended levels of oxygen saturation can be achieved. Based on this study, additional, comprehensive comparisons with other existing portable oxygen-delivery systems should be investigated under standardized and uniform workload conditions. Here, not only the oxygen saturation, but also other outcomes should be considered and analyzed at rest, during exercise, and during sleep.