Abstract
BACKGROUND: Arterial oxygen desaturation frequently occurs in patients with COPD during daily activities at home. Oxygen flow is usually set at fixed and low rates for ambulatory patients. We evaluated an innovative closed-loop system (FreeO2) that automatically adjusts the oxygen flow to the patient's needs in subjects with COPD during walking followed by recovery time, such as during ambulatory conditions.
METHODS: Patients with COPD who exhibited oxygen desaturation on exertion were included in the study. Subjects performed endurance shuttle walk tests followed by 10 min of recovery. The tests were conducted in a random order and in crossover with the 3 following conditions: subjects breathing (1) air at 2 L/min, (2) oxygen at 2 L/min, or (3) FreeO2 (variable oxygen flow). SpO2, pulse rate, PETCO2, breathing frequency, and oxygen flow were continuously recorded during the 3 conditions. The primary outcome was the percentage of time within the SpO2 target of 92–96%. Secondary outcomes included the endurance shuttle walk test time and distance.
RESULTS: Sixteen subjects with COPD were recruited. The percentage of time with SpO2 in the target range (92–96%) was higher while using the FreeO2, and time with severe oxygen desaturation (SpO2 <88%) was lower with FreeO2 in comparison with constant-flow oxygen and air testing conditions (0.6% vs 23.9% vs 52.2%, P < .001). In comparison with air, walking distance was increased by 35% with oxygen (P = .045) and by 63% with FreeO2 (P < .001). The walking distance was increased by 17% with FreeO2 in comparison with constant oxygen, but the difference was not statistically significant (P = .22).
CONCLUSIONS: Automatic titration of oxygen flow during walking to maintain oxygen saturation in a specified range improves oxygenation and may improve exercise tolerance during daily activity, such as walking, in patients with COPD in comparison with room air and fixed oxygen administration. (ClinicalTrials.gov registration: NCT02150434.)
Footnotes
- Correspondence: François Lellouche MD PhD, Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, 2725 Chemin Sainte-Foy, Ville de Québec, Québec G1V 4G5, Canada. E-mail: francois.lellouche{at}criucpq.ulaval.ca.
This work was supported by the Canadian Foundation for Innovation (Leaders Opportunity Funds) and Fonds de Recherche en Santé du Québec (FRSQ). Our research laboratory has been funded by the Canadian Foundation for Innovation (Leaders Opportunity Funds) to develop automated systems for respiratory support. Part of this funding was used to make FreeO2 prototypes. François Maltais holds a GSK/Canadian Institutes of Health Research (CIHR) research chair on COPD at Laval University. Drs Lellouche and L'Her are co-inventors of the FreeO2 system and are co-founders of a research and development company (Oxynov) to develop automated systems for respiratory support. No support from this company was provided for the study. The other authors have disclosed no conflicts of interest.
Supplementary material related to this paper is available at http://www.rcjournal.com.
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