2001 OPEN FORUM Abstracts
EVALUATION OF A NEWDEMAND OXYGEN CONSERVATION DEVICE IN PATIENTS WITH CHRONIC LUNG DISEASES ATREST AND WITH EXERCISE
Trina Limberg, BS, RRT,Andrew Ries, M.D., M.P.H., Roseann Myers, BS, RN, Lela Prewitt. University ofCalifornia San Diego Medical Center, San Diego CA
Background: Oxygen therapyis an important treatment and has been shown to improve survival in hypoxemicCOPD patients. Due to potential cost savings and portability benefits, demandoxygen systems have increased in use. Previous studies have demonstrated mixedresults of conservation systems during exercise and with activities of dailyliving. We sought to evaluate use of an O2XPRESS pneumatic deviceby comparing it to continuous flow during exercise in pulmonary rehabilitationprogram graduates.
Method: Twenty-one O2dependent patients (18 COPD, 3 Restricted lung disease) with documentedhypoxemia on room air (SaO2 <88% or PaO2 55mmHg) werestudied. All were receiving long term oxygen therapy. During the one visit testing,patients were provided with either a continuous flow nasal cannula or the SalterLabs demand oxygen conserving device (DOCD). Vital signs and oxygen saturationswere assessed at rest and during exercise. While seated, subjects received sequentialflow rates of 1, 2, 3 and 4 LPM of supplemental oxygen, once with continuousflow and once with the DOCD for 5 minute periods. Oximetry was recorded duringthe final 15 seconds of each five minute interval. Then subjects were testedwhile walking on the treadmill based on workload prescriptions determined duringthe previously completed pulmonary rehabilitation program. At UCSD, exercisetraining targets are set to approximate maximum symptom-limited levels reachedduring an initial incremental exercise test. In obstructive patients, supplementaloxygen was delivered sequentially, at 4, 3, 2, and 1 liters per minute duringtreadmill exercise for 3 minutes each. Following each change in flow rate subjectswere required to rest for 10 minutes. Restrictive patients received higher flowrates, sequentially, at 6, 4, 2 and 1 LPM. Ratings of perceived breathlessnessand muscle fatigue were also obtained via the Borg scale at the end of exercise.Assessments were terminated if oxygen saturations fell below 85%. COPD patientswere analyzed in a group while the restrictive patients were studied individually.Repeated measures analysis of variance was used to compare oxygen saturationwith the two methods of continuous flow via nasal cannula and the Salter LabsDOCD. Separate analysis was performed for rest and exercise with paired-t tests.
Results: For COPD patients,results showed there was no significant difference in SaO2 at comparableflow rates between the two devices, although with exercise SaO2 wassignificantly (p< 0.05) higher at the lowest flow rate with the DOCD (meanSaO2 91.5% versus 90.2%). SaO2 was higher for the DOCDin 10 patients (range 1-5%), higher for the nasal cannula in 4 (range 1-2%),and equal in 3 subjects. One subject did not exercise on 1 lpm due to a lowSaO2. Overall, there was no significant difference in ratings ofmuscle fatigue or breathlessness. Individual results for restrictive patientsshowed that at rest, the DOCD appeared to produce higher SaO2 inone of three patients. During exercise there did not appear to be any consistentdifference between continuous flow and use of the Salter Labs DCOD.
Conclusions: This pilot studydemonstrated that the Salter Labs DOCD was comparable to continuous flow bynasal cannula at rest and during exercise in patients with chronic lung disease.It is important to note treadmill speeds in some patients were as high as 2.8mph. Previous studies appear to have been conducted at much lower workloads.Since respiratory rates increase with higher workloads it is imperative thatpatients using conservation devices be assessed with exertion.
This study was supported by SalterLabs.