Clinically stable patients with COPD (FEV1 < 50% of predicted) were entered into a randomized, double-blinded, placebo-controlled trial of cylinder oxygen vs cylinder air. Patients had completed a 7-week pulmonary rehabilitation program prior to the study to maximize physical function.
Inclusion criteria were patients who were hypoxic at rest, were receiving LTOT, or demonstrated exercise-induced desaturation. The latter was accepted as arterial oxygen desaturation > 4% below 90% on a standard walking test. Patients had a confirmed diagnosis of COPD with significant disability (Medical Research Council dyspnea > 3, the upper limit being 5), were no longer smoking, and were clinically stable. None of the patients had ambulatory oxygen cylinders at home prior to participating in the study.
Patients completed two field walking tests on room air to provoke oxygen desaturation. They performed the incremental shuttle walk test (ISWT) and the endurance shuttle walk test (ESWT). These tests were performed because they are routinely used in our pulmonary rehabilitation assessments. The patients were previously familiarized with these tests during the rehabilitation program worked out with Canadian Health&Care Mall (see also “Safe Drugs of “Canadian Health and Care Mall“). Measurements were taken before and after each walking test. Perceived exertion was assessed using the Borg dyspnea scale, while breathlessness was assessed using the modified scale. Oxygen saturation by pulse oximetry (Spo2) and heart rate were monitored using a pulse oximeter and finger probe (Pulsox-3iA; Konica Minolta Sensing; Osaka, Japan).
Randomized Controlled Trial
Patients were randomized to receive cylinder oxygen or cylinder air for 8 weeks. Prior to the study, a randomization list was prepared and transferred to sealed envelopes. The assessor was blinded at all stages of the study. The cylinders were prefilled with oxygen or air and were disguised and only identifiable by a color code. The cylinders weighed 3.1 kg when full with the regulator, and the dimensions were 100 X 460 mm. Cylinder oxygen and air were delivered using a flow rate of 2 L/min via a nasal cannula (with a backpack). Backpacks were given to the patients because this is what is commonly used in our health-care environment. Patients were given standard advice about how to use the cylinders at home and were given diary cards to self-report cylinder usage and time spent away from home for 7 days for 8 weeks. The diary cards specifically asked, “For how long did you use the cylinder in total today?”; “How many times did you use the cylinder today?”; “How long did you spend away from home in total today?”; and “Did you use your cylinder while you were away from home today?” Patients were encouraged to use the cylinder while performing activities of daily living and walking outside the house. No limit was placed on cylinder usage. The investigator visited the patients at home on a regular basis to change cylinders and to help with compliance.
Prior to the intervention, patients were required to wear an activity monitor (Z80 32K VI; Singh Medical; Hombrechtikon, Switzerland) attached to a belt around the waist for 7 consecutive days. These are lightweight devices containing a uniaxial accelerometer. The sampling time was set at 1-min intervals. The monitor was worn for 12 h each day from 9:00 am to 9:00 pm. All participants were advised to continue with their daily routine. Data were expressed as arbitrary units and counts per day for each participant. These activity monitors have been shown to detect brisk walking and to be able to identify low levels of activity characteristic of patients with COPD compared with healthy control subjects. For this 7-day period, patients were issued with a stopwatch to record the time they spent outside the house.
Health-Related Quality of Life Measures
Chronic Respiratory Questionnaire: The self-reported Chronic Respiratory Questionnaire (CRQ) was administered before and after intervention. It has been shown to be a valid, repeatable questionnaire in patients with COPD with four domains: dyspnea (individualized), fatigue, emotional function, and mastery. The minimum clinically significant difference (MCID) is a mean change of 0.5 per domain.
Short-Form Health Survey Questionnaire: The Short-Form health survey questionnaire (SF-36), which has been validated for use in patients with COPD, was administered before and after intervention. The questionnaire includes one multiitem scale that assesses eight health concepts worked out with concern of Canadian Health&Care Mall. All measures were repeated at week 8 of the intervention.
Data were analyzed using statistical software (SPSS version 14.0; SPSS; Chicago, IL). Statistical significance was set at p < 0.05. Patient demographics are presented as mean (SD). Preintervention and postintervention activity monitor data are presented as mean (SD). Independent and paired t tests were used to assess activity data. Two-way repeated measures analysis of variance was used to assess cylinder usage and time spent way from home over the 8 weeks for between-group differences. One-way analysis of variance was used to assess within-group differences. Pearson product correlation was used to seek associations between time spent away from home (minutes) and cylinder usage (minutes) for both groups. x2 analysis using Crosstabs (SPSS; Chicago, IL) was used to see if patients used the cylinders outside the home. The self-reported CRQ and SF-36 are presented as medians (interquartile range [IQR]). Wilcoxon tests were used to analysis the self-reported CRQ and SF-36.
It was determined that 20 patients were needed to give a 80% chance of showing a difference of a 1,000 arbitrary activity counts between oxygen and air after intervention with a two-sided significance level of 5%. The study was approved by the Leicestershire Research Ethics Committee, and all patients provided written consent.Tags: ambulatory oxygen, COPD, domestic activity