Am. J. Respir. Crit. Care Med., Vol 152, No. 6, Dec 1995, 1940-1945.
Low-dose nebulized morphine does not improve exercise in interstitial lung disease
AO Harris-Eze, G Sridhar, RE Clemens, TA Zintel, CG Gallagher and DD Marciniuk
Division of Respiratory Medicine, University of Saskatchewan, Saskatoon, Canada.
Recent reports have suggested that low-dose nebulized morphine may improve
exercise tolerance in patients with interstitial lung disease (ILD) by
acting on peripheral opioid-sensitive pulmonary receptors. We therefore
examined whether the administration of low-dose nebulized morphine would
influence dyspnea or the breathing pattern during exercise of subjects with
ILD and improve their exercise performance. Each of six subjects with ILD
underwent three maximal incremental cycle ergometer tests, each test
separated from the last by at least 3 d. Each exercise test was similar
except that 30 min before exercise, the subjects received nebulized saline
(control), morphine 2.5 mg, or morphine 5.0 mg, respectively, in
double-blinded fashion. No significant differences were noted in exercise
duration, maximal workload, or sense of dyspnea at the end of exercise in
the control test and the tests with either morphine 2.5 mg or morphine 5.0
mg. Nor were significant differences noted in resting, submaximal, or end-
exercise measurements of oxygen uptake (VO2), carbon dioxide output (VCO2),
end-tidal CO2 (PETCO2), oxygen saturation (SaO2), minute ventilation (VI),
respiratory frequency (f), tidal volume (VT), or heart rate (HR) in the
three tests. Low-dose nebulized morphine did not alter the subjects'
breathing pattern or affect the relationship between dyspnea and
ventilation during exercise. No significant side effects were noted. The
administration of low-dose nebulized morphine to subjects with ILD neither
relieves their dyspnea during exercise nor improves their maximal exercise
performance.
