LACK OF EFFECT OF INHALED MORPHINE ON EXERCISE-INDUCED BREATHLESSNESSIN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background - Inhaled nebulised morphine may reduce breathlessness in p atients with lung disease, although the results of controlled trials a re conflicting. A direct action of morphine on the lung has been postu lated. This study aimed to investigate whether nebulised morphine redu ced exercise-induced breathlessness in patients with chronic obstructi ve pulmonary disease (COPD) and to determine if this was a local pulmo nary effect or occurred after systemic morphine absorption. Methods - A double blind, randomised, crossover study was performed in 12 men wi th COPD to compare the effects of nebulised morphine (10 and 25 mg), e quivalent intravenous doses (1 and 2.5 mg), and placebo. Breathlessnes s (visual analogue scale), ventilation, gas exchange, and exercise end urance were measured during graded bicycle exercise. Results - None of the treatments altered breathlessness, ventilation, or gas exchange a t rest or at any time during exercise, and exercise endurance was unaf fected. At peak exercise mean (95% CI) changes from placebo in ventila tion were -0.8 (-0.57 to 1.1) 1/min and -0.4 (-2.8 to 2.0) 1/min for t he highest intravenous and nebulised doses, respectively. For breathle ssness equivalent values were +2 (-5 to 9) and +1 (-9 to II) mm. The s tudy was of sufficient power that it is unlikely that a clinically imp ortant effect was missed. Conclusions - Nebulised morphine in these do ses has no effect on exercise-induced breathlessness. These findings d o not support the hypothesis that intrapulmonary opiates modulate the sensation of breathlessness in patients with COPD.