Low dose nebulised morphine may relieve dyspnoea through a direct effect on lung afferent nerves. To-study this further 11 adult patients with advanced chronic lung disease (FEV, range 0-4-1.4 1), whose exercise endurance was limited by dyspnoea, were entered into a double blind, randomised, crossover study in which low dose morphine or a placebo was inhaled. The effects were assessed by an endurance exercise test at 80% of maximum work load. One hour after a control endurance test patients inhaled 5 ml of morphine 1 mg/ml or isotonic saline for 12 minutes from a jet nebuliser. An endurance exercise test was repeated 15 minutes later and change in endurance time recorded. The two endurance tests were repeated on a separate day, before and after inhalation of the alternative solution. In all tests 100% oxygen was inhaled from a demand valve. The mean (SD) increase in endurance time was significantly greater after the subjects had inhaled morphine (64-6 (115) s, 35%) than after placebo (8-9 (55) s, 0-8%; p < 0 01). The mean dose of morphine nebulised was 1 7 (0-66) mg, giving a mean inhaled dose ofabout 0-6 mg, on the assumption of30% retention of the nebulised dose by each patient. No side effects were reported. Possibly small amounts ofmorphine delivered to the lungs act directly on lung afferent nerves to reduce dyspnoea.
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