Melatonin Administration Acutely Decreases the Diffusing Capacity of Carbon Monoxide in Human Lungs

Abstract

Background: Most physiological measurements of the pulmonary diffusing capacity use carbon monoxide (CO) as a tracer gas. Similar to CO, melatonin binds the hemoglobin in the blood. Objective: The present study was designed to assess the effect of exogenous melatonin administration on pulmonary functions including diffusing capacity for carbon monoxide (DL_CO) in healthy subjects. Methods: The study was performed in a randomized, double-blind, placebo-controlled manner. DL_CO was measured in 22 healthy male volunteers (age 18–25 years) who were randomized to melatonin (n = 11) and placebo administration (n = 11). At baseline, DL_CO, alveolar volume (V_A) and other spirometric parameters such as forced expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), peak expiratory flow (PEF) and maximal voluntary ventilation (MVV) were measured. DL_CO was then corrected for the hemoglobin concentration. Measurements were repeated in a double-blind fashion 60 min after the administration of melatonin (1 mg) or placebo. Results: DL_CO was significantly decreased (39.31 ± 4.75 vs. 34.82 ± 6.18 ml/min/mm Hg) 60 min after the melatonin administration (p = 0.01), while FEV₁, FVC, FEV₁/FVC, PEF and MVV values did not demonstrate significant differences. Placebo administration did not result in significant alteration in any of these parameters. Conclusions: In healthy subjects, oral administration of melatonin acutely influences the DL_CO without affecting other pulmonary function test results. We conclude that melatonin may have a reducing effect on the DL_CO in the lungs.