Fog-induced respiratory responses are attenuated by nedocromil sodium in humans

Fog inhalation induces cough and bronchoconstriction in patients with asthm a, but only cough in normal subjects; whether it also influences the patter n of breathing is unclear. Nedocromil sodium (NCS) inhibits the cough respo nse to inhalation of several pharmacological agents but its effects on fog- induced cough and changes in the pattern of breathing are unknown. We evalu ated the effects of no drug, placebo, and 4- and 8-mg NCS administration on the cough threshold and changes in the pattern of breathing during fog inh alation in 14 healthy subjects. Measurements of tidal volume (VT), duration of inspiratory and expiratory times (TI and TE, respectively), total durat ion of the respiratory cycle (TT), mean inspiratory flow (VT/TI), duty cycl e (TI/TT), respiratory frequency (f, 60/Tr), and inspiratory minute Ventila tion ((V) over dot) were obtained by inductive plethysmography. Median coug h threshold values were unaffected by placebo, but were increased (p < 0.01 ) by both NCS doses. In no-drug and placebo trials, inhalation of the thres hold fog concentration caused increases in both VT/TI and (V)over dot (p al ways < 0.05) due to selective increases (p < 0.01) in VT. These changes wer e markedly attenuated by both NCS doses administration. Thus, fog induces c oughing and increases in VT, VT/ TI, and (V) over dot in healthy subjects; NCS possesses antitussive effects and attenuates fog-induced changes in the pattern of breathing, possibly through inhibition of rapidly adapting "irr itant" receptors.