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Attenuation of induced bronchoconstriction in healthy subjects: effects of breathing depth

¹Divisione di Pneumologia Riabilitativa, Fondazione Salvatore Maugeri, Cassano Murge; ²Centro di Fisiopatologia Respiratoria e di Studio della Dispnea, Azienda Ospedaliera S. Croce e Carle, Cuneo; and ³Dipartimento di Medicina Interna, Università di Genova, Genova, Italy

Submitted 21 July 2004 ; accepted in final form 28 September 2004

The effects of breathing depth in attenuating induced bronchoconstriction were studied in 12 healthy subjects. On four separate, randomized occasions, the depth of a series of five breaths taken soon (1 min) after methacholine (MCh) inhalation was varied from spontaneous tidal volume to lung volumes terminating at 80, 90, and 100% of total lung capacity (TLC). Partial forced expiratory flow at 40% of control forced vital capacity (_part) and residual volume (RV) were measured at control and again at 2, 7, and 11 min after MCh. The decrease in _part and the increase in RV were significantly less when the depth of the five-breath series was progressively increased (P < 0.001), with a linear relationship. The attenuating effects of deep breaths of any amplitude were significantly greater on RV than _part (P < 0.01) and lasted as long as 11 min, despite a slight decrease with time when the end-inspiratory lung volume was 100% of TLC. In conclusion, in healthy subjects exposed to MCh, a series of breaths of different depth up to TLC caused a progressive and sustained attenuation of bronchoconstriction. The effects of the depth of the five-breath series were more evident on the RV than on _part, likely due to the different mechanisms that regulate airway closure and expiratory flow limitation.

deep breath; airflow obstruction; partial forced expiratory flow; residual volume

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