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This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 105/5/1477    most recent 00108.2008v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Muñoz, P. A. Articles by Rodríguez-Roisin, R. Search for Related Content PubMed PubMed Citation Articles by Muñoz, P. A. Articles by Rodríguez-Roisin, R.

Pulmonary gas exchange response to exercise- and mannitol-induced bronchoconstriction in mild asthma

¹Servei de Pneumologia, Institut del Tórax, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Ciber Enfermedades Respiratorias, Universitat de Barcelona, Barcelona, Spain; and ²Department of Respiratory Medicine, Royal Prince Alfred Hospital, Camperdown, New South Wales, Australia

Submitted 31 January 2008 ; accepted in final form 22 August 2008

Both exercise (EIB) and mannitol challenges were performed in asthmatic patients to assess and compare their pulmonary gas exchange responses for an equivalent degree of bronchoconstriction. In 11 subjects with EIB [27 ± 4 (SD) yr; forced expiratory volume in 1 s (FEV₁), 86 ± 8% predicted], ventilation-perfusion (A/) distributions (using multiple inert gas elimination technique) were measured 5, 15, and 45 min after cycling exercise (FEV₁ fall, 35 ± 12%) and after mannitol (33 ± 10%), 1 wk apart. Five minutes after EIB, minute ventilation (E; by 123 ± 60%), cardiac output (T, by 48 ± 29%), and oxygen uptake (O₂; by 54 ± 25%) increased, whereas arterial PO₂ (Pa_O2; by 14 ± 11 Torr) decreased due to moderate A/ imbalance, assessed by increases in dispersions of pulmonary blood flow (log SD; by 0.53 ± 0.16) and alveolar ventilation (log SD; by 0.28 ± 0.15) (dimensionless) (P < 0.01 each). In contrast, for an equivalent degree of bronchoconstriction and minor increases in E, T, and O₂, mannitol decreased Pa_O2 more intensely (by 24 ± 9 Torr) despite fewer disturbances in log SD (by 0.27 ± 0.12). Notwithstanding, mannitol-induced increase in log SD at 5 min (by 0.35 ± 0.15) was similar to that observed during EIB, as was the slow recovery in log SD and high A/ ratio areas, at variance with the faster recovery of log SD and low A/ ratio areas. In asthmatic individuals, EIB provokes more A/ imbalance but less hypoxemia than mannitol, primarily due to postexercise increases in E and T benefiting Pa_O2. A/ inequalities during both challenges most likely reflect uneven airway narrowing and blood flow redistribution generating distinctive A/ patterns, including the development of areas with low and high A/ ratios.

bronchial provocation; exercise; mannitol; multiple inert gas elimination technique; pulmonary gas exchange