• Bruno Mahut, Aurore Caumont-Prim, Laurent Plantier, Karine Gillet-Juvin, Etienne Callens, Olivier Sanchez, Brigitte Chevalier-Bidaud, Plamen Bokov, and Christophe Delclaux.
• Assistance Publique - Hôpitaux de Paris (AP-HP), Hôpital Européen Georges Pompidou, Service de Physiologie - Clinique de la Dyspnée, F-75015 Paris, France.
• Int J Chron Obstruct Pulmon Dis. 2012 Jan 1; 7: 165-71.

BackgroundThe aims of the study were: (1) to compare numerical parameters of specific airway resistance (total, sRaw(tot), effective, sRaw(eff) and at 0.5 L · s(-1), sRaw(0.5)) and indices obtained from the forced oscillation technique (FOT: resistance extrapolated at 0 Hz [Rrs(0 Hz)], mean resistance [Rrs(mean)], and resistance/frequency slope [Rrs(slope)]) and (2) to assess their relationships with dyspnea in chronic obstructive pulmonary disease (COPD).MethodsA specific statistical approach, principal component analysis that also allows graphic representation of all correlations between functional parameters was used. A total of 108 patients (mean ± SD age: 65 ± 9 years, 31 women; GOLD stages: I, 14; II, 47; III, 39 and IV, 8) underwent spirometry, body plethysmography, FOT, and Medical Research Council (MRC) scale assessments.ResultsPrincipal component analysis determined that the functional parameters were described by three independent dimensions (airway caliber, lung volumes and their combination, specific resistance) and that resistance parameters of the two techniques were not equivalent, obviously. Correlative analyses further showed that Raw(tot) and Raw(eff) (and their specific resistances) can be considered as equivalent and correlated with indices that are considered to explore peripheral airways (residual volume (RV), RV/ total lung capacity (TLC), Rrs(slope)), while Rrs(mean) and Raw(0.5) explored more central airways. Only specific resistances taking into account the specific resistance loop area (sRaw(tot) and sRaw(eff)) and Rrs(slope) were statistically linked to dyspnea.ConclusionParameters obtained from both body plethysmography and FOT can explore peripheral airways, and some of these parameters (sRaw(tot), sRaw(eff,) and Rrs(slope)) are linked to activity-related dyspnea in moderate to severe COPD patients.

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