Relationships between respiratory and airway resistances and activity-related dyspnea in patients with chronic obstructive pulmonary disease

Abstract

Bruno Mahut1,2, Aurore Caumont-Prim3,4, Laurent Plantier1,5, Karine Gillet-Juvin1,6, Etienne Callens1, Olivier Sanchez5,6, Brigitte Chevalier-Bidaud3, Plamen Bokov1, Christophe Delclaux1,5,71Assistance Publique – Hôpitaux de Paris (AP-HP), Hôpital Européen Georges Pompidou, Service de Physiologie – Clinique de la Dyspnée, F-75015 Paris, France; 2Cabinet La Berma, 4 avenue de la Providence; F-92160 Antony, France; 3AP-HP, Hôpital Européen Georges Pompidou, Unité d'Épidémiologie et de Recherche Clinique, F-75015 Paris, France; 4INSERM, Centre d'Investigation Épidémiologique 4, F-75015 Paris, France; 5Université Paris Descartes, Sorbonne Paris Cité, Faculté de Médecine, F-75015 Paris, France; 6AP-HP, Hôpital Européen Georges Pompidou, Service de Pneumologie; F-75015 Paris, France; 7CIC 9201 Plurithématique, Hôpital Européen Georges Pompidou, F-75015 Paris, FranceBackground: The aims of the study were: (1) to compare numerical parameters of specific airway resistance (total, sRawtot, effective, sRaweff and at 0.5 L • s-1, sRaw0.5) and indices obtained from the forced oscillation technique (FOT: resistance extrapolated at 0 Hz [Rrs0 Hz], mean resistance [Rrsmean], and resistance/frequency slope [Rrsslope]) and (2) to assess their relationships with dyspnea in chronic obstructive pulmonary disease (COPD).Methods: A 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.Results: Principal 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 Rawtot and Raweff (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), Rrsslope), while Rrsmean and Raw0.5 explored more central airways. Only specific resistances taking into account the specific resistance loop area (sRawtot and sRaweff) and Rrsslope were statistically linked to dyspnea.Conclusion: Parameters obtained from both body plethysmography and FOT can explore peripheral airways, and some of these parameters (sRawtot, sRaweff, and Rrsslope) are linked to activity-related dyspnea in moderate to severe COPD patients.Keywords: body plethysmography, forced oscillation technique, principal component analysis