Efecto de la maniobra inspiratoria y de la hiperinsuflación pulmonar en los flujos espiratorios máximos en pacientes con fibrosis quística

Abstract

The time course of the inspiration preceding the maximal forced expiratory maneuver (MFEM) has not been studied in cystic fibrosis (CF). We tested the hypothesis that CF children would have significantly higher forced expiratory volumes (FVC) and flows with decreasing duration of the inspiratory breathhold. We studied 16 stable CF patients (10 males) with no pulmonary exacerbation 2 months prior to the study, aged 11.9 ± 0.7 years (mean ± SEM) with a FEV1 of 62.8 ± 6.4% predicted. Pulmonary function tests included static lung volume and airway resistance measurements, followed by dynamic lung function measurements. The latter were preceded by 3 different inspiratory maneuvers in a random order [breathhold of 0 (M0), 2 (M2) or 5 seconds (M5)]. Patients were divided by the presence of lung hyperinflation (RV/TLC > 30%), with 9 children with hyperinflation and 7 no-hyperinflated patients. We found that, in the hyperinflated CF patients (RV/TLC > 30%), FEV1 and FVC were 8.9 ± 3.4% (p < 0.02) and 9.3 ± 2.1% (p < 0,001) higher respectively after M0 than after M2 and 2.4 ± 2.8% (p = ns) and 2.8 ± 3.2% (p = ns) lower respectively after M5 than after M2 (M0 vs M5: p < 0.01 for both FEV1 and FVC). In summary, in hyperinflated CF children, FEV1 and FVC are significantly higher after no inspiratory breathhold compared to a breathhold of 2 or 5 sec and we speculate that stress relaxation may account for this phenomenon. We suggest that standardization of the inspiratory maneuver is important in lung function studies in CF patients.