Nutritional status is an important predictor of diaphragm strength in young patients with cystic fibrosis

Abstract

Background: The effect of nutritional status and lung disease progression on diaphragm strength in young patients with cystic fibrosis remains unclear. Objective: The aim of this study was to investigate the effect of nutritional status and airway obstruction on diaphragm strength. Design: Twitch transdiaphragmatic pressure (Tw Pdi) obtained by bilateral anterior magnetic phrenic nerve stimulation, body mass index (BMI) z score, fat mass, fat-free mass (FFM), arm muscle circumference (AMC), forced expiratory volume in 1 s (FEV1), and functional residual capacity (FRC) were measured in 20 patients aged 15.1 ± 2.8 y (x- ± SD). Values were expressed as a percentage of predicted values. Results: Mean (±SD) Tw Pdi was 24.3 ± 5.5 cm H2O. Univariate regression analysis showed positive correlations between Tw Pdi and nutrition scores (BMI z score: r = 0.63, P = 0.003; FFM: r = 0.47, P = 0.04; AMC: r = 0.45, P = 0.04), airway obstruction (FEV1: r = 0.68, P = 0.001), and arterial oxygen partial pressure (r = 0.68, P = 0.001). Negative correlations were observed between Tw Pdi and dynamic hyperinflation (FRC: r = -0.65, P = 0.005) and arterial carbon dioxide pressure (r = -0.50, P = 0.03). Furthermore, stepwise regression analysis showed that Tw Pdi correlated with BMI z score (r = 0.75, P = 0.0002) and FEV1 (r = 0.69, P = 0.001). Conclusions: Diaphragm strength is relatively well preserved in young patients with cystic fibrosis. However, the strength of the diaphragm decreases with the progression of malnutrition and airway obstruction. © 2004 American Society for Clinical Nutrition.