Ultrasound evaluation of diaphragm function in children with chronic respiratory failure

Introduction: Clinically, a noninvasive measure of diaphragm function is needed in children. We hypothesized that ultrasonography can quantify diaphragm function and identify those children with chronic respiratory failure. Methods: 15 children were studied prospectively with mean age=2.1±6.3 yrs (range=0-22). The following groups were studied: 1)children after cardiac surgery and immediately before successful extubation (normal); 2)children with chronic respiratory failure (chronic). Ultrasound measurements were made during breathing through a T piece before and after adding 5% carbon dioxide (CO₂). The inspiratory (i) and expiratory (e) effort dependent measurements indexed for body surface area were: A)mean velocity (VEL_i(cm/sec/m²)) of the posterior diaphragm in transverse section, B)distance of the posterior diaphragm from the most anterior adrenal gland/kidney junction (D D_e (cm/m²)) and inspiratory time (T (sec/m²)) in sagittal section. The difference between D_i and D_e (ΔD(cm/m²)) was calculated. Measurements were made in triplicate and averaged. Data were analyzed using independent Student's t test with p≤0.05 being significant. Results: (mean±sem) n VEL_i ΔD T_i Normal 10 8.5±1.6 1.9±0.4 1.7±0.2 Chronic S 2.7±0.9*0.8±0.2*0.8±0.2*Normal+CO ₂ 9 8.9±1.4 2.2±0.5 1.9±0.2 Chronic+CO₂ 4 4.6±2.4 0.5±0.2*1.0±0.2*(*=difference from Normal, p≤0.05) Conclusions: Ultrasonography can be used to quantify diaphragm function and discriminate between normal children and those with chronic respiratory failure.