THORACOABDOMINAL PATTERN OF BREATHING IN NEUROMUSCULAR DISORDERS

Study objective: To assess abnormalities in thoracoabdominal pattern o f breathing (TAPB) in neuromuscular disorders during spontaneous breat hing, intermittent positive pressure ventilation (IPPV) with and witho ut abdominal (AB) binder, and immediately after IPPV. Design: Repeated measures design: Pre-IPPV spontaneous breathing, IPPV, IPPV with AB b inder, and post-IPPV spontaneous breathing. In protocol 1, ventilator pressure was held constant at the individual value habitually adopted in sessions of IPPV. In protocol 2, it was increased stepwise from 5 t o 30 cm H2O. Setting: University hospital, Department of Pediatrics, I ntensive Care, and Neuro-Ventilatory Rehabilitation. Patients: Thirty- one patients with spinal muscular atrophy (SMA) and 19 patients with m yopathy, mean age (+/-SD) 9.7+/-3 years. Measurements: Tidal volume (V T), percent thoracic contribution to VT (%RC), the phase angle between the thoracic and the AB volume changes and the labored breathing inde x, which is an index of asynchrony taking into account both the phase relationships and relative volumes of rib cage and AB compartments. Re sults: We observed marked abnormalities in TAPB during spontaneous bre athing, especially in the SMA group. %RC, labored breathing index, and phase angle displayed nearly normal values during IPPV. IPPV pressure s of 25 to 30 cm H2O were necessary to increase %RC above 80%. AB bind ing decreased VT, but led to larger thoracic volumes, especially in pa tients with SMA. Thoracic contribution to VT and thoracic volume after IPPV were higher than baseline levels. Conclusions: The quantitative assessment of TAPB enhances the ability to estimate pulmonary function in neuromuscular disorders, and the efficiency of mechanical ventilat ion.