Objective: To evaluate the acute effects of noninvasive positive pressure ventilation (NPPV) in patients with stable chronic respiratory failure secondary to cystic fibrosis.
Patients: Eight patients (29±5 years of age) with severe airflow limitation (mean FEV1, 24±3% predicted) and chronic respiratory failure (PaO2=67±15 mm Hg and PaCO2=50±4 mm Hg) were evaluated.
Methods: Tidal volume, respiratory rate, minute ventilation, oxygen saturation, and transcutaneous CO2 (TcCO2) measurements were made over a 20-min period before and after the application of NPPV (inspiratory pressure of 10 to 12 cm H2O and expiratory pressure of 4 to 6 cm H2O).
Results: NPPV increased saturation from 88±2% to 90±1% (p<0.05) and decreased TcCO2 from 51±3 mm Hg to 50±2 mm Hg (p<0.05). Tidal volume increased from 219±20 mL to 256±37 mL (p=not significant [NS]) and respiratory rate decreased from 24±2 to 18±1 (p<0.01). Minute ventilation decreased from 5.3±0.8 L/min to 4.6±0.6 L/min (p=0.08). There was no change in duty cycle (32±5% to 34±5%, p=NS). In two patients, esophageal pressure measurements were also recorded. There was a decrease in pressure from −21±1 cm H2O to −11±2 cm H2O and −14±1 cm H2O to −7±1 cm H2O.
Conclusions: In patients with stable, severe cystic fibrosis, NPPV (1) acutely improves gas exchange, (2) decreases minute ventilation, suggesting either a reduction in CO2 production or an increase in alveolar ventilation, and (3) reduces work of breathing.