ORIGINAL ARTICLE

Non-invasive proportional assist and pressure support ventilation in patients with cystic fibrosis and chronic respiratory failure

A Serra¹, G Polese², C Braggion¹, A Rossi²

¹ Centro Regionale Fibrosi Cistica, Azienda Ospedaliera di Verona, Ospedale Civile Maggiore di Borgo Trento, Verona, Italy
² Unità Operativa Pneumologia, Ospedali Riuniti di Bergamo, Bergamo, Italy

Correspondence to:
Correspondence to:
Dr A Rossi, Unità Operativa Pneumologia, Ospedali Riuniti, Largo Barozzi 1, I-24128 Bergamo, Italy;
arossi{at}ospedaliriuniti.bergamo.it

Background: Patients with advanced cystic fibrosis can benefit from non-invasive positive pressure ventilation (NPPV) for the treatment of acute decompensation as well as for the management of chronic respiratory failure. This study was undertaken to compare the physiological effects of non-invasive proportional assist ventilation (PAV) and pressure support ventilation (PSV) on ventilatory pattern, transcutaneous blood gas tensions, and diaphragmatic effort in stable patients with cystic fibrosis and chronic CO₂ retention.

Methods: In 12 patients two periods of spontaneous breathing were followed randomly by PSV (12 (3) cm H₂O) and PAV (flow assist 4.9 (1.3) cm H₂O/l.s, volume assist 18.9 (5.1) cm H₂O/l) set for the patient's comfort and administered for 40 minutes with 2 cm H₂O continuous positive airway pressure. Ventilatory pattern, transcutaneous blood gas tensions, and surface diaphragmatic electromyography were measured in the last 10 minutes of each application.

Results: On average, both PSV and PAV improved ventilation (+30%), tidal volume (+30%), and transcutaneous CO₂ (-7%) while reducing diaphragmatic activity (-30% with PSV, -20% with PAV). Mean inspiratory airway pressure was lower during PAV than during PSV (9.7 (1.9) and 12.9 (2.7) cm H₂O, respectively; p<0.05). The mean coefficient of variation of tidal volume was about 20% (range 11–39%) during spontaneous breathing and did not change with either PAV or PSV.

Conclusions: These results show that short term administration of nasal PAV and PSV to patients with stable cystic fibrosis with chronic respiratory insufficiency is well tolerated, improves ventilation and blood gas tensions, and unloads the diaphragm.

Abbreviations: CVF, chronic ventilatory failure; Edi, electromyograph of the diaphragm; f, respiratory frequency; IC, inspiratory capacity; NPPV, non-invasive positive pressure ventilation; Pao, pressure at airway opening; PAV, proportional assist ventilation; PSV, pressure support ventilation; SaO2, oxygen saturation; TcCO2, transcutaneous CO2 pressure; TcO2, transcutaneous O2 pressure; TE, expiratory time; TI, inspiratory time; TTOT, total cycle duration; V`E, minute ventilation; VT; tidal volume

Keywords: non-invasive positive pressure ventilation; chronic respiratory failure; respiratory muscles; cystic fibrosis

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