Respiratory Physiology & Neurobiology 150 (2006) 251–260 Nocturnal non-invasive positive pressure ventilation: Physiological effects on spontaneous breathing Wolfram Windisch ∗ , Michael Dreher, Jan Hendrik Storre, Stephan Sorichter Department of Pneumology, University Hospital Freiburg, Killianstrasse 5, D-79106 Freiburg, Germany Accepted 19 May 2005 Abstract The dynamic process of how non-invasive positive pressure ventilation (NPPV) improves spontaneous ventilation is unclear. Therefore, daytime trends of blood gases and breathing pattern were assessed by measurements 0, 0.5, 1, 3, 7, 11 and 15 h after cessation of nocturnal controlled NPPV in patients with chronic hypercapnic respiratory failure. Twelve patients (six COPD/six restrictive) who were established on NPPV and 12 controls (six COPD/six restrictive) completed. PaCO 2 decreased during con- trolled NPPV (P < 0.02). PaCO 2 additionally decreased step by step during the first 3 h of spontaneous breathing after switching from NPPV to spontaneous breathing (P < 0.05), but remained unchanged in controls. The PaCO 2 decrease was due to a stepwise increase in tidal volume (P < 0.05) at an unchanged breathing frequency. Accordingly, minute ventilation also stepwise increased (P < 0.03). There were no significant changes in controls. Improvements of PaCO 2 and tidal volume occurred even after 5.7 ± 3.1 days following first NPPV trials, but became more evident after 2 months. Maximal inspiratory mouth pressures increased in chronic obstructive pulmonary disease (COPD) patients (P < 0.05), and respiratory drive increased in restrictive patients (P <0.05) following 2 months of NPPV. Lung function parameters and inspiratory impedance remained unchanged. Improve- ments in health-related quality of life were evident and were correlated to the decline of elevated bicarbonate levels (r = 0.72, P < 0.01). In conclusion, there is a stepwise adaptation process lasting 3 h when switching from nocturnal controlled NPPV to daytime spontaneous breathing in which tidal volume increases and PaCO 2 drops after an initial PaCO 2 decrease while on NPPV. © 2005 Elsevier B.V. All rights reserved. Keywords: Hypercapnia; Inspiratory impedance; Minute ventilation; Quality of life; Tidal volume 1. Introduction Non-invasive positive pressure ventilation (NPPV) delivered by a facial mask is a well established and ∗ Corresponding author. Tel.: +49 761 270 3706; fax: +49 761 270 3704. E-mail address: windisch@med1.ukl.uni-freiburg.de (W. Windisch). increasingly used therapeutic option for patients with chronic hypercapnic respiratory failure (HRF) due to various underlying diseases, such as chest wall defor- mities, neuromuscular diseases and chronic obstructive pulmonary disease (COPD) (Anon., 1999; Mehta and Hill, 2001; Hill, 2004). Here, intermittent NPPV is used at home predominantly during night while patients usu- ally breathe spontaneously during daytime for most of the time. 1569-9048/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.resp.2005.05.017