Clinical impact of leak compensation during non-invasive ventilation - 07/08/11

Doi : 10.1016/j.rmed.2009.04.020 
Jan Hendrik Storre, Philipp Bohm, Michael Dreher, Wolfram Windisch
Department of Pneumology, University Hospital Freiburg, Killianstrasse 5, D-79106 Freiburg, Germany 

Corresponding author. Tel.: +49 761 270 3706; fax: +49 761 270 3704.



This study aimed to assess the impact of leak compensation capabilities during pressure- and volume-limited non-invasive positive-pressure ventilation (NPPV) in COPD patients.


Fourteen patients with stable hypercapnic COPD who were receiving long-term NPPV were included in the study. For both modes of NPPV, a full face mask and an artificial leak in the ventilatory circuit were used at three different settings, and applied during daytime NPPV, either without leakage (setting I), with leakage during inspiration only (setting II), and with leakage during inspiration and expiration (setting III). Ventilation pattern was pneumotachygraphically recorded.


NPPV was feasible with negligible leak volumes, indicating optimal mask fitting during the daytime (setting I). In the presence of leakage (settings II and III), the attempt to compensate for leak was only evident during pressure-limited NPPV, since inspiratory volumes delivered by the ventilator increased from 726±129 (setting I) to 1104±164 (setting II), and to 1257±166 (setting III) ml during pressure-limited NPPV, respectively (all p<0.001); however, they remained stable during volume-limited NPPV. Leak compensation resulted in a decrease in leakage-induced dyspnea. However, 83%/87% (setting II/III) of the additionally-delivered inspiratory volume during pressure-limited NPPV was also lost via leakage. Expiratory volume was higher in setting II compared to setting III (both p<0.001), indicating the presence of significant expiratory leakage.


The attempt at leak compensation largely feeds the leakage itself and only results in a marginal increase of tidal volume. However, pressure-limited – but not volume-limited – NPPV results in a clinically-important leak compensation in vivo. Trial registration: www.uniklinik-freiburg.de/zks/live/uklregister/Oeffentlich.html Identifier: UKF001272.

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Keywords : Chronic obstructive pulmonary disease, Leakage, Mask, Non-invasive positive-pressure ventilation, Respiratory insufficiency

Abbreviations : ANOVA, BMI, COPD, CO2, FEV1, FVC, fb, HCO3, HRF, ID, IPAP, LTOT, ml, mm, min, NPPV, PEEP, PCV, PaCO2, PaO2, PIP, Pmean, ref, RV, SaO2, SD, TLC, V-exp, V-insp, V-leak, VCV


© 2009  Elsevier Ltd. Tous droits réservés.

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Vol 103 - N° 10

P. 1477-1483 - octobre 2009 Retour au numéro
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