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Clinical impact of leak compensation during non-invasive ventilation . BACKGROUND 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 . METHODS 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 pneumotachy-graphically recorded . RESULTS 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 . CONCLUSIONS 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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Intervention_Physical
non-invasive positive-pressure ventilation ( NPPV )
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Outcome_Physical
Ventilation pattern
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Outcome_Physical
leak volumes
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Outcome_Physical
leakage
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Outcome_Mental
inspiratory volumes delivered by the ventilator
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Outcome_Mental
leakage-induced dyspnea .
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Outcome_Other
Expiratory volume
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Participant_Sample-size
Fourteen
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Participant_Condition
stable hypercapnic COPD
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Participant_Condition
receiving long-term NPPV