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Background: Continuous, non-invasive assessment of alveolar ventilation achieved by transcutaneous PCO(2) (PtcCO(2)) monitoring is clearly superior to intermittent, invasive blood gas analyses in patients receiving nocturnal non-invasive positive pressure ventilation (NPPV), but the reliability and accuracy of PtcCO(2)-monitoring is still disputed. The present study was aimed at investigating the capability of modern PtcCO(2)-monitoring to reliably assess alveolar ventilation during nocturnal NPPV., Methods: Capillary blood gas measurements (11pm, 2am, 5am and 7am) and 8 h of continuous PtcCO(2)-monitoring using three of the latest generation devices (SenTec Digital Monitor, Radiometer TCM4-TINA and Radiometer TOSCA500) were performed during polysomnography-proven sleep studies in 24 patients receiving NPPV (15 with COPD, 9 with restrictive disorders)., Results: The technical calibration drift for SenTec DM, TCM4-TINA and TOSCA500 was 0.1, -0.4 and -0.5 mmHg/h, respectively. Bland-Altman method comparison of PaCO(2)/drift-uncorrected PtcCO(2) revealed a mean bias (limits of agreement) of 1.0 (-4.7 to 6.7), -1.5 (-15.6 to 12.5) and 0.8 (-6.8 to 8.3) mmHg, respectively. Continuous overnight PtcCO(2)-monitoring detected variations in alveolar ventilation, with median ranges of 12.3 (10.7-14.5) mmHg for SenTec DM, 14.5 (12.5-17.0) mmHg for TCM4-TINA and 11.5 (11.0-13.0) mmHg for TOSCA500 (RM-ANOVA, p < 0.001). The four capillary PaCO(2) values ranged by a median of 6.3 (4.7-9.7) mmHg., Conclusions: Modern PtcCO(2)-monitoring is reliable, accurate and robust. Since PtcCO(2)-monitoring is also non-invasive, does not disrupt sleep quality and provides a more complete picture of alveolar ventilation than intermittent capillary PaCO(2), PtcCO(2)-monitoring should become the preferred technique for assessing alveolar ventilation during nocturnal NPPV., Trial Registration: DRKS00000433 at http://apps.who.int/trialsearch/default.aspx., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

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.

Background: Average volume-assured pressure support (AVAPS) has been introduced as a new additional mode for a bilevel pressure ventilation (BPV) device (BiPAP; Respironics; Murrysville, PA), but studies on the physiologic and clinical effects have not yet been performed. There is a particular need to better define the most efficient ventilatory treatment modality for patients with obesity hypoventilation syndrome (OHS)., Methods: In OHS patients who did not respond to therapy with continuous positive airway pressure, the effects of BPV with the spontaneous/timed (S/T) ventilation mode with and without AVAPS over 6 weeks on ventilation pattern, gas exchange, sleep quality, and health-related quality of life (HRQL) assessed by the severe respiratory insufficiency questionnaire (SRI) were prospectively investigated in a randomized crossover trial., Results: Ten patients (mean [+/- SD] age, 53.5 +/- 11.7 years; mean body mass index, 41.6 +/- 12.1 kg/m2; mean FEV1/FVC ratio, 79.4 +/- 6.5%; mean transcutaneous P(CO2) [PtcCO2], 58 +/- 12 mm Hg) were studied. PtcCO2 nonsignificantly decreased during nocturnal BPV-S/T by -5.6 +/- 11.8 mm Hg (95% confidence interval [CI], -14.7 to 3.4 mm Hg; p = 0.188), but significantly decreased during BPV-S/T-AVAPS by -12.6 +/- 12.2 mm Hg (95% CI, -22.0 to -3.2 mm Hg; p = 0.015). Pneumotachographic measurements revealed a higher individual variance of peak inspiratory pressure (p < 0.001) and a trend for lower leak volumes but also for higher tidal volumes during BPV-S/T-AVAPS. The SRI summary scale score improved from 63 +/- 15 to 78 +/- 14 during BPV-S/T (p = 0.004) and to 76 +/- 16 during BPV-S/T-AVAPS (p = 0.014). Sleep quality and oxygen saturation also comparably improved following BPV-S/T and BPV-S/T-AVAPS., Conclusion: BPV-S/T substantially improved oxygenation, sleep quality, and HRQL in patients with OHS. AVAPS provided additional benefits on ventilation quality, thus resulting in a more efficient decrease of PtcCO2. However, this did not provide further clinical benefits regarding sleep quality and HRQL.

Both pressure- and volume-limited non-invasive positive pressure ventilation (NPPV) have been used in patients with chronic respiratory failure. The aim of the present study was to compare the efficacy of ventilation during nocturnal volume- and pressure-limited NPPV. Fifteen patients (nine COPD, six non-COPD) were randomly assigned to receive either volume-limited or pressure-limited NPPV and were switched to the complementary mode after 6 weeks. Ten patients (five COPD, five non-COPD) completed the study. PaCO2 during sleep comparably decreased from 54.6+/-8.0 to 46.2+/-6.1 mmHg during volume-limited NPPV (P<0.05), and to 46.5+/-6.4 mmHg during pressure-limited NPPV (P<0.05). Improvements in sleep quality assessed by polysomnography were comparable, but less gastrointestinal side effects were reported for pressure-limited NPPV (P<0.05). Using a pneumotachograph the variance of inspiratory volumes was lower, but the variance of peak inspiratory pressures was higher during volume-limited NPPV compared to pressure-limited NPPV. Substantial leak volumes which accounted for 57% (volume-limited NPPV) and for 58% (pressure-limited NPPV) of the applied inspiratory volume were independent from the mode of ventilation. In conclusion, nocturnal volume- and pressure-limited NPPV have similar effects on gas exchange and sleep quality in patients with hypercapnic chronic respiratory failure, but volume-limited NPPV is associated with more gastrointestinal side effects.