Two months auto-adjusting versus conventional nCPAP for obstructive sleep apnoea syndrome.

Autoadjusting nasal continuous positive airway pressure (CPAP) greatly reduces the apnoea/hypopnoea index (AHI), and affords a significant reduction in median pressure (P50) compared-with manually titrated conventional nasal CPAP. The aim of the present study was to test whether these benefits were maintained in the medium term at home, in a double-blind crossover study. Ten sequential subjects (mean AHI 52.9 x h(-1)) were enrolled. After a manual titration, subjects were randomly allocated to 2 months autoadjusting nasal CPAP (AutoSet), followed by 2 months with the AutoSet device in fixed pressure mode at the manually titrated pressure, or vice versa. The machine-scored AHI, P50, and median leak were recorded on 12 nights in each arm, and averaged. Mean+/-SEM AHI was 4.0+/-0.3 x h(-1) in auto mode, and 3.7+/-0.3 x h(-1) in manual mode (NS). Mean+/-SEM P50 was 7.2+/-0.4 cmH2O auto, 9.4+/-0.6 cmH2O manual, average reduction 23+/-4% (p<0.0001). Auto "recommended" pressure was (mean+/-SEM) 10.1+/-0.5 cmH2O (p=0.04 with respect to manual) and peak pressure typically 1 cmH2O higher. Median (+/-SEM) leak was 0.181+/-0.006 L x s(-1) auto (and uncorrelated with AHI or pressure), 0.20+/-0.006 L x s(-1) manual (p=0.003). Compliance was 6.3+/-0.4 h in auto mode and 6.1+/-0.5 h in fixed mode (NS). Apnoea/hypopnoea index during 2 months of home autoadjusting nasal continuous positive airway pressure is comparable to that during conventionally titrated fixed pressure continuous positive airway pressure, while affording a 23% reduction in median pressure but no increase in compliance. Leak did not importantly affect autoadjustment.

[Comparison of the efficacy of the BiPAP-S/T and the VPAP-S/T ventilators in patients with stable chronic respiratory insufficiency]. / Vergleich der Effektivität des BiPAP-S/T- und VPAP-S/T-Ventilators bei Patienten mit stabiler chronisch-respiratorischer Insuffizienz.

This study compares the performance characteristics and clinical effectiveness of the BiPAP-S/T (Respironics, USA) and VPAP-S/T (ResMed, Australia) pressure support ventilator during two weeks of nasal ventilation in 15 patients with stable chronic respiratory insufficiency. All patients were previously stabilised using nasal BiPAP ventilation for at least three months. Subjects had a maximum inspiratory pressure of 20 cm H2O and highest breathing rate of 24 per minute. VPAP is lighter and quieter than BiPAP-S/T (31 vs. 43 dB for IPAP:EPAP = 15:5 cm H2O and breathing frequency = 15 breaths per minute). Both machines demonstrate comparable and reliable triggering at low flow rates for zero and up to 30 l/min mask leak. Clinical evaluation in the S/T mode showed the two ventilators to be equally effective in supporting gas exchange during sleep. Sleep quality and number of respiratory arousals were very similar at the end of the two weeks' test period with BiPAP-S/T and VPAP-S/T. Synchronisation of VPAP-S/T during REM was probably better than with BiPAP-S/T, because in the presence of mouth leak BiPAP-S/T occasionally jammed in IPAP, but VPAP-S/T did not. In conclusion, in the tested settings VPAP-S/T is as effective as BiPAP-S/T in maintaining ventilation and controlling blood gases during sleep in patients with stable respiratory insufficiency.

AutoSet nasal CPAP titration: constancy of pressure, compliance and effectiveness at 8 month follow-up.

We have previously shown that AutoSet satisfactorily improves sleep-disordered breathing and sleep architecture in subjects with obstructive sleep apnoea (OSA) syndrome. The aim of this study was to determine, in subjects treated with long-term conventional fixed pressure continuous positive airway pressure (CPAP) at the AutoSet recommended pressure, whether: the long-term compliance is satisfactory; the improvement persists once initial rebound is over; the titration pressure is stable with time; and the titration pressure is comparable with manual titration pressure using a similar end-point. Twenty males with OSA, previously studied with full polysomnography on their diagnostic night, at manual and AutoSet titration, and at the AutoSet recommended fixed pressure, were re-studied after a mean of 3 and 8 months of treatment at the recommended fixed pressure. Re-study included home respiratory monitoring (Nellcor EdenTrace), and repeated manual and AutoSet titration with polysomnography. Compliance was assessed with hour-meter readings. Mean (+/-SEM) usage was 5.7 +/- 0.1 h.night-1 at 3 and 8 months. The arousal index remained normalized. Diagnostic respiratory disturbance index (RDI) was 60.3 +/- 5.7 events.h-1. On AutoSet at fixed CPAP, RDI was initially 2.6 +/- 0.7 events.h-1, then rose slightly (p < 0.001) to 4.3 +/- 0.6 events.h-1 at 3 months, and was 3.6 +/- 0.5 events.h-1 at 8 months. AutoSet titration pressure was: 9.9 +/- 0.4 cmH2O initially, 10.6 +/- 0.4 cmH2O at 3 months, and 9.7 +/- 0.5 cmH2O at 8 months (NS). Manual titration pressure at 8 months was 10.4 +/- 0.4 cmH2O. The standard deviation of the discrepancy with AutoSet was 0.84 cmH2O. In conclusion, the AutoSet recommended pressure varies little with time, and closely predicts the final manual titration pressure; the improvement in respiratory disturbance index was largely maintained, and compliance was good, although probably enhanced by close supervision.

[Functional results of surgical lung volume reduction in severe pulmonary edema]. / Funktionelle Ergebnisse der chirurgischen Lungenvolumenreduktion beim schweren Lungenemphysem.

BASIC PROBLEM AND OBJECTIVE OF THE STUDY: Lung volume reduction (LVR) is a new surgical approach designed to relieve shortness of breath and improve exercise tolerance in patients with severe lung emphysema. The aim of this study was to analyse changes of lung function, gas exchange, exercise tolerance and degree of dyspnoea one and 3 months after LVR. PATIENTS AND METHODS: Seventeen patients (15 men and two women; mean age 53 [38-68] years) with severe emphysema (six with alpha 1-PI deficiency) underwent unilateral (n = 14) or bilateral (n = 3) LVR surgery. One week before and one and 3 months after surgery pulmonary function tests, arterial blood gas analysis at rest breathing room air, 6-minute walking distance and dyspnoea score (Medical Research Council Scale) were determined. RESULTS: There was a significant increase in forced expiratory vital capacity after one second (FEV1, P < 0.001), and a significant decrease in total lung capacity (TLC, P < 0.0001) and residual volume (RV, P < 0.0001). The mean increase in FEV1 was 39% and in PaO2 9%. The mean decrease in TLC was 20%, in RV 26% (P < 0.001; both comparisons), and in paCO2 4% (not significant). The mean 6-minute walking distance increased by 96% from 229 to 405 meters (P < 0.0001). The mean dyspnoea score on a five point scale (0-4 points) decreased by 52% from 3.4 to 1.6. With the exception of the improved inspiratory vital capacity the postoperative results at one and 3 months after LVR did not differ significantly. All patients were alive 3 months postoperatively. CONCLUSIONS: In patients with severe emphysema surgical LVR shows significantly improved pulmonary function, gas exchange, dyspnoea and walking distance as assessed one and three months postoperatively. The early mortality seems to be low.

Effect of surgical lung volume reduction on respiratory muscle function in pulmonary emphysema.

Lung volume reduction surgery (LVRS) in patients with severe lung emphysema restores the thoracic configuration to a more normal functional capacity. The aim of this study was to investigate whether reduction in intrathoracic volume by LVRS improves the inspiratory muscle force generation of the respiratory pump. Pulmonary function tests, maximal inspiratory mouth pressure (MIP), sniff nasal inspiratory pressure (SNIP), sniff transdiaphragmatic pressure (Pdi), and inspiratory mouth occlusion pressure (P0.1) were measured in 17 emphysematous patients (mean (+/- SEM) age 53 +/- 2 yrs) before and 1 month after LVRS. The mean value of forced expiratory volume in one second (FEV1) increased (0.82 +/- 0.07 vs 1.12 +/- 0.08 L; p < 0.0001), whilst there was a decrease (p < 0.0001) in residual volume (RV) (337 +/- 31 vs 250 +/- 21 % of predicted), functional residual capacity (FRC) (210 +/- 9 vs 159 +/- 9% pred), and total lung capacity (TLC) (138 +/- 6 vs 110 +/- 5% pred). The mean value of MIP increased by 52% from 4.8 +/- 0.4 to 7.3 +/- 0.6 kPa (p < 0.001), the mean value of SNIP increased by 66% from 3.9 +/- 0.4 to 6.5 +/- 0.5 kPa (p < 0.001), and the mean value of Pdi increased by 28% from 6.0 +/- 0.6 to 7.7 +/- 0.8 kPa (p < 0.05) after LVRS. P0.1 decreased on average by 24% from 0.46 +/- 0.03 to 0.35 +/- 0.02 kPa after LVRS. No significant correlations were found between inspiratory muscle (MIP, SNIP, Pdi) and respiratory drive (P0.1) indices, lung function data, 6 min walk distance, or dyspnoea score. In conclusion, the observed clinical improvement of patients with severe emphysema after lung volume reduction surgery results, in part, from an increased ability of the inspiratory muscles to generate force, which is paralleled by a significant decrease in central respiratory drive.