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NIV: clinical aspects

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A. Gulati, M. Ali, N. Oscroft, M. G. Davies, T. Quinnell, J. M. Shneerson, I. E. Smith. Papworth Hospital NHS Foundation Trust, Papworth Everard, UK

Introduction and Objectives Chronic ventilatory failure secondary to chronic obstructive pulmonary disease (COPD) is the most common indication for domiciliary non-invasive ventilation (NIV) in Europe. The aim of this study was to establish the efficacy and tolerability of a novel autovariable positive airway pressure (iVAPS, ResMed, Australia) ventilator compared with standard NIV (NIPPY, B and D electromedical, UK) in ventilator-naïve patients with COPD.

Methods Patients with chronic ventilatory failure secondary to COPD starting domiciliary NIV were randomised to receive iVAPS or standard NIV and followed-up at 1 and 3 months with repeat blood gas measurements, overnight pulse oximetry and quality of life scores (SF-36 and SGRQ).

Results Preliminary data of 21 patients are presented here. Ten were males, mean age 67 (SD 9.00) years, mean forced expiratory volume in 1 s (FEV1) 0.62 (SD 0.24) litres, mean PaCO2 8.49 (SD 1.4) kPa mean PaO2 6.79 (SD 0.85) kPa, mean SpO2 85.4% (SD 4.16%). Eleven were randomised to iVAPS and 10 to NIPPY. Three patients died (1 iVAPS and 2 NIPPY) before their first reassessment. At baseline there was no difference in age, body mass index, FEV1, PaO2, PaCO2 and mean SpO2 overnight between the two groups. At 3 months, on iVAPS there was a significant fall in mean PaCO2 of 1.98 kPa (SD 1.68, p  = 0.008) and rise in mean PaO2 of 1.14 kPa (SD 1.07, p  = 0.02). On NIPPY, a small but insignificant improvement was seen in mean PaCO2 and mean PaO2. Comparing the two groups for improvement in daytime blood gases, no significant differences were observed. Nocturnal oxygenation improved similarly on both the ventilators (mean nocturnal SpO2 improved by 3.0% on iVAPS and 5.63% on NIPPY). No difference was observed in the tolerability, comfort of use or hours of use (mean usage per night on iVAPS 6.4 h and on NIPPY 5.22 h, p = 0.38) between the ventilators.

Conclusion iVAPS was shown to be effective in improving daytime PCO2 and PO2 and was well tolerated in patients with COPD with chronic ventilatory failure. It was at least as effective as standard NIV.


1P. Murphy, 1K. Brignall, 2M. Hind, 2A. Simonds, 1C. Davidson, 1A. Williams, 3J. Moxham, 1M. Polkey, 4N. Hart. 1Lane Fox Respiratory Unit, Guy’s & St Thomas’ NHS Foundation Trust, London, UK, 2Sleep & Ventilation Unit, Royal Brompton & Harefield NHS Foundation Trust, London, UK, 3Department of Thoracic Medicine, King’s College Hospital, London, UK, 4Guy’s & St Thomas’ NHS Foundation Trust and Kings College London NIHR Biomedical Research Centre, London, UK

Introduction The levels of physical activity in patients with obesity hypoventilation syndrome (OHS) have not previously been measured. Although in simple obesity a relationship between anthropometrics and physical activity has been reported (NEJM;332:621), the effect of daytime somnolence, accompanying sleep-disordered breathing in OHS, on activity has not been investigated. We hypothesised that low activity levels would be associated with the degree of hypersomnolence and daytime arterial partial pressure of oxygen (PaO2) and carbon dioxide (PaCO2).

Methods Consecutive patients admitted for initiation of home mechanical ventilation (HMV) were provided with Actiwatches (Phillips-Respironics, Murrayville, USA) to monitor physical activity. The monitors were continuously worn for 7 days and returned with a diary card identifying sleep and nap times. Activity counts were analysed during daytime waking hours to produce mean and peak activity counts/day and the average number of minutes of sedentary (<40 counts/min) and moderate (>1500 counts/min) activity/day. Baseline anthropometric and arterial blood gases (ABG) were taken prior to initiation of HMV.

Results Ten patients (3 male) with mean age of 55.8 (9.6) years and Epworth Sleepiness Scores (ESS) of 14 (3.6). Mean body mass index (BMI) was 51.4 (8.7) kg/m2, waist circumference 139.6 (18.8) cm and fat free mass (FFM) 62.7 (18.5) kg. At initiation of ventilation, PaCO2 was 7.27 (1.34) kPa and PaO2 was 8.2 (1.94) kPa. Activity data showed that time spent in moderate activity was 7.2 (10) min/day and sedentary activity 409 (200) min/day. There was an inverse correlation between BMI and both mean activity (r2 = 0.56; p = 0.01) and peak activity (r2 = 0.50, p = 0.02). There was a similar relationship between waist circumference and mean activity (r2 = 0.67, p = 0.0038) and peak activity (r2 = 0.62, p = 0.0073). However, there was no correlation between ESS, FFM, PaCO2 or PaO2 and mean or peak activity.

Conclusions These data demonstrate extremely low levels of physical activity in patients with OHS at initiation of HMV. In contrast to our hypothesis, there were no correlations between activity and daytime somnolence or gas exchange, and the most relevant predictor of low activity was the degree of obesity. Furthermore, in contrast to previous data in simple obesity, FFM was not correlated with higher activity levels. Further studies are required to investigate the changes in physical activity following treatment with HMV.

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