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NIV: clinical aspects

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1K. K. Lee, 1A. Mistry, 1N. Grey, 1P. Murphy, 1A. J. Williams, 1A. C. Davidson, 2N. Hart. 1Lane Fox Respiratory Unit, Guy’s & St Thomas NHS Foundation Trust, London, UK, 2Guy’s & St Thomas NHS Foundation Trust and King’s College London NIHR Biomedical Research Centre, London, UK

Background Respiratory complications of obesity are increasingly common. The definition of obesity hypoventilation syndrome (OHS) is an overlap between daytime hypercapnia and sleep-disordered breathing in obese patients. This description could more clearly be defined as obesity-related respiratory failure (ORRF) incorporating three separate groups: hypercapnic obstructive sleep apnoea (OSA), combined OSA and OHS (OSA–OHS) and lone OHS. However, distinguishing between these groups in clinical practice is often difficult without detailed nocturnal physiological monitoring. We hypothesised that clinical anthropometric data would distinguish between OSA, combined OSA–OHS and OHS.

Method Data of 88 patients initiated on home mechanical ventilation from August 2005 to June 2008 were analysed from a purpose-designed electronic discharge summary database. The groups were defined by detailed overnight physiological studies. As the proportion of OHS was low (n = 8), we combined OSA–OHS and OHS for comparative purposes.

Results 42% of patients had OSA and 58% had OSA–OHS or lone OHS. The mean age was 52 (16) and 55 (15) years, respectively, with 70% males in the OSA group and 49% males in the OSA–OHS and OHS group. The results are shown in table 1.

Conclusion Although there was no difference in subjective somnolence between the groups, body weight and body mass index (BMI) were higher in the patients with OSA–OHS and OHS compared with the patients with hypercapnic OSA. Furthermore, these patients had an increased prevalence of the clinical features of cor pulmonale. As a consequence of the higher BMI, there was a greater restrictive lung defect in the patients with OSA–OHS compared with those with OSA, possibly exacerbating the more pronounced gas exchange impairment. Interestingly, despite the greater level of hypoxia there was no difference in the prevalence of secondary polycythaemia between the groups. In conclusion, in obese patients with hypercapnia, clinical features provide useful data to distinguish between patients with hypercapnic OSA, OSA–OHS and OHS based on body composition, signs of right heart failure, lung volume and gas exchange.

Abstract S53 Table 1


1G. Walters, 1S. Gill, 2B. Beauchamp, 2E. Gallagher, 1R. Mukherjee, 3H. Osman, 1D. Banerjee. 1Department of Sleep and Ventilation, Birmingham Heartlands Hospital, Birmingham, UK, 2Department of Physiotherapy, Birmingham Heartlands Hospital, Birmingham, UK, 3Department of Virology, Birmingham Heartlands Hospital, Birmingham, UK

Introduction Outbreaks of influenza (flu) have major impacts on hospital admissions and mortality. The usual flu rate for the 50th week of the year over the past 9 years in England is ∼23 cases per 100 000 population, but in 2008 it stood at 39.5 (Royal College of General Practitioners data). The Midlands was particularly badly hit by this outbreak, with a prevalence of 56 per 100 000. Such surges put pressures on health services, but there are few data on their impact on non-invasive ventilation (NIV) service providers. We hypothesised that seasonal flu outbreaks impact on NIV service requirements with adverse effects on admissions and outcomes, especially intubation rates and mortality.

Methods The Birmingham Heartlands hospital 11-bedded physiotherapy-run NIV service has on average 180 admissions/year for the treatment of acute hypercapnic respiratory failure. 72% are chronic obstructive pulmonary disease (COPD) exacerbations, intubation rate is 3.5% and mortality is 15%. A retrospective observational study (June 2007 to May 2009) was undertaken to determine if there is a relationship between confirmed hospital flu cases and the number of NIV admissions, intubations and deaths (ie, NIV therapy failure). In this study the following seasons were categorised as: summer, June to August; autumn, September to November; winter, December to February; and spring, March to May. Total flu cases stated includes types A and B.

Results Figure 1 shows the prevalence of confirmed hospital flu cases and the number of NIV admissions, intubations and deaths as a result of failure of therapy. Observation of the data suggests that seasonal peaks (as by hospital cases) do indirectly result in an increase in admissions requiring NIV and resultant rises in intubations and deaths. The data do not show how many NIV episodes were directly flu related.

Conclusions This observational study may suggest that seasonal outbreaks of community flu and therefore the resultant increase in hospital flu admissions may have an impact on the workload of NIV units, with an increase in admissions requiring NIV and ultimately an increase in the requirement for invasive ventilatory support and death. Predicting outbreaks of flu may allow better workforce planning for NIV units to cope with surges in activity.

Abstract S54 Figure 1

AU, autumn; NIV, non-invasive ventilation; SP, spring; SU, summer; WI, winter.


1L. H. Piggin, 1E. W. Thornton, 2R. M. Angus, 2B. Chakrabarti, 3C. A. Young. 1School of Psychology, University of Liverpool, Liverpool, UK, 2Aintree Chest Centre, University Hospital Aintree, Liverpool, UK, 3Walton Centre for Neurology and Neurosurgery, Liverpool, UK

Introduction Non-invasive ventilation (NIV) can palliate symptoms of nocturnal hypoventilation in motor neuron disease (MND) and improve quality of life. There has been no qualitative description of how patients’ thoughts and feelings may evolve whilst making the transition onto NIV and how physical/psychological changes are perceived by patients.

Methods 10 patients with MND participated in semi-structured interviews before being established on NIV and again 3 months following NIV initiation. Interviews were transcribed verbatim before undergoing thematic analysis. Salient themes were used to provide a phenomenological narrative.

Results Pre-NIV, framing in regard to disease progression was an important determinant of early emotional response. For some, NIV represented a negative “milestone” in physical decline, whilst for others, an opportunity/hope for improvement. Most were reluctant to consider “realities” of NIV until use was imminent, with resignation and anxiety common themes. Resistance increased where the link between ventilation and actual symptoms was poorly understood, creating conflict between subjective/objective need for treatment. Most patients perceived no subjective need for ventilation pre-NIV, describing decision making as led by professionals and family members. Reports of having “no choice” were common; however, after ventilation many patients reported that the non-invasive nature of treatment did give them choice which reassured and empowered them. Post-NIV, most reported improved sleep/energy levels; negative aspects were outweighed by positive physical effects. However, managing expectation was important; a minority finding effects disappointing or the struggle to adjust to the machine actually increasing sleep disturbance and anxiety. Patients reporting no effect were still motivated to continue “just in case” fearing no change with NIV might equate to significant physical decline without NIV.

Conclusion The diversity of experience and feeling amongst patients demonstrates that the physical and emotional landscape continually shifts in MND. Prior to treatment, perceptions of NIV ranged from alarm, with NIV seen as a marker of severe decline, to positivity as a potentially beneficial therapy. Some expectations were unrealistic, which correlated with later disappointment. In general, patients appeared ambivalent pre-NIV; however, following initiation of NIV they reported improved sleep and energy levels. This work suggests managing expectations is a central issue in using NIV in MND.

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