• Michelle Ramsay, Swapna Mandal, Eui-Sik Suh, Joerg Steier, Abdel Douiri, Patrick Brian Murphy, Michael Polkey, Anita Simonds, and Nicholas Hart.
• Lane Fox Respiratory Unit, Guy's, St Thomas' NHS Foundation Trust, London, UK Division of Asthma, Allergy and Lung Biology, King's College London, London, UK.
• Thorax. 2015 Oct 1;70(10):946-52.

IntroductionPatient-ventilator asynchrony (PVA) can adversely affect the successful initiation of non-invasive home mechanical ventilation (HMV). The aim of this observational study was to quantify the prevalence of PVA during initiation of HMV and to determine the relationship between PVA and nocturnal gas exchange.MethodType and frequency of PVA were measured by surface parasternal intercostal muscle electromyography, thoracoabdominal plethysmography and mask pressure during initiation of HMV. Severe PVA was defined, as previously, as asynchrony affecting ≥10% of breaths.Results28 patients (18 male) were enrolled aged 61±15 years and with a body mass index of 35±9 kg/m(2). Underlying diagnoses were neuromuscular disease with or without chest wall disease (n=6), obesity related chronic respiratory failure (n=12) and COPD (n=10). PVA was observed in all patients with 79% of patients demonstrating severe PVA. Triggering asynchrony was most frequent, observed in 24% (IQR: 11-36%) of breaths, with ineffective efforts accounting for 16% (IQR: 4-24%). PVA types were similar between disease groups, with the exception of auto-triggering, which was higher in patients with COPD (12% (IQR: 6-26%)). There was no correlation observed between PVA and time spent with oxygen saturations ≤90%, mean oxygen saturations or transcutaneous carbon dioxide levels during overnight ventilation.ConclusionsSevere PVA was identified in the majority of patients, irrespective of pathophysiological disease state. This was not associated with ineffective ventilation as evidenced by gas exchange.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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