Postural changes in 258 patients with pulmonary arteriovenous malformations (PAVMs) reviewed between 2005 and 2013 were evaluated prospectively using validated pulse oximetry methods. Of the 257 completing the test, 75 (29%) demonstrated orthodeoxia with an oxygen saturation fall of at least 2% on standing. None described platypnoea (dyspnoea on standing). The heart rate was consistently higher in the erect posture: 74 (29%) had a postural orthostatic tachycardia of ≥20 min . Orthostatic tachycardia was more pronounced in PAVM patients than controls without orthodeoxia (age-adjusted coefficient 5.5 (95% CIs 2.6, 8.4) min −1 , p<0.001). For PAVM patients, the age-adjusted pulse rise was 0.79 min −1 greater for every 1% greater drop in oxygen saturation on standing ( p<0.001). In contrast to the postural orthostatic tachycardia syndrome, in this population, there was a trend for more pronounced orthostatic tachycardia to be associated with better exercise tolerance. To the editorPulmonary arteriovenous malformations (PAVMs) result in hypoxaemia due to right-to-left shunting. 1Recent studies highlight that chronic hypoxaemia in ironreplete patients leads to secondary erythrocytosis which preserves arterial oxygen content (CaO 2 ).2 Both shunt fraction 3 and hypoxaemia severity 4 may increase acutely on standing, a phenomenon ascribed to basally situated PAVMs.3 4 Platypnoeaorthodeoxia (dyspnoea and arterial deoxygenation on standing) has been described, particularly in patients with patent foramen ovale.5 However, platypnoea was not our experience in the PAVM population, suggesting they may be able to compensate for acute falls in CaO 2 . The goal of the study was to quantify orthodeoxia and examine potential compensatory mechanisms to facilitate provision of appropriate information to PAVM patients.The study was ethically approved by the Hammersmith, Queen Charlotte's, Chelsea, and Acton Hospital Research Ethics Committee (LREC 2000/5764). Full methods are presented in the online supplementary data supplement. In all, 258 consecutive patients with CT-proven PAVMs were prospectively and newly recruited (2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013) and evaluated as described. Research letter on 28 April 2019 by guest. Protected by copyright.

CL. Exercise capacity reflects airflow limitation rather than hypoxaemia in patients with pulmonary arteriovenous malformations. QJM. 2019 In Press Exercise capacity reflects airflow limitation rather than hypoxaemia in patients with pulmonary arteriovenous malformations

Introduction and objectivesForced expiratory manoeuvres during lung function testing produce major pressure swings that are often overlooked by referring clinicians. Standard tests use a noseclip to prevent air leakage through the nose. Our goal was to examine how often the tests caused clinical sequelae such as nosebleeds in people with abnormal nasal and pulmonary vasculature due to hereditary haemorrhagic telangiectasia (HHT).MethodsWith ethical approval, self-reported migraine features and exacerbations were examined in HHT subjects with and without pulmonary AVMs, for a series of noninvasive and invasive investigations, using an unbiased online survey.ResultsOf 677 HHT-affected participants, 284 reported performing forced expiratory manoeuvres either with or without a noseclip in place. The median age was 54 years (interqurtile range 44–62) and the majority were female. All described nosebleeds: 130 (46%) experienced these at least daily, and a further 95 (33%) at least once per week. Only 1 of 253 (0.4%) reported nosebleeds were worse after finger oximetry measurements, compared to 53/282 (18.8%) after “blowing out hard without a noseclip” (chi-squared p < 0.0001). A higher proportion still reported nosebleeds were worse when a noseclip was used (66/192 (34.3%, p = 0.0003)). Similarly, migraine headaches (which are more frequent in people with HHT), were reported to be worse after forced expiratory manoeuvres both with (10/85 (11.7%) and without (11/105 (10.5%)) a noseclip, but not after oximetry or being weighed.ConclusionNoseclip use should be restricted in people already experiencing regular nosebleeds, and further pretest information may be required.

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