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
IntroductionAssessment of performance status is an important component of clinical management of patients with pulmonary arteriovenous malformations (PAVMs). Usual methods are time-consuming and insensitive to variations within normal or supranormal exercise capacity.MethodsThe Veterans Specific Activity Questionnaire (VSAQ) was modified to facilitate completion by patients independently. Patient-reported activity limitations were converted to the Medical Research Council (MRC) Dyspnoea Scale, New York Heart Association (NYHA) classification and metabolic equivalents (METs) in which 1 MET equals the consumption of 3.5 mL O2 per kilogram of body weight per minute.ResultsThe study population consisted of 71 patients with PAVMs aged 20–85 (median 52) years. Oxygen saturation (SaO2) was 80%–99.5 % (median 96%), and haemoglobin was 73–169 g/L in women and 123–197 g/L in men (p<0.0001). Arterial oxygen content (CaO2) (1.34 × [haemoglobin × SaO2]/100) was maintained unless iron deficiency was present. Most patients (49/71, 69%) did not need to stop until activities more energetic than walking briskly at 4 mph were achieved (6.4 km per hour, VSAQ >5, MRC Dyspnoea Scale 1 or 2, NYHA class I). SaO2 was inversely associated with the MRC Dyspnoea Scale and NYHA class, but not the VSAQ. Raw VSAQ scores captured a marked difference between men and women. METs were also higher in men at 3.97–15.55 (median 8.84) kcal/kg/min, compared with 1.33–14.4 (median 8.25) kcal/kg/min (p=0.0039). There was only a modest association between METs and SaO2 (p=0.044), but a stronger association between METs and haemoglobin (p =0.001). In crude and sex-adjusted regression, the CaO2 was more strongly associated with METs than either SaO2 or haemoglobin in isolation.ConclusionThe VSAQ, capturing patient-reported outcome measures, is an efficient and quantifiable measure of exercise capacity that can be readily employed in clinical services particularly where patients have normal to high exercise tolerance. In the PAVM population, exercise capacity reflects haemoglobin and CaO2 more than SaO2, even where SaO2 measurements are low.
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What is already known: Alongside age, pre-existing medical conditions are perceived negatively during triage assessments, particularly if rare, and/or theoretically expected to influence cardiorespiratory risk; Anaesthetists use cardiopulmonary exercise testing to categorise patients to higher and lower risk independently to diagnostic labels, but this is not feasible in acute settings; Pulmonary arteriovenous malformations are an exemplar of a condition where, due to expected or measured abnormalities (hypoxaemia-low PaO2 SpO2), poor physiological capacity might be predicted.
What this study adds Neither age nor usual SpO2 predicted lower/higher risk categories by anaerobic threshold, but haemoglobin-dependent indices of oxygen delivery to the tissues were associated with higher risk, offering opportunities for improvement by attention to anaemia and aerobic conditioning; Baseline exercise tolerance may override age and diagnostic labels in triage settings: the 13point VSAQ Veterans Specific Activity Questionnaire (VSAQ) is suggested as a rapid screening tool for cardiorespiratory risk assessment.Abstract 1 2 BACKGROUND: Rapid triaging, as in the current COVID-19 pandemic, focuses on age and pre-existing 3 medical conditions. In contrast, preoperative assessments use cardiopulmonary exercise testing (CPET) 4 to categorise patients to higher and lower risk independent of diagnostic labels. Since CPET is not 5 feasible in population-based settings, our aims included evaluation of a triage/screening tool for 6 cardiorespiratory risk. 7 METHODS: CPET-derived anaerobic thresholds were evaluated retrospectively in 26 patients with 8 pulmonary arteriovenous malformations (AVMs) who represent a challenging group to risk-categorise. 9 Pulmonary AVM-induced hypoxaemia secondary to intrapulmonary right-to-left shunts, anaemia from 10 underlying hereditary haemorrhagic telangiectasia and metabolic equivalents derived from the 13-point 11 Veterans Specific Activity Questionnaire (VSAQ) were evaluated as part of routine clinical care. Pre-12 planned analyses evaluated associations and modelling of the anaerobic threshold and patient-specific 13 variables. 14 RESULTS: In the 26 patients (aged 21-77, median 57 years), anaerobic threshold ranged from 7.6-24.5 15 (median 12.35) ml.min -1 kg -1 and placed more than half of the patients (15, 57.7%) in the >11 ml.min -16 1 kg -1 category suggested as "lower-risk" for intra-abdominal surgeries. Neither age nor baseline SpO2 17 predicted anaerobic threshold, or lower/higher risk categories, either alone or in multivariate analyses, 18 despite baseline oxygen saturation (SpO2) ranging from 79 to 99 (median 92)%, haemoglobin from 108 19 to 183 (median 156)g.L -1 . However, lower haemoglobin, and particularly, arterial oxygen content and 20 oxygen pulse were associated with increased cardiorespiratory risk: Modelling a haemoglobin increase 21 of 25g.L -1 placed a further 7/26 (26.9%) patients in a lower ...
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