S42 Effect of iron deficiency on oxygen transport in hypoxaemic patients: implications for haemodynamics and clinical management

Background Oxygen transport in the blood depends not only upon oxygen partial pressure (or saturation, SaO2), but also the concentration of haemoglobin to which oxygen binds, and blood volume in any given period. In current clinical studies and guidelines, it is rare for these components to be discussed together. Methods An observational cohort study was performed in 165 consecutive unselected patients with pulmonary arteriovenous malformations, including 98 before and after embolisation. 159 (96%) had hereditary haemorrhagic telangiectasia (HHT). Prior to statistical analyses, patients were stratified by self-reported exercise tolerance, and serum iron/ferritin. Results Patients were aged 17–87 (median 49)ys, with median SaO2 95% (range 78·5–99%) Many had biochemical/haematinic evidence of iron deficiency, predominantly attributable to HHT-blood loss, but several had undergone venesection for secondary polycythaemia, as recommended in current UK haematological guidelines. Haemoglobin ranged from 7.7–20.9g/dl (median 14.1g/dl), and was higher in patients with lower SaO2: For every 1% fall in SaO2, haemoglobin rose on average, by 0·82g/dl (p Conclusions Low oxygen carriage per unit volume, and not low PaO2/SaO2 per se, are predictors of impaired exercise tolerance in PAVM patients.