The object that presented itself to the eyes of the astonished clerk, was a boy – a wonderfully fat boy – habited as a serving lad, standing upright on the mat, with his eyes closed as if in sleep.
– Dickens [1]
In this issue of the European Respiratory Journal, Held et al. [2] report on 18 patients with severe pulmonary hypertension due to alveolar hypoventilation, who were markedly improved after 3 months of noninvasive bi-level positive-pressure ventilation (NIPPV). Mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) were 50 mmHg and 6–7 Wood units, respectively, at baseline, and decreased to 30 mmHg and 3–4 Wood units with NIPPV; this was accompanied by improved catherisation and echocardiographic indices of right ventricular (RV) function. The N-terminal pro-brain natriuretic peptide (NT-proBNP) levels also decreased, and the 6-min walk distance (6MWD) improved by 80 m. These results are in striking contrast with the “borderline” (mPAP 20–25 mmHg) or mild (mPAP 25–30 mmHg) pulmonary hypertension generally seen, but with rare exceptions, in patients with respiratory conditions. Borderline or mild pulmonary hypertension due to respiratory conditions is of uncertain clinical relevance, exhibits slow progression controlled by supplemental oxygen and is refractory to drugs targeting the pulmonary circulation [3, 4].
12 of the 18 patients reported by Held et al. [2] fulfilled the criteria of obesity hypoventilation syndrome (OHS), defined by a combination of awake hypercapnia (arterial carbon dioxide tension (PaCO2) >45 mmHg), a body mass index >30 kg·m−2 and exclusion of other causes that could account for hypoventilation, such as lung or neuromuscular disease [5, 6]. Three of the OHS patients had concomitant chronic obstructive pulmonary disease (COPD) and five patients had COPD without obesity. …
