Recumbent deoxygenation in mild/moderate liver cirrhosis: The "clinodeoxia". The ortho-clino paradigm

Background: While the effects of postural change on arterial oxygenation have been well documented in normal subjects, and attributed to the relationship of closing volume (CV) to the tidal volume, in liver cirrhosis such postural changes have been evaluated mainly in a rare, peculiar clinical end-stage condition which is characterized by increased dyspnea shifting from supine to upright position ("platypnea"). The latter is associated with worsening of PaO₂ ("orthodeoxia"). We evaluated the effects of postural changes on arterial oxygenation in patients affected by mild/moderate liver cirrhosis. Methods: We performed pulmonary function tests and arterial blood gas evaluation in sitting and supine positions in 22 patients with mild/moderate liver cirrhosis, biopsy-proved, and 22 matched non-smokers control subjects. Results: Recumbency elicited a decrease of PaO₂ (Δ(sup-sit)PaO₂) in 19 out of 22 controls and in all but one cirrhotics. The magnitude of this postural change was significantly (p = 0.04) greater in cirrhotics (9.6 ± 5.3%) compared to controls (6.7 ± 3.7%). In the subset of cirrhotics younger than 60 yrs and with PaO₂ greater than 80 mmHg in sitting position, the Δ(sup-sit)PaO₂ in recumbency further increased to 12 ± 5.8%, significantly (p = 0.014) greater than in same subgroup of controls (7.1 ± 3.8%). Conclusions: In mild/moderate liver cirrhosis the postural variations in PaO₂ follow the normal trends, but are of greater magnitude probably as a consequence of hypoventilated units of lung for postural and disease-linked tidal airway closure, resulting in more pronounced recumbent hypoxemia (" clinodeoxia").