Background: Lateral decubitus position is poorly tolerated by heart failure patients.
Study objectives: To evaluated pulmonary function and lung diffusion in heart failure patients in the following five body positions: sitting, prone, supine, and left and right decubitus.
Setting: Heart failure unit of a university hospital.
Subjects: We studied 14 chronic heart failure patients in New York Heart Association class III and 14 healthy volunteers.
Measurements and results: After 15 min of a selected position, subjects were evaluated by a discomfort scale, ear oximetry, and pulmonary function, which included FEV1, FVC, vital capacity (VC), alveolar volume, and diffusing capacity of the lung for carbon monoxide (Dlco) with subcomponent membrane resistance (DM) and capillary volume. In healthy subjects, we observed a reduction of Dlco and capillary volume in both lateral decubiti. Some discomfort was documented in both lateral decubiti when selected positions were compared with the sitting position. In the sitting position, pulmonary function suggested slight restriction ([mean ± SD] FVC, 89.8 ± 22.3% predicted; FEV1, 84.7 ± 16.9% predicted, VC, 88.6 ± 21.5% predicted; and FEV1/VC, 74 ± 7) with low Dlco (73 ± 19% predicted). Compared with sitting, lung mechanics were unchanged in prone and supine positions; FEV1, FVC, and FEV1/VC were lower when patients were lying on their side, with unchanged alveolar volume and VC. Dlco was similar when comparing sitting, prone, and supine positions, and it was lower in lateral decubitus because of the lower capillary volume (vs sitting) and DM (vs prone and supine). Body position-related FVC and Dlco reduction were greatest in the largest hearts (ΔFVC and ΔDlco vs left ventricle diastolic volume R = 0.524, p < 0.05 and R = 0.630, p < 0.02, respectively; ΔFVC and ΔDlco vs cardiothoracic index R = 0.539, p < 0.05 and R = 0.685, p < 0.01, respectively).
Conclusions: In heart failure, lateral decubitus airway obstruction and lung diffusion impairment become greater as heart dimensions increase.