[Influence of posture in respiratory function examination in obese subjects. II. In the patient with ventilation...

On earlier occasions healthy subjects, and normal weight cold patients and obese subjects not suffering from hypoventilation were subjected to respiratory function tests in different postures using the plethysmographic and helium dilution methods. This protocol was then applied to a series of obese patients with the functional characteristics of alveolar hypoventilation identified in preliminary functional tests. The study revealed: a) significant differences between plethysmographic and helium dilution findings; b) not significant volumetric differences produces by different postures (standing or squatting) especially as far as Total Lung Capacity and the main lung volume parameters are concerned. These results confirm the findings of others (Sharp et al., 1986) that diaphragmatic adjustment to changes in posture is inadequate in the obese with bronchial obstruction in whom absence of the fibre-length compensation phrenophrenic reflex and by the muscle flattening cause by the alveolar hyperinsufflation. On the basis of these data and others already published an index of "diaphragmatic passivity" based on the ratio between TLC in squatting and TLC in standing x 100 is proposed as an indicator of the lung volume available for use. This simple system would indicate the functional condition of the diaphragm and provide information for the functional assessment of patients proposed for rehabilitation treatment during follow-up.