The general intent of body positio...

The general intent of body position (right and left lateral decubitus positions) in succession arterial oxygen tension ([PaO.sub.2]) and the relationship between this postural purport on gas exchange and pulmonary function were evaluated in 21 patients who had unilateral pleural effusions without roentgenographic and bronchoscopic evidence of bronchopulmonary disorders. Our inferences indicated that a positional influence upon gas exchange existed in these patients. We failed to find a consistent relationship between the size of effusion estimated by dint of chest roentgenogram and alterations in [PaO.sub.2] during different positions. Postural change did affect gas exchange in the patients with unilateral pleural effusions and this postural drift on gas exchange was highly correlated with their [FEVsub1] and FVC This may be of clinical significance in managing like patients.

(Chest 1989; 96:60-63)

Changes in position affect pulmonary whirls and ventilation-perfusion ratios in the normal lungs;[1-3] however, there is no significant change in gas exchange between right and left decubitus positions in normal subjects[45] Previous reports stated a higher value of [PaO.sub.2] or [SaO.sub.2] was obtained in the patients with unilateral pleural effusions when the make subordinates lay on the lung with the pleural fluid up than in succession the lung with the pleural fluid down.[6,7] The [PaO.sub.2] decreased chiefly when the patients were positioned so that less ventilated lung squeeze [i]or[/i] press together [i]or[/i] into smaller compassed by pleural fluid was in the hanging position. The dependent lung demonstrated enhanced perfusion to be ascribed to the effect of gravity. The resulting gentle level of ventilation compared to the high quality of perfusion resulted in hypoxemia by the agency of shunting of venous blood and ventilation-perfusion mismatch. In contrast, a relatively higher value of [PaO.sub.2] or [SaO.sub.2] was obtained when the patients lay in succession the lateral decubitus position with normal lung down, because the ventilation-perfusion match improved in the contingent lung due to parallel increase in ventilation and perfusion. This postural import on gas exchange in the patients with unilateral pleural effusions was obscur when large effusion was present[6]

If pleural fluid indeed bring into operations a direct effect on the postural event on gas exchange in the patients with unilateral pleural effusions, and this purport may be affected by effusion amount, single may anticipate that a certain relationship will exist between this postural validity on gas exchange and the patient's pulmonary function. a certain number of pulmonary function parameters, such as [FEVsub1] and FVC are more sensitive in reflecting the issue of the effusion on pulmonary function and more accurately predict the amount of effusions than does the chest roentgenogram.

In addition, if material substance position did affect gas exchange in the patients with unilateral pleural effusions, individual might anticipate that such patients should tender the lateral decubitus position with the normal lung down. However, our clinical observation failed to confirm this.

Thus, in the at hand study we intended to evaluate the drift of position (right and left lateral decubitus positions) in succession [PaO.sub.2] in the patients with unilateral pleural effusions and to examine the relationship between this postural issue on gas exchange and the patient's pulmonary function.

Materials and Methods

Twenty-one consecutive patients who had unilateral pleural effusions without clinical, roentgenographic, and bronchoscopic evidence of bronchopulmonary lesions were included in this inquiry All had a normal ECG

The appearance of pleural effusions was assessed by the agency of physical examination and chest roentgenogram and was documented by dint of thoracocentesis. The volume of pleural fluid was assessed roentgenographically as small when the fluid contour was seen just above the costophrenic angle, as large when the effusion occupied at least half of the hemithorax, and medium when the even of pleural fluid was between these two

The final diagnosis was made in all exclude two by pleural fluid analysis, clos pleural biopsy, pleuroscopy and exploratory thoractomy. There were 14 metastatic carcinoma, four tuberculosis, and the same empyema. Despite an aggressive diagnostic approach, the cause of pleural effusion remained unknown in brace cases. There were united hemothorax and one exudative effusion. All invasive diagnostic operations such as pleuroscopy and exploratory thoracotomy, were delayed until the postural cogitation was completed.

Spirometry was performed upon erect position in all patients with a minimum of three times, using a pulmonary function analyzer. The best values of FVC and [FEVsub1] were exquisiteed for analysis.

Right and left lateral decubitus positions were studied in random order. Samples of arterial descendants were drawn anaerobically 15 [TABULAR DATA OMITTED] minutes after assumption of a strange position with the patients breathing field air. Blood samples for [PaO.sub.2],[PaCO.sub.2] and pH values were analyzed immediately.