Chest
Journal ArticleLung Mechanics in Sitting and Horizontal Body Positions
Section snippets
MATERIAL AND METHODS
The study was performed on ten healthy male volunteers with a mean age (±SD) of 31.4 ± 3.5 years, mean vital capacity of 5.34 ± 0.38 L (105 ± 9.5 percent predicted), and mean FEV1 of 4.28 ± 0.41 (106 ± 11.4 percent predicted).10 Measurements were made in the sitting, supine, and right and left lateral positions, in a random sequence. A pillow was used when subjects were tested in lateral postures to keep the head horizontal.
Esophageal pressure (Pes) was measured with the esophageal balloon
Lung Volumes
Average values (±SE) of VC and ERV in the ten subjects in four body positions are presented in Table 1. VC decreased by about 5 percent from sitting to lateral positions, the difference being statistically significant (p<0.05). There was no significant difference between right and left lateral or between the sitting and supine positions.
The ERV decreased by about 22 percent when moving from sitting to lateral positions and by 50 percent from sitting to supine. These differences were
DISCUSSION
In agreement with previous studies,13, 14, 15 we found a small reduction of VC in the horizontal postures, which can probably be attributed to increased thoracic blood volume.16 Also in agreement with previous reports,13, 14, 15, 16 the ERV decreased progressively when shifting from sitting to lateral and then to supine position. This reflects mainly gravitational effects, which cause a cephalad displacement of the diaphragm due to increased abdominal pressure in the horizontal postures,
ACKNOWLEDGMENTS:
The authors thank Mr. H. Ghezzo, who performed the statistical analyses of the data, and Mr. S. Filiatrault for technical assistance.
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Supported by Medical Research Council of Canada and NIH grant HL27617.
Manuscript received July 12; revision accepted October 5