Rib cage and abdominal restrictions have different effects on lung mechanics

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Abstract
Effects of a variety of restrictive procedures on lung mechanics were studied in 8 healthy men. Rib cage restriction decreased total lung capacity (TLC) by 43% and significantly increased elastic recoil and maximum expiratory flow (MEF). Subsequent immersion of 4 subjects with rib cage restriction resulted in no further change in either parameter; shifts of blood volume did not reverse recoil changes during rib cage restriction. Abdominal restriction decreased TLC by 40% and increased MEF and elastic recoil but recoil was increased significantly less than was the case with rib cage restriction. At a given recoil pressure, MEF was less during rib cage restriction than during abdominal restriction or no restriction. Measurements of the unevenness of inspired gas distribution by the single breath N2 technique showed increased unevenness during rib cage restriction, which was significantly greater than that during abdominal restriction. Lung volume restriction induces changes in lung function but the nature of these changes depends on how the restriction is applied and therefore cannot be ascribed to low lung volume breathing per se.