McKenzie D K, Gandevia S C, Gorman R B, Southon F C
Department of Respiratory Medicine, Prince Henry Hospital, University of New South Wales, Sydney, Australia.
Thorax. 1994 Jul;49(7):634-8. doi: 10.1136/thx.49.7.634.
Clinical tests of diaphragmatic strength are limited by the wide normal variation in maximal pressure which result, in part, from changes in diaphragmatic length. During relaxation at different lung volumes diaphragmatic length (LDI) can be estimated from the length of the zone of apposition (LZapp) and the transverse diameter of the rib cage (DRC). A study was carried out in two subjects using sequential digital radiography at six frames/second to determine whether these relations apply during maximal respiratory efforts which distort the rib cage and diaphragm.
The length of the anteroposterior contour of the diaphragm and DRC were determined by curve fitting. LZapp was measured with a millimetre rule.
A significant correlation was found between LDI and LZapp during both maximal inspiratory and expulsive manoeuvres (R2 = 0.88 and 0.52). LDI was estimated from the measurements of LZapp and DRC using a multiple regression equation derived from measurements during static relaxation. Despite the complex dynamic events at the onset of these "static" manoeuvres, actual LDI correlated strongly with derived LDI using all data for the two manoeuvres in each subject (R2 = 0.95 and 0.84). Measurements with ultrasonography (12 cm linear probe) and magnetometers confirmed the changes in LZapp and DRC during inspiratory and expulsive efforts.
Non-invasive measurements of LZapp and DRC can be used to derive an accurate estimate of diaphragmatic length under dynamic conditions.
膈肌力量的临床测试受到最大压力正常变异范围较宽的限制，这部分是由膈肌长度的变化所致。在不同肺容量下放松时，膈肌长度（LDI）可根据贴附区长度（LZapp）和胸廓横径（DRC）来估算。在两名受试者中进行了一项研究，使用每秒6帧的连续数字放射成像技术，以确定在使胸廓和膈肌变形的最大呼吸努力过程中，这些关系是否适用。
通过曲线拟合确定膈肌前后轮廓的长度和DRC。用毫米尺测量LZapp。
在最大吸气和呼气动作过程中，LDI与LZapp之间均发现显著相关性（R2 = 0.88和0.52）。使用在静态放松期间测量得出的多元回归方程，根据LZapp和DRC的测量值估算LDI。尽管在这些“静态”动作开始时存在复杂的动态事件，但在每个受试者中，使用这两个动作的所有数据，实际LDI与推导的LDI之间仍存在强烈相关性（R2 = 0.95和0.84）。超声检查（12厘米线性探头）和磁力计测量结果证实了吸气和呼气努力过程中LZapp和DRC的变化。
LZapp和DRC的非侵入性测量可用于在动态条件下准确估算膈肌长度。
