[Methodical aspects of pneumatic segment plethysmography. III. Measuring tourniquet problems].
The question, to which extent utilization of different plethysmographic cuffs influenced the assessment of volume changes, was examined in 40 healthy individuals as well as by means of an experimental model. It could be shown that plethysmographic results varied significantly according to the design of the cuffs: 1.a) Utilization of short (19.5 cm) cuffs that did not cover the entire thigh circumference resulted in significantly lower arterial inflow and pressure-dependent venous capacity measurements as compared to long cuffs (48.8 cm). b) This result was confirmed by use of a newly developed "calibration-cylinder" demonstrating that use of the short cuff showed only 62.2% of the true volume change, use of the long cuff, however, 89.6%. Deficiency of thigh contact is discussed as possible etiologic factor for this difference. 2. The cover material of the cuff also influenced the results significantly since results could be improved from 62.2% to 86.9% (short cuff) and from 89.6% to 95.1% (long cuff) by use of double layer non-compliant cloth. The reason for this finding is thought to be the compliance of conventional cloth. 3. Comparison of two cuffs with identical shape and dimensions resulted in significantly lower volume changes using hard stiff rubber as compared to soft compliant rubber. These findings suggest some recommendations for optimal design of plethysmographic cuffs. Cuffs should not underestimate volume changes obtained with the "calibration-cylinder" by more than 10%.
D000328:Adult; D006801:Humans; D007866:Leg / Q000098:blood supply; D010991:Plethysmography / Q000295:instrumentation*
Methodische Aspekte zur pneumatischen Segmentplethysmographie. III. Das Messmanschettenproblem