Measured versus calculated venous cross sectional area.

Aim: The aim of this study was to compare measured versus calculated venous cross-sectional area in healthy subjects in a standing and a lying positio n with normal breath-ing and during Valsalva manoeuvre. Method: Measurement s were carried out in 30 venous segments (the common femoral vein GRV, the superficial femoral vein SN, the greater saphenous vein GSV) of 5 healthy v olunteers (4 female, 1 male) with a median age of 28.7 years (range 23.4-46 .7 years) in supine and standing position, while normally breathing and dur ing a standardised Valsalva manoeuvre. Venous diameters were measured from B-mode in longitudinal view while cross-sectional areas were planimetricall y assessed from transverse B-mode as recorded on video (SVHS). The mathemat ical calculation of areas followed the formula (0.5 diameter)(2) x pi. All investigations were performed 3 times; mean values from these 3 measurement s were used for further computation. Measurements were performed using the NIH Image 1.6 program. Results: Correlation coefficients r of the calculate d versus the measured venous area while normal breathing in standing and in lying subjects were: 0.92 and 0.82 in the CFV, 0.92 and 0.84 in the SFV as well as 0.98 and 0.97 in the GSV, respectively. During Valsalva manoeuvre in standing and lying subjects the correlation coefficients r amounted to: 0.94 and 0.93 in the CFV, 0.92 and 0.94 in the SFV as well as 0.99 and 0.98 in the GSV, respectively. Conclusions: In healthy volunteers measured and calculated venous cross-sectional area at rest and during Valsalva manoeuvr e correlate well. Correlation is numerically better in standing compared to lying subjects while normal breathing. Calculated venous area is accurate and can be used for further calculations.