title: [Venous cross-sectional area: measured or calculated?].
abstract: OBJECTIVE
  The aim of this study was to compare measured versus calculated venous cross-sectional area in healthy subjects in a standing and a lying position with normal breath-ing and during Valsalva manoeuvre.
  
  
  METHODS
  Measurements were carried out in 30 venous segments (the common femoral vein CFV, the superficial femoral vein SFV, the greater saphenous vein GSV) of 5 healthy volunteers (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 during a standardised Valsalva manoeuvre. Venous diameters were measured from B-mode in longitudinal view while cross-sectional areas were planimetrically assessed from transverse B-mode as recorded on video (S-VHS). The mathematical calculation of areas followed the formula (0.5 diameter)2 x pi. All investigations were performed 3 times; mean values from these 3 measurements were used for further computation. Measurements were performed using the NIH Image 1.6 program.
  
  
  RESULTS
  Correlation coefficients r of the calculated 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 manoeuvre 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.
authors.affiliation: Abteilung Angiologie, Universitätsspital Basel/Schweiz.
authors.forename: C
authors.initials: C
authors.lastname: Jeanneret
authors.forename: K H
authors.initials: KH
authors.lastname: Labs
authors.forename: M
authors.initials: M
authors.lastname: Aschwanden
authors.forename: A
authors.initials: A
authors.lastname: Gehrig
authors.forename: K A
authors.initials: KA
authors.lastname: Jäger
mesh_terms: D000328:Adult; D005260:Female; D005268:Femoral Vein / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results; D015656:Respiratory Mechanics; D012501:Saphenous Vein / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D018616:Ultrasonography, Doppler, Duplex; D014636:Valsalva Maneuver