title: Comparison of thoracic epidural pressure in the sitting and lateral decubitus positions.
abstract: BACKGROUND
  The hanging drop technique identifies the epidural space using the negative pressure of this space. Although the hanging drop technique is popular at the thoracic level, there is still controversy on the negative epidural pressure at this level. The authors hypothesized that the epidural pressure is more consistently negative in the sitting position than in the lateral decubitus position at the thoracic level.
  
  
  METHODS
  This study compared the epidural pressures of 28 awake patients in the sitting (sitting group, n = 14) or lateral decubitus (lateral group, n = 14) position. The T5-T6 epidural pressure was measured using a closed pressure measurement system connected to a Tuohy needle.
  
  
  RESULTS
  All of the thoracic epidural pressures in the sitting group were negative (median, -5 mmHg; range, -18 to -1; mean, -7.2; SD, 6.3), in contrast to the lateral group (median, 5 mmHg; range, -4 to 13; mean, 5.1; SD, 4.4). The thoracic epidural pressure in the sitting group was significantly lower than in the lateral group (P < 0.001).
  
  
  CONCLUSIONS
  The thoracic epidural pressure is more negative in the sitting position than in the lateral decubitus position. These results suggest that the patient should be sitting when the hanging drop technique is used to identify the epidural space.
authors.affiliation: *Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Nam Su
authors.initials: NS
authors.lastname: Gil
authors.forename: Jong-Hwan
authors.initials: JH
authors.lastname: Lee
authors.forename: Seung Z
authors.initials: SZ
authors.lastname: Yoon
authors.forename: Yunseok
authors.initials: Y
authors.lastname: Jeon
authors.forename: Young Jin
authors.initials: YJ
authors.lastname: Lim
authors.forename: Jae Hyon
authors.initials: JH
authors.lastname: Bahk
mesh_terms: D000328:Adult; D000368:Aged; D000767:Anesthesia, Epidural / Q000379:methods*; D015170:Cerebrospinal Fluid Pressure / Q000502:physiology*; D004824:Epidural Space / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*