title: The epidural structure changes during deep breathing.
abstract: OBJECTIVE
  Previous experience has suggested that the insertion of an epidural catheter becomes easier when the patient takes a deep breath. The purpose of this study is to investigate the effects of respiration on the epidural space.
  
  
  METHODS
  We examined the epidural space using a flexible epiduroscope in 20 patients undergoing thoracic epidural anesthesia. A 17-gauge Tuohy needle was inserted using the paramedian technique and the loss-of-resistance method with 5 ml air. The epiduroscope was introduced into the epidural space via the Tuohy needle. Each patient was requested to take a deep breath when the epiduroscope was positioned at the needle tip and at approximately 10 cm cephalad from the needle tip within the epidural space. The changes in the epidural structure during deep breathing at each site were then measured.
  
  
  RESULTS
  In 80% of the patients, fatty tissue occupied the needle tip. Through the patients' maximal inspiration, the fatty tissue moved and a visible cavity expanded at the needle tip. Cross section area of the visible cavity at the needle tip was greater at the maximal inspiratory level than at the resting expiratory level: 12.1 +/- 6.7% vs 2.8 +/- 2.1% (mean +/- SD, P < 0.0001). In all patients, the visible cavity within the epidural space, which had already been expanded by injected air, became more expanded after maximal inspiration. Cross section area of the visible cavity at the 10 cm cephalad position was greater at the maximal inspiratory level than at the resting expiratory level: 20.6 +/- 10.0% vs 7.0 +/- 5.3% (P < 0.0001).
  
  
  CONCLUSIONS
  Epiduroscopy showed that deep breathing expanded the potential cavity of the epidural space. We suggest that the changes in the epidural structure during deep breathing may assist in the insertion of an epidural catheter.
authors.affiliation: Department of Anesthesiology, Jichi Medical School, Kawachi-gun, Tochigi-ken, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Igarashi
authors.forename: Y
authors.initials: Y
authors.lastname: Hirabayashi
authors.forename: R
authors.initials: R
authors.lastname: Shimizu
authors.forename: K
authors.initials: K
authors.lastname: Saitoh
authors.forename: H
authors.initials: H
authors.lastname: Fukuda
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D000368:Aged; D000767:Anesthesia, Epidural; D004724:Endoscopy; D004824:Epidural Space / Q000033:anatomy & histology* / Q000502:physiology*; D005260:Female; D005336:Fiber Optic Technology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012119:Respiration