title: An impedance threshold device increases blood pressure in hypotensive patients.
abstract: BACKGROUND
  The impedance threshold device (ITD-7) augments the vacuum created in the thorax with each inspiration, thereby enhancing blood flow from the extrathoracic venous systems into the heart.
  
  
  OBJECTIVE
  To the best of our knowledge, the ITD-7 has not previously been investigated in hypotensive patients in the emergency department (ED) or the prehospital setting. The objective of this study was to determine whether the ITD-7 would increase systolic arterial pressures in hypotensive spontaneously breathing patients.
  
  
  METHODS
  The ED study was a prospective, randomized, double-blind, sham control design. Patients with a systolic blood pressure ≤ 95 mm Hg were randomized to breathe for 10 min through an active or sham ITD. The primary endpoint was the change in systolic blood pressure measured non-invasively. The prehospital study was a prospective, non-blinded evaluation of the ITD-7 in hypotensive patients.
  
  
  RESULTS
  In the ED study, the mean ± standard deviation rise in systolic blood pressure was 12.9 ± 8.5 mm Hg for patients (n = 16) treated with an active ITD-7 vs. 5.9 ± 5.9 mm Hg for patients (n = 18) treated with a sham ITD-7 (p < 0.01). In the prehospital study, the mean systolic blood pressure before the ITD-7 was 79.4 ± 10.2 mm Hg and 107.3 ± 17.6 mm Hg during ITD-7 use (n = 47 patients) (p < 0.01).
  
  
  CONCLUSIONS
  During this clinical evaluation of the ITD-7 for the treatment of hypotensive patients in the ED and in the prehospital setting, use of the device significantly increased systolic blood pressure and was safe and generally well tolerated.
authors.affiliation: Department of Emergency Medicine, Hennepin County Medical Center, Minneapolis, Minnesota 55415, USA. Smith253@umn.edu
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Smith
authors.forename: Brent
authors.initials: B
authors.lastname: Parquette
authors.forename: David
authors.initials: D
authors.lastname: Lindstrom
authors.forename: Anja K
authors.initials: AK
authors.lastname: Metzger
authors.forename: Joni
authors.initials: J
authors.lastname: Kopitzke
authors.forename: Joseph
authors.initials: J
authors.lastname: Clinton
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D004311:Double-Blind Method; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007022:Hypotension / Q000628:therapy*; D008297:Male; D008397:Masks; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000295:instrumentation / Q000379:methods*; D011446:Prospective Studies; D012119:Respiration