title: Transesophageal echocardiographic evaluation during negative-pressure ventilation using the Hayek oscillator.
abstract: OBJECTIVE
  To evaluate the effects of negative-pressure ventilation (NPV) on hemodynamics using the Hayek oscillator (Breasy Medical Equipment, London, UK) and to determine whether the oscillation frequency can modify the hemodynamics, assessed by transesophageal echocardiography (TEE).
  
  
  METHODS
  A prospective study.
  
  
  METHODS
  A university hospital.
  
  
  METHODS
  Eleven American Society of Anesthesiologists class I patients undergoing orolaryngeal surgery.
  
  
  METHODS
  The ultrasound probe was inserted under general anesthesia. After baseline measurements were determined during spontaneous breathing, the frequency was changed from 30 to 60 to 120 cycles/min, consecutively. The left ventricular end-diastolic area (LVEDA), end-systolic area (LVESA), fractional area change (LVFAC), and end-systolic wall stress (ESWS) were determined. The velocities of the pulmonary artery (PA) flow, pulmonary venous (PV) flow, and transmitral flow were measured by pulsed Doppler techniques.
  
  
  RESULTS
  PaO2 increased and PaCO2 decreased significantly. NPV caused a significant increase in the LVEDA, whereas it did not significantly change the PA velocity. ESWS, an index of afterload, remained unchanged.
  
  
  CONCLUSIONS
  The authors conclude that NPV using the Hayek oscillator induces an increase in the LVEDA without any changes in PA velocity, suggesting increased transmural pressure rather than increased preload, and that the three different frequencies do not modify the effects on the hemodynamics.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, Nippon Medical School, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shiga
authors.forename: S
authors.initials: S
authors.lastname: Takeda
authors.forename: K
authors.initials: K
authors.lastname: Nakanishi
authors.forename: T
authors.initials: T
authors.lastname: Takano
authors.forename: A
authors.initials: A
authors.lastname: Sakamoto
authors.forename: R
authors.initials: R
authors.lastname: Ogawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D017548:Echocardiography, Transesophageal; D005260:Female; D006439:Hemodynamics; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015919:Ventilators, Negative-Pressure; D016277:Ventricular Function, Left