title: Comparison of four ventilatory protocols for computed tomography of the thorax in healthy cats.
abstract: OBJECTIVE
  To identify ventilatory protocols that yielded good image quality for thoracic CT and hemodynamic stability in cats. Animals-7 healthy cats.
  
  
  METHODS
  Cats were anesthetized and ventilated via 4 randomized protocols (hyperventilation, 20 seconds [protocol 1]; single deep inspiration, positive inspiratory pressure of 15 cm H(2)O [protocol 2]; recruitment maneuver [protocol 3]; and hyperventilation, 20 seconds with a positive end-expiratory pressure of 5 cm H(2)O [protocol 4]). Thoracic CT was performed for each protocol; images were acquired during apnea for protocols 1 and 3 and during positive airway pressure for protocols 2 and 4. Heart rate; systolic, mean, and diastolic arterial blood pressures; blood gas values; end-tidal isoflurane concentration; rectal temperature; and measures of atelectasis, total lung volume (TLV), and lung density were determined before and after each protocol.
  
  
  RESULTS
  None of the protocols eliminated atelectasis; the number of lung lobes with atelectasis was significantly greater during protocol 1 than during the other protocols. Lung density and TLV differed significantly among protocols, except between protocols 1 and 3. Protocol 2 TLV exceeded reference values. Arterial blood pressure after each protocol was lower than before the protocols. Mean and diastolic arterial blood pressure were higher after protocol 3 and diastolic arterial blood pressure was higher after protocol 4 than after protocol 2.
  
  
  CONCLUSIONS
  Standardization of ventilatory protocols may minimize effects on thoracic CT images and hemodynamic variables. Although atelectasis was still present, ventilatory protocols 3 and 4 provided the best compromise between image quality and hemodynamic stability.
authors.affiliation: Department of Small Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061, USA. nguerrer@vt.edu
authors.forename: Natalia
authors.initials: N
authors.lastname: Henao-Guerrero
authors.forename: Carolina
authors.initials: C
authors.lastname: Ricco
authors.forename: Jeryl C
authors.initials: JC
authors.lastname: Jones
authors.forename: Virginia
authors.initials: V
authors.lastname: Buechner-Maxwell
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Daniel
mesh_terms: D000758:Anesthesia / Q000009:adverse effects; D000818:Animals; D002415:Cats / Q000502:physiology*; D006439:Hemodynamics; D008168:Lung / Q000000981:diagnostic imaging / Q000502:physiology; D008176:Lung Volume Measurements; D013902:Radiography, Thoracic / Q000379:methods*; D012121:Respiration, Artificial / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*