Abstract | OBJECTIVE: DESIGN: Prospective, experimental study. SETTING: Research laboratory at a veterinary hospital. SUBJECTS: Female sheep weighing 48 +/- 2 kg. INTERVENTIONS: In five saline-lavaged sheep, we acquired whole-lung computed tomography scans, oxygenation, static elastance, and dynamic respiratory resistance and elastance at end-expiratory pressure levels of 7.5-20 cm H2O. MEASUREMENTS AND MAIN RESULTS: As end-expiratory pressure increased, computed tomography-determined alveolar recruitment significantly increased but was accompanied by significant alveolar overdistension at 20 cm H2O. An optimal range of end-expiratory pressures (15-17.5 cm H2O) was identified where alveolar recruitment was significantly increased without significant overdistension. This range corresponded to the end-expiratory pressure levels that maximized oxygenation, minimized peak-to-peak ventilation pressures, and minimized indexes reflective of the mechanical heterogeneity (e.g., frequency dependence of respiratory resistance and low-frequency elastance). Static elastance did not demonstrate any significant pressure dependence or reveal an optimal end-expiratory pressure level. CONCLUSIONS: We conclude that dynamic mechanics are more sensitive than static mechanics in the assessment of the functional trade-off of recruitment relative to overdistension in a sheep model of lung injury. We anticipate that monitoring of dynamic respiratory resistance and elastance ventilator settings can be used to optimize ventilator management in acute lung injury.
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Authors | Carissa L Bellardine Black, Andrew M Hoffman, Larry W Tsai, Edward P Ingenito, Bela Suki, David W Kaczka, Brett A Simon, Kenneth R Lutchen |
Journal | Critical care medicine
(Crit Care Med)
Vol. 35
Issue 3
Pg. 870-8
(Mar 2007)
ISSN: 0090-3493 [Print] United States |
PMID | 17255854
(Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
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Chemical References |
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Topics |
- Airway Resistance
(physiology)
- Animals
- Bronchoalveolar Lavage Fluid
- Disease Models, Animal
- Female
- Image Processing, Computer-Assisted
- Imaging, Three-Dimensional
- Lung Compliance
(physiology)
- Oxygen
(blood)
- Positive-Pressure Respiration
(adverse effects)
- Pulmonary Alveoli
(physiopathology)
- Pulmonary Atelectasis
(physiopathology)
- Respiratory Distress Syndrome
(physiopathology)
- Respiratory Mechanics
(physiology)
- Sheep
- Tomography, X-Ray Computed
- Transducers, Pressure
- Ventilation-Perfusion Ratio
(physiology)
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