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- Title
Assessment of airway closure from deflation lung volume-pressure curve: sigmoidal equation revisited.
- Authors
Bayle, Frédérique; Guérin, Claude; Debord, Sophie; Badet, Michel; Lemasson, Stéphane; Poupelin, Jean-Charles; Richard, Jean-Christophe; Bayle, Frédérique; Guérin, Claude; Lemasson, Stéphane
- Abstract
<bold>Objective: </bold>To assess a sigmoidal equation for describing airway closure.<bold>Design: </bold>Experimental study.<bold>Setting: </bold>University laboratory.<bold>Participants: </bold>Eight piglets mechanically ventilated on zero end-expiratory pressure (ZEEP).<bold>Interventions: </bold>Control and lung saline lavage.<bold>Measurements and Results: </bold>Lungs were inflated up to transpulmonary pressure of 30 cmH(2)O at constant flow (0.12l s(-1)) then deflated at the same flow rate up to the point at which oesophageal pressure was constant, which was assumed to represent complete airway closure. The deflation volume-transpulmonary pressure curve was fitted to: (1) a sigmoidal equation focusing on inflexion point and pressure at maximal compliance increase and (2) an exponential equation above an inflexion point determined by eyeballing. Data deviate from the exponential equation at the point of airway closure onset. The zero-volume intercept was determined. Complete airway closure was reached at -8.3+/-3.5cmH(2)O in control conditions and at -1.3+/-3.7 cmH(2)O after lavage (p < 0.05). Between control and lavage, onset of airway closure was 3.0+/-1.9 vs. 6.0+/-2.8 cmH(2)O (p <0.05), inflexion point 3.2+/-1.8 vs. 7.7+/-2.6 cmH(2)O (p <0.001), pressure at maximal compliance increase -1.9+/-0.7 vs. -0.03+/-2.1cmH(2)O (p <0.05) and zero-volume intercept -1.5+/-1.4 vs. 0.3+/-2.3cmH(2)O (p <0.05).<bold>Conclusions: </bold>During mechanical ventilation airways stay open and close around ZEEP in control but are closed above ZEEP after lavage. Inflexion point might reflect onset of airways closure in control. Pressure at maximal compliance increase was not a marker of complete airways closure. In control and lavage, pressure at maximal compliance increase and zero-volume intercept were reasonably equivalent.
- Subjects
FRANCE; LUNGS; RESPIRATION; AIRWAY (Anatomy); RESPIRATORY organs; ARTIFICIAL respiration; BRONCHOALVEOLAR lavage; ANIMAL experimentation; ADULT respiratory distress syndrome; RESPIRATORY obstructions; SWINE; TRACHEA intubation; STATISTICAL models; LUNG volume measurements
- Publication
Intensive Care Medicine, 2006, Vol 32, Issue 6, p894
- ISSN
0342-4642
- Publication type
journal article
- DOI
10.1007/s00134-006-0160-3