Document Detail

Spontaneous Breathing Improves Shunt Fraction and Oxygenation in Comparison with Controlled Ventilation at a Similar Amount of Lung Collapse.
MedLine Citation:
PMID:  21918161     Owner:  NLM     Status:  Publisher    
Background:Spontaneous breathing (SB), when allowed during mechanical ventilation (MV), improves oxygenation in different models of acute lung injury. However, it is not known whether oxygenation is improved during mechanically unsupported SB. Therefore, we compared SB without any support with controlled MV at identical tidal volume (V(T)) and respiratory rate (RR) without positive end-expiratory pressure in a porcine lung collapse model.Methods:In 25 anesthetized piglets, stable lung collapse was induced by application of negative pressure, and animals were randomized to either resume SB or to be kept on MV at identical Vt (5 mL/kg; 95% confidence interval: 3.8 to 6.4) and RR (65 per minute [57 to 73]) as had been measured during an initial SB period. Oxygenation was assessed by blood gas analysis (n = 15) completed by multiple inert gas elimination technique (n = 8 of the 15) for shunt measurement. In addition, possible lung recruitment was studied with computed tomography of the chest (n = 10).Results:After induction of lung collapse, Pao(2)/FiO(2) decreased to 90 mm Hg (76 to 103). With SB, Pao(2)/FiO(2) increased to 235 mm Hg (177 to 293) within 15 minutes, whereas MV at identical Vt and RR did not cause any improvement in oxygenation. Intrapulmonary shunt by 45 minutes after induction of lung collapse was lower during SB (SB: 27% [24 to 30] versus MV: 41% [28 to 55]; P = 0.017). Neither SB nor MV reduced collapsed lung areas on computed tomography.Conclusions:SB without any support improves oxygenation and reduces shunt in comparison with MV at identical settings. This seems to be achieved without any major signs of recruitment of collapsed lung regions.
Laszlo Vimlati; Rafael Kawati; Göran Hedenstierna; Anders Larsson; Michael Lichtwarck-Aschoff
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-9-14
Journal Detail:
Title:  Anesthesia and analgesia     Volume:  -     ISSN:  1526-7598     ISO Abbreviation:  -     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-9-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  1310650     Medline TA:  Anesth Analg     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
From the *Department of Surgical Sciences, Anesthesiology and Critical Care Medicine, Uppsala University Hospital, Uppsala, Sweden; and.
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