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Tidal Volume Variability During Airway Pressure Release Ventilation: Case Summary and Theoretical Analysis.
MedLine Citation:
PMID:  22348242     Owner:  NLM     Status:  Publisher    
Airway pressure release ventilation (APRV) is used in the management of patients with severe or refractory respiratory failure. In addition to reversal of inspiratory/expiratory ratios, this pressure control mode also allows unrestricted spontaneous breathing. Spontaneous tidal volumes as well as tidal volumes resulting from transition between high and low airway pressures are uncontrolled. There are limited data on the within patient variation of actual tidal volumes and the safety of these modes. The authors present a patient with severe ARDS who was managed with biphasic modes (APRV and BiPAP). Serial tidal volume measurements showed tidal volume ranged from 4 to 12 mL/kg predicted body weight. CT scan images and chest radiographs obtained before and following APRV showed lung parenchyma changes that may be related to ventilator induced lung injury. We also present a mathematical model that is useful for simulating APRV and demonstrating the issues related to volume delivery for mandatory breaths during the transition between the two pressure levels. A key finding of this analysis is the interdependence of release volume, autoPEEP and T Low time setting. Furthermore, it is virtually impossible to target a specific PaCO₂ with a desired level VT and autoPEEP in a passive model, emphasizing the importance of spontaneous breathing with this mode. This case report suggests caution when using these modes and that end-inspiratory lung volumes and tidal volumes should be limited to avoid lung injury. The important point of this case study and model analysis is that the application of APRV is more complex than it appears to be. It requires a lot more knowledge and skill than may be apparent from descriptions in the literature.
Madhu Sasidhar; Robert L Chatburn
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-2-17
Journal Detail:
Title:  Respiratory care     Volume:  -     ISSN:  0020-1324     ISO Abbreviation:  -     Publication Date:  2012 Feb 
Date Detail:
Created Date:  2012-2-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7510357     Medline TA:  Respir Care     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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