Document Detail

Imposed work of breathing during ventilator failure.
MedLine Citation:
PMID:  12036436     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Ventilators possess an anti-asphyxia valve that allows spontaneous breathing of ambient air during ventilator failure. This study examined the imposed work of breathing and pressure-time product of 8 critical care and 9 portable ventilators, using a laboratory simulation of spontaneous breathing during ventilator failure. METHODS: A test lung was modified to simulate spontaneous breathing with a tidal volume of 0.5 L and peak inspiratory flow of 60 L/min. A pneumotachograph and pressure tap were placed at the proximal airway between the breathing circuit and endotracheal tube. Flow was derived from the pressure drop across the pneumotachograph. Signals were amplified, integrated, and saved to a spreadsheet program, and imposed work of breathing and pressure-time product were calculated. Also measured were the inspiratory pressure required to open the anti-asphyxia valve (cracking pressure), time to cracking pressure, maximum negative inspiratory pressure, and time to maximum negative inspiratory pressure. RESULTS: For the critical care ventilators the mean +/- SD imposed work of breathing ranged from 213.07 +/- 3.53 to 890.63 +/- 0.88 mJ/L and the pressure-time product ranged from 2.67 +/- 0.01 to 13.37 +/- 0.01 cm H(2)O x s/L. For the portable ventilators the mean +/- SD imposed work of breathing ranged from 361.37 +/- 1.22 to 969.60 +/- 22.70 mJ/L and the pressure-time product ranged from 4.52 +/- 0.01 to 16.70 +/- 0.37 cm H(2)O x s/L. CONCLUSIONS: Spontaneous breathing during ventilator failure may impose work approximating the physiologic work of breathing. This imposed work may prevent effective breathing through the anti-asphyxia valve during mechanical ventilator failure due to electrical failure. These results reinforce the need to properly monitor mechanically ventilated patients and to have in place sufficient back-up power supplies and a method of manual ventilation.
Paul N Austin; Robert S Campbell; Jay A Johannigman; Richard D Branson
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Respiratory care     Volume:  47     ISSN:  0020-1324     ISO Abbreviation:  Respir Care     Publication Date:  2002 Jun 
Date Detail:
Created Date:  2002-05-30     Completed Date:  2002-08-02     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  7510357     Medline TA:  Respir Care     Country:  United States    
Other Details:
Languages:  eng     Pagination:  667-74     Citation Subset:  IM    
Department of Nurse Anesthesia, Graduate School of Nursing, Uniformed Services University of the Health Sciences, Silver Spring, Maryland 20910, USA.
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MeSH Terms
Equipment Design
Equipment Failure
Materials Testing
Models, Biological
Respiration, Artificial* / adverse effects,  instrumentation
Ventilators, Mechanical* / adverse effects
Work of Breathing*

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