Document Detail


CPAP reduces inspiratory work more than dyspnea during hyperinflation with intrinsic PEEP.
MedLine Citation:
PMID:  7634880     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Hyperinflation with intrinsic positive end-expiratory pressure (PEEPi) loads the respiratory muscles and causes dyspnea in obstructive lung disease. Continuous positive airway pressure (CPAP) has shown some efficacy in reducing inspiratory work and dyspnea. However, in obstructive lung disease, inspiratory work and dyspnea may be increased by additional factors that may not be affected by CPAP. Therefore, to study the effects of hyperinflation with intrinsic PEEP and CPAP in isolation, we used a mechanical analog of airway closure to increase end-expiratory lung volume in normal subjects. In five subjects in whom inspiratory work was measured, increasing end-expiratory lung volume by 1 and 2 L increased inspiratory work per breath from 0.42 +/- 0.04 J to 1.17 +/- 0.15 J (p < 0.05 compared with baseline) and 1.58 +/- 0.22 J (p < 0.05 compared with baseline and to the lesser level of hyperinflation). Although CPAP reduced work per breath and per minute to levels not significantly different from baseline, it had little effect on dyspnea. In ten subjects hyperinflated to 2.4 +/- 0.12 L above FRC, breathing could be sustained 19.5 +/- 4.5 min before quitting the load. This was increased to 26.7 +/- 5.2 min by 10 cm H2O CPAP (p = 0.052). Inspiratory dyspnea was modestly reduced by CPAP during these endurance trials. We conclude that CPAP can substantially ameliorate the respiratory work load induced by hyperinflation with intrinsic PEEP. However, the effects of CPAP on dyspnea and endurance are more limited. This suggests that the limits to breathing at high lung volumes are related to factors in addition to respiratory muscle work, and that CPAP may be of more value in reducing the work than in relieving the distress of obstructive lung disease.
Authors:
H E Fessler; R G Brower; S Permutt
Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Chest     Volume:  108     ISSN:  0012-3692     ISO Abbreviation:  Chest     Publication Date:  1995 Aug 
Date Detail:
Created Date:  1995-09-14     Completed Date:  1995-09-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0231335     Medline TA:  Chest     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  432-40     Citation Subset:  AIM; IM    
Affiliation:
Division of Pulmonary and Critical Care Medicine, Johns Hopkins Asthma and Allergy Center, Baltimore, USA.
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MeSH Terms
Descriptor/Qualifier:
Adult
Analysis of Variance
Dyspnea / physiopathology,  therapy*
Electromyography
Expiratory Reserve Volume
Humans
Male
Positive-Pressure Respiration* / instrumentation,  methods,  statistics & numerical data
Positive-Pressure Respiration, Intrinsic / physiopathology,  therapy*
Reference Values
Spirometry / instrumentation,  methods,  statistics & numerical data
Transducers
Work of Breathing*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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