Document Detail


Influence of inspiratory flow rate and frequency on O2 cost of resistive breathing in humans.
MedLine Citation:
PMID:  3170427     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We examined the combined effect of an increase in inspiratory flow rate and frequency on the O2 cost of inspiratory resistive breathing (VO2 resp). In each of three to six pairs of runs we measured VO2 resp in six normal subjects breathing through an inspiratory resistance with a constant tidal volume (VT). One of each pair of runs was performed at an inspiratory muscle contraction frequency of approximately 10/min and the other at approximately 30/min. Inspiratory mouth pressure was 45 +/- 2% (SE) of maximum at the lower contraction frequency and 43 +/- 2% at the higher frequency. Duty cycle (the ratio of contraction time to total cycle time) was constant at 0.51 +/- 0.01. However, during the higher frequency runs, two of every three contractions were against an occluded airway. Because VT and duty cycle were kept constant, mean inspiratory flow rate increased with frequency. Careful selection of appropriate parameters allowed the pairs of runs to be matched both for work rate and pressure-time product. The VO2 resp did not increase, despite approximately threefold increases in both inspiratory flow rate and contraction frequency. On the contrary, there was a trend toward lower values for VO2 resp during the higher frequency runs. Because these were performed at a slightly lower mean lung volume, a second study was designed to measure the VO2 resp of generating the same inspiratory pressure (45% maximum static inspiratory mouth pressure at functional residual capacity) at the same frequency but at two different lung volumes. This was achieved with a negligibly small work rate.(ABSTRACT TRUNCATED AT 250 WORDS)
Authors:
D S Dodd; P W Collett; L A Engel
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  65     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1988 Aug 
Date Detail:
Created Date:  1988-11-22     Completed Date:  1988-11-22     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  760-6     Citation Subset:  IM    
Affiliation:
Thoracic Medicine Unit, Westmead Hospital, Sydney, Australia.
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MeSH Terms
Descriptor/Qualifier:
Adult
Airway Resistance*
Female
Humans
Lung Volume Measurements
Male
Muscle Contraction
Oxygen Consumption*
Pulmonary Ventilation*
Respiratory Muscles / physiology*
Tidal Volume

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


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