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Inspiratory conductance: an alternative index of the relationship between inspiratory effort and airflow, with potential for clinical use.
MedLine Citation:
PMID:  21501395     Owner:  NLM     Status:  Publisher    
Introduction and objectives:  There is a need for a measure of airways status that is easier for patients to use. If airflow is briefly occluded at the onset of inspiration the maximum rate of pressure fall, dP/dtmax can be measured. After the occlusion is released, the maximum rate of change of inspiratory airflow (dF/dtmax) can be measured and expressed as a ratio of dP/dtmax to generate an index of inspiratory conductance (IC). We explored the characteristics of IC as a preliminary step towards developing it as an easy-to-use alternative. Methods:  To measure IC we constructed an apparatus consisting of a pneumotachograph, a low-resistance spring-loaded valve and a pressure transducer to measure airflow and pressure drop at the start of inspiration. We studied 30 healthy adults to define the values of the index, its stability, and its response to external inspiratory resistive loads. Results:  Mean IC was 2.49(SD 0.96) Ls(-1) kPa(-1) , with no significant difference between men and women. The index was stable with a mean long-term variation of 11.25% around the normalised mean, compared with 2.1% for FEV1, and within-test variation < 5%. In response to external resistive loading IC fell in a non-linear but consistent manner from 3.96(0.32) to 0.96(0.10) Ls(-1) kPa(-1) across an added resistance range of 0-70 kPasL(-1) . Conclusion:  We showed that IC was measurable with a minimal need for subject participation. It was stable and reproducible in normal individuals and responded to added inspiratory resistive loads in a way that suggested it could be of clinical utility.
Stephen Allen; Ian Brown; Ahmed Khattab; Jeff Bagust
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-4-18
Journal Detail:
Title:  The clinical respiratory journal     Volume:  -     ISSN:  1752-699X     ISO Abbreviation:  -     Publication Date:  2011 Apr 
Date Detail:
Created Date:  2011-4-19     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101315570     Medline TA:  Clin Respir J     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
© 2011 Blackwell Publishing Ltd.
Department of Medicine, The Royal Bournemouth Hospital, Dorset, UK Department of Physiology, Anglo-European College of Chiropractic, Dorset, UK Centre of Postgraduate Medical Research and Education, Bournemouth University, Dorset, UK.
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