Linked Life Data

8575580

Source:http://linkedlifedata.com/resource/pubmed/id/8575580

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
9
pubmed:dateCreated
1996-3-14
pubmed:abstractText
Diaphragm strength can be assessed by measurement of transdiaphragmatic pressure (Pdi) in response to stimulation of the phrenic nerves. The length-tension relationship of the diaphragm can be studied by measuring twitch Pdi over the range of lung volume. Previous studies of the relationship between lung volume and diaphragm strength have used the technique of electrical stimulation of the phrenic nerves. In these studies, the phenomenon of twitch potentiation has not been taken into account. It has previously been shown that prior contraction of the diaphragm can greatly enhance the twitch response, thus affecting the measurements. The aim of this study was to investigate the relationship between unpotentiated twitch Pdi and lung volume for volumes ranging from residual volume (RV) to total lung capacity (TLC) in normal subjects. Great care was taken to avoid muscle potentiation. For this purpose, we stimulated the phrenic nerves with a magnetic stimulator. In addition, we used positive pressure to inflate the lungs to high lung volumes. The impact of twitch potentiation on the length-tension relationship was investigated by subjects making maximum inspiratory efforts prior to phrenic nerve stimulation. The unpotentiated twitch Pdi decreased in a linear fashion with increasing lung volume over the full range of vital capacity by 0.54 kPa.L-1. Potentiation increased twitch Pdi by 40% at FRC and the effect was similar, in absolute terms, at all lung volumes. In relative terms, the effect of potentiation became greater as lung volume increased, and more than doubled twitch Pdi at TLC. With increasing lung volume, there is a linear fall in unpotentiated twitch Pdi with a slope that is less steep, over the same range of absolute lung volume, than previously reported. When assessing diaphragm strength by the twitch technique, it is essential to control for lung volume and equally important to control for twitch potentiation.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
0903-1936
pubmed:author
pubmed:issnType
Print
pubmed:volume
8
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1532-6
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
The effect of lung volume on transdiaphragmatic pressure.
pubmed:affiliation
Respiratory Muscle Laboratory, National Heart and Lung Institute, Brompton Hospital, London, UK.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't