Document Detail

Reduction of oscillatory pressure along the endotracheal tube is indicative for maximal respiratory compliance during high-frequency oscillatory ventilation: a mathematical model study.
MedLine Citation:
PMID:  11389579     Owner:  NLM     Status:  MEDLINE    
We hypothesized that during high-frequency oscillatory ventilation (HFOV), a reduction of peak-to-peak oscillatory pressure along the endotracheal tube is maximal when respiratory system compliance is maximal. We made a mathematical model of the endotracheal tube and the respiratory system of a neonate suffering from idiopathic respiratory distress syndrome (IRDS). The model consisted of linear viscous and inertive elements, a non-linear endotracheal tube resistance, and a non-linear compliance allowing for alveolar recruitment and overdistention. Respiratory compliance was maximal at the transition between maximal recruitment and minimal overdistention. A new variable, the oscillatory pressure ratio (OPR), was defined as the ratio between peak-to-peak oscillatory pressures at the distal end and the proximal opening of the endotracheal tube, respectively. The respiratory variables of four patients were fed into the model, and the relationship between respiratory system compliance and OPR was determined. OPR decreased as compliance increased, except for very low compliances below where 0.08 mL. cm H2O(-1), and OPR increased with increasing compliance. The relationship between mean airway pressure P(aw) and OPR revealed that the minimal OPR (range, 0.37-0.78) and maximal respiratory compliance coincided at the same P(aw). However, the relationship did depend on oscillation frequency, applied oscillatory pressure, and endotracheal tube resistance, parameters that may change during clinical application of HFOV. When 81 permutations of nominal and extreme respiratory variables were used in the model, the minimum OPR (0.60 +/- 0.23) and maximum compliance coincided in all cases. These model experiments support our hypothesis. The results indicate that the OPR may be a useful index to optimize lung expansion, where lung recruitment is maximal and overdistention minimal. In vivo tests will be needed to reveal the feasibility and reliability of such an index for biomedical and clinical application.
H R van Genderingen; A Versprille; T Leenhoven; D G Markhorst; A J van Vught; R M Heethaar
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Pediatric pulmonology     Volume:  31     ISSN:  8755-6863     ISO Abbreviation:  Pediatr. Pulmonol.     Publication Date:  2001 Jun 
Date Detail:
Created Date:  2001-06-04     Completed Date:  2001-07-12     Revised Date:  2006-03-28    
Medline Journal Info:
Nlm Unique ID:  8510590     Medline TA:  Pediatr Pulmonol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  458-63     Citation Subset:  IM    
Department of Clinical Physics and Informatics, University Hospital Vrije Universiteit, Amsterdam, Netherlands.
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MeSH Terms
Airway Resistance
High-Frequency Ventilation*
Infant, Newborn
Intubation, Intratracheal
Lung Compliance
Models, Theoretical*
Predictive Value of Tests
Reference Values
Respiratory Distress Syndrome, Newborn / physiopathology*,  therapy
Trachea / physiology*

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