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A computer‐model analysis of the influence of the upper airway on passive flow‐volume loops in infants
Author(s) -
Sly Peter D.
Publication year - 1989
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.1950060206
Subject(s) - medicine , airway resistance , flow resistance , volume (thermodynamics) , flow (mathematics) , airway , elastance , respiratory system , mechanics , cardiology , anesthesia , physics , thermodynamics
Abstract The present study was undertaken to determine the effects of upper airway resistance (R ua ) and elastance (E ua ) on the mechanical parameters calculated from the expiratory limb of the passive flow‐volume curve in normal infants, using a computer model. The model included separate compartments for the respiratory system, upper airway, and measurement equipment. Inclusion of R ua in the model decreased the slope of the expiratory limb of the flow‐volume loop, and the resistance calculated from the flow‐volume loop accurately reflected the total resistance of the model. Inclusion of E ua in the model caused a decrease in the end‐inspiratory (driving) pressure and a corresponding decrease in the peak expiratory flow but did not alter the slope of the linear portion of the expiratory limb of the flow‐volume loop. Resistance calculated from the loop underestimated true model resistance by 14.5%. However, further small fluctuations in E ua did not cause significant variability in the value of resistance calculated. Total elastance was accurately calculated whether or not R ua and E ua were included in the model. The results of this analysis demonstrate that, while E ua causes the true resistance to be underestimated, fluctuations in E ua are not likely to be an important source of variability in the mechanical parameters calculated from the passive flow‐volume loop; however, any changes in R ua will be reflected in the value of resistance calculated and therefore are likely to cause substantial variability in the calculated resistance.