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Effect of leak around the endotracheal tube on measurements of pulmonary compliance and resistance during mechanical ventilation: A lung model study
Author(s) -
Kuo ChiiYuh,
Gerhardt Tilo,
Bolivar Juan,
Claure Nelson,
Bancalari Eduardo
Publication year - 1996
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/(sici)1099-0496(199607)22:1<35::aid-ppul6>3.0.co;2-j
Subject(s) - medicine , endotracheal tube , pulmonary compliance , leak , compliance (psychology) , lung , mechanical ventilation , ventilation (architecture) , anesthesia , intensive care medicine , airway resistance , intubation , mechanical engineering , psychology , social psychology , environmental engineering , engineering
We studied the effect of leaks around the endotracheal tube (ETT) on the measurement of pulmonary mechanics during mechanical ventilation. We also evaluated the influence of different ventilator settings on the magnitude of leak. An adjustable leak was created at the end of the ETT in a lung model with constant compliance. Flow, tidal volume, and pressure changes were measured above and below the leak. Compliance ( C i ) and resistance ( R i ) during inspiration were determined by linear regression analysis (LRA) using the equation of motion and the Mead and Wittenberger method (MWM). The ventilatory change that influenced the degree of leak most was prolongation of inspiratory time ( T i ). The presence of a leak around the ETT resulted in an overestimation of the C i and R i values, which was proportional to the size of the leak. This overestimation was also influenced by the method used to determine C i and R i . Because the contribution of the leak to the tidal volume progressively increased as inspiration continued, methods of analysis that depended mainly on measurement points at the end of inspiration showed a larger deviation from the true C i and R i values than methods mainly influenced by measurement points at the beginning of inspiration. Because of this, shortening of inspiration, or analysis of points at the beginning of inspiration reduces the error in the measurements of C i and R i when a leak is present. Breaths with a large leak should be excluded from any analysis of pulmonary mechanics. Pediatr Pulmonol. 1996; 22:35–43. © 1996 Wiley‐Liss, Inc.