Correction of compliance and resistance altered by endotracheal tube leaks and non-linear pressure/volume-relationships.
Measurements of lung compliance (C) and resistance (R) are influenced by endotracheal tube leaks (ETTL) as well as non-linear pressure/volume relationships (P/V relationship). To keep C and R reliable, we developed an algorithm to mathematically correct inspiratory and expiratory volume (V) and flow. In this study, a ventilated lung model for non-linear P/V relationship with adjustment of an increasing ETTL was studied. In addition, the recordings (airway pressure, flow, and volume) of 21 infants (median weight: 1,220 g, range: 640-2,160 g, with a median leak size of 32%, range: 24-56%) were investigated. C and R were calculated continuously from the recordings of flow, volume, and airway pressure over time according to the changing volume. A method especially developed for the analysis of non-linear pressure-volume-relationship (APVNL) was employed. C and R affected by leaks were corrected applying the newly developed mathematical algorithm and compared with measurements without leakage. C could be corrected up to a leak of 80% and R up to 55% leak at half tidal V for the model with non-linear P/V-R. C and R without leak and after leak correction did not differ significantly in all infants where the APVNL method was applied (P > 0.05).
Nikischin
Werner
W
Department of Pediatrics, University of Kiel, Kiel, Germany. nikischin@pediatrics.uni-kiel.de
Lange
Malte
M
D000403:Airway Resistance; D000465:Algorithms; D004868:Equipment Failure; D045853:Exhalation; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000503:physiopathology* / Q000628:therapy; D001239:Inhalation; D007442:Intubation, Intratracheal / Q000295:instrumentation; D008168:Lung / Q000503:physiopathology*; D008170:Lung Compliance; D008171:Lung Diseases / Q000503:physiopathology* / Q000628:therapy; D008176:Lung Volume Measurements; D008953:Models, Anatomic; D008954:Models, Biological; D017711:Nonlinear Dynamics; D011312:Pressure; D015203:Reproducibility of Results; D015656:Respiratory Mechanics