Effects of inertance on respiratory mechanics measurements in mechanically ventilated children.
OBJECTIVE
The use of the first-order linear single compartment model when studying respiratory mechanics classically neglects inertance (Irs). We hypothesized that Irs would affect compliance (Crs) and resistance (Rrs) estimates in mechanically ventilated young children.


METHODS
Prospective study; single-center evaluation.


METHODS
University-affiliated tertiary pediatric intensive care unit.


METHODS
Forty-four patients with and without respiratory disease.


METHODS
Patients were studied during volume-controlled constant inspiratory flow ventilation.


RESULTS
Pressure (PaO) and flow (V') were analyzed according to two different models: a one-compartment first-order linear model according to PaO = (1/Crs) x V + Rrs x V' and a one-compartment second-order linear model according to PaO = (1/Crs) x V + Rrs x V' + Irs x V''. Irs was higher in children with vs. those without respiratory disease (median 0.00224 cm H2O/L/sec2, Q1-Q3 0.00180-0.00321 vs. median 0.00133 cm H2O/L/sec2, Q1-Q3 0.00072-0.00210; p < .001)). A positive correlation between Irs and the difference of Crs estimates between the first- and the second-order model was found in both groups (r = .84, p < .05 and r = .67, p < .05). Rrs estimates were similar in both groups.


CONCLUSIONS
This study showed that the linear single-compartment model may not adequately estimate the respiratory mechanical properties in mechanically ventilated children, particularly in the presence of respiratory disease. Including an Irs term significantly diminished Crs estimates. A one-compartment second-order linear model might be a useful clinical tool in more adequately measuring respiratory mechanics and optimizing ventilatory settings in children with respiratory disease.
Riou
Yvon
Y
Department of Respiratory Physiology, University Hospital of Lille, France.
Leclerc
Francis
F
Neve
Véronique
V
Sadik
Ahmed
A
Cremer
Robin
R
Leteurtre
Stéphane
S
D000465:Algorithms; D006801:Humans; D007223:Infant; D015278:Intensive Care Units, Pediatric; D008170:Lung Compliance; D015233:Models, Statistical; D011175:Positive-Pressure Respiration / Q000706:statistics & numerical data; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000706:statistics & numerical data*; D012131:Respiratory Insufficiency / Q000628:therapy; D015656:Respiratory Mechanics / Q000502:physiology*