Am. J. Respir. Crit. Care Med., Volume 162, Number 1, July 2000, 139-147

Ventilator-induced Overdistension in Children
Dynamic versus Low-flow Inflation Volume-Pressure Curves

VÉRONIQUE NÈVE, ERIC DUMAS de la ROQUE, FRANCIS LECLERC, STÉPHANE LETEURTRE, AYMÉE DORKENOO, AHMED SADIK, ROBIN CREMER, and RÉGIS LOGIER

Service de Réanimation Pédiatrique, Centre Hospitalier et Universitaire de Lille, Lille, France

We applied to 20 paralyzed ventilated children (0.15 to 14.3 yr, six with acute respiratory distress syndrome [ARDS]) the low-flow inflation (LFI) technique providing quasi-static volume-pressure (V-P) curves and compared the assessment of overdistension (OD) on dynamic and LFI (reference) inspiratory V-P curves. Dynamic curves were obtained at the airway opening during regular constant flow ventilation (Servo 300). Then LFI curves were obtained. Two analyses were performed: First, the nonlinear coefficient c of a second order polynomial equation (SOPE) fitted to dynamic data obtained during constant flow was compared with the c of SOPE fitted to LFI curve (within tidal volume [VT]). Second, the dynamic C20/C (ratio of compliance of the last 20% of the curve (C20) to total compliance [C]) was compared with the determination of the upper inflection point (UIP) on the LFI curve. OD was defined as a negative value of c, a C20/C < 0.80, an UIP included within the VT range for that child during regular ventilation. Using LFI V-P curves as reference, SOPE offered a better detection of OD than dynamic C20/C or the determination of the UIP by graphical means. Indeed the first analysis showed a substantial agreement ( 0.75) between dynamic c and LFI c detection of OD whereas the second analysis showed a poor agreement ( 0.22) between C20/ C and LFI detection of the UIP. In conclusion, quasi-static V-P curves can easily be obtained in children with the LFI technique. SOPE offers a good detection of OD on dynamic and LFI V-P curves but the C20/C index seems to be an inadequate measure of OD.

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