Related Experiment Videos
Ventilator-induced overdistension in children: dynamic versus low-flow inflation volume-pressure curves
V Nève1, E D de la Roque, F Leclerc
1Service de Réanimation Pédiatrique, Centre Hospitalier et Universitaire de Lille, Lille, France.
Insights
The low-flow inflation (LFI) technique effectively assesses overdistension in ventilated children. The second-order polynomial equation (SOPE) method accurately detects overdistension on dynamic and LFI curves, unlike the C20/C index.
Area of Science:
- Pediatric critical care medicine
- Respiratory physiology
- Mechanical ventilation
Background:
- Assessing overdistension (OD) in mechanically ventilated children is crucial for preventing lung injury.
- Dynamic volume-pressure (V-P) curves are commonly used but may not accurately reflect static lung mechanics.
- The low-flow inflation (LFI) technique offers a method to obtain quasi-static V-P curves for improved assessment.
Purpose of the Study:
- To compare the accuracy of overdistension detection using dynamic V-P curves versus LFI-derived quasi-static V-P curves in paralyzed, ventilated children.
- To evaluate two methods for OD assessment: a second-order polynomial equation (SOPE) and the C20/C compliance index.
Main Methods:
- Twenty paralyzed, ventilated children (0.15–14.3 years) underwent dynamic V-P curve acquisition during constant flow ventilation.
- LFI technique was used to obtain quasi-static V-P curves.
- Overdistension was assessed by comparing the nonlinear coefficient 'c' from SOPE and the C20/C index derived from both dynamic and LFI curves.
Main Results:
- The SOPE method showed substantial agreement (kappa=0.75) in detecting OD between dynamic and LFI curves.
- The C20/C index demonstrated poor agreement (kappa=0.22) for OD detection when compared to LFI reference.
- LFI V-P curves were easily obtained and provided a reliable reference for OD assessment.
Conclusions:
- The LFI technique is a feasible method for obtaining quasi-static V-P curves in pediatric patients.
- SOPE is a reliable method for detecting overdistension on both dynamic and LFI V-P curves.
- The C20/C index is an inadequate measure for assessing overdistension in this population.
Abstract:
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 (kappa 0.75) between dynamic c and LFI c detection of OD whereas the second analysis showed a poor agreement (kappa 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.