| Abstract |
INTRODUCTION: Functional residual capacity (FRC) determines both oxygenation and respiratory system compliance (CRS). In ARDS, in which FRC is decreased, an optimal PEEP is anticipated to restore FRC; accordingly, application of different levels of PEEP might improve FRC and CRS and ameliorate possible ventilator-induced lung injury. In adult ARDS, it has been argued that PEEP should be titrated primarily by its impact on CRS.
OBJECTIVES: In this longitudinal study, we sought to detect the changes of FRC, Crs, driving pressure (APrs), elastance, and lung stress and strain when applying incremental PEEP levels (PEEP INview) in mechanically ventilated (MV) children with or without ARDS; between groups and longitudinal changes will also be recorded and stress, strain and elastance will be correlated to various lung mechanics, age, hemodynamics, and length of stay (LOS) or MV-
days (MVD).
METHODS: Twenty-three mechanically ventilated children were deeply sedated, paralyzed and ventilated in volume-control mode or PRVC with a tidal volume of 6 mL/kg BW throughout the study protocol. Based on their PaO2/FIO2 ratios, patients with ARDS (<300) or non-ARDS (>300) were subjected to PEEP trials of 4-6-8-10 cmH2 Ο by u s i η g s ρ i ro m et ry of
and the PEEP INview tool. At each PEEP level, FRC and Crs measurements were recorded using the nitrogen washout process; Vt was measured at mouth level. Airway driving pressure was calculated as the airway pressure changes from total PEEP to end-inspiratory plateau pressure. Elastance of the respiratory system, chest-wall, and lung and stress, and strain were calculated longitudinally (0-72 hours).
RESULTS: Twenty-three critically ill mechanically ventilated children (9 girls) were included in the study. Escalated increases of PEEP from 4 to 10 cmH2O decreased stress and strain (p<0.03) and lung elastance (p<0.01) in children with mild or moderate ARDS by 24 hours. FRC showed a trend to increase at all time points, whereas an initial increase in Crs, achieved with PEEP 8, could be sustained from 6 to 72 hours. In both, ARDS and non-ARDS patients, total elastance was higher in the younger age (<5 years old) compared to the middle and older age group (p<0.001) and correlated inversely with age, FRC, and body weight at all PEEP levels, time series and disease groups (p<0.01). Elung/Ers ratios were inversely and Ecw/Ers positively related with FRC changes not differing between groups. Stress and strain were inversely related with FRC and Crs and positively with driving pressure and lung elastance (p<0.01). At all studied PEEP levels, lung mechanics did not interfere with hemodynamics. In a linear regression model (stepwise method), weighted by severity of illness (PRISM), only stress (p<0.001) and total elastance (p<0.02) were independently associated with MVD.
CONCLUSIONS: PEEP INview might represent a promising tool for optimizing PEEP in mechanically ventilated children. Total elastance is inversely related with age and FRC, and along with stress, is independently associated with MVD. Further studies are needed to ascertain if this PEEP strategy could help guide optimizing various aspects of lung mechanics in individual patients.
|
Search
