Session Webcast
WEANING: ART OR SCIENCE?
Video on Demand
ENERGY LOAD IN MECHANICALLY VENTILATED PAEDIATRIC LUNGS: A BENCH STUDY
Abstract
Background
Mechanical ventilator energy is transferred to the respiratory system and mainly spent to expand the lung parenchyma and overcome resistance of the airways. This has never been measured in mechanically ventilated children.
Objectives
To determine the tidal mechanical energy imparted to the lungs under different conditions in terms of lung size, respiratory mechanics and ventilator settings.
Methods
A bench study was designed to simulate age groups from newborn (endotracheal tube (ETT) 3.0mm) to adolescent (ETT 8.0mm). Pressure (PC) and volume (VC) controlled modes were tested. All possible combinations of respiratory mechanics were simulated. PEEP was set at 5cmH20. Airway and intrapulmonary pressure, including plateau pressure (Pplat) measured at zero-flow state, tidal volume (VT) and flow were recorded. Elastic energy applied to the lung (ELUNG) per breath normalised to body weight was measured from the dynamic pressure –volume curve.
Results
2,652 measurements were performed. ELUNG was higher in VC (p<0.001) and in small ETT sizes (p<0.001). ELUNG was positively correlated with driving pressure (DP) and inflated volume (VT/kg) (r2=0.87 and r2=0.65, respectively, all p<0.001). Best fitting model for predicting ELUNG was a linear combination of DP and VT/kg (R2 = 0.934, p<0.001). ELUNG differed between ventilation modes after stepwise change of compliance (p<0.001). ELUNG was negatively associated with stepwise increase of resistance only in PC ventilation (p<0.001).
Conclusion
DP and inflated volume were the leading mechanical lung energy coefficients. Further studies are needed to delineate the clinical significance of energy load in children and define the “bearable” range as to cause the least lung damage.
Video on Demand
THE IMPACT OF FLUIDS ON THE DIAPHRAGM FUNCTION IN MECHANICALLY VENTILATED LAMBS WITH ARDS
Abstract
Background
Mechanical ventilation in critically ill children may induce diaphragm atrophy and injury. Besides mechanical ventilation other factors may play a role in critical illness associated diaphragm weakness, including fluid overload and PEEP.
Objectives
To assess the effect of a restrictive versus liberal fluid strategy on diaphragm strength, and microcirculation in lambs. In addition, we studied the effects of acute change in PEEP on diaphragm contractility.
Methods
Sixteen healthy mechanically ventilated lambs were treated with oleic acid intravenous infusion to induce an indirect ARDS-model and were randomized to a strict restrictive or liberal fluid strategy. During transvenous phrenic nerve pacing, transdiaphragmatic pressure (Pdi) were recorded using oesophageal and abdominal balloons. A Cytocam-IDF video microscope was used to assess the microcirculation in the diaphragm.
Results
Fluid intake was higher in the liberal versus restrictive group, (39.2±15.4 ml/kg vs 100.1±17.8ml/kg, p<0.0001). Pdi was significant lower in the restrictive group after 6 hours of mechanical ventilation compared to baseline (8.3 cmH2O [IQR;2.1-20.3] vs 17.9 cmH2O [IQR;14.1-27.2], p=0.036). Microcirculatory flow index and number of vessel crossing was not significantly different (p=0.102 and p=0.344) between the groups after 6 hours of mechanical ventilation. Acute increase in PEEP from 5 cmH2O to 15 cmH2O decreased Pdi upon electrical stimulation with 40% (p = 0.043) in the restrictive group and 22% (p=0.028) in the liberal group.
Conclusion
Compared to liberal fluid intake a restrictive fluid regime is associated with impaired in vivo diaphragm function in lambs with ARDS. High levels of PEEP decrease diaphragm function.
Video on Demand
FLUID OVERLOAD IS ASSOCIATED WITH IMPAIRED OXYGENATION AND MORTALITY IN MECHANICALLY VENTILATED CHILDREN
Abstract
Background
Fluid overload (FO) is common in general pediatric intensive care unit (PICU). Information on impact of FO on oxygenation and mortality in ventilated pediatric patients is limited
Objectives
To prospectively evaluate the association between FO and oxygenation, mortality, mechanical ventilation (MV) duration, and length of stay in a PICU.
Methods
From January to August 2018, 245 children aged ≤ 36 months, who were on invasive MV for > 24 h at the PICU of Vietnam National Children's Hospital were included. Demographic and clinical data were recorded. Daily FO was calculated as [(fluid in-fluid out)/admission weight] × 100% in the first 7 days following admission. Univariate and multivariate analysis were used to assess the independent association between FO percent and oxygenation and clinical outcomes.
Results
Median age was 5.5 (IQR 3, 11) months. Peak FO ≥ 10% was present in 20.0%, and FO>15% was present in 9.0% of patients. Peak FO% during the study period correlated significantly with oxygenation index (OI) (r = 0.23, p =.03). Mortality was 29.0%. Fluid overload ≥ 10% was associated with an increased risk of mortality (OR = 3.1, 95% CI 1.5- 6.5, p=.002) after adjusting for age, PELOD score, and disease severity. We observed a dose-response relationship between FO and mortality, as the FO % cutoff percentage increased, odd ratio for mortality significantly increased. FO was associated with MV duration but not with PICU length of stay.
Conclusion
FO was associated with impaired oxygenation, increased risk of mortality, and prolonged duration of MV among survivors in mechanically ventilated children.