Additional work of breathing from trigger errors in mechanically ventilated children
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RESEARCH
Additional work of breathing from trigger errors in mechanically ventilated children Robert G. T. Blokpoel1* , Alette A. Koopman1, Jefta van Dijk1 and Martin C. J. Kneyber1,2
Abstract Background: Patient–ventilator asynchrony is associated with increased morbidity and mortality. A direct causative relationship between Patient–ventilator asynchrony and adverse clinical outcome have yet to be demonstrated. It is hypothesized that during trigger errors excessive pleural pressure swings are generated, contributing to increased work-of-breathing and self-inflicted lung injury. The objective of this study was to determine the additional work-ofbreathing and pleural pressure swings caused by trigger errors in mechanically ventilated children. Methods: Prospective observational study in a tertiary paediatric intensive care unit in an university hospital. Patients ventilated > 24 h and 24 h and 75th percentile as proposed by others (i.e. TE-index > 22.5%) [14, 29]. PTP was calculated by integrating the area under the oesophageal pressure versus time scalar from the beginning until the end of inspiration [23, 30]. For each patient median PTP for effective and ineffective breaths were calculated. We determined for the entire 5-min recording of all effective (PTPCUMULATIVE_BREATHS) and ineffective breaths (PTPCUMULATIVE_PVA). PTPTOTAL was defined as the sum of P TPCUMULATIVE_BREATH and PTPCUMULATIVE_PVA. The oesophageal peak-to-trough (ΔPoes) was calculated by subtracting the end-inspiratory Poes from the Poes at the onset of inspiration. We expected that patients with a lower number of ineffective triggering events would have lower PTP and ΔPoes. To compare the PTP between ineffective and effective breaths in each individual patient, the ratio of PTPPVA over PTPBREATH (PTPPVA/PTPBREATH) and ΔPoes-ineffective over ΔPoes-effective (ΔPoes-ineffective/ΔPoeseffective) was calculated. Statistical analysis
The Shapiro–Wilk test was used to test for normal distribution of the data. Normally distributed continuous data are presented as mean and standard deviation (SD). When the assumption of normality was not met, data are presented as median and 25–75 interquartile range (IQR). Categorical data are presented as percentage (%) of total. When comparisons between groups were made, continuous data were analysed using the Mann–Whitney U test. Spearman’s rank correlation coefficient was used to measure dependence between two variables. All statistical analyses were performed using SPSS version 24 (IBM, Armonk, USA). P values below 0.05 were considered statistically significant.
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Results In total 6194 breaths from 31 randomly selected patients (17 boys, 14 girls) were analysed. Median breaths during the 5-min recording was 180 [147; 249]. The median age was 3.0 [1.9; 18.5] months and median weight 5.6 [4.4; 9.8] kg. Median time patients were ventilated before data acquisition was 2.9 [1.9; 5.2] days. Median duration of MV was 5.9 [4.4; 9.5] days. NMB was used in 19 (61%) patients for a
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