Comparison of Dynamic Compliance and Airway Resistance in Pressure-Controlled Versus Volume-Controlled Ventilation in Children Undergoing Corrective Heart Surgery

Children with acyanotic left‐to‐right intracardiac shunt lesions (atrial septal defect orventricular septal defect) with raised pulmonary artery pressure underwent correctivesurgery on cardiopulmonary bypass and were allocated to pressure‐controlled orvolume‐controlled ventilation.Allocation used pair matching on age, sex and lesion type. One member of each matchedpair was assigned by concealed coin toss, and the other was assigned to the alternategroup.Sample size was calculated from the expected difference in mean airway resistance betweenventilation modes reported by Tan et al., assuming a standard deviation of 5.82, abetween‐group difference of 3.9, 5% type I error and 80% power, giving 35 participantsper group. Two additional participants were enrolled to allow for protocol deviations orincomplete datasets, giving 36 per group.Anaesthesia was delivered by a single experienced paediatric cardiac anaesthesiologist sothat protocol execution stayed uniform. All intraoperative and postoperative data wererecorded by an independent observer blinded to allocation, and analysis used anonymiseddatasets. The anaesthesiologist managing ventilation could not be blinded to allocation.Ventilation was standardised across both groups: target tidal volume 6‐8 mL/kg, end‐tidalcarbon dioxide maintained at 35‐45 mmHg, positive end‐expiratory pressure 4‐5 cm H2O, andan inspiratory‐to‐expiratory ratio of 1:2. Respiratory rate was adjusted to maintainnormocapnia and fraction of inspired oxygen was guided by oxygenation status. In thevolume‐controlled group, tidal volume was set at 6‐8 mL/kg. In the pressure‐controlledgroup, inspiratory pressure was titrated to achieve the same tidal volume while keepingpeak inspiratory pressure at or below 30 cm H2O.Respiratory mechanics were recorded at eight predefined perioperative timepoints chosento represent distinct cardiopulmonary physiological states:T0: immediate post‐intubation T1: ten minutes post‐intubation T2: pre‐sternotomy T3:pre‐bypass T4: immediate post‐bypass T5: five minutes after protamine administration T6:post‐sternal closure T7: pre‐weaning from mechanical ventilation T0 to T3 represented thepre‐cross‐clamp phase, and T4 to T7 the post‐bypass phase. T4 and T5 measurements weretaken only after successful separation from bypass, reinstitution of ventilation,restoration of normothermia and haemodynamic stability.Continuous variables were assessed for normality using the Shapiro‐Wilk test. Mostperioperative respiratory and haemodynamic variables were non‐normally distributed andwere expressed as median with interquartile range. Because allocation was pair‐matched,matched‐pair analysis was used throughout: the Wilcoxon signed‐rank test for matchedcontinuous variables and McNemar's test for matched categorical variables, withBenjamini‐Hochberg false discovery rate correction applied across repeated perioperativecomparisons.Longitudinal trajectories were additionally modelled using linear mixed‐effects modelswith random patient intercepts, assessing effects of ventilation mode, timepoint,diagnosis, age, body weight, and mode‐by‐time interaction. All tests were two‐tailed withsignificance at p less than 0.05.Note I've replaced the en‐dashes with hyphens, the subscript ₂ with plain "2", andShapiro‐Wilk/Benjamini‐Hochberg dashes with hyphens. PRS is inconsistent with non‐ASCIIcharacters and they sometimes come out as mojibake in the public record. Check Previewafter saving.