Feasibility of an alternative, physiologic, individualized open-lung approach to high-frequency oscillatory ventilation in children

Abstract

Background: High-frequency oscillatory ventilation (HFOV) is a common but unproven management strategy in paediatric critical care. Oscillator settings have been traditionally guided by patient age and/or weight rather than by lung mechanics, thereby potentially negating any beneficial effects. We have adopted an open-lung HFOV strategy based on a corner frequency approach using an initial incremental-decremental mean airway pressure titration manoeuvre, a high frequency (8-15 Hz), and high power to initially target a proximal pressure amplitude (∆P_proximal) of 70-90 cm H₂O, irrespective of age or weight.

Methods: We reviewed prospectively collected data on patients < 18 years of age who were managed with HFOV for acute respiratory failure. We measured metrics for oxygenation, ventilation, and haemodynamics as well as the use of sedative-analgesic medications and neuromuscular blocking agents.

Results: Data from 115 non-cardiac patients were analysed, of whom 53 had moderate-to-severe paediatric acute respiratory distress syndrome (PARDS). Sixteen patients (13.9%) died. Frequencies≥ 8 Hz and high ∆P_proximal were achieved in all patients irrespective of age or PARDS severity. Patients with severe PARDS showed the greatest improvement in oxygenation. pH and PaCO₂ normalized in all patients. Haemodynamic parameters, cumulative amount of fluid challenges, and daily fluid balance did not deteriorate after transitioning to HFOV in any age or PARDS severity group. We observed a transient increase neuromuscular blocking agent use after switching to HFOV, but there was no increase in the daily cumulative amount of continuous midazolam or morphine in any age or PARDS severity group. No patients experienced clinically apparent barotrauma.

Conclusions: This is the first study reporting the feasibility of an alternative, individualized, physiology-based open-lung HFOV strategy targeting high F and high ∆P_proximal. No adverse effects were observed with this strategy. Our findings warrant further systematic evaluation.

Keywords: Acute respiratory failure; Child; High-frequency oscillatory ventilation; Mechanical ventilation; Oxygenation; Paediatric acute respiratory distress syndrome; Paediatrics.

Fig. 1

Graphical simplification of the stepwise incremental–decremental mPaw titration when switching to HFOV. The red line represents the inspiratory limb of the pressure volume loop, whereas the green line represents de deflation limb. The mPaw is increased by 2 cmH₂O every 3–5 min until no further improvement in SpO₂ and/or decrease in mean ABP occurs during two consecutive increments (identifying mPaw_recruitment and mPaw_{hyperinflation}). Then, the mPaw is decreased by cmH₂O every 3–5 min until SpO₂ decreased (mPaw_{derecruitment}) during two consecutive decrements. The RM was repeated to mPaw_{hyperinflation} with setting the “optimal” mPaw + 2 cm H₂O above mPaw_{derecruitment}. mPaw mean airway pressure; SpO₂ transcutaneously measured oxygen saturation; mABP mean arterial blood pressure

Fig. 2

HFOV stepwise incremental–decremental mPaw titration

Fig. 3

Level and time course of achieved, frequency (F) (upper panel), proximal pressure amplitude ∆P_proximal (middle panel) and mean airway pressure (mPaw) (lower panel)during the first 72 h of high-frequency oscillatory ventilation (HFOV), stratified by paediatric acute respiratory distress syndrome (PARDS) severity (N = 62 children no/mild PARDS, N = 29 children moderate PARDS, N = 24 children severe PARDS). “Start” is the first measurement immediately after the recruitment manoeuvre. Data are depicted as median (25–75 interquartile range). *p < 0.05

Fig. 4

Level and time course of the oxygenation index (OI) (upper left panel), PaO₂/FiO₂ ratio (upper right panel), PaCO₂ (lower right panel) and pH (upper left panel) during the last 6 h of conventional mechanical ventilation (CMV) and the first 72 h of high-frequency oscillatory ventilation (HFOV), stratified by paediatric acute respiratory distress syndrome (PARDS) severity (N = 62 children no/mild PARDS, N = 29 children moderate PARDS, N = 24 children severe PARDS). “Start” is the first measurement immediately after the recruitment manoeuvre. Data are depicted as median (25–75 interquartile range). *p < 0.05

Fig. 5

Level and time course of hemodynamic parameters including heart rate (upper left panel), mean arteria blood pressure (upper right panel), central venous pressure (lower left panel) and blood lactate (lower right panel) during the last 6 h of conventional mechanical ventilation and the subsequent first 72 h of high-frequency oscillatory ventilation, stratified by age group (N = 83 children ≤ 12 months, N = 20 children 13–60 months and N = 12 children ≥ 61 months). “Start” is the first measurement immediately after the recruitment manoeuvre. Data are depicted as median (25-75 interquartile range). *p < 0.05

Fig. 6

Level and time course of the cumulative amount of fluid boluses in mL/kg (upper left panel), vasoactive score (middle left panel) and the cumulative fluid balance in mL/kg (lower left panel), and the percentage of patients who received fluid boluses per day (upper right panel) and patients on vasoactive support per day (lower right panel), stratified by age group (N = 83 children ≤ 12 months, N = 20 children 13–60 months and N = 12 children ≥ 61 months). Continuous data are depicted as median (25-75 interquartile range) and categorical data as  % of total. CMV conventional mechanical ventilation. *p < 0.05

Fig. 7

Percentage of patients who were on neuromuscular blocking agents (NMBA) (upper panel), mean midazolam dose (mg/kg/hour) (middle panel) and mean morphine dose (mcg/kg/hour) (lower panel) stratified by age group (N = 83 children ≤ 12 months, N = 20 children 13–60 months and N = 12 children ≥ 61 months). Continuous data are depicted as median (25–75 interquartile range) and categorical data as  % of total. CMV conventional mechanical ventilation. *p < 0.05