A pilot prospective study on closed loop controlled ventilation and oxygenation in ventilated children during the weaning phase

Abstract

Introduction: The present study is a pilot prospective safety evaluation of a new closed loop computerised protocol on ventilation and oxygenation in stable, spontaneously breathing children weighing more than 7 kg, during the weaning phase of mechanical ventilation.

Methods: Mechanically ventilated children ready to start the weaning process were ventilated for five periods of 60 minutes in the following order: pressure support ventilation, adaptive support ventilation (ASV), ASV plus a ventilation controller (ASV-CO2), ASV-CO2 plus an oxygenation controller (ASV-CO2-O2) and pressure support ventilation again. Based on breath-by-breath analysis, the percentage of time with normal ventilation as defined by a respiratory rate between 10 and 40 breaths/minute, tidal volume > 5 ml/kg predicted body weight and end-tidal CO2 between 25 and 55 mmHg was determined. The number of manipulations and changes on the ventilator were also recorded.

Results: Fifteen children, median aged 45 months, were investigated. No adverse event and no premature protocol termination were reported. ASV-CO2 and ASV-CO2-O2 kept the patients within normal ventilation for, respectively, 94% (91 to 96%) and 94% (87 to 96%) of the time. The tidal volume, respiratory rate, peak inspiratory airway pressure and minute ventilation were equivalent for all modalities, although there were more automatic setting changes in ASV-CO2 and ASV-CO2-O2. Positive end-expiratory pressure modifications by ASV-CO2-O2 require further investigation.

Conclusion: Over the short study period and in this specific population, ASV-CO2 and ASV-CO2-O2 were safe and kept the patient under normal ventilation most of the time. Further research is needed, especially for positive end-expiratory pressure modifications by ASV-CO2-O2.

Trial registration: ClinicalTrials.gov: NCT01095406.

Figures

Figure 1

Study protocol. Included patients were prospectively enrolled in a sequential study during which they received five consecutive 1-hour periods of ventilation. PSV, pressure support mode; ASV, adaptive support ventilation mode; ASV-CO2, ASV and CO2 controller; ASV-CO2-O2, ASV-CO2 and oxygen controller.

Figure 2

Functional algorithm of the ventilation and oxygen controller. (A) Ventilation controller. The partial pressure in end-tidal CO2 (PEtCO2) values are given with the quality index and derived from the mainstream CO2 sensor with proprietary algorithms as a surrogate of arterial partial pressure of CO2. PEtCO2min and PEtCO2max are adjustable by the user and depend on the patient's severity estimated by the level of inspiratory pressure; that is, the higher the inspiratory pressure and the more permissive the PEtCO2 limits. As an example and by default for an inspiratory pressure of 10 cmH2O, PEtCO2min is 35 mmHg and PEtCO2max is 41 mmHg. (B) Oxygen controller. The oxygen saturation from pulse oxymetry (SpO2) limits (SpO2safety and SpO2min) are adjustable by the user and depending on the patient's severity estimated by the positive end-expiratory pressure (PEEP) level; that is, the higher the PEEP level and the more permissive the SpO2 limits. As an example and by default for a PEEP level of 5 cmH2O, SpO2safety is 88%, SpO2min is 93% and SPO2max is 98%. The PEEPopt is defined according to a PEEP-fraction of inspired oxygen (FiO2) table and PEEPmax set by the user. The patient SpO2 is provided with a quality index and is derived from the pulse oxymeter with proprietary algorithms for artefact and motion rejections. MV, minute ventilation; RR, respiratory rate.

Figure 3

Peak airway pressure of children during the 1-hour periods of mechanical ventilation. Peak inspiratory airway pressure (Paw-peak; median and standard deviation (SD)) of the 14 children included during the five 1-hour periods of mechanical ventilation. The median values were not statistically different, but the SDs of individual breath-by-breath values (right panel) were significantly higher, suggesting more variability in adaptive support ventilation (ASV), ASV and CO2 controller (ASV-CO2) and ASV-CO2 and oxygen controller (ASV-CO2-O2) as compared with pressure support ventilation (PSV).