Prone Position in infantS/Children With Acute Respiratory Distress Syndrome

Study Overview
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Brief Summary
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In adult patients with acute respiratory distress syndrome (ARDS), the beneficial effects of prone position (PP) have been well investigated and explored; it reduces intrapulmonary shunt (Qs/Qt) and enhances lung recruitment, modifying both lung ventilation (VA) and lung perfusion (Q) distribution, finally generating an improvement in VA/Q matching and reversing oxygenation impairment;it reduces right ventricular afterload, increase cardiac index in subjects with preload reserve and reverse acute cor pulmonale in severe ARDS patients, but in infants and children there is still a lack of clear evidence. Taken together, these effects explain why PP improves oxygenation, limits the occurrence of ventilator-induced lung injury and improves survival. Prone position is simple to perform in infants and in some neonatal and pediatric intensive care units is already commonly accomplished. However, a detailed analysis of the respective effects of high PEEP and prone position is lacking in infants/children with ARDS, while these two tools may interfere and/or act coherently. A recent multicenter, retrospective analysis of patients with pediatric acute respiratory distress syndrome (PARDS) describes how patients managed with lower PEEP relative to FIO2 than recommended by the ARDSNet model had higher mortality, suggesting that future clinical trials targeting PEEP management in PARDS are needed. We designed a physiological study to investigate the physiological effects of prone positioning on lung recruitability in infants/children with acute respiratory distress syndrome.

Detailed Description
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Each patient meeting inclusion criteria will be evaluated for the presence of the oxygenation criterion. After neuromuscular paralysis (or apnoeic ventilation as per PICU protocol), and endotracheal suctioning, eligible patients will be ventilated for 30 min with PEEP = 5 cmH2O in the semi-recumbent position, with a tidal volume limited to 6 mL/kg and a Plateau Pressure less than 30 cmH2O. FiO2 will be titrated to obtain and SpO2 >92 % and <98 %. Afterward, arterial blood gas analysis (ABG) will be performed to compute PaO2/FiO2 ratio to confirm the presence of the inclusion and the absence of exclusion criteria.Patients showing PaO2/FiO2 ≤ 200 mmHg will be enrolled. Eligible patients will undergo the following protocol: Verify the presence of airway closure with airway opening pressure (AOP) > PEEP5cmH2O; PEEP will be initially set at 12 cmH2O (providing that plateau and driving pressures do not exceed 30 cmH2O and 15 cmH2O, respectively) for 40 minutes to stabilize lung volumes; afterwards, respiratory mechanics will be assessed through standard occlusions and arterial blood gases will be analyzed. Subsequently, a 4-steps decremental PEEP trial (PEEP 12 to 10 to 8 to 5 cmH2O) will be conducted. Each PEEP step will last 8 minutes, and all other ventilator settings will remain unchanged throughout the procedure. At the end of each PEEP step respiratory mechanics will be assessed by the ventilator through 1-second end-inspiratory and end-expiratory holds: plateau pressure [Pplat] and total PEEP [PEEPtot] will be measured, and driving pressure [ΔP=Pplat-PEEPtot] and respiratory system compliance [Crs = VT/ΔP] will be assessed; End-expiratory lung impedance (EELI) will be measured by electrical impedance tomography (EIT)

Official Title
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Physiological Effects of Prone vs. sUpine Position on Lung Recruitability in infantS/Children With Acute Respiratory Distress Syndrome

Conditions
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Prone Position, Acute Respiratory Distress Syndrome

Intervention / Treatment
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* Procedure: supine position
* Procedure: prone position


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: PaO2/FiO2 < 200 in the supine position, with a standard PEEP of 5 cmH2O; PaCO2 <45mmHg; Absence of history of chronic respiratory disease or heart failure or congenital heart disease (Modified Ross heart failure classification for children < II); Not underweight infants/children defined as a low body mass index (BMI) for age; Absence of any contraindication to PP (Appendix 1); Written informed consent of both parents and the legal guardian. Exclusion Criteria: Barotrauma; Less than 4 weeks of age (new-born physiology); Exacerbation of asthma; Chest trauma; Pulmonary oedema/haemorrhage; Severe Neutropenia (<500 WBC/mm3); Haemodynamic instability (Systolic blood pressure < 5th percentile or mean arterial pressure < 5th percentile adjusted by age); Lactic acidosis (lactate >5 mmol/L) and/or clinically diagnosed shock; Metabolic Acidosis (pH <7.30 with normal- or hypo-carbia); Chronic kidney failure requiring dialysis before PICU admission; Upper gastrointestinal bleeding. Refusal to sign written informed consent of both parents and the legal guardian.

Ages Eligible for Study
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Maximum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Non-Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: 2x2 cross-over design
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Controls<br>Eligible patients will undergo the experimental protocol. | Procedure: supine position<br>* At the end of the PEEP trial (i.e. at PEEP 5 cmH2O), patients will lay in the supine position for 15 minutes arterial blood gases will be performed and then a one-breath derecruitment maneuver (5-second exhalation, respiratory rate < 8 bpm) from PEEP 5 cmH2O to 0 cmH2O will be conducted to assess baseline functional residual capacity (FRC), defined as the EELI measured at 0 PEEP.<br>Procedure: prone position<br>* After the supine step, each enrolled patient will be placed in the prone position for 1 hour. For safety reasons, enteral feeding will be interrupted 30 minutes before prone positioning and re-established after the study ending. During pronation FiO2 will be increased up to 80% and then gradually decreased to the baseline value within the first 30 minutes of prone positioning. After 30 minutes of PEEP 12 cmH2O (provided that plateau and driving pressures did not exceed 30 cmH2O and 15 cmH2O, respectively) to stabilize lung volumes, the same measurements applied for the supine step will be performed. Any further modifications in the MV settings will be discouraged over the entire course of the study; nonetheless, if needed to achieve the SpO2 target, an increase in FiO2 will be allowed and recorded. In case of sudden worsening of the oxygenation impairment or haemodynamic, 100% FiO2 will be set, and the patient will be promptly positioned in the supine semi-recumbent position.<br>|
| Experimental: Patients<br>Eligible patients will undergo the experimental protocol. | Procedure: supine position<br>* At the end of the PEEP trial (i.e. at PEEP 5 cmH2O), patients will lay in the supine position for 15 minutes arterial blood gases will be performed and then a one-breath derecruitment maneuver (5-second exhalation, respiratory rate < 8 bpm) from PEEP 5 cmH2O to 0 cmH2O will be conducted to assess baseline functional residual capacity (FRC), defined as the EELI measured at 0 PEEP.<br>Procedure: prone position<br>* After the supine step, each enrolled patient will be placed in the prone position for 1 hour. For safety reasons, enteral feeding will be interrupted 30 minutes before prone positioning and re-established after the study ending. During pronation FiO2 will be increased up to 80% and then gradually decreased to the baseline value within the first 30 minutes of prone positioning. After 30 minutes of PEEP 12 cmH2O (provided that plateau and driving pressures did not exceed 30 cmH2O and 15 cmH2O, respectively) to stabilize lung volumes, the same measurements applied for the supine step will be performed. Any further modifications in the MV settings will be discouraged over the entire course of the study; nonetheless, if needed to achieve the SpO2 target, an increase in FiO2 will be allowed and recorded. In case of sudden worsening of the oxygenation impairment or haemodynamic, 100% FiO2 will be set, and the patient will be promptly positioned in the supine semi-recumbent position.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| effect of prone positioning on lung recruitability | PaO2/FiO2 ratio | at the end of the supine and prone position | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| difference in gas exchanges | PaO2/FiO2, PaCO2, PaO2 | at the end of the supine and prone position | 
| ventilatory ratio | minute ventilation (ml/min) × PaCO2 (mmHg)]/(predicted body weight × 100 × 37.5) | at the end of the supine and prone position | 
| global impedance-derived End-expiratory lung volume | effects of prone position on End-expiratory lung volume, measured with electrical impedance tomography | at the end of the supine and prone position | 
| regional impedance-derived End-expiratory lung volume | effects of prone position on End-expiratory lung impedance in the four regions of the lungs (ventral, mid-ventral, mid-dorsal, dorsal), measured with electrical impedance tomography | at the end of the supine and prone position | 
| tidal volume distribution | effect of prone position on % tidal volume distribution in the four regions of the lung (ventral, mid-ventral, mid-dorsal, dorsal), explored with electrical impedance tomography | at the end of the supine and prone position | 
| global impedance-derived lung dynamic strain | change in impedance due to tidal volume / end expiratory lung impedance, both measured with electrical impedance tomography | at the end of the supine and prone position | 
| regional impedance-derived lung dynamic strain | change in impedance due to tidal volume / end expiratory lung impedance in the four regions of the lungs (ventral, mid-ventral, mid-dorsal, dorsal), measured with electrical impedance tomography | at the end of the supine and prone position | 
| number of displacements of the endotracheal tube during prone position | safety endpoint | 2 hours | 
| number of oxygen desaturations during prone position | safety endpoint | 2 hours |