The present study is aimed to establish the epidemiological characteristics and clinical outcomes of mechanically ventilated children with acute hypoxemic respiratory failure (AHRF), defined as PaO2/FiO2 ≤300 mmHg on PEEP≥5 cmH2O and FiO2≥0.3, admitted in a network of pediatric hospitals in Spain.

Prospective, multicenter, observational study focused on the prevalence and outcomes of Acute Hypoxemic Respiratory Failure in children. From a total of 40 pediatric ICUs in Spain, 22 PICUs agreed to participate.

All consecutive patients from 7 days to 16 years old admitted in the PICU will have been enrolled if they fulfilled the following criteria: 1) acute episode (within 7 days of a clinical insult), 2) on invasive mechanical ventilatory support, 3) PaO2/FiO2 ≤ 300 mmHg (or SpO2/FiO2 ≤ 264), 4) Positive end-expiratory pressure (PEEP) ≥ 5 cmH2O and FiO2 ≥ 0.3.

This study is considered an audit, and informed consent is waived.

Period of study: 2 years (October 2019 to September 2021). Recruitment period: two consecutive months (i.e October-November followed by a period of no recruitment) until complete 12 months of recruitment (September 2021).

All investigators have received guidelines outlining the study design and the methods for data collection. All PICU admissions are screened daily for AHRF. Onset of AHRF was defined as the day on which the patient first met all inclusion criteria. All data are collected on standardized forms. Demographics, comorbidities, reason for initiation of IMV, arterial blood gases, laboratory, radiographic, hemodynamic and ventilator data were collected at study entry and during the first three days of AHRF diagnosis (T0 or time of inclusion in the study, 24 hours, days 2 and 3). Chest imaging (chest radiographs, lung ultrasound or computed tomography) were evaluated daily for the presence or absence of infiltrates, atelectasis, acute pulmonary edema, pleural effusion or pneumothorax. Tidal volume (VT) was calculated on the basis of the predicted body weight (PBW). Plateau pressure (Pplat) was determined after the application of a 0.5- to 1.0-sec end-inspiratory hold. Driving pressure was calculated as the difference between Pplat and PEEP. Patients meeting pediatric ARDS criteria were stratified into a mild, moderate, and severe according to PALICC definition and/or berlin definition. All patients are followed until PICU and hospital discharge.

Data are initially collected and stored at each center and then sent to study coordinators at the time of patient's hospital discharge.

Although patient care is not strictly protocolized, physicians are asked to follow the current standards of pediatric critical care management. For ventilatory management, it was recommended that all patients be ventilated with a VT of 6-8 mL/kg PBW, at a ventilatory rate to maintain PaCO2 at 35-50 mm Hg, a Pplat <30 cm H2O, and PEEP and FiO2 combinations to maintain PaO2 >60 mm Hg or SpO2 >90%.

Statistical Analysis: for the main objective of the study, a descriptive analysis including clinical variables, mechanical ventilation data, respiratory settings and ancillary measures will be performed.

Inclusion Criteria:

• Patients from 7 days to 16 years old admitted in the PICU.
• Acute episode (within 7 days of a clinical insult)
• On invasive mechanical ventilatory support
• PaO2/FiO2 ≤ 300 mmHg (or SpO2/FiO2 ≤ 264)
• Positive end-expiratory pressure (PEEP) ≥ 5 cmH2O and FiO2 ≥ 0.3.

Exclusion Criteria:

• Non-invasive respiratory support *Aged >16 years or < 7 days.

All consecutive patients from 7 days to 16 years old admitted in the PICU with an acute episode (within 7 days of a clinical insult) of hipoxemia defined as PaO2/FiO2 ≤ 300 mmHg (or SpO2/FiO2 ≤ 264), and on invasive mechaniccal ventilatio with a PEEP ≥ 5 cmH2O and FiO2 ≥ 0.3.