Materials and Methods

Study Population

This retrospective study enrolled all patients aged between 1 month and 14 years of age who were diagnosed with PARDS in the PICU of Shengjing Hospital between January 2013 and January 2020. Data were collected by searching the Health Information System (HIS) database for the PARDS diagnostic and clinical codes “principal diagnosis” and “all listed diagnoses,” yielding the final list of patients included in the study. In addition, patients’ diagnoses were confirmed from their medical records. Patients meeting the following criteria were included: 1) age between 1 month and 14 years; and 2) ARDS diagnosis and treatment with invasive mechanical ventilation. ARDS was defined in accordance with the Pediatric Acute Lung Injury Consensus Conference (PALICC) criteria [11]. Patients meeting the following criteria were excluded: 1) noninvasive ventilation treatment was received during the first 24 h following ARDS diagnosis; 2) missing data for any included variables; and 3) PICU admission lasting <24 h.

Data Collection

The following demographic and clinical data were retrospectively collected from electronic medical records (HIS records): 1) age and sex; 2) mortality and FSS scores upon admission and at hospital discharge; 3) data pertaining to treatment regimens following ARDS diagnosis, including inhaled nitric oxide, neuromuscular blockers, continuous renal replacement therapy, and extracorporeal membrane oxygenation (ECMO); 4) measurement data for the worst peak inspiratory pressure (PIP), positive end-expiratory pressure (PEEP), and inhaled oxygen concentration within the first 24 h after ARDS diagnosis (collected from blood tests); and 5) mechanical ventilation parameters. FSS scores upon admission and at discharge were determined retrospectively based on data recorded in the medical charts to assess and compare clinical and functional outcomes at those time points. The initial FSS score reflected each child’s functional status upon hospital/PICU admission with critical illness and chronic comorbid conditions, both of which contribute to impaired functional status. The FSS is based on symptomology scores, such as those of the Pediatric Overall Performance Category Scale, Pediatric Cerebral Performance Category Scale, and Glasgow Coma Scale [12]. It comprises six domains (mental, sensory, communication, motor, feeding, and respiratory), with domain scores ranging from 1 (normal) to 5 (very severe dysfunction), and total scores ranging from 6–30, with scores of 6‒7, 8‒9, 10‒15, 16‒21, and >21 indicating good, mildly abnormal, moderately abnormal, severely abnormal, and very severely abnormal functional status, respectively [3].

Definitions

In-hospital mortality was defined as in-hospital death following PICU admission. FSS dysfunction was defined as a change in FSS score ≥3 between baseline and discharge. PARDS severity was determined according to the worst oxygenation index (OI) in the first 24 h following diagnosis, according to the PALICC categories [11]. Patients were stratified into two groups based on severity, with an OI <16 defined as mild/moderate PARDS and an OI ≥16 as severe PARDS. The partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) (P/F) ratio was based on the Berlin definition issued by the European Society of Critical Care Medicine, where severity was graded as follows: mild/moderate, P/F >100, and severe, P/F ≤100 [13]. The Pediatric Logistic Organ Dysfunction-2 (PELOD-2) score was used to assess disease criticality in all patients upon admission [14]. The neuromuscular blocking agents used included rocuronium and vecuronium. Hemopurification refers to continuous renal replacement therapy. Direct and indirect PARDS were defined as ARDS caused by pneumonia, aspiration, or lung contusion and ARDS caused by non-pulmonary sepsis, leukemia, or pancreatitis, respectively.

Statistical Analysis

Categorical and continuous variables are presented as counts (percentages) and medians (interquartile ranges [IQRs]), respectively. Logistic regression analyses were conducted to evaluate the relationships between patient characteristics and PARDS outcomes. Any variables with a P <0.2 in the univariate logistic regression analysis were included in a subsequent multivariate logistic regression analysis. Survival curves were generated to analyze the survival outcomes of the direct and indirect PARDS groups. The log-rank test was utilized to compare the survival curves between the two groups. Statistical analyses were performed using Stata software (v13.0; StataCorp, College Station, TX, USA). Statistical significance was defined as P <0.05 (two-tailed test).

Ethical Approval Statement

All procedures were conducted in accordance with the ethical standards of the responsible committees on human experimentation, both institutional and national, and conformed with the 1975 principles of the Helsinki Declaration, as revised in 2008. This study was approved by the Institute of Research Medical Ethics Committee of Shengjing Hospital (approval number: 2022PS489K). As this was a retrospective study, the requirement for informed consent was waived.