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Clinical characteristics and early predictors of post-drowning acute respiratory distress syndrome in children: A retrospective cohort study in Hainan

This retrospective cohort study of 212 pediatric drowning patients in Hainan identifies drowning duration ≥ 5 minutes, lower Pediatric Critical Illness Score, elevated neutrophil-to-lymphocyte ratio, elevated lactate levels, and white-out appearance on chest radiography as key early predictors of post-drowning acute respiratory distress syndrome, which is associated with significantly higher disease severity, organ dysfunction, and mortality.

Original authors: Feng Jiang, Hongdie Chen, Boyi Lin, Yuanlu Chen, Zefu Chen, Shufan Wu

Published 2026-08-13

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CC BY 4.0

Original authors: Feng Jiang, Hongdie Chen, Boyi Lin, Yuanlu Chen, Zefu Chen, Shufan Wu

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the human body as a high-tech city. When a disaster strikes, like a sudden flood, the city's emergency services (the immune system) go into overdrive. Sometimes, in their panic to fix the problem, they accidentally damage the city's own infrastructure. This is what happens in a condition called Acute Respiratory Distress Syndrome, or ARDS. Think of ARDS as a "friendly fire" incident where the lungs, which are supposed to be the city's air filtration plants, get so swollen and filled with fluid that they can't breathe. This often happens after someone drowns, but it's not just about water getting in; it's about the body's chaotic reaction to the trauma. While we know drowning is dangerous, doctors have been trying to figure out exactly which kids are most likely to hit this "friendly fire" wall and end up in the intensive care unit. Is it the type of water? How long they were underwater? Or something else entirely? This question matters because if we can spot the warning signs early, we can rush the most vulnerable patients to the right care before their lungs shut down completely.

This study, conducted by a team of doctors in Hainan, China, acts like a detective story looking back at 212 children who were rescued from drowning and admitted to the hospital. The researchers wanted to solve a specific mystery: What makes some of these kids develop severe lung trouble (ARDS) while others recover without it? They gathered data from two major hospitals, looking at everything from how long the kids were underwater to their blood test results and chest X-rays.

The team found that the story of drowning is more about "time" and "severity" than the type of water. While it was true that more kids who drowned in seawater ended up with ARDS, the study suggests that the water itself isn't the main villain. Instead, the real culprit is how long the child was submerged. If a child was underwater for 5 minutes or longer, their chances of developing ARDS jumped significantly. It's like a timer on a bomb; once it hits the 5-minute mark, the risk of a catastrophic explosion (severe lung injury) goes up, regardless of whether the bomb was in a pool or the ocean.

The researchers also discovered that the body sends out very clear "distress flares" before the lungs fully fail. They identified five key warning signs that act like a dashboard warning light for doctors:

The 5-Minute Timer: Being underwater for 5 minutes or more.
The "Sick Score" (PCIS): A lower score on a standard test that measures how sick a child is overall.
The Blood Ratio (NLR): A specific ratio of white blood cells that indicates the body is in a state of high alarm.
The Fuel Gauge (Lactate): High levels of lactate in the blood, which is like a sign that the body's cells are running out of oxygen and switching to emergency backup power.
The "White-Out" Photo: A chest X-ray where the lungs look completely white instead of black, meaning they are filled with fluid.

The study showed that children who had these warning signs were much more likely to need a breathing machine, stay in the hospital longer, and unfortunately, face a higher risk of death. Interestingly, the study explicitly ruled out the old idea that the type of water (fresh vs. salt) is the deciding factor. While seawater drownings were more common in the severe group, the math showed that once you account for how long the child was underwater and how sick they were, the water type didn't actually matter. The duration of the submersion was the true independent predictor.

In short, this paper suggests that when a child is rescued from drowning, doctors shouldn't just worry about the water they swallowed. They should immediately check the clock (was it over 5 minutes?), look at the child's overall "sick score," check their blood for oxygen starvation signs, and take a quick X-ray. If those "distress flares" are lit, the child is likely on a path to severe lung trouble and needs aggressive care right away. The authors are careful to note that while these findings are strong, they come from a specific region and a retrospective look at past cases, so they are a powerful guide for now, but they hope future studies will confirm these rules for everyone.

Technical Summary: Clinical Characteristics and Early Predictors of Post-Drowning ARDS in Children

Problem Statement
Drowning remains a significant cause of pediatric mortality and morbidity, particularly in coastal regions like Hainan, China. While the systemic consequences of drowning—including acute respiratory failure, neurological injury, and multiple organ dysfunction syndrome (MODS)—are well-documented, specific evidence regarding the clinical characteristics and early predictors of post-drowning Acute Respiratory Distress Syndrome (ARDS) in children is limited. Previous studies have largely focused on broad "lung injury" or radiographic abnormalities rather than rigorously defined ARDS as a severe respiratory endpoint. Furthermore, the relative impact of water type (seawater vs. freshwater) versus submersion duration on ARDS development remains unclear in pediatric populations. This study aims to characterize the clinical features of post-drowning ARDS in children and identify independent early predictors to facilitate risk stratification and clinical decision-making.

Methodology
This retrospective cohort study was conducted between January 2016 and December 2025 at two tertiary referral centers in Hainan: Sanya Maternal and Child Hospital and Hainan General Hospital.

Study Population: The initial review identified 404 pediatric drowning cases. After applying inclusion criteria (e.g., confirmed drowning history, available submersion duration, survival to hospital arrival, age <18 years, PICU admission) and exclusion criteria (e.g., non-accidental drowning, pre-existing respiratory illness, treatment withdrawal), 212 patients were included in the final analysis.
Grouping: Patients were categorized into an ARDS group ( $n=78$ ) and a non-ARDS group ( $n=134$ ) based on the Pediatric Acute Lung Injury Consensus Conference-2 (PALICC-2) criteria.
Data Collection: Variables included demographic data, drowning specifics (water type, duration), disease severity scores (GCS, Pediatric Critical Illness Score [PCIS]), laboratory parameters (WBC, NLR, CRP, lactate, pH, BE), imaging findings (white-out appearance), and outcomes (MODS, infection, mechanical ventilation, mortality).
Statistical Analysis: Univariate comparisons were performed using t-tests, Mann–Whitney U tests, or chi-squared tests. Candidate predictors were screened using Least Absolute Shrinkage and Selection Operator (LASSO) regression. Variables were further refined using Variance Inflation Factor (VIF) assessment, Spearman correlation analysis, and clinical judgment to address multicollinearity (e.g., selecting Lactate over pH/BE). Finally, a multivariable binary logistic regression model was constructed to identify independent predictors of post-drowning ARDS.

Key Results

Incidence and Severity: The incidence of ARDS among the cohort was 36.8%. Children with ARDS exhibited significantly greater disease severity compared to the non-ARDS group, characterized by longer submersion durations, higher rates of seawater drowning, irregular breathing, prolonged capillary refill time, elevated inflammatory markers (WBC, NLR, CRP), and decompensated metabolic acidosis.
Outcomes: The ARDS group had significantly higher rates of concomitant infections, MODS, and the need for invasive mechanical ventilation (IMV). They also experienced longer PICU stays and a higher in-hospital mortality rate (11.5% vs. 1.5% in the non-ARDS group).
Independent Predictors: After multivariable logistic regression, five factors were independently associated with the development of post-drowning ARDS:
1. Drowning duration ≥ 5 minutes: Odds Ratio (OR) 2.731 (95% CI, 1.132–6.589; $P=0.025$ ).
2. Pediatric Critical Illness Score (PCIS): Lower scores were associated with higher risk (OR 0.889 per 1-point increase; 95% CI, 0.848–0.933; $P<0.001$ ).
3. Neutrophil-to-Lymphocyte Ratio (NLR): Higher ratios increased risk (OR 1.536; 95% CI, 1.208–1.952; $P<0.001$ ).
4. Lactate Level: Elevated levels were a strong predictor (OR 1.929; 95% CI, 1.465–2.540; $P<0.001$ ).
5. White-out Appearance on Chest Radiography: This imaging finding showed the largest effect size (OR 5.369; 95% CI, 1.990–14.482; $P<0.001$ ).
Water Type: While seawater drowning was more frequent in the ARDS group in univariate analysis, it did not remain a statistically significant independent predictor after adjusting for submersion duration and overall illness severity.

Significance and Claims
The authors claim that this study provides a focused characterization of post-drowning ARDS as a distinct, severe clinical entity rather than a general lung injury. The primary significance lies in identifying specific, early clinical signals that can aid in front-loaded risk stratification in emergency and PICU settings.

Clinical Utility: The study suggests that vigilance for ARDS is warranted in children presenting with a submersion duration of ≥5 minutes, elevated NLR and lactate levels, lower PCIS scores, and a "white-out" appearance on initial chest radiography.
Pathophysiological Insight: The findings support the contemporary view that the duration of submersion is a more critical determinant of ARDS risk than the type of water aspirated, as both pathways likely converge on similar downstream lung injury mechanisms.
Tool Validation: The study highlights the utility of the PCIS, a locally developed scoring tool, as a robust indicator of global critical illness severity in drowning cases, outperforming the Glasgow Coma Scale (GCS) in this specific context.
Imaging Interpretation: The "white-out" appearance is framed not as a synonym for ARDS but as a severe early imaging phenotype indicating advanced alveolar-capillary barrier injury, serving as a high-risk warning signal for clinicians.

The authors conclude that post-drowning ARDS represents a complex syndrome involving both pulmonary injury and systemic critical illness, and that the identified predictors can help clinicians identify high-risk children before ARDS is fully established. They acknowledge limitations regarding the retrospective nature of the study and potential recall bias regarding submersion duration, calling for further validation in larger multicenter cohorts.

Technical Summary: Clinical Characteristics and Early Predictors of Post-Drowning ARDS in Children

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