Dive response of children in relation to cold-water near-drowning

Area of Science:

• Physiology
• Pediatric Research
• Environmental Medicine

Background:

• The mammalian dive response is a physiological adaptation to breath-hold diving, involving bradycardia and peripheral vasoconstriction.
• Understanding the dive response in children is crucial for assessing their survival chances in cold-water drowning incidents.

Purpose of the Study:

• To compare the dive response strength, measured by breath-hold duration (BHD) and bradycardia, between children and adults.
• To investigate the relationship between age and BHD in children during simulated dives.
• To evaluate the potential contribution of the dive response to the resuscitation of children after cold-water near-drowning.

Main Methods:

• Simulated dives in 29°C water were conducted on 87 children (4-13 years) and 68 adults (20-68 years).
• Breath-hold duration (BHD) and heart rate changes (bradycardia) were recorded.
• Statistical analyses, including regression analysis, were used to compare BHD and bradycardia between age groups and to assess age dependency.

Main Results:

• Children had a significantly shorter mean BHD (16.1 s) compared to adults (43.0 s), representing only 37.4% of adult BHD.
• In children, BHD was significantly dependent on age (BHD = -1.46 + 2.27 * Age), while no age dependency was observed in adults.
• Only 16.1% of children could sustain a breath-hold of 25 seconds required for full diving bradycardia; their bradycardia levels were not significantly different from adults.

Conclusions:

• The dive response in children is considerably weaker than in adults, primarily attributed to their limited BHD.
• The dive response is unlikely to significantly enhance the prolonged resuscitatibility of children in cold-water near-drowning scenarios.
• Pediatric near-drowning survival in cold water is likely influenced by factors other than the dive response, given its limited efficacy in this age group.