The child is a 2-year-old who fell into a pool. He was retrieved from the pool by a family member but was not breathing. The family member started CPR, and the ambulance brought him to the hospital. What factors are important in determining the level of hypoxemia that the child may have experienced during the submersion? Select all that apply.

The level of hypoxemia that the child may have experienced during the submersion depends on several factors, but the most important ones are: The **temperature of water**: Cold water can induce a diving reflex, which lowers the heart rate and oxygen consumption, and may protect the brain from hypoxic injury. Cold water can also cause laryngospasm, which prevents water aspiration but also impairs gas exchange. The **amount of time the child was submerged**: The longer the submersion, the more severe the hypoxemia and the higher the risk of brain damage and death. The survival rate decreases significantly after 5 minutes of submersion. The other factors are less relevant or not directly related to the level of hypoxemia: The **weight of the child**: This may affect the buoyancy and the ability to float or swim, but not the oxygen consumption or gas exchange during submersion. The **oxygen concentration of the ambient air**: This may affect the pre-submersion oxygen saturation, but not the rate of oxygen depletion or gas exchange during submersion. The **witnessing of the fall into the pool**: This may affect the time to rescue and resuscitation, but not the level of hypoxemia during submersion.