A near-drowning patient arrives by ambulance. Pink foam comes out of his lungs, out of his nose. He coughs to clear it, gasps, gags, vomits repeatedly. The oxygen mask over his face panics him. You coax him into letting you replace it and keep it there. "This is oxygen. It’ll help."
But oxygen wasn’t enough for him. He had to be sedated, intubated (tube into lungs) and ventilated mechanically. Finally, after the intensive care unit and then several more days in the hospital, he was released. Emergency department staff were quite relieved to hear from his family that he left with no deficits, no apparent permanent damage.
That was a young and fit patient, who’d been pushed into a pool and pulled quickly out. He was cared for by paramedics on the way to the hospital. It only happened to him once. Still, he could have died. He could have been disabled. People worked for days to prevent that.
The foam coming out of his nose was pink with blood, seeping through delicate membranes. Alveoli are the tiny fragile balloons in our lungs where oxygen transfers from the air into our red blood cells. Water in lungs washes away the surfactant that keeps those alveoli walls from sticking together when we exhale. They can collapse without it, be less able to exchange oxygen, and with pulmonary edema (fluid accumulation in the lungs), that can lead to death up to 72 hours later, from secondary or "parking lot" drowning.
Fresh water in our lungs gets into our blood through those membranes, and can dilute it enough to cause red blood cells to burst (hemolysis). Hemolysis causes a disturbance in electrolyte balance that can lead to ventricular fibrillation in our hearts, and death. Hemolysis can damage our kidneys as well, leading to acute renal failure, and slower death. Plus, fewer red blood cells remain to carry what oxygen is available to all our organs.
Infection, pneumonia, possibly sepsis, are a third category of risk when liquids enter our lungs. Water itself may contain bacteria; mouths and noses always contain bacteria. Vomit contains bacteria, acid, and often solids, all of which damage lung tissue. EMTs are told to assume that all near-drowning patients will vomit during resuscitation, so they will be alert to the risk that vomit could be aspirated into our lungs.
Laryngospasm is a reflex reaction to water in airways, in both conscious and unconscious patients. It clamps shut and seals our airways from water, but also from air. The trach-kit required in the room for later waterboardings was there to cut an opening directly into the trachea, into the throat below the larynx, if laryngospasm persisted. Our thyroids are wrapped around the trachea there, though, and will bleed profusely if nicked.
Finally, as we know, depriving our brains of oxygen injures them. From published reports, people who have been waterboarded repeatedly often seem brain-damaged.
I’m only a former paramedic. No doubt an MD could provide more complete information and context.
More information:
"A Near-Drowning Victim With Pneumonia and Hemiparesis," at www.medscape.com/viewarticle/431130_print
"Swimming Hall Accident," at www.jems.com/news_and_articles/articles/swimming_hall_accident.html