Wilderness and Rescue Medicine 8th Edition

Chapter 21: Water-Related Injury

Trapped under water, most untrained people will inhale within a minute or two. Laryngeal spasm may protect the lungs for a short period, but ulti- mately water will infiltrate the alveoli, causing hypoxia and unconsciousness. Without rescue, brain injury and death follow shortly. You can condition your brain and respiratory system, or temporarily manipulate your blood chemistry by hyperventilating, to allow for longer breath holding. Practiced free divers can routinely achieve breath hold times of 5 and 6 minutes. The world record is over 11 minutes. With extreme discipline, these people are able to resist the dia- phragmatic spasms and intense urge to inhale long enough to become hypoxic with significantly altered mental status. At this point, the swimmer usually recognizes the need to surface and begin breathing and the timer stops. SCUBA (self-contained underwater breathing apparatus) has largely eliminated the need for pro- longed breath holding underwater, but it carries its own set of anticipated problems. Compressing air allows for breathing against water pressure but creates the potential for significant pressure dif- ferentials across body structures as water pressure increases and decreases with changes in depth. A ruptured ear drum is a minor example; a ruptured lung is a more serious consequence of the same problem.

For humans, water is a high-risk environment, but many of us seem to love being near, on, or under it for work and play. Water also plays a role in many natural disasters. Regardless of your loca- tion, or recreation or rescue responsibilities, it is worth knowing something about water-related injury. Drowning Drowning is respiratory distress occurring as a result of a submersion or immersion event (from sustained coughing to respiratory arrest). Your ability to swim has little to do with your ability to drown. One common cause of drowning is the loss of muscular coordination due to the rapid shell cooling that occurs in cold water. Sometimes, sudden immersion in very cold water causes a reflex gasp that fills the lungs and immediately deprives the victim of oxygen. Self- extrication efforts may be hampered by bulky clothing and boots or by being pinned down by a fast current. Even the strongest swimmer can drown in these conditions. Unless interrupted by rescue, the final act is the loss of conscious- ness and the inhalation of a substantial amount of water. Cardiac arrest and death follows within a few minutes.