Pathophysiological of Drowning

The effects of drowning are multiple, but the initial and primary insult is to the respiratory system, with hypoxaemia being the inevitable result (Case Report 22.1).
The sequence of events that occur with drowning includes the following:

Initial submersion in water preventing air breathing. This is usually followed by voluntary breath-holding. Duration of the breath-holding depends on several factors, which include general physical condition, exercise, prior hyperventilation and psychological factors (see Chapter 61). This is frequently a period when the victim swallows substantial amounts of water.

Fluid aspiration into the airway at the point of breaking the breath-hold. Eventually, the rising arterial carbon dioxide tension (PaCO2) compels inspiration, and fluid is aspirated. Laryngeal spasm may follow the first contact of the glottis with water. While laryngospasm is maintained, the lungs may remain dry; however, the inevitable result of the associated hypoxaemia is that the spasm will eventually also break, and if the victim remains immersed, then aspiration of water into the lungs will follow. Vomiting of swallowed liquid may occur, and this may also be aspirated into the lungs.

Progressive hypoxaemia. This may initially result from oxygen use during voluntary breath-holding and any subsequent laryngospasm, but ultimately it is aspiration of water or regurgitated stomach contents into the gas-exchanging segments of the lungs that provokes persistent and progressive hypoxaemia. The inhalation of water can occur through involuntary diaphragmatic contractions even if the victim is not breathing per se. The presence of water instead of air and the dilution of surfactant function with consequent alveolar atelectasis result in a ventilation-perfusion (V/Q) mismatch with a preponderance of low V/Q units and extensive venous admixture. The resulting hypoxaemia leads to unconsciousness, bradycardia and ultimately asystolic cardiac arrest. Hypoxic brain damage follows within a very short space of time.


CASE REPORT 22.1

Ernie Hazard, age 35: ‘I was thinking “This is it. Just take a mouthful of water and it’s over.” It was very matter of fact. I was at a fork in the road and there was work to do – swim or die. It didn’t scare me. I didn’t think about my family or anything. It was more businesslike. People think you always have to go for life, but you don’t. You can quit….’

The instinct to breathe underwater is so strong that it overcomes the agony of running out of air. No matter how desperate the drowning person is, he or she does not inhale until on the verge of losing consciousness. That is called the ‘break point’.
The process is filled with desperation and awkwardness: ‘So this is drowning…so this is how my life finally ends…. I can’t die, I have tickets for next week’s game’…. The drowning person may even feel embarrassed, as if he or she has squandered a great fortune. He or she has an image of people shaking their heads over this dying so senselessly. The drowning may feel as if it is the last, greatest act of stupidity in his or her life. The thought shrieks through the mind during a minute or so that it takes the panicky person to run out of air.

Occasionally, someone makes it back from this dark world. In 1892, a Scottish doctor, James Lowson, was on a steamship bound for Colombo. Most of the 180 people on board sank with the ship, but Lowson managed to fight his way out of the hold and over the side:

‘I struck out to reach the surface, only to go further down. Exertion was a serious waste of breath and after 10 or 15 seconds the effort of inspiration could no longer be restrained. It seems as if I was in a vice which was gradually being screwed up tight until it felt as if the sternum of the spinal column must break. Many years ago my old teacher used to describe how painless and easy death by drowning was – “like falling about a green field in early summer” – and this flashed across my brain at the time. The “gulping” efforts became less frequent and the pressure seemed unbearable, but gradually the pain seemed to ease up. I appeared to be in a pleasant dream, although I had enough willpower to think of friends at home and the site of the Grampians, familiar to me as a boy, that was brought into my view. Before losing consciousness the chest pain had completely disappeared and the sensation was actually pleasant.

‘When consciousness returned I found myself on the surface. I managed to get a dozen good inspirations. Land was 400 yards distant and I used a veil of silk and then a long wooden plank to assist me to shore. On landing and getting on a sheltered rock, no effort was required to produce copious emesis. After the excitement, sound sleep set in and this lasted three hours, when a profuse diarrhoea came on, evidently brought on by the sea water ingested. Until morning break, all my muscles were in a constant tremor which could not be controlled’.

From Junger S. The Perfect Storm. London: Fourth Estate; 1997, with quotes from James Lowson in The Edinburgh Medical Journal.