If breathing problems occur while diving, the first thing that comes to mind is barotrauma or decompression sickness. A common clinical picture, immersion-induced pulmonary edema (IPE), is little known despite its frequency. However, it can affect anyone who is in the water. The likelihood of divers being confronted with it, for example as first responder, is therefore considerable. All water sports enthusiasts should be aware of this clinical picture.
Pulmonary edema is a condition in which fluid leaks from the pulmonary capillaries into the alveoli. Immersion induced pulmonary edema (IPE) is a special form in which this occurs during immersion in water for reasons that are still poorly understood. IPE is used as a collective term for 2 subtypes, namely Swimming Induced Pulmonary Edema (SIPE) and Scuba Diver's Pulmonary Edema (SDPE). It can have many medical causes, but also occurs in healthy people.
Redistribution of blood into the chest cavity
The causes of IPE are not fully understood and are the subject of controversy. Immersion in water leads to a redistribution of peripheral volume (i.e. blood) into the heart and lungs, as the extremities and abdomen are compressed more by the water pressure (hydrostatic pressure) than the chest. The mechanism is intensified by cold water in particular, which leads to a constriction of the peripheral vessels as protection against cooling and reinforces this effect. Or to put it simply: blood is squeezed out of the arms, legs and abdomen into the chest in the (cold) water. This increases the pressure in the heart and lungs. As a result, fluid is eventually forced from the blood into the alveoli, causing pulmonary edema. This impedes gas exchange, leads to a deficiency of oxygen and is therefore always dangerous.
Although cold water is an important factor, the picture also occurs in warm waters. SIPE seems to affect more physically fit men, e.g. military divers and triathletes, and there is little doubt that exertion per se favors the occurrence of SIPE.
SIPE can hit healthy persons without warning.
Diver's pulmonary edema (SDPE) is more common in middle-aged women and is associated with high blood pressure and heart disease. A specific factor in diving is breathing against negative pressure, i.e. a situation in which the water pressure acting on the chest, which it has to overcome while breathing in, is higher than the pressure of the inhaled air/gas.
Specific conditions when diving
This is the case when breathing through a snorkel, in an unfavorable water position during diving where the head is held well above the chest (e.g. upright position or semi-upright trim), in the event of regulator malfunction, during rebreather diving when the counterlung is positioned above the lungs, i.e. on the back, or when the ADV (automatic diluent valve) is over-tightened, and finally as a result of a high density of breathing gas during very deep dives. Diving suits that or harnesses that are too tight can also contribute to the problem.
Occasionally, pulmonary edema in extreme free diving (pulmonary barotrauma of descent) is also categorized as IPE. In this case, the pressure conditions in the chest change unfavorably, but only after the residual volume has been fully reached in greater depths, which means that the mechanism is somewhat different.
Underestimated incidence
The incidence of SIPE is unclear and is probably greatly underestimated. People with heart disease are particularly at risk, which is why ice swimming poses a risk for them, as has already been discussed in this blog. It is very important to note that SIPE can also affect healthy people, even those who are very well trained.
SIPE should always be considered when coughing, shortness of breath or coughing up blood or foam occur during or immediately after swimming or diving. It is likely that divers misinterpret such symptoms as decompression sickness or barotrauma. SIPE can also be mistaken for (near) drowning.
Rapid response is essential
If SIPE is suspected, leave the water as quickly as possible. If symptoms occur underwater, surface immediately. As much weight as possible should be removed at the surface (e.g. lead, stages and other "junk") so that the body is immersed in the water as little as possible. On land, the patient should be positioned with their upper body raised. High doses of oxygen (15 l/' preferably via a mouth-nose mask with reservoir) should be administered. The emergency services should be alerted immediately and an emergency medical assessment must be carried out in all cases, not least to rule out (acute) heart disease.