Immersion Pulmonary Oedema
We have some absolutely fantastic scuba diving up here in the North East of England and Northumberland. With fantastic dives just a short drive from Newcastle – at Whitley Bay, Cullercoats, Sunderland and out of Blyth, we have lots of scuba divers too! Scuba divers, snorkellers and open water swimmers need to know about Immersion Pulmonary Oedema. We need to know some scuba diving first aid too…
In a rush? Here’s the short version…
Immersion Pulmonary Oedema is an accumulation of fluid in the lungs, in a casualty who has been immersed in water. This makes it more difficult for oxygen to be absorbed into the blood and for carbon dioxide to be removed – potentially leading to unconsciousness, cardiac arrest and death.
Those affected may be struggling to breathe, appear confused and/or believe their regulator isn’t working correctly.
What scuba diving first aid is required? They need to exit the water as quickly and safely as possible and be provided with 100% oxygen if available. They need to be kept warm and immediate medical assistance should be sought.
Here’s the science bit… What is Immersion Pulmonary Oedema?
Immersion Pulmonary Oedema (IPO) is a form of pulmonary oedema – an accumulation of fluid in the tissues of the lungs in those who are immersed in water. In the US, IPO is often called IPE, as they call it Immersion Pulmonary ‘Edema’. We’ll refer to the term IPO here.
Until recently, IPO was thought to be quite rare. However, over the last few years more evidence has emerged suggesting IPO is a significant factor in diving incidents. In fact, there’s mounting evidence that IPO probably causes more deaths in scuba divers than any other condition. The precise number of deaths due to IPO is still unknown, because some pathologists still mistake IPO for drowning, due to similar presentation of the lungs in both cases.
What causes Immersion Pulmonary Oedema?
Lung alveoli are microscopic air sacs surrounded by capillaries. A very thin layer of tissue separates each air sac from the blood in the capillaries that surround it. This membrane is thin enough to allow carbon dioxide to diffuse easily out of the blood and oxygen to diffuse in to the blood, but prevents the water in blood plasma from diffusing out to fill the alveoli.
When a person is immersed in water, the hydrostatic pressure causes compression of their leg veins. This means that blood that normally pools in the legs is pushed centrally into the chest. This increased central blood volume increases the pressure in the alveolar capillaries. If the alveolar capillary pressure exceeds critical level, plasma is forced into the alveolar sac as oedema fluid.
What does this mean?
Pulmonary oedema in the alveoli makes it more difficult for oxygen to diffuse into, and carbon dioxide to diffuse out of the alveolar capillary blood. Because of this, the person becomes breathless, starts to cough and may cough up frothy or blood stained sputum. The person may then start to act oddly as hypoxia (reduced oxygen content of blood) affects the brain. If hypoxia is severe, the person will become unconscious. If a scuba diver is hypoxic at depth, the hypoxia will worsen during ascent because ascent reduces the partial pressure of the oxygen in the lungs and arterial blood. Hypoxia can lead to unconsciousness, cardiac arrest and death.
How Do I Avoid Immersion Pulmonary Oedema?
- Hypertension/high blood pressure and pre-existing heart disease can increase the risk of IPO. The alveolar capillary pressure is often higher than normal in people with these conditions before immersion. They get more vasoconstriction on cold exposure than other people. This is one of the reasons such questions are asked on a diving medical form – so be honest!
- Over-hydration – scuba divers should NOT drink excessive fluids before a dive in an attempt to over-hydrate. Excessive hydration can increase the risk of IPO as it can have an additive effect on the increase in alveolar capillary pressure resulting from immersion.
- Exercise – extreme levels of stress or exercise can contribute to Immersion Pulmonary Oedema even in fit individuals. Where possible, minimise the need for extreme exercise during a dive.
What else do I need to know about Immersion Pulmonary Oedema?
- Older divers tend to have higher alveolar capillary pressures – meaning that a critical level may be reached more easily.
- Immersion in cold water (such as off the North East of England coast!) means constriction of blood vessels is greatest in the cold, although IPO can occur in tropical waters too.
How Do I Recognise Immersion Pulmonary Oedema?
There are a few signs that scuba divers should look out for:
- Divers with breathing difficulties, even though they’re not exercising particularly strenuously. Breathing may be rapid, uneven or heavy. Sometimes the person may be coughing uncontrollably. Underwater, look for changes in exhaled bubbles.
- Confusion, e.g. the person swimming in random directions.
- The person may appear to struggle with carrying out normal functions and may appear to be over-concentrating on breathing.
- The person may feel or express that their regulator isn’t working properly. They may even indicate that they are ‘out of gas’ – although their regulator(s) are working properly with adequate gas supplies.
- The person may appear to be having difficulty breathing when on the surface.
Scuba Diving First Aid – How Do I Treat Immersion Pulmonary Oedema?
If anyone is experiencing breathing difficulties underwater, the dive should be terminated by safely ascending and exiting the water. If you suspect IPO in a buddy, assist them to exit the water as quickly as is safe to do so. They should not be left to surface alone as the reduction in partial pressure of oxygen in the blood and brain may quickly lead to unconsciousness.
Once out of the water:
- Get the casualty to sit upright if conscious, as this improves gas (oxygen/carbon dioxide) transfer. If unconscious, they’ll need to be in the Recovery/Safe Airway Position.
- Provide 100% oxygen if available.
- Keep the casualty warm.
- Don’t give the casualty fluids.
- Seek immediate medical assistance.
A diver who has had IPO is at risk of experiencing it again. Medical investigation by someone who is familiar with diving medicine is important to rule out a cardiac problem.
Want to learn to dive in the North East? Definitely check out our good friends over at The Fifth Point Diving Centre!