In recent years there has been a growing interest in Immersion Pulmonary Oedema (IPO) as a factor within diving incidents. Although originally reported in the 1980s the condition was until recently thought to be rare. 

Increasing awareness of IPO

Until recent times the condition was thought to be rare but within the last 5-6 years consideration of the circumstances of diving incidents appears to be showing evidence of IPO being a significant factor. BSAC began highlighting the possibility within the Annual Diving Incident Report from 2016 onwards and Dr Peter Wilmshurst has presented on the subject at two BSAC Diving Conferences (2014 & 2017). 

Recently within the BSAC Annual Incident Report a number of the incidents described in the associated synopses have been confirmed by medical assessment as involving IPO in the casualty; a number of divers survived by immediately leaving the water and attending hospital.

To date 24 incidents have been identified in the entire database (1997-2018) where IPO has been confirmed; and for the 2016-2018 reporting years 29 incidents have been identified where IPO is suspected of being a factor from the synopsis using the factors described within the Annual Reports in recent years. 

Since highlighting the importance of IPO for divers in 2014 a number of articles, including personal experiences of suffering IPO, have been published in SCUBA magazine raising awareness. 

Pulmonary Oedema may be confused with drowning as both conditions result in fluid collecting in the lungs. First Aid treatment is however likely to be the same for both. 

Causes of IPO 

When we are immersed in water, the hydrostatic pressure causes compression of leg veins. As a result, blood that normally pools in the legs is pushed centrally into the chest. The increased central blood volume increases the pressure in the alveolar capillaries and may cause fluid to leak into the lungs and cause difficulty breathing and if not corrected can cause death. 

It has been known for some time that high blood pressure carries increased risk of pulmonary oedema, which is why it forms one of the screening questions on a diving medical form. What was previously less understood is that very strenuous exercise could trigger IPO. This had previously been reported in military divers under extremes of training. That level of extreme exercise might arise in diving for example when attempting a rescue of another diver or fighting a current. 

Avoidance of IPO 

IPO is the result of a combination of immersion in water and the body’s response to that immersion. Other than avoiding entering the water in the first place some simple steps may help reduce the risk. 

  • Hypertension - high blood pressure can contribute to the risk. Divers with high blood pressure should seek specialist advice from a Medical referee 
  • Hydration - divers should NOT drink excessive fluids prior to a dive. 
  • Exercise - extreme levels of exercise can contribute to IPO even in very fit individuals and so where possible minimise the need to extreme exercise

Recognition of IPO 

BSAC are continuing to consult with an expert to ascertain if IPO is likely in incidents where the description of the incident implies an IPO may have occurred. Whilst the body of information and evidence develops we believe it continues to be important to remind divers to be aware of factors that could indicate IPO which include:- 

  • Divers with breathing difficulties when not exercising particularly strenuously. Breathing difficulties may be indicated by rapid, uneven or heavy breathing, or coughing uncontrollably. 
  • Confusion, swimming in the wrong or random directions. 
  • Inability to carry out normal functions, whilst appearing to have to concentrate on breathing. 
  • Belief that a regulator is not working properly. 
  • Indication of ‘out of gas’ when their regulator(s) are found to be working correctly and with adequate gas supplies. 
  • Divers refusing or rejecting an alternate source when ‘out of gas’. 
  • Indication of difficulty of breathing when on the surface. 

Treatment of IPO 

Advice from the medical experts at this time is that if you experience breathing difficulties underwater you should terminate the dive and ascend safely and exit the water. If you recognise any of the above factors in a buddy then assist them from the water as quickly as it is safe to do so. Once out of the water the casualty should: 

  • sit upright if conscious, 
  • be given oxygen, 
  • keep warm, 
  • do NOT give fluids 

and it is essential that medical advice be sought.

Download this IPO Guidance as a pdf

Watch as Dr Peter Wilmshurst presents his Immersion pulmonary oedema explained presentation at the 2017 BSAC Diving Conference. 


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Download Instructor Guidance on IPO

The latest guidance for instructors on the condition Immersion Pulmonary Oedema (IPO) in divers and has been produced covering the key points in considering raising awareness for students and any divers.

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Immersion Pulmonary Oedema (IPO) articles

BSAC publishes guidance for divers, including snorkellers, on the condition Immersion Pulmonary Oedema (IPO) and how to avoid, recognise and provide first aid treatment.

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