International diving medical experts have come up with a joint position statement on the subject of immersion pulmonary oedema (IPO), the condition that has come to concern scuba divers as well as snorkellers and other surface swimmers.
And a key takeaway is that the specialist group strongly advise divers with previous suspected or confirmed IPO to think hard before pressing on with further compressed-gas diving.
Such divers should consult a doctor or cardiologist well-versed in diving medicine before considering resuming their in-water activities, they say – because surviving one incident does not indicate that they will survive the next.
Divers who have experienced IPO should also be fully investigated to identify any disease that predisposed them to the condition, say the experts, because it might have implications unrelated to future diving. IPO has been found to occur in divers with significant coronary disease, cardiac valve disease, cardiomyopathy and renal artery stenosis among other ailments.
Medical experts belonging to the influential South Pacific Underwater Medicine Society (SPUMS) Neil Banham, David Smart and Simon J Mitchell produced the report in consultation with UK Diving Medical Committee (UKDMC) members Peter Wilmshurst, Mark S Turner and Philip Bryson.
All had attended a workshop held at the SPUMS 52nd annual scientific meeting in Fiji in May to discuss the topic.
The purpose of the statement is to provide medical practitioners with guidance on IPO and diving, and in particular on emergency management and the advisability of divers returning to the sport following an episode in which IPO has been either diagnosed or is strongly suspected.
IPO risk factors
IPO is a build-up of fluid in the lungs, affecting the casualty’s ability to breathe and potentially lethal. With oxygen not getting into the blood and the body unable to expel carbon dioxide, the condition also occurs in surface swimmers and in scuba divers can be exacerbated by their breathing apparatus.
Personal risk factors for IPO identified so far include having experienced a previous episode; being female; age; and suffering from hypertension and/or pre-existing cardiovascular disease, according to the statement.
Extrinsic factors include colder waters; regulators that cause excess negative inspiratory pressures; rebreathers; severe exertion and excessive hydration. Ascents can also be problematic, particularly on open-circuit, with symptoms related to hypoxia occurring or worsening on ascent and/or after surfacing as the partial pressure of oxygen (PO2) decreases.
If divers who have survived an IPO episode choose to dive again despite medical advice, they should do so only after satisfactory treatment or resolution of any associated disease or risk factors identified, say the experts.
They should also be aware of potential risk-mitigation strategies, such as using only high-quality, well-fitting thermal protection, and the need to avoid when under water heavy exertion, overhead environments or decompression diving.
They should dive only if sure that emergency oxygen will be readily available, and should avoid pre-dive overhydration, while CCR divers should steer clear of using back-mounted counterlungs.
Limiting diving depths is not an acceptable IPO risk-mitigation strategy, agree the experts, who stress that no known association exists between IPO and decompression illness (DCI).
If a diver develops IPO on a deep dive, it will take longer to surface and exit the water. It also introduces additional risks, particularly on open-circuit, as PO2 decreases and a head-up attitude in the water results in negative-pressure breathing.
With an established link between experiencing IPO and subsequently developing hypertension, divers who have survived IPO should have their blood pressure checked regularly for life.
Signs and symptoms
Symptoms of IPO can include coughing; breathlessness; frothy sometimes pink sputum; moist or rattling breath sounds and wheezing; chest tightness; cyanosis and hypoxaemia (low blood oxygen levels); confusion; agitation; unconsciousness and cardio-respiratory arrest.
Divers should be aware of signs to look out for both in themselves or in a buddy: those listed above as well as rapid breathing apparent from exhaled bubbles on open circuit or a fast-falling pressure gauge; mistaken belief of being out of breathing gas or having malfunctioning breathing equipment; panic and compulsion to ascend.
In the event of a suspected IPO incident, the advice is for divers to end the dive immediately and leave the water as soon as possible.
While ascents need to be carried out safely, safety stops can be omitted if necessary, as can compulsory decompression stops in severe cases, in which case oxygen must be administered as soon as possible. BCs should not be over-inflated at the surface and the emergency services should be notified at once.
The casualty’s chest should be supported upright for breathing efficiency and tight diving gear and wetsuit removed, though the diver needs to be kept warm.
Further clinical guidance on emergency treatment and assessment for future diving is provided for medical staff in the joint position statement, which was published recently by SPUMS in Diving and Hyperbaric Medicine Vol 54.
Also on Divernet: What happens to a diver charged with manslaughter?, Red flags for snorkellers: how to stop the quiet deaths, Snorkel-deaths report questions IPO findings, ‘The dive that turned into my fight for life’
I as diagnosed with diffuse bilateral pulmonary embolism.how does this differ from IPO and I was told I can still dive. Has my status changed? Can I still dive?
As I understand it, what you describe is a completely different medical condition but, as in all such cases, it is best to consult a doctor with diving medical knowledge.