Sickle Cell
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Sickle Cell "trait" is the term used for someone who has one recessive sickle cell gene but not sickle cell itself. No symptoms are associated with the "trait" - no problem. Sickle Cell itself is another matter, and I imagine a contraindication to diving, though a diving physician's evaluation on a case-by-case basis may let some dive.
Rick
Rick
BillP
Senior Member
Hi Maggie:
As Rick has already pointed out, sickle cell disease and sickle cell trait are inherited disorders where the gene that controls the formation of hemoglobin in the blood is abnormal. Most of our genes are "paired"- one inherited from the father and one from the mother. If a person has one copy of the sickle gene they have "sickle cell trait" and if they have two copies of the gene they have "sickle cell disease". People with sickle cell trait still have some abnormal hemoglobin, they just have less abnormal hemoglobin that someone with sickle cell disease. That means it is less likely for someone with sickle cell trait to have significant anemia or to develop a sickling "crisis", but it's still possible.
I don't know of any studies that specifically look at sickle cell and diving. Peter Bennett and Carl Edmonds in their diving medicine texts and Fred Bove in his booklet Medical Examination of Sport Scuba Divers all say that sickle cell disease is an absolute contraindication to diving (ie, Don't do it). All consider sickle cell trait a relative contraindication to diving (ie, Maybe Ok under certain circumstances). In their "Fitness to Dive" chapter in Bennett's The Physiology and Medicine of Diving Mebane and McIver recommend that people at risk for Sickle Cell Trait be tested. They say if the sickling type hemoglobin (HbS) is over 40% of the total the person should not dive. In Carl Edmond's book, the authors recommend that a diver with sickle trait stay shallower than 18 meters. In his booklet Fred Bove suggests if the person with sickle trait has had significant anemia or has had a sickle crisis, the person should not dive.
There are a couple of potential problems with sickle cell and diving. One of the triggers for a sickle crisis is dehydration. Dehydration is a risk in scuba diving and divers with sickle trait need to be particularly vigilant about staying well hydrated. Hypoxia (lack of oxygen) can trigger a sickle crisis. Hypoxia shouldn't be a big risk in proper sport diving, but it does happen. It is probably a greater risk in diving where gas mixes low in oxygen are used for particularly deep dives. Also, DCS causes hypoxia of the affected tissues. If a diver with HbS develops DCS, the red blood cells in the area affected by the DCS will likely have some sickling of the red blood cells making the obstruction of blood vessels and the hypoxia worse.
From my reading it would seem that people with sickle cell disease should not dive. But the natural history of sickle cell disease and the success of treatment has improved remarkably in just the last few years. Asthma used to be considered an absolute contraindication to diving too, but that taboo is being revisited and reevaluated by many diving authorities. Perhaps the same will be true for sickle cell disease. People with sickle cell trait can dive under the proper conditions after evaluation and clearance by a physician knowledgeable in the issues of hematology and diving. Divers with sickle cell trait should take particular care to avoid dehydration, they should monitor their depth and gas supply particularly closely, and they should take extra precautions to avoid DCS- dive conservatively.
HTH,
Bill
As Rick has already pointed out, sickle cell disease and sickle cell trait are inherited disorders where the gene that controls the formation of hemoglobin in the blood is abnormal. Most of our genes are "paired"- one inherited from the father and one from the mother. If a person has one copy of the sickle gene they have "sickle cell trait" and if they have two copies of the gene they have "sickle cell disease". People with sickle cell trait still have some abnormal hemoglobin, they just have less abnormal hemoglobin that someone with sickle cell disease. That means it is less likely for someone with sickle cell trait to have significant anemia or to develop a sickling "crisis", but it's still possible.
I don't know of any studies that specifically look at sickle cell and diving. Peter Bennett and Carl Edmonds in their diving medicine texts and Fred Bove in his booklet Medical Examination of Sport Scuba Divers all say that sickle cell disease is an absolute contraindication to diving (ie, Don't do it). All consider sickle cell trait a relative contraindication to diving (ie, Maybe Ok under certain circumstances). In their "Fitness to Dive" chapter in Bennett's The Physiology and Medicine of Diving Mebane and McIver recommend that people at risk for Sickle Cell Trait be tested. They say if the sickling type hemoglobin (HbS) is over 40% of the total the person should not dive. In Carl Edmond's book, the authors recommend that a diver with sickle trait stay shallower than 18 meters. In his booklet Fred Bove suggests if the person with sickle trait has had significant anemia or has had a sickle crisis, the person should not dive.
There are a couple of potential problems with sickle cell and diving. One of the triggers for a sickle crisis is dehydration. Dehydration is a risk in scuba diving and divers with sickle trait need to be particularly vigilant about staying well hydrated. Hypoxia (lack of oxygen) can trigger a sickle crisis. Hypoxia shouldn't be a big risk in proper sport diving, but it does happen. It is probably a greater risk in diving where gas mixes low in oxygen are used for particularly deep dives. Also, DCS causes hypoxia of the affected tissues. If a diver with HbS develops DCS, the red blood cells in the area affected by the DCS will likely have some sickling of the red blood cells making the obstruction of blood vessels and the hypoxia worse.
From my reading it would seem that people with sickle cell disease should not dive. But the natural history of sickle cell disease and the success of treatment has improved remarkably in just the last few years. Asthma used to be considered an absolute contraindication to diving too, but that taboo is being revisited and reevaluated by many diving authorities. Perhaps the same will be true for sickle cell disease. People with sickle cell trait can dive under the proper conditions after evaluation and clearance by a physician knowledgeable in the issues of hematology and diving. Divers with sickle cell trait should take particular care to avoid dehydration, they should monitor their depth and gas supply particularly closely, and they should take extra precautions to avoid DCS- dive conservatively.
HTH,
Bill
From everything I've been able to find, people with the trait typically can't generate a crisis unless they combine LOW oxygen (e.g. high altitude) with strenuous exercise. And since SCUBA is a HIGH oxygen sport, the trait shouldn't be a factor - or am I missing something here, Doc?
Rick
Rick
BillP
Senior Member
Yes Rick, you're missing something. I think you're missing the paragraph where I said:
Are you trying to claim that hypoxia is impossible in scuba diving? Divers never engage in strenuous exercise? Tissue perfusion and oxygenation is improved in DCS? Bennett, Edmonds, and Bove are all wet and don't have a clue? Or were you saying something else that I missed?
Are you trying to claim that hypoxia is impossible in scuba diving? Divers never engage in strenuous exercise? Tissue perfusion and oxygenation is improved in DCS? Bennett, Edmonds, and Bove are all wet and don't have a clue? Or were you saying something else that I missed?
DannyBoy
Guest
I think what BillP said is right on about special risks inherent to sickle cell patients interested in diving. One other reason why sickle cell patients shouldn't dive (again, I am only talking about pts. with sickle cell disease, not trait) is that the symptoms of sickle cell crisis and DCS can be very similar. Both can present as pain in the joints, which poses a diagnostic problem because the treatment of DCS is quite different than the treatment of a sickle cell crisis. I apologize if someone else has pointed this out, and I missed it.
Take care,
DB
Take care,
DB
Thank you BillP. That is exactly what I wanted to know. I was pretty sure that people with Sickle Cell would be extremely unwise to dive and would be unlikely to obtain the necessary medical clearance. I have seen patients in crisis states and the idea of that occurring underwater fills me with horror. People with sickle cell trait however I wasn't sure could or should dive. The dehydration factor I was aware of as an increased risk for DCS but the O2 factor I was unsure of. If a person with sickle cell trait (HbS under 40%) kept within the 18 metre depth limit, dived only in non-stress conditions and also breathed an oxygen rich mix (Nitrox) would this significantly increase the safety margins?
BillP
Senior Member
Hi Maggie:
Glad to help. While I still
your synopsis looks like a reasonable synthesis of the recommendations of leading dive medicine authorities on sickle cell trait and diving.
BTW, Dr. Campbell (Scubadoc) has a page on his web site about sickle cell at http://www.scuba-doc.com/sickle.htm that discusses sickle cell testing of divers in the UK. You might find it helpful. Apparently the BSAC might require sickle cell testing of divers statistically at risk for having the sickle cell gene (eg of Afro-Caribbean origin or there was a history of sickle cell disease in the family)? He also mentions a study that suggests you can be less restrictive about sickle cell trait. Interesting.
Bill
Glad to help. While I still
your synopsis looks like a reasonable synthesis of the recommendations of leading dive medicine authorities on sickle cell trait and diving.
BTW, Dr. Campbell (Scubadoc) has a page on his web site about sickle cell at http://www.scuba-doc.com/sickle.htm that discusses sickle cell testing of divers in the UK. You might find it helpful. Apparently the BSAC might require sickle cell testing of divers statistically at risk for having the sickle cell gene (eg of Afro-Caribbean origin or there was a history of sickle cell disease in the family)? He also mentions a study that suggests you can be less restrictive about sickle cell trait. Interesting.
Bill
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Hi a-siren,
Nothing recent that I was to locate. However, here is some older research:
1. Aviat Space Environ Med. 1991 Nov;62(11):1099-102.
Sickle cell anemia trait in the military aircrew population: a report from the Military Aviation Safety Subcommittee of the Aviation Safety Committee, AsMA.
Voge VM, Rosado NR, Contiguglia JJ.
Military Aviation Safety Subcommittee, Aerospace Medical Association, Alexandria, VA.
The question of whether sickle cell trait (SCT) is potentially dangerous to military aircrew personnel who have it and, consequently, whether such individuals should be allowed to fly in military aircraft is a very emotional issue. This article traces the evolution of how the U.S. military has dealt with the problem, and the present status of individuals with SCT in the U.S. military aviation community. Extensive studies and means for subjectively evaluating the problem were instituted by the Department of Defense in 1981, after making the decision not to restrict aircrew with the trait from aviation duties. All research projects and educational programs were abruptly stopped in 1985. Today, there are no actual restrictions on individuals with SCT for duty in the aviation and diving communities.
Still, it appears prudent for the diver with SCT to observe the precautions discussed by Dr. BillP.
Regards,
DocVikingo
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.
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