Diving With Nitrox and Blood Donation

[LittleBug]

I am both an active blood donor, and an active diver. I just recently got my Nitrox certification and heard something about blood donations too close to diving with Nitrox would increase the likelihood of oxygen toxicity.

Have any of you heard anything about this?

 

[Gene_Hobbs]

I am both an active blood donor, and an active diver. I just recently got my Nitrox certification and heard something about blood donations too close to diving with Nitrox would increase the likelihood of oxygen toxicity.

I just asked asked DAN to revisit their blood donation statement (Nov 2006). It's funny how this one slipped through the cracks. So, here it is...

Immediately following blood donation, the volume of circulating blood is reduced. Provided the donor eats and drinks normally, blood volume returns to normal within 24 hours. Diving within the first few hours after donating blood is not advisable because of the possibility that reduced blood flow could cause impaired inert gas washout after a dive, and thus an increased risk of decompression sickness. We have no reason to believe that it is necessary to wait more than 24 hours after donation before scuba diving.

There was also an interesting abstract at the 2006 UHMS meeting on hematocrit and DCS. (RRR ID# 3643)

NEUROLOGICAL DECOMPRESSION ILLNESS AND HEMATOCRIT: ANALYSIS OF A CONSECUTIVE SERIES OF 200 RECREATIONAL SCUBA DIVERS.
Newton HB, Burkart J, Pearl D, Padilla W
BACKGROUND: Neurological complications are common in recreational divers diagnosed with decompression illness (DCI). The spinal cord appears to be the region most vulnerable to injury, but the brain, inner ear, and peripheral nerves are also at risk. Prior reports suggest that hemoconcentration, with hematocrit values of 48 or greater, increase the risk for more severe and persistent neurological deficits in divers with DCI. Herein we describe our experience with neurological DCI and hematocrit values in a large series of consecutively treated diver MATERIALS AND METHODS: We performed a retrospective chart review of 200 consecutive recreational divers that received treatment for DCI. Standard statistical analyses were performed to determine if there were any significant relationships between diving-related or demographic parameters, neurological manifestations, and hematocrit RESULTS: In 177 of the 200 divers (88.5percent), at least one severe manifestation of neurological DCI was present. The most common findings were paresthesia, dysesthesia, loss of coordination, and motor weakness. The median hematocrit value was 43, for both male and female divers, with a range of 30 to 61. Hematocrit values did not correlate with diver age (rank correlation = 0.053) or level of diving experience (rank correlation = 0.003). In male divers, the hematocrit did not correlate with the occurrence of severe sensory (p=0.27, Wilcoxon test) or motor (p=0.86, Wilcoxon test) symptoms, including the sub-group with values of 48 or greater. In contrast, female divers with hematocrit values of 48 or greater were significantly more likely to develop motor weakness (p=0.002, Fisher's exact test) and an increased number of severe sensory symptoms (p=0.001, Kendall's tau statistic CONCLUSIONS: Neurological complications are common in recreational divers treated for DCI. Hematocrit values of 48 or higher were correlated with the presence of motor weakness and severity of sensory symptoms in female divers. The hematocrit did not correlate with neurological DCI in male divers.

Dr. Denoble was able to locate one USN diving case report that describes blood donation preceding the dive with DCS. The connection is weak but worth noting.

This subject stated he first noticed a headache of moderate intensity on surfacing. States it seemed to be behind the eyes. No visual disturbances. Had no difficulty during dive clearing air passages of ears or sinuses. This moderate headache lasted about 24 hours. About 1500 he developed a moderate skin rash over right deltoid and upper arm (anteriorly and laterally) which caused no itching. Was first on oxygen on surface for 30 min and rash disappeared. Went home feeling quite well except for slight headache. About 1800 he noticed mild fleeting pains in various joints on right side involving wrist, elbow, knee and ankle on right side. These pains were mild and transient in character and subject did not report for aid as he thought his symptoms were mild and would subside. Slept well. Following AM had only slight headache. Right triceps area was still sore. Seen 14/18 and he had an ecchymotic area about 3” in diameter with two petechial heads over right triceps area. Some induration present indicative of rather deep extravasation of blood. This patient definitely had some peripheral vascular damage. Trauma as a cause for this bruise could not be accounted for. Intravascular bubbles may be the etiological factor. This case should have been given Rx by recompression. Note: this subject gave 1/2 pint of blood to blood donor service on the afternoon of the day preceding dive. This was not known until after his dive was made. This may have some etiological bearing in this case. Said he felt well after giving blood except for slight nausea following donation. Note RBC is slightly down.

and just for fun... (and the sake of completeness)

The donor&#8217;s body replenishes the fluid lost from donation in 24 hours. If not anemic (Hgb<12 Gm/dl) a person can dive in 24 hours after blood donation. It may take up to two months to replace the lost red blood cells. Whole blood can be donated once every eight weeks. The most important part of the blood to the diver is the red blood cell, responsible for the transport of oxygen to the tissues. The fluid part of blood is replenished in about one day. If the diver waits 24 hours and has a normal hematocrit, then diving should be allowed.

Red blood cells are perhaps the most recognizable component of whole blood. Red blood cells contain hemoglobin, a complex iron-containing protein that carries oxygen throughout the body and gives blood its red color. The percentage of blood volume composed of red blood cells is called the &#8220;hematocrit.&#8221; The average hematocrit in an adult male is 47 percent. There are about one billion red blood cells in two to three drops of blood, and, for every 600 red blood cells, there are about 40 platelets and one white cell. Manufactured in the bone marrow, red blood cells are continuously being produced and broken down. They live for approximately 120 days in the circulatory system and are eventually removed by the spleen.

Hope this helps...

Take care

 

[Cheekymonkey]

does that apply to plasma donation as well?

 

[DocVikingo]

Hi Cheekymonkey,

Yes, that applies to plasma donation as well.

The critical element in diving after donation is the loss of blood volume, and a unit of blood is largely a fluid called plasma. Red and white blood cells, platelets and other solid matter make up just a fraction of a given amount of blood.

It is blood flow within capillaries that is primarily responsible for oxygen (02) delivery and inert gas (e.g., nitrogen) removal, and reduced blood volume translates into reduced flow. This why rehydration following whole blood or blood plasma donation is important for safe scuba.

The lowered red blood cell (RBC) count secondary to donation is of relatively little importance as inert gases are not specifically transported in red cells. While 02 is, in a healthy individual the RBCs remaining after blood donation are more than capable of handling all of the body's oxygen demands. Loss of RBCs may result in mild fatigue, and of course divers shouldn't scuba unless feeling up to it, but typically this sensation is very temporary.

Helpful?

Regards,

DocVikingo

 

[DocVikingo]

Hi LittleBug,

While you've been exposed to some excellent educational material for the active blood donor who is also an active diver, it doesn't appear that your specific question has as yet been answered.

You inquire, "I just recently got my Nitrox certification and heard something about blood donations too close to diving with Nitrox would increase the likelihood of oxygen toxicity. Have any of you heard anything about this?"

What you heard is not accurate. Oxygen toxicity, or ox-tox, is also know to divers as the Paul Bert Effect and is a function of excessive concentrations of oxygen within the brain.

Ox-tox can result in seizures, muscle twitching & spasm, nausea & vomiting, dizziness, tunnel vision, ringing in the ears, incoordination, irritability, confusion and anxiety. A number of factors appear to contribute to ox-tox, including the use of nitrox, but blood donation and dehydration are not among them.

In fact, when one considers that red blood cells (RBCs) are responsible for the transport of oxygen (02) within the body, and that blood donation reduces the RBC count, it could be argued that the risks of ox-tox, whether on regular air or nitrox, might actually be reduced. Ditto for dehydration, which reduces blood flow within the capillaries and thereby reduces oxygen transport and diffusion.

Helpful?

Regards,

DocVikingo

 

[Gene_Hobbs]

While you've been exposed to some excellent educational material for the active blood donor who is also an active diver, it doesn't appear that your specific question has as yet been answered.

Sorry Doc, I guess I should have said that this was "all" I could find on blood donation and diving and that O2 Tox concerns were not in any result. Thanks! -G

 

[DocVikingo]

You are a veritable font of information, Mr. Hobbs, and an extremely valuable resource.

We just need to keep in mind that most inquirers to this forum are lay persons and not scientists or physicians and to take care not to lose the forest for the trees.

Regards,

DocVikingo

 

[CameronMartz]

In fact, when one considers that red blood cells (RBCs) are responsible for the transport of oxygen (02) within the body, and that blood donation reduces the RBC count, it could be argued that the risks of ox-tox, whether on regular air or nitrox, might actually be reduced.

Interesting thought, but that raises another question. O2 bound to RBCs does not exert a partial pressure. It is the dissolved O2 present in plasma that is exerting a partial pressure, and the dynamics of this would not likely change based upon a change in hematocrit. It is only the effect of a metabolic demand for O2 that allows the release of 02 from RBCs (due to the drop in partial pressure of dissolved O2).

So the question becomes, if CNS oxtox is a product of O2 partial pressure, do RBCs play any role at all in the equation?

Cameron

 

[DocVikingo]

Hi Cameron,

My argument in that regard was primarily theoretical and a bit extreme.

It is correct that it largely is the effect of a metabolic demand for O2 that allows the release of 02 from RBCs (due to the drop in partial pressure of dissolved O2). However, the amount of dissolved O2 present in plasma has a very high correlation with the amount of O2 bound to RBCs. As such, a drop in hematocrit obviously could have implications. Plasma 02 that is not available cannot diffuse into CNS tissue.

It is very unlikely, however, that the small change in hematocrit occasioned by a routine blood donation in a healthy individual would have any measurable effect on this dynamic.

Regards,

DocVikingo

 

[CameronMartz]

However, the amount of dissolved O2 present in plasma has a very high correlation with the amount of O2 bound to RBCs. As such, a drop in hematocrit obviously could have implications. Plasma 02 that is not available cannot diffuse into CNS tissue.

I don't mean to press the theoretical issue of nitrox and blood donations, but the oxygen transport system and how it is regulated is very relevant to diving, thus I think worth a continued discussion for those who care to follow it.

As it passes through the lungs, PPO2 in plasma is brought to equilibrium pressure with PPO2 of the inspired gas. RBCs serve to "hide" molecules of O2 from the gas laws, so to speak, in effect increasing its solubility in blood. However, the PPO2 of plasma leaving the lungs will be the same regardless of hematocrit level. Equilibrium pressure is equilibrium pressure.

In the body, O2 is metabolized from that dissolved in plasma. This lowers partial pressure of dissolved O2, which allows O2 to dissociate from RBCs and dissolve into the plasma. The entire process is moderated by ordinary gas laws of diffusion, and there is never a condition where there is no dissolved O2 present in plasma, yet O2 bound to RBCs.

Certainly, the higher the hematocrit, the less the partial pressure of dissolved O2 drops for a given metabolic demand. This could mean that for a given PPO2 of inspired gas and a given metabolic demand, the PPO2 of plasma delivered to peripheral tissues might be higher. However, CNS tissue has first dibs on fresh blood. Therefore, it is not very likely that it has dropped much from equilibrium pressure at the blood-lung barrier.

Besides, if CNS oxtox is an issue at all, we're talking PPO2s that are very high into the oxygen dissociation curve, meaning that relatively little O2 is being liberated from RBCs for a given metabolic demand. Again, it seems that it would be difficult for hematocrit to have a significant influence on the process, at least from a PPO2 standpoint. I don't know what effect increased blood viscosity might have on oxtox.

Cameron