High-Altitude Pilots at Increased Risk...
08-30-2013, 08:20 AM
#1
Gets Weekends Off
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Joined APC: Aug 2012
Posts: 1,026
High-Altitude Pilots at Increased Risk...
This article requires an account. I posted it here as it is a rather interesting article concerning U-2 drivers.
High-Altitude Pilots at Increased Risk for Brain Lesions
Megan Brooks
Aug 22, 2013
High-flying U-2 pilots in the United States Air Force (USAF) have an abnormally high number and volume of white matter hyperintensity (WMH) brain lesions on magnetic resonance imaging (MRI), a study suggests.
"These are novel observations in the U-2 population," neurologist Stephen McGuire, MD, from the University of Texas in San Antonio and the USAF School of Aerospace Medicine, told Medscape Medical News.
"We have been unable to identify any clinical deficits in any of the U-2 pilots studied, and all of the U-2 pilots that were part of this study are still performing the extremely complex tasks associated with flying the U-2 plane," he noted. "What we do not know is the long-term implication of these findings, nor what the threshold might be for inciting clinical symptoms," Dr. McGuire added.
The study was published in the August 20 issue of Neurology.
More Missions Since 9-11
The U-2 is a high-altitude reconnaissance aircraft that maintains a cabin altitude of approximately 9000 m while operating above 21,000 m, the investigators note in their report. Decompression sickness (DCS), including central nervous system neurologic DCS (NDCS), is a known occupational risk from exposure to low ambient pressure (hypobaria) in high-altitude pilots.
The risk for DCS among U-2 pilots has tripled since 2006, probably as a result of more frequent and longer periods of exposure for pilots. Dr. McGuire said the current study was "precipitated by the increased incidence of clinical NDCS" observed in U-2 pilots in association with the increase in intelligence, surveillance, and reconnaissance operations conducted since 2001.
He and his colleagues obtained MRI brain scans of 102 USAF U-2 pilots and 91 non-pilots matched for education, health factors, and age. All were between 26 and 50 years old.
They found that the U-2 pilots had nearly 4 times the volume (394%; P = .004) and 3 times the number (295%; P < .001) of WMH as non-pilots. The results were the same whether or not the pilots had a history of symptoms of DCS.
"Currently, the consensus opinion of the scientific community is these lesions are markers of an underlying disease process," Sean Jersey, MD, from the David Grant USAF Medical Center, Travis AFB, California, who was not involved in the study, told Medscape Medical News.
"A normal, healthy, young adult should not have very many, if any, detectable brain lesions. In the case of our U-2 pilots or divers, they are probably the result of an occupational exposure which was previously unrecognized," he said. Dr. Jersey emphasized that more research is needed "before we can say for certain that these lesions are dangerous."
Dr. McGuire and colleagues also found that the brain lesions in the nonpilots were mainly located in the frontal white matter, whereas in the U-2 pilots, they were more uniformly distributed throughout the brain and did not increase with age. This suggests, the authors say, that hypobaric exposure during high-altitude flights produces white matter damage different from that occurring in normal aging. "Both findings suggest injury produced by microemboli entering cerebral circulation at random," they note.
The researchers hypothesize WMH in U-2 pilots stems from "interaction between microemboli and cerebral tissue, leading to thrombosis, coagulation, inflammation and/or activation of innate immune response." More study is needed to clarify the pathologic mechanisms.
"We've suspected for some time that these pilots are having subclinical microbubble or microthrombi disease in the brain," Claude Piantadosi, MD, director of the Duke Center for Hyperbaric Medicine and Environmental Physiology, Durham, North Carolina, told Medscape Medical News. Dr. Piantadosi was not involved in the study.
An important DCS countermeasure for high-altitude pilots is prebreathing 100% oxygen before flying to denitrogenate body fluids and tissues. Dr. Piantadosi explained that when the U-2 program got started back in the 1950s and 1960s, pilots had a "very long oxygen prebreathe of 4 hours, and there wasn't as much [DCS] as seen recently."
"Two things have changed since 9-11," he said. The prebreathe has been shortened to 2 hours, "so the pilot has more time at altitude and more mission time, and the pilots fly more frequently: Instead of every couple of weeks[, they] may be flying twice a week."
In terms of the clinical significance of these lesions for long-term neurodegeneration and, in particular, the risk for Alzheimer's disease, Dr. Piantadosi said, "we don't have those answers yet, and this study doesn't address that."
USAF Being Proactive
Dr. McGuire said the USAF has been "very proactive in (1) addressing factors that will lessen the risk and (2) instituting a long-term monitoring program to better understand the long-term implications."
Edward T. Sholtis, deputy director of public affairs, Headquarters Air Combat Command at Langley AFB, Virginia, told Medscape Medical News the USAF has completed the evaluation of U-2 pilots, and ongoing occupational MRI monitoring by the Aeromedical Consult Service is now being implemented.
"Each pilot will receive a baseline MRI, a follow-on MRI every 3 years, and a final MRI when they leave the U-2 program by cross-training, separating, retiring, etc. These evaluations will provide medical documentation of any significant changes and allow long-term monitoring," he said.
"Current AF policy is no pilot will be disqualified based on WMH identified by MRIs," he added.
Sholtis also said the USAF is in the process of restricting exposure for the U-2 pilots via several measures: "flight operations guidance is under review to potentially increase down time between high flights longer than 9 hours, as well as limiting the length of deployments. Additionally, the Cockpit Altitude Reduction Effort (CARE) is a new program that will reduce the altitude U-2 pilots are exposed to during operational missions."
The study was supported by the USAF Surgeon General. The authors, Dr. Jersey, and Dr. Piantadosi have disclosed no relevant financial relationships.
High-Altitude Pilots at Increased Risk for Brain Lesions
Megan Brooks
Aug 22, 2013
High-flying U-2 pilots in the United States Air Force (USAF) have an abnormally high number and volume of white matter hyperintensity (WMH) brain lesions on magnetic resonance imaging (MRI), a study suggests.
"These are novel observations in the U-2 population," neurologist Stephen McGuire, MD, from the University of Texas in San Antonio and the USAF School of Aerospace Medicine, told Medscape Medical News.
"We have been unable to identify any clinical deficits in any of the U-2 pilots studied, and all of the U-2 pilots that were part of this study are still performing the extremely complex tasks associated with flying the U-2 plane," he noted. "What we do not know is the long-term implication of these findings, nor what the threshold might be for inciting clinical symptoms," Dr. McGuire added.
The study was published in the August 20 issue of Neurology.
More Missions Since 9-11
The U-2 is a high-altitude reconnaissance aircraft that maintains a cabin altitude of approximately 9000 m while operating above 21,000 m, the investigators note in their report. Decompression sickness (DCS), including central nervous system neurologic DCS (NDCS), is a known occupational risk from exposure to low ambient pressure (hypobaria) in high-altitude pilots.
The risk for DCS among U-2 pilots has tripled since 2006, probably as a result of more frequent and longer periods of exposure for pilots. Dr. McGuire said the current study was "precipitated by the increased incidence of clinical NDCS" observed in U-2 pilots in association with the increase in intelligence, surveillance, and reconnaissance operations conducted since 2001.
He and his colleagues obtained MRI brain scans of 102 USAF U-2 pilots and 91 non-pilots matched for education, health factors, and age. All were between 26 and 50 years old.
They found that the U-2 pilots had nearly 4 times the volume (394%; P = .004) and 3 times the number (295%; P < .001) of WMH as non-pilots. The results were the same whether or not the pilots had a history of symptoms of DCS.
"Currently, the consensus opinion of the scientific community is these lesions are markers of an underlying disease process," Sean Jersey, MD, from the David Grant USAF Medical Center, Travis AFB, California, who was not involved in the study, told Medscape Medical News.
"A normal, healthy, young adult should not have very many, if any, detectable brain lesions. In the case of our U-2 pilots or divers, they are probably the result of an occupational exposure which was previously unrecognized," he said. Dr. Jersey emphasized that more research is needed "before we can say for certain that these lesions are dangerous."
Dr. McGuire and colleagues also found that the brain lesions in the nonpilots were mainly located in the frontal white matter, whereas in the U-2 pilots, they were more uniformly distributed throughout the brain and did not increase with age. This suggests, the authors say, that hypobaric exposure during high-altitude flights produces white matter damage different from that occurring in normal aging. "Both findings suggest injury produced by microemboli entering cerebral circulation at random," they note.
The researchers hypothesize WMH in U-2 pilots stems from "interaction between microemboli and cerebral tissue, leading to thrombosis, coagulation, inflammation and/or activation of innate immune response." More study is needed to clarify the pathologic mechanisms.
"We've suspected for some time that these pilots are having subclinical microbubble or microthrombi disease in the brain," Claude Piantadosi, MD, director of the Duke Center for Hyperbaric Medicine and Environmental Physiology, Durham, North Carolina, told Medscape Medical News. Dr. Piantadosi was not involved in the study.
An important DCS countermeasure for high-altitude pilots is prebreathing 100% oxygen before flying to denitrogenate body fluids and tissues. Dr. Piantadosi explained that when the U-2 program got started back in the 1950s and 1960s, pilots had a "very long oxygen prebreathe of 4 hours, and there wasn't as much [DCS] as seen recently."
"Two things have changed since 9-11," he said. The prebreathe has been shortened to 2 hours, "so the pilot has more time at altitude and more mission time, and the pilots fly more frequently: Instead of every couple of weeks[, they] may be flying twice a week."
In terms of the clinical significance of these lesions for long-term neurodegeneration and, in particular, the risk for Alzheimer's disease, Dr. Piantadosi said, "we don't have those answers yet, and this study doesn't address that."
USAF Being Proactive
Dr. McGuire said the USAF has been "very proactive in (1) addressing factors that will lessen the risk and (2) instituting a long-term monitoring program to better understand the long-term implications."
Edward T. Sholtis, deputy director of public affairs, Headquarters Air Combat Command at Langley AFB, Virginia, told Medscape Medical News the USAF has completed the evaluation of U-2 pilots, and ongoing occupational MRI monitoring by the Aeromedical Consult Service is now being implemented.
"Each pilot will receive a baseline MRI, a follow-on MRI every 3 years, and a final MRI when they leave the U-2 program by cross-training, separating, retiring, etc. These evaluations will provide medical documentation of any significant changes and allow long-term monitoring," he said.
"Current AF policy is no pilot will be disqualified based on WMH identified by MRIs," he added.
Sholtis also said the USAF is in the process of restricting exposure for the U-2 pilots via several measures: "flight operations guidance is under review to potentially increase down time between high flights longer than 9 hours, as well as limiting the length of deployments. Additionally, the Cockpit Altitude Reduction Effort (CARE) is a new program that will reduce the altitude U-2 pilots are exposed to during operational missions."
The study was supported by the USAF Surgeon General. The authors, Dr. Jersey, and Dr. Piantadosi have disclosed no relevant financial relationships.
08-30-2013, 10:02 AM
#3
Gets Weekends Off
Joined APC: Nov 2006
Position: Body at sea level; heart at 70,000+
Posts: 1,349
A Personal Story that may help others.
In 1968 I experienced a decompression sickness "severe headache" during the last hour of an eight hour pressure suit flight. The pain was so distracting that I went below a minimum altitude restriction and was immediately corrected by my systems operator.
Well aware of the consequences of reporting the incident, and not wanting to be grounded, I landed, went home and took two Excedrin. Other then associated with a cold or flu, I had never experienced a headache before. I rationalized it must have been a single migraine event.
Eight years later (1976) I began to have frequent headaches and purchased lots of Excedrin. Again I rationalized they resulted because of the tension levels of my job (USAFA Cadet Wing DO - 0036). The frequency and over the counter treatment continued until 2004 when I finally sought medical opinion and "stronger medication."
The diagnosis was "Cluster Headaches." A large number of physicians don't even know what they are. Every severe headache to them is a migraine. Here is a "simplified description from Wikipedia:
Cluster headache is a condition that involves, as its most prominent feature, an immense degree of pain that occurs always on only one side of the head. (Unilateral) [1][2] Cluster Headaches belong to a group of primary headache conditions, called Trigeminal Autonomic Cephalalgias or (TACs). Some doctors and scientists have described the pain resulting from cluster headaches as the most intense pain a human can endure — worse than giving birth, burns or broken bones. Cluster headaches often occur periodically; spontaneous remissions interrupt active periods of pain, though about 10-15% of chronic cluster headache sufferers never remit.[3] Some people affected with cluster headache have committed suicide, leading to the nickname "suicide headaches."[4] The cause of the condition is not yet known.
I added the underlining. The worse cluster I ever experienced lasted over four months - a headache every day. Onset is less than ten minutes and treatment is with 'Sumatriptan . " Until it works, life is miserable.
The VA granted me 10% disability based on the DCI pressure suit experience. There is no monetary gain as the USAF takes an equal amount out of my retirement pay. Law precludes collecting both unless the disability is 50% or higher.
The lesson learned from my experience and recently released U-2 documents is that pilots are RELUCTANT to report DCI events and these events can have serious consequences on your health for the rest of your life.
Needless to say I cannot pass a flight physical.
In 1968 I experienced a decompression sickness "severe headache" during the last hour of an eight hour pressure suit flight. The pain was so distracting that I went below a minimum altitude restriction and was immediately corrected by my systems operator.
Well aware of the consequences of reporting the incident, and not wanting to be grounded, I landed, went home and took two Excedrin. Other then associated with a cold or flu, I had never experienced a headache before. I rationalized it must have been a single migraine event.
Eight years later (1976) I began to have frequent headaches and purchased lots of Excedrin. Again I rationalized they resulted because of the tension levels of my job (USAFA Cadet Wing DO - 0036). The frequency and over the counter treatment continued until 2004 when I finally sought medical opinion and "stronger medication."
The diagnosis was "Cluster Headaches." A large number of physicians don't even know what they are. Every severe headache to them is a migraine. Here is a "simplified description from Wikipedia:
Cluster headache is a condition that involves, as its most prominent feature, an immense degree of pain that occurs always on only one side of the head. (Unilateral) [1][2] Cluster Headaches belong to a group of primary headache conditions, called Trigeminal Autonomic Cephalalgias or (TACs). Some doctors and scientists have described the pain resulting from cluster headaches as the most intense pain a human can endure — worse than giving birth, burns or broken bones. Cluster headaches often occur periodically; spontaneous remissions interrupt active periods of pain, though about 10-15% of chronic cluster headache sufferers never remit.[3] Some people affected with cluster headache have committed suicide, leading to the nickname "suicide headaches."[4] The cause of the condition is not yet known.
I added the underlining. The worse cluster I ever experienced lasted over four months - a headache every day. Onset is less than ten minutes and treatment is with 'Sumatriptan . " Until it works, life is miserable.
The VA granted me 10% disability based on the DCI pressure suit experience. There is no monetary gain as the USAF takes an equal amount out of my retirement pay. Law precludes collecting both unless the disability is 50% or higher.
The lesson learned from my experience and recently released U-2 documents is that pilots are RELUCTANT to report DCI events and these events can have serious consequences on your health for the rest of your life.
Needless to say I cannot pass a flight physical.
08-30-2013, 08:18 PM
#4
Get me outta here...
Joined APC: Oct 2008
Position: Boeing right seat
Posts: 1,541
I was one of the pilots tested, and I went through two full MRI's, in two different machines. I hate MRI's.
Note that all of the single-seat AF U-2s have been modified so the cabin pressure at 70,000' is 14,500', instead of 29,000'. We expect DCS to pretty much go away.
Note that all of the single-seat AF U-2s have been modified so the cabin pressure at 70,000' is 14,500', instead of 29,000'. We expect DCS to pretty much go away.
08-31-2013, 09:56 AM
#6
Moderate Moderator
Joined APC: Mar 2008
Position: Curator at Static Display
Posts: 5,681
Ftrooper:
Sorry to hear about your condition (with respect to flying), but glad there is something that can give you relief.
Do you think the lesions in the study could be due to intensity of radiation, instead of their theory of micro bubbles? High altitude for long exposure means lots of radiation. I'm guessing 65-70,000 ft is 2 to 4 times the level of 35,000 ft.
My squadron in Germany has an incidence of brain cancer that is 13 times the statistical norm. My hunch is the local groundwater comes from limestone wells.....and limestone frequently also has radon.
Sorry to hear about your condition (with respect to flying), but glad there is something that can give you relief.
Do you think the lesions in the study could be due to intensity of radiation, instead of their theory of micro bubbles? High altitude for long exposure means lots of radiation. I'm guessing 65-70,000 ft is 2 to 4 times the level of 35,000 ft.
My squadron in Germany has an incidence of brain cancer that is 13 times the statistical norm. My hunch is the local groundwater comes from limestone wells.....and limestone frequently also has radon.
08-31-2013, 12:18 PM
#7
Gets Weekends Off
Joined APC: Nov 2006
Position: Body at sea level; heart at 70,000+
Posts: 1,349
Originally Posted by UAL T38 Phlyer
Ftrooper: . . . Do you think the lesions in the study could be due to intensity of radiation, instead of their theory of micro bubbles? High altitude for long exposure means lots of radiation. I'm guessing 65-70,000 ft is 2 to 4 times the level of 35,000 ft.
http://www.u2sr71patches.co.uk/rb57f.htm
" Most of the -F models operated by the US Air Force was assigned as weather reconnaissance aircraft and used in part to measure radiation levels after above ground nuclear weapons tests conducted by other countries."
The patch we wore:
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