The Environics, Inc. Post
Last week, in the YouTube program "Scrubbing In" presented by Navy Medicine, focused on training Naval and Marines for the feeling of hypoxia. In this week's show, the hosts are at Navy Medicine Aviation Survival Training Center in Patuxent River, Md, and the training application of the Environics Reduced Oxygen Breathing Device (ROBD2) is featured.
LCDR Corey Littel, the Director of the Aviation Survival Training Center, discusses what hypoxia is and how the pilots are trained. The Leutenant Commander discusses the use of hypobaric chambers for hypoxia awarenewss training. He explains this method is "slightly outdated." We then are shown training lab containing a number of ROBD2 systems, as well as the use of the "much more modern means of delivering a mask on version" of hypoxia training.
Produced by U.S. Navy Bureau of Medicine and Surgery Visual Information Directorate, published April 10, 2013
A few weeks back, I shared some information on the flight restrictions enacted due to concerns of hypoxia and hypoxia symptoms in pilots of the F-22 Raptor. Yesterday, it was reported that a potential cause of has been identified.
The flight restrictions, which limit flights within 30 minutes of a landing field, are still in place. According to Col. Kevin Robbins, a commander of the First Fighter Wing at Langley Air Force Base, 11 incidents of hypoxia have been reported in the last 10 months.
There have been and still are many speculated reasons for the hypoxia (which we review here and here). The latest release suggests that it is not the aircraft itself, but a piece of equipment worn by the pilots, a vest, that is to blame.
Due to the 9Gs the F-22 pilots may endure, an inflatable vest is worn. The vest provides counter-pressure during rapid decompression. While protecting the lungs, it also has the effect of restricting breathing, potentially being a hazard in terms of hypoxia.
The Environics Reduced Oxygen Breathing Device (ROBD2) is used in the training of pilots on hypoxia.
To view the full story, as aired on CBS News, please see below. You can see the ROBD2 used in correlation with the training simulator at about 45 seconds.
As a followup to my last post about the restrictions on F22 flights, Stars and Stripes published an interesting article which discusses some of the possible causes. One suggested cause is the oxygen system. The on-board oxygen generation system, or OBOGS, in the Raptors does not use liquid oxygen like the F16. Instead, air is drawn in through the engine and then filtered to increase the oxygen in the pilots' breathing air.
While the OBOGS is one possibility, Air Force investigators are considering other possiblilities, such as contimination as well. Several suggested contaminates are discussed, including the components that are used to create the F22 skin. The skin is created in a unique way to help the fighter evade radars.
In the news recently, there have been a number of stories regarding the F-22 Raptor and the concerns of pilots and others regarding symptoms of hypoxia in flight. Yesterday, Defense Secretary Leon E. Panetta ordered the Air Force Tuesday to limit all F-22 flights to distances that would allow pilot to make an emergency landing at any given time. In addition, the time line for addition of backup oxygen to the aircraft has been moved up. The Secretary requested monthly updates on the efforts to local the root cause of the oxygen deficiency in the cockpit.
The symptoms of hypoxia vary between individuals. The initial symptoms can include a general dulling of the senses, clumsiness or drowsiness. Some compare the feeling to being slightly intoxicated.
Without suplemental oxygen or flying to lower altitudes, the symptoms then worsen. Pilots may suffer from any combination of the following symptoms:
tingling in the skin
changes in vision
bluish tint to the lips.
Due to the effect on the brain, however, the pilot may be completely unaware that they are having any problems. The Reduced Oxygen Breathing Device is used to train pilots on the early symptoms of hypoxia in a simulated environment so that they may take preventative actions prior to becoming incapacitated.
Please click for more information on the symptoms of hypoxia, how the body becomes hypoxic at high altitude, and on how the Environics Reduced Oxygen Breathing Device is used to train pilots on the symptoms of hypoxia.
Every year, we ask our customers for their feedback throughout the year as well as on our annual Continuous Improvement Survey. We take this input very seriously, discussing the thoughts and suggestions and, when possible, implementing the requests that are made. One recurring suggestion was the availability of a Service Agreement for Recalibration of our systems. (You can learn more about our Calibration Services here.)
After many internal discussions, we are proud to announce the availability of Service Agreements on both new and existing systems. By having a Service Agreement with us, you will save both time and money. We are happy to help customize your agreement to fit your needs.
The benefits of signing a Service Agreement are:
You will lock in the current recalibration cost for the length of your agreement.
Your system will be given priority status when it arrives for recalibration. This means less downtime for you!
Your will receive a 5% discount on your recalibration cost by prepaying a One-Year Agreement or by signing a Two to Five Year Service Agreement (prepayment not required). This discount is on top of the savings you receive by locking in the current recalibration rates.
To learn more or to request a Service Agreement for an existing system, please contact us at (860) 872-1111 or complete an online request.
Over the past year, I have written several times about the effects of hypoxia, including a video, which showed not only how hypoxia may present itself, but how the hypoxic person may be oblivious to the effects. I also shared information regarding the use of the Reduced Oxygen Breathing Device (ROBD2), and how this system is used in military training to allow pilots to better prepare and understand the symptoms of hypoxia. You can read more here and here.
Today, I wanted to share an interesting study from the Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences in Bethesda, Maryland, and the Aviation Survival Training Center, Naval Survival Training Institute, Naval Operational Medicine Institute in Washington. The researchers were attempting to determine how effectively the ROBD (the earlier version of the ROBD2) reflected the reported symptoms of hypoxia when compared to in-flight occurrences.
The researchers began by surveying 566 aviators with a 20 question, anonymous survey about their flight experiences with hypoxia PRIOR to ROBD training. The survey included basic demographic questions followed by questions regarding in-flight hypoxia symptoms they may have experienced. For those who responded that they had experienced hypoxic symptoms in flight, additional questions were asked regarding which symptoms they had experienced.
A second group of 156 pilots were surveyed, also anonymously, following ROBD training at a simulated altitude of 25,000 ft (following the Navy's standard training protocols). Again, the survey included demographic questions as well as questions regarding any symptoms of hypoxia they may have experienced during the training.
Once the data was collected, the results were analyzed using a variety of means (including Chi-square analysis (alpha=0.05), Fischer’s exact test (alpha=0.05), and incident
risk ratios). I won't review all of the data and analysis, but some of the key findings are reviewed below.
For those surveyed regarding in-flight symptoms:
20% reported hypoxia symptoms at an average altitude of just over 25,000 ft
Of those who had experienced in-flight symptoms, over half (57%) were not wearing an oxygen mask when the symptoms started and only 21% reported the experience in naval aviation hazard reports (HAZREPs).
The most common symptoms reported were tingling, difficulty concentrating and dizziness.
When comparing the results of the two surveys, the researchers found:
5 of the 16 symptoms listed on the surveys had statistically significant differences in the reported levels (tingling, difficulty concentrating, air hunger, blurred vision, and lights dimming.
For the other 11 of the 16 symptoms, there was NO significant difference between the frequency reported during in-flight experiences and ROBD2 training experiences.
The authors conclude that some of the symptoms differences found may be minimized with some of the updates in the ROBD2, and that additional customization may reduce these still further. Regardless, they state, "Ultimately, the authors recommend the continued use
of ROBD as an operationally focused and seemingly valid training tool," recommending it be used as part of a total program which includes instruction on both the similarities and potential differences between training symptoms and in-flight symptoms.
To read the full article, click here (there is a fee for download. AsMA members have free access).
In past posts (here, here and here), we've looked at the effect that hypoxia has on both military and civilian pilots flying at altitude. We also talked about the ways these pilots can be trained to recognize the signs of hypoxia early so they can react accordingly. Today, I wanted to step back and look at what causes hypoxia at altitude.
Environment at Altitude - Pressure
It is better to have your head in the clouds, and know where you are... than to breathe the clearer atmosphere below them, and think that you are in paradise. - Thoreau
Earth's atmosphere encompasses us with a gaseous envelope which rotates with the planet. Commonly, it is said that as you go higher in altitude about the ground, the air is "thin." This implies that there is a change in the composition of the air at altitude, which is not true. The total blend of gaseous components (predominately nitrogen (78%) and oxygen (21%) remains the same. What changes is the number of oxygen molecules per unit volume of air. Why? Because this is directly affected by pressure, which decreases as you go up in altitude. So, while the same percent of oxygen is in the air, the actual value is highly lower. A simple analogy would be that on the ground 21% oxygen is like 21 red marbles in a cup of blue marbles while at altitude, it is 21 red marbles in a bathtub full of blue marbles.
In addition to the change in pressure, the lower temperature at altitude affects the gases. This effect is not as substantial as that of pressure, but is still important. The heat comes primarily from the heat of the Earth, not the sun. So, the higher up, the cooler it becomes (approximately 2°C for every additional thousand feet of altitude).
Science 101 - Gas Laws
A quick refresher of the main gas laws that will come into play.
Dalton's Law - With constant temperature and pressure, the sum of the component gas pressures in a gas mixture will be equal to the total pressure of the mixture. So, for our situation, since the percentage of oxygen in the atmosphere is 21%, we can calculate the partial pressure of oxygen at any altitude. This is key since the partial pressure of oxygen available plays a critical role in determining the onset and severity of hypoxia.
Graham's Law - A gas at high pressure exerts a force on a region of lower pressure. This can be simplified if you think of it as an attempt to reach an equilibrium. If there is a permeable or semi-permeable membrane between two gases, and gas will move from the area of higher pressure to the area of lower pressure until equilibrium is reached. All gases act this way and they do so independently in part of a gas mixture. It's possible (and actually probably) to gases in a mixture moving in opposite directions across the same membrane. In terms of the human body, this occurs to transfer oxygen in cells and tissues.
The Human Body at Altitude
What does all of that mean in terms of an actual human in a plane at altitude? Good question!
At sea level, the air that we breathe is at a pressure of 760 mm Hg, with the partial pressure of oxygen being 160 mm Hg (think of Dalton's Law, 21% of 760 mm Hg). By the time the oxygen gets to the lung, we are down to about 14% (106.4 mm Hg) oxygen and an increase concentration of carbon dioxide at a pressure of 41.8 mm Hg. After sending the oxygen rich blood out to the rest of the body, the returning blood carries oxygen at only 40 mm Hg. As we determined from Graham's Law, the oxygen will move from the higher pressure in the lung into the blood, where it is low while the carbon dioxide will move in the opposite direction. This cycle (breath in oxygen rich air, oxygen in the lung moves into the oxygen depleted blood, carbon dioxide moves out of blood, breathe out carbon dioxide rich air) continues with each breath.
And at altitude?
Well, at sea level, the pressure differences that allow the transfer of oxygen are sufficient to cause the blood leaving the lungs to be almost totally (97%) saturated with oxygen. Move up to the top of Pike's Peak (about 14,500 feet) the oxygen saturation drops with the pressure to about 80% and symptoms of altitude sickness appear with any prolonged exposure. At 25,000 feet, the partial pressure of oxygen in the lung is 14% of 281.8 mm Hg or 39.5 mm Hg. This is LOWER than the pressure of oxygen in the blood returning to the lung. The transfer of oxygen is therefore interrupted, and a body in this circumstance will quickly lose consciousness. In between these two altitudes, symptoms from mild vision issues to serious disorientation are seen.
Click here to learn more about the effects of hypoxia and to watch a training video which demonstrates the symptoms of hypoxia.
Several months ago, I shared some information about the effects of hypoxia. I included a video, which showed not only how hypoxia may present itself, but how the hypoxic person may be oblivious to the effects. I also shared information regarding the Reduced Oxygen Breathing Device (ROBD2), a system manufactured solely by Environics under a Navy patent, and how this system is used in military training to allow practical training with lower expense. You can review these articles here and here.
To refresh your memory, hypoxia is a condition brought on due to inadequate oxygen and the symptoms can include any combination of the following symptoms: dizziness, tingling in the skin, headache, racing heart, changes in vision, and bluish tint to the lips. Military personnel are not the only people who experience hypoxic conditions though. In a study presented at the 2010 ASMA conference, researchers examined the use of the ROBD2 on a sample group of 36 civilians ("The Use of the Reduced Oxygen Breathing Device (ROBD) in a General Civilian Sample, Pulse Oximetry Means and Ranges," a presentation of research by Leonard A. Temme, Ph.D. and David L. Still, O.D., Ph.D. of U. S. Army Aeromedical Research Laboratory, Dennis Reeves, Ph.D., and Rebecca Browning, B.S. of Clinvest, Banyan Group, Inc.; full presentation available here).
Civilians who are most likely to experience hypoxia include those flying in private or commercial aircraft, undergoing aviation training, using hypoxia training strategies for athletic improvements and Travel/tourism.
The researchers found that:
• Pulse rate increased with ROBD simulated altitude
• % blood oxygen between-subject variability increases with ROBD
• Pulse rate between-subject variability unaffected by ROBD simulated
• BMI positively correlated with pulse rate @ all altitudes
• BMI inversely correlated with %O2 at 8,000 and 12,000 ft
In summary, the study found that the ROBD2 could successfully be used for civilian training and "does what it says it does." The only alteration made was to replace the military style respirator with a non-military equivalent.
Donna Murdoch PhD, CAsP; CDR Matt Hebert, CDR Joe Essex
Our team has been having a terrific time at the Aerospace Medical Assoc. Annual Meeting in Anchorage, Alaska this week. We've had the chance to speak with participants from the US and overseas, and we have learned a great deal. Yesterday, there was a talk about the effects of hypoxia on pilots and the use of the Environics ROBD2 in hypoxia training. We are thrilled to play a small role in making training equipment that truly can help save lives.
Thanks to all of you who stopped by!!
Terry Dunn, President of Environics, Donna Murdoch PhD, CAsP, Leonard Temme PhD
If you weren't able to attend and want to learn more, check out the ROBD2 page which contains details on our system as well as a video about its use by the US Navy. Also, check out this blog post to see an eye opening view how hypoxia effects brain function.