By: David Gobel
On a recent trip to California, my goal was to document an aircraft’s actual interior cabin altitude, versus the altitude of that aircraft’s distance above the ground. Finding this altitude would tell me how much oxygen would be in the cabin, where lower altitudes would mean more available oxygen. To find out what the actual cabin pressure was, along with my own oxygenation level, I used a pulse oximeter and a small battery powered altimeter (used to record model rocket launches by measuring barometric pressure, i.e., the weight of the air). By comparison, if I had used an altimeter app, it would’ve measured altitude above sea by GPS, not by cabin altitude and thus oxygen availability.
The pulse oximeter used will typically rate me at 97% oxygenation. It also measures my pulse and I'm generally somewhere between 59 and 67 beats per minute (BPM) sitting quietly in a chair with my arm on an armrest (a normal range for adults is 60-100 beats). On the trip to and from California for the New Organ Alliance roadmapping effort, the cabin altitude was 6,500 feet heading west and above 8,000 feet heading east.
When not using an oxygen concentrator device, my oxygen level would drop to 90-92% on flights, and my pulse rate would approach 80 beats per minute. This appears to be a straightforward adaptation that the body engages when its oxygen level drops below its preferred set point, resulting in the more frequent delivery of less oxygen-saturated blood. It causes me to experience a feeling similar to claustrophobia (for clarity, I’m not claustrophobic and don’t have this experience in any other circumstance). I feel a near-panic desire to escape, along with feeling hot, clammy, and often nauseated. Before having the instrumentation to measure the possible reasons for this experience, I’ve always felt claustrophobic on flights, especially on red-eyes. What I’ve come to appreciate is that it’s not claustrophobia; it’s a response to a form of suffocation. It’s not dissimilar from being held underwater: of course I’d want to escape!
While having this low oxygen saturation, I would frequently yawn. Originally, I thought it was just sleepiness, but now with the measurements, it’s clear that my body was doing a lot of things to adapt to the situation, including trying to gulp more oxygen down. It’s likely that feelings of sleepiness were actually a reduction of oxygenation to my brain.
In addition to gasping for air by yawning, I would open up my chest and arch my back to enable as much breathing space as possible. This was made more difficult by being in a seat where your torso is compressed by your leg position and your shoulders are forced forward. Wearing a belt and constricting clothes further compounds the mechanical difficulty of respiration. The issue becomes more serious the older you get, the more obese you are, and with any existing respiratory conditions, such as allergies, asthma, or COPD (a chronic lung disease that restricts airflow).
In light of this oxygen deprivation, I’ve always had a really hard time with jet lag after flights. I can go two days and still have a fuzzy brain, which is terrible if you’re going to a scientific conference and trying to be friendly, happy, and on the ball.
Did an Oxygen Concentrator Make a Difference?
With use of an oxygen concentrator (see below), my pulse rate went down to my normal resting rate range of 68-72 BPM. I went up to 96-97% SpO2 (i.e., the amount of oxygen in the blood) at level 2 on the device, which also has a level 3 that would bring my oxygen saturation up to 98%, but I decided it would draw too much battery power.
All of the symptoms that I just described completely disappeared. I had no sense of claustrophobia, no sense of suffocation, no instinct to elongate my body and open my chest to get enough air. When arriving at my destination, I had no jet lag the following morning… in fact, I felt completely refreshed. As the day went on, I realized that even though I had just been on a cross-country flight, I felt perfectly normal. It was wonderful! At this stage of the trip, I attributed these feelings to some possible minor benefit from the oxygen, but mainly to a placebo effect.
And then it was time to come home. On the return trip, the cabin altitude was above 8,000 feet. I believe it was higher because the absolute altitude of the aircraft was about 4,000 feet higher going east than it was going west (probably to avoid headwinds or pick up tailwinds). On the way back, without an oxygen concentrator, my oxygen saturation had a median of 90%, ranging from 88-92%. Danielle, my consulting nurse, shared at the very beginning that I might be onto something important because when you're in a hospital, the standard of practice is to give oxygen to patients with an oxygen saturation of 94% or below, and that 90% or below is considered a clinically emergent state (see WHO’s SpO2 standards). We discovered that I was in a constant clinically compromised situation whenever flying.
My experience on the way back from NASA Ames to the DC area was similar. The oxygen concentrator was set so that I was reading a constant SpO2 of 96% on the pulse oximeter. Once back in DC, I felt completely rejuvenated, waking up feeling happy and completely aware, with no backache or grogginess. Maybe it wasn’t a placebo effect!
The Boeing 787 Dreamliner: “A Better Way to Fly”?
I just completed another trip, this time to Berlin for the Undoing Aging Conference, and I had similar results. This was a much longer journey, which included a flight from DC to Paris, with a layover of two hours, and another flight from Paris to Berlin. (In total, it was a 10-hour trip.) Once again, I used the oxygen concentrator, this time on a Boeing 787 Dreamliner for the transatlantic portion of the journey. I had hoped that the cabin altitude would be significantly lower and that I might not need the device, but that turned out to be completely wrong. The cabin altitude was 6,000 feet heading east towards Paris and I had exactly the same physical effects as when going to California.
Unfortunately, despite being on the Dreamliner, I needed the oxygen concentrator for both legs of the journey. Thanks to the use of the device, though, I had exactly the same positive outcome. I felt completely comfortable when using the concentrator, and without it, I felt like I was suffocating. Upon arrival, I was refreshed and in no distress, even though the new time zone was six hours earlier. Upon waking up the next morning, I was all smiles – ready to meet friends. At the Undoing Aging Conference, I was at least as competent as I ever get. But what about jet lag? None whatsoever. At least in my case (this n of 1), I’ve concluded jet lag really results from hypoxia – oxygen deficiency – over an extended period of time.
Additionally, I had hoped that the 787 would have higher cabin humidity. I can only report that during each leg of the trip, both heading east and west, there was a humidity of 16% in the cabin. This was a very disappointing result, as the Dreamliner had been advertised as having a higher humidity, or at least the potential for it (“Arrive feeling better: Better humidity” http://www.boeing.com/commercial/787/). It could be that this particular airline or flight crew decided that they did not want to either spend the extra money, time, or attention to ensure a hospitable environment for their passengers. Whatever the case may be, the cabin humidity was not any different than any other aircraft’s 16%.
Given these experiences, I’ve concluded that you should just pick whatever aircraft you happen to like. In my case, this is the A380 Airbus or the Boeing 747. Go for comfort. And if you can afford to, get an oxygen concentrator. If you feel short of breath or severely jet-lagged when flying, you can't afford not to have something like that device. They are now the size of a paperback book, weigh less than three pounds, and you can get batteries that last 5+ hours each. Most modern aircraft have A/C plugs as well, so you can operate it off of the cabin electrical feed.
The Risks of Flying: A Personal Report
One major problem that I frequently experience on flights, especially red-eyes, is syncope. Syncope is a lack of oxygen reaching the brain resulting in a loss of consciousness, often caused by changes in blood pressure. I thought it was simply a congenital issue that somehow had to do with the stress of flying and sleep deprivation by traveling during a time when I normally sleep. I doubt that now. I think what’s really happening is the result of a horrific environment that combines low oxygen, low humidity, and high temperatures, causing me to be hypoxic for an extended period of time. These cabins are an environment with almost no humidity. They have 10% lower humidity than the Sahara Desert!
Additionally, the cabin temperature on both California flights averaged above 85 degrees Fahrenheit. I don't know why...perhaps it's because it costs more to air condition the aircraft? Most people find such high temperatures to be uncomfortable. Personally, I prefer 68 to 72 degrees. How they permitted the cabin’s temperature to range from 85 to 89 degrees is beyond me. The FAA requires a temperature of 75 degrees as part of proper ventilation, but the lowest observed during the flights was 79 degrees F. In a cabin where the temperature is as high as 89 degrees and you're wearing business clothes, you're going to get overheated. If you're hypoxic and drier than the desert, it's no wonder that you get nauseated and pass out. Who knows what they allow on a red-eye flight! Frankly, at this point I'm not willing to try a red-eye, but maybe I will down the road now that at least I won’t be starving for oxygen.
In addition to the unpleasantness of my symptoms when flying without oxygen supplementation, the effects on my body put me at a higher risk for secondary, life-threatening events. The higher pulse rate compensating for the low oxygen puts a greater strain on my heart, making my risk of an arrhythmia or heart attack higher. In fact, the risk of myocardial infarction would be even higher because the lower blood oxygen concentration means that my heart muscle is also not receiving the oxygen it needs, and the dehydration that often accompanies flying thickens the blood. The low oxygen saturation of my blood combined with my drowsiness and anxiety leads me to believe that I was not getting enough oxygen to my brain. That certainly presents a risk for syncope (more on this later), but also could increase my risk of ischemic cerebral hypoxia, which, if sustained, can cause permanent brain damage. At the same time, the lack of oxygen in my body puts an extra strain on all of my organs. If someone had an underlying liver or kidney condition, one would expect organ failure to be a much higher risk.
At the beginning of this journey, we were looking at oxygenation as a phenomenon that could lead to severe jet lag, syncope, and hypoxia misdiagnosed as claustrophobia. Originally, I saw that the difference between my SpO2 of 97% and 92% was only 5%, so what was the big deal? 5% is so small. But if you do the math differently and say that anything <90% is a clinical emergency, then the real range is 90%-100%, or a 10% acceptable range. So of the 10%, 5% is half what you need to survive. That’s a very big deal. And I am here to tell you that it's very real and very important.
That leads me to the next question: Instead of falling in that 10% safety range, what if you were chronically down 1% all the time? Could that add to chronic low-grade depression, or other problems? Could it lead to getting sick more often? And do we actually know how to determine what the optimal oxygenation level is for an individual over time?
Flying with an Oxygen Concentrator: 13 Hours Later
Before flying with a personal oxygen concentrator, an immense amount of work is involved to ensure you’ll be able to use it. We did the trial (and the error), so that hopefully you will have a much easier time. The first step is to get a written prescription from your physician specifying that you need, for example, “supplemental O2, 2 LPM via nasal cannula as needed for shortness of breath.” You will need this prescription to obtain the oxygen concentrator, and you will need to present it to your flight check-in and at the gate. It would be very wise to have a scanned electronic copy.
The next step is choosing your concentrator. We highly recommend the Inogen line of oxygen concentrators. The unit we purchased was the Inogen One G4, which is the newest, quietest, smallest, lightest unit on the market. However, purchasing the latest and greatest came with a little setback. Although the unit itself meets FAA regulations, the FAA posts a list of “FAA Approved” units. The last list was posted in February 2014, so it is not frequently updated, so the Inogen One G4 is not listed.
In addition, each airline has the freedom to allow or deny a passenger’s use of their oxygen concentrator as they see fit. A passenger will need to work with each airline to ensure that they are meeting their requirements. For example, Virgin America simply required the unit to have a sticker on it stating that it met FAA regulations and a physician’s prescription. Air France did not permit use of the unit, because they require their own testing of each unit and post their own list of acceptable ones. United required an additional form to be signed by the physician specifying when the unit would be used. While they also require the passenger to have 1.5x the duration of the flight in battery life, this was waived because I didn’t need to operate the unit during takeoff or landing, and would only use it as needed (releasing the airline from any liability of you being unable to both use your oxygen concentrator and charge it).
Before flying, be sure to call the airline’s Special Travel Needs contact number to register the unit for your flight reservation and to ensure that any additional hoops are jumped through. As always, it’s a good idea to call again shortly before the trip to confirm.
Once you arrive at the airport, show your prescription and concentrator at the check-in desk, and reconfirm that you are all set. You will need to keep the unit out for security, and check in again at the gate with your unit and paperwork.
All of that may sound like a lot of hassle, and it is. If you experience jet lag, though, or any of the other symptoms from air travel discussed here, I hope you’ll consider pursuing your own experiments and seeing if you realize similar stunning results. Feeling wonderful after flying and mitigating any health risks makes any hassle entirely worth it.
N of One Disclaimer: This article outlines individual experiments with recommendations for your own personal trials. The results, while individually significant, don’t constitute a statistically significant data set. Your mileage may vary.