One of Cable’s professional interests is “altitude physiology of hypoxia” and training military and civilian aircraft personnel in hypoxia awareness.
“In an otherwise healthy person, hypoxia is not a noticeable effect at cabin altitudes of 4,000, 6,000, or even 8,000 feet, which is the absolute maximum,” he says. “But those with underlying medical problems, such as artery or lung disease, may have some impairment in their respiratory function.”
According to Gordon Cable, the cabin environment of an airplane can be taxing on the body and it is important for travelers to take care of their health.
“Anemia or low iron levels can mean that the blood cells aren’t carrying oxygen well enough, and symptoms of mild hypoxia can present themselves, making the person feel a little tired, short of breath with a headache or brain fog,” adds Cable. “Slight hypoxia also affects sleep architecture, affects the taste of food, and enhances the effects of alcohol. This is another good reason to limit alcohol, aside from the associated immobilisation and DVT risks.”
Airlines are aware of these risks, and according to Cable, Qantas has done a lot of research to mitigate the effects of prolonged confinement, immobilisation, lower air pressure and mild hypoxia (low oxygen levels in the tissues) in the cabin.
Plan for ULH success
“When I can afford it, I fly for business so I can stretch out and sleep to relieve jet lag. I’m adjusting my sleep patterns to my new time zone, taking my own pillow, noise-cancelling headphones, and drinking plenty of water,” says Cable. “I limit myself to a glass of champagne upon boarding and a glass of wine with dinner. An aisle seat means I don’t disturb anyone as I get up and pace a lot.”
Upon arrival, he trains and spends a lot of time in the bright sunlight to get into the new rhythm a little faster. If given the opportunity, he will choose to travel west, which will lengthen the day and make adjustment a little easier. Eastwards compresses time zones. The evidence for melatonin is conflicting, but he says there’s enough to suggest it works for circadian dysrhythmias.
A variety of bodily functions are tied into circadian rhythms, and because ULHs can occupy nearly an entire circadian cycle, airlines are constantly looking for better ways to manage the resulting disruptions and disorders. For example, Qantas draws on advice on a wide range of areas, from cabin lighting, heating and hydration to meal and menu timing.
“For those in economy or premium economy, ULH is more of a challenge. They should follow airline guidance on how to mitigate the strain,” Cable says.
And some aircraft are better configured for ultra-long range than others. “Boeing’s 787 Dreamliner is designed to fly at a lower cabin altitude, which is better tolerated, and has a higher cabin humidity, so it doesn’t have the same drying effect as other aircraft.
“It’s made of much lighter composite materials, which means it can be pressurized more, which has less of an impact on physiology. It’s also an all-electric aircraft, so the pressurization system is an entirely separate system. Normally cabins are pressurized with air coming from an engine.
“In general, these wide-body aircraft have lower passenger numbers on long-haul flights, as more business and premium offer more space and legroom.”
COVID-19 and ULH
Cable says concerns about COVID-19 are “a bit overdone.” So does Nader Abou-Seif, President-elect of the Australasian College of Aerospace Medicine. “But we still have to be careful when traveling because there is still potential for infections and new variants,” he says.
As there is no social distancing on the plane – people are still within 1.5 meters of each other in business class – he advocates wearing a mask regardless of the rules.
“Apart from discomfort, masks do not affect oxygenation and do not have a significant impact on blood gases,” says Abou-Seif. “While air filtration on airplanes is very effective and can certainly protect you from a person in the back of the plane, it doesn’t protect you from the person sitting next to you.
“I have had patients who have traveled with a baby. They wore masks, the baby didn’t. A passenger behind them coughed the entire flight and the baby contracted COVID-19. Of course the parents got it a few days later.”
dr Abou-Seif, clinical director of aerospace medicine at the Health Reserves Air Force (for the RAAF), says it’s not a good idea to wear the same soggy mask all the time.
“On most of these flights, the oxygen concentration in the lungs is probably two-thirds of what it should be at sea level. The cardiovascular and respiratory symptoms balance this out in healthy people,” says Dr. Abou soap.
“It’s easier to transmit an infection through a wet mask because you’re exhaling humidified air. Ideally, masks should be changed several times during the flight. Perhaps airline staff should offer them at certain intervals.”
In terms of hydration, he says if the mucous membranes get a little dry, the protection they provide can be less effective. Heavy smokers and travelers with underlying medical conditions that affect oxygen delivery, such as People with conditions such as heart disease or obstructive airways disease might have a more difficult time on long flights.
“For most of these flights, the oxygen concentration in the lungs is probably two-thirds of what it should be at sea level. The cardiovascular and respiratory symptoms compensate for this in healthy people,” he says. “Lack of sleep is also a problem. Being awake for 18 hours equates to a blood alcohol count of 0.05 in terms of coordination and judgment.”
While the negative effects of ULH travel may be more pronounced in older people, he says, older travelers may be able to compensate with strategies they’ve personally developed over years of flying.
The airlines also have strategies. For example, Qantas plans to introduce comfort zones for future ULH flights where everyone can move, stretch and drink.
Since comfort is also a function of mental state, it helps reduce anxiety on board by communicating well what to expect and how the flight is going.