Did you know that airplanes have lower oxygen levels which is why we sometimes feel lethargic when we fly?
No, I didn’t either and this is just one of the many things.I learned on my recent adventure to our award-winning Respiratory Investigations department at Hinchingbrooke. Fit to fly testing is just one of the many clinics the team run throughout the week. Sadly I arrive at the end of the clinic, but Chief Respiratory Physiologist Melanie Bryce gives me a whistle-stop tour through the process.
“The air we breathe is made up of 21% oxygen but as you get higher the amount of oxygen in the air decreases,” says Melanie. “As planes fly above 8,000ft the oxygen drops to 15%, which is why we often feel tired and headachey during a flight. For people with lung conditions, this can cause them to become unwell, so we run a fit to fly test to see if it is safe for patients to fly or whether they will need extra oxygen during their journey.”
Melanie and her team recreate the oxygen levels on a plane by giving patients a mask to breathe through for 20 minutes at 15% oxygen, and measures the body’s response e.g. whether or not they become hypoxic.
I am learning that the role of a clinical physiologist is a varied one as I am invited to shadow Gemma Wells in the allergy clinic. Patients under the care of our Ear, Nose and Throat (ENT) and Respiratory services can be referred for testing for air-based allergies such as Epithelia (pets) moulds and yeast and seasonal allergens (trees, grasses, and weeds). As the first patient sits down they are asked to pop their arms on a cushion with the inside of their forearms facing upwards.
“We always run a control test to make sure there is nothing that will interfere with the results such as anti-histamine in the patient’s system,” Gemma tells me as she writes numbers along the patient’s arm. “Each number refers to the allergy we are testing. The first test is always histamine and that should show up as a white/pink and slightly raised ‘’wheal’’. We then test the remaining allergies by dropping a blob of the allergen next to the number and ‘popping’ it so it is absorbed into the skin. After 20 minutes, we check the arms looking for a white/pink, raised area that is bigger than 3mm, anything over this indicates an allergy. If an allergy becomes clear the patient is given information about what to do and the results are sent back to the referring consultant.”
The team see around 9 patients a week for allergy testing, but anyone needing food allergy testing is sent to Addenbrooke’s.
Once I finish up with Gemma, I am taken to the laboratory to see lung function tests. Unfortunately the patient ‘did not attend’, but the team put me in the patient’s shoes and literally take me on their journey. First up is the ‘body box’ (pictured) and while I was pretty excited about going in and having a go, as soon as the doors shut I feel anxious. I am asked to put a peg on my nose and breathe through a mouthpiece, breathing normally until they are ready for me to take a big breath in and out. This is to measure my lung capacity and my residual volume (how much air is left in your lungs). It’s all going well until they block off my mouth piece. I knew it was coming. They told me before I went in and explained that I would need to breathe quicker against the block for about three breaths so they could measure the pressure change during this time. But for whatever reason, I lose all rational thought, panic and forget all of my instructions. I have a feeling I would make a bad patient.
Next was the gas transfer test to see how well the oxygen was transferring from my lungs into my blood stream, which was simple enough, I just needed to take a deep breath and hold it for 8 seconds before releasing. No dramatic incidents during this one.
The final test is a spirometry to assess how quickly I can move air in and out of my lungs. I need to fill my lungs with air and expel as soon as I am full – sounds simple, right? I am not a good student as my first two attempts fall out of the normal range – I don’t suspect a thing until the end of my third try when Melanie does a big sigh of relief.
“You had me worried for a second there,” she tells me. "Technique is so important in this test and can cause abnormal readings, but we are usually able to tell and coach patients until we get an accurate results."
I am a healthy adult and I found it difficult to follow, I can’t imagine how it must feel when you are already poorly and anxious about the outcome! But the team are fantastic and while each patient is doing the tests they are quietly monitoring the outcomes, keeping up that calm persona even when tests aren’t showing positive results.
If this blog has piqued your interest and you would like to learn more about a career as a clinical physiologist, visit: https://www.healthcareers.nhs.uk/explore-roles/healthcare-science/roles-healthcare-science/physiological-sciences
