Why I smuggled a £3,500 oximeter onto the London Underground

Before smartphones, you could monitor your smartphone. blood oxygen saturation It was expensive and bulky to buy the medical equipment. This firsthand account explores an “guerrilla science’ experiment conducted at the London UndergroundInvestigating the effects of poor ventilation stale air Deep tube lines impact You can also check out our other products. You can also find out more about the following: Lethargy. By using early portable pulse oximeterWe can observe how oxygen levels change during a commute. Consumer health tech The way we monitor and measure our health has changed.

The mystery of commuter “comas”

I started my career in central London. I commuted to and from work on the Underground. I fell into a deep sleep, sometimes coma like, during my commute. Even though I had worked very hard, I suspected that the stale underground air by the end the day could have contributed to the fatigue.

Science of oxygen saturation (SpO2)

Around that time, I was working at a respiratory clinic which received new portable oxygen monitors. Oximeters. The devices work by passing through a finger a wavelength of red-orange light. By measuring the amount of light that is transmitted, they can calculate the amount of oxygen in the blood. You cannot have more than 100% blood saturation. The device does the calculations and displays them as a percent. This was pre-iPhone, and before all things miniaturized. We thought this device was incredible.

Blood carries oxygen to all parts of the body where it is used for fuel. When oxygen levels drop, it is comparable to a battery running low – performance declines. It is the brain that is affected first. That’s why we feel tired or drowsy in poorly ventilated, crowded spaces. The “stuffy feeling” is relieved by stepping outside into the fresh air.

The £3,500 rucksack experiment

The battery inside the portable oximeter could last for up to six hours. Although “portable”, it was not a true term. It was about the same size as a small hi-fi amp and was quite heavy. It had a probe that was connected to a finger with a cable. A display showed oxygen saturation levels.

Following what may have been a convivial discussion, I ended up borrowing this expensive piece of equipment for an evening – contrary to all regulations, of course. I managed to get it in my backpack, the cable coming out the top, and the probe on my finger as I descended the Underground. The display was on, but I couldn’t see it because of my fatigue. After leaving King’s Cross, I fell into my usual deep slumber.

The next morning, I reviewed my data. It’s not surprising that my The oxygen saturation level has fallen to 92% The train was at the lowest point of its journey, which is probably why I fell asleep so quickly. Fortunately, I was regularly awakened by the frequent stops and jolts. Nevertheless, I had demonstrated my point. I returned the unharmed device, relieved at having survived both the train journey and my own health intact.

Compact and affordable modern pulse oximeters

Health technology is undergoing a dramatic shift today. What once required a £3,500 “amplifier” in a rucksack can now be bought as a tiny consumer device from retailers like Lidl for around €20.

Modern pulse oximeters are ultra-compact – small enough to fit on a fingertip – and run on long-lasting batteries. Modern devices are capable of providing more information than just oxygen.

• Heart rate monitoring Real-time Pulse Tracking

• Arterial Blood Flow The volume of blood in each heartbeat.

• Waveforms in visual form Visual representation of your circulation.

Silent hypoxia: a danger to your health

We often adapt to discomfort before we fully recognise it. We may not be aware of our oxygen levels decreasing until a friend brings it to our attention. We often blame our declining oxygen levels on other factors. Breathlessness or fatigue A medical cause other than ageing may be the culprit.

This became a major issue during the COVID-19 epidemic. While many remain asymptomatic, higher-risk individuals – particularly those over 65 – can develop Hypoxia (low oxygen in the blood) without obvious signs. This “silent” hypoxia can be severe before it’s detected and have a significant impact on health outcomes.

Monitor your health at home

It is a silver lining that you can monitor oxygen saturation at home easily, inexpensively and with an accuracy that matches machines of clinical grade. For those in higher-risk categories, investing €20–€30 in a reliable device is a small price for peace of mind.

Safety guidelines for monitoring your home:

• Know your baseline You can reassure yourself by performing a 30-second quick check every two days.

• Watch this trend: Seek medical advice when levels continue to decline.

• The 95% Rule A reading of less than 95% is a serious matter and can be a sign of a medical crisis.

Note that people with COPD have lower baseline values and should follow the doctor’s advice.

The legacy of improved air quality

In the 1980s, the London Underground launched a major ventilation program to improve air quality in its deepest underground tunnels.

It would have been nice to think that my “rucksack” research was responsible for this change. But I believe the Underground staff deserve credit. They were forced to improve the air quality by their daily exposure. Today’s commute is still stuffy, but it’s safer than previous “coma-inducing journeys”.

Information provided in this column should only be used for informational and educational purposes. It does not constitute any medical advice. This column is not intended to replace a professional medical diagnosis or treatment. If you have any questions about a medical condition, always seek out the advice of a qualified physician.

Dr Marcus Stephan