Our breathing patterns will determine the optimal oxygen system for paragliding

SEARCH Projects’ Pilot Tom de Dorlodot, in flight over the Karakorum wearing the Free Flight Physiology Project Hexoskin and pulse oximeter.

When Tom and Horacio flew above 6,000 m wearing our monitoring equipment, their heart and respiratory rates were higher than the pilots flying at lower altitudes. This is no surprise: at extreme altitude, our bodies can increase circulating oxygen by breathing more then pumping the oxygenated blood around faster. However, we can breath more by either increasing the rate or depth of breathing. We found that Tom and Horacio tended to increase respiratory rate at extreme altitude, rather than depth.

Most paragliding oxygen systems are pulsed-dose, delivering a fixed volume of oxygen every time the pilot draws breath. Often, pulsed-dose systems can work better with higher respiratory rates, while continuous flow systems are more suited to slower, deeper breathing. However, if the faster breathing is also very shallow, then sometimes the pulsed oxygen doesn’t trigger well or reach the alveoli where it can be transferred into the blood. We are very mindful though that Tom and Horacio were only two individuals, so we would need to know if these findings were more generalised before drawing any firm conclusions on the best oxygen system for high altitude paragliding.

Key messages

The jury is still out on the best oxygen system for pilots to use when flying at extreme altitudes. In particular, whether the system should be optimised for high respiratory rate or depth, or oxygen via the nose or mouth. It may be that current systems can be configured to better deliver oxygen to the parts of the lungs where it will be most efficiently used. (Please don’t let that put you off using oxygen though. This is still speculative, and we need to find out more.)

Why the Breathing Pattern Matters for Oxygen Delivery

When we talk about breathing at altitude, the total volume of air moved per minute is only half the story. What really matters for gas exchange is alveolar ventilation — the portion of each breath that actually reaches the tiny air sacs where oxygen crosses into the blood. A rapid, shallow breathing pattern can leave a large fraction of each breath trapped in the anatomical dead space of the trachea and bronchi, meaning that despite a high respiratory rate, the body may not be getting much more oxygen than it would at rest. For Tom and Horacio, their faster breathing at extreme altitude did increase their minute ventilation, but if the breaths were also very shallow, the gain in alveolar oxygen delivery may have been smaller than the raw respiratory rate suggests.

This distinction is particularly important for pulsed-dose oxygen systems, which are common in paragliding because they are lightweight and conserve the oxygen supply. These systems typically fire a fixed volume of oxygen at the start of each inhalation, relying on a pressure drop or flow sensor to detect the breath. If the inhalation is very shallow, the trigger may be weak or fail entirely, meaning the pilot receives no supplemental oxygen at all for that breath. Even when the trigger does fire, a shallow breath may not carry the oxygen bolus deep enough into the lungs to be useful. On the other hand, a deep, slower breath provides a stronger trigger and better mixing, which is why the breathing style we observed — fast but possibly shallow — could make pulsed-dose delivery less effective than expected.

We should be careful not to overinterpret the data from just two pilots, but the physiological principle is well established. A pulse oximeter can tell us that blood oxygen saturation is dropping, but it cannot tell us whether the oxygen we are delivering is actually reaching the alveoli. For future monitoring, we may want to add a spirometer or chest band that can measure tidal volume directly, so we can separate true shallow breathing from simply a fast rate with normal depth.

Comparing Pulsed-Dose and Continuous Flow Systems in the Air

Most paragliding oxygen setups fall into two broad categories: pulsed-dose (or demand) systems and continuous flow systems. Continuous flow delivers a steady stream of oxygen, usually through a cannula or mask, regardless of when the pilot inhales. It is simple and robust, but it wastes oxygen during exhalation and the pause between breaths. For a long flight at high altitude, that wasted oxygen adds up quickly in terms of weight and cylinder size. Pulsed-dose systems, by contrast, fire only when a breath is detected, which can extend the usable oxygen supply by a factor of two to four. This is why many high-altitude paraglider pilots choose pulsed systems despite their greater complexity.

However, our observations suggest that the choice may not be so straightforward. If pilots at extreme altitude naturally adopt a fast and shallow breathing pattern, pulsed-dose systems may under-deliver oxygen because of poor triggering or incomplete alveolar delivery. A continuous flow system would not care about breathing depth or rate — it simply provides a constant partial pressure of oxygen in the airway, and even a shallow breath will draw some of that oxygen into the lungs. The trade-off is that continuous flow is heavier and the oxygen supply may not last as long, which is a serious concern during multi-hour flights or when carrying other equipment.

One practical compromise could be a pulsed system with adjustable trigger sensitivity or a volume-based trigger that fires on very small inspiratory efforts. Some newer systems also allow the pulse volume to be increased for high respiratory rates, or they can switch to a low-flow continuous mode if the pilot’s breathing becomes too erratic. We did not test any of these features in the Karakorum flights, but they are worth investigating in controlled conditions where we can compare oxygen saturation outcomes with the same pilot using different delivery modes.

The Role of Acclimatization and Individual Variation

Tom and Horacio are experienced high-altitude pilots, but their flights over the Karakorum were likely brief exposures rather than a gradual ascent with full acclimatization. When a person spends days or weeks at altitude, the body adapts in several ways: ventilation becomes deeper and more efficient, the kidneys excrete bicarbonate to compensate for respiratory alkalosis, and the oxygen-carrying capacity of the blood increases. These changes can shift the natural breathing pattern from fast and shallow toward slower and deeper, which would favour pulsed-dose oxygen delivery. In other words, what we observed in Tom and Horacio might reflect acute exposure rather than the steady state of a well-acclimatized pilot.

Individual differences also play a large role. Some people are naturally “deep breathers,” while others tend to breathe more rapidly and shallowly even at sea level. Genetics, fitness, previous altitude experience, and even conscious breathing training can all influence this. Without a larger sample, we cannot know whether Tom and Horacio represent a common pattern for paraglider pilots or an outlier. We would need to measure baseline breathing patterns at low altitude, then repeat the measurements during high flights, ideally on the same individuals over multiple days to see how acclimatization changes the response.

Another factor worth exploring is the effect of the paragliding harness and the pilot’s position. Sitting in a harness with a chest strap and leaning forward slightly may restrict abdominal breathing, which could encourage shallower chest breathing. If so, a simple adjustment to the harness or the oxygen mask might improve breathing depth more than any change to the oxygen system itself. This is an example of how physiological monitoring in the real flight environment can reveal interactions that laboratory studies miss.

Next Steps: Expanding the Dataset and Real-World Testing

We are now planning a broader data collection effort to answer several of the open questions raised by the initial Karakorum flights. The goal is to gather enough information from a larger group of pilots to make evidence-based recommendations on oxygen system selection and configuration for high-altitude paragliding. Specifically, we aim to:

• Enroll at least 20 volunteer pilots with varying levels of high-altitude experience and measure their resting breathing patterns at low altitude using the same Hexoskin and pulse oximeter.
• Conduct repeated high-altitude flights in different regions (Himalaya, Andes, Alps) to capture a range of altitudes, temperatures, and flight durations.
• Compare pulsed-dose and continuous flow oxygen delivery in a crossover design, with each pilot using both systems on separate flights while we monitor SpO2, respiratory rate, tidal volume, and subjective comfort.
• Validate the trigger reliability of several commercially available pulsed-dose units under shallow breathing conditions simulated on the ground, before in-flight testing.
• Record cognitive performance and symptoms of acute mountain sickness using simple tablet-based tests and questionnaires during the flights, to correlate physiological data with pilot function.

We are also in discussion with oxygen equipment manufacturers about developing a paragliding-specific delivery mode that could automatically adjust the pulse volume or switch to continuous flow based on real-time respiratory rate and depth. Such a system would need to be lightweight, robust against vibration and wind, and fail-safe at very high altitude. The data from this expanded study will be made available to the paragliding community, and we hope it will lead to clearer guidelines rather than the current reliance on anecdote and trial-and-error.

This is a summary of one of our key findings from Phase I of the Free Flight Physiology Project. For a full write up of our methods and results, please see our our Cross Country Magazine article or our scientific paper in High Altitude Medicine and Biology.