Every night, millions of people stop breathing without knowing it. Not once, but sometimes hundreds of times. Their remedy? A mask, a hum and the steady whisper of pressurised air.
Author
- Michelle Spear
Professor of Anatomy, University of Bristol
It's not glamorous, but behind the awkward nighttime aesthetics of a Cpap (continuous positive airway pressure) machine lies a remarkable piece of engineering. It doesn't just help you breathe; it reshapes the way your airway behaves.
So how exactly does Cpap manipulate the body's anatomy to prevent sleep apnoea? The answer lies in an elegant understanding of pressure, posture and the floppy vulnerability of the human throat.
Obstructive sleep apnoea (OSA) occurs when the soft tissues of the upper airway - particularly the tongue, soft palate, uvula and pharyngeal walls - collapse during sleep, temporarily blocking airflow. But why does this happen?
The anatomy of the upper airway is uniquely precarious. Unlike the lower airway, which is supported by cartilage rings and rigid structures, the upper airway - specifically the pharynx - is a collapsible tube made up of muscle and mucosa.
It sits behind the tongue and soft palate and serves as a shared pathway for both breathing and swallowing. During wakefulness, muscle tone keeps this space open. But during sleep, especially in the deeper stages, muscle tone decreases.
In people with obstructive sleep apnoea, this reduction allows the soft tissues to sag inward, blocking airflow. Factors such as neck circumference, fat distribution and the shape of the skull and face can all increase this risk.
The result is a repetitive cycle of obstruction, oxygen deprivation and interrupted sleep. It's a disorder rooted not in the lungs, but in the structure and behaviour of the upper airway. Enter Cpap.
Pneumatic splint
The machine doesn't breathe for the individual; it acts more like a pneumatic splint. By delivering a constant stream of pressurised air through a mask, Cpap machines increase the pressure inside the upper airway just enough to keep the soft tissues from falling inward.
Picture the airway as a soft-sided tent: without support, it collapses inward. Cpap works like internal tent poles, quietly holding it open from within. Anatomically, this means the base of the tongue, the soft palate and the pharyngeal walls are gently pushed outward, preventing contact and collapse.
Over time, in some users, there may even be mild adaptations in tissue tone and airway behaviour during sleep, although Cpap isn't a curative device.
The pressure settings are crucial and typically calibrated to each individual. Too low and the airway still collapses. Too high and the person may experience discomfort or aerophagia (swallowing air). But when correctly calibrated, Cpap doesn't just reduce apnoea events, it can restore the natural stages of sleep, improve blood pressure and dramatically enhance quality of life.
Cpap's effect isn't limited to the upper airway; it also influences how the chest muscles work during breathing. By keeping the airway open, it makes it easier to breathe at night, so the breathing muscles - such as the diaphragm and the muscles between the ribs - don't have to work as hard.
It also stops the repeated drops in oxygen that can trigger the body's stress response, which is the main reason why untreated sleep apnoea increases the risk of heart problems.
There's also evidence that long-term Cpap use can reduce swelling and inflammation in the upper airway . However, the benefits of Cpap depend a lot on people using it consistently. Unfortunately, the size and noise of the equipment can make it hard for some people to use it regularly. Despite this, it remains the gold standard treatment, especially for moderate-to-severe sleep apnoea.
For all its noise, Cpap is a quiet triumph of anatomical insight applied to engineering. Instead of surgery or drugs, it uses air - the same substance that betrays the sleeper with every collapse - to reclaim the airway and restore function. It is, in essence, a machine that manipulates the pliability of human anatomy to therapeutic advantage.
It may not be glamorous. But for many, Cpap is nothing short of life-changing - an anatomical nudge toward a safer, deeper and more restful night's sleep.
Michelle Spear does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
