Breathing is a fundamental process that keeps us alive. Our bodies require oxygen (O2) to produce energy, and as a result of this energy production, carbon dioxide (CO2) is produced as a “waste product”. This intricate exchange between oxygen and carbon dioxide drives the functioning of our cells.

The amount of CO2 in our bloodstream determines our blood pH. As CO2 is transported from the cells to the lungs, where it is expelled, it influences the blood’s acidity level. Remarkably, our body is equipped with sensors throughout that can detect even slight changes in blood pH, indicating changes in concentration of CO2 levels.

To facilitate this exchange, our lungs expand through contraction of our breathing muscles, of which there are a few. These actions are in response to the increasing signals from the body’s CO2 sensors, the lungs expand which cause a drop in pressure within the lungs. This drop in pressure allows fresh oxygen to rush in while carrying away CO2 for exhalation.


The command to initiate the muscles responsible for inhalation stems from a specific area in the brainstem known as the Pre-Bötzinger complex, comprising just a few thousand neurons. This orchestration of breathing is rhythmic in nature, giving rise to phenomena like sighing, which is not prompted by CO2 levels, but rather is an inherent part of our breathing rhythm.

While our breathing generally operates autonomously at a baseline frequency which can be influenced (this is another juicy topic), we possess the ability to consciously control it. This awareness of control has been pivotal in human evolution, prompting us to harness and build upon this advantage.

Mammals, unlike most reptiles and amphibians, predominantly rely on active inhalation to move air in and out of their lungs. This evolutionary choice has given mammals an edge. Our lungs boast a vast membrane surface for efficient gas exchange, equivalent to about three-quarters the size of a tennis court. Coupled with the amazing diaphragm—a prominent dome-shaped muscle beneath the rib cage—mammals have evolved the capacity for an efficient inhalation that swiftly delivers oxygen and removes CO2 in a single breath.

In many cases, however, people fail to capitalise on this evolutionary gift. Stressful situations and high anxiety can lead to shallow upper chest breathing instead of utilising the efficient diaphragm. This faulty breathing pattern can result in neck pain, increased stress, poor sleep, compromised sports performance, hyperventilation syndrome, and various health issues.

Considering the oxygen demands of our large brain, which consumes 15-20% of the oxygen even when at rest, the diaphragm’s role gains even more significance. This energy-hungry brain could have spurred the evolution of the diaphragm, or the diaphragm may have been necessary before the building blocks of our frontal lobe were laid down facilitating the development of complex brain functions like memory, planning and language.

Furthermore, a fascinating aspect of our respiratory system is the phenomenon of sighing. Sighing occurs roughly every 5 minutes and has a distinct purpose. 

“UUuuuuuuuuuaaaaaarhhhhhhhhh” The official way to describe a Sigh

The lungs contain around 500 million alveoli—fluid-filled sacs responsible for gas exchange. A normal breath does not fully inflate all these sacs, so the brain’s Pre-Bötzinger complex triggers occasional deep breaths, or sighs, to ensure the alveoli stay functional. Neglecting these sighs can lead to alveolar breakdown, as observed in conditions like COPD, often associated with smoking.

Sighing’s importance extends to medical contexts, such as ventilator use in hospitals, where pre-programmed deep breaths in the ventilator system sustain healthy lung function. In essence, sighing serves as a crucial mechanism to uphold lung health.

In conclusion, our body’s intricate respiratory system involves a dynamic interplay between oxygen and carbon dioxide. This dance of gases fuels our energy production while maintaining a delicate pH balance. The evolution of the diaphragm and our ability to consciously control our breathing has bestowed us with unique advantages. Sighing, too, is a biological mechanism designed to protect our lungs’ functionality. As we delve deeper into the complexities of respiration, we uncover the remarkable ways our body has adapted and fine-tuned this vital process over time. 

If you are interested in learning more about your breathing and how to apply it to your performance or health, reach out!