In using the word ‘designed’, I am not talking about a grand design in a religious or spiritual sense. I am using this term to describe the outcome of factors that have contributed to how our bodies are both constructed and function, optimally. These factors are the evolutionary influences (environment etc.) that, over a million years and more, have led to us being what we are now.

As such, the respiratory system is designed for us to breathe through or nose (see diagram) via the following mechanisms:

• The inside of the nose contains turbine like ridges, known as turbinates, which swirl the air into a refined stream most suitable for oxygen exchange.
• The hairs in the nose filter inhaled air removing it of larger debris.
• The mucous membranes in the nasal passages produce mucous that help disinfect (via lysosomes) other pollutants in the air we breathe.
• Our sinuses produce up to 2 litres of mucous per day which serve to disinfect (as per the nose), humidify (as moist air is required in the lungs for optimal gas exchange) and heat or cool inspired air.

If we breathe regularly through our mouth, we by-pass the above processes leading to:

• Poor gas exchange in the lungs as the air that enters them is not humidified.
• As a result we also dry out and irritate sensitive lung tissue which produces mucous as a protective mechanism. This mucous takes up space in the lungs that would otherwise be used for gas exchange, and wheezing can be a common consequence.
• As the air that we breathe is not filtered or disinfected of bacterial, viral and foreign particles, excessive immune system activation occurs in our tonsils, adenoids and sensitive lung tissue leaving us more susceptible colds, flu’s and respiratory tract infections.
• The support that the tongue provides the upper jaw (to counteract the pressure exerted by the cheeks on the upper jaw) is removed as the tongue position shifts to the bottom of the mouth. This can lead to narrowing of the jaw and crowding of the teeth, especially during development.
• Drying of the saliva in our mouths which disrupts the pH of the saliva, removing some of its antibacterial effect which can predispose to dental carries and upset digestion.

Moreover, we breathe up to 6 times the volume of air in, and subsequently out, when we breathe through our mouths. The deleterious effect of this is that it washes out the reservoir of 6.5% end-tidal (after exhalation) CO2, therefore disrupting our ability to achieve the optimal pH in arterial blood (7.35 via 40mmHg of CO2) required for optimal oxygen release into tissues.

Mouth breathing is a very obvious example of over breathing. Other examples include sighing, yawning, coughing, snoring, talking too quickly, laughing and yelling.