Biochemistry and Physiology of Breathing
Why do we breathe?
To deliver oxygen to body cells
To remove excess CO2
Body cell requirement 2-3%
Atmospheric content 21%
Oxygen does not have to be stored. It is always available
Its purpose is to provide energy and to regenerate cells
Body requirement 6.5% or 40mm Hg
Atmospheric content 0.03%
It has to be produced by the body and stored
It is stored in the lungs at 6.5%
It is stored in arterial blood at 40mm Hg pressure
It is produced as a by product of exercise and digestion
When the child breathes through the mouth the stored carbon dioxide in the lungs escapes. This results in reduced levels of carbon dioxide in the lungs and reduced levels of carboxy-haemoglobin in the blood.
Many of the problems associated with chronic mouth breathing are as a result of this lowered level of carboxy-haemoglobin in the body.
Has 4 major functions in the body
It facilitates release of oxygen from haemoglobin
It triggers breathing by activating the medullary sensor
It maintains pH by buffering with bicarbonate or carbonic acid
It prevents smooth muscle from going into spasm
All these functions are reduced or impaired in children who are chronic mouth-breathers.
What makes us breathe?
||Although we breathe subconsciously the point that we inhale is determined chemically. As carbon dioxide builds up in the body it changes the pH of the blood and this pH shift triggers the brain to tell us to take a new breath. The Medullary Trigger reacts to levels of CO2 in the body of approximately 40mm Hg, producing a normal breathing pattern
What is normal breathing?
Gentle wave pattern
4-5 litres of air per minute
8-10 breaths per minute
Breathing in and out through the nose
This is about one breath every six seconds
What goes wrong?
The Medullary Trigger resets itself
Through constant exposure to CO2 levels lower than 40mm Hg, mainly as a result of mouth breathing, the trigger is activated far earlier, causing over breathing or hyperventilation.
This is often results in an inhale every three seconds
The Problem with Mouth Breathing
The tongue no longer provides support for the upper jaw with resulting reduced upper arch size.
The vault rises leading to reduction in the size of the nasal passages contributing to congestion of nose.
The pH of saliva elevates leading to increased rate of caries A tendency to URT infections often resulting in tonsillitis and enlarged adenoids.
The medullary trigger resets at lower level leading to hyperventilation.
The alkalinity of blood increases so less oxygen released from the blood. This is known as the Bohr Effect. Oxygen circulates the blood in the form of oxy-haemoglobin but reduced levels of carboxyhaemoglobin mean that less oxygen is released from the oxy-haemoglobin to enter the tissues so cells
Smooth muscle spasm. Gastric reflux, asthma and bed wetting are commonly associated with chronic mouth-breathing
Smooth muscle is found throughout the body
Smooth muscle goes into spasm causing:
||• Respiratory system
• Digestive system
• Circulatory system
• All hollow organs
• All tubes and ducts
||• Respiratory problems such as asthma
• Digestive disorders
• Circulatory problems
• Disturbed sleep
• Ear nose & throat issues
The Solution to Mouth Breathing
Train the child to become a natural nose breather again
Address the issues that caused the initial problem
Institute a strategy to ensure this does not recur
Fixing the problem
The Medullary trigger can be reset, by reversing the process and sending messages of increasing CO2 levels it is possible to reset the trigger and return the breathing pattern to normal