When we inhale, air is drawn in to fill our lungs.
Lungs have millions of small bags called alveoli, each smaller than the ‘full-stop’ at the end of this sentence (it is the alveoli and not the lungs that take in oxygen and send out carbon dioxide).
Each alveoli is covered in a mesh of blood capillaries (very thin vessels) – imagine a paper ball covered in mesh of rubber bands.
The blood in these capillaries absorbs oxygen from the alveoli & leaves behind carbon dioxide, which the alveoli then pumps out.
Bringing oxygen to the alveoli is called ventilation & transfer of oxygen through blood is called oxygenation.
When our respiratory system is working correctly, ventilation & oxygenation happen automatically; but there could be multiple conditions that affect these.
E.g. asthma causes inflammation in oxygen airways (trachea, bronchus etc.) thus hampering ventilation; viruses can puncture lung cells and fill alveoli with fluid making portions of lungs unusable, thereby, impairing oxygenation.
Ventilators bypass the respiratory system and ensure enough oxygen is forced into the alveoli.
In milder cases, a face mask is fitted over the mouth and nose and this mask is filled with high pressure air that is forced through airways into the alveoli.
Since in this case no component invades the body, it is called non-invasive ventilation.
In serious cases, a tube is inserted into trachea aka windpipe (invasive ventilation) bypassing all organs above trachea (in picture).
Ventilators use a circuit of valves and pipes that allow inhalation and exhalation.
The ventilators also help hold the lungs open even after exhaling so that breathing effort could be reduced.
In case of liquid buildup, diuretics (substances that cause increased production of urine to clear water away) are given.
Most modern ventilating systems are connected to a computer to monitor patient’s breathing and adjusting the airflow.
Ventilation generally requires heavy sedation and repeat ventilation can cause damage to the lungs.
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