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Pulmonary changes at high altitude and altitude sickness
Pulmonary changes during exercise
Anatomic and physiologic dead space
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|Calculated tidal volume (VT) ||500 mL|
|Upper airway volume ||80 mL|
|Conducting airway volume ||100 mL |
|Inspired CO2 pressure (PICO2) ||1 mmHg |
|Arterial CO2 pressure (PACO2) ||50 mmHg |
|Expired CO2 pressure (PT) ||20 mmHg |
Normally, during an inhale - the diaphragm and chest muscles contract to pull open the chest and that sucks in air like a vacuum cleaner, and then during an exhale - the muscles relax, allowing the lungs to spring back to their normal size pushing that air out.
Within the lungs, the bronchi divide into progressively smaller and smaller bronchioles until air gets down to tiny thin-walled air-sacs called alveoli which are surrounded by tiny capillaries. This is the site of gas exchange.
So, the part of the respiratory tree prior to these alveoli, starting from the nose, or the mouth, right up to the tiny terminal tiny bronchioles without these alveoli, merely acts to conduct or transport air to the alveoli. This part is known as the conducting zone and it does not take part in gas exchange.
The volume of air contained in this conducting zone is known as anatomic dead space.
‘Dead’ sounds kind of ominous but it basically reflects the fact that this air is as good as dead to the body, because you can’t extract oxygen from it.
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