Question

Could someone please answer this for me.

we established an experiment that focus on dead space of the human respiratory system. we added an extra dead about 650ml to the human airway and it turns out when we added the that extra dead space, the inspiratory reserve volume decreased , the tidal volume increased, and the pulmonary venitilation rate increased, but the partial pressure of oxygen alveoli (mmHg) staid the same, it didn't change. .

My question is: Why is the partial pressure of oxygen alveoli (mmHg) staid the same and it didn't change when an extra dead space was added to the students airways? What is the physiological reason behind this?

Answer 1

Answer:

• Dead space is the conducting part of the airway which is not involved in gas exchange.
• So dead space ventilation is wastage of air inhaled.
• It is usually around 150 ml.So total tidak volume is 600 ml normally,but only (600-150=)450 ml reaches the lungs for gas exchange.
• This 450 ml is involved in alveolar ventilation.
• After you increased the dead space ,to maintain the same alveolar ventilation, the tidal volume has to increase.
• Inspiratory reserve volume is the extra amount of air which you can breathe in after a normal tidal volume breathing.
• Since tidal volume has already increased,inspiratory reserve volume has to decrease because there is a limit to which the lungs can expand.

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