Lecture 8.6: Physiological consequence of airway obstruction Flashcards
What are the two factors driving sensation of breathing?
Load: Given by stuff lungs, narrow airways, chest wall, diaphragm
Drive: Higher centres such as pre-botzinger complex, involves mechano, chemo, baro receptors.
True or false? In regular breathing, expiration is passive.
True.
Obstructive airways affect gas exchange because airflow to alveoli all differ. What is this referred to as? What does that mean?
Because this is at the level of alveoli, it is known as V/Q mismatch. That is, we can either have:
Adequate perfusion of gasses, but not enough gas coming in/going out because of obstruction (as in asthma). Thereby affecting the lung in patches.
Or there could be a shunt to the alveoli, whereby there is absolutely no gas as all getting to a particular alveoli. (this is a very low form of V/Q).
What are the two main reasons for obstruction in asthma?
Airway obstruction: Responsive to B-agonists, anti cholinergics.
Inflammation: Responsive to corticosteroids (regulatory and anti-inflammatory), leukotriene antagonists, mast cell stabilsers.
What is the reason for breathing difficulties in COPD?
Non-steroidal inflammation, and loss of elastic tissue.
This leads to a destruction of alveolar capillary membrane. So small airways can collapse, especially in expiration.
There is an impaired gas exchange due to perfusion issues.
Finally a reduced capillary bed, leading to pulmonary hypertension.
What is the A-a gradient?
It is the measure of efficiency of gas exchange across alveolar capillary units. It should remain below 15-30.
What is respiratory failure type 1?
Low oxygen and normal or low CO2. Occurs as a result of damage to lung tissue.
What is respiratory failure type 2?
Low oxygen and high CO2. Occurs as a result of ventilatory failure. That is, alveolar ventilation is inadequate to secrete CO2.
