Surface Tension and Airway Resistance Flashcards
What is surface tension?
Force that arises due to favorable water-water interactions and unfavorable air-water interactions
How do alveoli compensate to limit air-H20 interaction?
they become smaller
What are 3 effects of increased surface tension?
decreased lung compliance
water accumulation in the lungs
collapse of small alveoli
How does surfactant reduce surface tension?
Surfactant is a mixture of lipids and proteins with polar and non-polar ends that insert into the water layer to distribute water molecules to diminish air-water interactions
How does an increase in radius affect resistance of airflow?
decreases resistance by r^4
What type of airflow does the majority of air have in the airways?
transitional flow (between laminar and turbulent flow)
How do chemical factors affect airway resistance?
chemical factors affect smooth muscle contraction/relaxation
What are 2 examples of bronchoconstrictors?
parasympathetic nervous system (acetylcholine)
histamine (asthma)
What are 3 examples of bronchodilators?
sympathetic nervous system (epinephrine, norepi etc)
agonists for beta adrenergic receptors (isoproteronol)
CO2 in bronchioles
What are the effects on lung volume with obstructive diseases?
higher lung volumes
What is dynamic airway collapse?
airway is open when Paw > Pip
airway is closed when Paw
Why do emphysema patients breathe through pursed lips during exhalation?
Trying to increase airway pressure to keep airways open
Since emphysemic sustain higher lung volumes, how do patients compensate during exhalation?
They use muscles involved in forced expiration thus leading to a positive pressure within the lung. A downfall of this compensation is that there is airway collapse due to reduced bronchiole wall integrity.
What is the PRIMARY problem of emphysema during quiet respiration?
reduced tendency of lungs to deflate
