Ventilation and Associated Factors Flashcards
What is atmospheric pressure at sea level?
760 mmHg, referred to as 0
The higher the altitude, the _____ the pressure.
lower
What is the density of water close to the density of?
blood
What is gauge pressure?
the pressure measured against zero atmospheric pressure
How do you measure absolute pressure?
gauge pressure + atmospheric pressure
What is the total pressure equal to according to Dalton’s law of partial pressures?
the sum of individual gasses in a mixture
What does the difference in partial pressures allow for?
diffusion across the blood-gas membrane
What is the label for airway or pleural pressure?
cm H2O/mmHg
What is the label for pressure in blood vessels?
mmHg
True or False: the pressure in the pleural cavity is usually negative.
True
What is Boyle’s law?
P1V1=P2V2
What does Boyle’s law mean?
pressure and volume are inversely related; when one increases, the other decreases
What is Charle’s law?
V1/T1 = V2/T2
What does Charle’s law mean?
the volume of a gas is directly proportionate to the temperature
What is the ideal gas law?
PV=nRT
What does P stand for in the ideal gas law?
gas pressure (atm)
What does V stand for in the ideal gas law?
Volume (L)
What does n stand for in the ideal gas law?
moles of gas
What does R stand for in the ideal gas law?
the universal gas constant: 8,3145 J/mol K
What does T stand for in the universal gas law?
Temperature (degrees K)
Why is intrapleural pressure negative?
to allow for the alveoli to expand
Which part of the respiratory cycle is active?
inspiration
What happens during inspiration?
the diaphragm flattens, the inspiratory muscle contract, and the thoracic cavity expands
What happens to the intrapleural pressure during inspiration?
it becomes more negative (-4 to -6 mmHg)
What happens to the alveolar transmural pressure during inspiration?
it increases
What happens to the alveoli during inspiration?
they expand at Palv = -1 mmHg
When does air stop flowing during inspiration?
When Palv = 0 mmHg
What is the passive phase of respiration?
expiration
What happens to the body during expiration?
the diaphragm returns to dome shape, the inspiratory muscles relax, the internal intercostal and abdominal muscles contract, and the thoracic cavity returns back to normal size
What happens to the intrapleural pressure during expiration?
it is less negative (-6 mmHg to -4 mmHg)
What happens to the alveolar transmural pressure gradient during expiration?
it decreases
What happens to the alveoli during expiration?
they return by elastic recoil (Palv = + 1 mmHg)
When does air stop expiring?
when Palv = 0 mmHg
What is Paw?
pressure within the airways
What is Ppl?
pressure within the pleural cavity
What happens if Ppl increases?
the lungs will not expand
What promotes the recoil affect of alveoli?
the rebound of stretched elastin and collagen
What reduces surface tension in alveoli?
surfactants hydrophilic and phobic moieties
The smaller the diameter of the alveoli, the higher the ________.
pressure
How is pressure reduced in small alveoli?
surfactant molecules being close to one another
What prevents collapsing of alveoli?
alveolar interdependence and surfactant
What alters alveolar interdependence?
emphysema
How is compliance measured?
change in volume over change in pressure
Compliance is the opposite of _____.
elasticity
Define compliance.
the ease with which something could be stretched
Define elasticity.
the tendency to come back to the original size/shape
What disease causes compliance to decrease?
fibrosis
What disease causes compliance to increase?
emphysema
Characterize emphysema
high lung volume and small pressure change - widened alveoli
What is hysteresis?
when the lung has inflated the surfactant molecules inflate, and it takes effort to open the alveoli
What is Poisuelle’s Law?
R = (8nl/pir^4)
When r is decreased by 1/2, what happens to the new R?
it is increased by 16 fold
