Ventilation Flashcards
airflow is governed by
the same principles of flow, pressure, and resistance that govern blood flow
atmospheric pressure drives
respiration
intrapulmonary pressure is
the pressure within the alveoli, also reffered to as alveolar pressure
direction that air flows depends on
the gradient between atmospheric pressure and intrapulmonary pressure
Boyle’s Law
states that the pressure of a gas in a closed container is inversely proportional to the volume of its container, at a constant temperature
Charles’ Law
states that the volume of a gas in a closed container is directly proportional to its absolute temperature, at a constant pressure
ex. basketball in cold
Dalton’s Law
states that each gas in a mixture exerts a partial pressure (p) independent of the partial pressures of the other gases in the mixture
Henry’s Law
states that the amount of gas that dissolves in a liquid is directly proportional to its solubility in that liquid and its partial pressure
for air flow into lungs,
intrapulmonary pressure must be lower than atmospheric air pressure and this is accomplished by increasing the volume of the lungs
-Boyles law is important here.
when diaphragm and external intercostal muscles contract,
volume of the thoracic cavity increases
contraction of the diaphragm
increases the volume of the thoracic cavity from top to bottom
contraction of the external intercostal muscles
pulls the ribs upward and outward to increase volume of thoracic cavity from front to back
because the visceral and parietal pleurae adhere strongly to one another,
lung volume will expand as the volume of the thoracic cavity expands
increasing the volume of the lungs causes
a drop in intrapulmonary pressure
- so atmospheric air pressure is now greater than intrapulmonary pressure, so air rushes into lungs along pressure gradient
- Boyles law
normal inspiration is
an active process
normal inspiration can be increased by
contracting additional chest muscles, which further enlarges volume of thoracic cavity and decreases intrapulmonary pressure
inspiration
air flow into lungs
expiration
air flow out of lungs
for air flow out of lungs,
intrapulmonary pressure must be higher than atmospheric air pressure and this is accomplished by decreasing the volume of the lungs
when diaphragm and external intercostal muscles relax,
volume of the thoracic cavity decreases
-volume of the thoracic cavity returns to normal, which forces lungs to become smaller
decreasing the volume of the lungs cause
a rise in intrapulmonary pressure (boyles law)
-intrapulmonary pressure is now greater than atmospheric air pressure, so air rushes out of lungs along pressure gradient
normal expiration during quiet breathing is
a passive process that can be made active by contracting abdominal and internal muscles to compress the thoracic cavity
resistance affects
airflow
pulmonary compliance
the ease with which the lungs expand relative to a change in the pressure gradient between the atmosphere and the lungs