Ventilation
movement of air in and out of the lungs
Respiration
The process by which cells break down simple food molecules to release the energy
... [Show More] they contain.
Minute Ventilation (VE)
Set flow of expired gas in one minute
VE = VT x RR
Normal VE is 5-8L/min.
< 10 weaning
alveolar ventilation
The volume of air that reaches the alveoli.
Measured by PaCO2
It is determined by subtracting the amount of dead space air from the tidal volume.
Functions of the pulmonary system
ventilate alveoli
diffuse gases in and out of blood,
perfuse the lungs so that the organs and tissues of the body receive blood that is rich in O2 and low in CO2
Diaphragm
Large, flat muscle at the bottom of the chest cavity that helps with inspiration
contracts > increased negative pressure in the lungs and draws air in
Accessory muscles of inspiration
sternocleidomastoid and scalene muscles
Exhalation
The passive part of the breathing process in which the diaphragm and the intercostal muscles relax, forcing air out of the lungs.
alveolar surface tension
promotes ease of breathing
Surfactant
chemical produced in the lungs to maintain the surface tension of the alveoli and keep them from collapsing
elastic recoil of the lungs
ability of the chest wall to return to normal after inspiration
generally passive
accessory muscles help if elastic recoil is not enough, i.e. COPD
Compliance of pulmonary ventilation
Ease with which the lungs and thoracic wall can be expanded
determined by alveolar surface tension and chest wall elatic recoil
increases w/ COPD
decreases w/ ARDS, pneumonia, pulmonary edema
airway resistance
dependent on the length, diameter, radius of airways and density, viscosity, velocity fo the gas exchange
normal = low
bronchodilation decreases airway resistance
bronchoconstriction increases airway resistance
gas transport steps
1. lung ventilation
2. oxygen diffusion from alveoli to the blood
3. perfusion of the organs and tissues
4. diffusion of oxygen from the blood to the cells
removal of CO2 steps
1. diffusion of CO2 from the cells into the blood
2. Perfusion of lungs via venous system
3. CO2 diffusion from the blood into alveoli
4. exhalation
barometric pressure
total pressure in the air exerted by all gas molecules
partial pressure
pressure exerted by one gas, i.e. PaO2
Effective gas exchange requires:
equal distribution of ventilation and perfusion
clear airways
normal lungs and chest wall
adequate pulmonary circulation
lung zones
Zone 1 - apices, ventilation is greater than perfusion
Zone 2 above left atrium
Zone 3 - base of lung, perfusion and ventilation are best
V/Q ratio
A measurement that examines how much gas is being moved effectively (ventilation) and how much blood is gaining access to the alveoli (perfusion)
Normal is .8
Low VQ = issue w/ ventilation
high VQ ratio = normal ventilation, impaired perfusion
restrictive lung disorder
condition limiting the intake of air into the lungs
decreased lung volume and decreased FVC [Show Less]