phys 3 Flashcards
anatomical dead space
inspired air which remains in the airways where it is not available for gas exchange
pulmonary ventilation(L) =
“tidal volume (L/breath) x Respiratory Rate (breath/min)
“
Alveolar Ventilation is less than pulmonary ventilation because of
the presence of anatomical dead space
alveolar ventilation =
(tidal volume – dead space volume) x Respiratory Rate
pulmonary ventilation is the
volume of air breathed in and out per minute
Alveolar Ventilation is
the volume of air exchanged between the atmosphere and alveoli per minute
why is alveolar ventilation more important than pulmonary ventilation
alveolar ventilation represents new air available for gas exchange with blood
what can be done to increase pulmonary ventilation
“the depth of breathing(tidal volume) and
rate of breathing (RR) increase”
the transfer of gases between the body and atmosphere depends upon
“ventilation
perfusion”
ventilation is the rate at which
gas is passing through the lungs
blood flow and ventilation vary from ____ to ____ of the lung
“bottom, top
they are both higher at the bottom”
why are some ventilated alveoli considered as alveolar dead space
they are not adequately perfused with blood
physiological dead space =
the anatomical dead space + the alveolar dead space
Local controls act on the smooth muscles of ____ and ____ to match ____ to ____
airways, arterioles, airflow, blood flow
Increase in alveolar O2 concentration as a result of increased ventilation causes
pulmonary vasodilation which increases blood flow to match larger airflow
what happens in areas in which perfusion is greater than ventilation
“CO2 increases in the area
O2 decreases in the area
dilation of local airways
constriction of local blood vessels
airflow increases
blood flow decreases”
effect of decreased O2 on pulmonary arterioles and systemic arterioles, respectively
vasoconstiction, vasodilation
effect of increased O2 on pulmonary arterioles and systemic arterioles, respectively
vasodilation, vasoconstriction
factors that influence the rate of gas exchange across alveolar membrane
“partial pressure gradient of O2 and CO2
diffusion coefficient for O2 and CO2
surface area of alveolar membrane
thickness of alveolar membrane”
partial pressure of a gas determines
the pressure gradient for that gas
The partial pressure of gas (1) in a mixture of gases that don’t react with each other is
The pressure that gas (1) would exert if it occupied the total volume for the mixture in the absence of other components
Ptotal =
P1 + P2 +…+ Pn
partial pressure of a gas is
The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature.
value of the total atmospheric pressure
101Kpa
value of water vapour pressure in the lungs
about 47mmHg
why is there a water vapour pressure
air in the respiratory tract is saturated with water
alveolar gas equation
PAO2 = PiO2 - [PaCO2/0.8]
“Respiratory Exchange Ratio (RER)
”
“RER is the ratio of CO2 produced/O2 consumed)
normal value Is 0.8 for someone eating a mixed diet.”
where do gases move due to the partial pressure gradient
from higher to lower partial pressures
diffusion coefficient
the solubility of gas in membranes
what does a big gradient between PAO2 and PaO2 indicate
problems with gas exchange in the lungs or a right to left shunt in the heart
ficks law of diffusion
"The amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional to its thickness"
features of the lungs that help facilitate effective gas exchange
“large surface area
thin membranes”
