B4-100 Intro to Respiratory Physiology Flashcards
alveolar gas equation
dead space equation
low tissue PO2
hypoxia
does gas exchange occur in the conducting zone?
no
does gas exhange occur in the respiratory zone?
yes
trachea
bronchi
bronchioles
make up the […] zone
conducting
respiratory bronchioles
alveolar ducts
alveolar sacs
make up the […] zone
respiratory
PICO2 is always
zero
only inspiring oxygen and nitrogen
gas exhange in the alveoli occurs […]
how quickly
immediately
why is the PAO2 less than PIO2?
gas exhange occurs immediately, so the pressure of O2 in the alveoli is less than the pressure of inspired O2 immediately
where does PACO2 come from?
venous circulation
equation for gas pressures
partial pressures equation
once air enters the lungs, it is saturated with
water vapor
partial pressures in the lungs must be corrected for
vapor pressure
subtract from atmospheric pressure
partial pressure of water is
47
subtract from atmospheric pressure
to correct for water vapor, subtract 47 from the
atmospheric pressure
PIO2 is usually about
150 mmHg
147 at KUMC
PIO2 at KUMC is about
147 mmHg
PB at KUMC is about
747 mmHg
what factors can alter PIO2?
- changing atmospheric pressure
- changing fractionated concentration
Fc of oxygen in atmosphere is about
21%
as long as there is a higher amount of oxygen in the air, it will readily diffuse into
circulation
concept: gas –> liquid
- delivered by ventilation
- removed by blood flow (metabolism)
O2
- delivered by blood flow
- removed by ventilation
CO2
high PAO2, Low PACO2
hyperventilation
low PAO2, high PACO2
hypoventilation
normal ventilation is defined as the ventilation necessary to maintain a PACO2 at
40 mmHg
ventilation is […] related to PACO2
inversely
normal PACO2 should be
40 mmHg
if alveolar PACO2 is not 40, you have a change in
ventilation
if PACO2 is > 40 mmHg, do you have hypo or hyperventilation?
hypo
if PACO2 is <40 mmHg, do you have hypo or hyperventilation?
hyper
equation for alveolar PO2
normal PAO2
100 mmHg
arterial and alveolar PCO2 are
identical
PaO2 should always be […]mmHg […] than PAO2
5-10 mmHg less
and increase in alveolar ventilation will cause a […] in PACO2
decrease
a decrease in alveolar ventilation will cause an […] in PACO2
increase
factors that impact alveolar gas exchange
- dead space
- surface tension
diffusion, shunt unit (TBD later)
anatomic dead space
conducting zones
physiologic dead space
alveoli is not getting perfused, no gas exhange
regions of the lungs that receive air, but not blood
no gas exhange
dead space
space in respiratory system other than alveoli
anatomic dead space
alveoli that receive air but not blood
physiologic dead space
in healthy individuals, physiologic dead space is
nearly zero
in healthy individuals, anatomic dead space is about
%
25-35%
dead space equation
as the difference between PaCO2 and PECO2 becomes greater, dead space
increases
volume of air breathed in a single minute
minute ventilation
minute ventilation equation
anatomic dead space can be estimated knowing the patient’s
weight
and 150 lb individual would have […]mL of dead space
150mL
alveolar minute ventilation equation
- amount of air alveoli receive over a single minute
- accounts for anatomic/physiologic dead space
alveolar minute ventilation
surface tension is determined by
law
LaPlace’s Law
LaPlace’s Law
in a large alveolus, the radius is large so pressure is
low
in small alveolus, radius is small so pressure is
high
the high pressure in a small alveoli will cause air to flow into
large alveolus
small alveoli may collapse
reduces surface tension in smallest alveoli
surfactant
lowers attractive force
what type of cells secrete surfactant?
type II alveolar
surfactant is more concentrated in […] alveoli
size
smaller
what happens if there is not enough surfactant?
- decreased compliance
- atelectasis
- pulmonary edema
due to small alveoli close
closing of small alveoli so that they cannot exchange CO2
atelectasis
