Pulmonary Physiology Flashcards
(36 cards)
what is the most important function of our respiratory tract?
gas exchange
what is the 4 step oxygen pathway?
- bulk flow of gases
- alveolar to capillary passive diffusion
- bulk flow of blood
- capillary to tissues passive diffusion
what is bulk flow of gases?
oxygen molecule moves thru many branches once it comes in from environment
trachea, bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, etc
branches over 20 times!!
alveolar to capillary diffusion
oxygen gets moved from alveolus to capillary, but there are multiple things trying to stop it:
1. epithelium of alveolus
2. pulmonary capillary epithelium
3. interstitium
these try and stop the movement of gases: O2 molecule has to overcome it
where is CO2 made?
in the tissues: picked up by venous blood supply and comes thru barriers and goes into alveolus
bulk flow of blood
- relies on the CV system
- blood delivers oxygen thruout systemic circulation
- lung –> peripheral tissues –> lung
how is most O2 carried in bloodstream?
attached to Hgb
hemoglobin’s role
- increases oxygen carrying capacity of blood by 70X
- 1 gram of Hgb can carry 1.34 mL of O2
- hemoglobin saturation = percent of hemoglobin that has O2 bound to it
- measure by SpO2
increased PCO2, H+ (decreased pH), temperature, and 2,3 DPG has what effect on Hgb affinity for O2?
it DECREASES Hgb affinity for O2: harder to load, and easier to unload.
ex: if you are exercising and your body temp increases, your CO2 and H+ will increase, which tells Hgb to let go of O2 so it can get to tissues faster because there is an increased demand
trace the flow of O2 from environment and thru body
room air
trachea
primary bronchus
terminal bronchioles
respiratory bronchioles
alveolar sacs (where gas is actually moving thru)
alveolus
pulmonary capillary: dissolved in plasma, bound to Hgb
tissues
cells
mitochondria
what drives simple diffusion?
pressure gradients
- O2 from alveolus –> blood –> tissues
- CO2 from tissues –> blood –> alveolus
partial pressure = ______ x _______
concentration x total pressure
PAO2
partial pressure of ALVEOLAR OXYGEN
PaO2
partial pressure of ARTERIAL oxygen (dissolved oxygen)
SaO2
oxygen saturation in ARTERIAL blood (oxyhemoglobin)
SpO2 is from a pulse oximeter
what are the values for hypoxemia and severe hypoxemia?
hypoxemia: PaO2 <80mmHg
severe hypoxemia: PaO2 <60 mmHg
these are based on sea level
what is hypoxemia?
low arterial partial pressure of oxygen (PaO2)
what is hypoxia?
low tissue oxygen levels
what is FiO2?
- fraction of inspired oxygen
- 21% on room air- regardless of where you are
- 100% if under anesthesia
how do you alter FiO2?
by putting patients under anesthesia or in oxygen cage
what is Pb?
barometric pressure
- depends on altitude
- 760mmHg at sea level
- 640mmHg in Fort COllins
what is PiO2?
- partial pressure of inspired oxygen
- takes into account barometric pressure
- PiO2 = FiO2 (Pb-PH2O)
- saying “what am I actually inspiring:
T/F: PACO2 = PaCO2
true, about equal because it diffuses well
PvCO2
partial pressure of venous CO2
approx 5mmHg higher than PaCO2: made in tissues and is picking it up and it’s in the venous supply
assess CO2 and thus ventilation on a venous sample
