Gas Exchange & Transport And V/Q Mismatch Flashcards
Increased thickness of lung membrane =
Decreased diffusion (e.g pulmonary edema)
O2 and CO2 diffusion
Oxygen enters blood from alveolar air because PO2 is greater than that of the blood
Simultaneously CO2 molecules exit blood bc PCO2 of venous blood is much higher than alveolar air
Amount of O2 diffused into the blood each minutes depends on what factors
- Alveolar pressure gradient
- Total functional SA of membrane
- Respiratory minute volume
- Alveolar air
As altitude increases
Alveolar PO2 decreases, thus less O2 enters the blood, eventually the PO2 in air = PO2 of blood
Functional Surface area
Anything that decreases the functional SA of the respiratory membrane decreases amount of oxygen diffused into blood
E.g emphysema
Resp minute volume
Anything that decreases respiratory rate, tends to decrease blood oxygenation
E.g morphine slows resps
Hemoglobin
Contains iron and O2 has an affinity for Iron atoms allowing the iron to act as a sponge for O2 molecules
Alpha and beta amino acid chains in hemoglobin
CO2 has an affinity for these chains allowing HB to sponge CO2 and carry it well
How much does a fully saturated hemoglobin molecule unload
At rest - 25%
Exercise - 75%
O2 Disassociation curve
Describes the relationship between PO2 and O2 saturation
Rightward shift
Indicates the HB has a decreased affinity for O2
Means higher PO2 would be required to reach the same O2 saturation
Also easier for HB to release O2
Typical causes of a right shift
Exercise, stress, shock
CADET
C- CO2
A- Acid
D- DPG
E- Exercise
T- Temperature
What is DPG
this molecule stabilizes the deoxygenated form of hemoglobin. Decreased BPG concentrations create increased oxygen affinity
Left shift
HB has increased affinity for O2
Temperature
Higher - Right
Lower - Left
DPG
Higher - Right
Lower - Left
PCO2
Higher - Right
Lower- Left
Acidity
Higher pH (alkaline) - LEFT shift
Lower pH (acidosis) - RIGHT shift
Why CO2 needs to be transported
CO2 is very acidic and is transport in the blood to be eliminated by the lungs or kidneys
What ways is CO2 transported
Form of bicarbonate
Combined with hemoglobin
Dissolved in plasma
Dissolved CO2
Small amount of CO2 dissolves in plasma and is transported
This creates PCO2 of blood plasma
Carbamino compounds
25% of CO2 unites with hemoglobin to make Carbamino hemoglobin
Higher PCO2 - accelerates the binding process
Bicarbonate
2/3 of CO2 is carried in bicarbonate (HCO3-)
- CO2 dissolves in plasma and molecules bind with H2O to form carbonic acid
- some then split to form H+ and bicarbonate (H2CO3)
Higher levels of carbonic acid =
Pulls the system towards the bicarbonate ions, increasing rate of bicarbonate formation
Bohr effect
Increased PCO2 decreases the affinity between hemoglobin and O2 causing a “right shift”
Bohr effect explained
- when we blow off CO2 our blood gets alkaline and gains a stronger affinity for O2
- results in O2 being drawn toward hemoglobin
- CO2 diffuses into blood making it acidic
- resulting in a weak HB/O2 bond and it releases its O2 into blood
Tracheal breath sounds
Directly over trachea, harsh like air though a pipe
Bronchial breath sounds
Present over large airways anteriorly, loud and high pitched
Bronchovesicular breath sounds
Posterior chest between scapulae, softer than bronchial sounds
Vesicular breath sounds
Over lung tissues, soft blowing
Crackles
Light cracking produced by air passing through moisture
Wheezes
High pitched sounds produced when air moves through smaller partially obstructed airways
Stridor
High pitched inspiratory sound from partial obstruction pf larynx or trachea
Ventilation problems
Airway obstruction
chest wall impairment
Neurological impairment
Treatments for ventilation problems
Vitals/monitoring
Fix obstruction
OPA/NPA/SGA/CPAP
BVM
What is diffusion
Process of gas exchange between capillaries and alveoli
Diffusion problems
Inadequate oxygen concentrations
Alveolar pathologies
Interstitial space pathologies
Capillary bed pathologies
Perfusion
Circulation of blood through the pulmonary bed
Perfusion Problems
impaired blood flow
Capillary bed pathologies
Inadequate blood volumes
Normal V/Q
1
When functioning properly 4L of air enter resp tract and 5L of blood go through capillaries so there is ideally just enough O2 to fully saturate blood
Shunt math
Vent 0.5L O.5L
Perfusion 1L
Dead space math
Vent 1L. 2.
Perfusion 0.5L
What is a shunt
An area with perfusion but no ventilation
What is dead space
Alveoli are ventilated but no perfused
When can cyanosis become present
SPO2 less than 90%
Factors that can affect SPO2 reading
Light
Shivering
Pulse volume
Vasoconstriction
Carbon monoxide poisoning
Nail polish
Loss of blood
