Module 3 Respiratory Function Flashcards
Define ventilation
Mechanical process by which ambient air is brougt ito and excanged with air in the lungs
Define respiration
Gas exchange that occurs in the lungs (at alveolar/capillaries) and throughout the body (at target tissue/capillaries)
Where are the pressure gradients located that control gas exchange?
Pulmonary capillaries
Systemic capillaries
What are the two components of the Alveoli/capillary gradients?
What is the pressure of O2? CO2?
Oxygen (PO2 = 103mmHg) and Carbon dioxide (PCO2 = 40mmHg)
In the alveoli/capillary gradient, what is the PO2 of blood returning from tissues? What is the partial pressure of O2 in blood leaving pulmonary capillaries?
PO2= as low as 40mmHg
Partial pressure=100mmHg
In the alveolar/capillary gradient, what is the pulmonary capillary PCO2 of blood returning from tissues? What is the partial pressure of CO2 in blood leaving pulmonary capillaries?
PCO2= 45mmHg
Partial pressure= 40mmHg
What are the two components that make up the capillary/tissue gradient?
Oxygen and CO2
What is the tissue PO2? Tissue PCO2? (in capillary/tissue gradients)
PO2= as low as 20mmHg (depends on metabolism demand)
Tissue PCO2= can be as high as 46mmHg (depends on metabolism demand)
In capillary/tissue gradients What is the tissue capillary PO2 of blood entering tissues? What is the partial pressure of O2 in blood leaving tissue capillaries?
PO2= 90-100mmHg
Partial pressure= 40mmHg (blood leaving tissue capillaries has delivered all of the O2)
In capillary/tissue gradients What is the tissue capillary PCO2 of blood entering tissues? What is the partial pressure of CO2 in blood leaving tissue capillaries?
PCO2= 40mmHg
partial pressure= 45mmHg (blood leaving tissue capillaries has increased CO2)
What is the percentage of O2, Nitrogen, CO2, and other gases in the atmospheric air?
O2=21%
Nitrogen=79%
others=<1%
CO2=0.03%
What is the equation for partial pressure for atmospheric air pressures?
PP= %concentration x total pressure of gas (air) PO2 = 760mmHg x 21% = 159mmHg
What is the percentage of oxygen and carbon dioxide in alveolar air pressures?
O2=14.5%
CO2=5.5%
What is the equation for partial pressure (alveolar pressures)?
PP=%concentration x total pressure of gas (air)
PaO2= air pressure x %O2 in air
PaO2= (760mmHg-47mmHg) x 14.5%= 103mmHg
What is pulmonary perfusion?
What is the resting Cardiac output (CO)?
What is the exercise cardiac output?
Pulmonary circulation/blood flow
Resting CO= 5L/min
Exercise CO= may increase up to 25 L/min
Alveoli ventilation distribution:
describe the base of lungs-
base is more compliant
alveoli smaller w/ reduced surface tension, EASY to inflate
Responsible for normal tidal volume ventilation
Describe the apex of the lungs-
Less compliant
Alveoli contain larger residual air and therefore larger with increased surface tension, making them more DIFFICULT to inflate
Inflate during extremes of ventilation
Main difference between apex and base of lungs?
base–> increased blood flow at base of lungs
apex–> decreased blood flow at apex of lungs
**if laying supine then more blood flow would be in osterior regions of lung and decreased in anterior regions
What happens if alveolar gas exceeds capillary pressure?
perfusion slows or stops
capillary collapses or is compressed, stopping blood flow
Describe the three zones of ventilation and perfusion variation in the upright lung-
Zone I: alveolar pressure>arterial capillary pressure>venous capillary pressure (perfusion stopped by alveolar pressure)
Zone 2: arterial capillary pressure>alveolar pressure>venous capillary pressure (perfusion is slowed down by the alveolar pressure)
Zone 3: arterial capillary pressure>venous capillary pressure>alveolar pressure (perfusion not affected by the alveolar pressure)
Describe the perfusion in each zone of the upright lung-
Zone 1: perfusion stopped
Zone 2: perfusion slowed down
Zone 3: perfusion not affected
What is the V/Q (ventilation/ perfusion) ratio?
It compares the amount of air that enters the alveoli each minute with the amount of blood that travels through pulmonary capillaries each minute (cardiac output)
How does the V/Q differ from the apex to the base of the lungs?
Apex: ventilation exceeds perfusion; very small portion of lung (high ventilation)
Base: perfusion exceeds ventilation
How does the V/Q ratio decrease?
decrease ventilation OR increase blood flow – the levels of O2 will decrease the CO2 will increase
What is the clinical V/Q measurement?
Sum of V/Q from all zones
V/Q = alveolar ventilation/cardiac output
V/Q = 0.8 (ventilation slightly less than perfusion)
What is the V/Q at rest?
- 2L/min / 5.0L/min = 0.8
* lungs very efficient at providing enough air to alveoli
Define perfusion
resting cardiac output
- 0L/min
* *in perfusion O2 is removed from alveoli and CO2 is added
What is alveolar ventilation?
(Tidal volume-Dead space) x Resting Respiration rate = alveolar vent.
Tidal volume=500ml
Physiological dead space=150ml
Resting respiration rate=12
Alveolar ventilation = (500-150)x12 = 4.2 L/min
What is the V/Q during moderate exercise?
0.8
vent and respiration increase proportionately
What is the V/Q during intense exercise?
Increases to 5/1
ventilation increases much more than perfusion
lungs are NOT the limiting factor in exercise
ex: (vent = 100L/min, while CO = 20L/min)
How does blood flow and V/Q change during a pulmonary embolism?
Blood flow is obstructed
V/Q increases infinitely
How does ventilation and V/Q change in COPD?
ventilation is obstructed
V/Q decreases
What drives oxygen transport across the alveolar capillary membrane?
pressure gradient
How long does it take for pulmonary diffusion across capillary membrane?
At rest, RBC takes 0.75 seconds to travel through pulmonary capillary
It takes 0.25 seconds to bind O2 to the hemoglobin
What is the saturation of oxygen in the blood?
SaO2 = saturation of oxygen in arterial blood
If RBC’s are 100% saturated, what does that mean?
They transport a maximum of 20ml of O2 per 100ml of blood
What is the Haldane effect?
Increased partial pressure of O2 (PO2) will INCREASE Hemoglobin affinity for O2
What is the Bohr effect?
Increased partial pressure of CO2 (PCO2) will DECREASE Hemoglobin affinity for O2
- in systemic capillaries O2 can dissociate from Hb to be released to target tissues
- in pulmonary capillaries O2 can bind to Hb to be delivered to systemic circulation
What does the oxyhemoglobin dissociation curve demonstrate?
It demonstrates saturation amounts at different pressures
The flat top portion represents a buffer zone (60-100mmg)–increased O2 binding to Hb is maintained at these pressures= haldane
The steep portion starts to favor O2 to be released into systemic tissue–O2 dissociation from Hb is increasing as these pressures decrease. capillaries in hypoxic tissue will have lower partial pressures of O2, so as the partial pressures decrease then the easier it is for O2 to be released into hypoxic tissue (bohr)
What two things can alter the oxyhemoglobin dissociation dissociation curve?
H+ and CO2 levels
- right shift=decreased affinity for Hb and O2, acidosis (elevated H+ levels) and hypercapnia (elevated CO2 levels) - temp, H+, and P-CO2 all increase
- left shift=increased affinity for Hb and O2, alkalosis and hypocapnia (decreased CO2 levels) - temp, H+, and P-CO2 all decrease
What are other factors that alter the oxyhemoglobin dissociation curve?
Body temperature and 2,3 DPG levels
DPG is an isomer located in RBCs that plays a role in regulating binding affinity of O2 and Hb (alters hb to lower O2 affinity)
Interpreting the oxyhemoglobin dissociation curve-if PaO2 is 100mmHg then the blood is 98% saturated. Where on the curve is this?
In between flat and steep zone–nearing flat zone
Interpreting the oxyhemoglobin dissociation curve-If PaO2 is 60mmHg then the blood is 90% saturated. Where on the curve is this?
The beginning of the flat portion of the curve
Interpreting the oxyhemoglobin dissociation curve-if the PaO2 is 40mmHg then the blood (hemoglobin) is 75% saturated. where on the curve is this?
This is typical of blood leaving exercising muscle.. This is in the steep zone
What does a pulse oximeter measure?
What are the Arterial O2 saturation values?
SaO2 (O2 saturation of arterial blood)
Arterial O2 saturation values:
95-97% = normal values for healthy individuals
90-95% = acceptable values for COPD or other pulmonary conditions, but still in buffer zone
Below 90% = often used as threshold for abnormal values
Describe carbon dioxide transport
CO2 is 20x more soluble than O2 and diffuses much quicker than O2
doesn’t require as large of pressure gradient
pressure gradient approximately 6mmHg in alveoli
alveoli PCO2=39-40mmHg, pulmonary arteries/capillaries=46mmHg
What are the three forms of CO2 transport and how much CO2 is transported in each form?
- CO2 dissolves in plasma (5-10% transported this way)–maintains gradient of alveoli/tissue CO2 to RBC CO2
- CO2 binds to hemoglobin (5-30% of CO2 transported this way)
- CO2 forms bicarbonate (HCO3-) (60-90% transported this way)–CO2 enters RBC, combines with H2O to form carbonic acid, carbonic acid dissociates into bicarbonate and H+, and bicarbonate dissolves back into plasma, while H+ is buffered by Hb
