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