Pulmonary Mod. 3 Respiratory Fxn Flashcards
What is Gas Exchange driven by at pulmonary capillaries and systemic capillaries
is driven by pressure gradients at both pulmonary capillaries & systemic capillaries
Alveoli/Capillary Gradients
Alveoli PO2=103mmHg
Capillary PO2=40mmHg
Carbon Dioxide PP
Alveoli PCO2=40mmHg
Pulmonary Capillary PC02=45mmhg
Capillary/Tissue Gradients: Oxygen
can be as low as 20mmHg
Tissue Capillary PO2 of blood entering tissue=90-100mmHg
Blood leaving tissue capillaries (has delivered it’s O2) is 40mmhg
Capillary/Tissue Gradients: Carbon Dioxide
Tissue PCO2=as high as 46mmHg
Tissue Capillary PCO2 of blood entering: 40mmHg
Blood leaving has increased it’s CO2 and will be 45mmHg
Pulmonary Perfusion
Resting CO= 5L/min
Exercise CO= may increase up to 25L/min
Alveoli Ventilation Distribution
Base: alveoli smaller w/reduced surface tension, easier to inflate. Responsible for normal tidal volume ventilation
Apex: less compliant
alveoli contain larger residual air, larger w/increased surface tension (more difficult to inflate)
inflate during extreme ventilation
Pulmonary Perfusion Distribution
pulm circ. gravity dependent
BASE: increased blood flow at base of lungs
APEX: decreased blood flow at apex of lungs
If alveolar gas pressure exceeds capillary pressure
perfusion slows or stops
the capillary collapses or is compressed thus blood flow stops
Upright Lung; Zone I
alveolar pressure>arterial capillary pressure> venous capillary pressure
Perfusion is stopped by alveolar pressure
Upright Lung: Zone II
Arterial Capillary Pressure>alveolar pressure>venous capillary pressure
perfusion is slowed down by alveolar pressure
Upright Lung: Zone III
Arterial capillary pressure>venous capillary pressure>alveolar pressure
prefusion is not effected by the alveolar pressure
Ventilation/perfusion (V/Q) Ratio
compares amnt of air that enters the alveoli each minute with the amount of blood that travels through pulmonary capillaries each minute
V/Q at rest
4.2/5.0=0.8
- 2=TV-dead space(150)x12(breath/min)
- 0=resting perfusion c/o
V/Q during moderate exercise
ventilation and respiration increase proportionately
V/Q remains at 0.8
V/Q During Intense Exercise
V/Q increases to 5/1
ventilation increases much more than pefusion
lungs not eliminating factor in exercise
If Blood Flow is obstructed (i.e pulmonary embolism)
V/Q=increase
If Ventilation is obstructed (i.e COPD)
V/Q= decrease
Oxygen Transport Across Alveolar capillary
pressure gradient driven
Time: rest: RBC takes .75 seconds to travel through pulmonary capillary. Only .25 seconds is needed to binds O2 to Hb
Saturation of Oxygen in the Blood
at 100% sat=transports a maximum of 20mL of O2 per 100 ml of blood
Right Shift in oxyhemoglobin dissociation curve is:
Decreased affinitiy for Hb and O2
acidosis (elevaged H+ levels) and hypercapnia (elevated CO2 levels)
Left Shift in oxyhemoglobin dissociation curve is:
Increased affinity for the Hb and O2
alkalosis
hypocapnia (decreased CO2 levels)
Three forms of carbon dioxide transport
CO2 dissolves in plasma
CO2 binds to hemoglobin
CO2 forms bicarbonate HC03
CO2 dissolves into plasma
approx. 5-10% of transported CO2 in this form
continues to maintain gradient of alveoli/tissue CO2 to RBC Co2
CO2 binds to hemoglobin
approx 5-30% of CO2 transported in this form
CO2 forms bicarbonate (HCO3)
approx 60%-90% transported CO2 in this form
CO2 enters RBC
CO2 Transport in Tissue-Bohr Effect
Elevated CO2 values will decrease Hb-02 affinitiy and encourage CO2-Hb binding
Bohr effect
CO2 Transport In Lungs- Haldane Effect
Elevated O2 values will decrease Hb-CO2 affinity and encourage Hb-O2 binding
Haldane effect
The FLAT top portion of oxyhemoglobin dissociation curve
Represents a buffer zone (60-100mmHg)
The STEEP portion of the oxyhemoglobin dissociation curve
Progressively favors O2 to be released into system tissue, o2 disassociates from Hb.
Capillaries in hypoxic tissue will have lower pp of o2 so it’s easier for O2 to be released in hypoxic tissue
