Module 3: Respiration Flashcards
What is gas exchange driven by?
Pressure gradients at both PULMONARY capillaries and SYSTEMIC capillaries
Alveoli PO2 = ____ mmHg
103
Describe the PO2 levels of pulmonary capillaries as they return from the tissues and when they leave to go to the rest of the body
PO2 of blood returning from tissues = 40 mmHg
PO2 of blood leaving pulmonary capillaries is saturated with O2 so it goes up to 100 mmHg
Alveoli PCO2 = _____ mmHg
40
Describe the PCO2 levels of pulmonary capillaries as they return from the tissues and when they leave to go to the rest of the body
PCO2 of blood returning from tissues = 45 mmHg
PCO2 of blood leaving pulmonary capillaries has REDUCED it’s CO2 so that it it is 40 mmHg
The tissue PO2 can be as low as ___ mmHg (depending on _____)
20 mmHg
metabolism demand
Tissue capillary PO2 of blood entering tissues is:
90-100 mmHg
Blood leaving the tissue capillaries that has already delivered its O2 is approx: ____ mmHg
40
Tissue PCO2 = ____ mmHg (depending on ____)
46 mmHg
metabolism demand
Tissue capillary PCO2 is ____ mmHg
40 mmHg
Blood leaving the tissue capillaries that has increased it’s CO2 now is approx. ____ mmHg
45 mmHg
Percentage of Oxygen in atmospheric air:
Calculate it’s partial pressure
21%
PO2 = 760 x 21% = 159 mmHg
Percentage of CO2 in atmospheric air
Calculate it’s partial pressure
.03%
PCO2 = 760 x .03% = .22 mmHg
What is the percentage of O2 and CO2 in alveolar pressures?
O2 = 14.5% (760-47)(14.5%) CO2 = 5.5%
What is an average resting Cardiac Output (CO)
5 L/min
What is the average exercise cardiac output (CO)?
up to 25 L/min
Which is more compliant with alveoli ventilation: the base or the apex of the lungs?
Why?
The base because the alveoli are smaller and have a reduced surface tension and therefore easier to inflate
The apex inflates during extremes of ventilation (WOB/accessory muscles, etc)
Pulmonary circulation and function are ____ dependent.
Gravity
What happens if alveolar gas pressure exceeds capillary pressure?
Perfusion slows or stops
The capillary “collapses” or “is compressed” thus blood flow stops
Where are the three zones of ventilation and perfusion located in the lung?
Zone I: At apex (small area)
Zone II: Area above left atria
Zone III: Base of the lung
Zone I: describe relationship between pressures and what happens to perfusion
Alveolar pressure > arterial capillary pressure > venous capillary pressure
Perfusion: is STOPPED by the alveolar pressure
Zone II: relationship between pressures and what happens to perfusion
Arterial capillary pressure > alveolar pressure > venous capillary pressure
Perfusion: is SLOWED DOWN by alveolar pressure
Zone III: relationship between pressures and what happens to perfusion:
Arterial capillary pressure > venous capillary pressure > alveolar pressure
Perfusion: is NOT EFFECTED by the alveolar pressure
V/Q ratio
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)
AKA: Alveolar Ventilation / Cardiac Output
V/Q ratio between base and apex of lung:
Apex: Ventilation exceeds perfusion so a very small portion of lung
Base: Perfusion exceeds ventilation
Clinical V/Q
The sum of V/Q from all zones
Normal = 4.2L / 5.0L = 0.8 (ventilation slightly less than perfusion)
How do you calculate alveolar ventilation?
(Tidal Volume - Dead Space) x RR
(500ml - 150 ml) x 12 = 4.2 L
What happens to V/Q during moderate exercise?
V/Q remains at 0.8
Both ventilation and respiration increase proportionately
What happens to V/Q during intense exercise?
V/Q increase 5/1
This means ventilation increases much more than perfusion
Are lungs a limiting factor in exercise?
NO!!
If blood flow is obstructed then what happens to V/Q?
Name a clinical example
V/Q INCREASES infinitely
ex: Pulmonary Embolism
If ventilation is obstructed then what happens to V/Q?
Name a clinical example
V/Q DECREASES
ex: COPD
What drives oxygen transport across alveolar capillary membranes?
The pressure gradient
How long (in seconds) does it take RBC to travel through pulmonary capillaries
0.75 seconds
How long (in seconds) does it take to bind O2 to hemoglobin?
0.25 seconds
SaO2 =
saturation of oxygen in arterial blood
100% saturation of oxygen in the blood =
transport a max of 20 ml of O2 per 100 ml of blood
______ partial pressure of arterial O2 (paO2) will ______ Hb affinity for O2
INCREASED partial pressure of arterial O2 (paO2) will INCREASE Hb affinity for O2
______ partial pressure of arterial O2 (paO2) will ______ Hb affinity for O2
DECREASED partial pressure of arterial O2 (paO2) will DECREASE Hb affinity for O2
What does the “Oxyhemoglobin dissociation curve” demonstrate?
Saturation amounts at different pressures
Describe the “flat” top portion of the oxyhemoglobin dissociation curve:
Represents a “buffer” zone
60-100 mmHg
Increased O2 binding to Hb is maintained at these pressures
Describe the “steep” portion of the oxyhemoglobin dissociation curve:
This portion progressively favors O2 to be released into systemic tissue
O2 dissociation from Hb is increasing as these pressures decrease
What are the 4 factors that alter the oxyhemoglobin dissociation curve?
- Body temperature
- 2,3 DPG levels
- pH (H+) levels
- CO2 levels
What does 2,3 DPG do?
DPG alters the hemoglobin to decrease O2 affinity
“Right Shift” of oxyhemoglobin dissociation curve:
Occurs when:
Inc. CO2, Inc. H+, DEC pH levels, Inc. temp, Inc. BPG
Results in a decreased affinity for Hb and O2
“Left Shift” of oxyhemoglobin dissociation curve:
Occurs when:
H+ dec, CO2 dec, Temp dec, pH INC., dec. DPG
Results in increased affinity for Hb and O2
Acidosis
Elevated H+ levels
Hypercapnia
Elevated CO2 levels
Alkalosis
Decreased H+ levels
Hypocapnia
Decreased CO2 levels
Bohr Effect
Presence of CO2 will decrease O2 and Hb affinity
i.e., Increased CO2 levels will alter affinity
Typically occurs in tissue
Haldane Effect
Presense of O2 will decrease CO2 and Hb affinity
i.e., increased O2 levels will alter affinity
Typically occurs in lungs
If PaO2 is 100 mmHg then the blood is _____ saturated.
Is this in a healthy or unhealthy individual?
98%
healthy
If PaO2 is 60mmHg then the blood is _____ saturated.
Is this in healthy or unhealthy individual?
90%
Beginning of “flat” portion of curve…starting to be unhealthy
If PaO2 is 40 mmHg then the blood is ____ saturated
Is this in healthy or unhealthy individual?
75%
Typical of blood leaving exercising muscle
Is CO2 more soluble or less soluble than O2?
CO2 is 20 times more soluble than O2 and diffuses much quicker than O2 and thus doesn’t require a large pressure gradient
What are the 3 “forms” of carbon dioxide transport?
- CO2 dissolves into plasma
- CO2 binds to hemoglobin
- CO2 forms bicarbonate (HCO3-)
What are the percentages associated with each form of CO2 transport?
- CO2 dissolving into plasma: 5-10%
- CO2 binding to hemoglobin: 5-30%
- CO2 forms bicarbonate: 60-90%
