Exam 3: Pulmonary Ventilation, Gas Exchange And Gas Transport Flashcards
What percentage of blood is oxygen is transported bound to hemoglobin?
97%
The remaining 3% of blood oxygen that is not bound to hemoglobin is transported how?
As a dissolved gas
The oxyhemoglobin dissociation curve is a graph that shows what?
The relationship between the partial pressure of oxygen and hemoglobin binding/saturation
The oxyhemoglobin dissociation curve shows at the arterial partial pressure of oxygen (~95 mmHg) will results in what percentage of hemoglobin binding/saturation?
95-100% (~97% on average)
The oxyhemoglobin dissociation curve shows at the venous partial pressure of oxygen (~45 mmHg) will results in what percentage of hemoglobin binding/saturation?
~ 70%
What is the effect of a lower venous saturation of hemoglobin vs. arterial saturation?
It causes the oxygen to be unloaded at the tissue
An increase in activity/exercise will affect the venous saturation of hemoglobin how?
Decrease % saturation
What is the atmospheric partial pressure of oxygen?
105 mmHg
At atmospheric partial pressure of oxygen (i.e. in the alveoli of the lungs), what is the saturation of hemoglobin and what would happen if the partial pressure of oxygen was increased beyond atmospheric (105 mmHg)?
Hemoglobin is almost fully saturated at atmospheric pressure and increasing the partial pressure beyond this has little effect of saturation due to the nature of the dissociation curve of hemoglobin
What partial pressure results in pure oxygen saturation?
760 mmHg
Why is pure oxygen dangerous to breath?
Because molecular oxygen ins highly oxidative and can uncouple respiratory chain in the mitochondria of type 1 pneumocytes, resulting in cell death and permanent damage after 24 hours of exposure
What conditions in the tissue would result in the oxyhemoglobin dissociation curve shifting to the right?
- Increased H+ (decreased pH)
- increased temperature
- increased 2,3-DPG
What is it called when the dissociation curve of oxyhemoglobin shifts to the right?
Bohr effect
What the hemoglobin dissociation curve shifts to the right due to increased metabolism of tissues, what effect does this ultimately have on oxygen delivery? Why?
Increased oxygen delivery because the hemoglobin saturation (i.e. oxygen binding capacity of hemoglobin) is lowered, thus increasing unloading behavior at the tissue
There are three ways that carbon dioxide is transported in the blood. What is the most common method and what percentage of blood carbon dioxide is transported that way?
~ 70% transported as bicarbonate ion (HCO3-)
There are three ways that carbon dioxide is transported in the blood. What are the two less common methods?
~ 7% transported as a dissolved gas
~ 23% bound to hemoglobin
The formation of carbonic acid from water and carbon dioxide is catalyzed by what?
Carbonic anhydrase
At the tissue level, what happens to chloride anions?
They move inside the RBC to balance charge
At the lungs, what happens to chloride anions?
They move outside the RBC to balance charge
As an RBC passes though a tissue capillary bed where metabolism is happening, what happens?
- ↑ CO2
- ↓ pH or ↑ H+ (from about 7.45 to 7.35)
- ↑ HCO3-
- ↓ plasma Cl-
- ↑ O2 delivery (the Bohr Effect)
As an RBC passes through a pulmonary capillary bed where ventilation is happening, what happens?
- ↓ CO2
- ↑ pH or ↓ H+ (from about 7.35 to 7.45)
- ↓ HCO3-
- ↑ plasma Cl-
- ↑ O2 uptake (the Bohr Effect in a “kind” of reverse)
What is the Haldane effect?
↑ O2 displaces H+ from hemoglobin, which drives the carbonic acid reaction in a direction such that there is
↑ CO2 release from the blood
Respiration, the process of breathing
Pulmonary ventilation
Normal, quiet, resting breathing depends on
Abdominal breathing
Contracting the diaphragm pulls it in which direction and what part of the cycle of breathing results?
Downward; inhalation
Relaxing the diaphragm draws it in which direction and what part of the cycle of breathing results?
Upward; relaxation/exhalation
Rib-cage muscles of inhalation
- External intercostals
- Some parasternal intercostals
- Anterior scalene
- Serratus anterior
- Sternocleiodomastoid
Rib-cage muscles of exhalation
- Rectus abdominus
- Internal intercostals
Restful breathing is predominantly
Diaphragmatic
Vigorous breathing is predominately
Rib-cage based
All the muscles of ventilation serve to change the shape of the chest and therefore change the
Pressure on the lungs
What kind of pressure is the pleural cavity under?
Negative pressure
Name the space between the lungs and the thoracic wall
Intrathoracic or intrapleural space
Name the space within the lungs
Intrapulmonic (lung) space
What is the substance that type 2 pneumocytes release in the intrapleural space that lessen H2O effects
Surfactin
How do you change the intrapleural pressure?
Increase or decrease the size of thorax
Note: the lungs will follow the change in shape because they want to keep the negative pressure
Pressure against the lung walls that is a combination of inside and outside pressure
Transmural pressure
Three types of work that must be done in order to breath
- Respiratory work/compliance work
- Airway work
- Tissue work/tissue resistance work
What type of work is required where all energy (in an ideal system) is converted into air movement
Respiratory/compliance work
Respiratory work =
Force X distance
Force is pressure
Distance is volume
So respiratory work is pressure X volume
What type of work is it where some energy is used to move tissues around
Tissue resistance work
T/F. More tissue work is required in ribcage-based ventilation.
True.
More tissue work required within breathing shifts from diaphragmatic to ribcage-based. Which is why ribcage is used second over the diaphragm.
What kind of work is required to overcome the drag on all respiratory tree linings?
Airway work
Obstructed airways or bronchi-constricted ones (ie. Asthma) would require what kind of work
Airway work
Q =∆P/R
Q is airflow
∆P is atmospheric vs. intrapulmonic pressure
R is airway drag
The prime determinant in airway work is
R^4, or the airway drag
Exhalation is a matter of capturing stored energy of inspiration. Then deduct tissue and airway work of expiration and the remaining is the
Free work of expiration
Total energy spent breathing
3-5%
Airway restrictions and tissue scarring may
Increase the work of breathing
Regular amount of air ventilated per breath
Tidal volume (500 ml)
Amount of air that can be inhaled after tidal volume
Inspiratory reserve volume (3,000 ml)
Amount of air that can be exhaled after tidal volume
Expiratory reserve volume (1,000 ml)
Expiratory reserve + tidal volume + inspiratory reserve
Vital capacity (4,500 ml)
Amount of air still in lungs after complete exhalation
Residual volume (1,000 ml)
Vital capacity + residual volume
Total lung capacity (5,500 ml)
Tidal volume
500 ml
Inspiratory reserve volume
3,000 ml
Expiratory reserve volume
1,000 ml
Vital capacity
4,500 ml
Residual volume
1,000 ml
Total lung capacity
5,500 ml
Vital capacity is dependent on
Normal and abnormal anatomical and physiological factors
Normal anatomical factors that impact vital capacity
Body size (large = ↑VC) Body type (tall/thin = ↑VC )
Abnormal anatomical factors that impact vital capacity
Kyphosis or scoliosis scoliosis (↓VC)
Respiratory paralysis like polio, cervical injury (↓VC)
Normal physiological factors that impact vital capacity
Muscle strength (conditioned = ↑VC ) Vigor of effort (trying hard = ↑VC )
Abnormal physiological factors that impact vital capacity
Pulmonary congestion ↓VC Reduced compliance (asthma, bronchitis, tuberculosis, pleurisy, etc) ↓VC
A volume parameter that incorporates time as part of vital capacity measurement that is a forced inhale
Forced vital capacity (FVC)
Amount of vital capacity exhaled in 1 second or 3 seconds that is often expressed as a % of VC
Forced expiratory volume
Average flow during the middle part of forced vital capacity that lowers with obstructive diseases
Forced expiratory flow
Spirometry is measuring
Volume and capacities (collection of volume) over time
The total new air moved into the respiratory system per minute
Minute respiratory volume
Minute respiratory volume equation
Tidal volume X respiratory rate
At rest: 500 ml X 12 bpm ~ 6 liters/minute
What is the average minute respiratory volume
6 liters/minute
The amount of air arriving at the alveoli
Minute alveolar volume
T/F. Minute respiratory volume does NOT equal the amount of air arriving at alveoli
True
Some ventilated air is wasted filling up larger airways and do not participate in gas exchange. This is anatomical dead space.
How much anatomical dead space in the body
150 ml in typical lungs
Average minute alveolar volume
4.2 l/m
Tidal volume = 500 ml
Anatomical dead space = 150 ml
Breathing rate of 12 breath/min
= 4.2 l/m
The atmospheric air that we breath has O2 pressure of about
160 mmHg
The atmospheric air that we breath has CO2 pressure of about
0 mmHg
How soluble is O2 and CO2 with water?
O2 not soluble
CO2 is very soluble
CO2 is _____ more/less diffusable than O2
20X more
Diffusion is a function of 3 factors
- Concentration gradients
- Solubility of gases
- Nature of barriers
Gas solubility is determined by
Solubility coefficient (S) and molecular weight (MW) of the gas
A concentration gradient concept represented as a _________ for a given gas
Pressure differential (∆P)
Henry’s Law states that partial pressure X solubility =
Dissolved gas
What is the prime determinant of gas exchange/diffusion (D) in the lungs (or tissues)
∆P or the pressure differential
Thus, D =∆P. Diffusion is determined by partial pressure of gas. And ∆P is determined by ventilation.
What is O2 mmHg at atmospheric air at sea level?
160 mmHg
What is CO2 mmHg at atmospheric air at sea level?
0 mmHg
What is O2 mmHg in the lungs?
105 mmHg
What is CO2 mmHg in the lungs?
40 mmHg
What are the five things that affect partial pressure difference in the lungs?
- Mixing old and new air (takes 10 breaths to fully exchange all air)
- Humidification of incoming air (H2) displaces all partial pressures downward a little)
- Absorption/disappaearance of O2 into blood (as long is blood is flowing away from alveoli, O2 is swept away to the tissues)
- Production/liberation of CO2 from the blood (as long as flowing toward alveoli, CO2 is delivered to the lungs)
- Ventilation (rate and depth of breathing)
How many breaths does it take to fully exchange all air
10+
Because of dead space and residual volume
In humidification of air, what displaces all partial pressures downward a little?
H2O
When blood flows away from alveoli, _____ is taken from the lungs to the tissues.
As long as blood flows to the alveoli, ____ is delivered from the tissues and to the lungs.
O2 goes to tissues; CO2 goes to lungs
What is arguably the main factor that affects partial pressures in the lungs?
Ventilation
Note: This is the rate and depth of breathing combined that exchanges air on a cyclical basis.
Resting consumption rate of O2 is ____; exercising consumption rate of O2 is ______
Resting = 250 ml O2/min Exercising = 1,000
Resting consumption rate of CO2 is ____; exercising consumption rate of CO2 is ______
Resting = 200 ml/min Exercising = 800 ml/min
Ventilation must [increase/decrease] during exercise in order to maintain normal alveolar PO2 (105 mmHg) and PCO2 (40 mmHg) levels
Increase
Blood flow passing alveoli
Perfusion
Ventilation-perfusion ration (V/Q)
Want air in lungs to go to the same places as blood is bringing CO2
Note: Also called V-P matching. Too much ventilation is a waste of work. Too little ventilation will not allow for full gas exchange.
When V/Q = 0, there is
For example: blocked alveolus
No ventilation
Note: physiological shunt occurs
When V/Q = 0 and there is no ventilation, what do PO2 and PCO2 levels change from and to?
PO2 = 105 ↓ 40 mmHg PCO2 = 40 ↑ 45 mmHg
When V/Q = infinity, there is
For example: obstructed blood vessel
No blood flow
Note: physiological dead space is formed (similar to anatomical dead space, though not for anatomy reasons)
When V/Q = infinity and there is no blood flow, what do PO2 and PCO2 levels change from and to?
PO2 = 105 ↑ 160 mmHg PCO2 = 40 ↓ 0 mmHg
Normal V/Q is about
0.8 (no associated units)
Note: actual V/Q varies through the [at rest] lungs
V/Q is “high” or “low” or “just right” in thirds of the lungs at rest. What 1/3 of the lung is associated with each zone?
- High V/Q in upper 1/3 of lungs
- Just V/Q right in middle 1/3rd
- Low V/Q in lower 1/3 lungs
Note: this is V/Q with a lung at rest. During exercise, redistribution occurs and all areas develop V/Q relationships as BP and flow increase
What happens to V/Q in the upper 1/3 of the lungs with exercise?
Better Q
In hypoxic conditions, what happens to blood vessels and why? (Recall from exam 2)
↓ O2 = vasoconstriction so that V/Q can be preserved by redirecting blood flow to better ventilated areas
In 1 second travel through capillary results in a movement of O2 from ____ to ___. Average is ____
Initially 65 mmHg ↓ 0 mmHg; average 11 mmHg at rest
Systemic arterial blood PO2
95 mmHg
Upon arriving at tissues, O2 level
Drops to 40 mmHg
O2 in a cell’s cytoplasm
25 mmHg
O2 in mitochondria of a cell
5 mmHg
A measure of difference in PO2 from systemic arterial blood to the systemic venous blood
Arterio-Venous Oxygen Difference
Note: this concept expresses amount of O2 removed by tissues
Arterio-Venous Oxygen Difference at rest
55 mmHg
Increase in AV O2 difference (Arterio-Venous Oxygen Difference) means that
Tissues are metabolizing more
Systemic venous blood PO2
40 mmHg
Upon arrival at tissues, CO2 level rises to
45 mmHg
Systemic venous blood PCO2
45 mmHg
In 1 second travel through capillary results in a movement of CO2 from ____ to ___.
5 mmHg; 0 mmHg
Local flow is primarily controlled by the release of local factors at tissues which causes
Vasodilation
Vasodilation will allow for more efficient
CO2 removal and O2 delivery
