Lecture 3 (Test 2) Flashcards
What is expected in areas with the highest effect of gravity regarding blood flow?
The highest blood flow is expected in Zone 3.
What is gravity dependence in relation to blood vessels in the lungs?
Gravity dependence refers to lower vascular resistance in areas of the lungs where blood vessels are more distended due to gravity.
In healthy individuals, which zones of blood flow are typically present in the lungs?
Healthy individuals typically only have Zone 2 and Zone 3 blood flow.
What characterizes blood flow towards the top and the base of the lung?
Pulsatile blood flow towards the top and continuous blood flow towards the base.
What condition leads to the presence of Zone 1 in the lungs?
Zone 1 occurs in pathological conditions, such as being unhealthy or on a mechanical ventilator.
Where is West Zone 4 located in the lung?
West Zone 4 is located at the very bottom of the lung, compressed by the weight of the lung.
What is the alveolar pressure at the start of a respiratory cycle?
The alveolar pressure is zero.
What is the starting pleural pressure in the lungs?
The starting pleural pressure is -5.
What does the negative pleural pressure do in the lungs?
It serves to hold the alveolus open.
What happens to pleural pressure during inspiration?
Pleural pressure lowers to -6.
What is the relationship between pleural pressure and inward recoil pressure during inspiration?
Lower pleural pressure creates an imbalance that allows alveolar pressure to change.
What is the formula relating alveolar pressure, pleural pressure, and elastic recoil pressure?
Alveolar pressure = pleural pressure + elastic recoil pressure.
What is transpulmonary pressure?
Transpulmonary pressure is another name for elastic recoil pressure.
How does transpulmonary pressure affect lung volume?
Increased transpulmonary pressure leads to increased lung volume.
What are the two primary passive influences on pulmonary vascular resistance?
- Lung volume
- Gravity
What happens to pulmonary vascular resistance when norepinephrine or epinephrine is introduced?
Pulmonary vascular resistance increases.
What is the lowest possible lung volume in a healthy adult?
Residual volume (RV), approximately 1.5L.
What is the highest lung volume achievable in a healthy adult?
Total lung capacity (TLC).
What is functional residual capacity (FRC) in relation to RV and TLC?
FRC is skewed to the left of the midpoint between RV and TLC.
What does FRC stand for in lung physiology?
Functional Residual Capacity
FRC is the volume of air remaining in the lungs after a normal expiration.
How does inspiratory reserve volume (IRV) compare to expiratory reserve volume (ERV) in relation to FRC?
IRV is greater than ERV
This relationship causes FRC to be skewed towards the left on the volume axis.
What is the relationship between FRC and pulmonary vascular resistance (PVR)?
PVR is at its lowest at FRC
This suggests that spending time at FRC is beneficial for heart function.
What happens to pulmonary vascular resistance when lung volume increases from FRC?
Pulmonary vascular resistance increases
This trend also occurs when lung volume decreases from FRC.
What are the two general components of total pulmonary vascular resistance?
- Extra alveolar blood vessels
- Alveolar blood vessels
What is the effect of pleural pressure on extra-alveolar blood vessels?
Higher pleural pressure narrows the blood vessels, increasing vascular resistance
Conversely, lower pleural pressure widens these vessels, decreasing resistance.
What is the expected effect of increased lung volume on extra-alveolar vascular resistance?
Decreased extra-alveolar vascular resistance
This occurs due to the negative pleural pressure pulling the blood vessel walls apart.
What happens to alveolar vascular resistance as lung volume increases?
Alveolar vascular resistance increases
This is due to the stretching of capillaries as the volume of air in the alveoli increases.
What is the relationship between lung volume and the length of capillaries in the alveoli?
Increased lung volume leads to longer capillaries
This results in higher pulmonary vascular resistance.
What is the total pulmonary vascular resistance a function of?
The sum of alveolar and extra-alveolar vascular resistances
How does positive pressure ventilation affect pulmonary vascular resistance?
It can increase vascular resistance in extra-alveolar blood vessels
This is because positive pressure pushes against the walls of the blood vessels.
What happens to the capillaries’ diameter at low lung volumes?
Capillaries are shorter and wider
This contributes to lower vascular resistance.
What is the effect of higher right heart cardiac output on pulmonary vascular resistance?
It can decrease pulmonary vascular resistance
This is due to the increased volume of blood in the vessels.
At what lung volume is pulmonary vascular resistance typically the lowest?
At Functional Residual Capacity (FRC)
True or False: The relationship between pleural pressure and vascular resistance is direct.
False
Increased pleural pressure leads to increased vascular resistance.
What happens to pulmonary vascular resistance when right heart cardiac output increases?
Pulmonary vascular resistance typically decreases
This is because an increase in blood volume leads to distension of compliant blood vessels.
Define distension in the context of the cardiovascular system.
Widening of blood vessels due to increased blood volume
Distension lowers pulmonary vascular resistance.
What is recruitment in relation to pulmonary blood flow?
The process of utilizing additional unused blood vessels for blood flow
Recruitment lowers vascular resistance by increasing the number of pathways for blood.
What is the relationship between cardiac output and pulmonary vascular resistance?
Higher cardiac output leads to lower pulmonary vascular resistance
This relationship is counterintuitive compared to the systemic circuit.
What effect does gravity have on pulmonary vascular resistance?
Dependent regions of the lung typically have lower vascular resistance than less dependent regions
This is due to the influence of gravity on blood distribution in the lungs.
How does blood viscosity affect pulmonary vascular resistance?
Increased blood viscosity leads to increased pulmonary vascular resistance
Thicker blood makes it harder to flow through the circuit.
What is the effect of positive pressure ventilation on pulmonary vascular resistance?
It typically increases pulmonary vascular resistance
Positive pressure can compress blood vessels in the chest.
Name two factors that increase pulmonary vascular resistance.
- Alpha agonists
- Sympathetic stimulation
Both factors tend to constrict pulmonary blood vessels.
Which prostaglandin is known to relax pulmonary blood vessels?
Prostacyclin (PGI2)
It has been studied as an inhalable treatment for pulmonary hypertension.
What is the atmospheric pressure at sea level?
760 mmHg
This is equivalent to 1 atm or 760 torr.
What is the concentration of nitrogen in the atmosphere?
79%
Nitrogen is the most abundant gas in the atmosphere.
How do you calculate the partial pressure of a gas?
Multiply the atmospheric pressure by the concentration of the gas
For example, PN2 = atmospheric pressure x 0.79.
What happens to gas pressure at higher altitudes?
Atmospheric pressure decreases
This results in lower partial pressures for the gases.
What is the partial pressure of oxygen at sea level?
159 mmHg
This is calculated from 21% of 760 mmHg.
What effect does water vapor have on inspired gas pressures?
Water vapor displaces other gases, reducing their partial pressures
At body temperature, the partial pressure of water vapor is 47 mmHg.
What is the significance of the term ‘torr’?
It is equivalent to mmHg
Both are units of pressure measurement.
What is the role of atmospheric pressure in gas exchange?
It drives the movement of gases into the body
Gas movement requires both gas and pressure.
What happens to pulmonary vascular resistance if right heart cardiac output drops?
Pulmonary vascular resistance increases
This can create a vicious cycle of worsening heart function.
What happens to atmospheric air as it hits the nose and upper airways?
It is warmed quickly and humidified rapidly.
What effect does water vapor have on the partial pressures of other gases in inspired air?
It dilutes the other gases, reducing their partial pressures.
What does PIO2 represent?
The partial pressure of oxygen in humidified gas.
How much does the partial pressure of oxygen decrease in humidified air compared to dry atmospheric air?
About 10 mmHg.
What is the dry atmospheric air PO2 value?
159 mmHg.
What is the PO2 of humidified air after accounting for water vapor?
149 mmHg.
What is the partial pressure of water vapor that remains constant in the lungs?
47 mmHg.
What is the formula for calculating PIO2?
PIO2 = FIO2 (PB – PH20).
Does altitude affect the partial pressure of water vapor?
No, it remains 47 mmHg regardless of altitude.
What is the effect of bringing in fresh air on the PAO2?
It increases the PAO2.
What happens to PACO2 when fresh air is introduced?
It decreases.
What is the typical PO2 of pulmonary arterial blood?
About 40 mmHg.
How does oxygen partial pressure change as blood moves through the pulmonary capillaries?
It increases from 40 mmHg to 100 mmHg.
What is the typical PCO2 of pulmonary arterial blood?
About 45 mmHg.
How is carbon dioxide unloaded from the blood into the alveoli?
Simultaneously with oxygen absorption.
What are the average gas pressures in the alveoli of a normally functioning lung?
- PAO2: about 100 mmHg
- PACO2: about 40 mmHg.
What is the alveolar water vapor partial pressure?
47 mmHg.
What is the effect of fresh air on the alveolar gas composition?
It increases PAO2 and decreases PACO2.
What is the significance of the alveolar gas pressures?
They indicate the efficiency of gas exchange in the lungs.
What is the term used to describe the pressure of oxygen in alveolar gas?
PAO2.
What happens continuously in the lungs regarding gas exchange?
Oxygen is absorbed and CO2 is unloaded.
What is the average alveolar PO2 expected in the lungs?
About 100 mmHg.
What is the typical alveolar PACO2 after gas exchange?
About 40 mmHg.
Fill in the blank: The partial pressure of water vapor in the lungs is always _______.
[47 mmHg]
