3.1 Flashcards
I. Lung volumes
1. What are the types of lung volumes?
Clinically, lung volumes are subdivided into dynamic and static lung volumes
1. Dynamic lung volumes: related to the rate at which air flows in/out of the lungs
2. Static lung volumes: not affected by the rate of airflow into/out of the lungs
I. Lung volumes
2. Characteristics of Dynamic lung volumes
related to the rate at which air flows in/out of the lungs
I. Lung volumes
3. Characteristics of Static lung volumes
not affected by the rate of airflow into/out of the lungs
II. Static lung volume
1. What are 4 parameters of standard lung volumes?
1) Tidal Volume (TV)
2) Inspiratory reserve volume (IRV)
3) Expiratory reserve lung volume (ERV)
4) Residual volume (RV)
II. Static lung volume
2. What is the definition and value of tidal volume (TV)
amount of air entering/ leaving the lung w/o extra effort (500mL)
II. Static lung volume
3. What is the definition and value of Inspiratory reserve volume (IRV)?
max. inspiration above tidal volume (3100mL)
II. Static lung volume
4. What is the definition and value of Expiratory reserve lung volume (ERV)
volume exhaled besides tidal volume(1200mL)
(The extra volume of air that can be expired with maximum effort beyond the level reached at the end of a normal, quiet expiration.)
II. Static lung volume
5. What is the definition and value of Residual volume (RV)?
air remaining in the lungs after complete exhalation(1200mL)
II. Static lung volume
6. What are the 4 standard capacities?
- Inspiratory capacities (IC)
- Functional residual capacity (FRC)
- Vital capacity (TLC)
- Total lung capacity
II. Static lung volume
7. What are the definition and value for Inspiratory capacities (IC)?
IRV + TV, largest amount that can be inhaled
= 3600 mL
II. Static lung volume
8. What are the definition and value for Functional residual capacity (FRC)?
ERV + RV, vol remaining in lungs after normal expiration (2400 mL)
II. Static lung volume
9. What are the definition and value for Vital Capacity (VC)?
Entire volume that can be max. inhaled + exhaled
= 4800 mL
II. Static lung volume
9. What are the definition and value for Total Lung Capacity (TLC)
The sum of all 4 volumes
= 6000 mL
III. How does respiration take place?
Respiration takes place by movement of the respiratory muscles
=> If all muscles are relaxed, the volume in the lung is = the FRC (2400mL in male, 1800mL in females)
III. Determination of FRC
1. What are the 2 method for the determination of FRC?
- He dilution method
- Body plethysmograph
III. Determination of FRC
2. Describe He dilution method
- A closed-circuit system where a spirometer is filled with helium and oxygen
- Patient is asked to breath normally -> helium spreads into the lungs -> since no leak of substance, FRC is calculated by: C1 x V1 = C2 x (V1 + V2)
- V2 is unknown = FRC - volume at the end of normal expiration
III. Determination of FRC
3. Describe Body plethysmograph
- Air-tight cabin
- Shutter which closes inhalation/exhalation
+) Patient in the cabin can perform normal expiration. At the end of normal expiration, we close the shutter and ask the patient to make a forceful inhalation
+) Patient cannot inhale because the shutter is closed. But can extend the chest and from that we can detect the pressure changes
+) From the pressure changes, we can calculate what volume was inside the thorax, FRC, lung volume etc.
IV. Dead spaces
1. What are the characteristics of dead spaces?
Dead spaces in the lungs relate to the part that do not participate in gas exchange
- dead space is the volume in the conductive zones (1-16)
- alveolar space is the volume in the respiratory bronchioles, alveolar ducts and sacs
=> ventilation occurs there
IV. Dead space
2. What are the 2 methods for Determination of dead space?
- O2-inhalation, N2-detection in expired gas
- pCO2-measurement
IV. Dead space
2A. How to determine dead space with O2-inhalation, N2-detection in expired gas?
- Ask patient to inhale O2 and to exhale it
- During exhalation period, we detect the N2 concentration
- As long as the person is exhaling from the dead space, there will be no N2, since the patient is just exhaling what was inhaled (pure O2)
-> If we get the volume of where N2 appears, we can tell how much the dead space is
IV. Dead space
2B. How to determine dead space by using pCO2-measurement?
in dead space, the pO2 and pCO2 concentration is equal to the outside pO2 and pCO2 concentration
IV. Dead space
3. What is the anatomical dead space?
Anatomical dead space: is the volume of the conducting airway including the nose, mouth, trachea, bronchi and bronchioles.
-> When we take in a tidal volume of 500mL, 150mL of that air does not reach the alveoli for gas exchange
IV. Dead space
4. What is Functional/physiological dead space?
It is the total volume of air that does not participate in gas exchange, thus, it is the anatomical dead space + the functional dead space of the alveoli
- Functional dead space is the space of the ventilated alveoli that do not participate in gas exchange
- Physiological dead space can occur if circulation/blood flow is blocked (thrombus)
IV. Dead space
4A. How can physiological dead space occur?
Physiological dead space can occur if circulation/blood flow is blocked (thrombus):
- From this point (thrombus), there will be no gas exchange, but the alveolus is still ventilating
- The pO2 will be the same, as in the other alveolus (pO2=150)
- If no blood flow -> nowhere for the gases to go to -> the volume of the alveolus becomes part of the dead space, because there is no circulation
V. Alveolar ventilation
1. What are the characteristics of Alveolar ventilation?
- There an inverse relationship (hyperbolic) between the alveolar ventilation (VA) and the alveolar pCO2 (PACO2)
- Relationship between the CO2-production (VCO2) and PACO2 is a linear relationship
=> The equation tells us the relationship between work and breathing
V. Alveolar ventilation
2. Give the formula for alveolar ventilation
V. Alveolar ventilation
3. What happen if there is more work?
we produce CO2
V. Alveolar ventilation
4. What happen if CO2-production (VCO2) increases during exercise?
If CO2-production (VCO2) increases during exercise, there will also be an increase in VA
V. Alveolar ventilation
5. What happen if we have twice as much VCO2?
If we have twice as much VCO2, our body will regulate to us having twice as much VA, and keep PACO2 constant (40mmHg)
-> Hypo/hyperventilation is based on pCO2-level in the alveoli
(PACO2 is always 40mmHg, even during exercise)
- Hypoventilation: PACO2 > 40mmHg (hypercapnia)
- Hyperventilation: PACO2 < 40mmHg (hypocapnia)
V. Alveolar ventilation
6. What is the value of PACO2 when there is hypoventilation?
Hypoventilation: PACO2 > 40mmHg (hypercapnia)
V. Alveolar ventilation
7. What is the value of PACO2 when there is Hyperventilation?
Hyperventilation: PACO2 < 40mmHg (hypocapnia)
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG - Retraction tendency
1A. What are the characteristics of Retraction tendency?
- The lung (covered with visceral pleura) is attached to the chest wall (covered with parietal pleura) with the pleural fluid between them
- During breathing, we do not move the lung, but the chest
-> lungs move with the chest
-> If we extend the chest, the lungs enlarge as well
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1B. Why are elastic fibers a reason for the retraction tendency?
- Acts like a spring, extending the alveoli
- Stretches when stress is applied -> allows for an increase in lung volume
- Recoil passively when this stress is released -> spontaneously shrink back to the original size
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1C. Why is surface tension a reason for the retraction tendency?
- The walls of the alveoli are covered by a fluid layer which is wet
- This fluid layer has a H2O-gas surface -> surface tension occurs
=> Surface tension reduces the surface -> reduces the alveoli and contributes to the retraction tendency
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1C1. How does surface tension occur?
Surface tension occurs due to the cohesion force of the H2O-molecules:
1. If we have a H2O-molecule inside the water, it has cohesion force with all surrounding molecules and the tension will be same in all direction = net effect is 0 (no surface tension)
- A H2O-molecule at the surface will have cohesion force with all the other H2O-molecules, but not with the air on the other side
-> cohesion force occurs only in 1 direction
-> this direction is to pull the H2O-molecules together = net effect is that the surface tension tries to reduce the surface
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1C2. How does surface tension try to make the alveolus smaller?
Surface tension gives the (cohesion)force, which tries to make the alveolus smaller
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1C3. how do we keep the alveoli open?
- In order to keep the alveoli open, we need to counteract the ‘’retraction tendency’’ with another force. It can be 2 kinds of forces:
1. Positive force from the inside of the alveoli
2. Negative force from the outside of the alveoli
=> What keeps the alveoli open in a normal respiratory system, is the negative force from the outside, because the pressure around the alveoli is negative
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1D. Why is the pressure negative?
- The retraction tendency of the lung moves the chest inside by pulling it inwards
- The chest will have an opposite (distension) tendency, which tries to counteract the retraction tendency of the lung by expanding
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
1D1. What happen to the lung In normal resting conditions?
- The lung is pulling inward
- The chest (wall) is pulling outward
=> The intrapleural pressure will be negative
=> Will provide the negative pressure/force around the alveoli, which counteracts the retraction tendency and keeps the alveoli open
VI. MECHANICAL PROPERTIES OF AIRWAYS, CHEST AND LUNG
2. What are the characteristic of Pneumothorax?
- If there is a puncture in the lung, air will enter the chest and will go to the intrapleural space -> lung compresses and collapses
- The reason for that, is that the fluid layer between the lung and chest wall is very wet -> the lung and chest move together due to this wet layer, and when air enters the intrapleural space, this common movement will not be possible any more
- Alveoli are the ones which have the retraction tendency -> makes the lung collapse, when we have a puncture (REMEMBER: lung compresses + chest expands)
V. Pressures in the respiratory system
1. What are the characteristics of pleural space?
Between the lungs and chest wall exists a pleural space -> 2 pleural layers are separated by fluid = a potential (virtual) space, with a negative pressure within
V. Pressures in the respiratory system
2. What are the 3 types of pressures you can find?
- Pressure inside the lung
- Pressure inside the pleural space
- Pressure outside the lung + chest
V. Pressures in the respiratory system
3. What are the characteristics of Pressure inside the lung?
Pressure inside the lung: alveolar (PA) or intrapulmonary (Ppulm) pressure
V. Pressures in the respiratory system
4. What are the characteristics of Pressure inside the pleural space?
Pressure inside the pleural space: intrapleural (Ppl), intrathoracic (PTH) or esophageal (Pesophageal) pressure
V. Pressures in the respiratory system
5. What are the characteristics of Pressure outside the lung + chest?
- Pressure outside the lung + chest: barometric (outer) pressure (PB)
V. Pressures in the respiratory system
6. What happen to pressures in in the respiratory system When we are not breathing?
When we are not breathing (between inhalation and exhalation), air is not moving, therefore:
- PB =PA -> PB =0,PA =0
V. Pressures in the respiratory system
7. What keeps the alveoli and lung open?
What keeps the alveoli and lung open, is the negative pressure of the pleural pressure:
- Ppl = -4 cmH2O (1 cmH2O = 0,7 mmHg)
- This negative pressure is created by the retraction tendency of the lung (explained!)
V. Pressures in the respiratory system
9A. What is Transmural pressure (PTM)?
Transmural pressure (Ptm) is the pressure difference between the alveolar pressure and pleural pressure:
- Ptm pressure inside (PA) – pressure outside (Ppl)
- PTM = 0– (-4cmH2O)
- PTM = + 4 cmH2O -> pressure which keeps alveoli open
V. Pressures in the respiratory system
9B. What are the important parameters of pressures in the respiratory system?
VI. Compliance of the lung
1. How is compliance of the lung measured?
Measured as how volume changes as a result of pressure change
VI. Compliance of the lung
4. Describe the Pressure-volume loop?
Compliance observed in the lung when filled with a liquid and a gas
=> Compliance = slope of the graph
=> Use slope at the level of FRC (functional residual capacity = resting state of respiratory system)
VI. Compliance of the lung
5. Is lung more compliant with fluid or gas?
Fluid
VI. Compliance of the lung
5A. Why is lung more compliant with fluid?
Lungs are more compliant with the fluid, something reduces the retraction force:
1. No surface tension, since all the nearby structures consist of fluid as well
2. No hysteresis (difference in inflation and deflation curves)
VI. Compliance of the lung
5B. Why is lung less compliant with gas?
The gas has lower compliance. Also, we have hysteresis here (explained later!)
VI. Compliance of the lung
6. What is the value of lung compliance?
C Lung = 0,2L/cmH2O (200mL/cmH2O)
VI. Compliance of the lung
7A. How can we measure compliance of the lung?
plethysmography
VI. Compliance of the lung
7B. How do we use plethysmography?
- Determine the FRC, and therefore the volume of the lung
- Determine the pressure by measuring the PTM (= PA-Ppl)
- PA measured by the tube in the plethysmograph, while Ppl is measured indirectly: Measure the Pesophageal instead, since Ppl = Pesophageal
=> Have all the values -> can construct a pressure-volume curve to measure the
compliance
VI. Compliance of the lung
8. How is compliance affected during pathological conditions?
The elasticity of the lung tissue is what affects the lung’s ability to inflate
VI. Compliance of the lung
8B. Characteristics of fibrosis
- A patient with fibrosis has less elastic fibers and therefore difficulty to expand the lungs
-> compliance ↓ (have to work harder to inflate) - Breathing will be more difficult for these patients
VI. Compliance of the lung
8C. Characteristics of Emphysema:
- A patient with emphysema will have ↑ compliance, because the walls of the lungs are more flexible -> easy to expand the lungs = NOT GOOD!
- Even in the resting state, the lung is already expanded
- There is little room to expand it if more breathing is needed (e.g. when exercising)
- Exhaling will require more effort
- Overall surface for gas exchange is small -> dynamic problems
VI. Compliance of the lung - Compliances of the chest and respiratory system
9. How is the compliance of the chest found?
- The compliance of the chest is found by the transmural pressure – difference between the inside pressure (pleural pressure) and the outside pressure (barometric pressure)
- PTM = Ppl - PB -> compliance of the chest (Cchest = 0,2 L/cmH2O)
VI. Compliance of the lung - Compliances of the chest and respiratory system
10. How is the compliance of the compliance of the whole respiratory system (lung + chest) found?
The compliance of the whole respiratory system (lung + chest) is also found by the transmural pressure – the difference between the inside pressure (alveolar pressure) and the outside pressure (barometric pressure)
- PTM = PA - PB => compliance of the respiratory system (Cresp.system = 0,1L/cmH2O)
=> Since the slope of the whole system is less steep than those of the lung and the chest, the compliance will also be lower than the compliances of the chest and lung
=>
VI. Compliance of the lung - Compliances of the chest and respiratory system
11. What limits the inhalation?
- If we increase the volume, the chest curve will be linear
=> Not limited there, because it can be further expanded - If we look at the curve of the lung, it becomes flat at high volume levels
=> Compliance of the lung limits inhalation
VI. Compliance of the lung - Compliances of the chest and respiratory system
11. What limits the inhalation?
- If we increase the volume, the chest curve will be linear
=> Not limited there, because it can be further expanded - If we look at the curve of the lung, it becomes flat at high volume levels
=> Compliance of the lung limits inhalation
VI. Compliance of the lung - Compliances of the chest and respiratory system
12. What limits the exhalation?
- If we look at the lung curve at the minimal volume (RV), it is pretty linear
-> Could be further decreased - The chest curve, on the other hand, becomes flat around (RV)
-> Compliance of the chest limits exhalation
VII. Surfactant
3. How does surfactant protect small alveoli from collapse?
- Surfactant reduces the surface tension (T↓)
- We can see that the pressure is inversely proportional to the radius, which means that the small alveoli (with a small radius) will have a higher pressure than the large alveoli (with a larger radius)
- The reduction of surface tension will be different in the 2 alveoli:
-> In the small alveolus, the surface is small (large in large alveolus), and if we have the same amount of surfactant in both alveoli; the concentration of the surfactant will be more concentrated in the small alveolus and more diluted in the large alveolus
VII. Surfactant
5A. What is hysteresis?
Hysteresis = difference in the curves of deflation and inflation (if we start from a fully collapsed state)
- Slope of deflation curve is more steep = large compliance
- Slope of inflation curve is less steep = smaller compliance
VII. Surfactant
5B. How is surfactant responsible for hysteresis?
- If we let the lung collapse fully, the surfactant (surface- active material) will move out and into micelles, due to the small surface
- If we then start to expand the lung, which has less surfactant, it will take more time/work, since the surface tension-reducing effect is decreased
=> Difficult to expand the lung (inhalation) - If the lung is fully expanded, the surfactants move back to the surface which makes the lung more compliant
=> Surface tension-reducing effect is increased => easier to deflate (exhalation)
