Respiratory Cycle and Lung Volumes Flashcards
______ ______ = volume inspired or expired with each normal breath
Tidal volume
How do you calculate minute ventilation rate?
Tidal volume x breaths/min
How do you calculate minute alveolar ventilation rate?
(Tidal volume - dead space) x breaths/min
Describe the relationship of air flow to the pressure difference between the mouth and the alveoli
Air flow is driven by and is directly proportional to the pressure difference between the mouth and the alveoli
What is the relationship of alveolar pressure and atmospheric pressure at rest?
Alveolar pressure = atmospheric pressure
[because the lung pressures are expressed relative to atmospheric pressure, the alveolar pressure is said to be 0]
What is the relative value of intrapleural pressure at rest?
Negative
[opposing forces of the lungs trying to collapse and the chest wall trying to expand creates a negative pressure in the intrapleural space between them]
A balloon catheter placed in the esophagus would measure what type of pressure?
Intrapleural pressure
What lung capacity value represents lung volume at rest (prior to inspiration)?
Functional residual capacity
During inspiration, inspiratory muscles contract and cause the volume of the thorax to increase. As the lung volume increases, what happens to alveolar pressure? What is the result?
Decreases to less than atmospheric pressure (becomes negative)
Pressure gradient between atm and alveoli now causes air to flow into the lungs; air flow will continue until the pressure gradient dissipates
What changes occur to intrapleural pressure during inspiration?
Becomes more negative because the elastic recoil strength of the lungs increases as lung volume increases
Changes in intrapleural pressure during inspiration are used to measure the dynamic _______ of the lungs
Compliance
How is lung volume calculated at the peak of inspiration?
Functional reserve capacity + one tidal volume
What changes occur with alveolar pressure during expiration? What does this lead to?
Alveolar pressure becomes greater than atm (becomes positive) because alveolar gas is compressed by the elastic forces of the lung
Since alveolar pressure is now higher than atmospheric pressure, the pressure gradient is reversed and air will flow out of the lungs
What changes occur with intrapleural pressure during normal, passive expiration?
Intrapleural pressure returns to its resting value during a normal passive expiration
What occurs with intrapleural pressure during forced expiration?
Intrapleural pressure becomes more positive, which compresses the airways and makes expiration more difficult [this occurs in COPD patients]
How might a COPD patient compensate for the collapse of the airways that occurs with forced expiration?
They exhale slowly with pursed lips
What is the most important muscle of inspiration? How does it work?
Diaphragm
When the diaphragm contracts, the abdominal contents are pushed down and the ribs are lifted upward and outward, increasing the volume of the thoracic cavity
What muscles of inspiration are not used during normal, quiet breathing? When are they used?
External intercostals
Accessory muscles
Used during exercise and in diseases causing respiratory distress
Expiration is normally a passive process, so expiratory muscles are only used during exercise or when airway resistance is increased due to things like asthma.
What are considered the expiratory muscles?
Abdominal muscles
Internal intercostal mm.
Abdominal muscles may be used in forced expiration, what is their action?
Compress the abdominal cavity, push the diaphragm up, and push air out of the lungs
Internal intercostals may be used in forced expiration, what is their action?
Pull the ribs down and in
Using a capital A, such as with partial pressure of oxygen: PAO2, what does the “A” indicate?
Alveolar gas
Using a lowercase “a” such as with partial pressure of oxygen: PaO2, what does the “a” indicate?
Arterial gas
What do we expect the relationship to be between the partial pressure of alveolar gas (PAO2) and the partial pressure of arterial gas (PaO2)?
They should be the same
What relationship is described by Boyle’s Law?
Pressure of a gas is inversely proportional to its volume
[P1V1 = P2V2]
Based on Boyle’s Law, an increase in lung volume corresponds with a _______ in pressure, and air will _____ the lung.
Decrease; enter
What kind of muscle(s) are/is the inspiratory muscles?
A. Smooth muscle
B. Skeletal muscle
C. Cardiac muscle
D. A and B
B. Skeletal muscle
What units are utilized in the measurement of pressures in respiratory physiology?
A. mm Hg
B. cm Hg
C. mm H2O
D. cm H2O
D. cm H2O
[note that we normalize atmospheric pressure to 0 cm H2O]
What is the intrapleural pressure at rest? How does it change during inspiration?
About -5 cm H2O
During inspiration, volume increases and intrapleural presure decreases to near -8 cm H2O
As the thoracic cavity increases in size during inspiration, alveolar pressure (pressure within the alveoli) _________, which causes air to ______ the lungs
Decreases; enter
At rest, alveolar pressure = _____ cm H2O
At the end of inspiration, alveolar pressure = ____ cm H2O
This is due to _______ in alveolar size
0
-1
Increase
As the thoracic cavity increases in size with inspiration, pleural pressure (pressure within the pleural spaces _________
Decreases
[starts negative, gets more negative]
T/F: transpulmonary pressure should always be negative
False: The transpulmonary pressure should always be positive because the pleural pressure should always be negative, so subtracting a negative will give you a positive.
How is transpulmonary pressure calculated?
Transpulmonary pressure = alveolar pressure - pleural pressure
What is the transpulmonary pressure at rest?
5 cm H2O at rest
Alveolar pressure increases during expiration due to recoil of the lungs, what does it increase to by mid-expiration?
+1 cm H2O
What is the transpulmonary pressure at the following points in the respiratory cycle?
- Rest
- Mid-inspiration
- End-inspiration
- Mid-expiration
- Rest = +5 cm H2O
- Mid-inspiration = +5.5 cm H2O
- End-inspiration = +8 cm H2O
- Mid-expiration = +7.5 cm H2O
_______ ________ = refers to the volume of air inhaled every minute
Minute ventilation
A patient’s respiratory volume is 14 breaths/minute (RR) and tidal volume is 500 mL per breath.
What is their minute ventilation?
7000 mL/min = 7 L/min
[this is the accepted normal value!]
At the end of inspiration, what would pleural pressure be?
A. 0 cm H2O B. -5 cm H2O C. -8 cm H2O D. +5 cm H2O E. +8 cm H2O
C. -8 cm H2O
Air flow into the lungs at the end of inspiration would be which of the following?
A. +1 L/s
B. 0 L/s
C. -1 L/s
D. -8 L/s
B. 0 L/s
What would be the flow rate during a forced expiration?
A. +2 L/s B. 0 L/s C. -2 L/s D. -1 L/s E. +1 L/s
A. +2 L/s
Transpulmonary pressure in the middle of inspiration would be which of the following?
A. +5 cm H2O B. +5.5 cm H2O C. +8 cm H2O D. -5.5 cm H2O E. -8 cm H2O
B. +5.5 cm H2O
The 2 respiratory zones are the conducting zone (no gas exchange) and respiratory zone (gas exchange). In which zone would you find the most smooth muscle?
Conducting zone; important for dilating/constricting bronchioles
What structures make up the key component of the respiratory zone?
Alveoli
What is one of the more common tools for measuring respiratory volumes?
Spirometer
What volumes and capacities cannot be measured by a spirometer?
Residual volume (RV)
Functional Residual Capacity (FRC)
Total Lung Capacity (TLC)
Normal respiration consists of what 4 respiratory volumes?
Tidal volume
Inspiratory reserve volume
Expiratory reserve volume
Residual volume
Since residual volume cannot be measured by spirometry, what method (besides estimation) can be used to measure RV more precisely?
Helium dilution method
________ are the sum of 2+ different combinations of respiratory volumes together
Capacities
What factors influence respiratory capacity?
Size
Gender
Age
Disease state
What are the 4 respiratory capacities that can be calculated based on the different respiratory volumes?
Vital capacity (VC)
Inspiratory capacity (IC)
Functional Residual Capacity (FRC)
Total Lung Capacity (TLC)
What volume is used as a diagnostic tool and is a measure of how much air is blown out in the first second of forced expiration?
Forced Expiratory Volume in 1 sec (FEV1)
_____% is a normal FEV1
A _______ in FEV1 would likely indicate obstructive respiratory disease
A ______ in FEV1 would likely indicate retrictive respiratory disease
80
Decrease
Increase
_______respiratory diseases are considered diseases of the airways resulting in reduced air flow
Obstructive
Which of the following is characteristic of obstructive lung disease?
A. Reduced lung volume; difficulty exhaling
B. Reduced lung volume; difficulty inhaling
C. Reduced air flow; difficulty inhaling
D. Reduced air flow; difficulty exhaling
D. Reduced air flow; difficulty exhaling
_______ respiratory diseases are characterized by reduced expansion of lung parenchyma and decreased total lung capacity
Restrictive
Which of the following is characteristic of restrictive lung disease?
A. Reduced lung volume; difficulty exhaling
B. Reduced lung volume; difficulty inhaling
C. Reduced air flow; difficulty inhaling
D. Reduced air flow; difficulty exhaling
B. Reduced lung volume; difficulty inhaling
What type of respiratory disease is characterized by a reduced FEV1 and a decrease in the FEV1:FVC ratio?
Obstructive
What type of respiratory disease is characterized by a reduction in both FEV1 and FVC, leaving the FEV1:FVC ratio either unchanged or elevated?
Restrictive
What changes occur to residual volume and inspiratory reserve volume in obstructive disease?
RV increases
IRV decreases
______ _____ = regions of the lung that receive air but not blood, so no gas exchange takes place
Dead space
What are the 3 types of dead space?
Anatomic
Physiological
Alveolar (subtype of physiologic)
_________ dead space refers to space in the respiratory system other than alveoli
Anatomic
_______ dead space refers to alveoli that receive air but not blood
Alveolar
__________ dead space is basically alveolar dead space, meaning alveoli that receive air but not blood - so no gas exchange can occur
Physiologic
In healthy individuals, what do you expect their physiological dead space to be?
Nearly zero
At what point in the respiratory cycle does anatomical dead space air enter the lungs?
At the end of inspiration
[this is the air that was left in the lungs at the end of previous expiration]
How is anatomical dead space calculated?
It is typically estimated based on person’s weight
For example: 150 lb person = 150 mL of anatomic dead space
How is physiologic dead space calculated?
(Arterial PCO2 - expiratory PCO2)/arterial PCO2
How is minute alveolar ventilation calculated?
(Tidal volume - dead space) x frequency
A 150 lb patient is breathing 12 breaths/minute. What is their minute alveolar ventilation rate?
4200 mL/min
4.2 L/min
A 200 lb person is breathing 20 breaths/min with a tidal volume of 750 mL. What is the minute ventilation rate?
15,000 mL/min
[15 L/min]
A 200 lb person is breathing 20 breaths/min with a tidal volume of 750 mL. Minute ventilation rate is 15,000 mL/min. What is their minute alveolar ventilation rate?
11,000 mL/min
[11,000 L/min]
A 67 y/o patient (6’2”, 197 lbs) has been hospitalized with COPD. He is artificially ventilated at a respiratory rate of 23 breaths/min and a tidal volume of 900 mL. Total anatomical and physiological dead space has been calculated to be 300 mL. What is his alveolar ventilation?
A. 17,600 mL/min
B. 11,000 mL/min
C. 13,800 mL/min
D. 6,600 mL/min
C. 13,800 mL/min
Which respiratory volume is the volume that can be inspired over and above the tidal volume?
Inspiratory reserve volume (IRV)
[used during exercise]
Which respiratory volume is the volume that can be expired after the expiration of a tidal volume?
Expiratory reserve volume (ERV)
Which respiratory volume is the volume that remains in the lungs after a maximal expiration?
Residual volume
How is inspiratory capacity calculated?
Tidal volume + Inspiratory Reserve Volume (IRV)
How is functional residual capacity calculated?
Expiratory Reserve Volume (ERV) + Residual Volume (RV)
______ ______ capacity = volume remaining in lungs after a tidal volume is expired
Functional residual
Spirometery is a commonly used clinical method of measuring a person’s functional residual capacity
False: FRC is calculated using residual volume, which cannot be measured by spirometry
_____ capacity = volume of air that can be forcibly expired after a maximal inspiration
Vital
How is vital capacity calculated?
Tidal volume + Inspiratory Reserve Volume + Expiratory Reserve Volume
[can also do inspiratory capacity + expiratory reserve volume]
What capacity represents the volume in the lungs after a maximal inspiration?
Total lung capacity (TLC)
How is total lung capacity calculated?
It is the sum of all 4 lung volumes
Can be calculated by taking Vital Capacity + Residual Volume
OR: Inspiratory capacity + Functional Residual Capacity
