Physiology pt.2 Flashcards
(25 cards)
What does spirometer measure?
Measures the volume of air inspired and expired and therefore the change in lung volume
Tidal volume
Amount of air entering and leaving the lungs with each breath is the tidal volume
Normal tidal volume
During quiet respirations, the VT is ~500 mL
Total ventilation
The product of VT and the frequency of breaths is total ventilation, given in liters per minute
Lung volumes
Four primary volumes that do not overlap:
Tidal volume
- Inspiratory reserve volume
- Expiratory reserve volume
- Residual volume
Lung capacities
- Total lung capacity
- Inspiratory capacity
- Functional residual capacity
- Vital capacity
Inspiratory reserve volume
The amount of air that could be inspired with maximal effort above tidal volume
Factors that affect IRV
- Current lung volume (The greater the lung volume after inspiration, the smaller the IRV)
- Lung compliance (A decrease in compliance, a measure of how easy it is to inflate the lungs, will cause IRV to fall as well)
- Muscle strength (If the respiratory muscles are weak, or if their innervation is compromised, IRV will decrease)
- Comfort (Pain associated with injury or disease limits the desire or ability to make a maximal inspiratory effort)
- Flexibility of the skeleton (Joint stiffness, caused by diseases such as arthritis and kyphoscoliosis (i.e., curvature of the spine), reduces the maximal volume to which one can inflate the lungs
- Posture (IRV falls when a subject is in a recumbent position, because it is more difficult for the diaphragm to move the abdominal contents)
Recumbent position meaning
Laying on ones side horizontally
Expiratory reserve volume
The additional volume of air that one can expire after quiet expiration with a maximal effort
Factors that affect ERV
Same as those of IRV
Residual volume
The amount of air remaining in the lung after after maximal exhalation
Is it a design flaw for the lungs to contain air that they cannot exhale? Would it not be better for the lungs to exhale all their air and to collapse completely during a maximal expiration?
Total collapse would be detrimental for at least two reasons:
(1) After an airway collapses, an unusually high pressure is required to reinflate it. By minimizing airway collapse, the presence of an RV optimizes energy expenditure.
(2) Blood flow to the lungs and other parts of the body is continuous, even though ventilation is episodic. Thus, even after a maximal expiratory effort, the RV allows a continuous exchange of gases between mixed-venous blood and alveolar air. If the RV were extremely low, the composition of blood leaving the lungs would oscillate widely between a high pO2 at the peak of inspiration and a low pO2 at the nadir of expiration
Lung capacities
The lung capacities are various combinations of these four primary volumes:
- Total lung capacity TLC
- Functional residual capacity (FRC)
- Inspiratory capacity (IC)
- Vital capacity (VC)
TLC
Sum of all four volumes
IC
- Sum of IRV and TV
- After a quiet expiration, the IC is the maximal amount of air that one could still inspire.
FRC
The sum of ERV and RV and is the amount of air remaining inside the respiratory system after a quiet expiration
VC
- The sum of IRV, TV, and ERV
- In other words, VC is the maximal achievable TV
Factors that affect VC
Same as those that affect IRV and ERV
FEV1
volume of air exhaled in 1 second after maximal inspiratory effort
Normal FEV1
~80% of VC in healthy young adults
Factors that affect FEV1
Depends on all factors that affect VC as well as on airway resistance
Dead space in lungs
Dead space is the volume of the airways and lungs that does not participate in gas exchange
Types of dead space in lungs
- Anatomic dead space is the volume of conducting airways
- Physiologic dead space includes the anatomic dead space plus those regions of the respiratory zone that do not participate in gas exchange
