Pulmonary 2 Flashcards
(41 cards)
What is the alveolar pressure during:
- Inspiration
- Expiration
- how does air flow?
- Alveolar Pressure is BELOW atmospheric (so negative pressure pulls air in)
- Alveolar Pressure is ABOVE atmospheric
Air flows down a pressure gradient
- so during inspiration it is pulled in, expiration it flows out
What is the relationship of Pressure and Volume?
Pressure is INVERSELY proportional to volume
Ex: as the volume of a container decreases, the pressure rises
What are the 2 major muscles of INSPIRATION?
- Diaphragm
- External Intercostals
Diaphragm flattens & moves DOWN: enlarge cavity VERTICALLY
External Intercostals: move UP and OUTWARD –> enlarge cavity in lateral & anterior-posterior direction
(they relax after inspiration is complete & rib cage falls)
What muscles are used for FORCED inspiration?
Accessory Muscles of Inspiration:
- Scaleneus
- SCM
By what mechanism do we EXPIRE? (passive or active)
What muscles are used for FORCED ACTIVE Expiration?
PASSIVE!
Abdominal muscles contract –> increase abdominal pressure and pushes diaphragm UP
Internal Intercostal Muscles flatten rib cage & pull ribs DOWN & INWARD
What are the only lung volumes that a spirometer cannot measure? What is another technique to measure this?
- RV, FRC, TLC
- Helium Dilution
- more dilution = larger capacity
What are the volumes of the following:
- Tidal Volume (Vt)
- Inspiratory Reserve Volume (IRV)
- Expiratory Reserve Volume (ERV)
- Residual Volume (RV)
- 500 mL
- 3000 mL
- 1200 mL
- 1200 mL
What is the following defined as:
- Change in volume that occurs with cycle breathing
- Volumes that can be in/exhaled in addition to the TIDAL VOLUME
- Volume that remains in the lung even after forced expiration
- Tidal Volume
- Inspratory/Expiratory Reserve
- Residual Volume (cannot be measured with spirometry)
What are the equations for the following:
- Inspiratory Capacity
- Functional Residual Capacity
- Vital Capacity
- Total Lung Capacity
- IC = IRV + Vt –> 3500 mL
- FRC = ERV + RV –> 2400 mL
- VC = IRV + Vt + ERV –> 4600mL
- TLC = IRV + Vt+ ERV + RV
- -> 5800 mL
What is the term for the maximum amount of air that can be moved from deep expiration to deep inspiration?
Vital Capacity
Define:
FRC
TLC
What is unique about these in terms of the spirometer?
FRC = Volume of air in the lungs when all respiratory muscles are relaxed
(lung pulls in, chest wall springs out)
TLC:
total volume of air held by the lung
- includes Alveolar Volume & Dead space volume
- scaled to the size of a person
-**cannot be measured with spirometer! **
What does Helium Dilution measure?
Measures the FRC ( the volume of air in lungs when all muscles are relaxed)
-patient relaxes to FRC volume and a valve is opened allowing helium during inhalation/exhalation
FRC = V1 * (C1-C2) / C2
What does a larger FRC signify?
Larger FRC = the more the initial helium concentration gets diluted
(dilution principle)
What are 2 ways to measure FRC?
- Helium Dilution
2. Body Plethysmography
What is compliance of the lung defined as? What does it measure?
Ability of any structure to comply with deforming forces
- measures the elastic properties of the lung
change in lung volume/ per 1 cm of H2o in distending pressure
What does lung compliance depend on? When is compliance maximized?
VOLUME of air within the lung
- volumes near FRC = compliance is maximized!
(compliance decreases at higher volumes)
What is hysteresis? What causes hysteresis?
Hysteresis: inflation of the lung has a different curve than deflation of the lung (inspiration/expiration)
- Surfactant causes Hysteresis
When are external intercostals & Accessory Muscles used?
DURING EXERCISE ( for inspiration)
- Internal intercostals = used for forced EXPIRATION
When is compliance maximal? What is the equation for compliance?
Max at MIDDLE RANGE of pressures
- compliance is the change in pressure in going from FRC to FRC +1
What is Specific Lung Compliance?
Absolute compliance depends on the volume of the structure
ex: child lung vs. adult lung
Compliance is tissue specific based on the VOLUME being evaluated
SC = Lung compliance/ lung volume
(compliance = volume/pressure)
How does the specific compliance change if half of a lung is removed (for example)?
The total complaince of the lung is less, BUT the specific compliance does NOT change!
- since it is a measure of compliance/volume
What 2 properties does inflation of the lung overcome?
- Viscoelastic properties of lung parenchyma by stretching elastic & collagen fibers
- Surface tension of alveolar epithelium set up between air/water interface (surfactant reduces tension, but not to zero)
What are the affects of Fibrosis & Emphysema on Compliance?
Fibrosis - Compliance Decreases
Emphysema - Compliance Increases(greater slope)
- alveoli expand in diamter, but decrease in SA
What are the affects of Fibrosis & Emphysema on FRC?
Fibrosis - FRC DECREASES
- more lung recoil
- intrapleural pressure becomes more negative (more pull of the lung = increase volume)
Emphysema - FRC INCREASES
- less lung recoil
- intrapleural space less negative (less pull of the lung on the chest wall)
