Lecture 2: Pulmonary Physiology (Ventilation) Flashcards
What is Pulmonary Function Testing (PFT)?
Testing done to measure the effectiveness of the lungs (e.g. Spirometry)
List the (4) reasons why Pulmonary Function Testing (PFT) is an important part of clinical medicine
- Establish the diagnosis of pulmonary disease and assesses its severity (restrictive vs obstructive)
- Documents the effectiveness of therapy (e.g. use of brochodilators for asthma)
- Charts the course of pulmonary disease
- Educates patients & (hopefully) facilitates changes in lifestyle (e.g. quit smoking)
Define Spirometry
- Spirometry is a simple test used to help diagnose and monitor certain lung conditions
- It’s carried out using a device called a spirometer
What do spirometers measure? Give examples.
- Measure volume of gas the lungs inhale or exhale as a function of time to evalute pulmonary function and fitness
- e.g., change in lung volume and flow rate of spontaneous breathing
- e.g., forced breathing maneuvers that evaluate pulmonary function
Shows flow rate
The graph below is a trace reading form a spirometer. Define:
- TLC
- FRC
- ERV
- IRV
- FVC
- IC
- RV
- V(T)
- VC
- TLC: Total Lung Capacity
- FRC: Functional Residual Capacity
- ERV: Expiratory Reserve Volume
- IRV: Inspiratory Reserve Volume
- FVC: Forced Vital Capacity
- IC: Inspiratory Capacity
- RV: Residual Volume (cannot be measured via spirometry)
- V(T): Tidal Volume
- VC: Vital Capacity
TLC is
Total Lung Capacity: the total amount of air in the lungs
FRC is
- Functional Residual Capacity: Eupnea breathing
- The volume remaining in the lungs after a normal, passive exhalation
ERV is
- Expiratory Residual Volume: the volume of air that can be forcefully exhaled after a normal resting expiration, leaving only the RV in the lungs
- Can increase expiratory volume during forced expiration
IRV is
- Inspiratory Residual Volume: the additional volume of air that can be inspired at the end of a normal inspiration
- Can increase inspiratory volume during forced inspiration
FVC is
Forced Vital Capacity: the total volume of air that can be exhaled during a maximal forced expiration effort
IC is
The maximal amount of air that can be inspired
RV is
- The amount of air that remains in a person’s lungs after fully exhaling
- CANNOT be measured by spirometry
V(T) is
The amount of air that can be inhaled or exhaled during one respiratory cycle
VC is
- The maximal volume of air that can be expired following maximum inspiration
- A FVC maneuver is need to get VC
Which 4 volumes of TLC do NOT overlap?
- V(T)
- IRV
- ERV
- RV
Using the graph below explain the important of IRV and ERV during active breathing?
- During active breathing (e.g. exercise) we need more air so we can draw on our inspiratory reserve volume (IRV) and expiratory reserve volume (ERV) to increase tidal volume (VT)
- ↑V(T)= ↓ERV + ↓IRV
What are the average volumes of the 4 non-overlapping subdivisions of TLC
Also known as the 4 Primary Lung Volumes
- Tidal Volume (VT): ~500 ml
- Inspiratory reserve volume (IRV):~2500 ml
- Expiratory reserve volume (ERV): ~1500 ml
- Residual volume (RV): ~1500 ml
Which of the 4 primary lung volumes (non-overlapping subdivisions) can not be measure via spirometry?
RV
What are lung capacities (compartments)?
Compartments that consist of 2 or more primart lung volumes
What are the 4 major lung capacities?
- IC: Inspiratory Capacity
- FRC: Functional Residual Capacity
- VC: Vital Capacity
- TLC: Total Lung Capacity
What is the equation for Inspiratory Capacity (IC)?
HIGH yield
- IC=V(T) + IRV; ~3L
- V(T): Tidal volume
- IRV: Inspiratory Reserve Volume
What is the equation for Functional residual capacity (FRC)?
HIGH yield
- FRC=ERV+RV; ~3L
- ERV: Expiratory Reserve Volume
- RV: Residual Volume
What is the equation for Vital Capacity (VC)?
HIGH yield
- VC=IRV+V(T)+ERV
- IRV: Inspiratory Reserve Volume
- V(T): Tidal Volume
- ERV: Expiratory Reserve Volume
What are the (3) equations for Total Lung Capacity (TLC)?
- TLC=IC+FRC
- TLC=VC+RV
- TLC=IRV+V(T)+ERV+RV; ~6L
- IC:Inspiratory Capacity
- FRC: Functional residual capacity
- VC:Vital Capacity
- RV: Residual Volume
- IRV:Inspiratory Reserve Volume
- V(T): Tidal Volume
- ERV: Expiratory Reserve Volume
Which of the 4 lung capacities can NOT be measured via spirometery?
- FRC, b/c the FRC equation (FRC=ERV+RV) includes RV which cannot be measured by a spirometer
The same does NOT apply to TLC even though an equation includes RV. This is b/c there are multiple ways to measure TLC
What is the indirect method for measuring FRC?
Closed-circuit helium (He) dilution method
List the steps (protocol) for the Closed-circuit He dilution method
- Spirometer filled with 10% He (balance room air)
- Subject breathes room air
- Close the valve @ FRC (=midposition) and start breathing the He mixture in the spirometer.
- After several breaths the He gas mixture will equilibrate between your patient’s lungs, which contains a volume of gas that is FRC, and the spirometer
What are the equations used to measure FRC in the closed-circuit He dilution method?
- C1xV1 (amount of He prior to equilibration) =C2(V1+V2) (amount of He after equlibration)
- C1: fractional concentration of He before opening the valve
- V1: volume of gas mixture in spirometer
- C2: [He]spirometer (which also=[He] lungs)
- V2= FRC
What is the equation that helps you solve for FRC (V2) in the closed-circuit He dilution method?
HIGH yield
- V2=FRC= [V1(C1-C2)]/C2
- C1: fractional concentration of He before opening the valve
- V1: volume of gas mixture in spirometer
- C2: [He]spirometer (which also=[He] lungs)
How can you solve for RV (resdiual volume) using the closed-circuit helium dilution method?
- Use the Closed-circuit He dilution method to solve for FRC
- Use spirometry to solve for ERV (expiratory residual volume)
- RV= FRC-ERV
What equation helps you solve for RV (residual volume)?
HIGH yield
RV=FRC-ERV
What are other indirect methods for measuring for FRC,RV, and TLC?
- Open-circuit N2 washout method
- Body plethysomography
Why is important to measure RV?
RV increases with obstructive lung diseases and decreases with restrictive lung diseases
Explain the main characteristics of Obstructive Lung Disease
- Increases airway resistance (↑Raw)
- Increases resistance to airflow
- Decreases ventilation
- Specific problem areas: Zones 0-7 (↑↑↑ Raw)
- Airflow is limited during expiration
Explain the main characteristics of Restrictive Lung Disease
- Decreases Lung-Chest wall (L-CW) compliance
- Respiratory muscles are weak
- Loss of neural drive
- Lungs are too stiff
Explain the main characteristic of Interstitial Lung Disease
- Diffusion impairment
- Increases capillary thickness
List (4) examples of Obstructive Lung Diseases
- Asthma
- Chronic Bronchitis
- Emphysema
- Cystic Fibrosis
Explain Asthma
Spasmodic contraction of smooth muscle in the bronchi
Explain Chronic Bronchitis
- An inflammatory condition of the bronchi, which results in the excessive production of mucus
- Pure chronic bronchitis=COPD
COPD=chronic obstructive pulmonary disease
Explain Emphysema
- Loss of lung recoil
- Pure emphysema=COPD
A mixture of what two diseases can cause COPD?
Chronic bronchitis and emphysema
Explain Cystic Fibrosis
- Viscous mucus in the airways with impaired muco-cillary clearance
- Recurring respiratory infections destroy the cellular constituents of the airway resulting in irreversible obstruction to airflow
Which of the diseases is reversible and why?
- Chronic Asthma
- Bronchitis
- Emphysema
Chronic Asthma, b/c there is no alvelor damage