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
Which of the diseases is NOT reversible and why?
- Chronic Asthma
- Bronchitis
- Emphysema
Emphysema, b/c alvelor damage occurs
Which of the diseases has the most mucus production?
- Chronic Asthma
- Bronchitis
- Emphysema
Bronchitis
What equation can be used to diagnosis if a patient has an obstructive lung disease?
- (FEV1/FVC)x100= FEV%
- FEV1=forced expiratory volume in 1 second
- FVC=Forced Vital Capacity
(FEV3/FVC)x100 is another equation used but not as important
What is the FEV% in a normal patient?
FEV% of FEV1 should be >70% of FVC
FEV% of FEV3 should be >95% of FVC (not as important)
If measured values are less than >70% of FVC (FEV) it is indicative of what type of disease?
Obstructive Lung Disease
The greater the obstruction (i.e. increased Raw) the _________ the FEV%.
lower
What is another unit that can be measured to determine what lung disease a patient has?
Low yield
Forced Expired Flow (FEF): normal range between. 25-75%
In addition to decreased expiratory flow (FEV% or FEF 25-75%) what are other (5) features are present with Emphysema (obstructive lung disease)?
- Increased compliance of the respiratory system d/t increased compliance of the lungs
- Increases TLC, which is seen as hyperinflation on a chest roentgenogram
- Loss of peripheral vascular elements on chest roentgenogram d/t loss of alveolar tissue
- Decreased static recoil of the lung
- Decreased pulmonary diffusing capacity, D(L) (D(L)=conduction of the alveolar-capillary membrane for gas; e.g., DLO2)
roentgenogram-an X-ray photograph
What is the reason for increased residual volume (RV) with COPD?
Dynamic compression (the pressure that keeps alveoli open decreases which causes premature airway collapse)
List (4) features present with Chronic Bronchitis (OLD)
OLD:Obstructive Lung Disease
- Airway resistance without loss of alveolar tissue
- TLC is usually normal
- Static compliance curve and recoil pressure are normal
- Decreased FEV% due to increased Raw
List features present in asthma (OLD) during an attack
- Maxium Expiratory flows are reduced (↓FEV% and ↓FEF25-75%)
- TLC, FRC, & RV are increased
- ↑RV d/t ↑smooth muscle tone, edema, inflammation of airway walls and abnormal secretions
- ↑TLC and ↑FRC are not well understood; accessory muscles are active
Below is a flow loop graph comparing a normal lung to dieased lungs. Explain that happens to TLC and RV with:
- Airway obstruction
- Pulmonary fibrosis
- Airway obstruction: ↑RV and ↑TLC b/c premature dynamic compression which causes ↓ V-dot (ventilaton)-airway collapses early
- Pulmonary fibrosis: ↓RV and ↓TLC but V-dot (ventilation) stays the same b/c disease is not affecting dynamic compression-nothing is obstructing the airways
What is the goal of ventilation?
To supply the O2 needed by the body and removes CO2
How does gas move in the body?
Because of differences in partial pressures
Explain Dalton’s Law of partial pressure?
- The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases
- Ptotal=Px+Py+Pz
What is the equation for total pressure (Patm)?
Patm=P(B)=P(O2)+P(N2)+Pother
How do you calculate partial pressure of O2?
- PO2=PB x FO2 (atm)
- 160mm Hg=760 mmHg x 0.21
- 0.21 ATA O2=1 ATA x 0.21
What is the equation used to calculate the partial pressure of a dry gas?
Pgas=Fgas x PATM
At sea level 1 atm= ________ mmHg and _______ cm H2O
- 760 mmHg
- 1033 cm H2O
What is the partial pressure of N2? How is it calculated?
- PN2=600.4 mmHg
- 0.79 x 760 mmHg
- (PN2=Fgas x PATM)
What is the partial pressure of O2? How is it calculated?
- PO2= 159.0 mmHg
- 0.209 x 760 mmHg
- (PO2=Fgas x PATM)
What is the partial pressure of CO2? How is it calculated?
- PCO2=0.3 mmHg
- 0.0004 x 760 mmHg
- (PCO2= Fgas x PATM)
Partial pressure for CO2 is basically 0
Using the image below explain the partial pressure changes (O2&CO2) from the Atmosphere to Alveolar
- O2: 160 mmHg drops to 100 mmHg b/c the addition of water vapor pressure (47 mmHg) and gases from FRC
- CO2: 0 mmHg increases to 40 mmHg b/c its being picked up from blood
Using the image below explain the partial pressure changes (O2&CO2) from the End Pulmoary Capillary to Systemic Arterial
- O2: 100 mmHg drops to 90 mmHg b/c oxygen feeds the bronchioles
- CO2: stays 40 mmHg b/c it’s easily dissolved
Using the image below explain the partial pressure changes (O2&CO2) from the Systemic Arterial to Tissue
- O2: 90 mmHg drops to 40 mmHg b/c oxygen feeds the tissue
CO2: 40 mmHg increases to 46 mmHg b/c deoxygenated blood increases
Explained what the partial pressures of O2 and CO2 is at the Mixed Venous stage
- O2: 40 mmHg
- CO2: 46 mmHg
- In the veins oxygen levels are low and CO2 levels are high
Using the graph below explain ventilation rate (V-dot), PO2, PCO2, and Arterial pH during light-moderate excercise
- V-dot (L/min): Maintain homeostasis by increasing ventilation
- PO2: consuming more O2 but constant rate
- PCO2: producing more CO2 but constant rate
- Arterial pH: follows [CO2] b/c bicarb. buffer
Using the graph below explain ventilation rate (V-dot), PO2, PCO2, and Arterial pH during anaerobic exercise
- V-dot (L/min): Ventilation increases dramatically
- PO2: consuming more O2
- PCO2: blows off more CO2 , breathing higher level than what regulates CO2 (hyperventaling)
- Arterial pH: drops d/t production of lactic acid
___________ is regulated to match ___ consumption and _______ production
Ventilation, O2, CO2
During Inspiration, why is PO2 increased and PCO2 decreased.
Breathing in O2 into the lungs which decreases the amount of CO2
During Expiration, why is PO2 decreased and PCO2 increased.
- ↓ O2 b/c of breathing out and absorption in blood
- ↑ CO2 d/t still moving CO2 out the body
During Breath Holding, why is PO2 decreasing and PCO2 increasing
- ↓O2 b/c gas exchange
- ↑ CO2 accumulation b/c circulation still occuring
Define Minute Ventilation
Amount of air inspired or expired per min
What is the equation of Minute Ventilation
- V-dot= VT x fresp
- Minute ventilation (ml/min)= tidal volume (ml/breath-size of breaths) x resp. frequency (breaths/min-# of breaths)
What are the (3) different ways to show minute ventilation
V-dot(min); V-dot(E); V-dot(I)
I: inspiration, E:Expiration
What is Alveolar Ventilation?
The amount of atmospheric air inspired per minute that reaches the alveoli and participate in gas exchange
True or False. All inspired gas reaches the alveolar gas compartment
FALSE, some remains in the airways (conducting zone)
What is the equation for Alveolar Ventilation calculation?
- Alveolar Ventilation: V-dot(A)= (VT-VD) x f
- VT=tidal volume
- VD=dead space (air in the conducting zone)
- f= resp. frequency
What is the equation to find tidal volume using dead space and alveolar ventilation?
V(T)= V(D) + V(A)
What is the equation to find tidal volume and resp. frequency using dead space and alveolar ventilation?
V(T) x fresp= V(D) x fresp. + V(A) x fresp.
What is the equation to find minute ventilation (E) using dead space and alveolar ventilation?
V-dot (E)= V-dot (D) + V-dot (A)
What happens to alveolar O2 and CO2 if alveolar ventilation is increased?
- ↑ O2, ↓CO2
- b/c ↑ ventilation increases gas exchange
What would occur to O2 and CO2 in the blood and tissues if ventilation increased?
- ↑ O2, ↓CO2
- b/c ↑ ventilation increases blood gas exchange
Explain the relationship between alveolar ventilation and PCO2 and PO2 using the graph below
- When PCO2 increases, V-dot(A) decreases and vice versa
- (↑PCO2=↓V-dot(A), ↓PCO2=↑V-dot(A))
- When PO2 increases, V-dot (A) increases and vice versa
- (↑CO2=↑V-dot(A), ↓CO2=↓V-dot (A))
When are the terms hyperventilation and hypoventilation used in medicine?
To refer to the state of overall ventilation in relation to CO2 production by the tissues
How is the hyperventilation and hypoventilation relationship determined?
By measuring systemic arterial PCO2
What does hyper- and hypoventilation NOT refer to?
- The rate or depth of breathing
- The patients effort to breathe
In Normal lungs, Hyperventilation has a _________ rate of CO2 and ________rate of O2
- Decreased rate of CO2
- Increased rate of O2
Also termed Alkalosis
In Normal lungs, Hypoventilation has a _________ rate of CO2 and ________rate of O2
- Increased rate of CO2
- Decreased rate of O2
Also termed Acidosis
Systemic arterial PO2 can NOT be used as indicator of hyper or hypoventilation in patients with _________________.
Lung dysfunction
In patients with lung diseases, what is the rate of CO2 and O2?
Decreased CO2, and Decreased O2
Define Hyperventilation
An increase in alveolar ventilation out of proportion to metabolism (V-dot CO2) which results in lowering PA(CO2)
Define Hypoventilation
A disproportionate decrease in alveolar ventilation relative to VCO2 leads to an increase in PA(CO2)
Define Hyperpnea
When VCO2 is proportional to the increase in VA, PaCO2 remains unchanged
VA: Alveolar Ventilation
Define Physiological (respiratory) Dead Space
Areas of the lungs that are ventilated where no gas exchange occurs (or where ventilation exceeds blood flow)
What are the 2 areas of Physiological Dead Space?
- Anatonomic Dead Space (Conducting Zone)
- Alveolar Dead Space
What is (are) TRUE concerning partial pressures?
a. The first 150 ml of expired air CO2 is normally the same as alveolar air CO2
b. At the end of expiration, anatomic dead space CO2 is about 0 torr
c. At the end of inspiration, anatomic dead space is filled with air whose O2 is much less than 100 torr
d. At the end of inspiration, anatomic dead space is filled with air whose CO2 is about zero
e. B and D above
d. At the end of inspiration, anatomic dead space is filled with air whose CO2 is about zero
In a normal subject at sea level breathing 50% of O2, which compartments has the lowest CO2 parital pressure?
a. basal lung end pulmonary capillary blood
b. alveolar air
c. anatomic dead space at the start of expiration
d. arterial blood
e. anatomic dead space at the start of inspiration
c. anatomic dead space at the start of expiration
At high alveolar volumes:
a. compliance is reduced and further increase in volume is more difficult
b. compliance is reduced and further increase in volume is facilitated
c. compliance is increased and further increase in volume is more difficult
d. the slope of the compliance curve is the same as it is at low lung volumes
e. surface tension becomes decreased due to surfactant
a. compliance is reduced and further increase in volume is more difficult
A patient is being artifically ventilated during surgery at a rate of 20 breaths/min and a tidal volume od 250 ml/breath. Assuming a normal anatomical dead space of 150 ml, the alveolar ventilation in this patient is
a. 1000 ml/min
b. 2000 ml/min
c. 3000 ml/min
d. 4000 m//min
e. 5000 ml/min
b. 2000 ml/min
- VA= (VT-VD) x fresp
- (250-150) x 20
- VA=2000 ml/min
In the upright position, ventilation per unit lung volume is greater at the base of the lung than at the apex because the base of the lung
a. Has more negative intrapleural pressure than the apex at the start of inspiration.
b. Is less expanded than the apex
c. Has lower compliance than the apex
d. Has more intrapulmonary-intrapleural pressure difference than the apex at the start of inspiration
b. Is less expanded than the apex
We use Alveolar Ventilation Rate instead of Minute Ventilation to discuss the lung’s ability to release CO2 because normally at rest:
a. during inspiration, only 350 ml of fresh air enters the mouth
b. during expiration, only 350 ml of air leaves the alveoli
c. during expiration, only 350 ml of air leaves the mouth
d. the TV is normally less than the Anatomic Dead Space
e. only the first 350 ml of air leaving alveoli passes through the mouth
e. only the first 350 ml of air leaving alveoli passes through the mouth
Which statement about alveolar ventilation is correct?
a. If a normal subject inspires, more of the incoming air goes initially to the apicals areas compared with the basal areas of the lungs
b. Alveolar ventilation equals tidal volume+dead space volume
c. Alveolar ventilation equals tidal volume+ inspiratory reserve volume
d. In inspiration from FRC, the basal lung areas are more compliant than apical areas
e. Both (A) and (D) are correct
d. In inspiration from FRC, the basal lung areas are more compliant than apical areas
As you sit here reading this question:
a. your Alveolar Ventilation Rate is about 4200 ml/sec
b. your respiratory rate is about 12 per second
c. your Minute Ventilation is about 100 ml/sec
d. your cardiac output is about 5 L/sec
e. None of the above
c. your Minute Ventilation is about 100 ml/sec
If a subject at rest voluntary increased breathing rate (f) while maintaining the same tidal volume:
a. Minute ventilation would be unchanged
b. Dead space ventilation would be increased
c. Alveolar ventilation would be unchanged
d. Alveolar ventilation would decrease
b. Dead space ventilation would be increased
