Exam 3: 1 Apr Understanding Pulmonary Function and Mechanics

Question 1

What is the significance of PO2 in relation to dead space?

Answer 1

PO2 would probably be lower than what the PO2 is in dead space

Dead space refers to areas of the lungs where gas exchange does not occur.

Question 2

What is the total pressure of all gases typically used for calculations?

Answer 2

760 mmHg

This is the standard atmospheric pressure at sea level.

Question 3

What does the flow volume loop indicate during expiration?

Answer 3

It helps assess the effort-independent phase and airway collapse

A normal flow volume loop shows a specific shape that indicates healthy airflow.

Question 4

What does a low FEV1/FVC ratio indicate?

Answer 4

It indicates difficulty in getting air out of the lungs

FEV1 stands for Forced Expiratory Volume in one second, and FVC stands for Forced Vital Capacity.

Question 5

What is FEF25-75?

Answer 5

It is a measure of forced expiratory flow rate occurring during the middle part of the breath

This measurement is often used to assess small airway reactivity.

Question 6

What happens to FRC when a person moves from an upright to a supine position?

Answer 6

FRC is reduced

FRC stands for Functional Residual Capacity.

Question 7

What remains unchanged when changing from upright to supine position?

Answer 7

Total lung capacity

Total lung capacity may decrease slightly in certain cases, such as obesity.

Question 8

What do expired gases indicate about the pulmonary system?

Answer 8

They provide clues about what is happening in the lungs

Expired gas analysis can help diagnose respiratory conditions.

Question 9

What is observed in the first part of the expired breath?

Answer 9

It does not contain CO2 from inspired air

This is due to the presence of dead space in the respiratory system.

Question 10

What should the end-tidal CO2 be in a healthy individual?

Answer 10

Approximately 40 mmHg

This is consistent with arterial blood gas measurements in healthy individuals.

Question 11

What effect does adding fresh air have on alveolar PCO2?

Answer 11

It decreases the concentration of CO2 in the alveoli

Fresh air typically has negligible CO2 content.

Question 12

What is the average alveolar PCO2 in a healthy individual?

Answer 12

40 mmHg

This is the typical partial pressure of CO2 in the alveoli during normal respiration.

Question 13

How much air is typically in the lungs between breaths?

Answer 13

Approximately 3 liters

This is the volume corresponding to the Functional Residual Capacity.

Question 14

What is the fractional concentration of CO2 in the lungs?

Answer 14

About 5%

This is derived from the ratio of the partial pressure of CO2 to the total pressure of gases.

Question 15

What is the effect of breathing in 350 cc of fresh air?

Answer 15

It increases the total lung volume to 3.35 liters

This calculation includes the existing volume in the lungs.

Question 16

What happens to the concentration of CO2 after adding fresh air?

Answer 16

It decreases

This is due to the dilution effect of fresh air that is low in CO2.

Question 17

What is the volume of fresh air mentioned?

Answer 17

3.35 liters

Question 18

What is the initial CO2 concentration before fresh air is inhaled?

Answer 18

5.263%

Question 19

What is the new CO2 concentration after inhaling fresh air?

Answer 19

4.7%

Question 20

What is the approximate PCO2 after one breath of fresh air?

Answer 20

35.8 mmHg

Question 21

What is the average alveolar PCO2?

Answer 21

40 mmHg

Question 22

How much does the alveolar PCO2 fluctuate on average?

Answer 22

±4 mmHg

Question 23

What happens to CO2 concentration in the lungs over time after breathing in fresh air?

Answer 23

It increases due to CO2 unloading.

Question 24

What does a higher V/Q ratio at the apex of the lung indicate?

Answer 24

More fresh air is getting to the top of the lung.

Question 25

In healthy lungs, what influences the gases present in the alveoli?

Answer 25

A mixture from various parts of the lungs.

Question 26

What are the expected CO2 concentrations at the top and base of the lung in emphysema?

Answer 26

Top: lower than average; Base: higher than average.

Question 27

What does an inverted slope on the capnograph indicate in someone with severe emphysema?

Answer 27

Massive airway collapse during expiration.

Question 28

What causes the delay in the capnograph readings?

Answer 28

Length of tubing and low flow rate.

Question 29

What is the purpose of using a moisture trap in the capnograph?

Answer 29

To prevent clogging and inaccurate readings.

Question 30

What does the end-tidal CO2 represent?

Answer 30

It approximates arterial blood gases.

Question 31

What is alveolar dead space?

Answer 31

Air spaces that do not participate in gas exchange.

Question 32

How can alveolar dead space be estimated?

Answer 32

By comparing end-tidal CO2 and arterial PCO2.

Question 33

What is the Bohr equation used for?

Answer 33

To estimate the amount of alveolar dead space.

Question 34

What are the two types of dead space?

Answer 34

* Anatomical dead space * Alveolar dead space

Question 35

What should the CO2 levels be in anatomical and alveolar dead spaces?

Answer 35

Very low or zero CO2.

Question 36

What is the formula for the amount of CO2 in expired air?

Answer 36

It comes from ventilated and perfused alveoli.

Question 37

What is the relationship between tidal volume and CO2 expelled?

Answer 37

CO2 expired equals tidal volume times the concentration of CO2.

Question 38

What is the formula for calculating the amount of CO2 in expired air?

Answer 38

The amount of CO2 in expired air equals tidal volume multiplied by the fractional concentration of CO2 in the mixed expired air. ## Footnote Tidal volume is typically around 500 cc's.

Question 39

What does the term 'VA' represent in the context of lung physiology?

Answer 39

VA represents the volume of alveolar air. ## Footnote This is important for calculating gas exchange in the lungs.

Question 40

How do you calculate the volume of alveolar air (VA)?

Answer 40

VA is equal to tidal volume minus dead space volume (VD). ## Footnote The formula is VA = VT - VD.

Question 41

What is the relationship between mixed expired CO2 and CO2 from healthy alveoli?

Answer 41

The amount of CO2 in the mixed expired sample must equal the amount of CO2 coming from the healthy areas of the lung. ## Footnote This indicates the contribution of functional alveoli to expired gases.

Question 42

What is the normal value for fractional expired CO2 in healthy individuals?

Answer 42

The fractional expired CO2 should be lower than 5%. ## Footnote This is typically around 27 mmHg for mixed expired CO2.

Question 43

What does 'VD' stand for in respiratory physiology?

Answer 43

VD stands for the volume of dead space. ## Footnote This includes both anatomical and physiological dead space.

Question 44

What is the significance of the Bohr equation in respiratory physiology?

Answer 44

The Bohr equation allows for the calculation of physiological dead space based on the differences in CO2 fractions. ## Footnote It helps estimate the efficiency of ventilation.

Question 45

True or False: Alveolar CO2 is typically around 40 mmHg in healthy individuals.

Answer 45

True. ## Footnote This is a standard reference point for normal alveolar gas exchange.

Question 46

What happens to the total pressure in the equation when calculating fractional concentrations?

Answer 46

The total pressure cancels out of the equation when it is present in all terms. ## Footnote This simplifies calculations for fractional concentrations.

Question 47

What is the estimated physiologic dead space for a healthy 20-year-old?

Answer 47

The estimated physiologic dead space is about 150 cc's. ## Footnote This can increase with age or certain medical conditions.

Question 48

Fill in the blank: The formula for calculating the volume of dead space divided by tidal volume is equal to the difference in the fractional alveolar concentration of CO2 minus the _______.

Answer 48

mixed expired fractional concentration of CO2. ## Footnote This relationship is crucial for understanding ventilation efficiency.

Question 49

What does 'F' represent in the context of gas concentrations?

Answer 49

F represents the fractional concentration of a gas. ## Footnote This is often expressed as a decimal.

Question 50

What is the clinical relevance of calculating alveolar dead space?

Answer 50

Calculating alveolar dead space helps assess ventilation efficiency and guide ventilatory support. ## Footnote High alveolar dead space indicates poor gas exchange.

Question 51

What is the equation used to solve for total dead space?

Answer 51

Physiologic dead space is calculated using the equation involving VD, CO2 and subtracting anatomical dead space from VT CO2. ## Footnote VD = Physiologic dead space, VT = Tidal volume, CO2 = Carbon dioxide concentration.

Question 52

How is compliance defined in terms of the pulmonary system?

Answer 52

Compliance reflects how easy it is to get fresh air into the lungs and how easy it is to get air out of the lungs.

Question 53

What are the two main barriers to air entering the lungs?

Answer 53

* Elastic recoil of the lungs * Chest wall compliance

Question 54

What does the elastic recoil of the lung want to do?

Answer 54

The elastic recoil of the lung wants to be as empty as possible.

Question 55

What happens to chest wall compliance when a patient is lying on their back?

Answer 55

Chest wall compliance is reduced due to extra weight on the chest.

Question 56

What is the effect of losing lung elastic recoil on the chest wall?

Answer 56

If lung elastic recoil decreases, the chest wall may protrude outward, leading to increased lung volume.

Question 57

What is the relationship between lung volume and pleural pressure in emphysema?

Answer 57

In emphysema, lung volumes are greater even with a less negative pleural pressure.

Question 58

What is the formula for calculating compliance?

Answer 58

Compliance = ΔV / ΔP.

Question 59

What is the normal pulmonary compliance at functional residual capacity (FRC)?

Answer 59

Normal pulmonary compliance is about 0.2 liters per centimeter of water.

Question 60

In terms of compliance, how do individual components of the respiratory system relate to the overall system?

Answer 60

The system compliance is less than the compliance of either individual component.

Question 61

True or False: The compliance of a series system is greater than the compliance of its individual parts.

Answer 61

False.

Question 62

Fill in the blank: The total resistance in a series system is calculated as _______.

Answer 62

R1 + R2.

Question 63

What happens to pleural pressure if lung elastic recoil decreases?

Answer 63

Pleural pressure may become more positive.

Question 64

How does the chest wall behave when the lung's elastic recoil is lost?

Answer 64

The chest wall tends to protrude outward.

Question 65

What is resistance in the context of current flow?

Answer 65

Resistance is how hard it is to push current through a system.

Question 66

How do you calculate total resistance in a series circuit?

Answer 66

Total resistance is the sum of the individual resistances: R_total = R1 + R2.

Question 67

What happens to total resistance in a parallel circuit?

Answer 67

Total resistance is lower than each individual resistance.

Question 68

What is the formula for total resistance in a parallel circuit?

Answer 68

1/R_total = 1/R1 + 1/R2.

Question 69

If R1 and R2 are both 2 ohms in a parallel circuit, what is the total resistance?

Answer 69

Total resistance is 1 ohm.

Question 70

What does compliance measure in the pulmonary system?

Answer 70

Compliance measures how easy it is to put air into the lungs using a given amount of pressure.

Question 71

How does resistance relate to compliance?

Answer 71

Resistance indicates how hard it is to move air, while compliance indicates how easy it is.

Question 72

If the compliance of the chest wall is 0.2 L/cm H2O, what is the compliance of the lung?

Answer 72

The compliance of the lung is also 0.2 L/cm H2O.

Question 73

What is the formula for total compliance in a series arrangement?

Answer 73

Total compliance is lower than either of the individual compliances.

Question 74

What happens to lung inflation if the chest wall integrity is compromised?

Answer 74

The lung will deflate and be difficult to inflate.

Question 75

What is pneumothorax?

Answer 75

Pneumothorax is an opening for air that fills the pleural space, making it hard to inflate the lung.

Question 76

What generates negative pleural pressure?

Answer 76

Negative pleural pressure is generated by the opposing recoil of the chest wall and lung.

Question 77

Fill in the blank: The total resistance in a series circuit is equal to _______.

Answer 77

R1 + R2

Question 78

True or False: In a parallel circuit, increasing the number of pathways increases total resistance.

Answer 78

False

Question 79

What will happen if blood fills the pleural space?

Answer 79

It will make it difficult to ventilate the lung.

Question 80

What is the compliance of the system if both chest wall and lung compliance are 0.2 L/cm H2O?

Answer 80

The compliance of the system will be 0.1 L/cm H2O.

Question 81

What is the relationship between the chest wall and lung in terms of their arrangement for airflow?

Answer 81

The chest wall and lung are arranged in series.