Blake's A&P Exam 2: Humidity, Gas Exchange, and Lung Function

Question 1

What impact does humidity have on gas mixtures?

Answer 1

Humidity affects the water vapor pressure, which displaces some oxygen and other inspired gases in the total gas mixture.

The vapor pressure in humidified air is about 47 mmHg.

Question 2

What are the normal pulmonary arterial blood gas levels for PO2 and PCO2?

Answer 2

Normal arterial blood gas levels are PO2 of 40 mmHg and PCO2 of 45 mmHg.

Question 3

How does age affect arterial PO2 levels?

Answer 3

Older individuals typically have lower arterial PO2 levels compared to younger individuals, with values decreasing from about 100 mmHg in youth to around 80 mmHg at age 90.

Question 4

What is the concept of dead space ventilation?

Answer 4

Dead space ventilation refers to the portion of inspired air that does not participate in gas exchange, typically the last 150 cc’s of an inspired breath or first 150cc’s of an expired breath.
- The specific calculation for deadspace is 1cc/lb IBW

Question 5

What is the definition of anatomical dead space?

Answer 5

Anatomical dead space is the volume of the conducting airways where gas exchange does not occur.
- Approimately 150cc’s or 1cc/lb IBW

Question 6

What is alveolar dead space?

Answer 6

Alveolar dead space occurs when ventilated alveoli are not perfused with blood, preventing gas exchange.

Question 7

What is minute ventilation?

Answer 7

Minute ventilation is the total volume of air inhaled or exhaled from the lungs in one minute, consisting of both dead space ventilation and alveolar ventilation.

Question 8

What is the normal minute alveolar ventilation?

Answer 8

Normal minute alveolar ventilation is 4.2 liters per minute.

Question 9

What is the total minute ventilation for an average individual?

Answer 9

Total minute ventilation is approximately 6 liters per minute.

Question 10

What is the net filtration pressure in the pulmonary capillaries?

Answer 10

The net filtration pressure in the pulmonary capillaries is 1 mmHg.
- 𝝿cap=28mmHg
- Pcap=7mmHg
- Pisf=-8mmHg
- 𝝿isf=14mmHg
So NFP=14+8+7-28
NFP=1mmHg

Question 11

How does gravity affect lung perfusion?

Answer 11

Gravity causes more blood flow to the lower regions of the lung, ensuring better ventilation-perfusion matching.

Question 12

What is hypoxic pulmonary vasoconstriction?

Answer 12

Hypoxic pulmonary vasoconstriction is a process where low oxygen levels (primary) or high CO2 levels (secondary) in the alveoli cause vasoconstriction in upstream pulmonary vessels, redirecting blood flow to better-ventilated areas.

Question 13

True or False: General anesthetics can interfere with hypoxic pulmonary vasoconstriction.

Answer 13

True
- Volatile anesthetics open K+ channels in vascular smooth muscle beds that lead to vasodilation instead of vasoconstriction.
- This can effectively lead to continued bloodflow to poorly ventilated areas of the lung which can directly compromise gas exchange!

Question 14

What happens to lung volumes under general anesthesia?

Answer 14

General anesthesia and muscle relaxation can significantly reduce lung volumes, especially in the supine position.

Question 15

What is the expected PO2 in pulmonary venous blood compared to systemic arterial blood?

Answer 15

Pulmonary venous blood PO2 should be slightly higher (104mmHg) than systemic arterial blood PO2 (100mmHg) due to bronchiolar admixture.

Question 16

What is the effect of aging on lung function?

Answer 16

Lung function begins to deteriorate around age 20, leading to decreased gas exchange efficiency and increased dead space.

Question 17

Fill in the blank: The last 150cc of an inspired or the first 150cc of expired breath that is not used for gas exchange is referred to as _______.

Answer 17

[dead space ventilation]

Technically this is 1cc/lb of IBW deadspace but 150cc is the average healty 20yr old number.

Question 18

What is the significance of the pleural pressure gradient?

Answer 18

The pleural pressure gradient directs fresh air to the base of the lung where blood flow is higher.

Question 19

What factors can disrupt fluid balance in the lungs?

Answer 19

• Capillary permeability
• Increased blood pressure
• Decreased oncotic pressure

Question 20

What is the term used to refer to both types of Dead Space in the lung?

Answer 20

Physiologic Dead Space

Physiologic Dead Space includes both anatomical and alveolar dead space.

Question 21

What is the typical anatomical dead space for a 20-year-old?

Answer 21

150 cc

Anatomical dead space refers to the volume of air that does not participate in gas exchange.

Question 22

How does age affect alveolar dead space?

Answer 22

Increases with age

Older individuals may have more areas of the lungs that are not functioning optimally.

Question 23

What is the relationship between health status and alveolar dead space?

Answer 23

More healthy = less alveolar dead space; more unhealthy = more alveolar dead space

Healthy lungs typically have less dead space for gas exchange.

Question 24

What is the consequence of increasing alveolar dead space?

Answer 24

Increased ventilation needed

More ventilation is required to compensate for areas where gas exchange is not occurring.

Question 25

What is the tidal volume (Vt) used in the equation discussed?

Answer 25

500 cc ## Footnote This volume consists of both dead space and alveolar ventilation.

Question 26

What does the abbreviation V̇A represent?

Answer 26

Alveolar ventilation ## Footnote V̇A refers to the volume of air entering the alveoli for gas exchange.

Question 27

What is the normal respiratory rate for a healthy 20-year-old?

Answer 27

12 breaths per minute ## Footnote This is the expected respiratory frequency for a healthy individual.

Question 28

Calculate the minute alveolar ventilation for a person taking 12 breaths per minute with an alveolar ventilation of 350 cc per breath.

Answer 28

4.2 liters per minute ## Footnote This is calculated by multiplying breaths per minute by alveolar ventilation per breath.

Question 29

What is the normal minute dead space ventilation for a healthy individual?

Answer 29

1.8 liters per minute ## Footnote This is derived from 150 cc of dead space ventilation multiplied by 12 breaths per minute.

Question 30

What is the total minute ventilation combining both dead space and alveolar ventilation?

Answer 30

6 liters per minute ## Footnote This is the sum of minute alveolar ventilation and minute dead space ventilation.

Question 31

What does the abbreviation V̇E stand for?

Answer 31

Minute total ventilation ## Footnote This includes all expired air, both from dead space and alveolar ventilation.

Question 32

At the end of an inspired breath, which gas composition is expelled first?

Answer 32

Dead space gas ## Footnote The first portion of the expired breath corresponds to the air that was in the dead space.

Question 33

What is the expected alveolar PO2 with normal ventilation?

Answer 33

About 104 mmHg ## Footnote This is a typical value when blood flow and ventilation are normal.

Question 34

What happens to alveolar PO2 if ventilation is increased?

Answer 34

Alveolar PO2 increases ## Footnote Increased ventilation allows more fresh air to enter the lungs.

Question 35

What is the normal alveolar PCO2 with normal ventilation?

Answer 35

40 mmHg ## Footnote This is the expected level of carbon dioxide in the alveoli under normal conditions.

Question 36

What is the pulmonary capillary pressure typically measured at?

Answer 36

7 mmHg ## Footnote This value is lower than systemic circulation pressures.

Question 37

What is the interstitial protein osmotic pressure in the pulmonary circulation?

Answer 37

14 mmHg ## Footnote This is approximately double what it is in the systemic circulation.

Question 38

What is the net filtration pressure in the pulmonary capillaries?

Answer 38

1 mmHg ## Footnote This is a measure of fluid movement out of the capillary into the interstitium.

Question 39

What role do lymphatics play in the lungs?

Answer 39

They remove excess fluid ## Footnote Lymphatics help maintain fluid balance in the lungs.

Question 40

True or False: Fluid in the lungs is beneficial for gas exchange.

Answer 40

False ## Footnote Excess fluid in the lungs can obstruct gas exchange.

Question 41

What is the left atrial pressure threshold that can lead to pulmonary edema?

Answer 41

Around 23 mmHg ## Footnote This pressure can indicate a significant problem in fluid balance.

Question 42

What is the significance of left atrial pressure in relation to edema formation in the lungs?

Answer 42

Left atrial pressure normally around 2 can rise to about 23 before causing significant problems ## Footnote This indicates a safety factor for edema formation in the lungs.

Question 43

What are two major risks that can lead to fluid buildup in the lungs?

Answer 43

* Loss of blood without replacement of colloids * Left heart failure ## Footnote These conditions can lead to increased pressures in the lungs and potential edema.

Question 44

What does the filtration coefficient do in the context of fluid flow in the lungs?

Answer 44

It turns pressure into a fluid flow rate (Q) ## Footnote Q stands for flow and is influenced by various filtration forces.

Question 45

What can cause increased capillary permeability leading to pulmonary edema?

Answer 45

* Infections * ARBs * Inhaled toxins * Oxygen toxicity ## Footnote These factors can lead to protein leakage into the interstitium and fluid buildup.

Question 46

How does left heart failure contribute to pulmonary edema?

Answer 46

It causes blood to back up in the lungs, increasing pressure and leading to edema ## Footnote The inability of the left heart to pump effectively results in fluid accumulation.

Question 47

Fill in the blank: The average pleural pressure in between breaths is _______.

Answer 47

negative five centimeters of water ## Footnote This is a standard measurement that affects lung mechanics.

Question 48

How does gravity affect blood flow in the lungs?

Answer 48

Lower regions of the lung receive more blood flow due to greater distension and lower resistance ## Footnote Blood flow is gravity-dependent, with more perfusion at the lung base.

Question 49

What happens to alveoli at the top and bottom of the lung during normal breathing (FRC)?

Answer 49

They are typically more full (about 60%) compared to those at the base (about 25%) ## Footnote This affects where fresh air is directed during inhalation.

Question 50

What happens to alveoli at the top and bottom of the lung during normal breathing (RV)?

Answer 50

They are typically more full (30%) at the the top compared with the bottom (20%). - 20% is the lowest that alveolar air can get due to small airways collapsing before more air can be pushed out.

Question 51

What can cause flash pulmonary edema in a patient with a closed airway?

Answer 51

Generating extremely negative thoracic pressure while trying to inhale ## Footnote This can occur in young, fit individuals attempting to breathe against an obstruction.

Question 52

What are some factors that can decrease interstitial hydrostatic pressure?

Answer 52

* Rapid evacuation of pneumothorax * Closed airway breathing attempts ## Footnote These actions can create transient changes in pressure that affect fluid dynamics in the lungs.

Question 53

True or False: High altitude can lead to pulmonary edema.

Answer 53

True ## Footnote High altitude conditions are associated with fluid retention in the lungs, although the exact mechanisms are not fully understood.

Question 54

What is the effect of insufficient lymphatic drainage on pulmonary edema?

Answer 54

It can lead to fluid accumulation in the lungs ## Footnote Conditions such as tumors or scarring can impede lymphatic function.

Question 55

What is the impact of increased blood pressure on pulmonary edema?

Answer 55

It can exacerbate left heart failure and increase lung pressures ## Footnote This can lead to fluid leakage into the lungs.

Question 56

What is the role of alveolar compliance in lung function?

Answer 56

It describes how easily alveoli can expand and fill with air ## Footnote Higher compliance allows for easier air filling in less full alveoli.

Question 57

What happens to blood flow and ventilation in the upright lung?

Answer 57

Blood flow is greater at the base, while ventilation is also directed towards areas with more blood flow ## Footnote This results in an efficient V/Q ratio.

Question 58

What is the alveolar fullness at the top of the lung at FRC? What about RV?

Answer 58

60% full at FRC and 30% full at RV

Question 59

What is the alveolar fullness at the base of the lung at FRC?

Answer 59

25% full a FRC and 20% full at RV - 20% is the lowest an alveoli can be due to small airway collapse

Question 60

How does gravity affect air distribution in the lungs?

Answer 60

It directs more air to the base of the lung

Question 61

What is transpulmonary pressure (P_TP)?

Answer 61

Alveolar distending pressure

Question 62

At FRC, what is the transpulmonary pressure at the base of the lung if alveolar pressure is zero and pleural pressure is -1.5?

Answer 62

1.5

Question 63

What is the transpulmonary pressure at the top of the lung at FRC if pleural pressure is more negative (-8.5)?

Answer 63

8.5

Question 64

What happens to the compliance of the lung as it approaches capacity?

Answer 64

It decreases, making it harder to add more air

Question 65

What does a steep slope on the compliance curve indicate?

Answer 65

High compliance

Question 66

What is the compliance behavior of the lung during inspiration compared to expiration? What is this phenomenon called?

Answer 66

More compliant during expiration - Hysteresis ## Footnote The lung is more compliant on expiration than inspiration because during inspiration, the lung has already had to overcome the initial stretch resistance. Alveoli are now more open and “less stiff.”

Question 67

What is the pleural pressure at the apex of the lung at RV in a healthy 20-year-old?

Answer 67

-2.2

Question 68

What is the transpulmonary pressure at the base of the lung at RV if pleural pressure is 4.8?

Answer 68

-4.8

Question 69

At what capacity do alveoli typically remain when airways collapse?

Answer 69

20%

Question 70

What is the compliance of the top of the lung when it is 30% full?

Answer 70

High compliance

Question 71

What happens to the alveoli at the base of the lung at RV?

Answer 71

They are typically collapsed

Question 72

How does the filling of the top of the lung affect the base of the lung?

Answer 72

It makes the base more prone to accepting volume ## Footnote All alveoli are connected so pullinf on the upper ones generates force to pull open the lower ones.

Question 73

What is the result of not having fresh air directed to well-perfused areas of the lung?

Answer 73

Gas exchange is compromised

Question 74

Fill in the blank: The lungs typically behave differently on _______ compared to _______.

Answer 74

inspiration; expiration

Question 75

True or False: The airways at the top of the lung are typically collapsed.

Answer 75

False

Question 76

What does the term 'compliance' refer to in the context of lung physiology?

Answer 76

The ease with which the lung expands

Question 77

What happens to the alveoli during a deep inspiration?

Answer 77

They fill more fully and become more compliant

Question 78

What happens to lung volumes when a patient is placed in a supine position under general anesthesia?

Answer 78

Lung volumes decrease significantly, often resulting in very low lung volumes due to body position and muscle relaxation. ## Footnote This is primarily because abdominal contents push against the diaphragm, reducing functional residual capacity (FRC) from about 3 liters in the upright position to about 2 liters in the supine position.

Question 79

What is the compliance of the top and base of the lungs, especially at RV?

Answer 79

The top of the lung is very compliant, while the base of the lung is not compliant at all. ## Footnote Increased transpulmonary pressure at the top keeps alveoli distended, while collapsed small airways at the base prevent air from entering.

Question 80

What is hypoxic pulmonary vasoconstriction?

Answer 80

It is the constriction of blood vessels upstream of poorly ventilated alveoli, redirecting blood flow to better-ventilated areas. ## Footnote This mechanism is unique to the lungs; in other vascular beds, low oxygen levels typically cause relaxation of blood vessels.

Question 81

What role does smooth muscle in pulmonary blood vessels play?

Answer 81

It can constrict or relax to determine blood flow through pulmonary capillaries based on the ventilation status of the alveoli. ## Footnote This allows for better matching of ventilation and perfusion in the lungs.

Question 82

Fill in the blank: The tendency of airway smooth muscle is to tighten up in response to _______.

Answer 82

hyperoxia ## Footnote Over time, hyperoxia can cause capillary swiss-cheese, so this is a protective mechanism for the lung.

Question 83

How does general anesthesia affect the body's ability to manage pulmonary blood flow?

Answer 83

General anesthetics open potassium channels in vascular smooth muscle, leading to relaxation and potentially allowing blood flow in poorly ventilated areas. ## Footnote This interferes with the body's normal compensatory mechanisms for managing ventilation and perfusion.

Question 84

What happens to alveolar gas composition if blood flow through a capillary is stopped?

Answer 84

The alveolar gas composition will resemble the inspired gas mixture, with PO2 close to 150 and CO2 close to zero. ## Footnote This occurs because without blood flow, there is no gas exchange happening in that part of the lung.

Question 85

What is the significance of the compliance in different lung regions?

Answer 85

Compliance varies, affecting how air is distributed; air tends to go to areas with higher compliance. ## Footnote This is crucial for effective ventilation during different body positions and conditions.

Question 86

True or False: The alveoli at the top of the lung are typically smaller than those at the base.

Answer 86

False

Question 87

What is a consequence of using 100% oxygen for an extended period?

Answer 87

It can lead to airway reactivity and potential tightening of small airways, complicating ventilation. ## Footnote Prolonged exposure to high oxygen levels can cause adverse respiratory effects.

Question 88

What happens to expiratory reserve volume (ERV) when a person moves from an upright to a supine position?

Answer 88

ERV decreases due to abdominal contents pushing against the diaphragm, involuntarily pushing air out of the lungs.

Question 89

What is the primary controller of smooth muscle reactivity in the lungs?

Answer 89

Hypoxic pulmonary vasoconstriction is the most important reflex. ## Footnote Other responses, such as airway tightening or reactions to CO2 levels, are secondary to this mechanism.

Question 90

What happens to blood vessels in a collapsed part of the lung?

Answer 90

Blood vessels in that area constrict to redirect blood flow to healthier regions of the lung. ## Footnote This helps maintain blood gas levels and overall lung function.

Question 91

What occurs when there is a mismatch between ventilation and perfusion?

Answer 91

The body compensates by constricting blood vessels in poorly ventilated areas to optimize gas exchange elsewhere.

Question 92

What is the expected change in vital capacity when a person transitions from upright to supine?

Answer 92

Trick question: Depending on the weight of abdominal contents, ERV can decrease significantly when moving supine due to some of the usual voluntary air reservoir being involuntarily pushed out. - When our ERV decreases, our IRV increases so our maxium depth of inspiration isn't affected. - VC remains constant.

Question 93

What happens to the Expiratory Reserve Volume (ERV) when moving into a supine position?

Answer 93

ERV is reduced when moving into a supine position ## Footnote This reduction occurs because some of the volume that could be expired is involuntarily pushed out.

Question 94

How does moving into a supine position affect vital capacity?

Answer 94

Vital capacity does not change ## Footnote The depth of a maximal breath effort remains the same.

Question 95

What happens to Inspiratory Reserve Volume (IRV) and Expiratory Reserve Volume (ERV) in a supine position?

Answer 95

IRV tends to expand, ERV tends to shrink ## Footnote This shift occurs due to pressure from the base of the lung on the diaphragm.

Question 96

What equipment is typically used to measure lung volumes and capacities?

Answer 96

Spirometer ## Footnote An incentive spirometer is commonly used in pulmonary function labs.

Question 97

Describe the basic function of a spirometer.

Answer 97

Measures air volume during inspiration and expiration ## Footnote The device operates by displacing air in an upside-down container, tracing patterns based on air volume.

Question 98

What does a normal breathing tracing on a spirometer represent?

Answer 98

Tidal volume ## Footnote This is the volume of air inhaled or exhaled during normal breathing.

Question 99

What is measured when a patient is instructed to expel all air from their lungs?

Answer 99

Expiratory Reserve Volume (ERV) ## Footnote This is the additional air that can be forcibly exhaled after a normal expiration.

Question 100

What is measured when a patient is instructed to inspire as much air as possible?

Answer 100

Inspiratory Reserve Volume (IRV) ## Footnote This is the additional air that can be inhaled after a normal inspiration.

Question 101

Fill in the blank: The old spirometer equipment resembled an upside-down _______.

Answer 101

water heater ## Footnote This design was used to measure air volumes before modern computerized equipment.

Question 102

What is the total lung capacity?

Answer 102

The maximum amount of air the lungs can hold ## Footnote This includes all volumes: tidal volume, inspiratory reserve volume, and expiratory reserve volume.