Pulmonary Physiology Part I

Question 1

What is the main function of the pulmonary system?

Answer 1

To exchange gases (oxygen and carbon dioxide) between the environment and the cells to power cellular respiration.

Question 2

What are the two major gases exchanged by the pulmonary system?

Answer 2

Oxygen (O₂) and carbon dioxide (CO₂).

Question 3

How is oxygen used in the body?

Answer 3

Oxygen is transported through the airways, heart, and circulation to the mitochondria, where it powers aerobic metabolism.

Question 4

What is carbon dioxide’s role in the pulmonary system?

Answer 4

CO₂ is a byproduct of aerobic metabolism, transported from tissues through the cardiovascular system to the lungs, and expelled from the body.

Question 5

Why must the pulmonary system adapt its rate of gas exchange?

Answer 5

It adapts to meet the varying metabolic demands of the body, such as during rest or heavy activity.

Question 6

What is a common way to measure metabolic demand?

Answer 6

By measuring the rate of oxygen consumption.

Question 7

How much can oxygen consumption increase during heavy activity?

Answer 7

It can increase up to twentyfold compared to oxygen consumption at rest.

Question 8

What is “minute ventilation”?

Answer 8

The amount of air that is breathed in per minute.

Question 9

What is the typical range of minute ventilation from rest to heavy activity?

Answer 9

From about 5 liters per minute at rest to 100 liters per minute during heavy activity.

Question 10

What are the two main processes of the pulmonary system discussed in the first lesson?

Answer 10

Ventilation (air flow) and defense systems (protection against environmental factors)

Question 11

Why is the pulmonary system unique in its interaction with the environment?

Answer 11

It is the only body system directly exposed to the environment through the airways.

Question 12

What is ventilation?

Answer 12

Ventilation is the bulk flow of air into and out of the lungs, driven by pressure gradients.

Question 13

What are the key components of the pulmonary system shown in the schematic?

Answer 13

Conducting airways, alveoli, chest wall, and intrapleural space (space between the lung and chest wall).

Question 14

What is the pressure difference necessary for air to flow during ventilation?

Answer 14

The pressure difference between the alveoli (P_in) and the atmospheric pressure (P_out).

Question 15

How does air enter the lungs during inspiration?

Answer 15

The diaphragm contracts, increasing thoracic volume and decreasing pressure in the alveoli, which allows air to flow into the lungs.

Question 16

What happens to thoracic volume and alveolar pressure during inspiration?

Answer 16

Thoracic volume increases, causing a decrease in pressure inside the alveoli, leading to air flowing into the lungs.

Question 17

What role does the diaphragm play in inspiration?

Answer 17

The diaphragm’s contraction increases the volume of the thorax, which lowers alveolar pressure and allows air to flow into the lungs.

Question 18

How does air leave the lungs during exhalation?

Answer 18

The diaphragm relaxes, thoracic volume decreases, alveolar pressure increases, and air flows out of the lungs.

Question 19

What happens to alveolar pressure during exhalation?

Answer 19

Alveolar pressure increases as the thoracic volume decreases, causing air to flow out until the pressures inside and outside the alveoli are equal.

Question 20

What is the relationship between volume and pressure in the thoracic cavity during ventilation?

Answer 20

An increase in thoracic volume decreases alveolar pressure (inspiration), and a decrease in thoracic volume increases alveolar pressure (exhalation).

Question 21

What must be open for air to flow during ventilation?

Answer 21

The glottis must be open for air to flow into or out of the lungs.

Question 22

What happens to the chest wall at its equilibrium point?

Answer 22

At equilibrium, with no external pressure, the chest wall’s volume is large, and it returns to this size when not compressed.

Question 23

How does the lung behave at its equilibrium point?

Answer 23

The lung’s volume is small at equilibrium, like a deflated balloon, and it requires external pressure to expand.

Question 24

How are the lung and chest wall coupled together?

Answer 24

The lung and chest wall are coupled through the intrapleural space, which behaves like microscope slides with water between them—tough to separate but able to slide.

Question 25

What happens when the chest wall and lung are coupled together?

Answer 25

The chest wall’s volume decreases (it is pulled inward), and the lung’s volume increases (it is pulled outward).

Question 26

What pressure is generated by the coupling of the chest wall and lung?

Answer 26

A negative intrapleural pressure is created due to the opposing forces of the lung’s tendency to collapse and the chest wall’s tendency to expand.

Question 27

What is Functional Residual Capacity (FRC)?

Answer 27

FRC is the equilibrium point where the expanding force of the chest wall and the collapsing force of the lung are equal, occurring at the end of a normal exhalation.

Question 28

What is Total Lung Capacity (TLC)?

Answer 28

TLC is the maximum volume of air that the lung and chest wall can hold during full inhalation.

Question 29

What is Residual Volume (RV)?

Answer 29

RV is the volume of air remaining in the lungs after a maximal exhalation, which cannot be expelled while the lung and chest wall are coupled.

Question 30

How does intrapleural pressure change during inhalation?

Answer 30

During inhalation, intrapleural pressure becomes more negative, which helps pull the lungs open and decreases alveolar pressure, allowing air to flow in.

Question 31

What changes occur during exhalation?

Answer 31

The diaphragm relaxes, making the intrapleural pressure less negative and increasing alveolar pressure, which pushes air out of the lungs.

Question 32

How do alveolar pressure changes drive ventilation?

Answer 32

During inhalation, alveolar pressure becomes negative, drawing air in. During exhalation, it becomes positive, pushing air out until equilibrium is reached.

Question 33

What is the role of expiratory muscles in forced exhalation?

Answer 33

Expiratory muscles, like the abdominal muscles, help further reduce lung and thoracic volume during forced exhalation.

Question 34

What is minute ventilation?

Answer 34

Minute ventilation is the product of tidal volume (volume of breath during inhalation) and respiratory rate.

Question 35

How do you calculate minute ventilation with normal values?

Answer 35

Multiply a normal tidal volume (450 mL) by a normal respiratory rate (12 breaths/min), resulting in approximately 5,400 mL/min.

Question 36

What is the purpose of ventilation in the lungs?

Answer 36

The purpose of ventilation is to bring air into the alveoli, where gas exchange takes place.

Question 37

What is the conducting zone in the lungs?

Answer 37

The conducting zone consists of airways where no gas exchange occurs and some air stays, known as anatomical dead space.

Question 38

What is anatomical dead space, and how much air does it typically contain?

Answer 38

Anatomical dead space is the part of the airway that doesn’t participate in gas exchange, typically about 150 mL in a healthy person.

Question 39

How do you calculate alveolar ventilation?

Answer 39

Alveolar ventilation = (Tidal volume - Dead space volume) × Respiratory rate. For example, (450 mL - 150 mL) × 12 breaths/min = 3.6 L/min.

Question 40

What is the effect of disease on physiological dead space?

Answer 40

Diseases can increase physiological dead space by creating regions in the lung that don’t participate in gas exchange.

Question 41

How does gravity affect ventilation distribution in the lungs?

Answer 41

Gravity pulls the lungs downward when upright, causing alveoli at the lung base to be smaller and more compliant compared to those at the apex.

Question 42

How does the Slinky analogy relate to the lungs?

Answer 42

Like a Slinky, the weight of the lung pulls down, making alveoli at the top more expanded (less compliant) and alveoli at the base smaller and more compliant.

Question 43

What is the compliance of the lungs, and how does it vary?

Answer 43

Compliance refers to the lung’s stretchiness. Alveoli at the base are more compliant (easier to expand) than those at the apex due to less initial stretch.

Question 44

How does the difference in alveolar compliance affect ventilation?

Answer 44

During inhalation, more air goes to the alveoli at the lung base, which are more compliant and expand more than those at the apex.

Question 45

How does body position affect ventilation distribution?

Answer 45

When lying down, ventilation distribution shifts from the base-apex gradient to a difference between the anterior and posterior aspects of the lungs.

Question 46

What is a spirometer used for in lung function testing?

Answer 46

A spirometer measures the flow of air to determine the volume of air moved during ventilatory maneuvers.

Question 47

What is tidal volume?

Answer 47

Tidal volume is the volume of air breathed in and out during a normal inhalation and exhalation, typically about 450-500 mL per breath.

Question 48

What is the inspiratory reserve volume (IRV)?

Answer 48

IRV is the additional volume of air that can be inhaled after a normal inhalation.

Question 49

How is inspiratory capacity (IC) calculated?

Answer 49

Inspiratory capacity is the sum of the tidal volume and the inspiratory reserve volume.

Question 50

What is vital capacity (VC)?

Answer 50

Vital capacity is the volume of air exhaled from a maximum inhalation to a maximum exhalation.

Question 51

What is expiratory reserve volume (ERV)?

Answer 51

ERV is the additional volume of air that can be exhaled after a normal exhalation.

Question 52

What is residual volume (RV)?

Answer 52

RV is the volume of air left in the lungs after a maximal exhalation, not measurable with spirometry.

Question 53

What is functional residual capacity (FRC)?

Answer 53

FRC is the volume of air remaining in the lungs at the end of a normal exhalation.

Question 54

How is total lung capacity (TLC) calculated?

Answer 54

TLC is the sum of the vital capacity (VC) and the residual volume (RV)

Question 55

How are lung volumes and capacities influenced?

Answer 55

They are influenced by age, gender, and body size, and can vary with different lung diseases.

Question 56

What is forced vital capacity (FVC)?

Answer 56

FVC is the total volume of air exhaled as forcefully and quickly as possible after a maximal inhalation.

Question 57

What does FEV1 measure?

Answer 57

FEV1 measures the volume of air exhaled in the first second of the FVC maneuver.

Question 58

Why is the FEV1/FVC ratio important?

Answer 58

It indicates what fraction of the total forced vital capacity is exhaled in the first second, often used to diagnose obstructive lung diseases.

Question 59

What is a normal FEV1/FVC ratio?

Answer 59

A normal ratio is about 75-80%, meaning that most of the FVC is exhaled in the first second.

Question 60

How does the FEV1/FVC ratio change in obstructive lung diseases?

Answer 60

The ratio is generally lower in obstructive lung diseases due to limitations in airflow.

Question 61

What does a flow-volume loop show?

Answer 61

It plots volume along the x-axis and airflow along the y-axis, illustrating the relationship between inhalation and exhalation during spirometry.

Question 62

What is a pneumothorax?

Answer 62

A condition where air enters the intrapleural space due to a lesion in the lung or chest wall, causing the lung to collapse and the chest wall to expand.

Question 63

How do we treat a pneumothorax?

Answer 63

By inserting a chest tube connected to wall suction to remove excess air and allow the lung to re-expand

Question 64

What happens when the muscles of ventilation are weak?

Answer 64

It impairs ventilation, making it harder for patients to breathe due to insufficient pressure and volume changes.

Question 65

What is the effect of a high spinal cord injury (C3 or above) on ventilation?

Answer 65

It can lead to diaphragm paralysis, making the patient dependent on mechanical ventilation.

Question 66

Define paradoxical breathing pattern

Answer 66

A breathing pattern where the abdomen expands but the chest wall collapses during inhalation due to weak intercostal and abdominal muscles.

Question 67

How does airway diameter affect ventilation?

Answer 67

arrowing of airways, as seen in asthma, increases resistance to airflow, requiring more muscular effort to maintain ventilation.

Question 68

What is dynamic airway compression?

Answer 68

A phenomenon during forced exhalation where increased intrapleural pressure compresses the airways, limiting airflow.

Question 69

What is compliance in the context of lungs?

Answer 69

The ability of the lungs to stretch and expand; it can be increased in emphysema or decreased in pulmonary fibrosis.

Question 70

How does emphysema affect lung compliance?

Answer 70

It increases lung compliance, making the lung overly stretchy and reducing the elastic recoil needed for exhalation.

Question 71

Why is ventilation harder with pulmonary fibrosis?

Answer 71

Pulmonary fibrosis decreases lung compliance, requiring more muscular effort to expand the lungs.

Question 72

What role does surfactant play in the lungs?

Answer 72

It reduces surface tension in the alveoli, preventing them from collapsing and aiding in gas exchange.

Question 73

What respiratory issue can premature babies face due to lack of surfactant?

Answer 73

They may experience alveolar collapse, leading to respiratory distress.

Question 74

What is the function of the ventilatory pump?

Answer 74

To maintain airflow by coupling the lung and chest wall, supporting muscle strength, and managing compliance, surface tension, and airway diameter.

Question 75

How does a decrease in lung compliance affect breathing effort?

Answer 75

It requires more effort from the respiratory muscles to expand the lungs, increasing the work of breathing.

Question 76

What is the primary function of the nasal passages in lung protection?

Answer 76

The nasal passages filter out larger particles of dust and debris using nose hairs and turbinates, which create turbulent airflow to trap particles.

Question 77

How do turbinates aid in protecting the lungs?

Answer 77

Turbinates are shells of bone in the nasal passages that create turbulent airflow, helping to trap larger air particles before they enter deeper airways.

Question 78

What role do macrophages play in lung protection?

Answer 78

Macrophages are immune cells in the respiratory zone that engulf particles and bacteria, helping to keep the small airways and alveoli clear.

Question 79

What is the mucociliary escalator?

Answer 79

It is a system in the conducting zone where mucus traps particles, and cilia sweep the mucus and trapped particles up towards larger airways for removal.

Question 80

Which factors can impair the function of the cilia in the mucociliary escalator?

Answer 80

Smoking, anesthesia, dehydration, and various lung diseases can impair cilia function, leading to retained particles, inflammation, and potential infections.

Question 81

What is the significance of the mucociliary escalator in lung health?

Answer 81

It helps clear mucus and trapped particles from the airways, preventing inflammation and infection like pneumonia.

Question 82

What is the primary purpose of a cough in the pulmonary system?

Answer 82

A cough helps clear irritants and particles from the airways, protecting the lungs from infection and inflammation.

Question 83

What are the four phases of a cough?

Answer 83

1.Inspiration (inhaling about 60% of maximal capacity)
2. Compression (thoracic compression to build pressure), 3. Glottis control (closing to maintain pressure)
4. Expulsion (releasing the glottis to expel air and irritants).

Question 84

Why is assessing a patient’s ability to cough important in clinical settings?

Answer 84

It ensures they can effectively clear their airways, which is crucial for preventing respiratory complications, especially in patients with muscular weakness.

Question 85

How can lung protection mechanisms be compromised in clinical populations?

Answer 85

Impaired cilia function, weakened cough ability, or decreased mucus clearance can lead to retained particles and increased risk of infections like pneumonia.