Lecture 34 - Respiratory System: Ventilation, Airway, Resistance, and Breathing

Question 1

Respiratory reflexes can change breathing movements in terms of ___? (3 things)

Answer 1

1. Timing
2. Pattern
3. Force

NOTE: all respiratory reflexes are long (neural) reflexes

Question 2

What is a sigh?

Answer 2

A reflexive breathing pattern which creates a slow, deep breath that reinflates pulmonary lobules

Question 3

What does a sigh re-inflate and how does it occur?

Answer 3

A sigh helps re-inflate pulmonary lobules. Re-inflating alveolar sacs requires an inspiration with greater force than that provided by resting tidal volume. This extra inflation force is provided by periodic reflexive sighs (single deep breaths)

Question 4

What are 2 protective reflexes to irritants in the airway? What type of response is this?

Answer 4

It is an expiratory response

1. Sneezing - a purely involuntary reflex triggered by the presence of irritants or particles in the nasal cavity or nasopharynx
2. Coughing - reflexively triggered by the presence of irritants or particles in the lower respiratory tract (coughing can be voluntary)

Question 5

Describe the 2 ways muscles related to respiratory activity contributes to current oxygen consumption

Answer 5

1. Primary inspiratory muscles - uses relatively little energy; only ~3-5% of resting energy demand
2. Accessory breathing muscles - recruiting these muscles greatly increases the energy demands of respiratory movements. Usually only used when oxygen demand is high

Question 6

What is respiratory minute volume (V_E)?

Answer 6

Measures the amount of air that’s moved into the respiratory system per minute

This can be calculated directly from spirometry measurements

Question 7

What is anatomical dead space (V_D)?

Answer 7

It is the mix of used and fresh air due to inhaled and exhaled air in the conducting regions of the respiratory tract. This air cannot contribute to alveolar ventilation

V_D is calculated = V_T
(resting tidal volume) * 0.3

Question 8

What is alveolar ventilation (V_A)?

Answer 8

Measure of the amount of air that actually reaches the alveoli per minute

Question 9

What does anatomical dead space reduce?

Answer 9

It reduces the effective size of the breath that can actually be used for external respiration

ie. the amount that reaches respiratory portions of the tract

Question 10

What are the 2 components that contribute to lung inflation?

Answer 10

Compliance and resistance

Question 11

Describe compliance in relation to lung inflation

Answer 11

It is a measurement of how much work it takes to expand/inflate the lungs at a given pressure

More force required for lung inflation = lower compliance

Question 12

What are restrictive lung diseases?

Answer 12

They are diseases of reduced compliance. They can be caused by changes in the respiratory system or thoracic cage

A person with this type of disease is unable to fully fill their lungs. At rest, it requires more work to achieve the same volume of air inspired

Question 13

Name 2 examples of restrictive lung diseases

Answer 13

1. Respiratory distress syndrome - caused by reductions or absence of surfactant
2. Arthritis or other disorders of rib articulations

Question 14

How can restrictive lung disease be detected and how is it characterized?

Answer 14

It can be detected in spirometry by reduced FVC or TLC - forced vital capacity; total lung capacity

Restrictive lung disease is characterized by lower capacity for air

Question 15

Describe resistance in relation to lung inflation

Answer 15

It is a measurement of how much force is needed to make air flow through conducting pathways

The diameter of airway passages is a major determinant of the overall resistance (and bronchioles are the biggest contributors)

Question 16

Name 2 examples of obstructive lung diseases

Answer 16

1. Asthma - caused by airway inflammation and bronchoconstriction
2. Chronic bronchitis/chronic obstructive pulmonary disease - caused by inflammation leading to overproduction of mucus that clogs airways

In these diseases, conducting pathways to lung tissue are obstructed, reducing flow rate. A patient must do more work to get air to and from the lungs in a set time

Question 17

How can obstructive lung diseases be detected and how is it characterized?

Answer 17

In spirometry, by changes to forced expiratory rate

They are characterized by slightly increased residual capacities

Question 18

What is emphysema?

Answer 18

It is a lung disease caused by the destruction of respiratory tissue. It is the result of prolonged inflammation and/or exposure to toxic particulates in air, which triggers destruction of lung tissue, especially elastic fibres in alveoli walls. We also lose alveolar surface area

Question 19

What is the most common cause of emphysema?

Answer 19

Smoking - this also elevates risk of developing lung cancer

Question 20

How does emphysema affect the compliance and elastic recoil of the lung?

Answer 20

It increases compliance for inflation, but it reduces the elastic recoil of the lung. The lungs are easier to inflate because of less tissue in the alveolar wall, but the loss of elastic tissue in alveoli means exhalation is comparatively harder work than normal

Question 21

How does emphysema affect resistance? Which lung disease is emphysema similar to? Which muscles are used during quiet breathing with emphysema, which are not usually used?

Answer 21

It increases resistance because of the loss of elasticity

Ventilation effects resemble those seen in obstructive lung disease because exhalation if more affected than inhalation by the loss of elasticity

The patient has to do more work to achieve the same volume of air exhaled (expiratory muscles are used even during quiet breathing because of loss of elasticity)

Question 22

How does emphysema affect respiration rate?

Answer 22

It leads to reduction of gas exchange surfaces, which leads to an increase in respiration rate

Question 23

Give 3 reasons why respiration rate increases due to emphysema

Answer 23

1. A loss of gas exchange surfaces is equivalent to increased dead space in the lungs
2. CO2 cannot be removed because used air is trapped in the lungs due to the lack of elastic recoil
3. Respiration rate increases to maintain blood PO2 and reduce PCO2 through chemoreceptor reflexes