mechanics of breathing

Question 1

Pulmonary ventilation consists of which two phases?

Answer 1

• inspiration
• expiration

Question 2

Define intrapulmonary pressure

Answer 2

• Ppul is the pressure within the alveoli

Question 3

What pressure prevents the lungs from collapsing?

Answer 3

• Transpulmonary pressure

Question 4

How is transpulmonary pressure calculated?

Answer 4

Intrapulmonary pressure (Ppul) - Intrapleural pressure (Pip)

Question 5

List the muscles of normal respiration

Answer 5

• Diaphram
• intercostal muscles

Question 6

Name the physical factors influencing pulmonary ventilation

Answer 6

• Airway resistance
• Alveolar surface tension
• Lung compliance

Question 7

Name the four respiratory volumes

Answer 7

• tidal volume
• inspiratory reserve volume
• expiratory reserve volume
• residual volume

Question 8

Define vital capacity

Answer 8

Vital capacity = total sum of IRV + ERV + TV

Question 9

Define dead space

Answer 9

Amount of inspired air within the conducting zone that does not participate in gaseous exchange

Question 10

Define intrapleural pressure

Answer 10

Pip = the pressure within the pleural cavity

Question 11

Define total lung capacity

Answer 11

• TLC is the maximum volume of air contained in the lungs after maximum inspiratory effort
• TLC = TV + ERV + IRV + RV

Question 12

Define Functional residual capacity

Answer 12

• FRC is the sum of Expiratory reserve volume and Reserve volume
• the volume of air remaining in the lungs after normal tidal expiration

Question 13

Define minute volume

Answer 13

• MV is the volume of air inspired and expired in a minute
• MV = TV x RR

Question 14

Define alveolar minute volume

Answer 14

• Alveolar ventilation rate = RR x (TV - dead space)

Question 15

Define nonrespiratory air movements

Answer 15

Nonrespiratory air movements are voluntary or reflex actions that clear the respiratory passageway or express emotions

Question 16

What respiratory group of the respiratory centre controls inspiration?

Answer 16

Dorsal respiratory group

Question 17

Which muscles of respiration does the Dorsal respiratory group control?

Answer 17

• Diaphragm
• External intercostal muscles

Question 18

What nerves are responsible for initiating ventilation?

Answer 18

• Phrenic nerves
• Intercostal nerves

Question 19

Describe phase 1 of inspiration

Answer 19

• inspiratory muscles contract
• diaphragm moves down
• thoracic cavity expands and volume increases

Question 20

Describe phase two of inspiration

Answer 20

• intrapulmonary pressure decreases by 1mmHg
• air flows into the lungs along the pressure gradient until Ppul = Patm

Question 21

Describe phase 1 of expiration

Answer 21

• inspiratory muscles relax
• diaphragm rises
• thoracic cavity recoils and volume decreases

Question 22

Describe phase 2 of expiration

Answer 22

• thoracic recoil causes an increase in intrapulmonary pressure by 1mmHg
• air flows out of the lungs down the pressure gradient until Ppul = Patm

Question 23

What is the normal value for tidal volume?

Answer 23

500ml

Question 24

True or false? Adult males and females have the same total lung capacity

Answer 24

False

Question 25

What is the value for normal intrapleural pressure?

Answer 25

756mmHg

Question 26

In which air passages does the greatest resistance to airflow occur?

Answer 26

Medium-sized bronchi

Question 27

Which factors diminish compliance?

Answer 27

• reduced natural resiliance of lungs
• blocked small respiratory passages
• reduced surfactant production
• decreased flexibility/expandability of thoracic cage

Question 28

What device is used in hospital to measure a patient’s lung volume and capacity?

Answer 28

A spirometer

Question 29

Define Boyle’s law

Answer 29

At a constant temperature , the pressure of a gas varies inversely with its volume

P1V1 = P2V2

Question 30

How do you calculate physiological dead space?

Answer 30

anatomical dead space + alveolar dead space