Respiration: mechanics

Question 1

What are the two meanings of respiration?

Answer 1

tissue respiration and breathing

Question 2

tissue respiration definition

Answer 2

the aerobic metabolism in cells

Question 3

breathing definition

Answer 3

gas exchange and the associated processes

Question 4

respiratory mechanics definition

Answer 4

study of mechanical properties of the lung and chest wall and the process by which air enters and leaves the lungs

Question 5

Function of the lungs

Answer 5

bring in oxygen rich air to fuel the body and to expel waste gas (CO2)

Question 6

Function of breathing

Answer 6

maintain blood gas homeostasis (O2, CO2, pH)

Question 7

What must the movement of air in and out of the lungs be coupled with?

Answer 7

cellular respiration

Question 8

What are the partial pressures of O2 and CO2 at rest?

Answer 8

PO2 = 100+-2 mmHg
PCO2 = 40+-2 mmHg

Question 9

Volume of O2 and CO2 exchanged at rest

Answer 9

250ml O2/min and 200ml CO2/min

Question 10

Volume of O2 and CO2 exchanged when walking

Answer 10

800ml O2/min and 750ml CO2/min

Question 11

Volume of O2 and CO2 exchanged during severe exercise

Answer 11

5000ml O2/min and 6000ml CO2/min (due to more anaerobic respiration)

Question 12

Which structures does air flow through to reach the lungs?

Answer 12

nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, alveoli

Question 13

Which structures are regarded as the upper airways?

Answer 13

nasal cavity, pharynx, larynx

Question 14

Major functions of the upper airway

Answer 14

humidify (saturate with water), warm (to body temp) and filter the air

Question 15

Which epithelium lines the upper airways to the bronchioles?

Answer 15

pseudostratified ciliated columnar epithelium

Question 16

How is inhaled air filtered?

Answer 16

particles become trapped in mucus which is wafted by cilia to the pharynx to be coughed out.

Question 17

Function of goblet cell

Answer 17

produce mucus that forms a layer over the cilia

Question 18

Ventilation at rest

Answer 18

6-7 L/min (12-15 breaths of 500ml)

Question 19

Max ventilation

Answer 19

160L/min (40 breaths of 4L)

Question 20

Cardiac output at rest

Answer 20

5 L/min (70bpm, 70ml/beat)

Question 21

Max cardiac output

Answer 21

25 L/min (200bpm, 125ml/beat)

Question 22

Description of inspiration during quiet breathing

Answer 22

active - diaphragm contracts downwards, pushing abdominal contents outwards. External intercostal muscles pull ribs outwards and upwards

Question 23

Description of expiration during quiet breathing

Answer 23

passive - elastic recoil

Question 24

Description of inspiration during strenuous breathing

Answer 24

active - greater contraction of diaphragm and external intercostal muscles. Inspiratory accessory muscles are active.

Question 25

Difference in diaphragm contraction in quiet and strenuous breathing

Answer 25

1cm in quiet breathing and 10cm in strenuous breathing

Question 26

Examples of inspiratory accessory muscles active during strenuous breathing

Answer 26

sternocleidomastoid, alae nasi, genioglossus

Question 27

Description of expiration during strenuous breathing

Answer 27

active - abdominal muscles active and internal intercostal muscles oppose external intercostals by pushing ribs down and inwards.

Question 28

Abdominal muscles active during expiration in strenuous breathing

Answer 28

rectus abdominus, internal oblique, external oblique, transverse abdominus

Question 29

What is the major inspiratory muscle?

Answer 29

Diaphragm

Question 30

What type of muscle is the diaphragm?

Answer 30

skeletal muscle

Question 31

What are the muscles of inspiration?

Answer 31

Sternocleidomastoid, scalenus, parasternal intercartilaginous muscles, external intercostals, diaphragm

Question 32

What are the muscles of expiration?

Answer 32

internal intercostals, abdominal muscles - rectus abdominis, external oblique, internal oblique, transversus abdominis

Question 33

What is pleural pressure (Ppl)?

Answer 33

the pressure between the lung and chest wall (pleural space)

Question 34

What is the elastic recoil pressure (Pel)?

Answer 34

The pressure exerted on the lung to return to the resting state

Question 35

What is the alveolar pressure (Pa)?

Answer 35

The pressure in the lungs

Question 36

What is the transpulmonary pressure (Pl)

Answer 36

The difference in pressure between the lung and the pleural space

Question 37

What is the alveolar pressure and the barometric pressure at the beginning of inspiration?

Answer 37

Pa=0, Pb=0 (so no flow)

Question 38

What are the pressure and volume changes during inspiration?

Answer 38

inspiratory muscles contract increasing the thoracic volume so Ppl becomes more negative. Pl (transpulmonary) increases which causes lungs to expand / alveolar volume to increase. Pa becomes negative (below Pb) so air flows in down the pressure gradient.

Question 39

What is the relation between Pa and Pb at the end of inspiration?

Answer 39

Pa=Pb (no flow - muscles stop contracting and expansion stops)

Question 40

Pressure and volume changes during expiration

Answer 40

thoracic volume decreases. Ppl and Pl return to pre-inspiration values. Thorax and lungs recoil (Pel). Air in alveoli compressed. Pa>Pb. Air flows out of lungs.

Question 41

What is the efficiency of breathing in healthy lungs?

Answer 41

very efficient, small muscle effort - 2% of resting energy expenditure

Question 42

Why is higher intensity breathing less efficient?

Answer 42

gas flow is turbulent and more muscles are being used. (accessory muscles fatigue easily, limiting exercise)

Question 43

What is a factor for developing respiratory failure?

Answer 43

respiratory muscle fatigue

Question 44

What is the functional residual capacity (FRC)?

Answer 44

the volume of air in the lung at the end of expiration during quiet breathing (ERV + RV)

Question 45

How does the elastic recoil forces of the lung impact lung volume?

Answer 45

Decrease lung volume

Question 46

How does the outward recoil of the chest wall impact lung volume?

Answer 46

Increase lung volume

Question 47

What is the relation of the elastic recoil forces of lung and outward recoil of chest wall at FRC?

Answer 47

Opposite and equal and muscles are relaxed

Question 48

How is the balance between the elastic recoil forces of the lung and outward recoil of chest wall disturbed?

Answer 48

By the contraction of respiratory muscles at the beginning of inspiration

Question 49

How can weak chest wall muscles (neuromuscular disease) affect the FRC?

Answer 49

FRC decreases as lung elastic recoil is greater

Question 50

What is the tidal volume?

Answer 50

Volume of air that moves in and out of lung in one resting breath

Question 51

What is the name of the volume of air that cannot be forced out of the lungs?

Answer 51

residual volume

Question 52

What is the expiratory reserve volume (ERV)?

Answer 52

the volume of air that can be forced out at the end of passive exhalation

Question 53

What is the total lung capacity?

Answer 53

The maximum volume of air that can be taken into lungs

Question 54

How can lung volume be measured?

Answer 54

Using a vitalograph or spirometer

Question 55

Why is it important to measure lung volumes?

Answer 55

To understand normal and diseased lung function