Lecture 2 - Mechanics of breathing Flashcards Preview

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Flashcards in Lecture 2 - Mechanics of breathing Deck (37):
1

definition of breathing

bodily function that leads to ventilation of the lungs
also known as external respiration

2

Ventilation definition

Process of moving gases in - inspiration and out (expiration) of the lungs

3

Mechanics of breathing involves...

describes the structural and physiological bases of ventilation

4

in what 2 ways do diseases affect ventilation

obstructive conditions: asthma, COPD, lung cancer
Restrictive:
Intrinsic : pulmobary fibrosis
extrinsic: pneumothorax, disorders of thoracic skeleton

5

How will gas flow?

through patent airways according to the pressure gradient between atmosphere (barometric pressure) and alveoli

6

Pressure during inspiration

Pb (atmospheric pressure) is greater than alveolar pressure

7

Pressure during expiration

Aloveolar pressure (variable - Pa) is greater than the atmospheric pressure

8

Why does airway obstruction have a major effect on flow? describe in terms of the equation

flow = (k x delta PX r^4)/ (L)
As flow depends on the radius, airway obstruction would majorly affect it.

9

How is generation of Delta P brought about

atmospheric pressure is constant
therefore difference in pressure generation is dependent on the pressure changes in the chest

10

How does alveolar pressure changes related to thoracic volume

Change in pressure is inversely proportional to thoracic volume. The pressure is higher when the volume is low and vice versa

11

What are inspiratory muscles used in quiet breathing and when there is an increasing effort

quiet breathing: diaphragm
external intercostals stabilise rib cage

Increasing effort:
diaphragm
, external intercostals lift and expand rib cage, accessory muscles, neck muscles, shoulder girdle muscles

12

Expiratory muscles during quiet breathing and increasing effort

quiet breathing: elastic recoil of tissues

increasing effort: internal intercostals, abdominal wall muscles

13

what physical changes happen in inspiration

increased vertical diameter
increase A-P diameter
elevated rib cage
external intercostals contracted
internal intercostals relaxed
neck muscles contract

14

Expiration: physical changes

abdominals contracted

15

Innervation of diaphragm and intercostals

phrenic nerve - C3,4,5
Intercostals: segmental thoracic nerves

16

What can a spinal cord injury cause

ventricular muscle paralysis

17

What are the pleura responsible in doing

transmitting thoracic cage expansion into lung volume expansion
thoracic cage expansion exerts an increasing negative pressure on the intrapleural space

18

What does a spirometer measure

Volume of air moving in and out of the lungs

19

What is tidal volume

the volume of air moved in or out of the lungs during normal breathing.
at rest - 6-7 ml/kg
during exercise - 15 ml/Kg
Volumes dependent on age, sex and height
typical value of an adult male is 500 ml

20

Inspiratory reserve volume

after normal expiration, take as deep a breath as possible
typical value for 70 kg male - 3000 ml

21

Expiratory reserve volume

after normal inspiration, breath out as deeply as possible
1,500 ml for 70 kg male

22

What is residual volume

even after maximal expiration, air remains in the lungs. this is because of rigid nature of thorax and pleural attachments of the lungs to the chest wall that prevent complete emptying.

this volume left is residual volume
cannot be measured by spirometry
typical value is 1000 ml

23

Lung capacities

combinations of lung volumes

24

Total lung capacity

TV+IRV+ERV+RV

25

Vital capacity

TV+IRV+ERV

26

Functional residual capacity

ERV+RV

27

What is vital capacity

after a maximal inspiration, make a maximal expiration
typical value - 5,000 ml

28

Examples of chest diseases affecting lung volumes and capactities

Restrictive lung diseases - pulmonary fibrosis - reduced Residual volume, FRC, VC, TLV
Obstructive - asthma, copd, emphysema,
increased RV, TLC may be reduced or increased
FRC increased in emphysema

29

what is measured clincally using a vitalograph spirometer

forced expiratory measurements
FVC, Forced expiratory volume in 1 second (FEV1)

30

What is a peak flow meter used to measure

peak expiratory flow rate

31

How do you distinguish between obstructive and restrictive clinically?

FEV1/FVC ratio
ratio below 0.7 - obstructive
ratio above 0.7 - restrictive

32

Peak expiratory flow rate

convenient way of measuring airways obstruction, not as good as spirometry for airflow limitation
can use it at home to monitor asthma or copd
wide diurnal variations - highest in the evenings and lowest in early hours
PEFR - less depenent on effort than FEV1

33

Reversibility of airflow limitation

In asthma, the airway constriction is reversible so that FEV1 and PEFR would be restored to normal after salbutamol.

34

when is airways constriction irreversible?

COPD

35

what provides additional information about pulmonary disease

flow-volume loops

36

What is FEV1?

The fraction of the vital capacity expired during the first second of forced respiration.

37

When can it be reduced even when vital capacity is normal?

in diseases like asthma when airway resistance is increased because of bronchial constriction.