Mechanics of Breathing

Question 1

what proportion of the deaths are attributable to respiratory disease

Answer 1

36%

Question 2

what is the definition of breathing

Answer 2

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

Question 3

define ventilation

Answer 3

the process of moving gases in and out of the lungs

Question 4

define mechanics of breathing

Answer 4

decries the structural and physiological bases of ventilation

Question 5

what are the two types of disease affecting ventilation and what are some examples

Answer 5

obstructive conditions:
asthma, COPD, lung cancer
restrictive conditions: intrinsic: pulmonary fibroids
extrinsic - pneumothorax, disorders of the thorax skeleton

Question 6

what is the difference in barometric pressure during inspiration and expiration between the atmosphere and the alveoli

Answer 6

inspiration: Pb (atmospheric pressure) > Pa (alveolar pressure)
expiration: Pa > Pb

Question 7

what is 1 atm of pressure equal to in terms of kPa, bar, mmhm and cmH20

Answer 7

1 atm = 101.3 kPa
= 1.013 bar
= 760 mmHg
= 1033 cmH2O

Question 8

what is a change in pressure dependant on

Answer 8

cycle of pressure changes in the chest

Question 9

according to boyles law what happens after thoracic volume changes

Answer 9

alveolar pressure changes

P = 1/V

Question 10

what are the difference sin muscle groups between quiet breathing and increasing effort

Answer 10

quiet = diaphragm and external intercostal muscle (inspiration)

increasing effort: accessory muscles involved such as neck muscles (pull rib cage up) and shoulder girdle muscles

Question 11

what happens in quiet breathing during expiration and increasing effort

Answer 11

quiet breathing = elastic recoil of tissue

increasing effort = internal intercostal muscles and abdominal muscle walls

Question 12

what innervates intercostals

Answer 12

segmenta thoracic nerves

Question 13

where does the diaphragm originate from

Answer 13

the neck and becomes a muscle therefore innervated by the cervical nerve

Question 14

what happens to the intrapleural space during thoracic cage expansion

Answer 14

causes an increasing negative pressure meaning air comes into lungs

Question 15

how does a traditional spirometer work

Answer 15

Measurement of the basic lung volumes and capacity
Counterbalanced using a weight
Cylinder down pen up
Breathes in pen moves up and vice versa

Question 16

what is tidal volume and its typical values

Answer 16

the volume of air moved in or out of the lungs during normal breathing
at rest: 6-7 ml/kg
exercise: 15 ml/kg

Question 17

what is the inspiratory reserve volume and what is its typical value

Answer 17

after normal expiration take as deep a breath as possible

70kg male - 3,000ml

Question 18

what is the expiatory reserve volume

and its typical value

Answer 18

after normal inspiration, breath out as deeply as possible

70 kg male - 1,500 ml

Question 19

which values on a spirometer do restrictive lung diseases affect

Answer 19

reduced RV, FRC, VC, TLC

Question 20

what do obstructive lung diseases such as asthma, COPD and emphysema affect

Answer 20

increased RV
TLC may be reduced in COPD but reduced in emphysema
FRC increased in emphysema

Question 21

what is FRC

Answer 21

functional residual capacity - dependant on the compliance of the lungs and chest wall

Question 22

what is compliance

Answer 22

defined as the change in lung volume per unit change in intrathoracic pressure
C = change in V/ change in pressure
if something is very compliant it means it doesn’t take much effort to stretch it

Question 23

what is the normal tendency of the lung

Answer 23

to collapse

Question 24

what is the calculation for recoil pressure of the lung

Answer 24

Palv - Ppl

Question 25

what is the recoil pressure of the lung at maximal expiration

Answer 25

0 - - 3 = +3 cmH2O

Question 26

what is the recoil pressure of the lung at peak inspiration

Answer 26

+ 30cmH2O

Question 27

what is the recoil pressure of then lung during tidal breathing

Answer 27

+5 cmH2O

Question 28

how do you calculate the recoil pressure of the chest wall

Answer 28

Ppl - Pbs (body surface)

Question 29

what are the three steps for measuring and calculating the recoil pressure of the chest wall

Answer 29

maximal expiration, close glottis, relax muscles | Ppl - Pbs = -30 - 0 = -30cmH2O

Question 30

what happens when we maximally expire in terms of the chest wall and intrapleural pressure

Answer 30

generates very negative intrapleural pressure and therefore chest wall wants to spring out for inspiration to occur

Question 31

describe the graph of a composite chest wall and lung compliance

Answer 31

at FRC the recoil pressure is 0 | FRC is the relaxation point of the respiratory system when chest wall and lung recoil pressures are equal but opposite

Question 32

what surgery is formed during circumferential burn

Answer 32

escharotomy

Question 33

how does scoliosis affect compliance

Answer 33

reduces compliance as ribs don't expand as well as they normally should

Question 34

what happens to compliance during emphysema

Answer 34

increases compliance as elastic tissue is destroyed meaning less want to recoil

Question 35

describe how gravity affects compliance throughput the length of the lungs

Answer 35

Spaces at the bottom are more closed off than those at the top Alveoli even at the bottom are not completely shut According to position in the lung alveoli have a difference in compliance – steeper curve at the bottom of the graph then flattens off at the top bigger change in the basal alveoli compared to the upper alveoli – upper don’t open that much – better ventilation at the bottom of the lungs ie when you breath the top alveoli don't stretch that much as they are already quite open

Question 36

what is closing capacity

Answer 36

The closing capacity is the volume in the lungs at which its smallest airways, the respiratory bronchioles, collapse

Question 37

what happens if the closing capacity exceeds FRC

Answer 37

alveoli independent lung regions will be poorly ventilated

Question 38

what happens to alveoli when FRC is smaller than closing capacity

Answer 38

you get closure of some of the alveoli

Question 39

does closing capacity ever change

Answer 39

no

Question 40

what is the equation for the law of laplace

Answer 40

Pressure = (2 x Thickness x Tension)/Radius

Question 41

how can tension within a sphere be decreased at constant pressure

Answer 41

increasing the thickness of the sphere wall

Question 42

how does surface tension work

Answer 42

potential energy is minimised through reducing surface area to volume ratio by formation of a sphere

Question 43

what specifically is the role of surfactant

Answer 43

``` Acts as a detergent to reduce alveolar surface tension Increases pulmonary compliance Prevents atelectasis Aids alveolar recruitment Minimises alveolar fluid ```

Question 44

which syndrome causing less surfactant

Answer 44

infant respiratory distress

Question 45

what cells produce surfactant

Answer 45

type 2 alveolar cells

Question 46

what is the composition of surfactant

Answer 46

90% phospholipid 10% protein

Question 47

what happens to surfactant as alveolar volume increases

Answer 47

becomes more dispersed which equalises pressure between alveoli of different sizes ie there is less tension from spread out surfactant in larger sized alveoli

Question 48

what is it called when the relationship between he intrathoracic pressure and the lung volume during tidal breathing

Answer 48

hysteresis

Question 49

what causes hysteresis

Answer 49

at small lung volumes: reduced compliance airway calibre

Question 50

what is the equation for flow in the lungs

Answer 50

Flow = (k.change in P.r^4)/L

Question 51

define laminar and terminal flow

Answer 51

Laminar flow is where the air is flowing through the tube in parallel layers, with no disruption between the layers, and the central layers flowing with greater velocity. Turbulent flow is when the air is not flowing in parallel layers, but direction, velocity and pressure within the flow of air become chaotic.

Question 52

which flows are where in the lungs

Answer 52

upper alveoli more turbulent flow | laminar flow in lower branches

Question 53

what does a vitalograph spirometer do

Answer 53

measures the forced vital capacity FVC | the forced expiratory volume in 1 second (FEV1)

Question 54

what does a peak flow meter measure

Answer 54

PEFR

Question 55

what causes reduction in FVC and FEV1

Answer 55

COPD (obstructive defect) | Restrictive defect such as pulmonary fibrosis

Question 56

what does the FEV1/FVC ratio distinguish between

Answer 56

obstructive and restrictive conditions ratio < 0.7 = obstructive ration > 0.7 = restrictive

Question 57

what is the difference between asthma and chronic obstructive lung disease

Answer 57

asthma airways are reversible via B adrenorecpetor agonist salbutamol COPD is irreversible

Question 58

what is the work of breathing

Answer 58

the energy used in inspiration to overcome elastic forces is stored as potential engird which is dissipated in expiration work is expended in the form of heat during inspiration and expiration to overcome resistance forces

Question 59

what is the equation for work

Answer 59

volume x pressure

Question 60

what happens to minimal work of breathing in restrictive and obstructive conditions

Answer 60

restrictive: work is minimised with rapid volume small volume breaths obstructive work is minimised with large volume slow breaths