overview of respiration and respiratory mechanics (R2)

Question 1

accessory musces of inspiration

Answer 1

(contract only during forceful inspiration)

• sternocleidomastoid
• scalenus

Question 2

muscles of active inspiration

Answer 2

(contract only during active inspiration)

• internal intercostal muscles
• abdominal muscles

Question 3

major muscles of inspiration

Answer 3

(contract every inspiration; relaxation causes expiration)

• external intercostal muscles
• diaphragm
• (ribs and sternum are also involved)

Question 4

tidal volume (TV)

Answer 4

• volume of air entering or leaving the lungs during a single breath
• average value = 500ml

Question 5

inspiratory reserve volume (IRV)

Answer 5

• extra volume of air that can be maximally inspired over and above the typical resting tidal volume
• average value = 3000ml

Question 6

inspiratory capacity (IC)

Answer 6

• maximum volume of air that can be inspired at the end of a normal quiet expiration (IC=IRV+TV)
• average value = 3500ml

Question 7

expiratory reserve volume (ERV)

Answer 7

• extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume
• average value = 1000ml

Question 8

residual volume (RV)

Answer 8

• minimum volume of air remaining in the lungs even after a maximal expiration
• average value = 1200ml

Question 9

functional residual capacity (FRC)

Answer 9

• volume of air in lungs at end of normal passive expiration (FRC = ERV + RV)
• average value =2200ml

Question 10

vital capacity (VC)

Answer 10

-maximum volume of air that can be moved out during a single breath following a maximal inspiration
(VC = IRV + TV + ERV)
-average value = 4500ml

Question 11

total lung capacity (TLC)

Answer 11

-maximum volume of air that the lungs can hold
(TLC = VC =RV)
-average value = 5700ml

Question 12

forced expiratory volume in one second (FEV1): Dynamic Volume

Answer 12

• volume of air that can be expired during the first second of expiration in an FVC (forced vital capacity)
• average volume = FEV1%= FEV1/FVC ratio, normally >75%

Question 13

factors that affect normal predicted values of lung volumes and capacities

Answer 13

age, gender, height etc

Question 14

spirometry definition/ function

Answer 14

-common office test used to assess how well your lungs work by measuring how much air you inhale, how much you exhale and how quickly you exhale. Spirometry is used to diagnose asthma, chronic obstructive pulmonary disease (COPD) and other conditions that affect breathing

Question 15

spirometry for dynamic lung volumes (volume time curve)

Answer 15

allows you to determine;

• FVC
• FEV1
• FEV1% (FEV1/FVC ratio)

Question 16

effect of lung diseases on spirometry results

Answer 16

• airway obstruction causes low/normal FVC, low FEV1, and low FEV1/FEC%
• lung restriction causes low FVC, low FEV1 and normal FEV1/FVC%
• combination of obstruction and restriction causes low FVC, low FEV1 and low FEV1/FVC%

Question 17

airway resistance

Answer 17

• F=change inP/R (where F=flow, P=pressure, R=resistance)

- resistance to flow in the airway normally is very low and therefore air moves with a small pressure gradient

Question 18

primary determinant of airway resistance

Answer 18

radius of conducting airway

Question 19

what effect does parasympathetic stimulation have of the bronchi

Answer 19

bronchoconstriction

Question 20

what effect does sympathetic stimulation have on the bronchi

Answer 20

bronchodilatation

Question 21

what can cause significant resistance to airflow

Answer 21

disease states(e.g COPD/chronic obstructive pulmonary disease or asthma)

Question 22

which stage of breathing is most difficult to carry out

Answer 22

expiration

Question 23

what happens to intrapleural pressure during inspiration

Answer 23

falls

Question 24

what happens to intrapleural pressure during expiration

Answer 24

rises

Question 25

dynamic airway compression in normal people

Answer 25

- causes no problems - the rising pleural pressure during active expiration compresses the alveoli and airway - pressure applied to the alveoli helps to push air out of lungs - the pressure applied to the airway is not desirable-tends to compress it - the increased airway resistance causes an increase in airway pressure upstream, this helps to open the airways by increasing the driving pressure between the alveolus and the airway (ie. the pressure downstream)

Question 26

dynamic airway compression during active expiration in patients with airway obstruction

Answer 26

- if there is an obstruction (eg. asthma or COPD), the driving pressure between the alveolus and airway is lost over the obstructed segment, this causes a fall in airway pressure along the airway downstream resulting in airway compression by the rising pleural pressure during active expiration - diseased airway are also more likely to collapse - the problem becomes worse if the patient also has decreased elastic recoil of the lungs (eg. a patient with emphysema and obstructed airway caused by COPD)

Question 27

peak flow meter

Answer 27

-gives an estimate of peak flow rate, which assesses airway function - test is useful in patients with obstructive lung disease (eg. asthma and COPD) -measured by patient giving short sharp blow into the peak flow meter (average of 3 attempts is usually taken)

Question 28

peak flow rate in normal adults

Answer 28

varies with age and height

Question 29

pulmonary compliance

Answer 29

(during inspiration the lungs are stretched) - compliance is the measure of effort that has to go into stretching or distending the lungs - it is the volume change per unit of pressure change

Question 30

factors that decrease pulmonary compliance

Answer 30

pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant

Question 31

what is the effect of decreased pulmonary compliance

Answer 31

- the less compliant the lungs are, the more work is required to produce a given degree of inflation/ greater change in pressure is needed to produce a given change in volume (ie. lungs are stiffer) - this causes shortness of breath especially on exertion

Question 32

effect of decreased pulmonary compliance on spirometry

Answer 32

may cause restrictive pattern of lung volumes (FVC is less)

Question 33

what can cause increased pulmonary compliance

Answer 33

- may become abnormally increased if the elastic recoil of the lungs is lost - increased pulmonary compliance occurs in emphysema, patients have to work harder to get the air out of the lungs (hyperinflation of the lungs) - compliance also increases with age

Question 34

what is effected in patients with obstructed airway and emphysema caused by COPD

Answer 34

- dynamic airway compression is aggravated | - pulmonary compliance is increased(?)

Question 35

normal work of breathing

Answer 35

- normally requires 3% of total energy expenditure for quiet breathing - lungs normally operate at about "half full"

Question 36

what situations increase the work of breathing

Answer 36

- decrease in pulmonary compliance - increase in airway resistance - decrease in elastic recoil - a need for increased ventilation