Respiratory Lab

Question 1

Boyle’s law

Answer 1

pressure of gas in a closed container is inversely proportional to the container volume

Question 2

intrapleural pressure change

Answer 2

• intrapleural pressure is always subatmospheric
• before inhalation → ~4mmHg less than atmospheric (i.e. 760 mmHg)
• after inhalation → ~6mmHg less than atmospheric

Question 3

alveolar pressure change

Answer 3

• after inhalation -> ~2mmHg less than atmospheric (i.e. 758mmHg)
• after exhalation -> ~2mmHg greater than atmospheric

Question 4

forces in quiet breathing

Answer 4

• recoil of elastic fibres stretched during inhalation
• inward pull of surface tension due to film of alveolar fluid

Question 5

surfactant deficiency in premature infants

Answer 5

respiratory distress syndrome
many alveoli collapse at end of exhalation
great effort needed to reopen at inhalation

Question 6

emphysema

Answer 6

type of COPD
destruction of elastic fibres in walls of alveoli
poor elastic recoil
increased compliance
difficulty in exhalation

Question 7

rate of airflow

Answer 7

pressure difference / resistance

Question 8

respiratory frequency

Answer 8

~12 breaths a minute

Question 9

tidal volume

Answer 9

volume of one breath
~500mL
350mL reaches respiratory zone, 150mL remains in conducting airways

Question 10

minute ventilation

Answer 10

• tidal volume x respiratory frequency
• ~ 6L/min

Question 11

alveolar ventilation rate

Answer 11

• volume of air per minute that actually reaches respiratory zone
• 350mL x 12 breaths per minute
• 4200 mL/min

Question 12

FEV1.0

Answer 12

• forced expiratory volume in 1 second
• volume of air that can be exhaled from the lungs in one second with maximal effort following maximal inhalation
• COPD greatly reduces FEV1.0

Question 13

residual volume

Answer 13

• volume of air remaining in lungs following exhalation of expiratory reserve volume
• because subatmospheric intrapleural pressure keeps alveoli slightly inflated, and some air remains in noncollapsible airways
• ~1200mL in males, ~1100mL in females
• cannot be measured by spirometry

Question 14

minimal volume

Answer 14

volume in lungs when thoracic cavity is opened
rise in intrapleural pressure → atmospheric pressure pushes out some of residual volume

Question 15

peak flow meter

Answer 15

used to measure peak expiratory flow rate
in units Lmin-1

Question 16

main factors that contribute to peak flow rate

Answer 16

• age
• height
• sex

Question 17

peak flow rate of asthmatic vs nonasthmatic

Answer 17

• lower in asthmatic
• constricted bronchioles
• more resistance to air flow

Question 18

peak flow rate of young active smoker vs young non-smoker

Answer 18

• same/higher in smoker
• cough a lot
• stronger internal intercostal muscles
• more forceful exhalation

Question 19

peak flow rate of long term smoker vs non-smoker

Answer 19

• lower in long term smoker
• damage to lung tissue
• increased compliance/decreased elasticity
• difficulty exhaling

Question 20

vitalograph

Answer 20

dry spirometer
used to measure vital capacity (i.e. FVC)
can obtain forced expiratory volume in one second (i.e. FEV1.0) from graph
units are L

Question 21

FEV1.0/FVC ratio

Answer 21

represents proportion of vital capacity exhaled in first second
used in diagnosis of obstructive and restrictive lung disease
in healthy adults, should be 75-80%

Question 22

FEV1.0/FVC ratio in obstructive diseases

Answer 22

e.g. asthma, COPD, chronic bronchitis
increased airway resistance to expiratory flow -> FEV1.0 likely to be diminished
FVC may be decreased (i.e. premature closure of airway), may still be able to achieve comparable vital capacity
overall reduced FEV1.0/FVC ratio

Question 23

spirometer

Answer 23

aka respirometer
instrument used to measure lung volumes

Question 24

collins spirometer

Answer 24

wet spirometer
can measure tidal volume, inspiratory reserve volume, inspiratory capacity, expiratory reserve volume, vital capacity
cannot measure residual volume, functional residual capacity
respond slowly to changes in volume
can only estimate FEV1.0, less accurate than dry spirometer

Question 25

lung model

Answer 25

container -> ribcage
space inside container -> interpleural space
tube -> airway
valve -> degree of closure represents obstruction
spring -> diaphragm
hole in tube -> pneumothorax
balloon -> lungs

Question 26

manometers in lung model

Answer 26

measure pressure in airway and interpleural space
U-shaped tube filled with water
outside arm is open to atmosphere, inside arm is open to lung model
downward movement of liquid in outside arm -> negative pressure in model airway compared to atmospheric pressure

Question 27

pressure change in lung model airway during inspiraton and expiration, obstructed vs unobstructed

Answer 27

unobstructed
- inspiration and expiration -> 0mmHg, equalises immediately
obstructed
- inspiration -> pressure decreases, equalises slowly
- expiration -> pressure increases, equalises slowly

Question 28

intrapleural pressure when no active force is applied on chest wall, model vs human

Answer 28

model -> 0mmHg subatmospheric
human -> ~4mmHg subatmospheric, because of recoil forces and surface tension wanting to collapse lungs, and chest wall wanting to expand outwards

Question 29

pressure in airways vs intrapleural space during inhalation

Answer 29

airways -> 0mmHg subatmospheric
intrapleural space -> becomes more negative

Question 30

changes in intrapleural pressure during pneumothorax at rest, deep inspiration, forced expiration

Answer 30

all 0mmHg subatmospheric
intrapleural pressure = atmospheric pressure

Question 31

content inside interpleural space of model vs human and expandability

Answer 31

model -> air, expandable
human -> serous fluid, not expandable

Question 32

estimated volume of intrapleural space of lung model vs human

Answer 32

model -> 1-2.3L
human -> 1-2L

Question 33

inspiratory reserve volume

Answer 33

• additional air inspired when taking a deep breath
• ~3100mL in males, ~1900mL in females

Question 34

expiratory reserve volume

Answer 34

• additional air expired when breathing out forcefully
• ~1200mL in males, ~700mL in females