Respiratory Lab Flashcards
Boyle’s law
pressure of gas in a closed container is inversely proportional to the container volume
intrapleural pressure change
- intrapleural pressure is always subatmospheric
- before inhalation → ~4mmHg less than atmospheric (i.e. 760 mmHg)
- after inhalation → ~6mmHg less than atmospheric
alveolar pressure change
- after inhalation -> ~2mmHg less than atmospheric (i.e. 758mmHg)
- after exhalation -> ~2mmHg greater than atmospheric
forces in quiet breathing
- recoil of elastic fibres stretched during inhalation
- inward pull of surface tension due to film of alveolar fluid
surfactant deficiency in premature infants
respiratory distress syndrome
many alveoli collapse at end of exhalation
great effort needed to reopen at inhalation
emphysema
type of COPD
destruction of elastic fibres in walls of alveoli
poor elastic recoil
increased compliance
difficulty in exhalation
rate of airflow
pressure difference / resistance
respiratory frequency
~12 breaths a minute
tidal volume
volume of one breath
~500mL
350mL reaches respiratory zone, 150mL remains in conducting airways
minute ventilation
- tidal volume x respiratory frequency
- ~ 6L/min
alveolar ventilation rate
- volume of air per minute that actually reaches respiratory zone
- 350mL x 12 breaths per minute
- 4200 mL/min
FEV1.0
- 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
residual volume
- 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
minimal volume
volume in lungs when thoracic cavity is opened
rise in intrapleural pressure → atmospheric pressure pushes out some of residual volume
peak flow meter
used to measure peak expiratory flow rate
in units Lmin-1
main factors that contribute to peak flow rate
- age
- height
- sex
peak flow rate of asthmatic vs nonasthmatic
- lower in asthmatic
- constricted bronchioles
- more resistance to air flow
peak flow rate of young active smoker vs young non-smoker
- same/higher in smoker
- cough a lot
- stronger internal intercostal muscles
- more forceful exhalation
peak flow rate of long term smoker vs non-smoker
- lower in long term smoker
- damage to lung tissue
- increased compliance/decreased elasticity
- difficulty exhaling
vitalograph
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
FEV1.0/FVC ratio
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%
FEV1.0/FVC ratio in obstructive diseases
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
spirometer
aka respirometer
instrument used to measure lung volumes
collins spirometer
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
lung model
container -> ribcage
space inside container -> interpleural space
tube -> airway
valve -> degree of closure represents obstruction
spring -> diaphragm
hole in tube -> pneumothorax
balloon -> lungs
manometers in lung model
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
pressure change in lung model airway during inspiraton and expiration, obstructed vs unobstructed
unobstructed
- inspiration and expiration -> 0mmHg, equalises immediately
obstructed
- inspiration -> pressure decreases, equalises slowly
- expiration -> pressure increases, equalises slowly
intrapleural pressure when no active force is applied on chest wall, model vs human
model -> 0mmHg subatmospheric
human -> ~4mmHg subatmospheric, because of recoil forces and surface tension wanting to collapse lungs, and chest wall wanting to expand outwards
pressure in airways vs intrapleural space during inhalation
airways -> 0mmHg subatmospheric
intrapleural space -> becomes more negative
changes in intrapleural pressure during pneumothorax at rest, deep inspiration, forced expiration
all 0mmHg subatmospheric
intrapleural pressure = atmospheric pressure
content inside interpleural space of model vs human and expandability
model -> air, expandable
human -> serous fluid, not expandable
estimated volume of intrapleural space of lung model vs human
model -> 1-2.3L
human -> 1-2L
inspiratory reserve volume
- additional air inspired when taking a deep breath
- ~3100mL in males, ~1900mL in females
expiratory reserve volume
- additional air expired when breathing out forcefully
- ~1200mL in males, ~700mL in females
