1- Respiratory Mechanics Flashcards
what are the major inspiratory muscles?
diaphragm & external intercostal muscles
what are the accessory muscles of inspiration?
sternocleidomastoid, scalenus, pectoral
(they only contract in forceful inspiration)
what are muscles of active expiration?
abdominal muscles & internal intercostal muscles
what lung volumes and capacities can be measured by spirometry?
- tidal volume (normal amount breathing in 1 breath)
- inspiratory reserve volume (extra volume that can breathe in if really try)
- expiratory reserve volume (the amount that’s left to breathe out after inspiratory capacity)
- inspiratory capacity (everything you can breathe in)
- vital capacity (everything that can be used)
what volumes and capacities can not be measured by simple spirometry?
- residual volume (the amount of breath that will never be breathed in or out)
- functional residual capacity (the residual volume & expiratory reserve volume)
- total lung capacity
*basically any capacity/volume involving residual volume
what is tidal volume and what is average value?
volume of air entering or leaving lungs during a single breath = 0.5L
what is inspiratory reserve volume (IRV)?
extra volume of air that can be maximally inspired over & above the typical resting tidal volume = 3L
what is expiratory reserve volume (ERV)?
extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume = 1L
what is residual volume (RV)?
minimum volume of air remaining in the lungs even after maximal expiration = 1.2 L
what is inspiratory capacity (IC)?
max volume of air that can be inspired at end of normal quiet expiration = 3.5 L
(inspiratory reserve volume + tidal volume)
what is functional residual capacity (FRC)?
volume of air in lungs at end of normal passive expiration = 2.2 L
(expiratory reserve volume + residual volume)
what is vital capacity? (IMPORTANT)
max volume of air that can be moved out during a single breath following max inspiration = 4.5 L
(inspiratory reserve volume + tidal volume + expiratory reserve volume)
what is total lung capacity?
total volume of air lungs can hold = 5.7 L
(vital capacity + residual volume)
when does residual volume increase?
residual volume = volume of air remaining in the lungs even after maximal expiration
increases when elastic recoil of lungs is lost (as less air can be released)
what is forced vital capacity? (FVC)
maximum volume that can be forcibly expelled from the lungs following a maximum inspiration
what is forced expiratory volume in 1 second (FEV1)?
volume of air that can be expired during the first second of expiration in an FVC (Forced Vital Capacity) determination
what is the normal FEV1/FVC ratio? and what is it?
normally more than 75%
= The proportion of the Forced Vital Capacity that can be expired in the first second = (FEV1/FVC) X 100%
when are dynamic lung volumes useful?
dynamic lung volumes = FEV1/FVC ratio
diagnosis of Obstructive and Restrictive Lung Disease
what is FEV1/FVC ratio if
a) asthma?
b) COPD?
a) <75%
b) COPD post-bronchodilator <70%
what is levels of Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1) and FEV1/FVC ratio be like in airway obstruction?
FVC = low or normal
FEV1= low
FEV1/FVC%
*problem mainly the low FEV1/FVC%
what is levels of Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1) and FEV1/FVC ratio be like in lung restriction?
FVC = low
FEV1 = low
FEV1/FVC% = normal
*mainly low FVC problem
what is levels of Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV1) and FEV1/FVC ratio be like in combination of obstruction & restriction?
FVC = low
FEV1 = low
FEV1/FVC% = low
*main problem low FVC and low ratio
what is primary determinant of airway resistance? (whats the main thing that can show whether resistance)
radius of the conducting airway
with airway resistance is expiration or inspiration more difficult?
Expiration is more difficult than inspiration
what can alter airway resistance?
- Parasympathetic stimulation causes bronchoconstriction
- Sympathetic stimulation causes bronchodilation
- Disease states (e.g. COPD or asthma) can cause significant resistance to airflow
what is dynamic airway compression?
- increased airway resistance (by blockage etc) causes an increase in airway pressure
upstream (closer to mouth & nose). This increased pressure helps push air through and open the airways by increasing the the driving pressure between the alveolus and airway (i.e. the pressure downstream) - dynamic airway compression happens when airways trying to close during breathing out. the increased pressure from the increases airway resistance (above) helps prevent airway from completely closing (basically the body uses a bit of extra force(increased pressure) to make sure airways stay open when there’s resistance, especially during breathing out
*diseased airways are more likely to collapse
what is peak flow meter?
- gives an estimate of peak flow rate, it assess airway function
- especially useful for people with obstructive lung disease (asthma & COPD)
- measured by short sharp breath into meter
- best of 3 taken
- peak flow rate in normal adults vary with height & age
what is pulmonary compliance?
compliance is a measure of the effort that has to go into stretching or distending the lungs
= change in lung volume per unit in transmural pressure gradient across the lung wall (i.e. difference between intra-alveolar and intrapleural pressure)
- the less compliant the lungs are, the more work is required to produce a given degree of inflation
what factors can decrease pulmonary compliance?
pulmonary fibrosis, pulmonary oedema, lung collapse, pneumonia, absence of surfactant
what does decreased pulmonary compliance mean?
greater change in pressure is needed to produce a given change in volume (i.e. lungs are stiffer).
= This causes shortness of breath especially on exertion
= may cause a restrictive pattern of lung volumes in spirometry
what factors increase pulmonary compliance?
- elastic recoil of the lungs is lost
- in emphysema (Patients have to work harder to get the air out of the lungs – hyperinflation of lungs)
- also increases with age
what are some examples of times when work of breathing is increased?
- When pulmonary compliance is decreased
- When airway resistance is increased
- When elastic recoil is decreased
- When there is a need for increased ventilation
