ALS Lecture 6 - Physiological Consequences of Restrictive Lung Disease DONE Flashcards
breathing control flow chart
medulla -> spinal cord -> spinal nerves C3, C4, C5 -> respiratory muscles
respiratory drive
occurs from brain, conscious and unconscious
ventilation depends on (3)
chest wall, airway resistance, lung compliance
diffusion (gas exchange)
gas crosses alveolar walls
perfusion (2)
blood’s oxygen carrying capacity (Hb), pulmonary circulation
inspiration muscles (3)
diaphragm, intercostals, sometimes accessory
expiration muscles (3)
diaphragm, intercostals, sometimes accessory
expiration muscles if breathing with increased drive (2)
internal intercostals, abdominal muscles
compliance is the measure of the lung’s abilitiy to
stretch and expand (distensibility of elastic tissue)
ventilation is the exchange of air between
lungs, atmosphere
minute ventilation =
tidal volume x respiratory rate
minute ventilation is the amount of air
in and out of the lungs in a minute
normal RR
12-16 breaths per min
alveolar ventilation =
(tidal volume - dead space) x respiratory rate
alveolar ventilation is the amount of air
exchanged within alveoli
which is more important, minute or alveolar ventilation?
alveolar ventilation
only the ___ _____ of the lung is where you get _____, the rest is ____ ____
very bottom, perfusion, dead space
label the ventilation diagram
done
ventilation homeostasis is a balance between
ventilatory capacity, ventilatory demand
ventilatory capacity is the maximum spontaneous ventilation that can be maintained
without development of respiratory muscle fatigue
ventilatory capacity put simply is how much you can
breathe in and out without respiratory muscle fatigue
ventilatory demand is the amount of
breathing needed to maintain normal PaCO2
Fick’s law of diffusion: rate of transfer of gas through a sheet of tissue is proportional to
tissue area, difference in gas partial pressure
rate of transfer of gas through a sheet of tissue is inversely proportional to
tissue thickness
diffusion is greater with (3)
larger SA, larger pressure gradient, smaller distance to diffuse across
label the diagram of diffusion
done
CO2 diffuses across the membrane ___ more rapidly than O2
20x
capillary transit time
how long blood is in capillaries
perfusion is the blood that
reaches alveoli via capillaries
maximal perfusion occurs at the lung bases when upright because of
gravity
hypoxic pulmonary vasoconstriction is a physiological mechanism to match
perfusion and ventilation
hypoxic pulmonary vasoconstriction - if we get a hypoxic area within lungs, blood vessels
restrict to send blood to better supplied areas, so blood still gets oxygenated
idiopathic pulmonary fibrosis involves (3)
small lungs, reduced compliance, thickened alveolar membrane
in idiopathic pulmonary fibrosis, FEV1/FVC ratio is
preserved (>70%)
look at the graphs and tables of idiopathic pulmonary fibrosis and the details with it
done
in idiopathic pulmonary fibrosis CXR shows
more prominent shadows in lower lung
in idiopathic pulmonary fibrosis CT scan shows
honeycomb cysts
look at the examples of arterial blood gases in idiopathic pulmonary fibrosis
done
hypoxaemia (low PaO2) and normal PaCO2 indicates
type 1 respiratory failure
mean age of idiopathic pulmonary fibrosis presentation
71
idiopathic pulmonary fibrosis male:female ratio is approx
2:1
idiopathic pulmonary fibrosis mean survival is
3.9 years
label the diagram of the different prognoses of idiopathic pulmonary fibrosis
done
3 common prognoses of idiopathic pulmonary fibrosis
rapid progression to death, slow progression with acute attacks which are usually fatal, stable with acute attacks
examples of pharmacological management of idiopathic pulmonary fibrosis
- pirfenidione, antifibrotic
- nintedanib, tyrosine kinase inhibitor
supportive management for idiopathic pulmonary fibrosis (4)
oxygen, pulmonary rehab, breathlessness management, transplant
obstructive lung disease
obstructed flow of air, affects ventilation
restrictive lung disease
chest volume restricted, increased work of breathing
examples of obstructive lung disease (4)
asthma, COPD, bronchiectasis, other airway disease
examples of restrictive lung disease (4)
pulmonary fibrosis, obesity, chest wall deformities, neuromuscular deformities
label the spirometry graph showing, normal, obstructive and restrictive patterns
done
normal FEV1/FVC
> 70%
obstruction spirometry pattern (3)
normal FVC, reduced FEV1, reduced FEV1/FVC ratio (<70%)
restriction spirometry pattern (3)
reduced FEV1, FEV1/FVC ratio almost normal (>70%)
during inspiration diaphragm
contracts, flattens, moves down
during inspiration ribcage
pulled up and out
during inspiration external intercostal muscles
contract
during inspiration internal intercostal muscles
relax
during inspiration airways are
pulled open
during inspiration pressure on outside is
greater than inside, air moves in
label the diagram of inspiration and expiration
done
during expiration diaphragm
relaxes, moves up
during expiration ribcage
moves down and in
during expiration external intercostal muscles
relax
during expiration internal intercostal muscles
contract
during expiration, airways are
compressed
during expiration, pressure on inside is
greater than outside, air moves out
if airways are narrowed already, they get even more
compressed, takes a long time to breathe out, decreased FEV1
in obstructive lung disease, FEV1 is
reduced
in obstructive lung disease, FVC is
preserved
in obstructive lung disease, FEV1/FVC ratio is
reduced, <70%
gas trapping happens in
obstructive lung disease
gas trapping
airways close on expiration, parts of lungs get gas trapped
in obstructive lung disease, diffusion is
normal (except in emphysema)
in obstructive lung disease, perfusion is
normal (end stage can lead to cor pulmonale)
in early asthma, Type 1 respiratory failure PaO2 is
low
in early asthma, Type 1 respiratory failure PaCO2 is
low
in early asthma, Type 1 respiratory failure HCO3+ is
normal
in early asthma, Type 1 respiratory failure pH is
low
in late severe asthma, Type 2 respiratory failure PaO2 is
low
in late severe asthma, Type 2 respiratory failure PaCO2 is
high
in late severe asthma, Type 2 respiratory failure HCO3 is
normal
in late severe asthma, Type 2 respiratory failure pH is
low
in COPD, Type 1 respiratory failure PaO2 is
low
in COPD, Type 1 respiratory failure PaCO2 is
normal
in COPD, Type 1 respiratory failure HCO3+ is
normal
in COPD, Type 1 respiratory failure pH is
normal
in COPD, Type 2 decompensated respiratory failure PaO2 is
low
in COPD, Type 2 decompensated respiratory failure PaCO2 is
high
in COPD, Type 2 decompensated respiratory failure HCO3+ is
normal
in COPD, Type 2 decompensated respiratory failure pH is
low
in COPD, Type 2 compensated respiratory failure PaO2 is
low
in COPD, Type 2 compensated respiratory failure PaCO2 is
high
in COPD, Type 2 compensated respiratory failure HCO3+ is
high
in COPD, Type 2 compensated respiratory failure pH is
normal
label the diagram of the spirometry graph
done
label the diagram of the spirometer
done
FVC
forced vital capacity, where volume plateaus, can’t blow any more
FEV1
forced expiratory volume in 1 second
in spirometry the patient
blow out hard and fast, trying to empty lungs
FEV1/FVC should be
> 70%
label the diagram of the helium dilution method
done
helium dilution method (3 steps)
- known conc of helium in tank
- pt breathes in then out
- calculate change in conc to find lung volume
flow rate
how quickly we can breath in and out
flow rate tells us about
airway resistance
Poiseuille’s law (for laminar flow)
resistance = inversely proportional to radius4
peak flow steps (3 steps)
- pt blows hard and fast into tube 3 times
2. smallest reading taken
flow volume loop shows us
rate of flow, dependent on volume
label the flow volume loop table
done
as we start to breathe out hard and fast, the flow volume loop curve
rises steeply
DLCO stands for
diffusion capacity of the lung for carbon monoxide
how do we measure DLCO? (4 steps)
- pt inspires air mix with CO
- 10 second breath-hold
- conc change is proportional to thickness of alveolar membrane
why do we use CO in DLCO?
CO taken up by Hb
respiratory rate
count breaths for 30secs, times by 2
normal PaO2 (10-12kPa), Hb is saturated by oxygen to what percentage?
95%
at PaO2 of about 8kPa, Hb is saturated by oxygen to what percentage?
90%
below 90% oxygen saturation, oxygen delivery is
markedly compromised
if O2 sats are below 90-92%, what is indicated?
blood gas measurement by arterial puncture
label the oxygen dissociation curve
done
when O2 saturations are above ~96% it doesn’t matter
how much you raise PaO2
a small decrease in PaO2 will cause a
massive fall in O2 saturation
2 types of restrictive lung disease
interstitial lung disease, chest wall deformities/neuromuscular disorders
interstitial lung disease increases the
distance gas has to diffuse across to get between air and blood
FEV1 in restrictive lung disease
reduced
FVC in restrictive lung disease
reduced
FEV1/FVC ratio in restrictive lung disease
normal or raised
PaO2
partial pressure of O2 in arterial blood
PaCO2
partial pressure of CO2 in arterial blood
raised PaCO2 indicates
type 2 respiratory failure
type 1 respiratory failure is
hypoxaemic, low paO2, low/normal PaCO2
type 2 respiratory failure is
hypercapnic, low PaO2, high PaCO2
label the acid-base balance diagram and the details below
done
hypoxia can be caused by (3)
impaired diffusion, hypoventilation, V/Q mismatch
2 types of V/Q mismatch
- normal ventilation, decreased perfusion
- normal perfusion, decreased ventilation
possible causes of decreased perfusion
right to left cardiac shunt, pulmonary emboli, not usually restrictive or obstructive
label the diagram of decreased perfusion
done
possible causes of decreased ventilation
pneumonia, pneumothorax, obstructive lung diseases (e.g. asthma)
label the diagram of decreased ventilation
done
