Pulm Flashcards
upper airway
nose
pharynx
glottis
vocal cords
2 subdivisions of lower airway and their generations+ volume
conducting- 16 gen, 150 mL
respiratory unit- 7 gen, 2.5 L
types of airflow and where it occurs
upper airway- turbulent
treachea through conducting- laminar
respiratory units - diffusion
what does the volume in the conducting airways represent and what do you use to measure it?
anatomic dead space; Fowler method (single breath nitrogen washout)
how do you measure residual volume?
1) Helium dilution (how deeply you breath in dilutes He in monitor)
2) body plethysmography
main muscle of inspiration + what its innervated by
diaphragm (phrenic, C3-C5)
4 lung volumes
tidal volume
expiratory reserve volume
inspiratory reserve volume
residual volume
4 lung capacities
TLC
FRC
IC
Vital capacity
why does air go into lung?
boyle’s law- P proportional to 1/v
what determines the volume of air in the lung?
1) lung compliance- delta v/delta p
2) interaction between lung (pulling in) and chest wall (pulling out)
what is special about the inflation compliance curve?
exhibits hysteresis due to high surface tension of alveoli at small volumes
trans-lung pressure
PL= Palveolar (0) - Ppleural (-5) = 5
pressure that keeps alveoli open
wall pressure
Pw= Ppleural (-5) - Pbarometric (0)= -5
respiratory pressure
Pr= alvolar pressure- barometric pressure= 0
at what point on the relaxation pressure curve are the pressures balanced?
at FRC- chest pull out equals lung pull in
describe the process of inspiration in terms of lung pressures
- diaphragm contracts
- pleural pressure (Ppl) becomes more negative (pulling air in)
- trans-lung pressure (Pa-Ppl) become more positive
- alveolar pressure becomes more negative, alveoli want to expand and pull air in
During quiet breathing, pleural pressure is always positive/negative
negative (-5 to -8)
Take away from the Hagen-Poiseuille equation explaining laminar flow & resistance
- resistance directly proportional to airway length/gas viscosity
- resistance inversely proportional to airway radius to the fourth power
four factors influencing airway resistance
decreased AWR with increased
1) lung volume
2) sympathetic stimulation
increased AWR with increased
1) vagal stimulation
2) mucus/edema/infection/smooth muscle contraction
what is flow limitation?
- at equal pressure point (abnormally outside cartilage), the pressure outside the airway (pleural) is greater than the pressure inside, can cause airway compression
- airflow becomes independent of total driving pressure (aka is FORCE INDEPENDENT)
- look at Palveolar-Ppleural (Plung)
- occurs with emphysema
- increase pressure in airways using purse lipped breathing
what does a dynamic lung function test measure? what do you want it to be?
FEV1/FVC
normal - >75%
what dynamic lung function result is low in asthma? what do you test?
low FEV1/FVC ratio
test if albuterol (beta 2 agonist) helps
how does pulmonary vascular resistance change with changes in pressure and why?
pulmonary vascular resistance decreases with increases in pressure b/c of
1) recruitment (more capillaries open up) and
2) distension (vessels are thin, can easily be expanded)
when is pulmonary vascular resistance lowest with respect to lung volume? what is it a balance between?
at FRC
- balance between alveolar and extra-alveolar vessels
- extra-alveolar vessels behave like lung tissue, expand with inhalation
intrapleural pressure is less negative at the bottom/top of the lung; alveoli at this point have a smaller/larger translung pressure (Pa-Ppl), how do they compensate?
bottom (more surface area, gravity)
- alveoli at base have smaller translung pressure, are smaller BUT have higher compliance, recieve more of the ventilation in lung
what does breathing at a smaller volume benefit?
alveoli at the top of the lung- have a negative translung pressure, are not collapsed like the ones at the bottom, sit at better part of compliance curve
where does most of the blood flow in the lungs go to?
the base- zone 3- alveolar dead space
Parterial>Pvenous>Palveolar
in what zone do you see the waterfall effect? what does this mean?
zone 2 Parterial>Palveolar>Pvenous
flow determined by difference between alveolar and arterial pressure
when does the ventilation-perfusion (V/Q) ratio equal 0?
- shunt alveolus
- aka you have blood flowing but no air
- you have a HIGH PCO2 in alveolus
- PO2 is very low in alveolus
when does the ventilation-perfusion (V/Q) ratio approach infinity?
- dead space alveolus
- aka you have air but no blood
- have HIGH PO2 in alveolus
- PCO2 is almost 0
what are the units for V/Q?
mL O2/mL blood
differences in V/Q ratio based on where you are in the lung?
apex: V/Q > 1 - more air than blood
The majority of oxygenated blood leaving the lung comes from the ____? what does this cause?
base
- have lower PO2 in arterial blood than in alveolar air
take away from ficks principle of diffusion
diffusion directly proportional to area, inversely proportional to thickness
what gas is diffusion limited, and what does that mean?
- soluble gases like CO
- quickly binds Hb, causes little change in partial pressure
- will never saturate blood, just depends how quickly it can get out of alveolus
what gas is perfusion limited, and what does that mean?
- insoluble gases such as NO (and to some extent O2 and CO2)
- equilibrate rapidly
- gas transfer is limited by the amount of blood
how do you measure the diffusion capacity of the lung?
- single breath CO test*
- patients breaths dilute CO gas from residual volume to TLC
- holds breath for 10 seconds, exhale
- 1st part of exhaled gas is discarded b/c its dead space
- measure how much CO is diluted down in alveoli
what is the alveolar gas equation?
PAO2= (Patm-Ph20)xFiO2 - (PACO2/R)
where at 37*C, Patm= 760, Ph2O= 47 , FiO2= 0.21, R=0.8
what does the alveolar partial pressure of CO2 depend on?
1) directly proportional to metabolism (production)
2) inversely proportional to ventilation (elimination)
describe the Bohr effect
a decreased p50 or increased affinity for O2 to Hb is caused by: decreased: Temp PCO2 2,3 DPG H+
O2 capacity
1 gm Hb binds 1.34 mL O2
normal blood= 15 g Hb/100mL
or
20.1 mL O2/100 mL blood
T/F An anemic patient has a lower venous SaO2
true- need to extract more O2 because you have less circulating Hb
4 causes for hypoxemia (PaO2
- hypoventilation- increase in pCO2, Aa difference is normal, PO2 would go up with O2,
- diffusion limitation
- shunt
- V-Q inequality
only form of hypoxemia that doesn’t respond to 100% O2
SHUNT (PaO2= 55mmHg)
how is CO2 transported in blood?
10% dissolved
20-30% carbamino
60-70% HCO3-
what regions generate breathing pattern?
DRG (inhalation) &
VRG (expiration) of medulla
what regions control breathing pattern?
apneustic (excites DRG)
pneumotaxic (inhibits DRG)
what do medullary chemoreceptors do
decreased pH and increased CO2
where are peripheral cehmoreceptors and what do they do?
carotid body and aortic arch respond to low O2
three components of mucociliary clearance system?
mucus, periciliary fluid, cilia (beat upwards to mouth)
* no cilia in alveoli (removed via macrophages)
