Pulm Deck 1 Flashcards
4 functions of the respiratory system
1) O2 in, CO2 out
2) barrier function
3) metabolic function (angiotensin)
4) host-defense/immune function
what makes up the upper airway? lower?
- nose, pharynx, glottis, vocal cords
- trachea, bronchial tree, alveoli
what is the function of the upper airway?
- to condition air (warm it to body temp) and humidify it
- also provides ~50% of total resistance
at what level of the lung can a piece be removed? what is this called?
- a bronchopulmonary segment= region supplied by 1 segmental bronchi
- is the anatomic unit of the lung
whats the difference between a pneumothroax and a pleural effusion?
pneumothorax- air between visceral (close) and parietal pleura
pleural effusion- fluid
what is the physiological unit?
- respiratory unit=
respiratory bronchioles, alveolar ducts, and the alveoli - 5 mm tall, but make up a lot of surface area (2.5-3 L) or SA of 50-100m^2
what are conducting airways? what does this form? what is it’s volume?
- bronchi that contain cartilage + non-respiratory (w/o alveoli) bronchioles
- makes anatomic dead space
- 150 mL
- goes up to 16th branch point
what are type 1 and type 2 epithelial cells?
- type 1= very long, 98% surface area, site for gas exchange
- type 2= produce surfactant
- exist in a 1:1 ratio in adults
- neonates don’t have type 2
laplace relationship for lungs
inward pressure= 2*surface tension/ radius
what does surfactant do? is there more in smaller or larger alveoli?
- decreases surface tension; more in smaller alveoli
what allows for the stability of alveoli
- surfactant
2. interdependence- alveoli mechanically linked together
what allows for the interdependence of alveoli?
- collateral ventilation provided by:
pores of kohn- adjacent alveoli
channels of lambert- terminal airways- alveoli
channels of martin- interbronchial
where do bronchial veins come from and where do they go?
- from bronchiole arteries leading to terminal bronchioles
- 1/3 blood goes back to heart, 2/3 drains into pulmonary circulation (admixture)
3 ways inhaled materials are deposited
impaction (large in pharynx)
sedementation (medium in small airways)
diffusion (small in alveoli)
what is the mucociliary clearance system?
- removes inhaled particles, consists of:
- mucus layer
- pericillary fluid
- cilia- beat in coordinated fashion, propel stuff up
pathway of lungs
trachea 2 main stem bronchi lobular bronchi (6 total) segmental bronchi (bronchopulmonary segment) bronchioles - non-respiratory bronchioles - respiratory alveolar ducts
3 ways particles are cleared
- they’re swallowed
- mucociliary system
- alveolar macrophages eat them
2 circulation pathways of lung
- bronchial- lungs can survive without
- pulmonary- largest vascular bed in body
where do you lose cilia?
where do you lose smooth muscle?
where do you lose cartilage & mucus glands?
- alveolar ducts
- alveolar sacs
- bronchioles
what is Boyle’s law?
at a fixed temperature, the volume of gas is inversely proportional to the pressure exerted by the gas
muscles of active expiration
- internal intercostals- flattens ribs and sternum further
- abdominal muscles- causes diaphragm to be pushed further upwards
muscles of inspiration
- external intercostals- ribs go up and out (lateral & anteroposterior)
- diaphragm- 75% increase in thorax volume- muscle flattens and goes down (vertical)
accessory muscles of inspiration
- SCN
- scalenus
- contraction used for forceful inspiration; lift sternum and ribs 1 & 2
what is the diaphragm stimulated by?
phrenic nerve (C3-C5)
volumes- tidal, IRV, ERV, Residual
Vt- 500 mL (quiet breathing)
IRV- 3,000 mL (volume inhaled past tidal)
ERV- 1,200 mL (volume exhaled past tidal)
RV- 1,200 mL (what’s left)
inspiratory capacity
IC= IRV+ Vt= 3.5 L
functional residual capacity
FRC= ERV+ RV= 2.4 L
Vital capacity
VC= IRV+ Vt+ ERV= 4.6 L
Total lung capacity
TLC= IRV + Vt+ ERV+ RV= 5.8 L
which volumes and capacities cannot be measured with a spirometer?
RV, FRC, TLC
two ways to measure RV
1) helium dilution- requires ventilated tissue
2) body plethysmography
what determines the volume of air in the lungs? what is the equation for specific compliance?
- compliance = change in volume/ change in pressure = 0.2 L/cm H2O
- specific compliance= lung compliance/lung volume
what is hysteresis?
the dissipation of energy between inflating & deflating the lungs
what is the compliance like in emphysema?
- lose elastin
- high compliance
- lung easier to inflate
- low pressure at high volumes
what is the compliance like in fibrosis?
decrease compliance b/c of fibrotic tissue; higher pressure at lower volumes
what determines the total compliance of the lungs?
lung (elastic pulling it together): chest-wall (muscles pulling out) interactions
atmosphere
intra-alveolar
intra-pleural pressures
760 mmHg
760 mmHg
756 mmHg
how do you calculate trans-lung pressure (Pl)?
Pl= Pa-Ppl
= 760-756= 4 mmHg
- pressure of lung wall on pleural cavity
how do you calculate transmural pressure (Pw)?
Pw= Ppl-Pb
= 756-760 = -4 mmHg
- Pb= pressure on chest wall from air outside
- Pw= difference between pleural cavity and thoracic wall
how do you calculate pressure across the respiratory system?
Prs= Pl + Pw= 0
T/F Intrapleural pressure is always below atmospheric pressure
T
At points with no air flow, volume is ____ and pleural pressure is _______
max, 0
3 patterns of gas flow
laminar, transitional, turbulent
what two things is air flow determined by?
pattern of gas flow
resistance to air flow by airways
where does laminar flow begin? where is true laminar flow present?
smaller airways of the conducting zone; in small bronchioles
where is the highest resistance found? why?
- generation 4- medium sized bronchi that are short and branch frequently
- air flow is turbulent
- remember air flow at any 1 generation is really parallel
3 inspiratory airflow profiles
0-9: tubulent, high resistance
10-16: laminar flow, some resistance
17-23: diffusive, respiratory zone, no resistance, independent of respiratory cycle
2 things that decrease air way resistance, 4 things that increase it
- decreased by increased lung volume (inhalation), sympathetics
- increased by vagal stimulation, mucus, edema, contraction of smooth muscle
what is the main measure of airway resistance?
FEV1- the forced expiratory volume in 1 second
smaller= higher resistance to expiration
what is the most important pulmonary function test measurement?
FEV1/FVC- greater than 75% are normal, less than 75% are obstructive
what happens as lung volume increases?
- force of inspiratory muscles decreases
- lung recoil pressure increases
- airway resistance decreases
- PIFR (peak inspiratory flow rate) is between TLC and RV
where does PEFR occur and what happens to it as it approaches resting volume?
first 20% of cycle; get expiratory flow limitation
what is the effort independent region of flow-volume curve? what is dynamic compression determined by?
no matter how strongly you try and exhale, the flow rate always converges the closer to get to the reserve volume; determined by alveolar- pleural pressure
when is airflow effort dependent?
at higher lung volumes (early expiration)
what is flow limitation caused by?
the compression of airways when pressure outside is greater than the pressure inside airway
what is the equal pressure point?
where pressure in the airway is equal to pleural pressure in a region without cartilage
which breathing parameter is reduced with obstructive lung disease (asthma, COPD)? Whic is reduced in restricted lung disease (fibrosis)?
FEV1- obstructive
FVC- restrictive
which receptor does albuterol act on? which parameter does it increase?
beta-2 agonist; increases FEV1 and FVC
what are the two main components of respiratory work (O2 consumption)?
- elastic work (overcomes elastic recoil)
- resistance work (overcomes airflow resistance)
what is elastic work proportional to? flow-resistive work?
elastic work- tidal volume
flow-resistive work- frequency of breathing
what is the compensation for the increase in work cause by fibrosis? COPD?
fibrosis- breathe shallow & rapidly
COPD- breathe slower & deeper
what is the ideal gas law?
PV=nRT
what do Dalton & Amagat’s laws state?
Dalton- sum of partial pressures= total pressure
Amagat- sum of partial volumes= total volume
what are the partial pressures of O2, N2, and water vapor in humidified air before gas reaches the alveolus?
PO2= 760*0.21= 160 mmHg PN2= 760*0.79= 600 mmHg PH2O= 47 mmHg- dilutes other gases!
how do you calculate the partial pressure of tracheal O2?
(Patm-Ph2O) X Flow of O2= 150 mmHg
(760-47)*0.21
what is the alveolar gas equation?
Pao2= Pio2- (Paco2/R)
where Pio2= (Patm-Pwater)xFiO2
what is the ideal alveolar oxygen amount?
102 mmHg
what is the respiratory quotient?
R= excreted CO2/ O2 taken up
what is the fraction of alveolar CO2 determined by?
metabolism & rate of ventilation
- inversely proportional to ventilation
- a 50% reduction in ventilation will double Pco2
- directly proportional to production
equation for the partial pressure of CO2
PCO2= VCO2(production) X (Patm-Ph2o)/alveolar ventilation
where is inspired air shunted to? why?
lung base
- base of lung has more alveoli
- the base is more compliant, can hold more reserve
what is a time constant? what does a long time constant mean?
the rate at which the alveoli fills
t= resistance x compliance
- longer= slow filling & emptying
what happens to the time constant when you increase resistance?
- alveoli fills more slowly & becomes under-ventilated
what happens to the time constant when you decrease compliance?
- alveoli fills faster than the normal unit but only receives half the ventilation
what are the 4 features of the N2 curve obtained from the nitrogen washout test
1) %N2 starts at 0 for some volume as the dead spaces empty
2) rapid upswing in % N2 as alveolar regions empty
3) alveolar plateau where there is equal emptying of all lung zones
4) there is a second upswing due to slowly emptying alveoli
what can the nitrogen washout test measure?
anatomical dead space- volume in the middle of the first upward inflection
what is the equation for ventilation?
v= frequency x tidal volume
what is physiological dead space and how can it be calculated?
- total volume that does not participate in gas exchange
- anatomical dead space + alveoli that are ventilated but not perfused
- measure fraction of expired CO2 and compare it to PaCO2 in blood
The larger the tidal volume, the ____ the dead space ventilation; To increase alveolar ventilation, a _______ in tidal volume is more effective than a ______ in the frequency of breathing
smaller
What is Fick’s law?
- transfer of gas is proportional to the area that it has to go through, a constant, and the difference in partial pressure
- the transfer of gas is also indirectly proportional to thickness
What is Graham’s law?
- the rate of diffusion is direction proportional to the solubility coefficient of the gas
- inversely proportional to the sqrt of the molecular weight
if there is no difference between the partial pressure for a gas in alveoli and end capillary blood, what is flow limited by? what is an example?
- perfusion limited, NO
perfusion vs diffusion
perfusion- process of delivering blood
vs
diffusion- movement of a substance
properties of pulmonary arteries
- carry deoxy blood
- thin wall, minimal smooth muscle
- 7X more compliant
- easily distensible
- low pressure *** exposed to alveolar pressure
3 ways to challenge diffusion of O2
1) thicken walls (fibrosis)
2) exercise (decrease time of blood in caps)
3) drop alveolar PO2 in high altitude, gradient drops
pulmonary vascular resistance changes with changes in vascular pressure how? and by which mechanisms?
- decreases
1) recruits more capillaries
2) capillaries distend to accommodate more blood
what is pulmonary vascular resistance?
change in pressure between pulmonary artery (14) and left atrium (8) / blood flow ( 6 L/min)
- comes out to 1mmHg/L/min (LOW!!!!)
what is PVR regulated by?
- gravity
- lung volume changing alveolar pressure & extra-alveolar pressure
- A-V pressure gradient
alveolar resistance ___ as you approach total lung capacity, while extra-alveolar resistance ______
alveolar- increases (squishing vessels in alveoli)
extra-alveolar- decreases (expanding)
when is PVR the least?
at the functional residual capacity (stable resting point)
two reasons for blood flow to be higher in the base than the apex
1) more lung tissue at the base due to shape of lung
2) gravity pulls blood down easier
names of 3 zones of the lung
zone 1- no-flow zone
zone 2- waterfall zone
zone 3- normal zone
what is hypoxic vasoconstriction and what does it depend on?
- if blood is exposed to low PO2 in the alveoli, the vessels constrict
- depends on the ALVEOLAR concentration of O2, not the blood
- shifts blood from poorly ventilated areas to well ventilated areas; is important at birth
what is fluid movement across capillary governed by? how does edema develop?
- starling forces- hydrostatic & oncotic pressures
- when drainage rate exceeds maximum lymphatic flow
excessive filtration from pulmonary capillaries leads to ____, while excessive filtration from systemic capillaries leads to ____
- engorgement of alveolar walls & alveolar flooding
- engorgement of pleural space & pleural effusions (decreased lung volume)
what is the difference between obstructive and restrictive lung diseases?
obstructive- can’t exhale
restrictive- can’t fully expand
