pulmonary physiology Flashcards
___ is the gold standard for gas exchange
ABG (O2 tension in blood)
Q is proportional to
P/R
R is proportional to
length x viscosity / radius ^4
Q =
VA (velocity x area)
so velocity is Q/A
mVe =
Vt x RR
minute ventilation = tidal volume x respiratory rate (depth x frequency)
VT=
VD + VA
dead space + alveoli
compliance =
volume/pressure
Fick’s law of diffusion is proportional to
diffusion constant x (A x P)/T
PaCO2 is proportional to
VCO2/VA
CO2 in blood is dependent on/proportional to CO2 produced/alveolar ventilation
Henderson-Hasselbach
pH = pK + log(HCO3-/C02)
simplified: pH ~ HCO3- (pH directly related to bicard - base)
pH ~ 1/PaCO2 (pH inversely related to CO2 in blood)
CO2 + H2O H2CO3 H+ + HCO3-
respiratory system can be divided
- conduction portion
- condition the inspired air: warm to body temp, filter (remove particles), saturate with H20 vapor
- bulk transport of air
- respiratory portions
- gas exchange function (in alveolar sacs)
ventilation
- process by which air moves into lungs (inspiration) and out of lungs (expiration)
- how: muskulotskeletal pump
- why: need tiniest pressure gradient for exchange
- pressure fluctuations
- accomplished by coordination of respiratory muscles, rib cage, and lungs
dead space and alveolar volume
- efficacy of breath tells you nothing about depth of breath
- VT = VD + VA (tidal volume = dead space volume + alveolar volume)
- still some dead space in respiratory zone
- respiratory bronchioles only have a few alveoli
hypoventilation
retaining CO2: if you only ventilate dead space and alveoli
hyperventilation
blowing off CO2: raises pH (alkaline)
why you use brain paper bag in panic attack
hypoxemia
low O2 in blopd
hypoxia
low O2 in tissues
ischemia
lack of blood flow
dead space and alveolar volume
- VD - dead speace volume
- physiologic: non-perfused alveolus, changeable
- anatomic: areas without alveoli, not changeable
mVe =
- mVe = VT x RR = (VD + VA) x RR
- mVe is volume of air inhaled in one minute, and ventilation is dead space and alveolar ventilation
- dead space increases in COPD
distribution of blood flow
- majority of breath to the bottom of the lung
lung compliance
- change in volume/change in pressue
- 1/elasticity
- ability of tissue to expand
- decreased compliance = stiffer
surface tension and compliance
- surface tension wants to collapse alveoli
- surfactant lessens surface tension – produced by T2 pneumocytes
surfactant
- breaks bonds on liquid molecules to lessen surface tension and increase compliance for easier breathing
- reduces surface tension to decrease muscular effort to ventilate lungs
- composed of lipids and proteins
- lipoprotein: secreted by alveolar epithelium (T2 cells) into alveoli
- both hydrophilic (on inside of air-liquid interface) and hydrophobic/lipophilic (outside)
- break H+ bonds of interface to increase compliance
- separate with breathing in – keep small alveoli from collapsing
- anti-bacterial, prevents infection: immune effect to protect against invaders (proteins A and D)
alveoli
- alveolar walls are T1 pneumocyte, surfactant is T2
- alignment of surfactant molecules
- resident macrophage
- air:liquid surface
static pressure-volume (PV) curve
- lungs get stiffer with greater volume
- compliance = volume/pressure
- higher change in volume for change in pressure is compliance
- lower change in volume for change in pressure is stiff
the top of the lung has ____ compliance than the bottom of the lung
lower
with decreased compliance, patients breathe ____ to compensate
faster (increase RR)
factors that impact air flow and resistance
- Q = P/R
- laminar (easy to move)
- turbulent: need greater pressure
- resistance
- radius, airway length, gas viscosity, lung volume
- larger airways generally have higher velocity and thus more turbulent flow
- Q = VA: as cross section area of branching airways increase -> slower velocity -> laminar flow (less resistance, so less pressure needed)
cross sectional area and bronchial tree
sympathetic stimulation stimulates ____ for ____, and parasympathetic stimulation stimulates ____ for ____
- sympathetic stimulation (NE) stimulates beta2 receptors for bronchodilation
- parasympathetic stimulation (ACh) stimulates muscarinic receptors for bronchodilation
non-uniform lung ventilation
- regional obstruction
- asthma, foreign body, mucus plug
- regional changes in elasticity
- pneumonia, pulmonary fibrosis, atelectasis
- regional dynamic compression - hole/bullous in lung
- COPD, pneumothorax
- regional limitation to expansion
- scoliosis, burn injury, rib fracture/muscle guarding
work of breathing
- work of respiratory muscles to over come the elastic and resistance factors from airways, lungs, and chest wall to expand the chest and lungs
- elastic factors: compliance (stiffness) of lungs, chest wall, and abdominal contents
- airway resistance: bronchospasm, airway inflammation, and swelling and secretions
- work to get air in
conducting zone
trachea to terminal bronchioles
upper respiratory tract
- nose, pharynx, and larynx
- provides 1st line of defense against infection
- filters, warms, humidifies air
lower respiratory tract
- trachea begins at C6
- directly superior to beginning of trachea is larynx (vocal chords)
- trachea bifurcates (carina) into 2 mainstem bronchi (right and left) at sternal angle (2nd rib space)
- T4/T5 when supine, T7 when standing
- trachea is 16-20 cartilaginous rings (hyaline cartilage)
- flexible but rigid to keep trachea open
- each ring is open posteriorly (for flexibility) covered by trachealis muscle
tracheal/bronchial epithelium
psudostratified columnar epithelium
- ciliated: into sol layer (more liquid), push gel layer up into airway to catch gunk - airway defense
- spit out or to stomach
- mucus secreting goblet cells and glands
- lymphoid tissue
- airway secretions (mucus) line RT and form 2 layers - sol and gel layers
- bronchial wall epithelium lined by cilia in sol layer
- sol layer is less viscous than gel layer, allowing cilia to beat freely
- during forward stroke, cilia tips hit gel layer to propel it centrally to larger airways and mouth
___ bronchioles have ____ and continue as ____ bronchioles, which then open into ____ and individual ___
terminal bronchoiles have no alveoli and continue as respiratory bronchioles (have alveoli), which then open into alveolar ducts and individual alveoli
gas exchanging zone
- acinus describes functional gas exchange unit, consiting of
- respiratory bronchioles
- alveolar ducts, alveolar sacs, alveoli
- acinus is distal to terminal bronchiole
alveoli
- walls composed of squamous epithelium (T1 and T2)
- T1 are very thin
- 95% of alveolar surface area
- function for gas exchange
- T2 synthesize and secrete
- reduce surface tension and allow alveoli to remain open
- also may be resident alveolar macrophages (dust cells)
respiratory cycle
- inspiration
- external pressure > intrathoracic pressure
- expiration
musculoskeletal pump
- external intercostal muscles: aid in quiet and forced inhalation
- elevation of ribs, expand thoracic cavity
- internal intercostal muscles: aid in forced expiration (quiest is passive)
- depress ribs, decrease dimensions
- both external and internal innervated by intercostal nerves
Boyle’s law
P related to 1/v
- PV = k (pressure x volume = constant)
zone of apposition
angle formed by rib cage and diaphragm
more acute is normal
45-90 is “flattened diaphragm”
rib cage moves in ___ movement, and sternum moves in ___
bucket handle
pump handle
abdominal paradox
- sign of diaphragmatic dysfunction
- paradoxical inward motion of abdomen as rib cage expands in inspiration
- seen in high SCI (C5 or above)
sniff test
- assesses motion of diaphragm during a short, sharp inspiratory effort through nostils
- descent of diagphragm will be seen in people without disorder
- with unilateral/bilateral diaphragm paralysis, there is a paradoxical (cephalad) movement of paralyzed diaphragm
flail chest
- multiple fractures in a single rib – multiple floating segments
pulmonary function testing (PFT
- MIP, MEP, MVV
maximal inspiratory pressure (MIP)
- lowest pressure developed during a forceful inspiration against an occluded airway
- primarily measures inspiratory muscle strength
- recorded as negative number in cm H20 or mmHg
- AKA negative inspiratory force (NIF)
maximal expiratory pressure (MEP)
maximal voluntary ventilation (MVV)
- total volume of air exhaled during 12 seconds of rapid, deep breathing
- primarily measures breathing reserve (respiratory muscle endurance)
- liters/minute
- rapid, deep breathing for 12-15 seconds: measured volume is indication of respiratory muscle endurance
respiratory muscle fatigue
- supply: energy availability
- muscle blood flow, O2 content
- demand: energy requirements
- work of breathing, strength, mechanical efficiency
- psychologic and neurologic factors
factors that influence breathing
- hypothalamus – emotions, pain
- cortex – voluntary control
- chemoreceptors
chemoreceptors and breathing
- central: in medulla oblongata
- responds to increase CO2 that passed through BBB
- H+ stimulates receptors for increased breathing depth and increased rate
- peripheral: in aortic/carotid bodies
- responds when PaO2 < 60 mmHg –> increase ventilation
- synergistic with higher PaCO2
- also responds to pH decreases –> increase ventilation
- hypoxic drive
- responds when PaO2 < 60 mmHg –> increase ventilation
changes in peripheral chemoreceptors
normal CO2 is 40
normal O2 is 90
hypoxic drive with chronic elevated PCO2 levels
seen in emphysema
FIO2
- fraction inspired air O2
- 0.21 = 21% (dry) room air
- inhaled air: 0.21 x 760 mmHg = 160 mmHg of O2
- PAO2 = alveolar O2
- PaO2 = O2 dissolved in arteries
henry’s law
- explains how gases dissolve across alveoli-capillary membrane
- amount of gas absorbed by a liquid is directly proportional to the partial pressure and solubility of the gas in the liquid
- air-liquid interface = alveolar-capillary membrane
- CO2 is 20xs more soluable than O2
- CO2 diffuses across alveolar-capillary membrane faster than O2
fick’s law of diffusion
- passive exchange of gas between lung and blood/blood and tissues and organs is dependent on
- concentration gradient (changes in partial pressures) of gases
- supplemental O2 changes pressure gradient of alveolus and venous blood
- solubility of the gases (CO2 > O2) - diffusion constant
- surface area (A) available for diffusion
- membrane thickness
- concentration gradient (changes in partial pressures) of gases
gas diffusion and lung
- alveoli provide high SA for gas exchange with pulmonary blood
- average 480 million
at rest, there is ____ time for full equilibration of oxygen
- sufficient
- resting conditions: pulmonary capillary blood is in contact with alveolus for about 0.75 seconds total and fully equilibriuated with alveolar oxygen after about 0.25 seconds
lung disease ____ diffusion
- impairs
- in exercise: pulmonary blood flow is quicker (less time for gas exchange)
- those with lung disease are unable to oxygenate pulmonary blood fully and thuss have a limited ability to exchange gases
- limits performance and ADLs
CO2 diffuses across alveolar-capillary membrane ____ times fast than oxygen
- 20
- so factors are less likely to compromise CO2 transfer from blood to alveoli
O2 content of blood (delivered to tissues) is dependent on
- PaO2 (dissolved O2 in blood)
- hemoglobin concentration (Hgb)
also blood flow (CV function)
O2 transportation
- 2 forms
- dissolved in plasma (2%)
- reversibly bound to hemoglobin (98%)
Bohr effect
- increased CO2 (decreased pH) –> decreased Hb affinity for O2
- promotes “unloading” (think muscle)
oxyhemoglobin dissociation curve
CO2 transport (VCO2)
- 3 ways CO2 is transported
- bicarbonate (HCO3-) in RBC and plasma (60%)
- carbaminohemoglobin (30%)
- dissolved gas (10%)
haldane effect
- deoxyhemoglobin (after “unloading”) can carry more CO2
pulmonary circulation pressures
- P system artery > P pulmonary artery
pulmonary circulation
- Q = P/R
- rate of blood flow through pulmonary circulation = flow rate through systemic
- but RV driving pressure is very low (10-15 mmHg)
pulmonary vascular resistance (afterload) is
- low
- low capillary hydrostatic pressures produce less net filtration than produced in system capillaries
- lungs are “dry”
pulmonary circulation autoregulation
- hypoxic vasoconstriction – pulmonary arterioles constric when alveolar PO2 decreases (decrease PAO2)
- matches ventilation/perfusion ratio
recruitment and distention in responses to increased ____
- cardiac output
- PVR (afterload) remains low even with increase CO
distribution of pulmonary blood flow and ventilation
- blood flow and ventilation is greater at the base than at the apex
are ventilation and perfusion evenly matched across the lung
- no, under normal circumstances, they are not evenly matched
- Ventilation = V
- Perfusion = Q
low V/Q
shunt
V < Q
high V/Q
dead space
Q < V
V = Q
perfusion is ____
- regional – heterogenous
- gravity effect
- cardiac output
- pulmonary vascular resistance (PVR)
- zone I: alveoli > arterial > venous
- airflow > blood flow (dead space)
- zone II: arterial <> alveoli > venous
- airflow <> blood flow (mixed)
- zone III: arterial > venous > alveoli
- blood fow > airflow (shunt)
ventilation and perfusion
blood gas changes with exercise
- SpO2 and PaO2 constant
- pH and PaCO2 down
- mVe = RR x Vt
ventilation/perfusion relationships
