1 Resp Physio Flashcards
Where dead space and respiratory zone begin/end
Dead space: nose/mouth to terminal bronchioles. Resp: resp bronchioles to alveoli
What makes up transpulmonary pressure
Alveolar pressure (pressure inside lungs) - intrapleural pressure (pressure outside of lungs)
During tidal breathing transpulm pressure is always ___. When intrapleural pressure becomes positive
Positive. Ptx or forced expiration, otherwise always negative
2 muscles that contract on inspiration
Diaphragm and ext intercostals
Muscles that contribute to active exhalation
TIRE: transverse abd, int oblique, rectus abd, ext oblique
Vital capacity req for an effective cough
15 ml/kg
Primary determinant of CO2 elimination
Alveolar ventilation
Dead space in avg pt, what increased Vd leads to
2 ml/kg, about 150 ml. Wides paco2-etco2 gradient and causes co2 retention
Minute ventilation: how to calculate, rough amount
TV X RR. 5LPM
Alveolar ventilation: what it measures, how to calculate, rough amt
Fraction of min vent that is available for gas exchange. (TV - dead space) x RR. 3.5LPM
Alveolar vent: ___ prop to CO2 produc and ___ prop to PaCO2
Directly to production, inversely to PaCO2
Anything that inc Vd/Vt ratio inc ___ __ and __ __. Most common cause under GA is what
Dead space, dec alveolar vent. Reduction in co
Causes of inc Vd:
Face mask, moisture exchanger, PPV, anticholinergics, old age, neck extension, dec CO or pulm bf, COPD, PE, sitting pos
Causes of dec Vd
ETT, LMA, Trach, neck flexion, supine or prone pos
Physiologic dead space can be calc w/___ eqn, eqn itself:
Bohr. (PaCo2- exhaled CO2) / paco2
In sitting position what things are higher in base than the apex
Partial pressure of alveolar CO2 and blood flow
In sitting position what is higher in apex than base
PA02 and V/Q ratio
The best ventilated alveoli are the most _____, which are at the ___ of the lung
Compliant, base
Perfusion is greatest at the base due to ____, ventilation is best at the ___ due to alveolar ___
Gravity, base, compliance
Non dependent lung: vent, perf, v/q, 02, co2, n2
Low, low, high, high, low, same
Dependent lung: vent, perf, v/q, 02, co2, n2
High, high, low, low, high, same
Vent perf mismatch: what happens in zone 1, blood passing underventilated alveoli does what, mismatch ____ the a-a gradient, and it minimizes ____
Bronchioles constrict to minimize it, retains CO2, increases, shunt
Atelectasis causes ___ to ___ shunt
Right to left
An alveolus can transfer more ___ than ____
More co2 than 02
With v/q mismatch the paco2 gradient becomes ___, the pa02 gradient becomes ___
Smaller, larger
When pneumocytes begin making surfactant, peak
22-26 weeks, peak 36 weeks
Each alveolus has ___ ___ of surfactant, larger vs smaller concentration
Same amount, larger has smaller concentration
Zone 1 is inc by what 3 things
Low bp, PE, or high a/w pressure
Sites of normal anatomic shunt: 3 , what this means
Thebesian veins (drain l heart), bronchiolar veins, pleural veins. Bypasses lungs and never gets 02
What zone 4 is
Pulmonary edema. Pa>Pist>Pv>PA. Fluid overload, mitral stenosis, laryngospasm, neg p pulm edema
Alveolar oxygen equation
Fio2 x (PB 760-Ph20 47) - PaCO2/RQ
What comprises the respiratory quotient, >1 means what, 0.7 means what
CO2 production / oxygen consumption. >1= lipogenesis. 0.7= lipolysis
Causes of hypoxemia with normal A-a gradient (2), can they be fixed with supplemental 02
Reduced fio2 and hypoventilation. Yes
Causes of hypoxemia w inc A-a gradient, can they be fixed with 02
Diffusion limitation (yes), v/q mismatch (yes), shunt (no)
Nml values: IRV, TV, ERV
3000, 500, 1100 (mls)
Nml value: RV, TLC, VC
1200, 5800, 4500 (mls)
Normals: IC, FRC
3500, 2300 mls
Tv ___ ml/kg, VC ___ ml/kg, FRC ___ ml/kg dosed on ___
7, 70, 35. IBW
4 things that cant be measured with spirometry
CV, CC, TLC, FRC
How peep restores FRC
Reducing zone 3 (when FRC is reduced, zone 3 increases)
Things that decrease FRC
GA, obese, preg, neonates, adv age, supine, lithotomy, tberg, paralysis, light during anes, excessive IVF, high fio2, reduced pulm compliance in disease states (pulm edema, pulm fibrosis, acute lung injury, Etc)
Things that increase FRC
Adv age, prone, sitting, lateral, obstructive lung disease, peep, sigh breaths
Closing capacity= ___ + ____
Residual volume + closing volume
Factors that inc closing volume
Close p: COPD, LV failure, obesity, supine, ext of age, preg
By age 30 CC=FRC when, age 44 they’re equal when, 66 equal when
30= GA, 44= supine, 60= standing
CaO2 calc
(1.34 x hgb x sao2) + (pao2 x 0.003)
How to calc DO2, nml value
CaO2 x CO X 10. 1000 ml02/min
VO2 eqn, nml values
CO X (CaO2 - cvo2). 3.5 ml/kg/min, roughly 250 ml/min
Dec p50= ___ shift, inc p50= ___ shift
Dec= left. Inc= right
Left shift occurs in ____, right shift occurs where.
Left= lungs, right= metabolically active tissue
What is the Bohr effect
CO2 and h+ cause hgb to release 02
____ inc 2,3 dpg. 2,3 dpg is a compensation mechanism in ___
Hypoxia. Anemia
Hamburger shift
Cl transferred to RBC in exchange for HCO3 as buffer
Venous CO2 and ph
5 higher than PaCO2, 7.36
Methods of co2 transport, which most common
Bicarb (70%), bound to hgb (23%), dissolved in plasma (7%)
CO2 solubility= ___ law
Henrys
Haldane effect
CO2 carriage: 02 causes rbc to release co2
Bohr effect
02 carriage: co2 and dec ph cause rbc to release 02
C02 dissoc curve: when right v left means, how po2 relates
Left love right release. Lower po2= more co2 carried
4 consequences of hypercarbia
Hypoxemia, inc myo 02 demand, hyperkalemia, dec 02 carrying capacity
Paco2=
CO2 production / alveolar ventilation
Causes of inc co2 production
Sepsis, overfeeding, MH, shivering, seizures, thyroid storm, burn
Causes of dec co2 elim
A/w obstruct, inc dead space, ARDS, COPD, resp center depression, drug OD, inadequate NMB reversal
Effects of hypercarbia
Hypoxemia, inc p50/right shift, myo depression, sns stim, oculocardiac, in k and ca and ICP, dep loc
When co2 narcosis occurs
> 90 paco2
Acute resp acidosis: paco2 and ph change
Inc 10mmhg, dec 0.08
Chronic resp acidosis paco2 and ph change
Inc 10, dec 0.03
When paco2 and min vent change in linear fashion
Paco2 20-80q
When paco2 is a resp depressant
> 80-100
Mac of co2
200
Causes of L shift co2 response curve
PaO2 <60, metab acid, IC htn, fear, salicylates/aminophylline/doxapram/NE
Causes of r shift co2 response curve
Metab alk, carotid endarterectomy, sleep, VA/Opioids/NMB
What L v R shift CO2 response curve means
L: ve higher than expected for given co2. Resp alk. RL ve lower than given, resp acid
L v R shift co2 response curve on apneic threshold
L = threshold dec, R: threshold inc
Where pneumotaxic and apneustic centers are
Pons
Where drg and vrg are
Medulla
Dorsal resp center: where, func
Medulla/tractus solitarus. Insp pacer
Ventral resp Central location and func
Medulla-tractus solitarus. Insp and exp- mainly exp when ve demand inc
Pneumotaxic center: location and func
Upper pons, inhib DRC/triggers end insp. Strong stim= rapid shallow rr, weak= slow and deep
Apneustic center: location and func , what is it inhibited by
Lower pons, stim DRC/causes insp. Inhib by pulm stretch receptors
Which chemoreceptors respond to 02 vs co2
02= peripheral, CO2= central
Most imp stim for central chemoreceptor, what it drives
H+ in the csf, DRC
Window that hyperventilation effects bicarb
Few hours to 2 days
Central chemo receptor is depressed by what
Profound hypercarbia and hypoxemia
Peripheral chemoreceptors: location, what they dont respond To, 2ndary roles
Bifurcation of carotid artery. Dont:sa02 ca02. 2nd: pac02, h+, perfusion pressure monitoring
What is hypoxic ventilatory response
02 <60 closes k channels in type 1 glomus cells, opens ca ch and inc NT release, AP along herrings nerve and CN 9, term in medulla = min vent inc
What impairs hypoxic vent response
Carotid endarterectomy and 0.1 MAC of IA/TIVA
2 conditions that dont impair hypoxic vent response
Anemia and CO poisoning
Hearing Breuer inflation reflex
If inflation 1.5> FRC, reflex turns off the DRC and stops further inflation. Mediation by CN X and phrenic n
Hearing Breuer deflation reflex
When lung vol too small helps prevent atelectasis by taking bigger breath
J receptors: stim what, Activ by what
Stim tachypnea. Activ by PE/CHF
Paradoxical reflex of head
Stim newborn to take first breath
HPV: stim by what, impaired by what
Reduction in ALVEOLAR (not arterial) 02 tension. MAC VA >1.5, vasodilators, pde inhib, dobutamine, CCB, phenylephrine, epi, dopamine
What may increased HPV shunt
Hypervolemia/LAP >25 and elev CO
