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Spr2015_Week5 > Pulm Fxn test > Flashcards

Pulm Fxn test Flashcards

1
Q

When would you use a PFT?

A

1) Whether pulmonary disease is present 2) Type or pattern of disease present 3) Severity of disease 4) Change in disease severity over time or with therapy 5) Pre-operative clearance

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2
Q

`variables measured by PFTs?

A

1) Lung volumes
2) Airflow
3) Gas exchange
4) Compliance of the lung
5) espiratory muscle strength •
6) Airway responsivene

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3
Q

what are obstructive diseases

A

trouble getting air out

• Asthma • COPD (emphysema, chronic bronchitis) • Bronchiolitis

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4
Q

what are restrictive diseases

A

decr compliance/ability to inflate lungs
poor inspiratory muscles

• Pulmonary edema • Interstitial lung disease • Neuromuscular weakness • Pleural disease • Obesity

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5
Q

whatt are mixed diseases

A

mixed obstructive + restrictive

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6
Q

mechanism of spirometer

A

1)

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7
Q

spirogram looks like?

A

a

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8
Q

Difference between volumes and capacities

A

volumes = measured or at least estimated

single entity
everything but residual volume

capacities = sums of at least 2 volumes

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9
Q

define tidal volume (TV or VT)

A

1) volume of normal, even respiratoions at rest
2) inspiration requires effort, expiration passive

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10
Q

define ERV (expiratory reserve volume)

A

volume of gas left in lung after normal, tidal expiration that can be exhaled

requires effort

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11
Q

describe inspiratory reserve volume

A

volume of gas inhaled above that inhaled with normal tidal inspiration

requires effort

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12
Q

describe residual volume

if abnormal, means…

estimate or measured?

A

volume of gas remaining in lung at end of max expiration

if abnormal, can’t completely collapse lung

estimated (can’t measure)

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13
Q

define functional residual capacity

due to?

what is special about FRC?

A

volume of gas left in lung at end of tidal expiration

= sum of ERV + RV

volume at which elastic recoil of lung balanced by chest wall wanting to spring out

(system in equilibrium)

NO EFFORT REQUIRED

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14
Q

define inspiratory capacity

A

volume of gas maximally inspired from FRC

= VT + IRV

requires effort

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15
Q

vital capacity

A

volume of gas maximally inspired from RV

= ERV + VT + IRV

  • requires effort
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16
Q

define total lung capacity

estimated from?

effort or passive?

A

total volume of gas in lung

= RV + ERV + TV + IRV

  • requires effort

–> estimated from RV

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17
Q

define flow equation

A

flow = volume/time

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18
Q

what is an acceptable measure of expiratory airflow

A

6 sec expiratory time

curve plateaus for ~ 1 sec

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19
Q

when you are measuring airflow, you are measuring ____

A

expiratory airflow

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20
Q

Reproducibility of airflow means you need to have

A

3 FEV1 maneuvers within 200 mL

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21
Q

Define FEV1

A

within 1st second after expiring

70-80% should come out within first second

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22
Q

Define FVC

A

FVC = forced vital capacity

should be same as vital capacity

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23
Q

Define FEV1/FVC ratio

what is normal range

A

ratio between the amount of air expire d in 1st second to entire expired amount

0.7-0.8 dependent on age

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24
Q

if you have airflow obstruction, how does that affect FEV1/FVC

A

then FEV1/FVC ratio decr

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25
what is HALLMARK OF OBSTRUCTIVE LUNG DISEASE
reduced FEV1/FVC
26
what do values of FEV1/FVC ratio dependent on?
1) age, gender, race, height normal range = 80-120%
27
if the FEV1 is greater or FEV1/FVC incr than what you would expect, suggestive of?
suggestive of restrictive process cannot diagnose restrictive disease on spirometry MUST HAVE LUNG VOLUMES TO DIAGNOSE
28
you cannot diagnose ___ on spirometry
restrictive diseases
29
what is the flow-volume loop?
airflow vs. amount of air expired expiratory limb = positive deflection inspiratory limb = negative deflection
30
define effort-independent portin of flow-volume loop
1) when expire, rapidly reach resp flow rate 2) effort indepedent = leftover 2/3 of expiration because only maximal flow rate through airway no matter how hard you try
31
what is special about effort independent
no matter how hard you try you can't incr this linear decline in flow determined by elastic recoil of lung and airways resistance
32
shape of inspiratory limb?
symmetric
33
when you see obstructive lung disease on flow-volume loop what is characteristic? when you see restrictive lung diseases on flow-volume loop what is characteristic?
reach peak expiratory flow rate, but obstructive so can't get air out (high airway resistance) --\> flow rate decr rapidly --\> "coving" = cannot make a diagnosis just supportive for restrictive diseases, normal shape to flow-volume curve, but at same volume, expiratory flow is higher (supranoral airflow)
34
if you have obstrictive outside the thorax (extrathoracic) what happens during expiration vs. inspiration
during expiration, you generate positive pressure in chest to blow air out trachea surrounded by atmospheric pressure and positive pressure in lumen, so push walls of trachea apart during expiration not see much obstruction to airflow \_\_\_ during inspiration, you have negative pressure in chest so in lumen of trachea you have negative pressure, and outside of trachea = so trachea walls move in during inspiration --\> see truncation of flow-volume loop (flattening during inspiration)
35
if you have obstruction in central airway inside thorax (intrathoracic obstruction)
during expiration, airway surrounded by positive pressure in lung itself to move air out so airway has positive pressure outside compared to inside, so walls of trachea will move inward --\> truncation of flow volume cloop during inspiration, airway surrounded by negative pressure to pull airway walls out in the thorax so obstruction is not visualized on flow-volume loop
36
variable intrathoracic obstruction vs. variable extrathoracic obstructive vs. fixed obstruction
intrathoracic --\> arrow points down (central airway tumors) extrathoracic --\> arrow points up (laryngospasm, laryngeal edema) fixed --\> doesn't change with inspiration vs. expiration
37
airflow interpretation what to look at? how do you interpret?
- FEV1 - FVC - FEV1 /FVC - Flow-volume loop --\> decide if normal, obstructed, suggested restriction, airway obstruction
38
Lung Volumes with Helium Dilution Method
1) inhale known concentration of inert gas (not absorbed into blood stream in alveoli = N2 and He) 2) allow diffuse 3) blow out and have C2 to calculate what volume of distribution that initial gas went into = gives you total lung capacity
39
LIMITATIONS OF HELIUM DILUTION METHOD
in obstructive disease, if you have trouble getting air out, so you retain more gas --\> lots of deadspace --\> s inspird gas can't distribute evenly (UNDERESTIMATE VOLUME)
40
what is plethysmography
measures lung volumes based on P1 V1 = P2 V2 breathing around the functional residual capacity --\> intermittently shutter will close =-\> change in volume
41
benefits of plethysmography vs
cons = difficult, harder to do pros= Most accurate as does not require diffusion of gas - important in patients with air trapping such as asthma and emphysema!
42
when interpreting lung volumes procedure
1) look at TLC low = diagnostic of restrictive lung disease 2) look at FRC= thoracic gas volume 3) increased FRC (TGV) = hyperinflated - TLC or FRC \> 120% RV \> 140% (RV calculated) if just RV elev then air trapping = obstructive 4) decr FRC = restricted) - TLC or FRC \< 80%
43
if you are hyperinflated what is your TLC or FRC
* TLC or FRC \> 120% predicted * RV \>140% (RV is a calculated value) * Air trapping if just RV elevated
44
45
what is DLCO what is it determined by (4)
marker of gas-exchange 1) surface area of alveolar capillary interface 2) membrane thickness 3) diffusion gradient of gas 4) presence of Hb
46
where is gas exchange occurring?
alveolar-capillary interface
47
how do you measure DLCO what does it mean?
1) inhale known concentration of CO CO = 200x greater affinity for Hb so readily taken into blood stream from alveoli 2) hold for 10 sec 3) exhale so amount leaving is inversely proportional to how well alveoli working more CO out (little taken up, so poor alveoli function) 3) also do helium diluton method to measure volume of distribution at same time
48
if you have decr DLCO what does that mean?
emphysema = destroy alveolus and capillary membrane so decr surface area --\> dead space ## Footnote interstitial lung disease or fibrosis --\> incr membrane thickness (so CO uptake decr) pneumonia or pulm edema --\> alveoli filled with pus --\> decr surface area, incr diffusion distance pulm vascular disease --\> in pulm HTN, incr resistance to flow so decr diffusion capacity and decr pulm blood flow --\> decr DLCO
49
if you have incr DLCO what does that mean?
1) alveolar hemorrhage = extrude RBC into alveoli --\> Hb in lung --\> CO bind all Hb --\> incr DLCO 2) polycythemia 3) interstitial edema (water get into alveoli and interstitium full of water so more RBC) 4) asthma
50
hallmark of pulm vascular disease
normal airflow, normal lung volume decr DLCO
51
why do you use helium dilutation with DLCO?
calculate alvoelar volume --\> corrected for chest wall/pleural diseases (obesity) or resection of lung lung resected due to lung cancer, amount of CO taking up will be decr because less surface area but not due to problem with alveoli NOT CORRECT FOR RESTRICTIVE LUNG DISEASE WITH IDIOPATHIC PULM FIBROSIS BECAUSE IT AFFECTS DIFFUSING DISTANCE (ALVEOLAR MEMBRANE)
52
HOW DO you measure compliance (dV/dP)
how well your lungs expand/how elastic or floppy are your lungs 1) probe into esophagus 2) inhale to TLC 3) exhale out, measure pressure 4) repeat measure total volume you've exhaled out and plot against pressure change
53
pressure-volume change in disease
as you get more volume, it takes more pressure to get much smaller change in volume
54
how does pulm fibrosis appear on pulm volume curve
pulm fibrosis = make lung like concrete --\> pressure-volume curve is flatter so takes much more pressure for a given volume change
55
how does emphysema look on pressure-volume curve?
emphysema --\> decr elastic recoil so lungs have been overstretched much more compliant and get much larger volume change for given change in pressure (shift left and up)
56
obesity pressure-volume curve
obesity = more soft tissue around chest cavity, chest cavity = lower volume for given pressure shifts curve down but no change in shape
57
asthma pressure-volume curves
asthma acute exacerbation = problem getting air out = retain more air in chest, more volume in lung at give pressure, shifted up
58
when do you see compliance measured? ARDS with mechanical ventilator
giving known tidal volume we can pressure at end of expiration to see compliance of lung
59
what is respiratory muscle strength
how much force generated on inspiration or expiration ## Footnote PiMax: • inspiration attempt against closed valve * PeMax: * expiration against closed valve very effort dependetn so can fake it
60
Respiratory muscle weakness causes
1) neuropathies 2) myopathies
61
how to measure airway responsiveness with bronchodilator challenge criteria
1) give albuterol (b2 agonist = vasodilator) \>12% change in FEV1 and/or FVC and 200CC incr volume
62
how to measure airway responsiveness with methacoholine challenge
PC20 \< 8 mg/mL cholinergic medication --\> bronchoconstriction 20% decr in FEV1
63
how to measure airway responsiveness with EIB
1) inhale cold air while exercising 2) want to see decline in FEV1 by 20% to be positive
64
procedure of looking at all PFTs
1) look for airflow obstruction - present/absent - bronchodilator response 2) lung volumes (incr, decr, mixed = airflow obstruction + decr lung volume) 3) gas exchange (DLCO and DLCO/VA incr/decr/normal) 4) flow volume loop (upper airway obstruction)
65
FEV1 = 2.29L 72% predictive FVC = 6.04 FEV1 incr to 2.63L 83% predictive
FEV1 = 2.29L 72% predictive FVC = 6.04 Ratio of FEV1/FVC = low gets bronchodilator FEV1 incr to 2.63L 83% predictive (\>200 cc change in FEV1 so he has reversibility)
66
FEV1 = 44% FVC = 44% ratio preserved at 88% TLC = 92% predictive FRC reduced and RV reduced (less than 80%) Adjusted DLCO/VA = 112%
symmetrically reduced suggests restrictive lung disease but can't diagnose with spirometry TLC = 92% predictive = restrictive lung disease FRC reduced and RV reduced (less than 80%) DLO 46% predictive Adjusted DLCO/VA = 112% so restriction not due to parenchymal lung disease but some chest wall restrictive lung disease with normal DLCO/VA obesity, pleural disease, or neuromuscular disease
67
FEV1 = 52% FVC = 60% Ratio = 66% (low = obstruction) TLC = 77% (low) RV and FRC = normal DLCO = 41%
Ratio = 66% (low = obstruction) TLC = 77% (low) RV and FRC = normal = obstructive because give larger lung volume and restrictive causes lower lung volume so balance out DLCO = 41% correct up to 83% with DLCO/VA DLCO/VA adjusted and TLC should be within 500cc --\> underestimated due to restrictive lung disease --\> restriction + obstruction you can only say diffusing capacity reduced not chest wall obstruction --\> mixed disease with normal DLCO/VA = obesity + COPD
68

Spr2015_Week5 (19 decks)

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