lipari pulmonary function testing

normal expiration is ___active/passive?___ process, with flow of air depending on

1.

2.

-passive process

1. elastic recoil

2. airway resistance

what do pulmonary function tests measure?

- airflow obstructions

- lung size restrictions

- decreased gas transfer across alveolar-capillary membrane

what are "abnormal" values in pulmonary function tests based on

- matched to race, age, sex, and height [RASH]

- outside of range based on normal individuals (95% confidence)

therefore, this definition is arbitrary and can misclassify pts

what are the uses of PFTs

1. evaluation: lung disease, chronic cough, dyspnea, chest tightness

2. effects of toxin exposure (dust, chemicals,...)

3. risk stratification before surgery

4. monitoring effectiveness of tx

5. impairment/ disability assessment

t/f: pulmonary function test values are compared to subjects with diagnosed lung function disorders and matched based on race/ethnicity

false. compared to HEALTHY subjects and matched based on race/ethnicity

which reference values does the American Thoracic Society (ATS) recommend

1. GLI for 3-95 years

- gold standard!! multiethnic

2. NHANES III 8-80yrs and Wang equation <8 years

which reference values would you use for a 90 year old patient getting pulmonary function testing done

Global Lung Function Initiative (GLI) for 3-95 yrs; multiethnic and most reliable (gold standard!)

tidal volume

total amount of air exhaled during normal quiet breathing (not forced)

expiratory reserve volume

max air exhaled BELOW tidal volume (below the normal amount you would exhale normally/ forced)

inspiratory reserve volume (IRV)

The additional volume of air that can be inhaled with maximum effort after normal inspiration

residual volume

Amount of air remaining in the lungs after a maximum forced exhalation (the amount of air left to prevent lungs from collapsing)

summarize and explain TV, IRV, ERV, and RV (summary)

tidal: how much air you exhale when normally breathing

erv: extra air you can forcefully exhale after a normal exhale

irv: extra air you can forcefully inhale after normal inhale

rv: air that always stays in your lungs after you fully exhale—this prevents lung collapse

functional residual capacity (FRC)

volume of air remaining in the lungs after a normal tidal volume expiration (ERV + RV)

functional residual capacity (FRC) is ___% of total lung capacity (TLC)

40%

inspiratory capacity (IC)

max volume of air inhaled after a normal exhale

(TV + IRV)

compare FRC to IC

- both add up to make up your total lung capacity (TLC)

FRC is what stays in your lungs after you exhale normally

IC is how much you can inhale from that same point

TV + IRV =

IC

vital capacity (VC)

amount of air exhaled after a maximal inspiration (75% of TLC)

VC = IRV + TV + ERV

vital capacity is ___% of total lung capacity

75%

2 ways to measure vital capacity

1. forced vital capacity (FVC)

- measured on forced expiration

2. slow vital capacity

- measured over 30+ second exhale

- normal range restrictive disorder unlikely

total lung capacity (TLC)

volume of air after maximal inspiration

TLC = IRV + TV + ERV + RV

t/f: RV is only measured indirectly

true. it is the amount that is left in the lungs so we cant really take it out and measure it

t/f: restrictive lung diseases will show an increase in TLC

false. reduction in TLC bc cant get air into lungs due to restriction when inhaling

vital capacity + _________ = TLC

functional residual capacity + _________ = TLC

IRV + ERV + reserve volume + __________ = TLC

vital capacity + reserve volume = TLC

functional residual capacity + inspiratory capacity = TLC

IRV + ERV + reserve volume + tidal volume = TLC

forced vital capacity (FVC)

measurement of the amount of air that can be forcefully exhaled from the lungs after the deepest inhalation

what is FEV1 and what does it convey and depend on

FEV1: amount of air exhaled during the 1st second of FVC maneuver

- conveys info on obstruction

- depends on volume of air in lungs and effort when exhaling

- can be lowered by a decrease in TLC or lack of effort

FEV1 can be lowered by

obstructions, decrease in TLC, lack of effort

why do we use FEV1/FVC instead of just FEV1?

- more sensitive

- independent of patient's size or TLC

- measures airway obstruction with or without restriction

whats a normal fev1/fvc? obstruction?

normal: >75%

obstruction: <70-75%

diagnosis if <70%

what is peak expiratory flow

fastest airflow rate reached during exhalation (FVC)

describe the proper way to take a peak flow measurement

1. have patient STAND and INHALE deeply

2. blow into peak flow meter as fast as possible

3. write down number shown on meter

- repeat twice (best of 3 total)

describe what DLCO is (diffusing lung capacity for carbon monoxide) & how you know if its abnormal

pt takes single breath of CO and enters lungs-> binds to HgB

- if there is NO CO in their exhalation= no abnormality

- if there IS CO in their exhalation= abnormal (bc of decreased gas transfer, the CO didnt diffuse onto hgb properly and was instead exhaled)

t/f: an abnormal diffusing lung capacity for carbon monoxide would show no CO in a patient's exhale

false. abnormal test WOULD show CO since bad gas transfer led to it still being in lungs

common conditions that reduce diffusing lung capacity for carbon monoxide (DLCO)

anything where gas transfer from alveoli to blood is impaired

- lung resection

- emphysema

- interstitial lung disease

normal spirometry and lung volumes with reduced DLCO can suggest

- pulmonary vascular disease

- anemia

- early interstitial lung disease

when are arterial blood gases assessed

- hypoxemia

- hypercapnia (CO2 retention)

- acid-base disorders

what is an A-a gradient

Difference in partial pressure of oxygen between alveoli and arterial blood; used to measure pulmonary gas exchange quality

what can a normal A-a gradient and hypoxemia indicate

alveolar hypoventilation (ex: sedative overdose)

(low inspired oxygen rather than issues with gas exchange)

what is FeNO? why is it used?

Fractional exhaled nitric oxide (FENO)

- measures eosinophilic airway inflammation

-used to assess patients' adherence to therapy or if they need more ICS therapy

a low feno (<____ppm) indicates ____________ response to ICS

a high feno (>____ppm) indicates ____________ response to ICS

low <25ppm: decreased response to ICS

high >50ppm: increased response to ICS (bc high eosinophilic inflammation)

spirometry measures all lung volumes and capacities (including Fev1) EXCEPT

RV (residual volume; never directly measured)

FRC (left in lungs after normal exhale-> erv + rv)

TLC (all lung volume sum; need rv)

t/f: spirometry is the most widely available PFT and is used to define the degree of restrictive lung diseases

false. obstructive lung disease

spirometry IS the most widely available pft, but it cannot directly measure rv, frc, and tlc—which are essential for diagnosing restrictive lung disease

instead, it may show characteristics in restrictive diseases

since spirometry cannot measure TLC, which tests can?

- helium dilution

- nitrogen washout

- body plethysmography

- chest xray measurement (planimetry)

which 2 curves are produced in spirometry

volume vs time

flow rate vs volume

which PFT is the most widely available, useful, and can be done in 15-20 mins

spirometry

t/f: obstructive lung diseases are characterized by a lower capacity to move air through airways and into the lungs

false. out of lungs (restrictive is into lungs)

mechanisms of obstructions in obstructive lung diseases

- mucosal factors (secretions, edema,inflammation)

- smooth muscle constriction

- loss of elastic support

- collapse of airways

identify whether the following are increased, decreased, or normal in obstructive lung disease

FVC

FEV1

FEV1/FVC

fvc= normal (exhaled total is normal)

fev1= low (low in first second)

fev1/fvc= low (normal is 70+)

which spirometry measurements define an obstructive process

low FEV1 and low FEV1/FVC

which 3 diseases are commonly associated with obstruction

asthma, emphysema, chronic bronchitis

obstructive vs restrictive lung disease characteristics

obstructive: defined by low fev1 and low fev1/fvc!!

- low FEV and FEV1/FEV ratio [fvc is normal]

- cannot get air out of lungs

restrictive: defined by low TLC!!

- FEV1/FEV ratio is normal or higher

- low FVC and low FEV1

- cannot get air into lungs

identify whether the following are increased, decreased, or normal in restrictive lung disease

FVC

FEV1

FEV1/FVC

FVC= low

FEV1= low

FEV1/FVC= normal or higher(70+)

t/f: restrictive lung diseases are characterized by an inability to move air into the lungs and have a reduction in all expiratory volumes

true

what are restrictive processes defined by

lower tlc (total lung capacity)

- normal flow-loop curve

- shortened height and width

describe the changes to a flow-loop curve in restrictive diseases

- shape remains normal (pattern of inspiration and expiration is unchanged)

- shortened height and width:

mild<80%

moderate <65%

severe <50%

common diseases associated with restriction

parenchymal inflammation, fibrosis, alveolar filling, chest wall deformity, neuromuscular conditions, poor effort

normal fev1/fvc

over 70-75%

t/f: normal spirometry values are age dependant

true. lower values in older patients, higher in younger pts

would you expect to see high or lower fev1/fvc in elderly? kids? kids w asthma?

older= lower

kids= higher

kids with asthma= <85%

t/f: healthy athletic subjects may have a low fev1/fvc, and normal fev1 and normal FVC

true. may indicate health or mild asthma

- must use judgement or give bronchodilator challenge

a FEV 1 of ____ indicates moderate obstruction

a FEV1 of ______ indicates severe obstruction

<60: moderate

<40%: severe

t/f: a fev6 may be used instead of fev1

true

what is an acute bronchodilator response characterized by? (fev1)

increase in FEV1 >12% and >0.2L

(mostly seen in asthma)

compare asthma, chronic bronchitis, and emphysema in terms of FEV1, FEV1/FVC, airway resistance, and response to bronchodilators

-low FEV1 in all

- low FEV1/FVC in all

- increased airway resistance in asthma and chronic bronchitis (not emphysema)

- large response to bronchodilators mainly in asthma!!! low in chronic bronchitis and emphysema (about 20% may have tho)

what can be a potential differential in asthma, chronic bronchitis, and emphysema

-increased airway resistance in asthma and chronic bronchitis (not emphysema)

- large response to bronchodilators mainly only asthma

t/f: mainly asthma pts have hyper-reactive airways, but some patients with COPD may as well, suggesting worse prognosis and accelerated decline in FEV1

true

asthma may be diagnosed by demonstrating hyperresponsiveness to provocative agents such as

methacholine

histamine

distilled water

cold air

exercise

a positive hyperreactivity asthma test would display

decline FEV >20% AND reversibility of obstruction to bronchodilators

[can be used on pts with no wheezing and normal PFTs]

summary of obstructive lung disease vs restrictive lung disease

FVC

FEV1

FEV1/FVC

TLC

RV/TLC

airway resistance

FVC: normal in OLD, low in RLD

FEV1: low in both

FEV1/FVC: low in OLD, normal or high in RLD

TLC: normal or high in OLD, low in RLD

RV/TLC: normal or high in both

airway resistance: high in OLD, normal in RLD

which pulmonary functions values are the same in obstructive and restrictive lung diseases

FEV1 (low)

RV/TLC (normal or high)

FEV1 and FEV1/FVC can be used to diagnose ______ and suggest _______

diagnose obstructions, suggest restrictions

use TLC to diagnose restriction using 4 methods:

helium dilution, nitrogen washout, body plethysmography, chest xray measurement (planimetry)

what are 2 minor tests used to assess lung function based on general fitness

1. 6 minute walk test: walk pre determined route, see how much distance is covered

2. harvard step test: step up and down 20 inch step, last 5 minutes, 1 minute rest, measure recovery heart rate (lower hr= better fitness)