Respiratory Function Testing

alveolar ventilation

Va

diffusing capacity of lung for carbon monoxide

DLCO

forced expiratory volume in 1 second

FEV1

forced vital capacity

FVC

functional reserve capacity

FRC

peak expiratory flow rate

PERF

pulmonary function tests

PFTs

total lung capacity

TLC

ventilation/perfusion scan

V/Q scan

inspiration

diaphragm muscle contracts and pulls downward while muscles pull upward; overcome elastic properties of lung and resistance to airflow

expiration

passive process in which the diaphragm relaxes; elastic recoil of lungs pulls lungs back to original size and shape

-evaluate physiologic processes

-diagnosis of symptomatic diseases

-screen for early, asymptomatic disease

-determine prognosis of disease

-monitor response to treatment

purpose of PFTs

obstruction to airflow, changes in lung size, decrease in gas transfer

types of abnormalities detected in PFTs

demographics (age, height, race, sex)

what normal PFT results are based off of

peak flow, spirometry, pulse ox, DLCO

common types of PFTs

arterial blood gas, exercise oximetry, six-minute walk test, maximum inspiratory/expiratory pressure

specialty types of PFTs

TV (tidal volume)

air exhaled during normal breathing

IRV (inspiratory reserve volume)

maximal air inhaled above tidal volume

ERV (expiratory reserve volume)

maximal air exhaled above tidal volume

RV (residual volume)

air remaining in the lung after maximal exhalation

TLC (total lung capacity)

sum of TV + IRV + ERV + RV

VC (vital capacity)

sum of TV + IRV + ERV

FRC (functional reserve capacity)

sum of RV + ERV

FEV1 (forced expiratory volume in 1 second)

volume of air exhaled during the first second of the FVC maneuver

FVC (forced vital capacity)

total amount of air that can be exhaled

FEV1/FVC

FEV1 as a ratio of FVC - more sensitive to measure obstruction as independent of patient's size or TLC

FEF (forced expiratory flow)

flow (speed) of air during a forced expiration

FEF 25%-75%

FEF during 25% to 75% of FVC - represents the mean flow during the middle half of the FVC

PEF (peak expiratory flow)

maximum flow obtained during forced expiration

obstructive lung disease

reduced capacity to get air out of the lungs

COPD, asthma, bronchiectasis, cystic fibrosis

types of obstructive lung diseases

FEV1/FVC < 0.7 (70%)

diagnosis of obstructive lung disease

restrictive lung disease

reduced capacity to get air into the lungs

interstitial lung disease (fibrosis, sarcoidosis), chest wall pathology (scoliosis), obesity, neuromuscular (ALS)

types of restrictive lung diseases

reduction in all expiratory volumes; FEV1/FVC is normal

diagnosis of restrictive lung diseases

pulmonary vascular disease

broad term including any condition that affects the blood vessels within the lungs

pulmonary hypertension, chronic thromboembolic disease

pulmonary vascular disease

spirometry

PFT in which a clip is placed on the nose and patient exhales hard and fast into a mouthpiece until no more air will come out

most lung volumes and capacities except residual volume (RV)

what spirometry measures

TLC, FRC

what CANNOT be calculated with spirometry?

reduced

FEV1 in obstructive lung disease

normal or reduced

FVC in obstructive lung disease

reduced

FEV1/FVC ratio in obstructive lung disease

normal or reduced

FEV1 in restrictive lung disease

reduced

FVC in restrictive lung disease

normal or reduced

FEV1/FVC ratio in restrictive lung disease

obstructive

obstructive or restrictive lung disease?

restrictive

obstructive or restrictive lung disease?

coving

hallmark of obstruction in a flow-volume loop

normal, just smaller

shape of flow-volume loop in restrictive lung disease

post-bronchodilator FEV1/FVC < 0.7

diagnosis of COPD with spirometry

>12% change in FEV1 pre vs post bronchodilator

diagnosis of asthma with spirometry

peak flow meter

PFT in which a patient blows into a meter as hard and fast as they can and determines how far the marker was moved

PEF (peak expiratory flow)

what peak flow meters measure

personal best

to find a patient's __________________ with peak flow meter, take their peak flow between noon and 2 PM each day, each time after they take their quick-relief medicine to relieve symptoms, or any other time their provider tells them to

DLCO (diffusing capacity of lung for carbon monoxide)

PFT that tests diffusing capacity of lungs for carbon monoxide, measuring ability of lungs to transfer gas from air to red blood cells across alveolar-capillary membrane

lung restriction, emphysema, interstitial lung disease

disease states where reduced diffusing capacity (DLCO) is seen

pulse oximetry

measures oxygen saturation via arterial saturation with a device that emits and reads the reflected light from capillary blood to estimate saturation

>95%

normal SpO2

V/Q scan (Ventilation Perfusion Scan)

method that uses radioactive gas and albumin to measure ventilation and perfusion with a series of two scans performed together: ventilation in which radioactive material is inhaled to measure where air flows in the lungs and perfusion in which radioactive material is injected into vein to measure where blood is flowing in lungs

PE and pulmonary hypertension

what are V/Q perfusion scans often used for?