SPIROMETRY BASICS

ROSEMARY STINSON MSN, CRNPTHE CHILDREN’S HOSPITAL OF PHILADELPHIATHE CHILDREN’S HOSPITAL OF PHILADELPHIA

DIVISION OF ALLERGY AND IMMUNOLOGY

PORTABLE COMPUTERIZED SPIROMETRYWITH BUILT IN INCENTIVES

WHAT IS SPIROMETRY?

Use to obtain objective measures of lung function Physiological test that measures how an individual

inhales or exhales volume of air Primary signal measured–volume or flow Essentially measures airflow into and out of the Essentially measures airflow into and out of the

lungs Invaluable screening tool for respiratory health

compared to BP screening CV health Gold standard for diagnosing and measuring airway

obstruction.

ATS, 2005

SPIROMETRY AND ASTHMA

At initial assessment After treatment initiated and symptoms and

PEF have stabilized During periods of progressive or prolonged

asthma controlasthma control At least every 1-2 years: more frequently

depending on response to therapy

o To evaluate symptoms, signs or abnormal laboratory tests

o To measure the effect of disease on pulmonary function

o To screen individuals at risk of having pulmonary disease

WHY NECESSARY?

diseaseo To assess pre-operative risko To assess prognosiso To assess health status before beginning strenuous

physical activity programs

ATS, 2005

SPIROMETRY VERSUS PEAK FLOW

Recommended over peak flow meter measurements in clinician’s office.

Variability in predicted PEF reference values. Many different brands PEF meters. Peak Flow is NOT a diagnostic tool. Peak Flow is NOT a diagnostic tool.

Helpful for monitoring control.

EPR 3, 2007

WHY MEASURE?

o Some patients are “poor perceivers.”o Perception of obstruction variable and spirometry

reveals obstruction more severe. o Family members “underestimate” severity of

symptoms.symptoms.o Objective assessment of degree of airflow obstruction.o Pulmonary function measures don’t always correlate

with symptoms.o Comprehensive assessment of asthma.

ATS, 2005 ; EPR 3, 2007

EPR 3,1997

SPIROMETRY MYTHS

Can’t be performed on children It takes a long time It can only be performed by respiratory

therapistsThe curves and numbers are hard to interpret The curves and numbers are hard to interpret

TEST PROCEDURE

Three Phases:o Maximal inspiration- Deep breath in o Exhalation- Blast of air: Takes at least 6 seconds to

fully empty air o Continue completion to end of timeo Continue completion to end of time

Vital Capacity:o Maximum amount of air emptied from lungso Average 3-5 literso Dependent on age, sex, height

COMMONLY MEASURED VARIABLES

Forced Vital Capacity (FVC) Forced Expiratory Volume in first second

(FEV1) FEV1/FVC

Forced Expiratory Flow from 25-75% of FVC Forced Expiratory Flow from 25-75% of FVC (FEF25-75%)

Peak Expiratory Flow (PEF) Flow volume loop/expiratory curve

FEV1

Defined: Forced expired volume in 1st second of FVC maneuver; Normal > 80%

Expressed as a percent of the predicted value A proportion of the forced vital capacity (FVC) or

FEV1 /FVC. Approximately 2.5 - 4 Liters Approximately 2.5 - 4 Liters

Depends upon age, height, sex Measure of speed exhalation (volume/liters) Value most used to diagnose obstructive disease and

degree of improvement with bronchodilator The test most used for assessing the risk of future of

exacerbations

ATS, 2005; EPR 3 ,2007

FEV1

FVC

Defined: Forced vital capacity-Maximal volume of air exhaled with maximum force

Measures the amount of air blown out after full inspirationinspiration

Total lung capacity minus Residual Volume Their “umph” factor

FVC

FEV1/FVC RATIO

Defined: Amount of air expired in the 1st second/ Total amount air expired during maneuver

o Decreased in obstructive, normal in restrictiveCalculated resulto Calculated result

o Measured FEV1 / Measured FVCo Percentageo Example: FEV1 3 L and FVC 4 L ; FEV1/FVC= 75%o Compared to predicted normal value ( age, sex,

height)

PEFR

Defined: Peak expiratory flow rate- The maximum flow attained during a FVC maneuver.

Effort dependent!The top of the blast The top of the blast

Value indicative of large airway function Used to determine baseline in peak flow meters

Measure PEFR (in meters/second) x 60 = baseline Must have baseline minimum of ~ 240 Liters

FEF 25-75%

Defined: Measures the average amount of air in the small airways during the middle half of test (From 1-3 seconds)

Forced expiratory flow rate between 75% and 25% of FVC

Forced expiratory flow rate between 75% and 25% of FVC

Flow in the middle of the curve Measures small airways function Effort dependent

Useful in children over 10 yrs old Most sensitive test to detect the presence of early

small airways disease!

FEF 25-75%

THE EXPERT PANEL RECOMMENDEDSPIROMETRY MEASUREMENTS:

• FEV1

• FEV6

• Forced expiratory volume in 6 seconds

• FVC

• FEV1/FVC

Before AND after use of short-acting bronchodilator

Should be performed for patients where a diagnosis of asthma is being considered

Including children ≥ 5 years of age.

EPR 3- Guidelines, 2007

TESTING METHOD

o Patient has 3 acceptable tests o Pre bronchodilator

o Drug administered (Albuterol 4 puffs 90 mcg/puff)o Testing repeated:

> 10 to 15 minutes post SABA > 10 to 15 minutes post SABA > 30 minutes post anticholinergic agents

o Significant reversibility an increase in FEV1 > 200 ml and 12 % from baseline

o Degree of airway reversibility- correlates with airway inflammation

ATS 2005 ; EPR 3 ,2007

TESTING…

o Aim of test –to determine whether patient lung function can improve with therapy- in addition to their regular medications.

o Baseline testing: when not taking any drugs • SABA> 4 hours• SABA> 4 hours• LABA, Theophylline> 12 hours• No smoking> 1 hour prior to testing

ATS, 2005

SUMMARY

Pulmonary functions are importanto Gold standard used to confirm diagnosis of

asthma (≥ 12% FEV1, ≥ 200 ml)o Determine the degree of obstruction

Determine severityo Determine severityo To assess one aspect of response to therapy

o To monitor for future remodeling

SUPPLEMENTAL SLIDES

BRONCHODILATOR RESPONSE

FEV1 may improve within about 10 minutes of using inhaled bronchodilator

If reverses by ≥ 12% “reversibility” or “bronchial hyper-responsiveness” has been

demonstrateddemonstrated If reversible, suggests asthma If not reversible, does not exclude asthma

PRE- POST SPIROMETRY

REPORT