SPIROMETRY BASICS

ROSEMARY STINSON MSN, CRNP THE CHILDREN’S HOSPITAL OF PHILADELPHIA DIVISION OF ALLERGY AND IMMUNOLOGY PORTABLE COMPUTERIZED WITH BUILT IN INCENTIVES WHAT IS SPIROMETRY?

 Use to obtain objective measures of 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  Invaluable screening tool for respiratory health compared to BP screening CV health  Gold standard for diagnosing and measuring airway obstruction.

ATS, 2005 SPIROMETRY AND

 At initial assessment  After treatment initiated and symptoms and PEF have stabilized  During periods of progressive or prolonged asthma control  At least every 1-2 years: more frequently depending on response to therapy WHY NECESSARY?

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

o To assess pre-operative risk

o To assess prognosis

o 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.  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.

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 therapists  The curves and numbers are hard to interpret TEST PROCEDURE

Three Phases: o Maximal inspiration- Deep breath in o - Blast of air: Takes at least 6 seconds to fully empty air o Continue completion to end of time

Vital Capacity: o Maximum amount of air emptied from lungs o Average 3-5 liters o Dependent on age, sex, height COMMONLY MEASURED VARIABLES

 Forced (FVC)  Forced Expiratory Volume in first second

(FEV1)

 FEV1/FVC  Forced Expiratory Flow from 25-75% of FVC (FEF25-75%)  (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  Depends upon age, height, sex  Measure of speed exhalation (volume/liters)  Value most used to diagnose obstructive disease and degree of improvement with  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 inspiration  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 restrictive o Calculated result o Measured FEV1 / Measured FVC o Percentage o 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  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  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 RECOMMENDED SPIROMETRY MEASUREMENTS:

• FEV1 • FEV 6 Before AND after use of • Forced expiratory volume in 6 seconds short-acting • FVC bronchodilator • FEV1/FVC

 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 > 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 • LABA, Theophylline> 12 hours • No smoking> 1 hour prior to testing

ATS, 2005 SUMMARY

 Pulmonary functions are important o Gold standard used to confirm diagnosis of asthma (≥ 12% FEV1, ≥ 200 ml) o Determine the degree of obstruction o Determine severity o 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 demonstrated  If reversible, suggests asthma  If not reversible, does not exclude asthma PRE-POST SPIROMETRY REPORT