Spirometry in Practice

• A technique used to measure air flow in and out of the lungs.

• A recording of lung volumes and capacities defined by the respiratory process. These recordings may be static (untimed) or dynamic (timed).

• Assesses the integrated mechanical functions of lungs, chest wall and respiratory muscles.

•The gold standard for diagnosis, assessment and monitoring of COPD.

• Better than PEFR (which is effort dependent) for demonstrating airway obstruction in BA.

• The most commonly used PFT.

Indications

• Measure airflow obstruction to help make a definitive diagnosis of COPD

• Detect airflow obstruction in smokers who may have few or no symptoms

• Assess one aspect of response to therapy

• Perform pre-operative assessment

• Distinguish between obstruction and restriction as causes of breathlessness

• Perform pre-employment screening in certain professions

1) Volume Displacement

Spirometer

• Conventional old spirometers

• Derived indices are generally manually calcualated.

• High resistance to airflow

•Time consuming, inconvenient.

• Difficult disinfection

2) Flow Sensitive

Spirometer

• Utilize a sensor that measures air flow as the primary signal and calculate volume by integration.

• Automatically calculate a wide range of ventilatory indices and draw curves, which provide an immediate feedback on quality.

•Easier for the patient and operator.

•Easy disinfection, some have disposable flow sensors eliminating the need for disinfection.

3) Portable Spirometer,

Peak Flowmeter

• Readings have limited accuracy and are flow dependent.

• Limited role in intitial ssessment of respiratory disease.

•Reasonably reliable for patients to monitor their own disease progression or response to therapy.

4) Incentive Spirometer

Rather than a diagnostic tool, it is used to improve the patient incentives to comply with treatment and to do respiratory exercises.

How to DO?

Before the Test

1) Exclude contraindications: • Haemoptysis of unknown origin.• Current chest infection or within in last 6 weeks.• Pneumothorax.• Recent MI or PE (< 3 m).• Unstable angina in last 24 hours.• Recent surgery (eye, chest, abdomen) (< 3m).• Recent CVA (< 3m).• Aneurysm (cerebral, thoracic, abdominal).

How to DO?

Before the Test

2) Stop Asthma Medications: • SABA 6h• LABA 12h• Ipratropium 6h• Tiotropium 24hMedications may be continued if the test aims to assess the patient condition on treatment.

How to DO?

Before the Test

3) Other Precautions: • Physical and mental rest.• No coffee or smoking for 30 mins.• Empty the bladder in females or those with history of urinary incontinence.

How to DO?

• Patient is sitting comfortably, not leaning forwards, legs not crossed, feet firm on floor.

• No tight clothes or collars.

• Explain the procedure to the patient.

• Nasal clip is optional.

During the Test

How to DO?

• Ask the patient to do a

Forced Expiratory Maneuver (FEM):

- Take a maximal inspiration.

- Hold the breath and seal your lips tightly around the mouth piece.

- Blow as fast as possible (blast expiration) until the lungs feel completely empty (at least 6 sec., up to 12 sec in obstructive disease)

- Examine the graph and record:

o FEV1.

o FVC.

o FEV1/FVC (FER)

During the Test

How to DO?

• Get 3 readings that meet acceptability criteria –two of them with repeatability criteria.

• Record the highest reading.

• Continue watching, explanation and encouragement throughout the procedure.

• If inspiratory flow is to be tested as well, inspiration is likewise tested.

During the Test

Acceptability Criteria• The patient followed instructions

• A continuous maximal expiratory manoeuvre throughout the test (i.e. no stops and

starts) was achieved and was initiated from full inspiration.

• There was no evidence of hesitation during the test

• The PEF has a sharp rise (flow-volume)• No premature termination, i.e. expiration

continued until there was no change in volume and the patient had blown for ≥ 6

seconds• There were no leaks

• No cough (FEV1 may be valid if cough occurs after the first second)

• No glottic closure.• No obstruction of the mouthpiece (e.g. by the

tongue or teeth)• No evidence that the patient took an

additional breath during the expiratory manoeuvre

Repeatability Criteria• Obtain 3 acceptable tests

• The two largest values for FVC should agree to within 5% or 150 mL.

• The two largest values for FEV1 should agree to

within 5% or 150mL.

• Submaximal efforto Submaximal effort

o Air leak around the mouthpiece (lips not tight enough)o Air leak through nose

o Incomplete inspiration before the forced expiratory maneuver (not at TLC)

o Incomplete or weak expiration (lack of blast effort)o Slow start of expiration

o Cough (particularly within the first second of expiration)o Glottic closure

o Obstruction of the mouthpiece by the tongueo Vocalisation during the forced manoeuvre

o Poor posture (leaning forwards).o Extra- breath during the blow

Causes of Poor Record

Vol

um

e, li

ters

Time, seconds

Unacceptable Trace – Premature Termination or

Glottic Closure

Normal

Vol

um

e, li

ters

Time, seconds

Unacceptable Trace – Slow Start

Normal

Vol

um

e, li

ters

Time, seconds

Unacceptable Trace - Coughing

Normal

Vol

um

e, li

ters

Time, seconds

Unacceptable Trace – Extra Breath

Normal

Spirometry includes:

• Lung volumes (most simple).

• Lung capacities (composite of > 2 volumes)

• Volume per time: as FEV1,2,3,4,5,6

• Volume / time: flow rate (values + curve)

• Flow rate / Volume: (values + loop)

Adverse Effects

• Light headedness• Headache

• Fainting: reduced venous return or vasovagal attack (reflex)

• Transient urinary incontinence

TotalLung

Capacity

Tidal Volume

Inspiratory ReserveVolume

Expiratory ReserveVolume

Residual Volume

Inspiratory Capacity

Vital Capacity

End Normal Exp

End Normal Insp

End Maximal Insp

End Maximal Exp

Functional ResidualCapacity

Predicted Normal Values

Age

Height

Sex

Ethnic Origin

Affected by biodemographic variables:

No

rmal

Ob

stru

ctiv

e

Res

tric

tive

Flow Volume Loop

Expiratory flow rateL/sec

Volume (L)

FVC

Peak expiratory flow (PEF)

Inspiratory flow rate

L/sec

RVTLC

Peak Inspiratory flow (PIF)

As noted by the red line, a curve which is scalloped out and leaning away from the Y axis suggests obstruction.

A curve that is straighter (green line) and leaning to the Y axis supports the diagnosis of restriction.

(> 0.7)

(< 80%)

(< 0.7)

(< 80%)(< 80%) (< 80%)

(< 80%)

Bronchodilator Reversibility Testing

•FEV1 should be measured (minimum twice,

within 5% or 150mls) before a bronchodilator is given

Bronchodilator*

DoseFEV1 before and after

Salbutamol400 µg via large volume spacer

15 minutes

Terbutaline500 µg via Turbohaler 15 minutes

Ipratropium160 µg via spacer 45 minutes

Bronchodilator Reversibility Testing• An increase in FEV1 that is both greater than 200

ml and 12% above the pre-bronchodilator FEV1 (baseline value) is considered significant (Up to 8% increase may occur in normal persons).

• It is usually helpful to report the absolute change (in mL) as well as the % change from baseline to set the improvement in a clinical context .

• The absence of reversibility does not exclude asthma because an asthmatic person’s response can vary from time to time and at times airway calibre is clearly normal and incapable of dramatic improvement.

Bronchoprovocation

Useful for diagnosis of asthma in the setting of normal pulmonary function tests

Common agents:

- Methacholine, Histamine, others

Diagnostic if: ≥20% decrease in FEV1

Look ONLY at FEV1/FVC, FVC

FEV1/FVC > 0.7FVC > 80%P

FEV1/FVC< 0.7FVC > 80%P

FEV1/FVC > 0.7FVC < 80%P

FEV1/FVC < 0.7FVC < 80%P

NORMAL OBSTRUCTIVE RESTRICTIVE MIXED orOBSTRUCTIVE + AT

Provocation Test

BD ReversibilityTest

See LaterBD Reversibility

TestIf asthma suspected

Reversible Not Reversible Reversible Not Reversible

BA COPD OBSTRUCTIVE + AT RV, TLC

Mixed

High Low