R H Y S J E F F E R I E S

The role of lung function testing in the assessment of and treatment of:

AIRWAYS DISEASE

ARTP education

Learning Objectives

� Examine the clinical features of airways disease to distinguish between COPD and asthma

� Explore the pathogenesis of obstructive airways disease and relate these to patterns of lung function impairment

Overview of Airways Disease

Asthma: Pathology

Asthma: Pulmonary Function

� Bronchoconstriction causes increased airway resistance and work of breathing

� Demonstrated by reduced measures of expiratory flow:¡ PEF¡ FEV1¡ FEV1/FVC%¡ MEF values

Asthma: Pulmonary Function

� Airway narrowing may cause gas trapping leading to increased RV

� Bronchoconstriction may lead to increased FRC and hyperinflation¡ Airway resistance decreases with lung volume (as airway

calibre increases)¡ Tidal volume shifts to higher lung volume in order to minimise

work of breathing (dynamic hyperinflation)

Asthma: Pulmonary Function

� There is no gas exchange defect however uneven ventilation may reduce effective VA, and therefore reduce area for gas exchange¡ KCO likely to be normal or high¡ TLCO normal or slightly reduced (due to reduced VA), or

raised due to increased vasculature of respiratory bronchioles

� TLC likely to be significantly greater than VA (low VA/TLC ratio)

Asthma: Pulmonary Function

� Between exacerbations airway function may be normal¡ ‘Normal’PFT’s do not exclude asthma

� According to BTS guideline:¡ “Confirmation hinges on demonstration of airflow obstruction

varying over short periods of time”

� This can be assessed by:¡ Bronchodilator reversibility testing¡ Steroid treatment trial¡ Airway provocation testing

Reversibility Testing

Bronchodilator Reversibility Criteria

ARTP/BTS Guidelines160ml increase in FEV1, or

330ml increase in VC

ERS Recommendations>12% in FEV1 %predicted ,

and 200ml absolute

ATS Recommendations 12% and 200ml increase in baseline FEV1 or FVC

BTS COPD Guidelines ≥  200ml  and  ≥  15%  increase  in  FEV1   from  baseline

GOLD Guidelines≥  200ml  and  ≥  12%  increase  in  FEV1   from  baseline

40 yr old female

Non-smoker

Wheeze, allergy to cats

and dogs

47 yr old female

Non-smoker

BMI 47

Hx exertional breathlessness

Frequent RTI

46 yr old female

Smoker 25 pack yrs

Frequent RTI

Reports ‘asthma attacks’ requiring

hospitalization

52 year old male

Ex-smoker30 pack yr

Hx wheeze, SOB on exertion

COPD

� Definition:¡ COPD is characterised by airflow obstruction that is not fully reversible.

The airflow obstruction does not change markedly over several months and is usually progressive in the long term. (NICE 2010)

¡ COPD is a progressive airway disease which unlike asthma is only partially reversible

� COPD essentially comprised of two disorders:¡ Chronic bronchitis¡ Emphysema

� Both are present but clinical presentation varies according to which predominates

Emphysema

Centriacinar(mostly apex)

Panacinar(no regional preference)

Paraseptal(adjacent to pleura

or intra-lobular septa)

Emphysema

COPD: Chronic Bronchitis

� Chronic Bronchitis¡ Defined as persistent cough, for at least 3 months of the year,

for 2 consecutive years

� Hyperplasia and hypertrophy of mucous glands produce excess intra-luminal secretions

� Small airways are narrowed by:� mucous plugs, mucosal oedema, smooth muscle hypertrophy,

and bronchoconstriction

Chronic Bronchitis

COPD: Pulmonary Function

� PEF, FEV1 and FEV1% are reduced

� Dynamic compression during forced exhalation causes premature closure of airways

¡ This limits the volume of gas that can be exhaled and therefore reduces FVC

¡ During a slower exhalation (VC) transmural pressure is lower so collapse is less likely

¡ VC likely to be greater than FVC

COPD: Pulmonary Function

� Several features of COPD cause hyperinflation:

¡ Loss of elastic tissue caused by emphysema component increases lung compliance - Lungs become more easily stretched

¡ Mucous plugging and airway narrowing makes emptying of some compartments difficult - causing hyperinflation

¡ Dynamic hyperinflation occurs as increased airway resistance encourages ventilation at higher lung volumes (airway calibre is greater at higher volumes

� Helium dilution likely to be slow

� Large difference between TLCHe and TLCpleth

� TLC, FRC and RV will be raised

COPD: Pulmonary Function

� Gas transfer:¡ Emphysema causes reduction in alveolar surface area and so

TLCO and KCO may be impaired¡ Airway narrowing makes gas mixing slow and so effective VA

typically reduced

� The exact pattern of impairment for PFT’s will vary according to:¡ The predominance of components of COPD, i.e. Bronchitis vs

Emphysema, +/- asthma¡ The severity of disease

NICE(2004)

ATS/ERS 2004 GOLD 2008 NICE

(2010)

FEV1/FVC Post-

bronchodilator

FEV1%

predicted

Post-bronchodilator

Post-bronchodilator

Post-bronchodilator

< 0.7 80% Mild Stage 1 (mild)

Stage 1 (mild)

< 0.7 50–79% Mild Moderate Stage 2

(moderate)Stage 2

(moderate)

< 0.7 30–49% Moderate Severe Stage 3

(severe)Stage 3 (severe)

< 0.7 < 30% Severe Very severeStage 4(very

severe)

Stage 4(very

severe)

Grading Severity

52 year old female

smoker of 35 years

Dx of asthma since early

20’s

61  year  old  male  smoker  frequent  

exacerbations  

Notable   barrel  chested  with  productive  cough

49 year old male

Smoker with 30 yrs pack

hx

BMI 16

Evidently dyspnoeic

even at rest with ++ use of accessory muscles Vt

COPD v Asthma

� NICE Guidelines:

¡ “Clinically significant COPD is not present if FEV1 and FEV1% return to normal with drug therapy”

¡ “Asthma may be present if . . There is a 400ml response to bronchodilators. . . .or 30mg prednisolone for 2/52”

Summary: COPD vs Asthma

Features COPD Asthma

Smoker? Nearly all Possible

Symptoms under age of 35 Rare Common

Chronic productive cough Common Uncommon

Breathlessness Persistent Variable

Night-time waking with SOB/wheeze Uncommon Common

Duirnal or day to day variation in symptoms? Uncommon Common

Remember Asthma and COPD may both be present