Predicting risks of asthma recurrence

Stephen WattConsultant in Respiratory and Hyperbaric

MedicineAberdeen Royal Infirmary

AsthmaHazards at work

• Inability to do job (restricted work capacity)

• Frequent periods of illness• Sudden incapacity to do critical tasks• Exposure to sensitisers• Outcome of acute episodes in remote

locations

AsthmaAssessment of fitness for work

• “Certificate of fitness”–misleading and misunderstood– often rigid application of guideline

• Medical assessment = risk assessment– transparent– logical– understood by patients

Asthma

• Definition – no gold standard• Clinical diagnosis– Cough, wheeze, breathlessness, chest

tightness + variable airflow obstruction– Pathology involves airway hyper-

responsiveness and inflammation

• Very common

Asthma in Children

• Diagnosis– Cough, SOB occur with viral infections– Frequency, diurnal variation, triggers, atopy, family

history, response to Rx

• Prognosis– Age > 2 - < 2– Sex – Female > Male– Frequency of episodes– Severity– Atopy– Family history– Abnormal lung functuion

Asthma in Adults

• Patterns of disease– Episodic

• atopy, infection, exercise

– Persistent• Severity

– Mild (acute episode history)– Moderate – Severe (therapy history)

– Brittle– Cough variant

• Impact of therapy

Prevalence

• Problems with diagnosis– Wheeze ever, episode in last year, treatment =

8.1%– 2001 health survey

• Wheeze in last year 15-20% age up to 55• Diagnosis of asthma 10-15% age up to 55

• Very common

Asthma mortality

• Approx 1200 asthma deaths in UK pa

• Age specific mortality– Children and adults <45 = >1 per

100,000– Adults 45 – 64 = 2 per 100,000– Adults > 65 = 10 per

100,000

Asthma morbidity

• Is survival dependent on benefit of medical care?

Asthma morbidity

• Asthma is common cause for hospital admission

• But–Multiple admissions– Cause for admission• Poor compliance, panic, co-morbidity

– Small number are life threatening

Predicting the risk• Risk in this age group is very small• Risk factors for death– Age– Poor lung function– Co-morbidity– Previous severe episodes (hospital admissions)– Previous near fatal episode– Poor compliance with treatment– No diagnosis

• Proportion of deaths occur without diagnosis

Assessing the risk

• Medical history– Age of onset– Severity (current treatments)– Symptoms (when well and when unwell)– Frequency of episodes– Control of episodes (Self management)–Monitoring PEF (where appropriate)

• Lung function

November 2008

Lung function tests

• FEV1– best of three satisfactory attempts–most reproducible test– SD is 0.5 litres• Normality 95% confidence limits = predicted

normal +- 1.67 * 0.5• Percent predicted value not helpful!

– remember ethnic correction factors

What can asthmatics do?

• Almost all jobs dependent on assessment–Manual labouring– Athletics– Police– (Firemen)– (Diver)

Where do asthmatics work?

• Altitude• Offshore• Polar regions