Asthma (ILO/IMO Guidelines Appendix E J45-46)

Introduction

Asthma is a chronic condition characterised by inflammation within the airways. Symptoms are usually episodic and include cough, wheezing, chest tightness and breathlessness. Episodes may last from a few minutes to several weeks and vary in severity from trivial to fatal. Episodes may be provoked by various factors. Respiratory infections are the commonest cause but more transient episodes may follow exercise, especially in cold dry air, or exposures to allergens or respiratory irritants. Some episodes appear to occur spontaneously but these are rarely severe. An individual with asthma may be affected by one or more of these factors. Asthma can occur at any age but is most common in childhood. Many children with asthma grow out of their symptoms during their teen age years. Occupational asthma may also occur in a previously unaffected individual as a result of sensitisation to certain chemicals and organic materials which are encountered in the course of work, some of which are found at sea. Modern treatment of asthma is very effective and results in good control of symptoms in most patients.

Impairment and risk

The importance of asthma in relation to fitness to work at sea lies in the possibility of an acute episode occurring while at sea leading to a severe or life threatening illness where the medical support required for appropriate treatment is unavailable.

Rationale and justification

• There is no evidence about asthma risks in seafarers beyond case reports. Hence information from onshore studies needs to be used.
• A history of asthma is common in cadets entering seafaring.
• Asthma is very common in children; although > 25% have such a diagnosis recorded in their clinical notes the true prevalence is closer to around 15%. A large proportion of those with true childhood asthma cease to have symptoms in their teens, but some continue to have hyper-reactive airways and an asthmatic response to irritants and allergens into adult life.
• People whose asthma is reliably controlled by regular use of a preventer inhalers (corticosteroid or long term beta agonists) and with only occasional use of supplementary short term reliever bronchodilators rarely develop severe and potentially life threatening episodes.
• Test methods can sometimes be used to detect the causes of asthma Specific immunoglobulin levels may be raised by some agents causing asthma.

Classification of asthma as an aid to decision taking

Childhood Asthma

• Mild – few or no hospitalisations, normal activities between episodes, controlled by inhaler therapy alone, remission before age 16, normal lung function
• Moderate – few hospitalisations, frequent use of reliever inhaler between episodes, interference with normal exercise activity, remission before age 16, normal lung function
• Severe – frequent episodes requiring treatment to be made more intensive, regular hospitalisation, frequent oral or iv steroid use, lost schooling, abnormal lung function

Adult Asthma

Asthma may persist from childhood or start over the age of16. There is a wide range of intrinsic and external causes for asthma developing in adult life. In late entry recruits with a history of adult onset asthma the role of specific allergens, including those causing occupational asthma should be investigated. Less specific inducers such as cold, exercise and respiratory infection also need to be considered. All can affect fitness for work at sea

• Mild intermittent asthma – infrequent episodes of mild wheezing occurring less than once every 2 weeks, readily and rapidly relieved by beta agonist inhaler
• Mild asthma – frequent episodes of wheezing requiring use of beta agonist inhaler or the introduction of a corticosteroid inhaler. Regular use of a preventer inhaler may effectively eliminate symptoms and the need for more than occasional use of a rapid acting bronchodilator reliever inhaler.
• Exercise induced asthma – episodes of wheezing and breathlessness provoked by exertion especially in the cold. Episodes may be effectively controlled by either long-term preventer inhalers, short term reliever inhalers used prior to or during exercise or by oral medication
• Moderate asthma – frequent episodes of wheezing despite regular use of inhaled steroid (or steroid/long acting beta agonist) treatment requiring continued use of frequent beta agonist inhaler treatment, or the addition of other medication, occasional requirement for oral steroids.
• Severe asthma – frequent episodes of wheeze and breathlessness, frequent hospitalisation, frequent use of oral steroid treatment.

Reactive Airway Dysfunction Syndrome

Onset over age 16 following chemical inhalation incident. This is characterised by non-specific airway hyper-reactivity brought on by irritants, cold etc and will follow a single severe overexposure to an irritant such as chlorine or ammonia. It is likely to limit fitness for work at sea.

Assessment and decision taking

Note: the detail of recommendations given here reflects more recent expert advice than recommended criteria in the ILO/IMO Guidelines. Hence they are not completely compatible as they accept the controlled use of some forms of long-term preventer medication.

• First determine how the asthma is classified, using the above criteria? Essentially the clinical pattern of past episodes and the therapy required is a good assessment of severity/control; and a useful indication of the likely pattern of future episodes.
• What is the pattern of past responses? How frequent have they been and is there a pattern to their severity such that each is more severe than the one before? Do episodes regularly follow a particular provoking factor such as a respiratory infection, exercise in cold air or exposure to other irritants? This information may be a guide to the nature of future episodes, but respiratory infection in particular does not consistently produce an asthmatic response.
• Is there evidence of an allergic cause for the asthma? This is less common but important because the features of increasingly severe reactions and the need to avoid exposure totally to prevent recurrence are specific to allergy and may sometimes be the major reason for deciding that a person is unfit. If the causal agent is known it may be possible to determine whether it is likely to be present at sea. Thus exposure to cats will usually be avoided at sea (if not in port), but house dust mites are likely to be present.
• Is prevention solely based on avoidance or is any medication used? If medication is required then some degree of surveillance may be needed.
  • What oral medications are or have recently been used? Oral steroids may be an indicator of a significant episode.
  • Are inhalers used? If used for prevention are they taken regularly or only from time to time? If beta agonists are used to relieve episodes of bronchospasm how frequently are they used? Prescribing data from the doctor treating the person may give useful additional information on inhaler use.
• Does the sufferer self treat in the event of an episode? This will require assessment in terms of the acceptability of the medication at sea and the consequences of any failure to control symptoms effectively.
• How secure is the diagnostic information? An applicant who is concerned that asthma may have an adverse effect on the issue of a certificate is likely to minimise the severity of their condition and to overstate the effectiveness with which it is controlled. If the pattern of the condition and the effectiveness of its treatment is supported by a detailed medical report from the doctor treating the person then decision taking may have a firmer foundation. If there are doubts about severity then a medical report should be obtained and, if it is from a chest physician, the potential value of non-specific challenge testing to estimate current reactivity should be raised. In requesting a report it is important to indicate the reasons for needing it – as in 'Impairment and risk' on page 1.

Note: If an occupational cause for asthma that is present in the person's current pattern of employment is found it is important that the ship operator is made aware of this, this may be directly with the consent of the individual or by informing the MCA of the details of the case and providing contact information for the operator.

In all cases where the classification of the person's asthma is in doubt an assessment by a specialist chest physician should be undertaken.

Conditions for certificate issue

1. For anyone who uses preventer inhalers their continuing use as prescribed will be made a condition of certificate issue. Sufficient medication must be taken aboard to cover the longest anticipated period before a return visit to the treating doctor. If a clinical decision is taken that the use of preventers should be stopped or modified the seafarer will need to be re-assessed and a period ashore may be needed to confirm that the change has not increased the risk of future episodes.
2. Anyone who uses reliever inhalers must take aboard sufficient to cover twice the current level of use for the longest anticipated period before return to the treating doctor.
3. Increased medication use is an indicator that the control of the asthma is not longer adequate and the seafarer should be advised to obtain medical advice at the next available/possible opportunity.
4. Seafarers should be given and carry a 'to whom it may concern' letter indicating their treatment regime, the fact that the validity of their certificate is conditional on maintaining any prescribed treatment and the need for medical assessment in the event of any problems with control. They should be advised to show this to the captain or responsible officer on embarkation.

Testing of lung function and bronchial reactivity

As spirometry frequently does not show any abnormalities between attacks of asthma it is an insensitive measure of either diagnosis or severity. A period of peak flow monitoring 4 times a day is more useful as an indicator of bronchial reactivity. Bronchial reactivity testing in the presence of possible asthma is a valid but hospital-based means of assessment. Various protocols using different provoking agents are used. Exercise will also act as a trigger and has been used in the armed forces and is an easier to use but equally valid predictor of future asthma risk.

Exercise testing for bronchial hyper-reactivity may be undertaken by an appropriately equipped Approved Doctor (who may charge an additional fee for performing this test). Alternatively, either exercise testing or other forms of reactivity testing may be undertaken at a specialist clinic. Access to facilities for exercise testing is likely to be particularly useful for those ADs who do a large number of medicals on potential new recruits. The recommended procedure is:

• Ask all recruits about asthmatic symptoms and check PEFR (peak expiratory flow rate)
• If there is a history of asthma or recorded PEFR is more than 75l/min below predicted PEFR perform exercise testing
• Measure FEV1(Forced Expiratory Volume in 1 second), FVC(forced vital capacity) and PEFR at rest
• Exercise on treadmill until applicant reaches 80% maximal heart rate, then stop
• Repeat spirometry at 1,5,8,10,12 minutes post exercise
• If FEV1 falls by >15% of pre-exercise level (typically at 8 minutes post exercise), there is a residual asthmatic tendency.