Textbook of Maritime Medicine

7.2.1 Navigation

Vision can be assessed using standard tests of acuity and colour vision and this is the routine practice. Many of these tests do not directly relate to the sort of visual functions needed to cope in conditions of poor visibility and at night but they are simple to apply (7.6.4.1). Hearing loss can be identified either by finding thresholds for pure tone sounds of by means of speech comprehension.  The actual contribution of the use of particular levels of visual or auditory capability as the basis for decisions on who is able to undertake navigating duties does not have a well validated basis beyond the empirical fact that both functions are essential for safety when navigating a vessel.

Cognitive abilities are critical to the correct interpretation of information from both within and beyond the vessel. Assessment of cognitive function is largely outside the scope of the medical examination process and usually depends on the person’s observed performance at their job. However in a few cases, for instance following a head injury or cerebrovascular event, or when there are concerns about a seafarer’s performance and they are referred for a medical view the current state of cognitive ability may well arise in the course of a medical examination. Referral for more detailed psychological assessment in often required. Behaviour traits, such as impulsiveness, aggression and risk taking, can also influence cognitive processing in ways that are particularly likely to put a ship into danger and again a specialist assessment will probably be needed. These are likely to come to the attention of those performing medical examinations either because of a clinical report or as a result of concerns about performance while in training or while at sea. Mental ill-health can also adversely affect cognitive performance and this is likely to be exacerbated by any concurrent misuse of alcohol or drugs (10.12 and 11.6.1)

Sudden incapacitation in a navigating officer or rating can have direct consequences for vessel safety and a significant excess risk of an incapacitating event such as a loss of consciousness from reduced cardiac function, seizure or insulin induced hypoglycaemia will limit a person’s suitability for navigation duties, unless adaptations, such as the constant presence of another crew member competent to take over their duties is feasible.

Physical abilities beyond a baseline level are not directly relevant to navigation duties as such but the officers and ratings who perform navigation watches usually have other duties, for instance vessel inspection tours, cargo handling and mooring that require agility, manual handling capabilities and stamina. All of which need to be assessed  

7.2.2 Prolonged voyages

Seafarers onboard a ship, except when it is in port rarely have access to medical care. The one exception to this being those serving on vessels with more than 100 crew – almost exclusively cruise ships – and even here a full range of facilities is not available. As a consequence any illness, or indeed injury, that arises has to be managed by crew members who have only limited training and who also have other duties to perform. The arrangements for their training, for medications and medical equipment to be carried and for access to advice, both from medical guides and from onshore telemedical services are covered in chapter 9.

Selection procedures for seafarers who are on long voyages that are out of reach of the shore need to identify any pre-existing condition that could be expected to recur, relapse, progress or have complications while at sea. A judgement needs to be made on the probability of this happening and on the importance of early onshore medical care to survival and recovery. Some account also needs to be taken of the likelihood of severe pain, which even if not life threatening, as with a dental abscess or a renal stone, will create major distress for the individual and a high level of concern among other crew members.

Examples of relevant risks:

Recurrence   

- Cardiac event

- peptic ulcer

- biliary colic

- renal colic

- low back pain

- pneumothorax

Relapse

- multiple sclerosis

- mental health problems

- obstructive lung disease

-ulcerative colitis

Progression

- diabetes

- cardiomyopathy

- liver disease

- kidney disease

Complications

- hernia

- poor dental health

- prostatic hypertrophy

The presence of one of the above conditions does not automatically make a person unfit to undertake long voyages but the risk of serious problems arising at sea needs to be assessed in each case, as does the importance of rapid intervention should a problem arise.

7.2.3 Watchkeeping schedules

Most seafaring is a twenty four hour activity. As a consequence seafarers work for periods at all times of the day and night and may also work many more hours per day than would be normal onshore. There are legal restrictions on hours worked but emergencies, pressure to arrive on time, crew reductions and at times the urge of seafarers to maximise their wages will lead the boundaries of the law being exceeded.  See 10.16 on fatigue. The scope for medical assessment of a seafarer’s suitability for watch keeping duties is limited. Adaptation may become more difficult with age as sleep patterns become more disturbed, sleep disorders such as obstructive sleep apnoea may mean that a regular daily pattern of rest is essential. Irregular eating habits can adversely affect some gastro-intestinal conditions. Medication regimes are normally based on regular periods of sleep and wakefulness and these can be difficult to adjust. However in most cases it is the subjective feelings of the seafarer about how well they are coping with watch keeping duties that will determine advice and decisions about fitness for watch keeping.

7.2.4 Emergency duties

Most crew members will have duties in the event of a maritime emergency such as a fire, collision, grounding or storm damage. These often require physical capabilities and mental resilience over and above that needed during routine duties. Medical assessment of these abilities beyond physical fitness testing  is rarely practicable but training courses in fire-fighting and safety of life, as well as emergency drills onboard provide indicators of ability. If these courses have not been undertaken recently re-attendance may be a valid form of assessment. A medical declaration of fitness to participate in such courses in mid-career may be required by the course provider. 

Physical capability testing has several dimensions: cardiorespiratory reserve as tested by step or treadmill test; muscle strength, joint flexibility, co-ordination of movement and balance. It is usually best carried out in a gymnasium rather than in a clinical setting, except where detailed medical monitoring, for instance for cardiac performance, is needed.

7.2.5 Fish catching.

Fishing requires a large proportion of the crew of the vessel, whether small and inshore or larger and fishing in distant waters to be on deck handling gear and the catch, often under adverse weather conditions. These tasks are physically demanding and so in principle a rational assessment process would identify those with poor physique or mobility problems as well as those whose health could be adversely affected by exposure to hot or cold conditions. In practice most of the people worldwide who work on fishing vessels self-select into the work and continuity of employment depends on having the appropriate physical and mental capabilities.

For distant water fisheries the same considerations apply as to any other long voyage (7.2.1), while for those who navigate fishing vessels the functional requirements are the same as for all other seafarers with these duties (7.2.1).

7.2.6 High speed vessels and fast craft.

This covers a variety of types from high speed ferries to inflatables used for rescue and patrol work. With the exception of customer service staff on fast ferries virtually all crew members will be undertaking navigational duties, but in a situation where fast response times are essential to take account of sea conditions. The criteria will be as 7.2.1 but where there is no crew protection the use of glasses to aid vision can be a problem because of spray on the lenses.  In addition there is a considerable amount of whole body vibration and this means that any musculo-skeletal problems, especially those affecting the back and neck are likely to be worsened. It is therefore good practice to screen for these both before starting work in fast craft and to consider excluding those with severe problems. The effects of vibration on those working in fast craft should always be assessed when they are examined.

If the craft have rescue duties it is important to ensure that those working in them have the physique and stamina required to ensure that the rescue team can work effectively. Such craft often have only limited protection from the weather for crew and even when this is available rescue operations will involve exposed work, often in very adverse weather conditions. Hence any excess risks from cold exposure need to be considered.

Fast craft normally return to shore on a daily basis so there is no significant risk from the presence of medical conditions of that result in health problems that only develop over a period of days (7.3.2).

7.2.7 Sail ships

Much sailing is done in the leisure sector and so does not feature in fitness for work assessment and certification. However commercial yacht masters and crews and those who act as officers on sail training ships usually come within employment related assessment regimes. Even for those who crew such vessels for pleasure there will be situations where an assessment of fitness is appropriate. The requirements for handling sails will vary with rig but specific physical capabilities may be required to handle wet sails in poor weather and to go aloft.

The requirements for navigators are as in 7.3.1 with the addition that these duties are often carried out in the open rather than on a bridge and so the ability to cope with adverse weather conditions is important. On smaller commercial charted yachts there may only be one commercially qualified yacht master, with the other crew members being effectively paying passengers with no guaranteed seafaring skills. In these circumstances sudden illness in the qualified yacht master is likely to have major implications for vessel safety and they should only be considered fit if they have no significant excess risk of incapacitating illness. Where vessels are on prolonged voyages assessment should take account of 7.3.2.