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4.2 Manifestations. There are a number of manifestations of decompression ­illness which occur commonly and these are outlined below. They may occur alone or in combination. Occasionally, unusual cases occur and in such instances, the use of additional descriptive terms may be required.

 4.2.1 Pain

 (a) Limb Pain. This is probably the most frequent manifestation of decompression illness. It is used to describe the deep aching pain in or around one or more joints which may begin during decompression or after completion of a dive. Following 'bounce' dives, the upper limbs tend to be involved more often than the lower limbs and the shoulder is involved particularly frequently. Conversely, in saturation divers, aviators and compressed-air (caisson) workers, it is the lower limbs and particularly the knees which are involved most commonly. The pain usually begins gradually and is poorly localized; it may resolve spontaneously and is then known as a 'niggle'. Niggles may flit from joint to joint. If the pain gets worse, it becomes more readily localized and is described as a dull, boring ache, similar in character to tooth ache. Sometimes the joint is held in a particular position that is least painful, but pain is seldom made worse by movement. If the pain is in a lower limb, weight bearing may be poorly tolerated on that limb. On examination, there are often no objective signs. Occasionally, there is a skin rash over or adjacent to the affected joint. Notably, the 'classical' signs of inflammation: redness, swelling, warmth to the touch and tenderness are missing.

Even cases of apparently straight-forward limb pain must be FULLY EXAMINED. A patient in pain may not notice mild paresthesia or a small area of numbness. Ensure that no neurological symptoms can be detected before the choice of a therapeutic table is made. Limb pain decompression illness usually resolves completely, even without treatment over a period of 12-72 hours. However, deliberate withholding of recompression is difficult to justify. Not only is rapid relief of pain usually obtained but, particularly in cases where there has been a rapid onset of pain after surfacing, the onset of subsequent neurological symptoms may be prevented.

(b) Girdle Pain. This is a poorly localized, aching or 'constricting' sensation which is generally in the abdomen, pelvis, or occasionally, in the chest. Girdle pain in the context of DCI is generally considered ominous since it frequently portends neurological deterioration.

 4.2.2 Neurological.

Involvement of the nervous system may be subtle, multifocal and consequently of bewildering variety and very difficult to localize. Both the central and peripheral nervous systems may be involved and the manifestations can be broken down into the loss of certain functions: higher functions, which would include aberration of thought processes or affect, loss of memory, dysphasia etc; alteration to the level of consciousness, including seizures; loss of co-ordination: loss of strength or sensation with almost any distribution: dysfunction of special senses and loss of sphincter control, especially of the bladder. It is likely that many of these disorders involve the brain. In these cases, some loss of consciousness to the point of disorientation is a frequent finding and coma may occasionally ensue. Visual symptoms are common, as are motor and other sensory deficits. Because this disease may be subtle, it is most important that a diving supervisor knows his divers. Otherwise signs such as a change of mood, dulling of intellect and loss of short-term memory may go unrecognized.

 4.2.3 It is apparent that the spinal cord is also involved in neurological decompression illness with some frequency. It may appear to be involved alone or with other parts of the nervous system.

 4.2.4 Dives which readily appear to provoke disease with a predominantly spinal cord distribution are short, deep dives with a rapid ascent to the surface. The onset of symptoms commonly occurs shortly after reaching the surface, with about half of serious cases becoming symptomatic within 10 minutes. Less than 10% of serious cases present more than 4 hours after completing the dive. In severe cases, the condition is often heralded by the onset of girdle pain. Shortly afterwards, the patient may notice pins and needles, numbness and muscular weakness in the legs which rapidly progresses to paraplegia. It is possible for all four limbs to be involved and, in severe cases shock may complicate the clinical picture. In less severe cases, the onset is not so dramatic and progress to paraplegia may be delayed and incomplete. There may be little in the way of girdle pain in such cases. On examination, it is often possible to determine a 'level' above which spinal cord function is apparently normal. This level is often in the lower thoracic or upper lumbar segments. It is occasionally possible to determine different levels for motor innervations and the various sensory modalities. The bladder is frequently involved. The patient may report difficulty initiating urination, but more often this will be detected by the absence of urinary output and the presence of a distended bladder on examination of the abdomen.

 4.2.5 Unless the fulminant (means sudden and severe) condition is rapidly treated by recompression, a complete recovery is unlikely. The prognosis for cases with a less dramatic onset is better. Even without recompression some spontaneous improvement generally occurs. Nonetheless, improvement will be more rapid and complete with recompression.

 4.2.6 Audio-Vestibular. This is a unique subclass of neurological decompression illness. It is thought that there are two mechanisms whereby the audio-vestibular system may be involved: Barotraumas and Tissue injury caused by the formation of bubbles from dissolved gas. Possible targets of this second mechanism include the cochlea, the eighth nerve nuclei and cerebellar or cortical pathways. In individual cases it may be very difficult to distinguish between these mechanisms or sites of injury by clinical examination alone. As a consequence this term may be used to describe the syndrome which includes: vertigo (a sense of rotation), tinnitus (perception of sound within the human ear in the absence of corresponding external sound), nystagmus (uncontrolled movement of the eyes, usually from side to side, but sometimes the eyes swing up and down or even in a circular move) or loss of hearing after a dive. Nausea and vomiting may accompany these symptoms but or themselves are not sufficient to imply audio-vestibular involvement in decompression illness. Experimental and anecdotal evidence now exists to show that recompression does not appear to have an adverse affect on pathology due to round or oval window rupture. Therefore, if the mechanism of disease is uncertain, appropriate recompression therapy should be undertaken. All such cases should then be referred for specialist investigation to establish the need for further treatment of a perilymph fistula.

 4.2.7 Pulmonary. As has been mentioned before, involvement of the lungs in decompression illness may be due to two quite distinct processes: decompression pulmonary barotrauma and the cardiopulmonary consequences of massive venous gas embolism. Although the mechanisms involved are distinctly different, it may be difficult to distinguish between them immediately in a clinical setting, because many of the symptoms and some of the signs are shared: chest pain, cough, haemoptysis, shortness of breath, cyanosis and, rarely, shock. Progressive disease may be due either to a tension pneumothorax or massive gas embolism of the lungs. Where there has been a dive which has induced a low gas burden, it is most likely that a pneumothorax is the cause of the problem. This may be diagnosed clinically from the classic signs: cyanosis and respiratory distress; evidence of mediastinal shift away from the affected side; hyper resonance and reduced respiratory movements and breathe sounds on the affected side. An x-ray, if available, will confirm the diagnosis. The presentation of patients with massive, overwhelming venous gas embolism of the pulmonary circulation has been described, although it is very rare and generally associated with deep dives and missed decompression. These patients usually become symptomatic within about half an hour of reaching the surface. The condition commences with central chest pain and a cough, which may be aggravated by taking deep breaths or inhaling cigarette smoke. Breathlessness and central cyanosis follow and, shortly thereafter, signs of shock. The condition is commonly progressive and the patient may deteriorate rapidly: cardiovascular collapse, loss of consciousness and death may follow, unless the patient is recompressed. Apart from cyanosis and respiratory distress, there are no signs of a pneumothorax.

 4.2.8 Cutaneous. The skin may be affected by diving in a number of ways. Two very common manifestations of decompression, which are not generally regarded as illnesses, are suit 'squeeze' and itching in the absence of a rash. The term 'cutaneous' decompression illness should be used to describe the condition which generally presents with severe itching around the shoulders or over the trunk. After a time, this develops into an erythematous rash which may progress to cyanotic mottling or marbling of the skin. When further describing the condition, it is desirable to identify the location of the disorder.

 Rash due to decompression illness

4.2.9 Lymphatic. Occasionally, lymph nodes may become enlarged and tender and this may be associated with oedema. The skin feels thickened and may have the 'pitted' appearance of orange peel. If pressure is applied to the skin, for example by the thumb, and released after about a minute or so, a visible indentation remains.

4.2.10 Constitutional. There are a number of non-specific symptoms which occur after diving and which, if severe or if accompanied by other manifestations, may be considered part of the decompression illness’ syndrome. These include headache, fatigue, malaise (which may include nausea and, possibly, vomiting) and anorexia.

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