Review of Fitness to Dive Guidelines: Neurologic
Suggestions for Review of Fitness to Dive Guidelines: Neurologic
In our last newsletter we brought up the suggestion that guidelines placing restrictions on diving in certain conditions and with certain drugs might be too stringent and might possibly be either misapplied or archaic.
The suggestion has also been made that guidelines have been promulgated for military, commercial and professional divers based on conclusions drawn from naval diving medical officers for military personnel and that a different set of rules should be considered for sport and recreational divers. In addition, many recommendations in various guidelines are based on physician judgment and anecdotal experience and not on good clinical evidence. There is not a large body of evidence in support of many of the 'absolute' and 'relative' contraindications usually listed. However, it also can be stated that the same physical forces are acting on the same human body when anyone descends beneath the surface, and that immutable physical laws should apply across the board. This is certainly true but it is the strict application of rules without any 'wiggle room' that is vexing to many people.
In the final analysis for many of the restrictions, it is actually the amount of risk that an individual is willing to take in order to participate in sport diving. Glen Egstrom, PhD wrote this about risk associated with diving:
"Scubadoc- I read your newsletter with the usual amount of stimulation. I feel that an old (1787) Ben Franklinism fits here very well. He observed “Having lived long I have observed many instances of being obliged by better information and for consideration to change opinions even on important subjects which I once thought right but found to be otherwise.” The evolutionary changes in the view of the relative levels of risk associated with diving often have the appearance of lowering levels of concern on the part of the medical and instructional communities of divers. I prefer to view it as a heightened appreciation for the nature of the risk vs. benefit evaluation. Risk assignment should be based upon objective, scientific analysis of a hazardous condition. The benefits, often less quantifiable, should be viewed in terms of physical as well as mental health aspects. The nature of the calculated risk should be clearly explained to the individual on the basis of the objective evidence. Most individuals, armed with specific knowledge about their fitness to dive and the risks placed in perspective, are likely to make good informed decisions. For those who do not pay attention, they will probably continue to let their minds make appointments that their bodies cannot keep. As is their right as an individual.
It has always been easier to be arbitrary and overly restrictive than it has been to get good evidence for a balanced opinion. I personally have always felt that regular doses of hyperbaric “therapy” in the form of diving have provided benefits to my life that make the risks more than acceptable. Good luck on your project, it could be a real challenge! "
Revisiting the "Absolute Contraindications" to diving - as outlined by various organizations such as the RSTC and NOAA and copied by most of the certifying agencies, turns out to be a difficult project, as there are few studies to be found that back up their recommendations. Making the guidelines more lenient turns out to be just as difficult - again because there are few suggestions that can be based on evidence. Expert opinion and anecdotal evidence are generally the substantiating factors in making decisions about fitness to dive. The obvious reasons why a person should not be allowed to dive are as follows:
* Disorders that lead to altered consciousness
* Disorders that inhibit the "natural evolution of Boyle's Law"
* Disorders that may lead to erratic and irresponsible behavior.
In our last newsletter, http://scuba-doc.com/nl041505.html , we looked into the ear, nose and throat. Today, we will investigate the evidence supporting the neurological restrictions.
RSTC Contra-indications
Neurologic abnormalities that affect a diver's ability to perform exercise should be assessed individually based on the degree of
compromise involved.
Absolute Contraindications:
Abnormalities where the level of consciousness is subject to impairment put the diver at increased risk of drowning. Divers with spinal cord or brain abnormalities where perfusion is impaired are at increased risk of spinal cord or cerebral decompression sickness.
. History of seizures other than childhood febrile seizures
. Intracranial tumor or aneurysm
. History of TIA or CVA
. History of spinal cord injury, disease or surgery with residual sequelae
. History of type II (serious and/or central nervous system) decompression sickness with permanent neurologic deficits
Relative Contraindications:
. Migraine headaches whose symptoms or severity impair motor or cognitive function
. History of head injury with sequelae other than seizure
. Herniated nucleus pulposus
. Peripheral neuropathy
. Trigeminal neuralgia
. History of spinal cord or brain injury without residual neurologic deficit
. History of cerebral gas embolism without residual (pulmonary air trapping has been excluded)
. Cerebral palsy in the absence of seizure activity
NOAA Absolute Contra-indications
Neurological
· History of Seizure disorder: After head injury, disallow diving during that period of time that the diver is at risk for seizures
http://www.scuba-doc.com/epildv.htm
Risk Assessment
No evidence exists that diving with compressed air scuba to the accepted 130 fsw limit increases the risk of epileptic seizures. One is no more likely to seize while diving than while driving: the risk is the same. There is no useful data to determine the potential for injury in divers with epilepsy. So the assessment of risk is mostly subjective rather than objective.
The general position that any sedating medication (includes those controlling epilepsy) is enhanced by high partial pressures of nitrogen is unproven. With the exception of very few studies, this is an assumption.
The position that seizure activity can be triggered by underwater pressure due to increased O2 pp has been shown to occur in a low percent of all dives. Increased seizure activity in epileptics due to glare, flickering light, psychological factors, cold water, hyperventilation or anxiety is unproven.
Recommended convulsion-free intervals on and off medication are highly variable depending upon the locale and are somewhat based upon the regulations concerning driving with epilepsy. (There is an increase of 1.3-2.0 times the accident rate in seizure free drivers). However, persons with seizure history are not passed as fit to pilot an airplane.
The risk of drowning or pulmonary barotrauma are high for any loss of consciousness.
Fitness to Dive?
From a 'common-sense' point of view it would appear that the risk of accident to the diver and associates is too great to approve a person with epilepsy as 'fit to dive'.
· Intracranial tumor or aneurysm
Our assessment:
The risk of both of these untreated diagnoses would be the same as on the surface - hemorrhage with loss of consciousness. The big difference is that underwater, drowning will surely occur.
Therefore, the risk of LOC is highly variable but present.
Increased risk of DCS has not been reported, to my knowledge.
The possibility of erratic and irresponsible behavior would seem to be minimal and not brought on by diving with these entities.
Ability to self and buddy rescue variable.
Fitness to dive?
It would probably be unwise to dive with these conditions unless treated and stable for a long enough period of time to assess the possibility of seizures.
· History of TIA (transient ischemic attacks) or CVA (cerebral vascular accidents)
See http://www.scuba-doc.com/tia.htm
Assessment:
TIAs and CVAs are both associated with an increased incidence of arterial disease and are apt to reoccur.
The risk of LOC is increased and certain diving activities can increase the intracranial pressure (Valsalva, straining) possibly increasing the risk of hemorrhage.
Most diving physicians feel that an area of deranged vascularity increases the risk of nitrogen bubble accumulation and DCS. (unproven?)
There would be no increase in erratic or irresponsible behavior.
There is the possibility of decreased ability to self and buddy rescue.
Fitness to dive?
Absolute restriction on sport diving seems draconian and each instance should require a case-by-case decision, made with the advice of the treating physician, family and diving partners. Consulting a neurologist familiar with diving medicine is also advisable. New divers should not be certified as fit to dive. Experienced divers should be assessed on a case by case basis.
· History of spinal cord injury, disease or surgery with residual sequelae.
This includes a history of having had Type II neurological DCS with permanent neurological deficits.
Risk Assessment
LOC not applicable
The risk in this situation is mainly the fear of further damage to the previously scarred spinal cord tissue from decompression injury.
Erratic and irrsponsible behavior is not applicable.
Ability to self and buddy rescue is problematic.
Fitness to Dive?
Reinjury to a previously damaged spinal cord would be disastrous and these divers should not be allowed to sport dive.
· Episodic loss of consciousness
A history of unexplained syncopal episodes, whether cardiovascular or neurogenic.
Until diagnosed and treated effectively, this is a valid contra-indication.
· Recurring neurologic disorders (ie: multiple sclerosis)
See http://www.scuba-doc.com/msdiv.htm
Risk Assessment
Risk factors are inability to self and buddy rescue, confusion of diagnosis of decompression accident.
Loss of consciousness is not a risk factor.
There is no evidence of increased risk for DCS.
Most people with this condition have no change in their personality and behave quite responsibly.
The condition comes and goes and is characterized by remissions and exacerbations.
Fitness to Dive?
Absolute contra-indication to sport diving seems overly restrictive and each instance should require a case-by-case decision, made with the advice of the treating physician, family and diving partners. Consulting a neurologist familiar with diving medicine is also advisable.
· Peripheral neuropathies associated with weakness or significant pain or sensory loss, or that it is recurrent/progressive, is disqualifying
Risk assessment:
Loss of consciousness is not a factor
Increased susceptibility to DCS is not reported as being a problem.
Confusion with the signs and symptoms of DCS would be a significant factor.
Behavior is not a problem.
Self and buddy rescue might be a significant problem.
Fitness to dive?
Absolute restriction on diving seems harsh and each instance should require a case-by-case decision, made with the advice of the treating physician, family and diving partners. Consulting a neurologist familiar with diving medicine is also advisable.
NOAA Relative Contra-indications
Neurologic
· Migraine: Those persons who have migraine with any of the following should not dive:
Aura, impairment of one of the senses, nausea and vomiting or photophobia.
This should not be a restriction in the sport diver. Obviously, a diver should not dive during an attack or if diving is known to bring on an attack. The relationship of PFO and migraine with aura should be restrictive.
· Head injuries: Persons can be cleared for diving following head injuries if they have no
history of: intracranial hemorrhage
· Brain contusion:
- Unconsciousness lasting 24 hours or longer
- Unconsciousness lasted 2-24 hours and the person has been seizure free for 2
years
- Unconsciousness lasted less than 2 hours and the person has a normal
neurological workup.
- Person is neurologically normal one year after experiencing 3-4 weeks of
amnesia.
- Neurologically normal nine months after experiencing 2-3 weeks of amnesia.
- Neurologically normal 6 months after amnesia for 1-2 weeks
- Neurologically normal 6 weeks after momentary amnesia.
· Simple febrile seizures: Seizures accompanying febrile episodes below the age of 6 with
no history of abnormal neurological exams, seizures of longer than 15 minutes duration
or non-febrile seizures in family members.
· Ruptured disc without neurological or physical impairments. Successful disc surgery below L1-L2 and uncomplicated, successful cervical disc surgery from an anterior
approach after 3 months.
· CNS (brain or spinal cord) decompression sickness with complete resolution of signs and symptoms within 24 hours.
· Cerebral gas embolism with complete resolution of signs and symptoms within 24 hours
assuming no complications from pulmonary considerations
· Brain surgery (tumor or aneurysm)
posted by Ern Campbell, MD, @ 12:30 PM
