The following recommendations and guidelines is relative conservative and it may only apply to sport divers. Any unclear information and further advice should be obtained from your diving physician.
Contents of FAQ in Diving Medicine

Cardiovascular Problems

1. 1. Coronary Artery Disease (CAD)
      Ideally, one would like to establish a baseline and periodic cardiovascular screening program for all divers, which would provide laboratory determination of serum lipids, risk factor analysis, resting and exercise electrocardiography and exercise scintigraphy. Scuba diving candidates over the age of 40, and poorly conditioned diving candidates under 40 should have an exercise electrocardiogram for assessment. To participate in scuba diving, approximately 13 METS should be achieved in exercise electrocardiogram. In the presence of an abnormal exercise ECG, such a candidate may be tested with exercise ECG with scintigraphy and, if possible, coronary angiography.
      
      Those divers with symptoms of angina pectoris, history or finding of myocardial infarction arrhythmias due to CAD represent contraindications to diving.
      
      In rare exceptional individuals who undergo successful coronary angioplasty and coronary re-vascularization and those who recover from discrete, non-complicated myocardial infarctions, who have completed rehabilitation programs with life-style and risk factor modification can be evaluated individually for diving. Return to diving would be only after the usual non-invasive testing procedures by cardiologist to rule out myocardial ischemia. Drugs which alter cardiovascular response to exercise is not acceptable and risk of drowning and risk to their diving buddies must be advised. Regular check-up by cardiologist with experience in diving medicine on an annual basis and maintain a high level of physical conditioning to avoid excess cardiovascular stress in diving.
      
      
   2. Hypertension
      Hypertension controlled by weight loss, salt restrictions and exercise, diving can be safe. Further, well controlled by these measures plus diuretics can also continue to dive. Due to the potential need to increase the cardiac output in response to heavy exercise in a diving emergency requires that those taking beta blocking agents or other drugs which produce significant blockade of the nervous system should demonstrate adequate performance on an exercise test to 13 METS. All hypertensive patient with left ventricular hypertrophy, left ventricular dilation or left ventricular dysfunction should not continue diving , even if blood pressure is controlled. Current recommendation on chooses of anti-hypertensive medication for divers are from ACE inhibitor and Calcium channel blockers rather then from beta-blocking drugs.
      
      
   3. Valvular Heart Disease
      For mitral regurgitation, if no evidence of left ventricular function and asymptomatic with minimal left ventricular dilation on ECG and echocardiogram that diving can be continues.
      
      Aortic insufficiency with hemodynamically insignificant changes and asymptomatic can be qualify for diving. However ECG and echocardiogram must show no left ventricular hypertrophy, minimal left ventricular dilation, and no left ventricular dysfunction.
      
      Any other degree of aortic stenosis or mitral stenosis is considered disqualifying for diving since they impede forward flow during exercise and pulmonary edema and/or syncope will be the result. Diver with asymptomatic Mitral valve prolapse are fit for diving except medication, chest pain, palpitation, arrhythmias, syncope, dyspnea complicating the disease.
   5. Congenital Heart Disease
      ANY DEFECT WHICH ALLOWS A COMMUNICATION BETWEEN THE RIGHT AND LEFT CIRCULATIONS AT THE LEVEL OF THE HEART OR GREAT VESSELS SHOULD CAUSE DISQUALIFICATION.
      
      Divers who have had successful repair of non-cyanotic lesions, such as atrial septal defects, patent ductus arteriosus and ventricular septal defect, may be cleared for diving after evaluation by a cardiologist and by a chest physician.
      
   6. Pacemakers
      In general, patients who require permanent pacemakers are disqualified for diving due to their underlying cardiac disease. The only possible exception to this may be the young individual with congenital third degree A-V block who need full evaluation by their cardiologist to evaluate their functional status and the pacemaker's ability to perform physiologically. Besides, pacemakers have been tested in hyperbaric chambers and showed no change in performance or structural integrity under increased barometric pressure, such tests would be required before considering diving with pacemakers. Those healthy divers with supraventricular arrhythmias treated with catheter AV node destruction on implanted pacemakers may also be suitable for diving.
      

Pulmonary Problems

1. 1. Bronchial Asthma
      All exercise-induced asthma is considered an absolute disqualification for scuba diving.
      
      Any patient with currently active bronchial asthma should be advised not to dive. Any patient with a history of childhood asthma, symptoms suggestive of asthma within the past year, suspicion of exercise or cold air conduced asthma should be referred to a pulmonary medicine specialist for valuation. Current data shown that an asthmatic diver who demonstrated to be have normal resting and post-exercise lung function test is not at risk when diving. However, medication for acute asthma control within 48hours before diving is not acceptable.
      
      ONE CAUTIOUS REMINDER MUST BE REPEATED: THE GREATEST VOLUME CHANGES IN THE LUNGS OF ANY DIVER WITH AIR TRAPPING OCCUR AT SHALLOW DEPTHS. NEVER CLEAR A PERSON FOR-SHALLOW DIVING ONLY THE SHALLOWEST FOUR FEET, EVEN IN A SWIMMING POOL IS THE MOST DANGEROUS DEPTH FOR COMPRESSED GAS DIVING FOR A PATIENT WITH ACTIVE BRONCHOSPASMTIC DISORDERS.

Endocrinology

Diabetes Mellitus
Current recommendation is that no diving for those with insulin dependent diabetes mellitus (IDDM) or with non-insulin dependent diabetes mellitus (NIDDM) if there is a history of hypoglycemic episodes. A diabetic diver without any complication is qualified to dive even oral hypoglycemic medication is necessary for diabetic control.

Ophthalmology

1. Ophthalmic contraindications to diving: Intraocular gas, Intraocular hollow implant, and inadequate vision for underwater functioning.

   Special considerations regarding common ocular disorders :
   

   1. Glaucoma and Ocular Hypertension
      The existence of glaucoma or ocular hypertension can practice diving as long as adequate visual acuity and visual fields exist. A candidate using Timoptic should be cleared by a cardiologist for diving (the use of Timoptic eye drops can affect the heart rate and response to stress).
      Diving can continue after a successful Laser trabeculoplasty for treatment of glaucoma. Duration of convalescent times after eye surgery should be consulted with diver's ophthalmologist.
      
   2. Retinal detachment
      Repaired or laser photocoagulation in retinal detachment patient can continue diving provided a regular ocular examination by ophthalmologist maintained.
      
   3. Cataract
      Patients with cataracts who still have adequate vision and Aphakia with contact lens correction for visual acuity can dive.
      
   4. Visual Acuity corrections
      Divers who need underwater refractive correction are recommended to try soft contact lenses, corrective lenses boned onto face mask surface or prescription-ground face mask lenses to avoid bubble formation in hard contact lenses.

      
      

Neurology in diving

Head Injuries

The main considerations on return to diving after head trauma are on its residual neurologic deficit which would interfere with performance and the risk of post-traumatic seizures. History of intracranial haemorrhage, brain contusion, seizures that occur soon after the injury, or prolonged unconsciousness or amnesia all raise the risk of post-traumatic seizure disorders. Advice from neurologist or neurosurgeon should be follow.

Migraine sufferers who have shown any of the following unpredictable sudden onset of an aura with impairment, notably vision, loss of sensation or function of a hand, cause produce severe mood alterations or, in the case of basilar artery migraine, causes vertigo, diplopia or clouding of consciousness or the severe headache accompanied by nausea, vomiting and photophobia may suddenly impair a diver's ability to function safely underwater and should be disqualified for diving. Exception will be allowed for those well controlled with medication.

Seizure Disorders
Major or minor seizure disorders is absolutely disqualifying for diving, regardless of control by anticonvulsant medication. The attack may be preceded by a warning or aura which is usually momentary and may be a motor, sensory or emotional change, indicating the part of the brain where the discharges start. The typical periodic breathholding during the tonic and clonic phases of a major seizure make rescue, bringing the diver to the surface, an especial risk for pulmonary overpressure accident with resulting pneumothorax or arterial gas embolism.
Febrile convulsion occur in childhood which do not have any abnormal neurological changes, long duration of seizure or positive family history of non-febrile seizures are safe to dive. A history of episodes of unconsciousness early in life should evoke evaluation. The neurological evaluation at the time of the episodes may have included EEG, but normal EEG would not overrule a good clinical impression that the attack was due to epilepsy. A history of epileptiform seizures in childhood is disqualifying for diving unless there is good evidence they were simple febrile seizures.

Spine Injury
Incidence of DCS occurs relative higher in injured parts of the body and injured spine therefore it should be mention to divers. A history of spinal cord trauma with neurologic deficit should be cause for disqualification, with or without residual deficit. A history of Guillain-Barre Syndrome, Brown-Sequard Syndrome, degenerative joint disease as seen with spinal stenosis and cervical disc disease with peripheral sign are all considered disqualifying. Rare exceptions can be reviewed case by case by diver's

History of Cerebrovascular Accident
Diver with a history of cerebrovascular accident should be disqualification for diving. Even though function has apparently been restored, the likelihood of loss of neural reserve and possible local CNS hypoperfusion make serious CNS decompression sickness more likely. While a history of transient ischemic attack is also disqualifying.

Trigeminal Neuralgia
Those divers with a trigger zone in the face mask contact area could suffer attacks during diving or donning diving gear. Trigeminal neuralgia attack with severe pain can induce a panic attack which is not acceptable underwater and therefore not fit for diving.

Peripheral Neuropathy
Diver with peripheral neuropathy needs individual evaluation regarding underlying disorders and functional disability, which could interfere with diving activities. In general, disqualification must be advised because of inability to differentiate neuropathy from decompression sickness in diving. Known sensory loss, which may result in severe, undetectable injury from diving, is also disqualified.

1. 1. 1. Gastrointestinal system in diving

   Esophageal diverticula, significant free gastroesophageal reflux, achalasia, sliding hiatal hernia are not fit for diving.

   Gastric outlet obstruction, severe post-gastrectomy dumping syndrome is disqualifying for diving.

   Small intestine obstruction, continent ileostomy and exterocutaneous fistulae are disqualify for diving.

   Significant fatty liver is liable to have inert gas excess and rupture of fat cells resulted in unfit for diving.

   
   The above information provided by Dr Ronson C.T. LI