Lung disorders

Active asthma

Bronchiectasis

Chronic obstructive pulmonary disease (COPD)

Cystic fibrosis

History of spontaneous pneumothorax

Interstitial lung disease

Lung cysts or bullae

Marfan syndrome

Chronic hypercapnia

Cardiovascular disorders

Heart failure

History of significant ventricular arrhythmias

Hemodynamically significant intracardiac shunt or any right-to-left shunt (eg, atrial septal defect, tetralogy of Fallot)

Coronary artery disease

Psychologic disorders

Panic or phobia

Structural disorder

Unrepaired hernia

Neurologic disorders

Seizure disorder

Recurrent syncope

Metabolic disorders

Extreme obesity

Type 1 or type 2 diabetes mellitus treated with insulin (a relative contraindication)

Ear, nose, and throat disorders

Untreated allergic rhinitis

Perforated tympanic membrane

Upper respiratory infection

Pregnancy

Possible risk of birth defects and fetal injury due to decompression sickness

Habitual air-swallowing

Gastrointestinal overinflation during ascent due to swallowing pressurized air at depth

Poor exercise tolerance

Inadequate physiologic response to adverse diving conditions

Severe gastroesophageal reflux

Aggravated by loss of gravity effect on the abdomen during submersion

Children < 10 years

Incomplete understanding of the physics and physiology needed for safe diving