Evaluation of adults wishing to SCUBA dive

INTRODUCTION — Patients seeking to participate in recreational self-contained underwater breathing apparatus (SCUBA) diving may ask their primary care clinician for advice and an evaluation to determine if it is safe for them. Such requests may be general in nature or with specific medical conditions in mind. Whenever possible, we recommend that questions about diving fitness in patients with specific health conditions be addressed with a diving medicine specialist. Resources that include a list of specialists trained in fitness to dive examinations are available below. (See 'Resources' below.)

This topic will review basic information about fitness for recreational diving and the risks posed by common medical conditions; a comprehensive discussion of related medical complications and contraindications to diving is beyond its scope. Examinations for scientific or occupational diving have different requirements and should be performed by a diving medicine specialist. The diagnosis and management of SCUBA-related complications are discussed separately. (See "Complications of SCUBA diving".)

BASIC PHYSIOLOGY OF SCUBA DIVING — An understanding of the basic physiology of immersion and breathing compressed gas, and their effects on the body, helps to inform the evaluation of prospective divers. Nuances about differences in gas composition and the effects of extreme depth will not be considered, but basic concepts of immersion, pressure, exposure, inert gas uptake, and oxygen toxicity are discussed.

SCUBA diving can be defined simply as breathing compressed gas while immersed underwater. Most often, recreational divers breathe compressed air (21 percent oxygen), though gas composition may vary. The recreational diving depth is commonly defined as no deeper than 130 feet (40 meters), but with advanced technical diving, far greater depths can be reached.

Elements of diving with important physiologic effects include the following:

●Immersion – Immersion in water has multiple physiologic effects, including peripheral vasoconstriction leading to increased intrathoracic blood volume and right heart pressures [1]. This results in diuresis and may cause pulmonary edema in susceptible individuals, as well as potentially exacerbating underlying cardiac conditions. (See "Complications of SCUBA diving", section on 'Immersion pulmonary edema'.)

●Pressure – Changes in ambient pressure affect all air-filled spaces in the body in accordance with Boyle's law. Boyle's law states that at a constant temperature, the volume of a gas varies inversely with the ambient pressure. In other words, the volume of a gas decreases as pressure increases (descent during dive) and increases as pressure decreases (ascent from dive). Inability to equilibrate pressures may cause barotrauma, particularly to the middle ear, sinuses, and lungs. (See "Complications of SCUBA diving", section on 'Gas laws' and "Complications of SCUBA diving", section on 'Barotrauma'.)

●Gas exposure – Increased ambient pressure results in increased partial pressures of breathing gases. In the case of nitrogen, supersaturation of tissues with this gas may cause decompression sickness (DCS). In the case of oxygen, exposure to high partial pressures may lead to oxygen toxicity (either pulmonary or central nervous system). (See "Complications of SCUBA diving", section on 'Decompression sickness'.)

●Work of breathing – Work of breathing while diving increases for a variety of reasons, including immersion, body position, resistance from equipment, and increased gas density [1].

MEDICAL EVALUATION PRIOR TO DIVING — There is no standard approach to medical evaluation or re-evaluation for recreational diving. In many regions, including much of the United States, a screening medical questionnaire is given to prospective divers. This is typically done prior to initial certification or during advanced certification courses and sometimes is required by diving charter operations. If the prospective diver does not respond "yes" to any of the medical screening questions, they are permitted to proceed without any further medical evaluation. The most commonly used screening form is the Recreational Diving Medical Screening System, which was released in 2020 by the Diver Medical Screen Committee.

The physiologic changes engendered by diving are generally well tolerated, but a number of medical conditions can increase the potential for complications (table 1) [2]. The British Thoracic Society published guidelines for the respiratory evaluation of potential divers in 2003 (table 2A-B) [1]. The key points essential to clinical assessment before diving are outlined in an algorithm (algorithm 1). The rate of mishaps during SCUBA dives among participants both with and without chronic medical conditions appears to decrease when pre-dive safety checklists are used [3].

FITNESS TO DIVE

General concepts — Patients with some common medical conditions may be permitted to participate in diving under the right circumstances. As examples, patients with diabetes mellitus, hypertension, or coronary artery disease who are medically optimized and stable could dive after a careful discussion of the potential risks. When evaluating the prospective diver with chronic disease, it is important to keep the following concepts in mind:

●Diving increases stress on the cardiovascular system.

●Diving increases work of breathing and overall stress on the respiratory system.

●Any event that would render a patient even temporarily incapacitated or unconscious is potentially catastrophic underwater.

●Any condition that increases the risk of pulmonary barotrauma may result in serious harm, including pneumothorax or arterial gas embolism. (See "Complications of SCUBA diving", section on 'Barotrauma'.)

●Divers should possess the ability to exert themselves in the water and self-rescue if needed.

Physical fitness requirements — The degree of exertion required to participate in SCUBA diving varies depending on several factors including the type of diving and location. At a minimum, a diver should be able to maintain an exertion level of six metabolic equivalents of task (METs), equivalent of jogging 14 minutes/mile (nine minutes/km), with the understanding that exertion exceeding this level may be required occasionally [4]. In addition, a candidate must be a proficient swimmer. We recommend an initial screening using the Recreational Diving Medical Screening System for all prospective divers (certification courses require such screening), with additional testing and specialist input as necessary.

Absolute and relative contraindications — In general, any medical condition that impairs someone's ability to exert themselves underwater safely, such as untreated coronary artery disease or pulmonary disease, is considered an absolute contraindication to SCUBA diving (table 1). A history of spontaneous pneumothorax and pregnancy are considered absolute contraindications. In addition, any conditions that entail a risk of incapacitation or loss of consciousness, such as seizure disorders or syncope, are contraindications to diving. If stable and well managed, some conditions may be considered relative contraindications.

Below are brief summaries of common conditions, organized by organ system, that are typically contraindications to diving or require further investigation before diving is permitted. Evidence about the safety of diving with these medical conditions is limited, and recommendations are typically based on expert opinion. Expert groups that have released fitness to dive recommendations include the Undersea and Hyperbaric Medical Society (UHMS), Divers Alert Network (DAN), South Pacific Underwater Medicine Society (SPUMS), British Thoracic Society (BTS), and the UK Diving Medical Committee (UKDMC). While there is substantial overlap and general agreement among these organizations as to general guidance, there are some differences of opinion about specific conditions. Recommendations from many of these organizations are cited below.

COMMON MEDICAL CONDITIONS

Cardiovascular

Common conditions and general evaluation — Cardiovascular disease likely represents the greatest risk to divers. In the 2019 Divers Alert Network (DAN) annual fatality report, the most common cause of disabling injury among divers was cardiovascular disease [5]. Broadly speaking, the cardiovascular evaluation of a prospective diver should focus on conditions that could cause a loss of consciousness or incapacitation of any kind, impaired exercise tolerance, or increased risk for decompression sickness (DCS) or arterial gas embolism. These conditions include arrhythmia, ischemic heart disease, decompensated heart failure, and septal defects [6].

According to a 2011 consensus statement from the Undersea and Hyperbaric Medical Society (UHMS) and DAN, SCUBA diving is contraindicated for patients with the following cardiovascular conditions [6]:

●Untreated or debilitating coronary artery disease

●Cardiomyopathy

●Long QT syndrome or other channelopathy

●Arrhythmias causing episodes of loss of consciousness or exercise intolerance

●Severe valvular lesions

●Complex congenital heart disease (eg, cyanotic heart disease, unrepaired atrial septal defect)

●Automatic implantable cardioverter defibrillator (AICD)

The South Pacific Underwater Medicine Society (SPUMS) published guidelines in 2020 that added left ventricular dysfunction of any kind to the list above, with the caveat of those with an ejection fraction above 50 percent and good exercise capacity might be able to dive but require careful evaluation [7]. While the author agrees with general guidance around the contraindications listed here, individual exceptions do occur (eg, otherwise healthy and fit young adult with mild, nonobstructive cardiomyopathy may be able to dive). Such patients are best assessed on a case-by-case basis by or in consultation with a diving medicine specialist.

More challenging is screening patients with potentially undiagnosed cardiac disease at risk of an adverse event while diving. Ultimately, the extent of such screening is determined by the clinician, but it is worth noting that cardiac disease represents a significant risk, particularly to the aging diver [8].

General screening for ischemic heart disease is reviewed in detail separately (see "Screening for coronary heart disease" and "Screening for coronary heart disease in patients with diabetes mellitus"). An approach to such screening for prospective divers is outlined in the following algorithm (algorithm 2). Risk calculation tools should be used as indicated. (See "Atherosclerotic cardiovascular disease risk assessment for primary prevention in adults: Our approach", section on 'Estimate ASCVD risk using a risk calculator'.)

When performing such screening in prospective divers, we think that providers should pay particular attention to the following risk factors and signs [6,8]:

●Hypertension (with left ventricular hypertrophy being of particular risk for arrhythmia)

●Diabetes mellitus

●Dyslipidemia

●Smoking

●Family history

●Complaints of exertional chest pain or shortness of breath

DAN recommends that an exercise stress test (as opposed to imaging modalities) be used to screen for coronary heart disease in prospective divers, as it assesses both ischemic cardiac disease and exercise tolerance [6]. The 2020 SPUMS guidelines include a screening algorithm for divers 45 years and older, with a recommendation for re-evaluation every five years [7].

Hypertension — Well-controlled hypertension is not an absolute contraindication to diving but should be evaluated carefully before a patient is cleared to dive. Hypertension is a risk factor for left ventricular hypertrophy, and thus for arrhythmia, as well as for coronary artery disease [8]. In addition, hypertension likely increases the risk for immersion pulmonary edema, and prospective divers should be informed of this risk as well as its signs and symptoms [7].

Cardiac septal defects — Another frequently encountered challenge when evaluating prospective divers is screening for cardiac septal defects and providing management recommendations should such defects be discovered. Below, we discuss patent (also called persistent) foramen ovale (PFO), the most common septal defect, estimated to be present in approximately 27 percent of the population [9]. (See "Patent foramen ovale" and "Atrial septal abnormalities (PFO, ASD, and ASA) and risk of cerebral emboli in adults".)

The primary concern in divers with a PFO is the movement of venous gas bubbles to the arterial circulation via an intracardiac shunt. Venous gas bubbles occur with some regularity when diving. Their appearance increases with gas loading (increased time and depth of breathing compressed inert gas, most commonly nitrogen) [10]. The presence of gas bubbles alone does not necessarily cause disease, as they are often filtered by the capillary system in the pulmonary vasculature. However, if a right-to-left shunt exists that bypasses the pulmonary system, gas bubbles may pass to the arterial side and cause decompression illness, sometimes called a paradoxical arterial gas embolism.

The presence of a PFO is associated with an increased risk of DCS. Experts often give the risk as 2.5 times greater for DCS overall and 4 times greater for neurologic DCS. However, the degree of risk varies based on several factors including the size of the shunt. The absolute risk is low, with the estimated incidence of neurologic DCS in divers with PFO at 4.7 cases per 10,000 dives [9]. Closure of a PFO is associated with some risk, and treatment recommendations must take this into account.

In 2016, SPUMS and the UK Diving Medical Committee (UKDMC) issued a joint statement about screening and management of PFO in divers with the following recommendations [11]:

●Routine screening for PFO is not necessary for diving physicals

●Investigation of possible PFO may be needed in any of the following circumstances:

•History of decompression illness with cerebral, spinal, vestibulocochlear (inner ear), or cutaneous manifestations

•History of migraine with aura

•History of cryptogenic stroke

•History of PFO or atrial septal defect in a first-degree relative

In a joint statement, DAN and UHMS have suggested that screening for a PFO be performed in patients with a history of more than one episode of DCS associated with cerebral, spinal, vestibulocochlear, or cutaneous manifestations [12]. The author believes that divers with a history of DCS should be evaluated by or in consultation with a diving medicine specialist before returning to dive [13].

If investigation is indicated, the screening must include a transthoracic echocardiogram (TTE) with bubble contrast and provocative maneuvers to evaluate for right-to-left shunting. TTE without bubble contrast is not sufficient. A spontaneous right-to-left shunt or large, provoked shunt is likely a significant risk factor for decompression illness. The risk of decompression illness with smaller shunts is likely increased, but the magnitude has not been quantified. The decision whether to repair a PFO and/or continue diving (with possible modifications) should be made in conjunction with a cardiologist and diving medicine specialist. Following PFO closure, a repeat bubble TTE should be performed at least three months after to ensure closure [11].

Pacemakers, pulmonary edema, and other cardiac issues — Decisions about diving with a pacemaker must be made carefully, accounting for factors such as the indication for the device and the device itself. Evidence regarding safe diving practices with pacemakers is scant, but some suggest that depths should be limited (ie, deeper dives avoided) due to the possibility of device malfunction [4,10]. Each device has limitations, and these should be reviewed with the manufacturer. (See "Permanent cardiac pacing: Overview of devices and indications".)

Many experts consider a prior episode of immersion pulmonary edema to be a contraindication to diving, as there is a high risk of recurrence [4]. Risk factors may include hypertension, cardiac dysfunction, pulmonary hypertension, exertion, and a cold environment (although episodes can occur in tropical waters). Immersion pulmonary edema is likely underdiagnosed and may be a significant contributor to diving fatalities. (See "Complications of SCUBA diving", section on 'Immersion pulmonary edema'.)

Other congenital cardiac conditions are outside the scope of this topic and should be addressed jointly by a cardiologist and diving medicine specialist [14].

Pulmonary

Asthma — Asthma is likely the most common pulmonary condition that physicians are asked to evaluate in patients seeking to participate in SCUBA diving. While asthma is no longer considered an absolute contraindication in some divers, patients may experience complications, including [15]:

●Limited ventilatory capacity during exercise

●Pulmonary barotrauma

●Acute asthma exacerbation provoked by exercise or breathing cold, dry, compressed air

Recommendations vary among organizations, but all agree that prospective divers should meet the following criteria in order to dive [1,16,17]:

●Asthma must be well controlled and patient asymptomatic (may be on maintenance medications)

●No rescue medication required within 48 hours of diving

●Normal spirometry testing (FEV1>80%; FEV1/FVC >75%)

●Normal exercise tolerance

The use of bronchial provocation testing to help determine fitness for diving is controversial. Some argue that such testing is too sensitive and unnecessary for patients whose symptoms have been well controlled for a long period.

Guidance about patients with exercise-, emotion-, or cold-induced asthma vary, but many organizations recommend that these individuals not dive [16,17]. Such cases should be evaluated on an individual basis. We suggest provocation testing for these individuals, who can be referred to a pulmonologist for such evaluation.

Pneumothorax — History of a spontaneous pneumothorax is generally considered an absolute contraindication to diving due to the risk of recurrence precipitated by pressure changes while diving. A history of traumatic pneumothorax may not be a contraindication, but patients require testing to confirm normal lung function and structure [1].

Chronic obstructive pulmonary disease — Chronic obstructive pulmonary disease (COPD) with reduced pulmonary function is generally considered a contraindication to diving. COPD increases the risk for air trapping and barotrauma as well as reducing exercise tolerance [1].

Pulmonary blebs/cysts — The presence of pulmonary blebs or cysts is generally considered a contraindication to diving due to increased risk for air trapping and barotrauma [1]. However, the presence of cysts in the absence of other lung disease may be more common than previously thought, and the true risk to divers has yet to be determined [18]. Such patients wishing to dive should be referred to a diving medicine specialist.

Neurologic

Seizures — A history of seizures is considered a high-risk medical condition for SCUBA diving, as a seizure that occurs in the water can cause drowning or aspiration. Some experts feel that patients who have not experienced a seizure for five years or longer while off of all anti-seizure medication may be permitted to dive [19]. A history of a single, uncomplicated childhood febrile seizure is not considered a contraindication to diving. With the exception of individuals with a single, uncomplicated childhood seizure, we believe that any diving candidate with a history of seizures should be evaluated by or in consultation with a diving medicine specialist.

Spinal procedures — There are no well-established guidelines about returning to dive after spinal surgery. At minimum, we recommend waiting at least three to six months after surgery and obtaining clearance from the surgeon. Prior to diving, the patient should undergo evaluation of any risk factors for spinal cord decompression (eg, hemorrhage or thrombosis around the spine) and a functional evaluation of strength and mobility.

Migraine with aura — Diving candidates with a history of migraine with aura may be at increased risk for DCS due to the association of migraine with aura with PFO [19]. (See 'Cardiac septal defects' above.)

Other neurologic disorders — Patients with neurologic disorders that potentially impair function must be evaluated on a case-by-case basis to determine their fitness to dive. DCS and arterial gas embolism frequently present with neurologic symptoms that may be difficult to differentiate from a baseline neurologic condition. It is essential to perform a thorough neurologic examination and establish a functional baseline for such divers. Assessments of coordination, balance, and gait are essential in addition to strength and sensation.

Head, eyes, ears, nose, and throat — The most common injury sustained from SCUBA diving is middle ear barotrauma, which can occur due to the changes in pressure that develop during descent and ascent. Equilibration of the pressures in air-filled spaces must occur to avoid such barotrauma. Procedures to accomplish this in the middle ear must be performed actively by the diver during descent (eg, Valsalva) but occur passively during ascent unless there is an obstruction (eg, mass, edema, hemorrhage). Similarly, pressure in the sinuses should equilibrate passively unless there is obstruction. Other air-filled spaces, such as dental caries, poor-fitting fillings, and those created by periodontal prosthetics, are also at risk for barotrauma [20].

A simple test of equalization (eg, Valsalva) may be done as part of the initial examination but is probably insensitive for predicting who will experience barotrauma.

Any diver with a history of ear or sinus surgery should be evaluated by an otolaryngologist (ear, nose, and throat [ENT] surgeon) prior to diving, as should those with a history of tympanic membrane rupture or conditions that increase the risk for such rupture (eg, history of tympanostomy tubes, eustachian tube dysfunction). Unhealed tympanic membrane rupture or the presence of tympanostomy tubes is generally considered disqualifying. Some conditions may prevent the patient from diving only temporarily. These include sinusitis, otitis media, and some causes of obstruction (eg, cerumen impaction, polyps). After resolution and re-evaluation, the candidate may be considered fit for diving.

Any condition that causes vertigo (eg, Meniere disease, labyrinthitis, other causes of vestibular dysfunction) is potentially disqualifying and should be carefully evaluated. Vertigo that occurs underwater may be debilitating and cause disorientation, vomiting and aspiration, or drowning [20]. (See "Causes of vertigo" and "Evaluation of the patient with vertigo" and "Meniere disease: Evaluation, diagnosis, and management" and "Vestibular neuritis and labyrinthitis".)

Diabetes — Diabetes mellitus was previously considered a contraindication to diving due primarily to the risk of hypoglycemia and incapacitation. However, many divers with diabetes participate safely, and in 2005, UHMS and DAN published a set of consensus guidelines for diver selection, glucose management, and safe diving practices [21]. Diabetics who are controlled only on oral agents that do not cause hypoglycemia are likely to be at less risk than those on insulin or oral agents that may cause hypoglycemia.

It should also be noted that specific devices such as insulin pumps and continuous glucose monitors that are commonly worn by diabetic patients are unlikely to be tested or rated for immersion or depth. They may need to be removed or disconnected during the dive.

Hematologic abnormalities — Any condition that puts a diver at increased risk of clotting or bleeding may theoretically increase the risk of DCS and traumatic injury. These include but are not limited to sickle cell disease, hemophilia, and hereditary hypercoagulable conditions.

Psychiatric disorders — In general, any severe or uncontrolled psychiatric disorder, including substance abuse, is considered a contraindication to diving. Diving with well-controlled psychiatric disorders may be possible, but special consideration should be paid to any candidate with a history of panic, anxiety, or claustrophobia. Panic underwater may lead to poor decision-making or rapid ascent, which can result in severe injury or death. The potential effects of psychiatric medications should be accounted for when considering diver safety. (See "Panic disorder in adults: Epidemiology, clinical manifestations, and diagnosis" and 'Medications' below.)

Pregnancy — Pregnancy is generally considered a contraindication to diving. The fetus is not protected from DCS and is at greater risk of malformation and arterial gas embolism due to the lack of an effective pulmonary capillary filter [22,23]. In addition, changes in blood flow during pregnancy and abnormal temperature regulation in the mother can increase the risk of DCS, while congested mucous membranes can lead to sinus and ear barotrauma. However, termination of pregnancy is not recommended in women who have dived early in pregnancy, and normal infants have been born to women who continued diving throughout gestation.

Coronavirus disease 2019 — Any diver with a history of coronavirus disease 2019 (COVID-19) should be evaluated by a physician before beginning (or returning to) diving. The effects of COVID-19 on the pulmonary and cardiovascular systems may put divers at increased risk for pulmonary barotrauma, decreased exercise capacity, shunting, or cardiovascular events. We recommend following the screening and evaluation protocols published in the following reference [24].

History of diving-related illness — Any candidate with prior episodes of DCS or arterial gas embolism should be evaluated by or in consultation with a diving physician before returning to dive. Generally, any diver with residual symptoms from these events should not return to diving. A workup for any modifiable risk factors may be indicated as well as potential modifications for more conservative diving.

Medications — A comprehensive review of medications that may affect diving safety is beyond the scope of this topic. While few medications constitute an absolute contraindication to SCUBA diving, the medication types listed below pose potential threats to diver safety and warrant careful consideration:

●Medications that are sedating or may impair judgment or increase the risk for nitrogen narcosis. Such medications include sleep aids, benzodiazepines, opioids, and some other psychiatric medications.

●Medications that increase the risk of seizure or impaired consciousness. These include bupropion, QTc-prolonging medications (table 3), and any medications that may cause hypoglycemia (table 4), syncope, or orthostasis (eg, beta blockers, diuretics).

●Medications that impair exercise tolerance (eg, beta blockers). Exercise tolerance should be assessed in patients taking such medicines.

●Medications with increased risk for cardiac or pulmonary toxicity (eg, amiodarone, bleomycin, doxorubicin).

●Anticoagulants pose an increased risk to divers who sustain trauma or develop spinal cord DCS. The 2020 SPUMS guidelines recommend against diving while taking anticoagulants but acknowledge that this approach is controversial and based on expert opinion rather than high-quality evidence [7].

RESOURCES — The links below include useful resources for clinicians evaluating recreational SCUBA divers and can help clinicians find diving medicine specialists:

●Recreational Diving Medical Screening System

●List of diving medical examiners

●Resources for divers

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Travel medicine".)

SUMMARY AND RECOMMENDATIONS

●Physiologic demands of diving and medical evaluation – The physiologic effects of underwater immersion, pressure changes, and breathing compressed gas make SCUBA diving unsuitable for individuals with certain medical conditions (table 1). All diving certifications and many trip operators require a preparticipation medical screening. The most commonly used is the Recreational Diving Medical Screening System. (See 'Basic physiology of SCUBA diving' above and 'Medical evaluation prior to diving' above.)

●Fitness to dive – The degree of exertion required to participate in SCUBA diving varies depending on the type of diving and location. At a minimum, a diver should be a proficient swimmer able to maintain an exertion level of six metabolic equivalents of task (METs), equivalent of jogging 14 minutes/mile (9 minutes/km), but exertion exceeding this level may be required. (See 'Fitness to dive' above.)

●General contraindications to diving – As a general rule, any medical condition that impairs a patient's ability to exert themselves underwater safely (eg, debilitating coronary artery or pulmonary disease) or entails a risk of incapacitation or loss of consciousness (eg, seizure disorder) is considered an absolute contraindication to diving (table 1). Other absolute contraindications include a history of spontaneous pneumothorax and pregnancy. Additional contraindications are reviewed by organ system in the text. Exceptions to many contraindications occur but should be reviewed carefully on an individual basis. (See 'Absolute and relative contraindications' above and 'Pregnancy' above.)

●Cardiovascular disease – Cardiovascular disease represents a great risk to divers. According to major diving organizations, the following cardiovascular conditions are contraindications to diving:

•Untreated or debilitating coronary artery disease (algorithm 2)

•Cardiomyopathy

•Long QT syndrome or other channelopathy

•Arrhythmias causing episodes of loss of consciousness or exercise intolerance

•Severe valvular lesions

•Complex congenital heart disease (eg, cyanotic heart disease, unrepaired atrial septal defect)

•Cardiac septal defects (eg, patent foramen ovale [PFO])

•Automatic implantable cardioverter defibrillator (AICD)

•Immersion pulmonary edema

Well-controlled hypertension is not an absolute contraindication to diving but should be evaluated carefully. (See 'Cardiovascular' above.)

●Pulmonary disease – Well-controlled asthma is not a contraindication to diving but should be assessed carefully as it may limit exercise capacity, increase the risk of barotrauma, and be exacerbated by breathing cold, dry, compressed air. Participating asthmatic patients must have good lung function and be asymptomatic with no rescue medications needed within 48 hours of diving. A history of spontaneous pneumothorax, chronic obstructive pulmonary disease (COPD), or pulmonary blebs or cysts is considered a contraindication to diving. (See 'Pulmonary' above.)

●Neurologic disease – A history of seizure other than isolated childhood febrile seizure is widely considered a contraindication to diving. Migraine with aura is associated with PFO, and appropriate evaluation should be performed as indicated. Other neurologic conditions are discussed in the text. (See 'Neurologic' above.)

●Head, eyes, ears, nose, and throat conditions – Middle ear barotrauma is the most common injury sustained from diving. Individuals with a history of ear or sinus surgery, tympanic membrane rupture, or conditions that increase the risk of tympanic membrane rupture (eg, history of tympanostomy tubes, eustachian tube dysfunction) should be evaluated by an otolaryngologist prior to diving. Conditions such as sinusitis, otitis media, and some causes of obstruction (eg, cerumen impaction, polyps) may temporarily disqualify prospective divers. (See 'Head, eyes, ears, nose, and throat' above.)

Any condition that causes vertigo (eg, Meniere disease, labyrinthitis) is potentially disqualifying and should be carefully evaluated. Vertigo that occurs underwater may be debilitating and cause disorientation, vomiting and aspiration, or drowning.

●Diabetes – Diabetes mellitus has been considered a contraindication to diving due primarily to the risk of hypoglycemia and incapacitation, but many diabetic patients participate safely by following specific safety guidelines. (See 'Diabetes' above.)

●Other conditions and medications – Other conditions that may be contraindications to participation in diving are discussed in the text. While few medications constitute an absolute contraindication to SCUBA diving, many may pose a potential threat to diver safety and warrant careful consideration. (See 'Psychiatric disorders' above and 'Coronavirus disease 2019' above and 'History of diving-related illness' above and 'Medications' above.)