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Dive Medicine

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Other Names

  • Dive Medicine
  • Scuba Diving


  • This page summarizes the pathology associated with the various types of diving

Introduction and Terminology

  • Barotrauma: trauma related to pressure during ascent or descent
    • Descent: gas volume in air-containing body cavities, such as the lungs, middle ear, paranasal sinuses, and gastrointestinal tract, is diminished

Types of Diving

  • Scuba Diving
    • Underwater diving with the use of compressed air
    • Gear: compressed air cylinder, a regulator, a buoyancy compensator; generally includes a wetsuit, fins, mask, dive watch, weights
    • Requires certification (generally through PADI or NAUI)
  • Free Diving
    • Underwater diving without supplemental oxygen
    • Dates back thousands of years to early shellfish divers
    • Additional gear may include weights, fins, suit, dive watch
    • Competitive extreme sport, with several sub-categories
    • Deepest "no limits" depth records for males (214m, 702ft), females (160m, 525ft)
  • Snorkeling
    • Usually surface or shallow water swimming with the use of a snorkel to allow continuous breathing while the face remains submerged
    • Most often used in resorts or tropical areas
  • Rebreather Diving
  • Tethered Diving
    • Surface supplied gas supplied by a hose from a source or a diving bell.
    • Most often used in commercial or military diving, often in settings with little to no visibility.

Diving Terms

  • FSW: Feet of Sea Water
  • Gear
    • Open Circuit:
    • Closed Circuit:
    • O2-CCR: closed-circuit oxygen rebreather

Affiliated Bodies

  • Divers Alert Network (DAN)
    • Divers Alert Network is a group of not-for-profit organizations dedicated to improving diving safety for all divers
    • Website: https://dan.org/
    • Emergency hotline phone number (919) 684-9111
  • Recreational Scuba Training Council, Undersea and Hyperbaric Medical Society (UHMS)
    • The UHMS is the primary source of scientific information for diving and hyperbaric medicine physiology worldwide
    • Website: https://www.uhms.org/
  • Recreational Scuba Training Council (RSCT)
    • Dedicated to creating minimum recreational diving training standards for the various scuba diving certification agencies across the world
    • Website: https://wrstc.com/


  • Barotrauma of descent
  • Barotrauma of ascent
    • Pulmonary Barotrauma: occurs when diver breathing compressed air ascends too rapidly
    • Decompression Illness (DCI): broad term encompassing all disease processes related to decompression
      • Decompression Sickness (DCS): dissolved nitrogen comes out of solution, forms bubbles in blood and tissue ("the bends")
      • Arterial Gas Embolism (AGE): severe form of DCI in which gas bubbles are introduced into the arterial circulation
    • Alternobaric vertigo
    • Facial baroparesis (Bells Palsy)
  • At depth injuries
  • Other

Risk Factors

  • Sports
    • Scuba diving


Effects of depth on ambient pressure[1]
  • General
    • Increased ambient pressure is the most significant environmental exposure
    • Pressure increases linearly with depth
    • Exposure to increased or decreased pressure can create significant pathological effects
  • Boyle's Law
    • Describes relationship between compression and expansion of gas
    • Applies to the diving body's air filled areas such as lungs, sinuses, middle ear
    • States that the volume and pressure of a gas at a given temperature are inversely related.
    • E.g.: At 2 ATA (10m/33ft) a given gas would be 1/2 it's volume, at 3 ATA (20m/66ft) it would be 1/3 it's volume and so on.
  • Henry's Law
    • Describes increased content of dissolved inert gas in blood and tissues
    • States the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid
  • Pascals Law
    • Applies to the diving body (without air filled areas such as lungs)
    • States that the pressure applied to any part of the enclosed liquid will be transmitted equally in all directions through the liquid.


  • Checklist
    • It is important to follow a pre-diving checklist
    • Inspect equipment before and after each dive
  • Safe diving practices
    • Appropriate education and training
  • Warn divers against
    • Multiple daily dives
    • Diving and flying on the same day
    • Trying to alter diving profile
  • Patients with pulmonary disease should be screened prior to diving, this includes:
    • Asthma (controlled or uncontrolled)
    • Obstructive lung disease
    • Emphysema
    • Bullae
    • Cysts or cystic lung disease
    • Fibrosis
    • Tuberculosis (active or past)
    • Sarcoidosis
    • History of spontaneous pneumothorax
  • Exercise
    • Aerobic exercise before or during decompression may decrease the post-dive gas bubble formation[2]
  • Dental
    • Persons should undergo a thorough dental examination before being exposed to pressure changes
    • Vitality testing of all teeth is required for the detection and treatment of asymptomatic pulp necrosis[3]
  • Reduced risk of Decompression Illness:
    • Avoid breath holding
    • Avoid rapid ascent
    • Do not dive with active pulmonary infections or disease
  • Preventing nitrogen narcosis
    • Avoid diving to depths >100 feet
    • Use nitrogen free gas mixture (e.g. heliox)
    • Use mixture with reduced nitrogen content (e.g. Trimix = helium-nitrogen-oxygen)
    • Frequent check on diving companions
  • Preventing carbon monoxide toxicity
    • Test the gas in scuba tanks for CO prior to each dive
    • Fill tank at a reputable dive shop that tests for CO

Flying after Diving

  • Diver’s Alert Network (DAN) 2002 Consensus Guidelines:
    • Guidelines for flying after recreational diving without known injury
    • Apply to air dives followed by flights at cabin altitudes of 2000 to 8000 feet for divers without DCS symptoms
  • Summary recommendations[4]
    • Single no-decompression dive, one should wait at least 12 hours before flying
    • Multiple dives per day or multiple days of diving, 18 hours is suggested
    • For any decompression dives, “substantially longer than 18 hours appears prudent.”

Comorbidity Considerations

Coronary Artery Disease

  • General
    • Physicians should consider patient cardiac risk factors in light of the unique stressors that diving places upon the cardiovascular system
    • There is increased myocardial oxygen demands (from swimming), preload (immersion-induced increase in central venous return), afterload (from cold-induced peripheral vasoconstriction)
  • Recommendations from UHMS, DAN
    • Divers over the age of 40 undergo risk assessment for coronary artery disease
    • Consider exercise stress test for asymptomatic divers with multiple cardiac risk factors[5]
    • Routine screening is not recommended for low risk, young divers
  • Optimal fitness to dive
    • Reach a maximum capacity of 13 metabolic equivalents (METS)
    • Reach stage 4 of the Bruce protocol
    • Allows a diver to exercise comfortably at 8 to 9 METS[6]
  • Known coronary artery disease
    • May be cleared for low-stress sport diving after 6 to 12 healing, stabilization, cardiac rehabilitation
    • Requires thorough cardiovascular evaluation, including stress testing, to assess age-adjusted cardiopulmonary fitness[7]

Patent Foramen Ovale

  • General
    • Foramen ovale allows right to left shunting during fetal development
    • In most individuals, this closes at birth, but may not seal in up to 1/3 of the population
    • There has been considerable controversy over the relationship between (patent foramen ovale) PFO and DCS
    • Ultrasound examination of divers has demonstrated that venous gas bubbles can pass through a PFO, embolize the arterial circulation[8]
    • Shunting at rest may not be apparent because left atrial pressure is usually greater than right atrial pressure
  • Evidence
    • There seems to be increased risk of DCS in divers with a PFO vs in divers without
    • Although the statistics are challenging, a 1998 meta-analyis estimated the odds ratio (OR) for serious DCS with PFO vs no PFO is 2.52 (95%CI, 1.5– 4.25)[9]
    • A 2003 review found no clear agreement regarding the role of a PFO in DCS[10]
    • A transesophageal echocardiogram study found an OR of 2.6 for developing DCS in divers with a PFO[11]
    • Others have quoted a 4.5 fold increased risk[12]
    • More cently, a study found an OR of 24.8 (95% CI 2.9 –210.5) in divers with a PFO at rest[13]
  • Recommendations
    • Recommendations based on rareity of DCS and relative risk being very low
    • The average recreational sport diver does not need screening for PFO
    • Known PFO is not an absolute contraindication for diving
    • Strategy is to reduce venous bubble load by avoiding dives that require decompression stops, limiting bottom time, appropriate use of oxygen-enriched breathing mixes[14]


  • General
    • Asthmatics are thought to be at increased risk due to pulmonary obstruction, air trapping, and hyperinflation that accompany an acute asthma attack
    • Additionally, cold and exercise serve as triggers for many asthmatics
    • Based on these assumptions, asthma has traditionally be considered an absolute contraindication
  • Evidence
    • 2003 review: no evidence for an increased risk of pulmonary barotrauma, DCS, or death among divers with asthma[15]
    • However, 2003 paper considered biased because it only includes asthmatic with mild disease who dive against medical advice
    • True risk likely higher than what is shown in available literature[16]
  • Recommendations
    • Difficult to make universal recommendations based on variability of precipitating factors, pulmonary function, reversibility of asthmatics
    • Published guidelines vary by region
    • Australia: divers with asthma must pass spirometry before certification
    • United Kingdom: well controlled asthmatics may dive as long as they do not require bronchodilator within 48 hours[17]
    • General consensus is that lung function must be normal before asthmatic can dive
    • UHMS, RSTC: mild-moderate, well controlled asthmatics with normal spirometry can be considered
    • Medications used to maintain normal spirometry are not a contraindication
    • Inhalation challenge tests are not recommended[18]

Diabetes Mellitus

  • General
    • Divers at risk of hypoglcemia, especially if on insulin or oral hypoglycemic agents
    • For this reason, individuals with diabetes have historically been prohibited from diving[19]
    • RSCT, UHMS, and DAN consider diabetes a severe risk condition[20]
  • Diabetes and Diving Committee (joint UHMS/American Diabetes Association)
    • In 1994, established first dive criteria for physically fit, well controlled diabetocs
  • Evidence
    • Multiple studies have demonstrated that select diabetics can safely participate in recreational diving (need citation)
    • Evidence is lacking for a universal ban for all diabetics
  • General recommendations
    • Potential diver must be held to high standard of fitness, very experienced in diabetes management
    • Must be skilled at monitoring daily glucose, including effects of strenuous exercise
    • Exclude divers with significant systemic sequlae, recent history of hypoglycemia, poorly controlled blood glucose
  • UHMS/ DAN Guidelines (2005)[21]
    • Must be on stable dose of insulin for 1 year or oral hypoglcemic agent for 3 months
    • Hemoglobin A1c < 9%
    • No significant hypo- or hyperglycemic episodes for 1 year
    • No secondary complications of diabetes
    • No hypoglycemic unawareness
    • Note: these guidelines also provide recommendations and limitations on the day of diving

Spontaneous Pneumothorax

  • General
    • Individuals with a history of spontaneous pneumothorax are at high risk of developing another one
    • Divers who have experienced a pneumothorax are at greater risk of developing another one or an air gas emoblism
    • Most dive physicians recommend these individuals should not dive
  • Recommendations
    • CT can evaluate for blebs, however even if no underlying disease
    • Individuals with a history of spontaneous (i.e. unprovoked) pneumothorax should not dive[22]
    • Note there are case reports of individuals returning to diving after a surgical blebectomy (need citation)

Geriatric Patients

  • General
    • Aging adults are more physicaly active
    • Physicians are more likely to be asked to evaluate geriatric patients for fitness to dive
  • General recommendations
    • There is no formal age limitation for recreational scuba diving
    • Recommendations are based on the acute and chronic illnesses, overall physical fitness of the individual
    • All geriatric patients require cardiovascular risk stratifiation; may require exercise stress testing (see coronary artery disease)
    • Consider diving program that is less rigorous[23]


  • Hypothermia
    • Increased risk of hypothermia due to increased conductive heat loss in water

See Also




  1. Lynch, James H., and Alfred A. Bove. "Diving medicine: a review of current evidence." The Journal of the American Board of Family Medicine 22.4 (2009): 399-407.
  2. Blatteau JE, Gempp E, Galland FM, Pontier JM, Sainty JM, Robinet C. Aerobic exercise 2 hours before a dive to 30 msw decreases bubble formation after decompression. Aviat Space Environ Med. 2005 Jul;76(7):666-9.
  3. K. Woodmansey, “Class II barodontalgia: review and report of a case,” General Dentistry, vol. 56, no. 7, pp. e39–e42, 2008
  4. Sheffield PJ, Vann RD, eds. DAN Flying After diving workshop proceedings. Durham, NC: Divers Alert Network; 2004.
  5. Harrison D, Lloyd-Smith R, Khazei A, Hunte G, Lepawsky M. Controversies in the medical clearance of recreational scuba divers: updates on asthma, diabetes mellitus, coronary artery disease and patent foramen ovale. Curr Sports Med Rep 2005;4:275– 81.
  6. Pendergast DR, Tedesco M, Nawrocki DM, Fisher NM. Energetics of underwater swimming with SCUBA. Med Sci Sports Exerc 1996;28:573– 80.
  7. Divers Alert Network, Caruso JL. Diving medicine articles. Cardiovascular fitness and diving. Available at: http://www.diversalertnetwork.org/medical/articles/ article.asp?articleid11. Accessed February 10, 2008.
  8. Lynch JJ, Schuchard GH, Gross CM, Wann LS. Prevalence of right-to-left shunting in a healthy population: detection by valsalva maneuver contrast echocardiography. Circulation 1984;59:379–84.
  9. Bove AA. Risk of decompression sickness with a patent foramen ovale. Undersea Hyperb Med 1998; 25:175– 8.
  10. Foster PP, Boriek AM, Butler BD, Gernhardt ML, Bove AA. Patent foramen ovale and paradoxical systemic embolism: a bibliographic review. Aviat Space Environ Med 2003;74(6 Pt 2):B1– 64.
  11. Germonpre P. Patent foramen ovale and diving. Cardiol Clin 2005;23:97–104.
  12. Schwerzmann M, Seiler C, Lipp E, et al. Relation between directly detected patent foramen ovale and ischemic brain lesions in sport divers. Ann Intern Med 2001;134:21– 4.
  13. Cartoni D, De Castro S, Valente G, et al. Identification of professional scuba divers with patent foramen ovale at risk for decompression illness. Am J Cardiol 2004;94:270 –3.
  14. Moon RE, Bove AA. Transcatheter occlusion of patent foramen ovale: A prevention for decompression illness? Undersea Hyperb Med 2004;31:271– 4.
  15. Koehle M, Lloyd-Smith R, McKenzie D, Taunton J. Asthma and recreational scuba diving: a systematic review. Sports Med 2003;33:109 –16.
  16. Divers Alert Network, de Lisle Dear G. Asthma and diving. Available at: http://www.diversalertnetwork. org/medical/articles/article.asp?articleid22. Accessed February 18, 2008.
  17. British Sub Aqua Club. Medical information. Asthma. Available at: www.bsac.com/core/core_picker/ download.asp?id10093&filetitleAsthma. Accessed on: February 18, 2008.
  18. Scuba Schools International. Guidelines for recreational scuba diver’s physical examination; 2002:1– 4. Available at: http://www.scubaland.com/Files/PDF/ Medical%20Exam%20Guidelines.pdf. Accessed October 26, 2008.
  19. Scott DH, Marks AD. Diabetes and Diving. In: Bove AA, Davis JC, eds. Diving medicine. 4th ed. Philadelphia, PA: Saunders; 2004:507–18.
  20. Scuba Schools International. Guidelines for recreational scuba diver’s physical examination; 2002:1– 4. Available at: http://www.scubaland.com/Files/PDF/ Medical%20Exam%20Guidelines.pdf.
  21. Pollock NW, Uguccioni DM, Dear GdeL, eds. Diabetes and recreational diving: guidelines for the future. Proceedings of the Undersea Hyperbaric Medical Society/Divers Alert Network workshop, June 19, 2005. Durham, NC: Divers Alert Network; 2005.
  22. Divers Alert Network, Moon RE. Scanning for blebs. Available at: http://www.diversalertnetwork. org/medical/articles/article.asp?articleid40.
  23. Mazzeo RS, Cavanagh P, Evans WJ, et al. ACSM position stand on exercise and physical activity for older adults. Med Sci Sports Exerc 1998;30:992– 1008.
Created by:
John Kiel on 13 June 2019 05:36:20
Last edited:
10 April 2023 17:18:32