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Home , Barotrauma, Diving medicine, Fitness to dive

J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from CLINICAL REVIEW Diving : A Review of Evidence

James H. Lynch, MD, MS, and Alfred A. Bove, MD, PhD

Recreational is a growing sport worldwide, with an estimated 4 million sport divers in the United States alone. Because divers may seek medical care for a disorder acquired in a remote location, everywhere should be familiar with the , injury patterns, and treatment of injuries and illnesses unique to the . Failure to properly recognize, diagnose, and ap- propriately treat some diving injuries can have catastrophic results. In addition, recreational dive certi- fication organizations require physical examinations for medical clearance to dive. This article will re- view both common and potentially life-threatening conditions associated with diving and will review current evidence behind fitness to dive considerations for elderly divers and those with common medi- cal conditions. (J Am Board Fam Med 2009;22:399–407.)

Recreational scuba diving is a growing sport across include some controversial topics in , the globe. Worldwide, the number of annual diving which will be reviewed in this manuscript. certifications has tripled during the past 20 years.1 In the United States alone there are an estimated 4 Environment million sport divers.2 Apart from the coastlines, The most significant environmental exposure in takes place in lakes and quarries diving is the increased . Underwa- throughout the country, and divers may present to copyright. ter, pressure increases in a linear fashion with depth their local emergency departments or office prac- (Table 1).3 Exposure to increased pressure can re- tices with injuries or illnesses unique to diving and sult in several pathophysiologic changes. One is the underwater environment. Because of the pop- related to compression and expansion of gas ac- ularity of diving in tropical waters and the ease of cording to Boyle’s Law; another is related to in- travel, divers may seek medical care for a disorder creased content of dissolved inert gas in blood and acquired in a remote and often unfamiliar location. tissues according to Henry’s law.3

Failure to properly diagnose and appropriately http://www.jabfm.org/ treat some diving injuries can result in catastrophic outcomes, particularly those involving the and Sinus and spinal cord. In addition, more than ever before, Although pulmonary barotrauma receives much at- patients of all ages are seeking medical clearance to tention because of the seriousness of its sequelae, dive from their primary care physicians, who must be barotrauma to the and sinuses is a far more aware of recommendations for fitness to dive. These common and potentially debilitating injury for divers. Barotrauma is defined as the damage on 26 September 2021 by guest. Protected that results from the inability of the body to equal- This article was externally peer reviewed. ize pressure in a gas-filled space (eg, the middle Submitted 14 May 2008; revised 5 November 2008; ac- ear). During ascent and descent, the body is ex- cepted 21 November 2008. posed to changes in ambient pressure. According to From the 5th Special Group, United States Army, Fort Campbell, KY (JHL); and Section of , Tem- Boyle’s Law, as ambient pressure increases during ple University School of Medicine, Philadelphia, PA (AAB). descent, the volume of gas-filled space decreases. In Funding: none. Conflict of interest: none declared. the ear, for example, the tympanic membrane is Disclaimer: The views expressed in this manuscript are deflected inward to the point of rupture unless air is those of the authors and do not reflect the official policy or position of the Department of the Army, Department of allowed to enter the via the Eustachian Defense, or the U.S. Government. tube.4 Middle ear barotrauma (“middle ear Corresponding author: James H. Lynch, MD, MS, DeWitt ACH, Fort Belvoir, VA 22060 (E-mail: james.h.lynch@ squeeze”) is the most common diving injury, oc- us.army.mil). curring in 30% of first-time divers and 10% of doi: 10.3122/jabfm.2009.04.080099 Diving Medicine: Current Evidence 399 J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from

Table 1. Effects of Depth on Ambient Pressure tion, rhinosinusitis, or other conditions that will 8 Absolute put a patient at risk for barotrauma when diving. Sea Water Pressure Mercury Pounds per Inner ear barotrauma is a condition related to (feet) (atm) (mm) Square Inch middle ear barotrauma. Forceful attempts to equal- 0 (sea level) 1 760 14.7 ize the middle ear with the may 33 2 1520 29.4 elicit a pressure gradient between the middle ear 66 3 2280 44.1 and the perilymph of the inner ear large enough to 99 4 3040 58.8 rupture the round or oval window, causing peril- 132 5 3800 73.5 ymph leakage. This condition presents as acute sensorineural hearing loss, , and . The treatment is not recompression but experienced divers. It manifests as acute onset of rather bed rest, head elevation, avoidance of strain- and is sometimes associated with vertigo ing, and referral to an otolaryngologist. A detailed and . Clinical findings range dive history is helpful when distinguishing inner from injection of the tympanic membrane to he- ear barotrauma from inner ear sick- 4 motympanum with or without ruptured tympanic ness (DCS; discussed later). membrane.5 Sinus barotrauma (“sinus squeeze”) is another Pulmonary Barotrauma relatively common diving injury usually resulting According to Boyle’s Law, during ascent, as ambi- from transient nasal or chronic sinusitis. ent pressure is reduced, gas inside the ex- Blockage of the sinus ostium may cause a relative pands. If a diver compressed air at depth negative pressure in a sinus cavity during descent. does not allow the compressed air in the lungs to This causes engorgement with mucosal edema and escape by exhaling, or if air empties slowly from a

can result in bleeding into the sinuses. Sinus baro- copyright. segment because of obstructive pulmonary trauma manifests as acute onset of facial pain with conditions, then the gas expands during ascent as epistaxis.6 Other types of barotrauma include - ambient pressure falls, causing alveoli to rupture. odontalgia (“tooth squeeze”), inner ear barotrauma, This air under pressure then escapes the alveoli and and mask squeeze. Treatment for both sinus and rushes into surrounding tissues, resulting in medi- middle ear barotrauma includes the use of decon- astinal or or pneumotho- gestants and . Systemic antibiotics for rax. In the most severe cases, air will enter the prophylactic treatment of otitis media may be con- bloodstream via pulmonary veins, traveling through http://www.jabfm.org/ sidered in middle ear barotrauma with tympanic the left heart as an arterial gas embolism (AGE). membrane perforation. Tympanic membrane rup- These air bubbles distribute throughout the arterial ture should be allowed to completely heal before circulation and reach the brain where they occlude diving again. bloodflow, compromise the blood-brain barrier, Prevention of these common diving injuries and result in stroke-like events.9 Almost all cases of consists primarily of careful attention to pressure AGE present within 5 minutes of ascent and man- equilibration and a slow, feet-first descent. The use ifest as gross neurologic deficits, including stupor; on 26 September 2021 by guest. Protected of nasal and/or systemic , such as bilateral or unilateral motor and sensory changes; oxymetazoline and , before diving unconsciousness; visual disturbances; vertigo; con- may be helpful; however, they must be used with vulsions; and, in approximately 5%, complete car- caution to avoid the rebound effect sometimes as- diovascular collapse (Table 2).10 sociated with a reverse block during ascent at the Of note, the greatest change in lung volume per end of the dive.7 Prevention of otic barotrauma is change in depth occurs nearest the surface. There- best accomplished through the use of a Valsalva fore, it is possible for divers breathing compressed maneuver during descent. Explanation of this ma- air in a pool as shallow as 4 feet to develop pulmo- neuver should be part of the diving evaluation. nary barotrauma if they ascend to the surface while When performing fitness to dive evaluations, the holding their breath at maximum lung volume.11 primary care must consider the risk of Treatment of AGE consists of advanced cardiac life ostial insufficiency from upper respiratory infec- support, 100% , hydration, and immediate

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Table 2. Presenting in Patients musculoskeletal symptoms, such as pain that is of- with Arterial Gas Embolism ten dull or throbbing and poorly localized around a

Sign or Symptom Percentage joint—the shoulder and elbow being the most com- mon sites. rash and pruritis are common cu- Stupor or confusion 24 taneous manifestations; less common is cutis mar- Coma without 22 morata or skin marbling. This condition, which has Coma with seizures 18 been reportedly associated with PFO, may be a Unilateral motor deficits 14 harbinger of more serious symptoms that could Visual disturbances 9 require recompression therapy.14 Type I DCS usually Vertigo 8 presents soon after the dive; 95% of people affected Unilateral sensory deficits 8 Bilateral motor deficits 8 have onset of pain within 6 hours of surfacing. Joint Collapse 4 pain is rapidly relieved with recompression therapy. Cutaneous manifestations usually resolve spontane- Reproduced with permission from Neurologic Complications of ously in 12 to 24 hours. The treatment for type I, or Scuba Diving from the June 1, 2001 issue of American Family Physician. Copyright © 2001 American Academy of Family Phy- musculoskeletal, DCS is recompression using US 15 sicians. All Rights Reserved. Navy Diving Manual Table 6 algorithm. Type II (neurologic or systemic) DCS describes that which affects the neurologic, vestibular, or recompression using the US Navy Diving Manual pulmonary systems. Neurologic involvement is Table 6 algorithm, which is a standard protocol most common among sport divers and can be that involves recompression to 60 feet in a hyper- caused by either spinal cord or cerebral involve- 10 baric chamber while breathing oxygen. The ma- ment. Like pain-only DCS it is rapid in onset, with jority of individuals with AGE fully recover with half of patients developing symptoms within 1 hour 9 prompt recompression therapy. of surfacing and 90% reporting symptoms within 6 hours. The neurologic symptoms that present most copyright. often include numbness, dizziness, weakness, gait DCS is caused by injury due to formation in abnormality, and hypoesthesia (Table 3).10 blood and tissues. As ambient pressure increases at Inner ear DCS (the “staggers”) may be caused by depth, the partial of inspired gases in- bubble formation in the semicircular canals and crease proportionately. Inert gas—primarily nitro- presents as acute vertigo, nystagmus, tinnitus, and gen—is dissolved in tissues, creating in the body a nausea with vomiting. Pulmonary DCS (the supersaturated state; if ascent is too rapid, the dis- “chokes”) is a rare condition probably caused by a http://www.jabfm.org/ solved in the blood and tissues will be- come supersaturated and form bubbles that cause Table 3. Presenting Signs and Symptoms in Patients tissue injury through mechanical effects, vascular with Decompression Sickness occlusion, and activation of the clotting cascade and Sign or Symptom Percentage inflammatory mediators. Bubbles are often de- tected initially in the venous system and pose a Numbness 59 further risk for systemic injury by entering the Pain 55 on 26 September 2021 by guest. Protected arterial circulation through a patent foramen ovale Dizziness 27 (PFO), which produces a right-to-left cardiac Extreme 25 24 shunt. Bubbles entering the arterial circulation via Weakness 23 a shunt produce symptoms similar to AGE.12 The Nausea 14 incidence of DCS among recreational scuba divers is Gait abnormality 12 13 approximately 2 to 3 cases per 10,000 dives. As Hypoesthesia 10 could be predicted by the pathophysiology, DCS may Visual Disturbance 8 manifest with a wide array of signs and symptoms and Itching 5 is typically classified into either type I or type II. Type I (nonsystemic or musculoskeletal) DCS is Reproduced with permission from Neurologic Complications of Scuba Diving from the June 1, 2001 issue of American Family characterized by the absence of neurologic and Physician. Copyright © 2001 American Academy of Family Phy- other systemic symptoms and usually manifests as sicians. All Rights Reserved. doi: 10.3122/jabfm.2009.04.080099 Diving Medicine: Current Evidence 401 J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from

Table 4. Summary of Diving-Related Conditions4,6,7,10,15,16

Condition Presentation Dive History Prevention/Treatment

Barotrauma Middle ear Acute ear pain, vertigo, tympanic Usually during descent Slow equalization on descent, membrane rupture decongestants, consider antibiotics for tympanic membrane perforation Inner ear Acute vertigo, nausea, vomiting, Usually during descent Bed rest, elevated head, hearing loss avoidance of Valsalva, otolaryngology consult Sinus Acute facial pain, epistaxis Usually during descent Slow equalization on descent, decongestants Arterial gas Stupor, coma, focal weakness, Immediately upon surfacing or 100% oxygen, supportive embolism visual disturbances during ascent care, US Navy Table 6 Algorithm Decompression Sickness Type I Poorly localized joint pain, rash, Significant time at depth; 50% 100% oxygen, supportive itching develop symptoms within 1 care, US Navy Table 6 hour of surfacing, 90% Algorithm within 6 hours Type II Numbness, dizziness, weakness, Significant time at depth; 50% 100% oxygen, supportive gait abnormality, hypoesthesia develop symptoms within 1 care, US Navy Table 6 hour of surfacing, 90% Algorithm within 6 hours

massive pulmonary gas embolism. This usually fol- Flying After Diving lows a rapid or uncontrolled ascent and presents Flying after diving deserves mention because many copyright. with immediate substernal pain, cough, and cardio- recreational dives take place away from home, vascular shock resembling adult respiratory distress which may involve air travel. ’s Alert syndrome.16 The treatment for type II DCS is Network (DAN) 2002 Consensus Guidelines for hydration, 100% oxygen, and immediate transport Flying After Recreational Diving (which apply to to a recompression facility for treatment under Ta- air dives followed by flights at cabin altitudes of ble 6 algorithm of the US Navy Diving Manual. If 2000 to 8000 feet for divers without DCS symp-

the patient must be flown to a chamber, it is im- toms) are summarized here: for a single no-decom- http://www.jabfm.org/ portant to limit altitude to less than 1000 feet or use pression dive, one should wait at least 12 hours an aircraft that can be pressurized to sea level to before flying; for multiple dives per day or multiple prevent the exacerbation of symptoms. days of diving, 18 hours is suggested, and for any decompression dives, “substantially longer than 18 hours appears prudent.”18 Decompression Illness (DCI), a term that encom- on 26 September 2021 by guest. Protected passes DCS and AGE, was introduced because Common Medical Disorders and Diving treatment of either condition is recompression. There are several medical issues that may be con- However, distinction between the 2 is important traindications to diving. The conditions covered for prognosis in future diving exposures. For clin- here are some of the more controversial topics or ical management, the greatest challenge may be to ones that generate the most questions from primary distinguish between DCI and nondiving conditions care physicians. These include coronary dis- because of the vague nature of symptoms and be- ease, PFO, , , spontaneous pneumo- cause there are no specific diagnostic tests for DCI. thorax, and older age. Detailed fitness to dive con- However, diagnostic certainty is not required be- siderations and a more comprehensive list of cause divers with suspected DCI should be recom- conditions can be found in Guidelines for Recre- pressed if there are no medical contraindications ational Scuba Diver’s Physical Examination19 or and a chamber is available (Table 4).17 the webpage20 and in stan-

402 JABFM July–August 2009 Vol. 22 No. 4 http://www.jabfm.org J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from dard texts.21,22 Alternatively, DAN is available for months of healing and stabilization if a thorough phone consultation during business hours at (800) cardiovascular evaluation including stress testing 446-2671 or for emergency calls 24 hours a day, 7 determines that age-adjusted cardiopulmonary fit- days a week at (919) 684-8111.20 ness is not impaired.27

Coronary Disease Patent Foramen Ovale According to 2005 American Heart Association sta- The foramen ovale is open during fetal life to allow tistics, an estimated 16 million Americans have cor- for right to left shunting. For most people this onary heart disease—the single leading cause of opening is closed at birth by a flap that seals against death in the United States. This year an estimated the atrial septum. However, the flap is not sealed in 1.2 million Americans will suffer an acute coronary approximately one third of the population and can syndrome, and approximately 310,000 of them will open with changes in intrathoracic pressure.28 For die from the heart attack in an emergency depart- years, there has been considerable controversy over ment or without being hospitalized.23 DAN fatality the relationship between PFO and DCS. Ultra- surveillance data reveals that cardiac conditions are sound examination of divers has demonstrated that the number 2 cause of death, second only to drown- venous gas bubbles, which are common after diving ing, in the 89 US and Canadian recreational diving- and usually filtered by the pulmonary vasculature, related deaths in 2005. Approximately 80% of fa- can pass through a PFO and embolize the arterial talities were in people 40 years or older, and for circulation.29 Shunting through a PFO may not be those whose medical history was available, hyper- apparent at rest because left atrial pressure is usu- tension and heart disease were the most common ally greater than right atrial pressure almost en- conditions reported.13 tirely throughout the cardiac cycle. The exception Any physician caring for prospective divers must to this may be during times of certain respiratory consider their patients’ cardiac risk factors in light movements, such as the period after a Valsalva copyright. of the unique stresses diving puts on the heart. maneuver when a surge of venous blood transiently Aside from increased myocardial oxygen demands increases right atrial pressure. Actions such as from swimming, preload is also increased because straining to lift heavy objects (ie, scuba tanks after a of immersion-induced increase in central venous dive) produce a similar effect on venous return. return, whereas afterload is increased from cold- Regardless of the improbability of paradoxical induced peripheral vasoconstriction. The Recre- gas embolism, there have been several reports of ational Scuba Training Council, Undersea and Hy- possible associations between PFO and DCS. Cau- http://www.jabfm.org/ perbaric Medical Society (UHMS), and DAN sality is still unproven, but there seems to be an recommend that divers over the age of 40 undergo increased relative risk of developing DCS with a for coronary artery disease. Exer- PFO versus without. The exact prevalence of PFO cise stress testing may be recommended for asymp- in divers with DCS is not known because of a tomatic divers with multiple cardiac risk factors.24 combination of factors. Interpreting available data Routine screening would not be advised for young, is complicated by imprecise diagnosis of DCS and low-risk divers because of the low positive predic- poorly standardized methods of detecting PFO.30 on 26 September 2021 by guest. Protected tive value of exercise stress testing in these individ- The most widely quoted odds radio (OR) for seri- uals.25 is optimal when a diver can ous DCS with PFO versus without PFO is 2.52 reach a maximum capacity of 13 metabolic equiv- (95%CI, 1.5–4.25) as determined by a meta-anal- alents (METS) or stage 4 of the Bruce protocol. ysis published in 1998.31 This was with a reported This peak capacity allows a diver to exercise com- per-dive incidence of DCS of 3.41 in 10,000 dives. fortably at 8 to 9 METS.26 With increasing num- In 2003, an extensive bibliographic review of 145 bers of older divers, screening for coronary disease peer-reviewed journal articles related to PFO is essential for patients seeking medical clearance found no clear agreement regarding the role of for . Individuals with known coronary PFO in DCS.32 From a combined analysis of the artery disease, including those with previous heart contrast transesophageal echocardiogram studies, attacks or revascularization procedures, may be an OR of 2.6 has been calculated for the develop- cleared for low-stress sport diving after 6 to 12 ment of DCS in divers with a PFO versus those doi: 10.3122/jabfm.2009.04.080099 Diving Medicine: Current Evidence 403 J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from without.30 Other authors have concluded that PFO risk of pulmonary barotrauma, DCS, or death increases the risk for DCS as much as 4.5 times.33 among divers with asthma.41 However, this infor- A more recent investigation into the functional and mation may be biased because it accounts only for anatomic characteristics of PFO has yielded a pos- asthmatics with mild disease who have chosen to sible higher risk subgroup. The unadjusted OR to dive against medical advice. The actual risk for all develop DCS for divers with PFO was 5.5 (95% CI asthmatics is probably higher than what is shown in 1.8–16.5). However, if stratifying by PFO charac- published studies.42 teristics, there was no statistically significant differ- With such vast differences among patients with ence in risk for DCS for divers with PFO detected respect to precipitating factors, pulmonary func- only during Valsalva than divers without PFO. tion, and degree of airway obstruction and revers- There was a significant risk of divers with PFO at ibility, it is difficult to consider asthma as a single rest, with an OR of 24.8 (95% CI 2.9–210.5).34 disease when assessing fitness to dive. Rather, this With this knowledge, we should consider our condition demands individualized consideration recommendations for diving and PFO based on the based on each specific diver’s history and disease absolute increased risk. DCS in recreational divers syndrome.9 There are several published guidelines is extremely rare, occurring after only 0.005% to with a variety of recommendations for diving with 0.08% of dives. Presented differently, actual data asthma. In Australia, all divers with asthma must from DANЈs Project Dive Exploration recorded 4 pass before certification, but in the cases of DCS in approximately 14,000 dives.13 Ev- United Kingdom, well-controlled asthmatics (ex- idence supports that the average recreational sport cluding cold-, exercise-, or emotion-induced asth- diver need not be screened for PFO. For those matics) may dive as long as they do not require a already diagnosed as having a PFO, this is not a bronchodilator within 48 hours.43,44 Among ex- contraindication for diving. Until we know more, a perts and other major diving organizations, the safe strategy would be to reduce the venous bubble consensus is that lung function must be normal load because it is the bubbles—not the PFO—that before an asthmatic can dive. Carefully selected copyright. are the cause of DCS. This can be accomplished by mild to moderate, well-controlled asthmatics with avoiding dives that require decompression stops, by normal screening spirometry can be considered limiting bottom time, or by the appropriate use of candidates for diving per recommendations by the oxygen-enriched breathing mixes.35 Recreational Scuba Training Council and the UHMS.45 Spirometry should be normal before and after exercise testing. used to maintain normal spirometry is not a contraindication to div- Asthma http://www.jabfm.org/ More than 22 million Americans have asthma, ing. Inhalation challenge tests, including methacho- which is roughly 7% of the total population.36 line or hypertonic saline, are not recommended.19 Several surveys have revealed the prevalence of active asthmatic disease among divers from 4% to 7%.37–40 There is obvious theoretical concern for Diabetes asthmatic divers. Pulmonary obstruction, air trap- Individuals with diabetes mellitus (DM) who are ping, and hyperinflation that accompany an acute treated with insulin or oral hypoglycemic agents on 26 September 2021 by guest. Protected asthma attack would seemingly place the asthmatic are at increased risk for hypoglycemia during or diver at increased risk for pulmonary barotrauma. after exercise. Because of the potential for under- In addition, conditions such as cold and exercise water hypoglycemic events, diabetics have histori- serve as triggers for many asthmatics. Based on this, cally been prohibited from diving.46 The Recre- asthma had been traditionally considered an abso- ational Scuba Training Council, UHMS, and DAN lute contraindication to diving.9 consider diabetes a severe risk condition in accor- Despite these facts and documented decrements dance with the Scuba Schools International guide- in pulmonary function studies after diving, the ev- lines.19 This guideline warns that a rapidly changing idence is equivocal for risk of pulmonary baro- level of consciousness associated with hypoglycemia trauma or DCS among divers with asthma. A com- can contribute to and specifies that “diving prehensive review of the literature in 2003 found is therefore generally contraindicated, unless associ- no epidemiologic evidence for an increased relative ated with a specialized program that addresses these

404 JABFM July–August 2009 Vol. 22 No. 4 http://www.jabfm.org J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from issues.”19 Because the Diabetes and Diving Commit- patients with a history of spontaneous tee (joint UHMS/American Diabetes Association) es- are recommended not to dive under any circum- tablished the first fitness to dive criteria in 1994 for stances.49 Even if a surgical procedure designed to physically fit diabetics with well-controlled disease, prevent recurrent spontaneous pneumothorax, such multiple studies have demonstrated that select diabet- as pleurodesis, has been used, recommendations re- ics can safely participate in recreational diving and main to avoid diving, although individual divers have that evidence is lacking for a widespread ban on div- returned to diving without incident after surgical ing for all diabetics.46 However, expert recommenda- blebectomy.19 tions support holding diabetic divers to a very high standard of physical fitness and experience in diabetes management, including monitoring daily glucose pat- The Elderly and Diving terns and the effects of strenuous exercise and exclud- With growing physical activity among older Amer- ing divers with any significant systemic diabetic se- icans, primary care physicians are being asked with quelae, recent history of hypoglycemia, or poorly increased frequency to evaluate their elderly pa- controlled blood glucose.24,46 A workshop jointly tients for fitness to dive. Similarly, the diving pop- sponsored by the UHMS and DAN in 2005 pub- ulation is aging along with the US population at lished guidelines for diabetes and recreational diving. large. The following evidence can support recom- These guidelines stipulate that adults with DM may mendations for older patients who wish to participate qualify as fit to dive during their physician’s annual in sport diving. There is no formal age limitation for review if they have been on a stable dose of insulin for recreational scuba diving. Recommendations for div- 1 year or oral hypoglycemic agents for 3 months; have ing in the elderly are based on the presence of acute a glycosylated hemoglobin level of Յ9%; have had no or chronic illness and especially on the physical con- significant episodes of hypo- or hyperglycemia for 1 ditioning of the individual. Physical capacity is known year; have no secondary complications of DM; and to decline with age, yet, as we know, there are many have no hypoglycemia unawareness. In addition, older individuals who have attained a higher level of copyright. these guidelines provide scope of diving limitations fitness than many of their younger counterparts. and recommendations for glucose management on However, there are some basic physiologic responses the day of diving.47 to aging that should be considered when reviewing older patients’ fitness to dive.50 Known cardiovascular changes with age include Spontaneous Pneumothorax increases in blood pressure and peripheral vascular Some individuals have weak areas (blebs) in the resistance and decreases in oxygen update, work http://www.jabfm.org/ pleural lining of the lung that can rupture without capacity, and maximal heart rate. Some of these provocation, resulting in pneumothorax. Approxi- cardiovascular parameters that have been thought mately half of those who suffer a spontaneous to change with age may actually be associated more pneumothorax are likely to have another because with fitness level.51 In addition, as stated earlier, they usually have multiple pleural blebs, which are coronary artery disease, higher rates of which are all prone to leak at one time or another.48 Because seen among the elderly, is a major contributor to there is evidence that divers who have experienced diving-related deaths in North America. There- on 26 September 2021 by guest. Protected spontaneous pneumothorax are at greater risk of fore, emphasis is placed on assessing physical ca- pneumothorax or gas embolism while diving, most pacity and screening for coronary disease during dive physicians recommend that individuals who evaluation for fitness to dive. As previously men- have experienced spontaneous pneumothorax tioned, individuals aged 40 or older should undergo should not dive.10 In diving, these blebs or bullae in risk assessment for coronary artery disease, which the lungs predispose a diver to pulmonary baro- may require formal exercise testing. A maximum trauma because they are weaker than normal lung capacity of 13 METS is the suggested criteria for tissue, empty their air slowly during exhalation, and stress testing to allow a diver to swim comfortably can build up pressure during ascent causing rup- with diving gear in a 1-knot current expending 8 to ture. Computed tomography scanning may be rec- 9 METS.19 Other physiologic changes with age ommended to detect blebs; however, even if imag- include breathing difficulties from increased dead ing shows no evidence of underlying lung disease, space, glucose intolerance, heat and cold intoler- doi: 10.3122/jabfm.2009.04.080099 Diving Medicine: Current Evidence 405 J Am Board Fam Med: first published as 10.3122/jabfm.2009.04.080099 on 8 July 2009. Downloaded from ance, decreased range of motion from changes in 9. Neuman TS. Pulmonary barotrauma. In: Bove AA, collagen structure, and alterations of neurological Davis JC, eds. Diving medicine. 4th ed. Philadelphia, function. PA: Saunders; 2004:185–94. Because many diving accidents are caused by 10. Newton HB. Neurologic complications of scuba div- ing. Am Fam Physician 2001;63:2211–8, 2225–6. inadequate training, poor physical conditioning, 11. Bove AA. Medical aspects of sport diving. Med Sci and human error, all of these factors must be con- Sports Exerc 1996;28:591–5. sidered for a given individual before recommend- 12. Vann RD. Mechanisms and risks of decompression. ing diving. Any combination of minor physical def- In: Bove AA, Davis JC, eds. Diving medicine. 4th ed. icits in an older diver may contribute to an Philadelphia, PA: Saunders; 2004:127–64. increased risk for diving injuries or mishaps. With 13. Divers Alert Network Annual Diving Report 2007. careful evaluation, it is certainly reasonable for Durham, NC: Divers Alert Network, 2007. some elderly people in good health to undertake 14. Wilmshurst PT, Pearson MJ, Walsh KP, et al. Re- safe recreational diving. It would be prudent, how- lationship between right-to-left shunts and cutane- ever, to recommend a diving program that may not ous decompression illness. Clin Sci 2001;100:539– 42. be as rigorous as programs recommended for their 50 15. Moon RE. Treatment of decompression illness. 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