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©2013 UpToDate ® Print Email Summary of key points and recommendations The diving environment Diving is an arduous underwater activity in which environmental conditions affect bodily structure and function. Forevery 10 meters descent in sea water, ambient pressure increases by 100kPa, equivalent to 1 atmosphere (1 bar). The volume of a given mass ofgas changes inversely in proportion to pressure. The gas in bodilycavities such as the lungs, sinuses, middle ear and intestine istherefore subject to compression during descent and expansion duringascent. This may lead to tissue damage. Partial pressure ofgases increases in direct proportion to the increase in ambientpressure. Greater quantities of inert gas, mainly nitrogen, thereforedissolve in tissues at depth and come out of solution on ascent. The density of inhaled gas increases with pressure, restricting breathing. Immersion displaces blood from the periphery into the thorax, reducing lung volume. Work of breathingincreases due to a combination of increased gas density, increasedhydrostatic pressure, and altered respiratory mechanics. The underwater breathing apparatus adds dead space and increases resistance to breathing. During diving, carbon dioxide retention may result from the above listed effects on the body. Potential risks of diving General risks: panic, hypothermia, physical trauma, and drowning. Equipment/techniqueproblems: hypoxia, hyperoxia, or poisoning by inappropriate gasmixtures or contaminant gases may result from equipment malfunction orpoor dive planning. Amalfunctioning respiratory regulator may result in aspiration. Barotrauma:is caused by compression or expansion of gas filled spaces duringdescent or ascent, respectively. Compression of the lungs duringdescent may lead to alveolar exudationand haemorrhage. Expansion of the lungs during ascent may cause lungrupture leading to pneumothorax, pneumomediastinum, and arterial gasembolism. Decompression illness:may occur when gas, which has dissolved in tissues while at depth,comes out of solution as bubbles. Clinical manifestations vary, themost severe being cardiorespiratory and neurological. Loss of buoyancy control: is a cause of many accidents, usually when it leads to rapid uncontrolled ascent. It is also essential to consider comorbidities such asdiabetes and epilepsy which may influence capability for diving but areoutside the scope of this document.

Decompression illness:may occur when gas, which has dissolved in tissues while at depth,comes out of solution as bubbles. Clinical manifestations vary, themost severe being cardiorespiratory and neurological. Loss of buoyancy control: is a cause of many accidents, usually when it leads to rapid uncontrolled ascent. It is also essential to consider comorbidities such asdiabetes and epilepsy which may influence capability for diving but areoutside the scope of this document. The physician should bear the following general concepts in mind when assessing respiratory fitness to dive: The subject may be required to swim in strong currents. The subject may be required to rescue a companion (dive buddy) in the event of an emergency. The diving environment is associated with a risk of lung rupture. The gas breathed by the diver may be very cold. Buoyancycontrol is essential and requires training, experience, and use ofappropriate equipment. The following recommendations are therefore made. Assessment of respiratory fitness to dive In the history,particular attention should be paid to current respiratory symptoms,previous history of lung disease including childhood history, previoustrauma to the chest, and previous episodes of pneumothorax. Respiratory system examination should be performed. Forced expiratoryvolume in 1 second (FEV1), forced vital capacity (FVC), and peakexpiratory flow rate (PEF) should be measured. FEV1 and PEF shouldnormally be greater than 80% of predicted and the FEV1/FVC ratiogreater than 70 percent. Routine chestradiography is not considered necessary in asymptomatic subjects withno significant respiratory history and normal examination findings.However, all professional divers, including recreational divers, whoplan to work as instructors are recommended by the Health and SafetyExecutive to undergo chest radiography. Chest radiographyis appropriate if there is a previous history of any significantrespiratory illness - for example, pleurisy, pneumonia, recurrentrespiratory infections, sarcoidosis, chest surgery or trauma,pneumothorax - and those with current respiratory symptoms and/orabnormal examination findings. Routine measurementof the expiratory flow-volume loop, exercise testing, or bronchialprovocation testing are not considered necessary although these testsmay be useful in specific cases.

Chest radiographyis appropriate if there is a previous history of any significantrespiratory illness - for example, pleurisy, pneumonia, recurrentrespiratory infections, sarcoidosis, chest surgery or trauma,pneumothorax - and those with current respiratory symptoms and/orabnormal examination findings. Routine measurementof the expiratory flow-volume loop, exercise testing, or bronchialprovocation testing are not considered necessary although these testsmay be useful in specific cases. Thoracic CTscanning, which has greater sensitivity than standard chest radiographyto detect lung structural abnormality, may be useful in specific areas. Reproduced from Thorax, British Thoracic Society guidelines on respiratory aspects of fitness for diving, volume 58, pages 3-13, Copyright © 2003, with permission from BMJ Publishing Group Ltd.

Chest radiographyis appropriate if there is a previous history of any significantrespiratory illness - for example, pleurisy, pneumonia, recurrentrespiratory infections, sarcoidosis, chest surgery or trauma,pneumothorax - and those with current respiratory symptoms and/orabnormal examination findings. Routine measurementof the expiratory flow-volume loop, exercise testing, or bronchialprovocation testing are not considered necessary although these testsmay be useful in specific cases. Thoracic CTscanning, which has greater sensitivity than standard chest radiographyto detect lung structural abnormality, may be useful in specific areas. Reproduced from Thorax, British Thoracic Society guidelines on respiratory aspects of fitness for diving, volume 58, pages 3-13, Copyright © 2003, with permission from BMJ Publishing Group Ltd. Summary of key points and recommendations (continued) Recommendations on specific respiratory conditions Lung bullae or cysts increase risk of barotrauma and are contraindications to diving. Previousspontaneous pneumothorax is a contraindication unless treated bybilateral surgical pleurectomy and associated with normal lung functionand thoracic CT scan performed after surgery. Subjects with asthma should be advised not to dive if they have wheeze precipitated by exercise, cold, or emotion. Subjects with asthma may be permitted to dive if, with or withoutregular inhaled anti-inflammatory agents (step 2 of the BTSguidelines), they: Are free of asthma symptoms; Have normal spirometry (FEV1>80 percent predicted and FEV1/VC ratio >70 percent predicted); and Have a negative exercise test (<15 percent fall in FEV1 after exercise). Subjects withasthma should monitor their asthma with regular twice daily peak flowmeasurement and should refrain from diving if they have: Active asthma - that is, symptoms requiring relief medication in the 48 hours preceding the dive; An increased peak flow variability (more than 20 percent diurnal variation). COPDcarries a theoretical increased risk of barotrauma and reduced exercisetolerance. Subjects will probably be advised against diving on thebasis of reduced pulmonary function (FEV1 <80 percent predicted).

Active asthma - that is, symptoms requiring relief medication in the 48 hours preceding the dive; An increased peak flow variability (more than 20 percent diurnal variation). COPDcarries a theoretical increased risk of barotrauma and reduced exercisetolerance. Subjects will probably be advised against diving on thebasis of reduced pulmonary function (FEV1 <80 percent predicted). Sarcoidosis has been associated with pulmonary barotrauma. Diving iscontraindicated in subjects who have active sarcoidosis. Those in whomsarcoidosis has resolved should have normal chest radiography andpulmonary function testing before being advised that they may proceedwith diving. Tuberculosis is apotentially transmissible disease that may cause residual impairment oflung structure and function. A subject with active tuberculosis shouldnot dive. After curative treatment they may dive if lung function andchest radiograph are normal. Cysticfibrosis is often associated with abnormal pulmonary function andincreased risk of pneumothorax. Diving is contraindicated in thosepatients who have pulmonary involvement. Fibrotic lungdisease reduces lung compliance and impairs gas transfer. Diving istherefore contraindicated in subjects who have fibrotic lung disease. Long term effects of diving on the lung Diverstend to have large lung volumes with proportionately greater increasesin vital capacity than in FEV1. This may be attributable in part to theeffects of repeatedly breathing dense gas through increased resistances. Divers may have reduced expiratory flow rates at low lung volumes, possibly reflecting small airway disease. Vital capacity of divers may decline with age at an increased rate. Saturation diving causes a fall in carbon monoxide transfer which, oncethe dive is completed, gradually returns to pre-dive values. Sources of specialist advice In the United Kingdom, advice on sports divingmay be sought from the medical referees of the British Sub Aqua Club,the Scottish Sub Aqua Club, or the Sub Aqua Association. Information isavailable on the UK Sport Diving Medical Diving Committee website(file://ww.uksdmc.co.uk). The Royal Navy Institute of Naval Medicine isalso willing to discuss cases with both divers and physicians.

In the United Kingdom, advice on sports divingmay be sought from the medical referees of the British Sub Aqua Club,the Scottish Sub Aqua Club, or the Sub Aqua Association. Information isavailable on the UK Sport Diving Medical Diving Committee website(file://ww.uksdmc.co.uk). The Royal Navy Institute of Naval Medicine isalso willing to discuss cases with both divers and physicians. The Health and Safety Executive (HSE) isresponsible for commercial diving policy and regulation. Individualswho are diving at work require a current HSE certificate of fitness todive following examination by an approved medical examiner of divers. Reproduced from Thorax, British Thoracic Society guidelines on respiratory aspects of fitness for diving, volume 58, pages 3-13, Copyright © 2003, with permission from BMJ Publishing Group Ltd.