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80-455: SDV may stand for: Swimmer delivery vehicle for scuba divers SEAL Delivery Vehicle Shut down valve Switched digital video via cable Sde Dov Airport , Tel Aviv, Israel (by IATA airport code) Society of Divine Vocations or Vocationist Fathers SDV International Logistics Source Data Verification , for clinical trials Software Defined Vehicle Topics referred to by

160-457: A shock wave . Ventilator-induced lung injury (VILI) is a condition caused by over-expansion of the lungs by mechanical ventilation used when the body is unable to breathe for itself and is associated with relatively large tidal volumes and relatively high peak pressures. Barotrauma due to overexpansion of an internal gas-filled space may also be termed volutrauma . Examples of organs or tissues easily damaged by barotrauma are: When diving,

240-431: A DPV requires simultaneous depth control, buoyancy adjustment, monitoring of breathing gas, and navigation. Buoyancy control is vital for diver safety: The DPV has the capacity to dynamically compensate for poor buoyancy control by thrust vectoring while moving, but on stopping the diver may turn out to be dangerously positively or negatively buoyant if adjustments were not made to suit the changes in depth while moving. If

320-431: A chest X-ray. Also known as mediastinal emphysema to divers, pneumomediastinum is a volume of gas inside the mediastinum, the central cavity in the chest between the lungs and surrounding the heart and central blood vessels, usually formed by gas escaping from the lungs as a result of lung rupture. Gas bubbles escaping from a ruptured lung can travel along the outside of bronchioles and blood vessels until they reach

400-652: A combat swimmer unit or naval Special Forces underwater, over long distances. SDVs carry a pilot, co-pilot/navigator, and combat swimmer team and their equipment, to and from maritime mission objectives on land or at sea. The pilot and co-pilot are often a part of the swimmer team. An example of a modern SDV in use today is the SEAL Delivery Vehicle used by the United States Navy SEALs and British Special Boat Service . For long-range missions, SDVs can carry their own onboard breathing gas supply to extend

480-473: A dive can allow water into the middle ear, which can cause severe vertigo from caloric stimulation. This may cause nausea and vomiting underwater, which has a high risk of aspiration of vomit or water, with possible fatal consequences. Inner ear barotrauma (IEBt), though much less common than MEBT, shares a similar external cause. Mechanical trauma to the inner ear can lead to varying degrees of conductive and sensorineural hearing loss as well as vertigo . It

560-460: A dive profile alone cannot always eliminate either of the possibilities, the detailed dive history may be necessary to diagnose the more likely injury. It is also possible for both to occur at the same time, and IEDCS is more likely to affect the semicircular canals, causing severe vertigo, while IEBt is more likely to affect the cochlea, causing hearing loss, but these are just statistical probabilities, and in reality it can go either way or both. It

640-408: A doubling of the pressure on the diver. This pressure change will reduce the volume of a flexible gas-filled space by half. Boyle's law describes the relationship between the volume of the gas space and the pressure in the gas. Barotraumas of descent, also known as compression barotrauma, and squeezes, are caused by preventing the free change of volume of the gas in a closed space in contact with

720-519: A fast, light, surface boat to a submerged DPV. Started in the 1970s by Submarine Products Ltd. of Hexham, Northumberland, England, Subskimmer is now a tradename owned by Marine Specialised Technology. As DPVs get bigger they gradually merge into submarines . A wet sub is a small submarine where the crew spaces are flooded at ambient pressure and the crew must wear diving gear. Covert military operations use wet subs to deliver and retrieve operators into harbors and near-shore undetected. An example

800-399: A lungful of air with them from the surface, which merely re-expands safely to near its original volume on ascent. The problem only arises if a breath of ambient pressure gas is taken at depth, which may then expand on ascent to more than the lung volume. Pulmonary barotrauma may also be caused by explosive decompression of a pressurised aircraft, as occurred on 1 February 2003 to the crew in

880-410: A pneumothorax as a result of barotrauma from ascending just 1 metre (3 ft) while breath-holding with their lungs fully inflated. An additional problem in these cases is that those with other features of decompression sickness are typically treated in a diving chamber with hyperbaric therapy ; this can lead to a small pneumothorax rapidly enlarging and causing features of tension. Diagnosis of

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960-413: A pneumothorax by physical examination alone can be difficult (particularly in smaller pneumothoraces). A chest X-ray , computed tomography (CT) scan, or ultrasound is usually used to confirm its presence. Other conditions that can result in similar symptoms include a hemothorax (buildup of blood in the pleural space), pulmonary embolism , and heart attack . A large bulla may look similar on

1040-404: A pressure differential develops between the ambient water and the interior of this space, and this can cause swelling and haemorrhagic blistering of the canal. Treatment is usually analgesics and topical steroid eardrops. Complications may include local infection. This form of barotrauma is usually easily avoided. Middle ear barotrauma (MEBT) is an injury caused by a difference in pressure between

1120-431: A pressure-resistant watertight casing containing a battery -powered electric motor , which drives a propeller . The design must ensure that the propeller cannot harm the diver, diving equipment or marine life, the vehicle cannot be accidentally started or run away from the diver, and it remains approximately neutrally buoyant while in use underwater. DPVs are useful for extending the range of an autonomous diver that

1200-449: A resultant tension in the surrounding tissues which exceeds their tensile strength . Patients undergoing hyperbaric oxygen therapy must equalize their ears to avoid barotrauma. High risk of otic barotrauma is associated with unconscious patients. Explosive decompression of a hyperbaric environment can produce severe barotrauma, followed by severe decompression bubble formation and other related injury. The Byford Dolphin incident

1280-524: A team can be re-supplied by contact with other SDVs. In the latter usage, SDVs can stealthily plant mines and other bombs on ships or port infrastructure and then retreat to a safe distance before detonating the explosives. In addition to destroying targets, the SDV can mislead enemies as to where they are being attacked from. One type of SDV—the Mark 9 SEAL Delivery Vehicle—was also capable of firing torpedoes, giving it

1360-576: A type of diver propulsion vehicle used as secret naval weapons in World War II . The name was commonly used to refer to the weapons that Italy, and later Britain, deployed in the Mediterranean and used to attack ships in enemy harbours. The first human torpedo was the Italian Maiale ("Pig"). In operation, it was carried by another vessel (usually a normal submarine), and launched near the target. It

1440-494: A type of shock called obstructive shock , which can be fatal unless reversed. Very rarely, both lungs may be affected by a pneumothorax. It is often called a "collapsed lung", although that term may also refer to atelectasis . Divers who breathe from an underwater apparatus are supplied with breathing gas at ambient pressure , which results in their lungs containing gas at higher than atmospheric pressure. Divers breathing compressed air (such as when scuba diving ) may develop

1520-402: A variety of techniques depending on the affected area and whether the pressure inequality is a squeeze or an expansion: Professional divers are screened for risk factors during initial and periodical medical examination for fitness to dive . In most cases recreational divers are not medically screened, but are required to provide a medical statement before acceptance for training in which

1600-478: Is accepted practice to assume that if any symptom typical of DCS is present, that the diver has DCS and will be treated accordingly with recompression. Limited case data suggest that recompression does not usually cause harm if the differential diagnosis between IEBt vs IEDCS is doubtful. The sinuses , like other air-filled cavities, are susceptible to barotrauma if their openings become obstructed. This can result in pain as well as epistaxis ( nosebleed ). Diagnosis

1680-465: Is affected by the interaction of these forces and the pre-existing state of the lung tissues, and dynamic changes in alveolar structure may be involved. Factors such as plateau pressure and positive end-expiratory pressure (PEEP) alone do not adequately predict injury. Cyclic deformation of lung tissue may play a large part in the cause of VILI, and contributory factors probably include tidal volume, positive end-expiratory pressure and respiratory rate. There

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1760-509: Is also common for conditions affecting the inner ear to result in auditory hypersensitivity. Two possible mechanisms are associated with forced Valsalva manoeuvre. In the one, the Eustachian tube opens in response to the pressure, and a sudden rush of high pressure air into the middle ear causes stapes footplate dislocation and inward rupture of the oval or round window. In the other, the tube remains closed and increased cerebrospinal fluid pressure

1840-467: Is an example. Rapid uncontrolled decompression from caissons, airlocks, pressurised aircraft, spacecraft, and pressure suits can have similar effects of decompression barotrauma. Collapse of a pressure resistant structure such as a submarine , submersible , or atmospheric diving suit can cause rapid compression barotrauma. A rapid change of altitude can cause barotrauma when internal air spaces cannot be equalised. Excessively strenuous efforts to equalise

1920-510: Is different from Wikidata All article disambiguation pages All disambiguation pages Swimmer delivery vehicle DPVs include a range of configurations from small, easily portable scooter units with a small range and low speed, to faired or enclosed units capable of carrying several divers longer distances at higher speeds. The earliest recorded DPVs were used for military purposes during World War II and were based on torpedo technology and components. A DPV usually consists of

2000-413: Is indirectly caused by ambient pressure reduction, and tissue damage is caused directly and indirectly by gas bubbles. However, these bubbles form out of supersaturated solution from dissolved gases, and are not generally considered barotrauma. Decompression illness is a term that includes decompression sickness and arterial gas embolism caused by lung overexpansion barotrauma. It is also classified under

2080-864: Is largely controlled by the towing vessel, but the diver has a limited amount of control over vertical and lateral excursions. DPVs currently in service include: Swedish firm Defence Consulting Europe Aktiebolag (stock company, often abbreviated as DCE AB) has developed a family of SDV of modular design, all of them based on the same basic frame and general design principle, and current available versions include: After purchasing US submersible manufacturer Seahorse Marine, Emirate Marine Technologies of United Arab Emirates has developed four classes DPV/SDV, all of them built of glass reinforced plastic and carbon composite materials: All SDVs of former Yugoslavia were developed by Brodosplit - Brodogradilište Specijalnih Objekata d.o.o. which have been passed on to successor nations of former Yugoslavia. Barotrauma Barotrauma

2160-409: Is most commonly associated with acute respiratory distress syndrome . It used to be the most common complication of mechanical ventilation but can usually be avoided by limiting tidal volume and plateau pressure to less than 30 to 50 cm water column (30 to 50 mb). As an indicator of transalveolar pressure, which predicts alveolar distention, plateau pressure or peak airway pressure (PAP) may be

2240-487: Is no improvement in symptoms after 48 hours, exploratory tympanotomy may be considered to investigate possible repair of a labyrinthine window fistula . Recompression therapy is contraindicated in these cases, but is the definitive treatment for inner ear decompression sickness, making an early and accurate differential diagnosis important for deciding on appropriate treatment. IEBt in divers may be difficult to distinguish from inner ear decompression sickness (IEDCS), and as

2320-460: Is no protocol guaranteed to avoid all risk in all applications. Barotrauma caused during airplane journeys is also referred to as airplane ear. The environmental pressure must be prevented from changing rapidly by large amounts. One should include multiple redundant levels of protection against rapid decompression, and systems allowing non-catastrophic failure with sufficient time to allow comfortable equalization of relevant air spaces, particularly

2400-436: Is otherwise restricted by the amount of breathing gas that can be carried, the rate at which that breathing gas is consumed, which is increased by exertion and diver fatigue, and the time limits imposed by decompression obligation, which depend on the dive profile . Typical uses include cave diving and technical diving where the vehicles help move bulky equipment and make better use of the limited underwater time imposed by

2480-437: Is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or liquid. The initial damage is usually due to over-stretching the tissues in tension or shear , either directly by an expansion of the gas in the closed space or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by

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2560-561: Is the Multi-Role Combatant Craft (MRCC). These are unpowered boards (usually rectangular) towed by a surface boat which function as diving planes . The diver holds onto the sled and may use a quick-release tether to reduce fatigue. Depth control while submerged is by adjusting the angle of attack. Sometimes known as manta-boards, after the manta ray . Towed sleds are useful for surveys and searches in good visibility in waters where there are not too many large obstacles. The route

2640-457: Is the usual protective measure and is the definitive protection in decompression and exposure to vacuum, but they are expensive, heavy, bulky, restrict mobility, cause thermal regulatory problems, and reduce comfort. To prevent injury from unavoidable pressure changes, similar equalization techniques and relatively slow pressure changes are required, which in turn require patent Eustachian tubes and sinuses. Treatment of diving barotrauma depends on

2720-584: Is transmitted through the cochlea and causes outward rupture of the round window. Inner ear barotrauma can be difficult to distinguish from Inner ear decompression sickness . Both conditions manifest as cochleovestibular symptoms. The similarity of symptoms makes differential diagnosis difficult, which can delay appropriate treatment or lead to inappropriate treatment. Nitrogen narcosis , oxygen toxicity , hypercarbia , and hypoxia can cause disturbances in balance or vertigo, but these appear to be central nervous system effects, not directly related to effects on

2800-420: Is usually caused by breath-holding on ascent. The compressed gas in the lungs expands as the ambient pressure decreases causing the lungs to over-expand and rupture unless the diver allows the gas to escape by maintaining an open airway , as in normal breathing. The lungs do not sense pain when over-expanded giving the diver little warning to prevent the injury. This does not affect breath-hold divers as they bring

2880-424: Is usually simple provided the history of pressure exposure is mentioned. Barosinusitis, is also called aerosinusitis, sinus squeeze or sinus barotrauma. Sinus barotrauma can be caused by external or internal overpressure. External over-pressure is called sinus squeeze by divers, while internal over-pressure is usually referred to as reverse block or reverse squeeze. If a diver's mask is not equalized during descent

2960-610: The British when they discovered how effective this weapon could be after three Italian units successfully penetrated the harbour of Alexandria and damaged the British battleships HMS  Queen Elizabeth and HMS  Valiant , and the tanker "Sagona." The official Italian name for their craft was "Siluro a Lenta Corsa" (SLC or "Slow-running torpedo"), but the Italian operators nicknamed it "Maiale" after their inventor Teseo Tesei said that it

3040-629: The Space Shuttle Columbia disaster . Barotrauma may be caused when diving, either from being crushed, or squeezed, on descent or by stretching and bursting on ascent; both can be avoided by equalising the pressures. A negative, unbalanced pressure is known as a squeeze, crushing eardrums, dry suit, lungs or mask inwards and can be equalised by putting air into the squeezed space. A positive unbalanced pressure expands internal spaces rupturing tissue and can be equalised by letting air out, for example by exhaling. Both may cause barotrauma. There are

3120-408: The external auditory canal . Diagnosis of middle and external ear barotrauma is relatively simple, as the damage is usually visible if severe enough to require intervention. Barotrauma can occur in the external auditory canal if it is blocked by cerumen, exostoses, a tight-fitting diving suit hood or earplugs, which create an airtight, air-filled space between the eardrum and the blockage. On descent,

3200-453: The pleural space between the lung and the chest wall . Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath . In a minority of cases, a one-way valve is formed by an area of damaged tissue , and the amount of air in the space between chest wall and lungs increases; this is called a tension pneumothorax. This can cause a steadily worsening oxygen shortage and low blood pressure . This leads to

3280-455: The pressure differences which cause the barotrauma are changes in hydrostatic pressure. There are two components to the surrounding pressure acting on the diver: the atmospheric pressure and the water pressure. A descent of 10 metres (33 feet) in water increases the ambient pressure by an amount approximately equal to the pressure of the atmosphere at sea level. So, a descent from the surface to 10 metres (33 feet) underwater results in

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3360-557: The severity may be taken into consideration . Asthmatics with a mild and well controlled condition may be permitted to dive under restricted circumstances. A significant part of entry level diver training is focused on understanding the risks and procedural avoidance of barotrauma. Professional divers and recreational divers with rescue training are trained in the basic skills of recognizing and first aid management of diving barotrauma. Isolated mechanical forces may not adequately explain ventilator induced lung injury (VILI). The damage

3440-454: The DPV is bulky and affects precise manoeuvring at close quarters. The DPV occupies at least one hand while in use and may get in the way while performing precision work like macro photography. Since the diver is not kicking for propulsion, they will generally get colder due to lower physical activity and increased water flow. This can be compensated by appropriate thermal insulation. If the operation of

3520-418: The DPV is critical to exit from a long penetration dive, it is necessary to allow for alternative propulsion in case of a breakdown to ensure safe exit before the breathing gas runs out. Control of the DPV is additional task loading and can distract the diver from other matters. A DPV can increase the risk of a silt-out if the thrust is allowed to wash over the bottom. Human torpedoes or manned torpedoes are

3600-576: The Mediterranean alone. Similar vehicles have been made for work divers or sport divers but better streamlined as these do not have warheads; the Dolphin made on the Isle of Wight (UK) in the 1971s is an example. Some Farallon and Aquazepp scooters are torpedo-shaped with handles near the bow and a raised seat at the rear to support the diver's crotch against the slipstream. The Russian Protei-5 and Proton carry

3680-493: The air supply is insufficient to keep up with the increase in ambient pressure. On a helmet with a neck dam, the neck dam will allow water to flood the helmet before serious barotrauma can occur. This can happen with helium reclaim helmets if the reclaim regulator system fails, so there is a manual bypass valve, which allows the helmet to be purged so breathing can continue on open circuit. Lung over-pressure injury in ambient pressure divers using underwater breathing apparatus

3760-763: The body over time, and when the symptoms are mild, no treatment may be necessary. Otherwise it may be vented through a hypodermic needle inserted into the mediastinum. Recompression is not usually indicated. Diagnosis of barotrauma generally involves a history of exposure to a source of pressure which could cause the injury suggested by the symptoms. This can vary from the immediately obvious if exposed to explosive blast, or mask squeeze, to rather complex discrimination between possibilities of inner ear decompression sickness and inner ear barotrauma, which may have nearly identical symptoms but different causative mechanism and mutually incompatible treatments. The detailed dive history may be necessary in these cases. In terms of barotrauma

3840-449: The broader term of dysbarism , which covers all medical conditions resulting from changes in ambient pressure. Barotrauma typically occurs when the organism is exposed to a significant change in ambient pressure , such as when a scuba diver , a free-diver or an airplane passenger ascends or descends or during uncontrolled decompression of a pressure vessel such as a diving chamber or pressurized aircraft, but can also be caused by

3920-551: The decompression requirements of deep diving . Military applications include delivery of combat divers and their equipment over distances or at speeds that would be otherwise impracticable. There are accessories that can be mounted to a DPV to make it more useful, such as lights, compasses, and video cameras. Use of a DPV on deep dives can reduce the risk of hypercapnia from overexertion and high breathing rate. DPV operation requires greater situational awareness than simply swimming, as some changes can happen much faster. Operating

4000-602: The decreasing pressure until the lungs reach their elastic limit, and begin to tear, and is very likely to sustain life-threatening lung damage. Besides tissue rupture, the overpressure may cause ingress of gases into the tissues through the ruptures, and further afield through the circulatory system. Pulmonary barotrauma (PBt) of ascent is also known as pulmonary over-inflation syndrome (POIS), lung over-pressure injury (LOP) and burst lung. Consequent injuries may include arterial gas embolism , pneumothorax , mediastinal , interstitial and subcutaneous emphysemas , depending on where

4080-420: The descent, and expands back to the original volume during ascent. A scuba or surface-supplied diver breathing gas at depth from underwater breathing apparatus fills their lungs with gas at an ambient pressure greater than atmospheric pressure. At 10 metres the lungs contain twice the amount of gas that they would contain at atmospheric pressure, and if they ascend without exhaling the gas will expand to match

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4160-400: The diagnostic workup for the affected individual could include the following: Laboratory: Imaging: Barotrauma can affect the external, middle, or inner ear. Middle ear barotrauma (MEBT) is the most common diving injury, being experienced by between 10% and 30% of divers and is due to insufficient equilibration of the middle ear . External ear barotrauma may occur if air is trapped in

4240-410: The diver and the air in the hose can be several bar. The non-return valve at the connection to the helmet will prevent backflow if it is working correctly, but if absent, as in the early days of helmet diving, or if it fails, the pressure difference will tend to squeeze the diver into the rigid helmet, which can result in severe trauma. The same effect can result from a large and rapid increase in depth if

4320-401: The diver attached to the top. The New Zealand made Proteus is strapped onto the diver's cylinder. The Subskimmer is a submersible rigid-hulled inflatable boat (RIB). On the surface it is powered by a petrol engine, when submerged the petrol engine is sealed and it runs on battery-electric thrusters mounted on a steerable cross-arm. It can self inflate and deflate, transforming itself from

4400-527: The diver does not control the DPV properly, a rapid ascent or descent under power can result in barotrauma or decompression sickness. High speed travel in confined spaces, or limited visibility can increase the risk of impact with the surroundings at speeds where injury and damage are more likely. Many forms of smaller marine life are very well camouflaged or hide well and are only seen by divers who move very slowly and look carefully. Fast movement and noise can frighten some fish into hiding or swimming away, and

4480-435: The diver who holds onto handles on the stern or bow . Tow-behind scooters are most efficient by placing the diver parallel to and above the propeller wash. The diver wears a harness that includes a crotch-strap with a D-ring on the front of the strap. The scooter is rigged with a tow leash that clips to the scooter with releasable metal snap. Swimmer Delivery Vehicles (SDVs) are wet subs designed to transport frogmen from

4560-424: The diver, resulting in a pressure difference between the tissues and the gas space, and the unbalanced force due to this pressure difference causes deformation of the tissues resulting in cell rupture. Barotraumas of ascent, also called decompression barotrauma, are also caused when the free change of volume of the gas in a closed space in contact with the diver is prevented. In this case the pressure difference causes

4640-546: The ears using the Valsalva manoeuvre can overpressurise the middle ear, and can cause middle ear and/or inner ear barotrauma. An explosive blast and explosive decompression create a pressure wave that can induce barotrauma. The difference in pressure between internal organs and the outer surface of the body causes injuries to internal organs that contain gas, such as the lungs , gastrointestinal tract , and ear . Lung injuries can also occur during rapid decompression , although

4720-508: The emboli. Care must be taken when recompressing to avoid a tension pneumothorax . Barotraumas that do not involve gas in the tissues are generally treated according to severity and symptoms for similar trauma from other causes. Pre-hospital care for lung barotrauma includes basic life support of maintaining adequate oxygenation and perfusion, assessment of airway, breathing and circulation, neurological assessment, and managing any immediate life-threatening conditions. High-flow oxygen up to 100%

4800-523: The external auiditory canal over the eardrum, referred to by divers as ear squeeze , causing inward stretching, serous effusion and haemorrhage, and eventual rupture. During ascent internal over-pressure is normally passively released through the eustachian tube, but if this does not happen the volume expansion of middle ear gas will cause outward bulging, stretching and eventual rupture of the eardrum known to divers as reverse ear squeeze . This damage causes local pain and hearing loss. Tympanic rupture during

4880-423: The external ear canal and the middle ear. It is common in underwater divers and usually occurs when the diver does not equalise sufficiently during descent or, less commonly, on ascent. Failure to equalise may be due to inexperience or eustachian tube dysfunction, which can have many possible causes. Unequalised ambient pressure increase during descent causes a pressure imbalance between the middle ear air space and

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4960-601: The gas ends up, not usually all at the same time. POIS may also be caused by mechanical ventilation. Gas in the arterial system can be carried to the blood vessels of the brain and other vital organs. It typically causes transient embolism similar to thromboembolism but of shorter duration. Where damage occurs to the endothelium inflammation develops and symptoms resembling stroke may follow. The bubbles are generally distributed and of various sizes, and usually affect several areas, resulting in an unpredictable variety of neurological deficits. Unconsciousness or other major changes to

5040-406: The inflammatory response and resolution of oedema by causing hyperoxic arterial vasoconstriction of the supply to capillary beds. High concentration normobaric oxygen is appropriate as first aid but is not considered definitive treatment even when the symptoms appear to resolve. Relapses are common after discontinuing oxygen without recompression. A pneumothorax is an abnormal collection of air in

5120-419: The injury may be termed volutrauma, but volume and transpulmonary pressure are closely related. Ventilator induced lung injury is often associated with high tidal volumes (V t ). Other injuries with similar causes are decompression sickness and ebullism . A free-diver can dive and safely ascend without exhaling, because the gas in the lungs had been inhaled at atmospheric pressure, is compressed during

5200-413: The inner ear. A low internal pressure reduces decompression rate and severity in a catastrophic decompression reduces the risk of barotrauma but can increase the risk of decompression sickness and hypoxia in normal operating conditions. Some measures for protection against rapid decompression specific to airplanes include: Outside of a pressurized cabin environment at very high altitudes, a pressure suit

5280-555: The introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites or interfere with the normal function of an organ by its presence. The term is usually applied when the gas volume involved already exists prior to decompression. Barotrauma can occur during both compression and decompression events. Barotrauma generally manifests as sinus or middle ear effects, lung overpressure injuries and injuries resulting from external squeezes. Decompression sickness

5360-531: The mediastinal cavity round the heart, major blood vessels, oesophagus and trachea. Gas trapped in the mediastinum expands as the diver continues to rise. The pressure of the trapped gas may cause intense pain inside the rib cage and in the shoulders, and the gas may compress the respiratory passageways, making breathing difficult, and collapse blood vessels. Symptoms range from pain under the sternum, shock, shallow breathing, unconsciousness, respiratory failure, and associated cyanosis. The gas will usually be absorbed by

5440-399: The most common and easy to identify risk factors must be declared. If these factors are declared, the diver may be required to be examined by a medical practitioner, and may be disqualified from diving if the conditions indicate. Asthma , Marfan syndrome , and COPD pose a very high risk of pneumothorax. In some countries these may be considered absolute contraindications, while in others

5520-453: The most effective predictor of risk, but there is no generally accepted safe pressure at which there is no risk. Risk also appears to be increased by aspiration of stomach contents and pre-existing disease such as necrotising pneumonia and chronic lung disease. Status asthmaticus is a particular problem as it requires relatively high pressures to overcome bronchial obstruction. When lung tissues are damaged by alveolar over-distension,

5600-416: The range of the swimmer's scuba equipment. SDVs are typically used to land special operations forces or plant limpet mines on the hull of enemy ships. In the former usage, they can land a combat swimmer team covertly on a hostile shore in order to conduct missions on land. After completing their mission, the team may return to the SDV to exfiltrate back to the mother-ship. For extended missions on land,

5680-399: The relative negative internal pressure can produce petechial hemorrhages in the area covered by the mask along with subconjunctival hemorrhages . A problem mostly of historical interest, but still relevant to surface supplied divers who dive with the helmet sealed to the dry suit. If the air supply hose is ruptured near or above the surface, the pressure difference between the water around

5760-424: The risk of injury is lower than with explosive decompression. Mechanical ventilation can lead to barotrauma of the lungs. This can be due to either: The resultant alveolar rupture can lead to pneumothorax , pulmonary interstitial emphysema (PIE) and pneumomediastinum . Barotrauma is a recognised complication of mechanical ventilation that can occur in any patient receiving mechanical ventilation, but

5840-403: The same term [REDACTED] This disambiguation page lists articles associated with the title SDV . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=SDV&oldid=1192730256 " Category : Disambiguation pages Hidden categories: Short description

5920-492: The same. A variety of injuries may be present, which may include inner ear haemorrhage, intralabyrinthine membrane tear, perilymph fistula, and other pathologies. Divers who develop cochlear and/or vestibular symptoms during descent to any depth, or during shallow diving in which decompression sickness is unlikely, should be treated with bed rest with head elevation, and should avoid any activity which could cause raised cerebrospinal fluid and intralabyrinthine pressure. If there

6000-563: The standoff ability to attack from up to 3 nautical miles (5.6 km) away. The origins of the SDV stems from the Italian human torpedoes and the British Motorised Submersible Canoe used during World War II. These are torpedo or fish-shaped vehicles for one or more divers typically sitting astride them or in hollows inside. The human torpedo was used to great effect by commando frogmen in World War II , who were able to sink more than 100,000 tons worth of ships in

6080-493: The state of consciousness within about 10 minutes of surfacing are generally assumed to be gas embolism until proven otherwise. The belief that the gas bubbles themselves formed static emboli which remain in place until recompression has been superseded by the knowledge that the gas emboli are normally transient, and the damage is due to inflammation following endothelial damage and secondary injury from inflammatory mediator upregulation. Hyperbaric oxygen can cause downregulation of

6160-447: The symptoms, which depend on the affected tissues. Lung over-pressure injury may require a chest drain to remove air from the pleura or mediastinum . Recompression with hyperbaric oxygen therapy is the definitive treatment for arterial gas embolism, as the raised pressure reduces bubble size, the reduced blood inert gas concentration may accelerate inert gas solution, and high oxygen partial pressure helps oxygenate tissues compromised by

6240-400: The vestibular organs. High-pressure nervous syndrome during heliox compression is also a central nervous system dysfunction. Inner ear injuries with lasting effects are usually due to round window ruptures, often associated with Valsalva maneuver or inadequate middle ear equalisation. Inner ear barotrauma is often concurrent with middle ear barotrauma as the external causes are generally

6320-443: Was electrically propelled, with two crewmen in diving suits and rebreathers riding astride. They steered the torpedo at slow speed to the target, used the detachable warhead as a limpet mine and then rode the torpedo away. The nose of the torpedo was filled with pounds of TNT and would be hung under a ship's keel. The idea was successfully applied by the Italian navy ( Regia Marina ) early in World War II and then copied by

6400-421: Was making the noise of a pig while moored on the beach. The British versions were named " chariots ". The Motorised Submersible Canoe (MSC), nicknamed Sleeping Beauty , was built by British Special Operations Executive (SOE) during World War II as an underwater vehicle for a single frogman to perform clandestine reconnaissance or attacks against enemy vessels. The most common type of DPV tows

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