, , ,

Oxygen Toxicity: Too much of a good thing.

Oxygen is necassary for life, but as divers we are exposed to higher partial pressures of oxygen (pO2 or ppO2) than normal. A partial Dr Oliver Sykespressure is simply the fraction of the total pressure that an individual gas takes up in a mixture of gases. Therefore 21% oxygen at sea level has a pO2 of 0.21 bar.

There are 2 main types of oxygen toxicty that we need to limit, which are pulmonary (lung) and neurological oxygen toxicity. In order to obtain energy from food, oxygen is used to break strong molecular bonds at the cellular level and is necessarily a fairly reactive species. As humans, we have evolved to use oxygen at 0.21 bar and even a pO2 of 0.5 bar begins to overwhelm the body’s repair mechanisms very slightly. This pO2 is only 50% O2 at sea level or 25% O2 at 2 bar or 10m. Therefore 50% oxygen is not recommended for over 24hrs in healthcare settings due to lung oxygen toxicity. Unless absolutely necassary. With much larger increases over shorter periods, such as a pO2 of over 1.4 bar during diving, neurological oxygen toxicity becomes the main worry. This is manifested in violent fitting (uncontrolled movements of the arms and legs) and is often fatal when diving. Unfortunately drowning is common and ascent is dangerous due lung barotrauma from a closed wind pipe. Therefore even a full face mask is not safe and the only treatment is to reduce the high pO2. Unfortunately stressors make neurological oxygen toxicity more likely during diving and include exercise, cold, poor vis, nitrogen narcosis, raised blood carbon dioxide levels and psychological stress. These are present on all dives and for everyone to some degree.

During recompression treatment, the chamber environment does not risk drowning and we minimise the stressors. We also use air breaks to limit the time spent at high pO2 levels and therefore use 100% O2 to greater depths than in water.

Overall, neurological oxygen toxicity is a very rare event in chambers and simply requires the diver to be taken off oxygen. Given that recompression is a treatment, the additional risk from oxygen toxicity is therefore acceptable and the pO2 limit is significantly higher in chamber treatments. But only with good reason.

 

Question 1:

What do you do if a diver fits underwater?

100% O2 should not be breathed below 4-6m, as this gives a pO2 of 1.4 to 1.6 bar. If a diver is using breathing gas mixes enriched with oxygen and then fits at depth, the cause is likely to be oxygen toxicity and switching to the wrong mix can cause this. Ascent is clearly dangerous due to lung over expansion injury, but may be the only way to ensure help can be given. Make sure you are aware of this problem and are able to cope with it. Essentially, follow the guidence from your training agency at all times.

 

Question 2:

Are there any preceding symptoms prior to an oxygen toxicty fit?

Yes there are. These include blurred vision, ringing in the ears, nausea, twitching, irritability (anxiety, restlessness) and dizziness, which can progress to convulsions (fitting). These can be remembered with the letters VENTID-C  and can be difficult to pick up when diving. (Vision, Ears, Nausea, Twitching, Irritability, Dizziness, Convulsions)

 

Question 3:

What happens if someone has an oxygen fit in the chamber?

Our chamber attendants are trained to recognise the preceding symptoms and will take the diver off oxygen. If there is a convulsion, then they will pad the moving limbs and the fit will stop once off oxygen. Chamber pressure must not be altered during a fit. There is no long term damage, it is not epilepsy and has no impact on future diving or driving. We would then decide whether to continue the treatment or shorten it, depending on the reason for treatment and the state of the patient.

 

Question 4:

What is pulmonary (lung) oxygen toxicity?

The airways become narrower as a result of inflammation. There is often midline chest pain, cough and reduced lung function tests. Diving is unlikely to produce sufficient oxygen exposure. However some of the more extensive treatments for decompression illness may cause a degree of pulmonary oxygen toxicty. Thankfully this is often completely reversible.

 

Question 5:

Are air breaks useful in preventing oxygen toxicity at sea level?

Important: Do not use air breaks when using oxygen at the surface in an emergency situation, this is unnecessary and deprives the diver of a very important treatment.

 

A video from Divers Alert Network DAN follow the link below :

CNS Oxygen Toxicity – Richard Vann PhD

, ,

Flying after diving and flying after recompression

Dr Oliver Sykes

Dr Oliver Sykes

Many divers fly home after a diving holiday, but how many realise that this might have consequences and there are guidelines on how long they should wait? We often see divers at the hyperbaric unit who clearly have not waited long enough before flying and have developed decompression illness during the flight. Thankfully these are a tiny minority of divers and are not usually severe cases, but time to treatment is often delayed and can result in residual symptoms.

 

Why do we decompress during a flight? Commercial aircraft are pressurised to less than an atmosphere for a number of reasons, primarily financial. No planes are airtight and therefore leak. This requires compressors to maintain cabin pressure, which requires expensive fuel. However the pressurised plane is then heavier and this requires more fuel too. Therefore pressurising the fuselage to less than 1 atmosphere makes flying cheaper and we all decompress on the flight home. This is not a problem unless you’ve been diving recently. PADI appears to follow the DAN guidelines on flying after diving:

 

The following guidelines are the consensus of attendees at the 2002 Flying After Diving Workshop. (Alert Diver, November/December 2002, www.diversalertnetwork.org/files/FADWkshpBook_web.pdf) They apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) for divers who do not have symptoms of decompression sickness (DCS). The recommended preflight surface intervals do not guarantee avoidance of DCS. Longer surface intervals will reduce DCS risk further. For a single no-decompression dive, a minimum preflight surface interval of 12 hours is suggested. For multiple dives per day or multiple days of diving, a minimum preflight surface interval of 18 hours is suggested. For dives requiring decompression stops, there is little evidence on which to base a recommendation, and a preflight surface interval substantially longer than 18 hours appears prudent.

 

In reference to these guidelines, scubadoc states (http://www.scuba-doc.com/flyngaft.htm):

The above is for sports diving and should not apply to commercial diving or nitrox diving. Because of the complex nature of DCS and because decompression schedules are based on unverifiable assumptions, there can never be a fixed flying after diving rule that can guarantee prevention of bends completely.

 

After treatment for decompression illness, there also should be some time for recovery before flying. Damage from the bubbles of decompression illness is the result of many interactions, but one of the most basic problems is lack of oxygen (low partial pressure of oxygen) in the tissues. Unfortunately a lower partial pressure of oxygen in the tissues also occurs with the decompression and lower cabin pressure involved in commercial flights. Therefore flying after treatment for decompression illness should be discussed with the diving doctor. The US Navy Diving Manual (Rev 6) states: Patients with residual symptoms should fly only with the concurrence of a Diving Medical Officer. Patients who have been treated for decompression illness or arterial gas embolism and have complete relief should not fly for 72 hours after treatment, at a minimum.

 

Question 1:

Can I fly home immediately after a 40 min Discover Scuba session to 5m?

 

No. This is a single no decompression dive and you must wait at least 12 hours.

 

Question 2:

I am going to drive home over some hills that are around 1000ft above sea level. Is this OK within 12hrs of surfacing?

 

This is probably OK, but be aware that symptoms may still occur,especially if you ascend to altitude sooner rather later after surfacing. Anything below 2000ft (610m) should be fine. There are plenty of hills within the UK that are over this height and I have seen divers develop decompression illness as a result of driving home over the Pennines, for example.

 

Question 3

As a diving officer, what should I advise helicopter crews, if a diver requires airlifting to a chamber?

This needs to be discussed on a case by case basis with the diving doctor and the service providing the aircraft as there is a risk of worsening the decompression illness but there are also significant risks to flying low.

Advice usually includes:

Keep the diver on 100% oxygen

Use an aircraft pressurised to 1 atmosphere if available

Fly as low as possible, preferably below 1000ft

 

Question 4

I have a commercial diving medical from the Health and Safety Executive, what are their recommendations about return to diving after DCI?

Commercial diving is very different to sports diving, with far more control over depths, times, ascent rates, multilevel diving and number of dives per day. However the diver has less control over when he/she actually dives. Its therefore not really reasonable to compare the two. I would recommend that you discuss it with the diving doctor that treated you. The HSE guidelines can be found at: www.hse.gov.uk/diving/ma1.pdf

 

Question 5

Where can I get more advice on flying, diving and decompression illness?

 

The Divers Emergency Service
Telephone: +44 (0) 7999 292 999

 

We are based at London Hyperbaric Medicine in the East end of London. You can phone us from anywhere in the world and we will help you find your nearest chamber and diving doctor

, , , ,

Clearing your Ears In Water and Other Pressurised Environments.

As a diver, clearing your ears may be second nature. However we all had to learn at some stage and damage to your ears from over forceful clearing techniques is possible. So a quick reminder of the many techniques available may be useful.

The theory:

Your ears have an external tunnel that ends with a flexible ear drum. Imagine a real drum that gets compressed if you increase the pressure around it. (See a. in Figure 1.) The frame of the drum is like your skull and the skin of the drum is like your ear drum. Thankfully your ears differ significantly from a real drum! (See Ear anatomy picture below) For example, ach ear has a tube (See b. in Figure 2), which runs from behind the ear drum to the back of your throat. To stop your ear drum being pushed inwards, you need to increase the internal pressure behind your ear drum. You can do this by actively pushing air up these tubes. Unfortunately these tubes can work like flutter valves, hence can get stuck closed if you try too hard or allow the pressure to get too great before clearing your ears. Blockage can also occur when you have a cold and diving may not be possible. So you must not dive if you can’t clear your ears.

The external water pressure on the drum (Figure 1) and internal pressure generated by you (Figure 2):

 

The Techniques:

Try any of the techniques below early and often but perhaps start with 1. and  2. Everyone does it differently and works out which method works best for them. You will know when you have been successful when your ears “pop” and your hearing and perhaps balance returns to normal. Some of these are easier, in a recompression chamber rather than when diving.

1.         Swallowing, which is known as the Toynbee manoeuvre, drinking, sucking sweets, yawning, coughing, blowing your nose are all things we are used to doing and can be useful.

2.         Pinch your nose, close your mouth and try to blow out of your ears gently. Too hard will not work and can do damage. Watch other divers if you need to know how hard to try. This is known as the valsalva manoeuvre.

3.         The Lowry technique involves using all the above.

4.         Edmonds technique involves rocking the lower jaw from left to right and up and down and forwards and backwards, so that the lower teeth project in front of the upper teeth.

5.         Edmonds 2 advice: “Block your nose, close your mouth, then suck in your cheeks then puff them out quickly.”

6.         Try an otovent. (In chamber only) Occlude one nostril and blow up the balloon with the other nostril.  [youtube]

This content is blocked. Accept cookies to view the content.

[/youtube]

7.         A difficult one to describe is the Frenzel manoevre. This involves closing the mouth and nose and push the back of your tongue up to the roof of your mouth as you swallow.

8.         Some people get good at clearing their ears and can do it without seeming to do anything. This is an advanced technique not discussed here, but everyone started off by holding their nose and blowing gently out of their ears!

Blocked or painful ears are very common while the pressure is increasing and difficulty clearing your ears is nothing to be ashamed of, but pain is a sign of possible barotrauma and definitely to be avoided. Some people simply find it difficult, but the longer and deeper you leave it, the less likely you will be able to clear your ears.

Ear Anatomy

 

(Kindly reproduced from Wikipedia)

Question 1: Who was Valsalva?

He was a 17th Century Italian anatomist, who described this method for expelling pus from the middle ear through a perforated ear drum.

Question 2:

Can I cause a perforated ear drum by clearing my ears too hard?

Yes, but this thankfully only happens rarely and is probably most commonly associated with a pre-existing weakness in the ear drum. Round window rupture and disruption of the middle ear bones are also possible and barotrauma is possible from as little as 2m. Grommets are artificial tubes placed in the ear drum to allow passive ear clearing, but completely preclude diving. Perforated ear drums seem to me to be most commonly caused by jumping into water ‘ear first’

Question 3:

Can I use decongestants to help clear my ears?

Definitely avoid these and do not dive if you cannot clear your ears. If the medications wear off, the ‘reverse block’ may cause barotrauma, intense dizziness and prevent ascent due to pain.

Question 4:

How can I be sure that I am clearing my ears properly?

Practise gently in water and follow the advice from your instructor. If clearing your ears is still causing pain, avoid diving with an upper respiratory infection. Try descending feet first to reduce venous congestion and using the anchor chain to fine tune to the speed of descent. Small ascents may relieve a blockage due to the flutter valve effect. Finally, there may be a correctable cause and a visit to your doctor may be useful.

Question 5:

How can I tell the difference between inner ear DCI and inner ear barotrauma?

This is an important question as the treatments are entirely different. Inner ear DCI requires recompression, but this will worsen inner ear barotrauma. However both may present with dizziness, nystagmus, (eye flicking) nausea, vomiting and unsteadiness. Both are serious conditions and require assessment by a doctor experienced in diving medicine. Inner ear barotrauma is more likely when symptoms begin on compression, with a shallow dive profile and forceful ear clearing. There may be associated ear barotrauma signs and symptoms, such as pain, fullness, unable to clear your ears and red/damaged ear drum.

Whereas the symptoms of inner ear DCI may start after the beginning of the ascent from longer, deeper, mixed gas dives and there may be signs and symptoms of neurological DCI, such as numbness and weakness in the limbs

, ,

The History of Diving Chambers

Perhaps the first recorded diver, who was not a free diver, was Alexander the Great. He was said to have been lowered in to the Bosporus strait in a glass barrel in 320BC. Not much had improved by 1620, when Drebbel developed a diving bell which must have been severely limited as air was only replenished at one atmosphere. It was Henshaw, an English clergyman, who possibly constructed the first pressurized chamber for people on land in 1662. He called it the ‘domicilium’ and it was large enough to contain a piano and smoking room. Clearly this was before current theories on sound waves and bombs. At the very least, the denser air at pressure have altered the pitch and made the pipes burn much quicker! Sir Edmund Halley, of comet fame, probably developed the first useful diving bell, in which people remained underwater in the Thames for an hour and a half in 1691. Barrels of air were brought down to them which would have flushed out the carbon dioxide and replenished the oxygen. Perhaps also the first open circuit! The earliest recorded attempt at protecting a diver in rigid armour was made by John Lethbridge of Devonshire, England in 1715. The oak suit had a viewing port and holes for the diver’s arms and water was kept out of the suit by means of greased leather cuffs. The device was reported to have made many working dives to 60ft/18m. In 1774 Freminet, a French Scientist, reached a depth of 50ft and stayed there for an hour, using a helmet with compressed air pumped through a pipe from the surface.

Pressure vessel technology really only developed in the early to mid-1800s with the construction of bridges and tunnels. Triger developed open caissons in France, but water leak was a major problem and in 1830 Admiral Lord Thomas Cochrane patented the technique of using compressed air to exclude water. This technique was successful but was soon followed by reports of decompression illness in the workers. In 1854, Pol and Watelle reported that relief was obtained by workers who went back into the tunnels and Paul Bert showed that bubbles in the tissues during decompression consisted mainly of nitrogen in 1871. But it was only after the building of the New York tunnels under the Hudson and East rivers in 1889 and 1893 that the benefits were fully established. Early chambers at tunnelling sites were nothing more than boilers mounted horizontally with an airtight door at one end.

While Scheele discovered oxygen first in 1772, Priestly published first in 1775 and Lavoisier correctly described combustion in 1775. For hyperbaric oxygen, it was Drager in Germany who first realised the potential benefits of oxygen under pressure and devised a system for the treatment of decompression illness in 1917, but it was Benke and Shaw who first finally used hyperbaric oxygen to treat decompression illness in 1937. Official regulation and standards for hyperbaric oxygen therapy came together with The Undersea Medical Society, which was formed in the United States in 1967, and added, hyperbaric to its name in 1986. Diving chambers are now used for more than just recompression and there is a whole speciality called hyperbaric medicine. The Undersea and Hyperbaric Medicine Society publishes a complete list of indications for hyperbaric oxygen at http://membership.uhms.org/?page=indications

 

Question 1: Why is decompression illness also known as the Bends?

In the USA, the ‘Grecian bend’ was part of popular fashion at the time of building the Brooklyn Bridge, having been introduced into America as a dance move in the mid-1850s. This replicated the position adopted by the workers, presumably with severe girdle pain decompression illness and probably gave ‘the bends’ its name. One can imagine that the association with female attire provoked much joking amongst the men and contributed to the long history of divers making light of the pains of decompression illness.

Question 2: What does the word hyperbaric mean?

Hyper- comes from the Greek word ‘hyper’, meaning over or above and -baric refers to pressure, as in barometer and has its origin in the Greek word ‘baros’, meaning weight. In current scientific language, hyperbaric is an adjective used to describe an environment that is at pressure greater than atmospheric.

 

Question 3: What is the Paul Bert effect?

Central nervous system oxygen toxicity was first described by Paul Bert and is sometimes referred to as the “Paul Bert effect”. He showed that oxygen was toxic to insects, arachnidsmyriapods, molluscs, earthworms, fungi, germinating seeds, birds, and other animals. In humans this occurs as result of breathing increased partial pressures of oxygen and is the reason for limiting pO2 to 1.4 bar while diving. There is an initial syndrome of anxiety, twitching and nausea which develops into seizures which can easily be fatal underwater.

 

Question 4: What type of chambers exist today?

Hyperbaric chambers are classified into monoplace and multiplace chambers. Monoplace chambers are generally pressurised with oxygen and take one, or occasionally 2 people. There is therefore no need to where a mask, but the oxygen requirements are high as there is continuous flushing of the chamber. Multiplace chambers are more appropriate for emergencies as there is more room and allows for a chamber attendant and better monitoring. These chambers are pressurised with air and therefore require the patient to wear a mask or hood to breath oxygen at the correct pressure. Other features of multiplace chambers include size, entrance locks, and medical locks.

Question 5: Why did the British Navy use goats to research diving tables?

Haldane and the British Navy produced the first theory and set of tables determining ‘safe’ decompression schedules in 1906. While these contained fundamental flaws, the rates of decompression illness were reduced. It is said that goats were used instead of divers in the research because they are of similar size to humans, stamp their feet when in pain from decompression illness and have useful handles (horns) for getting them in and out of chambers. The unfortunate flock of goats was only been disbanded in Portsmouth about 20 yrs. ago, citing huge vets bills. No wonder!

 

Tunnelling work.

 

 

 

, ,

‘Cutaneous Manifestations of Decompression Illness’ Also known as ‘Skin Bends’

Because the bends can present in so many ways, the problems it can cause in the skin can be overlooked. Especially as rashes after diving are common. The overarching title: ‘Decompression Illness’ (DCI) includes decompression sickness (DCS) and arterial gas embolism (AGE), reflecting the 2 theories by which bubbles cause problems. However skin bends can be associated with both processes and therefore a descriptive classification of symptoms is the most useful method of communicating information. So what could be easier to describe and treat than a skin bend? However there seems to be a few problems.

Skin bends may not be seen as part of decompression illness. Rashes are common and determining whether a skin bend is present can be difficult. A skin bend is a rash with poorly defined edges, there may be varying degrees of redness, it may be itchy, may make the skin seem more like marble and may occur in a single area or in multiple areas. Finally the rash of a skin bend is not caused by sunburn, suit squeeze, harness straps, skin infections, bites or scratching, although all these may be present and confuse the picture. Simple cases of itching, burning and increased warmth occur after many dives and probably should not be recompressed, but should still be discussed with a diving doctor. In terms of severity, next comes cutis marmorata. This is described as marbling of the skin. Blood vessels constrict and dilate in different areas over a small patch of skin, producing areas of pale skin and redder areas. This then looks like marble and should certainly be discussed with a diving doctor.

At the other end of the scale, livedo reticularis is the most severe form, as seen in the picture above, and involves patchy, reddish-purple mottled areas, especially around the shoulders and trunk. This can be intensely itchy, due to a local vascular reaction from bubbles in the tissues below the dermis, and is clearly a systemic manifestation of DCS. These divers must be treated. Another skin symptom to take seriously occurs with blockage of the lymphatics with bubbles, resulting in swelling and a peculiar pitting of the skin called peau d’orange (meaning skin of the orange) and again is evidence of a more serious form of DCS, known as lymphatic decompression sickness.

In the past skin bends on the limbs were not considered severe enough to warrant treatment. However all symptoms that start after decompression has begun, however minor, can herald severe DCI and must be assessed by a diving doctor. There have also been recent reports of an association with skin bends with patent foramen ovale (PFO) and there are now recommendations that some divers with this condition be checked for PFO.

In order to help us improve our recognition of skin bends, please help us with our Skin Bend Image and Information Bank. Scroll down the page to find the correct article at: http://www.londonhyperbaric.com/category/blog and download the 3 forms. Please print off and fill in the consent form and questionnaire and send these to the address given. Finally lease email the relevant photos to the secure NHSMail email address: o.sykes@nhs.net. This will in no way affect your treatment by the Divers Emergency Service or London Hyperbaric Medicine.

We do need written consent, not emailed consent. Sorry!

Picture reprinted from The Lancet, Vol. 377, Vann RD, Butler FK, Mitchell SJ, Moon RE, ‘Decompression Illness,’ Pages 153-64, 2011, with kind permission from Elsevier.

 

 

Information for Participants

Research study: Skin Bend Image and Information Bank

We would like to invite you to be part of this research project.

You should only agree to take part if you want to and it is entirely up to you. If you choose not to take part there won’t be any disadvantages for you and choosing not to take part will not affect your access to treatment or services in any way. Please read the following information carefully before you decide to take part; this will tell you why the research is being done and what you will be asked to do if you take part. Please ask if there is anything that is not clear or if you would like more information. If you decide to take part you will be asked to sign the attached form to say that you agree. You are still free to withdraw at any time and without giving a reason.

Details of study:

There are many reasons for rashes after diving, but sometimes these are due to decompression illness. (The Bends) We at London Hyperbaric Medicine (LHM) would like to collect anonymous images and information on rashes that occur up to 72 hrs after diving in order to form a bank. This will be published on the LHM web site and blog (http://www.londonhyperbaric.com/category/blog), in a Sport Diver article (http://www.sportdiver.co.uk/), for teaching purposes, in a medical journal and in The Anaesthesia UK Image Bank, (http://www.frca.co.uk/imgdefault.aspx) if accepted for publication. This will form very useful resources for doctors and divers.

Every effort will be made to ensure that you are unrecognizable from the pictures. However this cannot be absolutely guaranteed. Once the pictures are on the web site, you may request for yours to be removed at any time.

Cautions:

If you think you may have skin decompression illness, any other form of decompression illness or serious cause for a rash, then contact the Divers Emergency Service immediately on:

+44 (0)7 999 292 999

In order to help maintain your safety and confidentiality, the images will not be free for all to use. LHM will need to hold the copyright to the images, but will not use the images in any other fashion without express prior consent from you.

, ,

Drowning

By Dr Oliver Sykes from Sport Diver/Divers Emergency Service

Drowning is death due to lack of oxygen (hypoxia) from suffocation caused by submersion in water and near drowning occurs where the victim survives an event that nearly resulted in drowning. According to the World

Health Organization, drowning is the 3rd leading cause of unintentional injury death worldwide, accounting for 7% of all injury related deaths (est. 388,000 deaths by drowning in 2004, excluding those due to natural disasters).

 

People in difficulty in the water may be in distress but still have the ability to keep afloat, signal for help and take actions. However those that drown fall into two categories: Passive or active drowning. In passive drowning people suddenly sink due to a change in their circumstances. Examples include people who drown in an accident, or due to sudden loss of consciousness or sudden medical condition. Active drowning occurs in non-swimmers and the exhausted or hypothermic at the surface, who are unable to hold their mouth above water and are suffocating due to lack of air. Instinctively, people in such cases perform well known behaviours in the last 20 – 60 seconds before being submerged, representing the body’s last efforts to obtain air. Notably such people are unable to call for help, talk, reach for rescue equipment, or alert swimmers even feet away, and they may drown quickly and silently close to other swimmers or safety.

Drowning can take place in other circumstances than those in popular awareness. For example, children have drowned in buckets and toilets, but most drownings occur when the victim is in water (90% in freshwater (rivers, lakes and pools), 10% in seawater). Drownings in other fluids are rare, and are often related to industrial accidents. Shallow water blackout is caused by hyperventilation prior to swimming or diving. The primary urge to breathe is triggered by rising carbon dioxide (CO2) levels in the bloodstream but hyperventilation artificially depletes this and leaves the diver susceptible to sudden loss of consciousness without warning from hypoxia on ascent as the oxygen levels fall. There is no bodily sensation that warns a diver of an impending blackout, and victims become unconscious and drown quietly without alerting anyone. They are typically found on the bottom. Secondary drowning occurs after inhaled fluid irritates the lungs, which then leak fluid and make breathing and ventilation more difficult.  Certain poisonous vapours, gases or vomit can have a similar effect. The reaction can take place up to 72 hours after a near drowning incident, and may lead to a serious condition or death. Therefore all cases of near drowning should be observed in an appropriate healthcare setting after the event. Examinations on human drowning victims show that there appears to be little difference between drowning in salt water and fresh water.

 

Management

Optimal pre hospital care is a significant determinant of outcome in the management of immersion victims worldwide. Bystanders should call the emergency services immediately and, as in any rescue initiative, initial treatment should be geared toward ensuring adequacy of the airway, breathing, and circulation (ABCs). Rescue may therefore simply involve bringing the person’s mouth and nose above the water surface but an individual may be rescued at any time during the process of drowning.  No two cases are entirely alike. The type of water, water temperature, quantity of water aspirated, time in the water, and individual’s underlying medical condition all play a role. For example hypothermic patients can appear dead and therefore all cases should be warmed up and an unconscious victim rescued with an airway still sealed from laryngospasm stands a good chance of a full recovery. Therefore bystanders and rescue workers should never assume the individual is unsalvageable unless it is patently obvious that the individual has been dead for quite a while.

 

Unfortunately a drowning person may cling to the rescuer and try to pull himself out of the water, submerging the rescuer in the process. Thus it is advised that the rescuer approach with a buoyant object, or from behind, twisting the person’s arm on the back to restrict movement. After a successful approach, negatively buoyant objects such as a weight belt are removed. The priority is then to transport the person to the water’s edge in preparation for removal from the water. The person is turned on their back with a secure grip used to tow from behind. If the person is cooperative they may be towed in a similar fashion held at the armpits. If the person is unconscious they may be pulled in a similar fashion held at the chin and cheeks, ensuring that the mouth and nose are well above the water. 

Airway and C-Spine

Pay attention to cervical spine stabilization if the patient has facial or head injury, is unable to give an adequate history, or may have been involved in a diving accident or motor vehicle accident. If possible, the individual should be lifted out in a prone position. Theoretically, hypotension may follow lifting the individual out in an upright manner because of the relative change in pressure surrounding the body from water to air.  In the patient with an altered mental status, the airway should be checked for foreign material and vomit. Debris visible in the oropharynx should be removed with a finger-sweep manoeuvre. The abdominal thrust (Heimlich) manoeuvre has not been shown to be effective in removing aspirated water; in addition, it delays the start of resuscitation and risks causing the patient to vomit and aspirate.

 

Breathing and Circulation

Rescue breathing should be performed while the individual is still in water, but chest compressions are inadequate because of buoyancy issues. Once on firm ground, chest compressions are performed if the patient is pulseless, and if they are not breathing rescue breaths. The highest concentration of oxygen should be given as early as possible. If available, continuous non-invasive pulse oximetry is optimal. If the patient still has difficulty breathing on 100% oxygen or has a low oxygen saturation, use continuous positive airway pressure (CPAP) if available and if you are trained to do so. Also consider early intubation, with appropriate use of positive end expiratory pressure. Higher pressures may be required for ventilation because of the poor compliance resulting from pulmonary oedema. Transfer the patient to the nearest appropriate medical facility and consider that treatment for hypothermia may also be necessary.

 

 

, ,

ASTHMA: Why Can I Not Dive?

ASTHMA: Why Can I Not Dive?

Asthma is similar to having an allergy. There are triggers, such as cold, exercise and emotion induced asthma, the attacks are intermittent and can vary in severity. At a cellular level, there are complex inflammatory interactions that are incompletely understood. However ultimately, the responses to asthma and allergies do not improve survival chances.

While most cells in the lungs are pneumocytes, that exchange CO2 for O2 with every breath, there are also mucus secreting cells and muscle cells, which widen and narrow the diameter of the conducting tubes. Mucus helps remove foreign material and wider diameter tubes are required to exchange more gas during exercise.

 

Asthma has 2 effects during an attack. There is more mucus production and there is significant airway constriction. As air passes through narrowed tubes, further obstructed with mucus, there is wheeze, chest tightness and shortness of breath. Wheeze means air trapping in the lungs, which can lead to pulmonary barotrauma, pneumothorax and air embolism. Some of the most feared complications in diving. While the extent of an attack varies hugely, from barely noticeable to life threatening, divers die every year due to asthma.

How can we make sure it’s not you? People with cold, exercise or emotion induced asthma must avoid diving altogether. While a little wheeze can be annoying while playing football, there are additional factors that make scuba diving completely different from the usual sports. For example dry gas and salt water aspiration act as additional triggers for asthma and make asthma attacks worse. There may well be a decompression obligation, meaning a controlled emergency swimming ascent, or immediate surfacing, is not safe during an attack, especially with the additional gas trapping. However most importantly, an asthma attack reduces exercise tolerance and can turn a dangerous situation into a life threatening emergency. Unlike football, with scuba diving, you cannot simply stop play and call for help.

The UK Sports Diving Medical Council has been instrumental in creating guidelines to allow some asthmatics to dive. Look under medical standards, then respiratory and then asthma at www.uksdmc.co.uk. Previously any history of wheeze meant no diving. Currently the guidelines state:

Asthmatics may dive if they have allergic asthma but not if they have cold, exercise or emotion induced asthma.
All asthmatics should be managed according to British Thoracic Society guidelines
Only well controlled asthmatics may dive
Asthmatics should not dive if he/she has needed a therapeutic (required for symptom control) bronchodilator in last 48hrs or has had any other chest symptoms, such as cough or chest tightness.

A puff or 2 of ventolin, often the blue inhaler, before a dive TO RELIEVE SYMPTOMS is not safe. As prevention however, 2 puffs of ventolin before a dive is acceptable. The bottom line is that asthma can be life threatening under water and must be taken seriously.

Question1:
I play football 2 or 3 times a week, I wheeze a little when it’s cold, but my asthma does not stop me doing anything. Can I still dive?
This is a common question and people are often surprised at being told they cannot dive because of asthma, which may not limit their other activities. However breathing compressed gas at depth provides a number of triggers that are not present on land, so an attack may be more severe than expected, and help is more difficult to provide, as diving is usually remote and ascent is dangerous. Unfortunately asthma can also be stable for months and years and then flare up with an acute attack. So no diving with exercise, cold or emotion induced asthma.

Question2:

 I take a steroid (brown) inhaler along with my ventolin (blue) inhaler. Can I still dive?                                            You need assessment from a diving doctor. You may, or may not, be able to dive safely.

Question3:
Why do diving doctors vary their requirements for a diving medical for asthma?
All diving medicals for asthma should include taking down a history of your asthma and an exercise test. There is no point in having a medical if you have exercise, cold or emotion induced asthma, as these prevent safe diving. If you are going for a medical, remember that everyone with asthma is affected differently and the doctor needs to be sure that your will not have a life threatening asthma attack under water. You will be asking the doctor to take some responsibility for your health, so the doctor will want to be as stringent as he/she feels necessary.

Question4:
How can I improve my asthma control?
Primarily, make sure that you have a doctor in charge of you asthma, take the medications as directed by them and avoid triggers. The treatment may include inhalers, nebulisers or tablets, but unfortunately if you are on tablets or nebulisers, then your asthma is too severe to consider diving. Stopping smoking and weight loss can help too. If you are prescribed a steroid (brown) inhaler, remember to take it. This is a preventer medication and takes days/weeks to work. Once taken regularly, there should be fewer symptoms, less ventolin required and therefore less air trapping and safer diving.

 

Question5:                                                                                                                                                                                             I have been assessed as fit to dive with my asthma, but how do I know if my asthma is good enough to dive?  If there is any cough, wheeze or chest tightness, then you should not dive. If you have needed medications, including inhalers, for any chest symptoms then no diving again for 48hrs from last dose. Monitoring your own peak expiratory flow rate (PEFR, peak flow) can help you gain control of your asthma and balance the need for treatment. However it is not possible to give an absolute figure for peak flow for safe diving, as asthma can vary considerably and the presence of symptoms is much more important.

 

 

 

 

 

Fluticasone propionate metered dose inhaler commonly used for long term control.

 

 

 

 

 

 

 

 

 

Salbutamol metered dose inhaler commonly used to treat asthma attacks.

 

 

 

 

 

Pictures courtesy of wikipedia

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

,

New release: Baltic Gold written by Phillip Sayers

If you’re looking for a fantastic read on your next dive trip, holiday, bed time read or if you love a fact based drama, how about this one Baltic Gold. This book will have you on the edge of your seats, wanting more. When I read it I could not put it back down!

Based on actual events, Baltic Gold is full of desperation, disaster and discovery. Written by our very own Phillip Sayers.

“A tremendous tale of diving exploits and second world war history. The author’s detailed research and outstanding diving knowledge has created a great diving and war-history based adventure which is fascinating, and exciting to the end.”

David Smith – CEO, National Hyperbaric Centre

“A very good story based on historical fact, which always makes these novels more interesting. It is a moving credible story with plenty of action. I think the HMS Edinburgh divers would be very embarrassed to read parts of it.”

Ric Wharton – Author of ‘Salvage of the Century’
                                                                                                                                                                                                                                                                                                                                                                                                                            To buy or preview this book go to :   www.balticgold.com
, ,

HSE Scuba Chamber Orientation Course

Our courses are proving to be very popular the moment.

As a result of the interest, we are pleased to announce the next dates; it’s short notice, however here are the dates:
HSE scuba chamber orientation course running on the 9th August, this is a 1 day course and is a Prerequisite of the HSE Professional Scuba.

 

The final part of HSE Professional Scuba can be booked and paid for with Andark Divers direct.

The HSE Professional Scuba (old part 4 course) is the first rung of the ladder in the Commercial diving world. It will take any existing diving qualifications and add to them to produce a competent working diver using Scuba equipment.  As part of the HSE phase you are also required to complete a recompression chamber course for 1 day.

Prerequisites

HSE diving medical, PADI rescue diver or equivalent.

Course Goals

Enable course participants to:

1. As a member of a dive team, have knowledge of the Pre-Dive procedures for a two compartment compression chamber.

2. As a diver, to carry out a dry dive to 40msw with a view to experiencing possible nitrogen narcosis.

3. As a member of a dive team and under supervision have a working knowledge of the functions and procedures for operating a two compartment compression chamber.

4. As a member of a dive team, have a working knowledge of the post dive compression chamber checks and user maintenance.

5. As a member of a dive team and under supervision, have a working knowledge of the function and procedures for acting as an attendant inside a two compartment compression chamber.

6. As an inside attendant in a compression chamber have a working knowledge of the conduct of a therapeutic recompression.

 

Course Materials

Course Materials will be supplied.

Course price £150 (price is for Scuba Chamber Orientation course – deposit £50)
Prices

HSE initial medical £100.

HSE follow up medical £80.

Book the course and medical at the same time to receive £20 discount.

Course to be run from 08.30 to 16.30 with 3/4 hour lunch break

Contact

training@londonhyperbaric.com

http://www.andark.co.uk/diving/hse-pro-scuba

, , ,

Seasickness

Diving from a liveaboard off Pemba, The Green Island, is apparently amazing. However I spent 3 days in bed, feeling very green. Kitting up just once was hell. While some get benefit from being underwater and rush to get in, even the small wave motion underwater was enough to make me feel like vomiting. Everyone who has hearing and a functioning vestibular system is susceptible to motion sickness. Numbers are roughly split into 1/3 that are highly susceptible, 1/3 suffer in rough conditions and 1/3 only in extreme conditions. The books always discuss an imbalance between the 3 sensory modalities for spatial awareness. These include proprioception, which is joint position sense, vision and the vestibular system, which is the sense of movement and balance. However there is also clearly a psychological input. Once begun, seasickness is more difficult to get rid of, but it is also catching and distraction may help reduce it. Hence remedies tend to work better if in place before the motion and the thoughts get out of hand. If I was away for longer, I may have managed some diving as often sea sickness gets better after 2-3 days at sea.

 

Hyoscine, meclizine and cinnarizine (stugeron, TM) work by reducing vestibular inputs and can be sedating. Most people do not have any serious problems with these medications; however there is the possibility of side effects, drug interactions and effects on pre-existing medical conditions. Therefore these medications should be discussed with a doctor before diving. Carl Edmonds recommends the trial use of any medication that cause drowsiness to ensure no untoward reactions and to dive shallower than 18m to avoid narcosis. For this reason alcohol must also be avoided. The most common side effects of seasickness medications are:

·        Drowsiness

·        Headache

·        Dizziness

·        Agitation

·        Poor concentration

·        Fast heart rate

·        Dry mouth

·        Blurred vision

·        Difficulty passing urine

·        Stomach and gut upsets

 

Closing your eyes, or looking at the horizon, reduces the conflict between balance and visual inputs, which is worsened by going below deck. Lying down along the boat’s centre line, toward the stern and minimizing head movements, reduces proprioceptive input by incurring the least complex movements. However it’s also the best place for a smelly engine and for navigating the boat. So may incur the wrath of those still capable of useful function and compound the demoralising effects of seasickness.

 

An approach that involves different mechanisms to prevent sea sickness may work well. For example, chewing fresh ginger, good hydration and acupressure are safe with cinnarizine. The acupuncture point known as Pericardium 6, traditionally has been used to help relieve nausea. It is located on the inside of the wrist, about the length of 2 fingernails up the arm from the centre of the wrist crease. Many travel stores sell wrist bands with built in buttons designed to apply acupressure to this point, which has no significant side effects.

The following nutritional tips may help reduce symptoms, improve overall health and should be considered before taking medications:

·        Avoid spicy, greasy, or fatty meals, alcohol and hangovers

·        Don’t overeat

·        Drink plenty of water.

·        Dry crackers and carbonated drink (such as ginger ale) may help

Peppermint tea, black horehound, biofeedback, cognitive behavioural therapy, hypnosis and breathing exercises have also worked for some people. Probably through relaxation. However no treatments are known to be effective in all cases and if symptoms do not resolve soon after arriving on dry land then it’s time to phone the doctor.

 

Finally, dehydration is worth a special mention as it is common, associated with sun and alcohol, and can predispose sufferers to sea sickness, vomiting and more dehydration. The outflow from the stomach (pyloric sphincter) may also stay constricted and stop oral fluids and drugs from reaching their site of action. Hence intravenous, intramuscular or rectal routes may be required to correct the imbalance of electrolytes in the blood and the increased risk of decompression illness. Dehydration is definitely one predisposing factor to avoid.

 

Questions

1) I recently went on a day trip to complete my Advanced Open Water course with the Deep dive. On the way to the site I suffered with seasickness and one of the other divers advised that I didn’t do the deep dive as I was more likely to get bent on the dive because I was seasick. I did complete the dive in the end and had no decompression sickness symptoms afterwards but wanted to know if this was really true and whether I was taking a risk doing the dive?

 

There is no reason why seasickness would directly cause decompression sickness. However dehydration and poor concentration due to sedative medications, rushed kitting up or feeling unwell can contribute to an increased risk. So if you are a seasickness sufferer, then you should be aware of these problems and minimise the effects before diving.

 

2) I suffer occasionally from seasickness and have seen other divers use all sorts of patches and natural remedies. I don’t like to take medicines so I’m keen to know whether these more natural methods really work?

 

Patches for seasickness are usually hyoscine, which avoids the oral route and generally provides a low dose for longer than tablets. There is no guaranteed cure for seasickness, so I cannot say what will work for you, but it is worth trying a range of remedies. Examples of the more natural remedies with the best evidence are probably ginger and acupuncture. A review of the use of ginger in American Family Physician journal in 2007, described 4 trials of its use in motion sickness. 2 trials showed there was benefit and 2 did not. For acupuncture, there does not seem to be any serious reviews for its use in motion sickness. However there are many similarities with post operative nausea and vomiting, for which there is some significant trials and reviews that suggest there may be some benefit.

 

3) Do I need to take sea sickness tablets before I go on the boat or can I take them if I start to feel sick?

Sea sickness tablets are for prevention, not cure. Hence are best taken before leaving the land in order to give the medications time to work. For precise timings, read the information sheet that comes with all over the counter medications. Different drugs will take different times to work, but at least an hour will be required before significant benefit and probably more for full benefit. Once you feel sick, medications are much less likely to work, if at all. So take them early and read the information sheet.

4) Should I eat something before taking sea sickness tablets?

Seasickness tablets do not have to be taken with food but can be. If you are likely to feel sea sick, then eating small amounts before travelling may be a good idea and good hydration prior to travelling is a must.

5) Can I take sea sickness tablets if I’m pregnant?

Hyoscine, meclizine and cinnarizine (stugeron TM) are not advisable in pregnancy. As with most medications, there is little research into the effects on pregnancy. However, if you have taken seasickness tablets while pregnant, then speak to your doctor. On balance, long term effects are very unlikely. A few grams of ginger and wrist bands are safe.

 

References:

Am Fam Physician. 2007 Jun 1; vol. 75(11) pp. 1689-91

Ginger: an overview.

White B

 

Br J Anaesth. 2009 May; vol. 102(5) pp. 620-5

P6 acustimulation effectively decreases postoperative nausea and vomiting in high-risk patients.

Frey UH, Scharmann P, Löhlein C, Peters J

 

J Neurosurg Anesthesiol. 2010 Apr; vol. 22(2) pp. 128-31

Electroacupoint stimulation for postoperative nausea and vomiting in patients undergoing supratentorial craniotomy.

Wang XQ, Yu JL, Du ZY, Xu R, Jiang CC, Gao X

 

Anaesthesiol Scand. 2009 Nov; vol. 53(10) pp. 1341-7

Effect of P6 acustimulation on post-operative nausea and vomiting in

patients undergoing a laparoscopic cholecystectomy.

Frey UH, Funk M, Löhlein C, Peters J