Archive for January, 2007

BAROTRAUMA & DYSBARISMS #9

January 31, 2007

DECOMPRESSION SICKNESS (DCS):

Rapid reduction in ambient pressure, during ascent, causes dissolved gases to come out of
solution and form bubbles of nitrogen, the oxygen is rapidly metabolized in the tissues.

Gas bubbles can: 
– obstruct small blood vessels
– cause changes in blood chemistry
– stretch and damage tissues

Symptoms present within 12 hours.
– 80% within 1 hour of surfacing.
– 95% within 4 hours of surfacing.

TYPE I  – musculoskeletal limb pain
BENDS = periarticular pain in arms & legs (arms > legs)
pain relieved by direct pressure
pain can be mild, “Niggles,” to severe
skin/lymphatic involvement = pruritus, marbling, rashes

TYPE II – neurological
pain in areas other than the extremities
CNS changes = cord involvement or cerebral
spinal cord DCS = most common form of DCS in divers
paresthesia s – ascending numbness – paraplegia
urinary retention – fecal incontinence – priapism

Cerebral DCS:
classic CVA symptoms
pulmonary manifestations – “CHOKES”
occurs within minutes of surfacing
substernal chest pain – cough – dyspnea
can progress to respiratory failure and shock
labyrinthine or inner ear DCS – “STAGGERS”
vertigo – nausea/vomiting – tinnitus – hearing loss – nystagmus
                 
TREATMENT FOR DCS TYPE I & II:    
RECOMPRESSION
100% oxygen (helps to wash out nitrogen)
IV fluid therapy with crystalloid (hemoconcentration)
diazepam or phenergan for vertigo – nausea – vomiting
should not dive for 6 months after DCS & not until full evaluation

RECOMPRESSION – HYPERBARIC THERAPY
to reduce the size of the bubbles
to promote reabsorption
prevent further bubble production

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BAROTRAUMA & DYSBARISMS #8

January 29, 2007

ARTERAIL GAS EMBOLISM:  (AGE)Most serious of all dive injuries – frequently fatal.
Second only to drowning in fatalities in sport divers.
Ruptured airways allow air bubbles to enter the pulmonary circulation and go to the left side of the heart.
From the left ventricle may migrate to the coronary or cerebral circulation.
Resulting in:
ACUTE MYOCARDIAL INFARCTION (AMI)
CEREBROVASCULAR ACCIDENT (CVA)
AGE usually presents within 10 minutes of the “burst lung”.

SYMPTOMS: 
CVA = neurological symptoms:
change in mood or affect
visual disturbances
hemiplegia or hemiparesis
unconsciousness

AMI = apnea – dyspnea
chest pain – chest pressure
dysrhythmia s – asystole

SUDDEN LOSS OF CONSCIOUSNESS BEFORE SURFACING IS AGE UNTIL PROVEN OTHERWISE

TREATMENT:  RECOMPRESSION!!!
100% O2 while transporting
Transport supine & MONITOR AIRWAY

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BAROTRAUMA & DYSBARISMS #7

January 27, 2007

PNEUMOMEDIASTINUM & INTERSTITIAL EMPHYSEMA:
Ruptured airways allow air to escape into the soft tissues.
Air dissects into the mediastinal – into the pericardium – cephalad into the neck.

SYMPTOMS: 
subcutaneous air & crepitus on compression of the skin – neck
change in voice
dyspnea
pericardial air on x-ray

TREATMENT: 
Interstitial (subcutaneous) emphysema is not dangerous.
100% O2 will hasten recovery.
Must be monitored for other sequela = pericardial tamponade.

PNEUMOTHORX:   (TENSION PNEUMOTHORAX)
Ruptured airways allow air to escape into the pleural space.
Air trapped in the pleural space.

SYMPTOMS: 
Vary from mild to severe dyspnea with cyanosis.

TREATMENT: 
Monitor if mild.
100% O2 in severe cases, may require artificial ventilation.
Chest tube thoracotomy for severe = tension pneumothorax.
Needle thoracotomy in emergency.

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BAROTRAUMA & DYSBARISMS #6

January 25, 2007

ASCENT INJURIES:  “REVERSE SQUEEZE”

ASCENT   = expansion of the gas.     
The volume of gas increases by 2, doubles, every 33 fsw.

This is why it is an absolute rule that people with asthma cannot SCUBA dive!
ASTHMA and SCUBA diving = death
.
During ascent some of the air breathed at depth will get trapped in the alveoli and bronchioles, then during ascent that trapped air will expand and burst the alveoli and bronchioles, resulting in burst lungs and DEATH.

PULMONARY OVERINFLATION:
“Pulmonary Over Pressurization Syndrome” – POPS = “Burst Lung”
Usually occurs with a rapid ascent and breath holding.
Gas in the lung expands rapidly causing alveolar rupture.  (Boyle’s Law)
Alveolar rupture allows air to be forced into other tissues/spaces.
Resulting in escape of air under pressure into the:
Mediastinum = PNEUMOMEDIASTINUM/INTERSTITIAL EMPHYSEMA
Pleural Space = PNEUMOTHORAX
Pulmonary Venous System = ARTERIAL GAS EMBOLISM  (AGE)

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BAROTRAUMA & DYSBARISMS #5

January 22, 2007

ALTERNOBARIC VERTIGO: 

This occurs when there is unilateral pressure difference between middle & inner ear.
More common during ascent then descent.

SYMPTOMS: 

sudden transient vertigo – usually less than one minute.
overwhelming feeling of disorientation.
vertigo may persist on the surface.
accompanied with nausea, vomiting, nystagmus.
no tinnitus

TREATMENT: 

usually not required = transient.
decongestants may speed recovery, 
(occasionally a myringotomy is required.)

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BAROTRAUMA & DYSBARISMS #4

January 20, 2007

EXTERNAL EAR SQUEEZE:   “Barotitis externa”

The External Auditory Canal (EAC) is occluded by cerumen, ear plugs, or wet suit hood. 
As the external pressure increases during descent the “plug” prevents the outside pressure from equalizing in the EAC. 
The EAC becomes edematous and hemorrhagic.
Pain is not relieved by Valsalva or Frenzel maneuver.

PREVENTION:   STOP THE DESCENT and ASCEND to where it is pain free.

TREATMENT:    
Cortisporin Otic Solution or other steroid ear drop.

INNER EAR BAROTRAUMA:  “Barotitis interna”

A pressure differential develops between the middle and inner ears that causes an implosion or explosion of the round or oval windows that separate the inner and middle ear.

SYMPTOMS: 
sudden onset
severe vertigo
roaring tinnitus
nystagmus
fullness of the affected ear
sensorineural hearing loss
does not improve with ascent

TREATMENT:  Antivertigo drugs:
meclizine (Antivert)
diazepam (Valium)
Follow-up with ENT before diving again

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BAROTRAUMA & DYSBARISMS #3

January 18, 2007

BAROTRAUMA:  (Boyle’s Law) DESCENT = compression of the gas.  (volume decreases by 1/2 every 33 fsw)
ASCENT   = expansion of the gas.      (volume increases by 2 every 33 fsw)
(fsw = feet of sea water)

Boyle’s Law – This is why it is an absolute rule that people with asthma cannot SCUBA dive!ASTHMA and SCUBA diving = death.
During the dive some of the air breathed in at depth gets trapped in the alveoli and bronchioles.
Then during ascent that trapped air will expand and burst the alveoli and bronchioles, resulting in burst lungs and DEATH.
         
DESCENT INJURIES:  “SQUEEZE INJURIES”
DESCENT = compression of the gas.  (volume decreases by 1/2 every 33 fsw)

MIDDLE EAR SQUEEZE:  “Barotitis media”
The Eustachian Tube that connects the middle ear to the sinuses is not venting properly.
This prevents the air pressure from the SCUBA tank from getting into the middle ear. 
As a result, there is more pressure outside then in, increasing the pressure against tympanic membrane.
This causes the tympanic membrane (TM) to be pushed inward, causing pain and bleeding of the TM.
Increased pressure in middle ear causes mucosal bleeding and edema of the TM and the middle ear tissues.
If the diver ignores the pain and continues to descend the pressure will increase and the tympanic membrane may rupture inward. 
Water then rushes into the middle ear causing severe vertigo as a result of caloric vestibular stimulation.
 
PREVENTION: 
Valsalva or Frenzel maneuver, to equalize the pressures between the sinuses and the middle ear.   
Long-acting Decongestants/Antihistamines used for 3 days prior to dive.
Inhaled Nasal Steroids used for 7 days prior to dive.

TREATMENT:  
STOP THE DESCENT and ASCEND to where it is pain free.
Decongestant/Antihistamine.
Monitor for onset of Otitis Media.

CONTRAINDICATIONS FOR A DIVE:
Perforated Tympanic Membrane
Sinusitis
Upper Respiratory Tract Infection
Asthma is an absolute contraindication to diving, ever.

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BAROTRAUMA & DYSBARISMS #2

January 16, 2007

BREATHING A GAS UNDER PRESSURE: (Henry’s Law)

NITROGEN NARCOSIS:  “rapture of the deep”
Breathing nitrogen under pressure has an anesthetic-like effect.
In SCUBA diving there is the “Martini Rule” = every 50′ of depth is like having one martini.
Symptoms are similar to being inebriated:
At 100′ you may feel lightheaded, euphoric, have poor reaction timing, and POOR JUDGEMENT.
At 300′ you may become unconscious.
You most likely will not realize that you have “rapture of the deep” just like you don’t know how drunk you are.  You have to rely upon one another to keep an eye on each other.

CARBON MONOXIDE:  

A little goes a long way. 
Have to make sure that your SCUBA tanks are properly filled and there is no risk of CO contamination. 
A very small quantity of CO in the pressurized air you breathe will lead to loss of conscious while diving.
Symptoms of CO poisoning are unconsciousness, drowning, and DEATH.

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SCUBA DIVING INJURIES – BAROTRAUMA & DYSBARISMS #1

January 14, 2007

SCUBA Diving Injuries: Barotrauma & Dysbarism 

This is a review series on injuries and emergencies that can occur SCUBA diving.
We have to remind ourselves that we do not belong under the water, breathing compressed air out of a tank on our backs.  To do so requires fitness, training, and a trust in the technology that allows us to breath underwater.

Mechanism of Injury of Barotrauma:


Breathing a Gas Under Pressure
Pre-dive on the Surface = Environmental Exposure
Descent Injuries – Increasing Pressure = Compression Injuries or Squeeze Injuries
Bottom Time = Saturation Injuries
Ascent – Decreasing Pressure = Decompression Injuries
Post-dive on the Surface = Environmental Exposure
In the Ocean = Hazardous Marine Life

THE GAS LAWS That All Divers Must Know:

BOYLE’S LAW:   
The volume of a gas varies inversely with the pressure.
Increase the pressure = decrease the volume (squeeze)
Decrease the pressure = increase the volume (expand)

CHARLE’S LAW:   
The volume of a gas varies with temperature.
Cold gas = less volume,  Warm gas = more volume

GENERAL GAS LAW:  
Pressure 1 x Volume 1  =  Pressure 2 x Volume 2
  Temperature 1                   Temperature 2

DALTON’S LAW: 
Law of partial pressures: P = Pp1 + Pp2 + Pp3 ….
Total pressure (P) = sum of all the partial pressures (Pp), nitrogen + oxygen + …

HENRY’S LAW: 
As pressure increases the amount of gas dissolved into the body increases. 
Bottom time = saturation of gas in tissues.
 
ATMOSPHERIC ABSOLUTE (ATA): 
The atmospheric pressure at sea level is 1 ATA =:
14.7 psi (pounds per square inch)
29.9 inmg (inches of mercury)
760 mmhg (millimeters of mercury) or Torr
1033 g/cm2 (grams per centimeter squared)
1013.3 mbar (millibars)
10.08 msw (meters of sea water)
33 fsw (feet of sea water)
34 ffw (feet of fresh water)
Every 33 feet of sea water adds 1 ATA…so at 100′ you are at 4 ATA.

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Soft Tissue Injuries #4 – Abscess Formation

January 10, 2007

The Principles of Incision & Draining of an Abscess:

Picture – Assess and evaluate the abscess and surrounding anatomy.
Prep – clean and prep the area of the skin to be incised.
Pain control – if possible numb the skin with ice or inject with lidocaine.
Puncture the abscess – with a scalpel or sharp knife pierce the abscess.
Purge – gently compress and drain the abscess.
Purify – rinse the abscess clean with iodine solution.
Protect – cover with a sterile dressing and monitor during evacuation.

Stitches & Wound Closure:

  • Wounds edges may be approximated but, they should not be closed unless the wound can be thoroughly cleaned and closed in sterile fashion.Wound repair and closure is rarely functional; it is almost always cosmetic.If a wound heals with a scar, the scar can later be removed and the wound sutured closed for a better result.

    Bite wounds should never be closed as they are very dirty wounds, from the bacteria from the animal’s mouth. 

    Always consider tetanus booster for dirty wounds. Tetanus immunization is good for 10 years.

    Always consider rabies prophylaxis for animal bites.

So, in the wilderness setting:

  • Control bleeding.

    Properly and thoroughly scrub and clean the wound.

    Approximate the edges, but do not close the wound.

    Dress and bandage the wound to protect and promote healing.

    With loss of function splint to support the extremity.

    Change dressings at least two times per day.

    Monitor for signs of infection.

    If the wound is going to continue to get wet, use iodine wet-to-dry dressings to prevent infection.

For more detailed information on wilderness and long-term management of Soft Tissue Injuries see the Jan/Feb 2006 and the March/April 2006 issues of the Wilderness Medicine Newsletter.