HBOT Safety/Review Questions #2
In the monoplace chamber with an extremely high concentration of oxygen under pressure, elimination of ignition is a key method of reducing the hazard of combustion. Which of the following are possible ignition sources for hyperbaric environments?
Sparks or arcs from electrically powered devices
Frictional or impact sparks
Electrostatic sparks
Introduction of pre-heated devices into the chamber
Hand warming devices
ANSWER: All of the above.
All of the above are possible ignition sources, and all must be avoided for a safe hyperbaric oxygen therapy session to occur. (Reference, Workman, W.T., Hyperbaric Facility Safety, Best Publishing, 1999, page 513, Table 6). The effective way to prevent ignition is to avoid placing anything in the chamber except patients and 100% cotton towels or 100% cotton bandaging to cover any catheters, external fixators, etc. Patients should not be allowed to contact each other in the chamber. Non-metallic treatment modules should be employed where necessary and appropriate. Metal to metal contact in a pressurized hyperbaric oxygen chamber must be strictly disallowed.
Thorough cleaning of the hyperbaric oxygen therapy chamber and treatment modules should be performed between each treatment session.
A 100% cotton towel soaked in dishwashing soap solution followed by a 100% cotton towel soaked with water is appropriate for the final cleaning. The bottom of the chamber should be checked frequently and regularly for accumulation of hair and animal dander, as they are combustible substances.
How often should a regular preventative inspection and maintenance be scheduled with a trained professional hyperbaric oxygen chamber service company (or the manufacturer's technical service department)?
Every 4 months
Every 6 months
Every 3,000 treatment sessions
Every 12 months
ANSWER: 4. Every 12 months
Based upon a major manufacturer's service schedule, annual inspection and preventative maintenance by a professional HBOT chamber service company or the service department of the manufacturer should be performed. (Workman, W.T., Hyperbaric Facility Safety: A Practical Guide, Best Publishing, 1999, Page 471)
Many veterinary patients are receiving extensive and sophisticated dental care. The following question concerns HBOT and dentistry.
Which of the following statements is true?
Marked periodontal disease is a contraindication for HBOT.
A cracked premolar will likely have increased discomfort during an HBOT session.
Teeth with cavities (caries) will likely have increased discomfort during an HBOT session.
Air trapped between a dental filling (restoration) and the pulp may cause tooth pain during compression or decompression during an HBOT session.
ANSWER: 4. Air trapped between a dental filling (restoration) and the pulp may cause tooth pain during compression or decompression during an HBOT session.
Air trapped between a filling and the pulp in a dental restoration can create tooth pain during compression or decompression, as the air "bubble" shrinks during compression and then expands back to it's original size during decompression. This is a practical example of Boyle's Law as it applies to clinical HBOT. The filling must be replaced if this is suspected and the HBOT sessions are to be continued. (Kindwall and Whelan, Hyperbaric Medicine Practice, Second Edition Revised, 2004, Best Publishing, Page 94).
A controlled study in people with chronic periodontal disease demonstrated that HBOT in conjunction with scaling and root planing (SRP) was significantly more effective than SRP alone in the reduction of gingival bacterial pathogens and improvement in gingival health scores (Signoretto et al, Microbiological Evaluation of the Effects of Hyperbaric Oxygen on Periodontal Disease), New Microbiol. 2007 Oct: 30[4]: 431-7)
A 7 year old MN Greyhound is referred to you with leukocytosis, thrombocytopenia, fever, and increasing bilirubin.
He maintains a normal and steady PCV. You suspect sepsis. The fever is controlled with IV fluids and antibiotics. You want to add adjuvant HBOT. You review the thoracic radiographs (right).
Will you add HBOT?
Yes or no? Why?
ANSWER: No. The radiographs reveal pulmonary bullae. This patient is at risk for rupture of the bullae at pressure, and tension pneumothorax could subsequently develop while in the chamber. During decompression free air in thorax would actually further expand in volume, resulting in more serious pulmonary atelectasis. (References: Kindall, E.P., Whelan, H.T., Hyperbaric Medical Practice, Second Edition Revised, Best Publishing, 2004, Page 492: Steenblock, D.A., Hyperbaric Oxygen for Treatment of Stroke and Traumatic Brain Injuries, National Stroke Association Conference, Boston, MA, 1997).
A young canine is referred after a cardiopulmonary arrest/resuscitation and an iliac saddle thrombus. You are completing caudal abdominal ultrasound exam (immediately prior to a scheduled HBOT session) when the technician arrives to take the patient directly to the chamber.
Describe how to prepare the patient in this situation for a safe HBOT session:
ANSWER: Some brands of ultrasound gel have propylene glycol and ethanol compounds in their ingredients. Most ultrasonographers use alcohol to prepare the coat and skin for ideal contact with the probe. These substances all support combustion, and are not allowed in the chamber. The patient should be washed with a gentle soap and water solution, and wiped with a 100% cotton towel prior to the treatment session. This is especially important to remember in this situation where the session immediately follows the ultrasound exam.
You have been referred a canine patient for adjuvant HBOT in the treatment of acute "Bell's Palsy.” The patient had an extensive diagnostic work up by a veterinary neurologist which revealed no evidence for an underlying cause for the clinical signs. The client is a donor to your hospital, and devoted to her pet. The daily HBOT treatments will be done as an outpatient.
The head of the hospital lets you know how important this client is to the practice. For the first session the client brings a special 100% cotton "Snuggie" with her to place in the chamber and "keep her dog warm." She states that "her dog always lays on this Snuggie". She gives it directly to the technician who will be attending the treatment. The technician finds a body warmer packet (typically used in cold weather sports) heating up in a pocket in the "Snuggie."
What are the issues and how will you handle this?
ANSWER: The technician did an excellent job in preparing the patient for a safe treatment session. The overwhelming majority of chamber fires in the world (rare, but devastating) have occurred as the result of prohibited items in the chamber or incomplete preparation of the patient. In this case, the chemical body warmer is a prohibited item, as these devices have been known to be associated with chamber combustion (Raleigh, G. et al, Undersea & Hyperbaric Medical Society Website Online Safety Article, "Air Activated Chemical Warming Devices: Effects of Oxygen and Pressure"). Investigations into adverse events during HBOT have revealed situations where household members have unwittingly enabled the introduction of prohibited items into the chamber while trying to "enhance" the comfort of their family member.
In the article published in Undersea Hyperb Med, 1997:24[1]:35-8, Racic et al studied a randomized group of 79 human patients, and concluded that HBOT was more effective than prednisone in the treatment of Bell's Palsy.
A two month old toy breed puppy was presented HBC, and scheduled in the same day for HBOT to treat a traumatic brain injury. Which of these diagnostic procedures is not absolutely indicated before the treatment session?
Rectal temperature just prior to HBOT treatment
Chest X-rays
Spinal X-rays
Blood glucose just prior to HBOT treatment
Neurologic examination
ANSWER: 3. Spinal X-rays
These are not absolutely necessary prior to this treatment session. All patients must have a rectal temperature just prior to each session to reduce the potential for oxygen toxicity. The puppy was hit by a car, and chest X-rays are required to rule out untreated pneumothorax (a contraindication for HBOT). This toy breed puppy with trauma and head injury has probably not been eating as usual (and therefore at risk for hypoglycemia), consequently a blood glucose determination is vital prior to the treatment session. A neurologic examination is indicated in a patient with traumatic brain injury to determine the progression or regression of neurologic status.
Rockswold, Rockswold, et al (J Neurosurg. 2010 May; 112(5): 1080-94) employed a prospective, randomized clinical trial in human patients with severe traumatic brain injury. They found that hyperbaric oxygen therapy at 1.5 ATA significantly reduced intracranial pressure and increased cerebral blood flow/brain tissue oxygen levels compared to control groups. The clinician may consider adjuvant HBOT as well as drug therapy (e.g. hypertonic saline, mannitol) for TBI.
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