HBOT Safety/Review Questions
The following are examples of patients you might treat with adjuvant hyperbaric oxygen therapy. Select the one who would be most likely to have a seizure during a one hour session at 1.5 or 2.0 ATA.
a male neutered feline with a non-healing axillary ("pocket") wound.
a female spayed Cocker Spaniel with immune mediated hemolytic anemia.
a female spayed mixed breed bitten by a pit viper.
a male neutered Boxer with a medically managed insulin producing tumor who has developed acute, severe, effusive pancreatitis.
ANSWER: 4, a male neutered Boxer with a medically managed insulin producing tumor who has developed acute, severe, effusive pancreatitis.
HBOT is an important therapeutic tool in the management of pancreatitis, and should be considered in this case (a discussion with references can be found here.). However, one must remember that HBOT potentiates the effects of insulin, and it is essential to monitor blood glucose, pre and post HBOT, in a case like this. If your patient has a low blood glucose prior to a scheduled treatment, therapeutic intervention and postponement of the HBOT session are indicated. It should be noted that patients with diabetes mellitus on insulin therapy should also have their blood glucose monitored prior to therapy. A general guideline is to reduce the insulin dose just prior to a session by approximately 25%. It is common for a canine or feline with diabetes mellitus to develop a reduced insulin requirement after a series of HBOT sessions.
You are evaluating an 8 year old feline with a known historical diagnosis of hypertrophic cardiomyopathy.
The cat has been medically managed by a cardiologist, and appears stable on your initial cardiopulmonary assessment. It was presented for an acute gait disturbance (onset less than 8 hours prior to presentation) of a single forelimb. You note that the involved leg is cool to the touch, and a toenail bleeds inappropriately slow when cut to the vascular level.
Color Doppler Ultrasound exam demonstrates that blood flow to the distal affected limb is subjectively reduced, but still present. Sensation is intact to the distal limb. You decide that there has been a thromboembolic event in the brachial artery, likely associated with the underlying cardiomyopathy.
Your intent is to lessen the impact of ischemia/reperfusion injury and act to reduce the potential further development of the thrombus. You decide to start anti-platelet therapy with low dose aspirin while awaiting the attending cardiologist's consultation. In an ICU rounds discussion you suggest adjuvant HBOT therapy to increase oxygen delivery to the hypoxic tissues of the forelimb and enhance pain control. Your colleague worries that HBOT may exacerbate ischemia/reperfusion syndrome.
Is the following statement True or False?
A recent study demonstrates that hyperbaric oxygen therapy actually inhibits ischemia/reperfusion injury by inhibiting neutrophil adherence to endothelia.
ANSWER: True
One of the studies documenting the effect of HBOT on the ischemia - reperfusion syndrome was published by Jones et al in Plastic & Reconstructive Surgery, August 2010, Volume 126, Issue 2, pp 403-411, "Hyperbaric Oxygen Inhibits Ischemia - Reperfusion - Induced Neutrophil CD18 Polarization by a Nitric Oxide Mechanism". The study supports previous studies affirming that HBOT inhibits neutrophil adhesion to endothelial membranes, thus opposing the pathological progression of the Ischemia -Reperfusion Syndrome.
You are treating two young Jack Russell Terriers (from the same litter) living with the same family. They are both bitten in the face by a rattlesnake. The patients were treated with antivenin, then referred, at the owner's request, for adjuvant hyperbaric oxygen therapy. They arrive at your hospital in one transport kennel, with the owners reporting they are inseparable. Since the two housemates get along so well you consider putting them into the chamber together to expedite their treatment.
Please discuss the safety issues involved and how you might manage this situation.
ANSWER: It is never permitted to treat multiple patients at the same time in a situation where they might have contact with each other during an HBOT session. This would create opportunities for static electricity discharge between the patients, especially in conditions of dry humidity. In addition, the risk of injury caused by unforeseen physical conflict during a session is not acceptable. The options include treating these two patients in separate sessions, or treating them together using individual polycarbonate treatment modules to achieve separation and safety during HBOT. Do not use cages inside the HBOT chamber that have metal parts which may scrape against each other and create a spark.
You are performing HBOT on a canine HBC patient with multiple injuries, including traumatic brain injury and crushing injuries to the laryngeal area. The patient is stable and breathing spontaneously through a tracheostomy site. Which of the following medical devices would not be allowed in the chamber during a session with this patient?
A chest drain with a Heimlich valve
A soft rubber Penrose drain
A urinary catheter emptying into a sterile rubber glove
A tracheostomy tube with the cuff inflated by air
All of the above
ANSWER: D. A tracheostomy tube with the cuff inflated by air
Boyle's Law states that for a body of ideal gas at constant temperature, the volume is inversely proportional to the pressure. Therefore, compressing the air in a cuff to twice its original absolute pressure (e.g. 2 ATA) will halve its volume. Thus, the cuff inflated by air will reduce in volume and diameter to a much smaller size, and the tube could shift position or even fall out, with the potential for loss of a patent airway. You may prevent this from happening by using sterile saline to inflate the tube cuff (Reference: Larson-Lohr and Norvell, Hyperbaric Nursing, Best Publishing, 2002, pgs. 206-7).
A veterinary hyperbaric technician is monitoring a canine patient being treated for Immune Mediated Hemolytic Anemia [IMHA] in a monoplace chamber. Which one of these situations calls for an early end to the treatment session?
The hair on the patients ears and nose is beginning to stand straight up and out.
The patient is licking repeatedly at his forepaws.
The cotton bandage on his paw is starting to unravel.
The patient vomits his morning meal.
ANSWER: 1
This rare situation of excessive static formation requires standard, gradual decompression and an early end to the session, as static buildup could lead to a spark, with increased risk of combustion. Static buildup can be minimized by gently wiping down the haircoat of the patient with a moistened, 100% cotton towel prior to the session.
Treatment with HBOT is valuable in IMHA, as it allows delivery of oxygen to systemically hypoxic tissues, and helps rapidly lower carbon monoxide (CO) levels, which are a by-product of Heme Catabolism. This endogenously produced CO binds to remaining RBCS, causing reduction in RBC deformability, and shifts the oxygen dissociation curve to the left. CO induces increased platelet aggregation. In addition, CO combines with myoglobin, cytochrome c-oxidase and cytochrome P-450, which may inhibit the mitochondrial respiratory chain. An evidence-based approach review of peer reviewed publications concluded that all articles reported a positive result when HBOT is given for treatment of severe anemia in humans. Van Meter KW, Undersea Hyperb Med 2005 Jan-Feb; 32 (1) 61-83
The inside and outside of the plexiglass on a hyperbaric chamber should be thoroughly cleaned with spray window cleaner or alcohol wipes on a regular basis. True or false?
ANSWER: False
You are about to treat a feline with acute, exceptional anemia of unknown origin in the hyperbaric oxygen chamber while cross matching to a blood donor. The patient and client are new to you and the hospital, and have arrived as an emergency referral with pale, white, mucous membranes and marked lethargy. The owner is quite stressed, and reluctant to let the pet leave her arms. She wants you to allow something to go in the chamber with the cat to make it feel more comfortable. She has several items with her as options. Which of the following is acceptable?
A cell phone so the owner can talk to the cat
A nylon toy
A plastic toy with a metal bell
A GPS collar so the owner can track her cat's movements and position from her cell phone
None of the above
ANSWER: None of the above.
Of course, the cell phone and the GPS device are electronic and have batteries. They are not allowed in the chamber as they may initiate a spark or develop an overheated battery. The nylon toy and the plastic toy with a metal ball have a higher tendency to create static electricity (or a spark) than a 100% cotton toy, so they are not acceptable in the chamber. Safe practice is to (diplomatically) disallow any owner-supplied items to accompany the patient into the chamber. Use only the 100% cotton towels that are purchased and supplied by your own hospital. (Reference, Larson-Lohr, Norvell, Hyperbaric Nursing, Best Publishing, 2002, Page 250).
You are administering BID HBOT (as an outpatient) to a young male canine hunting dog. This patient developed an acute coccygeal neuropathy associated with prolonged extreme exercise and experienced nearly complete loss of tail movement and tone. The weather is warm and wet, and the mosquitos are swarming. As you admit the dog in the morning you ask the owner if there are any new medications or treatments the dog is receiving. The owner answers, "No, but I had to spray mosquito repellent all over him and me just so we could survive the morning walk!"
What is the significance of this statement in regards to the planned HBOT session and how do you handle the situation?
ANSWER: Most of the major mosquito repellent sprays are primarily alcohol-based, thus supporting combustion. This patient should have a thorough and complete bath prior to the HBOT session. The attending doctor and hyperbaric technician should be aware of topical products being used by owners or by staff in the treatment and/or grooming of HBOT patients. Alcohol or petroleum-based products are common, and both must be avoided or removed from the patient coat prior to HBOT. Other examples of alcohol-based products include many brands of 'finishing' or 'holding' grooming hair sprays.
Which of the following items are allowed in the Hyperbaric Oxygen Chamber during a treatment session?
An IV catheter wrapped in 100% cotton cast padding and secured with cotton tape.
A gastric feeding tube protected by a 100% cotton tube stockinette.
An external fixator wrapped in 100% cotton cast padding.
A fiberglass cast covered by a 100% cotton stockinette.
All of the above.
ANSWER: 5. All of the above.
The National Fire Protection Association (NFPA) established criteria for safe practices in health care facilities. NFPA-99 Chapter 20 specifies that 100% cotton is an approved anti-static material for use in Hyperbaric Oxygen Chambers. It is imperative that other materials used in patient bandaging be covered with 100% cotton inside the chamber. Metal external fixators must be heavily padded and completely covered in 100% cotton to prevent metal to metal contact and spark generation.
It is also important that when more than one patient is receiving HBOT simultaneously in the same chamber, the patients must be kept separated in individual non-metallic "treatment modules" to prevent static electricity discharges or dangerous interactive contact between patients.
An adult F/S feline was rescued from a house fire and presented as an emergency with significant thermal burns, respiratory distress (with generalized pulmonary alveolar infiltrates on radiographs), and weakness. You consider the possibility of carbon monoxide (CO) toxicity in addition to the other indications for adjuvant HBOT. It is estimated that over 50% of the deaths in fires are the result of CO toxicity. (Reference Jain K.K., Textbook of Hyperbaric Medicine, 5th Edition, Pages 112-129)
Hyperbaric Oxygen Therapy is an accepted and "Coded" treatment for CO toxicity in human medicine, and third party payers will generally reimburse HBOT treatment expenses for this condition. HBOT reduces the half life of blood CO from greater than 5 hours to less than 25 minutes and supplies enough oxygen via the plasma to sustain life while CO levels dissipate.
Would you expect neurologic signs of CO toxicity to occur:
immediately on exposure?
days to weeks after exposure?
ANSWER: The correct answer may be both 1 and 2. In humans, two neurologic syndromes are observed after carbon monoxide exposure: Acute and Delayed Neurologic Syndromes. (Reference Zhang, J.H., Hyperbaric Oxygen For Neurological Disorders, Best Publishing; 2008, Pgs 377-393)
The Acute Syndrome is the result of hypoxia, CO binding to myoglobin, hemoglobin, mitochondrial cytochrome compounds, and the development of cerebral edema and necrosis.
The Delayed (Chronic) Syndrome is an immune mediated response, and a 2006 paper by Thom et al demonstrated HBOT's beneficial effect in this syndrome (Hyperbaric Oxygen Reduces Delayed Immune-Mediated Neuropathology in Experimental Carbon Monoxide Toxicity).
The following is a contraindication to Hyperbaric Oxygen Therapy:
A cat with pyothorax.
A dog with a marked pulmonary alveolar pattern on radiographs after biting an electric cord.
A cat with pulmonary injury and cutaneous burns as the result of a house fire.
A canine with untreated tension pneumothorax subsequent to being hit by a car.
ANSWER: 4. A canine with untreated tension pneumothorax subsequent to being hit by a car.
Untreated pneumothorax is a contraindication for HBOT therapy. The clinical significance follows: if the pneumothorax progresses during the HBOT, as the patient is decompressing (at the end of the treatment session) the volume of the free air trapped in the thorax will expand, and thus further collapse the lungs and compromise respiration (Reference Kindall and Whelan, Hyperbaric Medical Practice Best Publishing 2004, page 86). If a patient with a chest tube is being treated, it is advisable to check radiographs and connections/plugs immediately prior to a session. Ensure that this patient does not have a recent history of significant amounts of air being found and removed from the thorax during the regular "tube checks".
Patients with a history of trauma should have thoracic radiographs prior to HBOT in order to rule out pneumothorax. Patients with known pulmonary bullae, tracheal tears, pneumomediastinum, or a history of spontaneous pneumothorax may not be ideal patients for HBOT, as these conditions have the potential for rapid progression to pneumothorax at any time.
A canine referred to your hospital (and diagnosed as severe pancreatitis) is being treated with adjuvant HBOT. The rectal temperature has been variably elevated over the past 48 hours since admission. Just prior to this morning's session the attending technician comes to you and states that the rectal temperature is 104.2 degrees F. The dog has clinically improved each day during hospitalization, and you want to continue HBOT, but are concerned about this temperature spike and its implications. Please discuss your options regarding HBOT and your decision-making process in this situation.
ANSWER: Of course, you want to examine the patient for alternative reasons for fever, including sepsis, infectious diseases, IV catheter associated phlebitis, abscess, etc. You may wish to repeat abdominal ultrasound examination and blood/urine tests. However, this patient is progressively improving clinically, so you may be inclined to continue adjuvant HBOT as well.
Fever (or hyperthermia of other origin) increases uptake of oxygen by body tissues, and thus increases the risk of oxygen toxicity. The most common sign of oxygen toxicity recognizable in small animal hyperbaric oxygen therapy is a short generalized motor seizure. In this patient with a fever you may choose one or more of the following (with the consent of the attending clinician) prior to HBOT to reduce the risk of oxygen toxicity:
Administer a cool-down bath and check rectal temperature prior to therapy. In general, the upper limit of acceptable rectal temperature prior to HBOT is 103.5 degrees F in the canine or feline.
Check with the attending doctor to see if administration of an NSAID is compatible with the patient's clinical status and concurrent medications, and follow up rectal temperatures after treatment to see if the temperature drops into acceptable levels.
Administer an injection of a benzodiazapine such as diazepam which has anticonvulsant properties (again...only if the attending doctor concurs).
Reduce the treatment pressure to 1.5 ATA if appropriate, according to the clinical problem being treated.
In some cases you may choose instead to postpone HBOT indefinitely until the temperature returns to acceptable levels. Other substances which help protect against oxygen toxicity include phenothiazines, propranolol, and Vitamin E (Reference Jain, K.K., Textbook of Hyperbaric Medicine, 5th Edition, Hogrefe and Huber Publishers, 2009, page 84)
A 12-year-old Fes Schnauzer with a chronic history of Cushing's and diabetes mellitus is referred for adjuvant HBOT in the management of severe pancreatitis [which began shortly after she was observed eating garbage from the trash can].
At morning rounds you discussed pre-HBOT management in this patient. What adjustment do you have to make to this patient’s medications prior to an HBOT session?
ANSWER: Reduce the immediate pre-treatment insulin dosage by 33% of the usual dose.
The clinician should consider checking blood glucose measurements in Diabetics undergoing HBOT before and after treatment sessions to help decide how much the individual patient's blood glucose is affected by HBOT. In a study on human Diabetics, insulin dosages were reduced by significant amounts in over 60% of patients treated by HBOT. (Reference: Kakhnovski et al, Biochemical Indices in Diabetes Mellitus Patients Undergoing Hyperbaric Oxygenation. Sov Med 10: 33-37)
A 10 month old feline is being treated with HBOT for a non-healing axillary wound which had not responded to graft/flap surgery. The wound has been present for 7 months. Biopsies and cultures did not reveal etiologic agents (including Mycobacterium). The kitten has a short generalized seizure during HBOT at 2 ATA observed by the attending technician.
The technician should:
Press the Emergency Button and immediately/ rapidly decompress, then notify the attending doctor.
Initiate an immediate gradual decompression over 10-15 minutes to terminate the session, then contact the attending doctor.
Adjust the treatment pressure down to 1.5 ATA gradually, and promptly contact the attending doctor.
Notify the attending doctor, and begin to time the seizure. If the seizure is short (less than two minutes), start to reduce the pressure gradually down to 1.5 ATA.
ANSWER: 4.
Seizures are infrequently encountered during HBOT, and may be a sign of “oxygen toxicity”. They are usually short in duration, and without sequellae. They typically occur at a slightly greater frequency during higher ATA treatment pressures, such as 2.5 or 3 ATA. Most seizures observed in the chamber are short. If this is the case, wait until the seizure ends, then begin a gradual reduction in pressure to 1.5 ATA. Rapid decompression is NOT recommended as the expanding pulmonary gases during rapid decompression could theoretically rupture lung tissue during the tonic phase of the seizure. If the seizure ends quickly the treatment session may be completed at the reduced ATA if the patient appears stable. The attending doctor may consider giving future sessions at the reduced ATA, prescribing pre- treatment anticonvulsants such as benzodiazapines, or both.
Known epileptics or patients with CNS diseases at risk for seizures may receive HBOT, however the attending clinician should consider lower treatment pressures and/or pre-treatment anticonvulsants. [reference Kindwall, EP. Whelen HT, Hyperbaric Medicine Practice, Second Edition Revised, Best Publishing, 2004, page 77].
The attending doctor and technician should be aware that hypoglycemia may also occur in the chamber, and manifest as a seizure in some patients.
A 10-year-old canine was referred for possible adjuvant HBOT in the treatment of presumed pancreatitis. The patient is critically ill, and has multiple criteria supporting this diagnosis, including vomiting, lipemia, anterior abdominal pain, “strawberry milkshake” abdominal effusion with no evidence for infectious organisms, radiographic and ultrasonographic imaging typical for pancreatitis, and extremely elevated cPLI.
However, the patient has a history of malignant Mast Cell Tumor and is currently being treated with Palladia®.
The referring doctor asks you, “Is the presence of malignant neoplasia a contraindication for HBOT?” You answer:
Yes
No
ANSWER: 2. No
In light of HBOT's upregulation of Vasculogenesis, many clinicians express hypothetical concern that treating a cancer patient with HBOT will increase the rate of tumor growth or stimulate metastasis. This has NOT been observed in large numbers of humans treated with HBOT for radionecrosis (Reference, Kindwall, E.P. and Whelan, H.T., "Hyperbaric Medical Practice", Second Edition Revised, Best Publishing, 2004, pages 86-89)
A nude mice model implanted with human Squamous Cell Carcinoma showed no difference in tumor growth or metastasis between controls and HBOT treated subjects at six week follow up (Reference, Sklizovic, D. et al. "Hyperbaric Oxygen Therapy and Squamous Cell Carcinoma Growth", Head and Neck, 1993; 15 (3): 236-240)
A 3 year old pregnant female champion breeding bitch is presented to you on emergency with a fresh wound on the lower mandible and severe facial swelling. The owner witnessed a rattlesnake biting the dog as it sniffed around a large rock during a walk. The bitch is due to whelp in approximately two weeks. You want to use adjuvant HBOT in this patient, but are concerned about HBOT's effect on the feti, or premature closure of the fetal ductus arteriosi. Is HBOT contraindicated in pregnancy?
Yes
No
ANSWER: 2. No
There appears to be no established contraindication to treatment with HBOT in pregnancy. It takes prolonged exposure times, 12 consecutive hours or more, to result in closure of a ductus arteriosus. Likewise, the retrolental fibroplasia / retinopathy of neonatal humans associated with prolonged hyperoxemia has not been associated with the relatively short HBOT sessions.
Reviews of the human medical literature reported in Russia and the US have resulted in recommendations that HBOT can be used in pregnant females without harm to the fetuses or mothers [references Pobendinsky, NM et al “Hyperbaric Oxygen in the Treatment of Reproductive Function of Women” Proceedings of the Seventh International Congress on Hyperbaric Medicine. Van Hoesen, KB et al, “Should hyperbaric oxygen be used to treat the pregnant patient for acute carbon monoxide poisoning?" JAMA. 1989; 261[7]: 1039-1043]
Which of the following is allowed to be included with a feline patient inside the chamber or treatment module during an HBOT session?
A cell phone on speaker mode so the owner can speak to the cat during the treatment
A stuffed toy which jumps up and down when batted by the cat
An Ipod music player with speakers
A 100% cotton garment recently worn by the owner
ANSWER: 4. A 100% cotton garment recently worn by the owner. 100% cotton is allowed in the chamber. Electronic, battery operated, or wind-up devices would be a combustion hazard, and are not permitted in the chamber.
A veterinary hyperbaric technician is monitoring a canine patient being treated for Immune Mediated Hemolytic Anemia [IMHA] in a monoplace chamber. Which one of these situations calls for an early end to the treatment session?
The hair on the patients ears and nose is beginning to stand straight up and out.
The patient is licking repeatedly at his forepaws.
The cotton bandage on his paw is starting to unravel.
The patient vomits his morning meal.
ANSWER: 1. This rare situation of excessive static formation requires standard, gradual decompression and an early end to the session, as static buildup could lead to a spark, with increased risk of combustion. Static buildup can be minimized by gently wiping down the haircoat of the patient with a moistened, 100% cotton towel prior to the session.
Treatment with HBOT is valuable in IMHA, as it allows delivery of oxygen to systemically hypoxic tissues, and helps rapidly lower carbon monoxide (CO) levels, which are a by-product of Heme Catabolism. This endogenously produced CO binds to remaining RBCS, causing reduction in RBC deformability, and shifts the oxygen dissociation curve to the left. CO induces increased platelet aggregation. In addition, CO combines with myoglobin, cytochrome c-oxidase and cytochrome P-450, which may inhibit the mitochondrial respiratory chain. An evidence-based approach review of peer reviewed publications concluded that all articles reported a positive result when HBOT is given for treatment of severe anemia in humans.
Van Meter KW, Undersea Hyperb Med 2005 Jan-Feb; 32 (1) 61-83
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