Hyperbaric Therapy in Blood Loss Anemia

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Continuing Education Activity

Red blood cells contain hemoglobin, the primary carrier of oxygen throughout the human body. When hemoglobin levels decrease, anemia results and patients may exhibit signs and symptoms of decreased oxygen delivery to tissues (also known as oxygen debt). The signs and symptoms of oxygen debt may include tachycardia, dyspnea, fatigue, chest pain, and altered mental status. Laboratory findings may include metabolic acidosis, hyperlactatemia, and elevated cardiac enzymes. Transfusion of packed red blood cells is administered to anemic patients who are symptomatic to relieve the signs and symptoms of oxygen debt. However, some patients are unable to receive blood transfusions due to religious beliefs or medical reasons. In these patient populations, hyperbaric oxygen therapy can be administered to increase oxygen delivery to tissues and relieve the signs and symptoms of oxygen debt. This activity highlights the interprofessional team's role in managing patients with anemia who refuse blood transfusions.


  • Review reasons why some patients cannot accept blood transfusions.
  • Summarize the use of hyperbaric oxygen therapy for anemic patients.
  • Describe the adverse effects of hyperbaric oxygen treatments.
  • Explain modalities to improve care coordination among interprofessional team members to improve outcomes for patients affected by anemia.


Red blood cells contain hemoglobin, the primary carrier of oxygen throughout the human body. When hemoglobin levels decrease, anemia results, and patients may exhibit signs and symptoms of reduced oxygen delivery to tissues (also known as oxygen debt).[1] The signs and symptoms of oxygen debt may include tachycardia, dyspnea, fatigue, chest pain, and altered mental status. Laboratory findings may include metabolic acidosis, hyperlactatemia, and elevated cardiac enzymes. Transfusion of packed red blood cells is administered to anemic patients who are symptomatic to relieve the signs and symptoms of oxygen debt. However, some patients cannot receive blood transfusions due to religious beliefs or medical reasons such as massive autoimmune hemolysis.[1] In these patient populations, hyperbaric oxygen therapy can increase oxygen delivery to tissues and relieve the signs and symptoms of oxygen debt.


According to the Jehovah’s Witnesses religion, portions of the Bible (including Genesis, Leviticus, and Acts) state that its followers must abstain from receiving blood.[2] Jehovah’s Witnesses will not accept blood transfusions, and this religious belief has been upheld in the American legal system.[2]

Other patients are unable to accept blood products due to medical reasons. Examples include patients with hemolysis and antibody formation due to transfusion reactions or those with crossmatch incompatibility. 

Patients who cannot accept blood transfusions for medical or religious purposes are at increased risk of morbidity and death after acute and unexpected blood loss from conditions including postpartum bleeding, trauma, and intraoperative hemorrhage.


Up to 1000 Jehovah's Witnesses die each year in part because they refuse to accept a blood transfusion.[2] Anemic patients who are elderly, obese, on hemodialysis, or have underlying heart disease are at increased risk for mortality.


Hyperbaric oxygen therapy is delivered in a hyperbaric (pressure) chamber with the patient breathing 100% oxygen at a pressure greater than 1.0 atmosphere absolute (ATA). Typically 2-3 ATA is used. Beyond 3 ATA, there are issues with oxygen toxicity.   

The amount of oxygen delivered to the body (DO2) is dependent on the arterial oxygen content (CaO2) and cardiac index (CI). The equation representing this is as follows:

  • DO2 = CaO2 x CI

The arterial oxygen content primarily depends on hemoglobin concentration; each hemoglobin molecule can carry up to 1.38 ml of oxygen per gram of hemoglobin.[3] A tiny amount of the arterial oxygen supply is dissolved in the plasma and depends on the partial pressure of oxygen in the blood (PaO2). The following equation represents the arterial oxygen content:

  • CaO2= (Hemoglobin [g/dL] x 1.38 ml O2 x %oxygen saturation) + (0.003 x PaO2)

The oxygen delivered to tissues is then extracted and used by the tissues. On average, the human body extracts 5% to 6% volume of oxygen from the blood.[3] As long as the oxygen supply equals or exceeds the amount of extracted oxygen, symptoms of oxygen debt do not occur. In anemic patients, oxygen delivery via hemoglobin may not be sufficient to compensate for oxygen extraction. When hemoglobin concentrations drop below 6 g/dL, oxygen delivery, and extraction become unequal, and when hemoglobin concentrations fall below 4 g/dL, tissue oxygenation delivery is significantly impaired.[2]

In 1959, the Dutch surgeon Boerema published “Life Without Blood,” a manuscript detailing the use of hyperbaric oxygen therapy (HBO) for treating anemia.[4] Boerema exsanguinated healthy piglets and replaced the blood volume with a plasma-like solution. The piglets’ resulting hemoglobin concentration was 0.4 g/dL, which is incompatible with life. The piglets were then pressurized in a hyperbaric chamber to 3 absolute atmospheres (ATA) for 45 minutes. The animals survived this exposure, despite having essentially no hemoglobin present and recovered uneventfully after they were re-infused with normal blood. Boerema noted that under hyperbaric conditions, the amount of oxygen dissolved in the plasma could significantly exceed the amount present while breathing air under normobaric conditions. This phenomenon is due to Henry’s Law, which states that the amount of gas dissolved in a solution is directly proportional to the partial pressure of the gas. When partial pressures of a gas increase, such as under hyperbaric pressurization, more of that gas dissolves in solution. Breathing room air (21% oxygen) under normobaric conditions results in a PaO2 of approximately 100 mmHg; breathing 100% oxygen under hyperbaric conditions results in a PaO2 greater than 2000 mmHg. Under hyperbaric conditions, oxygen dissolved in the plasma can approximate or meet the body’s metabolic demands of oxygen extraction.[5] At a treatment depth of 3 ATA, the plasma dissolved oxygen approximates 6% volume, equal to the body’s oxygen extraction.[6]

History and Physical

Anemia can present with a wide range of signs and symptoms. For example, anemic patients may be light-headed, confused, weak, fatigued, irritable, and have headaches, decreased exercise tolerance, palpitations, or dyspnea. Generally, symptoms do not occur until the hemoglobin level drops to less than 7 g/dL.  

The most common systems involved in hemorrhage are the gastrointestinal, genitourinary, and pulmonary systems. Therefore, menstrual history in women should be explored, as well as asking about hematemesis, hemoptysis, hematuria, hematochezia, and melena.

A thorough past medical history should include the following:

  • Medications such as aspirin, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, bisphosphonates,carbamazepine, cephalosporins, nonsteroidal anti-inflammatory drugs, phenytoin, sulfa drugs, and chemotherapy agents
  • Supplements such as iron, folate, and B12,
  • Family history such as Sickle cell anemia, glucose-6-phosphate deficiency, spherocytosis

On exam, signs of acute blood loss associated with emergent anemia can include hemodynamic abnormalities such as hypotension, tachycardia, and tachypnea. In addition, the patient may experience decreased urine output, increased thirst, and altered mental status. These clinical manifestations depend on factors such as patient comorbidities, age, baseline medications, and severity of illness or injury. For example, younger adults may be able to compensate with an increased heart rate. However, older patients with baseline medical problems are more commonly unable to compensate. This may be especially true if they are chronically on beta-blockers. The examination is often normal in patients with chronic anemia, although several findings suggest specific causes. Pallor, scleral icterus, and jaundice are associated with hemolytic anemia.

In addition, physicians should assess for evidence of cardiac murmur, crackles, hepatomegaly or splenomegaly, thyromegaly, and lymphadenopathy. On rectal examination, evaluation for tenderness, joint deformities, rashes, and melena or blood is essential. Evidence of bleeding with chronic anemia suggests a coagulation disorder. As discussed, patients can adapt to low hemoglobin levels, such as 5 to 6 g/dL, if anemia is slow in onset.


Patient evaluation should focus on signs and symptoms of decreased oxygen delivery to tissues. Vital signs may show tachycardia and hypotension. The patient’s mental status may be altered; cerebral infarcts may occur secondary to decreased oxygen delivery to the brain. Ischemic changes may be present on electrocardiography, and decreased urine output may be due to hypoperfusion. Laboratory studies may reveal metabolic acidosis, abnormal cardiac enzymes, or a base deficit.

Treatment / Management

The physiologic effects of hyperbaric oxygen therapy in anemic patients are short-lived; the elevated tissue partial pressures of oxygen last only minutes to hours after each hyperbaric exposure.[5] The frequency of hyperbaric oxygen therapy should be tailored to the patient’s clinical status.[7] More symptomatic patients may require treatments administered two or three times daily.  Typically treatments are at 2 to 3 ATA for 3 to 4 hours 3 or 4 times daily.  Volume status should be maintained, as well as nutritional support, folic acid, vitamin B, iron, and other hematinics.[8]

Treatments can be administered in a monoplace (holding a single person) or multiplace (accommodating multiple people) hyperbaric chamber.  Treatment depths depend on the individual hyperbaric unit’s clinical procedures.  Still, increased treatment depths will result in higher partial pressures of oxygen and likely increase relief of the symptoms of oxygen debt.  Other modalities which can reduce oxygen consumption, including sedation, neuromuscular paralysis, and cooling, can also be utilized as adjunctive therapy.[9] Blood should be minimized whenever possible; pediatric tubes can be used for phlebotomy to reduce unnecessary blood loss.[9] Consultation with a bloodless medicine specialist for recommendations for using iron supplementation and erythropoietin may also be considered.

Differential Diagnosis

Differentials include the following conditions:

  • Alpha thalassemia
  • Aplastic anemia
  • Beta thalassemia
  • Hemolytic anemia
  • Iron deficiency anemia
  • Low LDL cholesterol
  • Megaloblastic anemia
  • Myelophthisic anemia
  • Pernicious anemia
  • Sickle cell anemia
  • Spur cell anemia


Several case reports and series support HBO's efficacy and other "bloodless" modalities for acute and chronic blood loss anemias.[10][11][12][13]


Mild middle ear barotrauma is not uncommon.  Serious complications of HBO are rare.[14] These include:

  • Eustachian tube dysfunction
  • Tympanic membrane rupture
  • Oxygen toxicity
  • Ear, sinus, or tooth pain
  • Decompression sickness
  • Pneumothorax
  • Arterial gas embolism
  • Nitrogen emboli to the central nervous system, lung, or joints
  • Middle ear hemorrhage
  • Deafness
  • Changes in vision
  • Certain types of hemolytic anemia
  • Fire hazard
  • Nausea, fatigue, malaise
  • Claustrophobia
  • Equipment malfunction 


Other specialists need to be involved regarding the cessation of blood loss, whether from bleeding, hemolysis, or failure of production. Reported adjunctive therapies include PEGylated carboxyhemoglobin bovine, hemoglobin-based oxygen carriers, erythropoietin, steroids, and hematinics such as iron, folate, and B12/cyanocobalamin.[13][8][12][11]

Many hospitals have Hospital Liaison Committees (HLC). These can utilize community-based volunteer Jehovah’s Witness clergy that assist hospitalized Jehovah’s Witnesses. These volunteers visit patients, help coordinate care plans that reflect the spiritual beliefs of the patients, and advocate for such patients in a nonconfrontational fashion.[12]   

Deterrence and Patient Education

"The refusal of transfusion is not equivalent to refusing medical treatment, and numerous options are available to manage care without transfusions effectively."  Bloodless Medicine and Surgery use concepts and techniques to decrease blood loss, tolerate anemia, correct deficiencies, and otherwise manage patients without transfusions for anemia.[15]

Pearls and Other Issues

Hyperbaric oxygen therapy is generally well tolerated, and most side effects can be minimized by careful patient preparation and planning. The most common adverse event associated with hyperbaric oxygen therapy is middle ear barotrauma, which manifests as pain or pressure in the ears during chamber compression or decompression. Slow compression, pressure reduction maneuvers (such as the Valsalva maneuver), and prophylactic administration of decongestants (such as pseudoephedrine) can reduce the risk of ear barotrauma. Sinus, dental, and pulmonary barotraumas may also occur but are rarely encountered in clinical practice. Patients should avoid holding their breath during chamber ascent to reduce the risk of pulmonary barotrauma.

Oxygen toxicity seizures are rare and may be minimized using scheduled air breaks. Pulmonary oxygen toxicity is rare and may be minimized by maintaining well-defined intervals of several hours between each hyperbaric treatment. Patients with diabetes may experience hypoglycemia during hyperbaric treatments, and patients with a history of claustrophobia may experience confinement anxiety.

Enhancing Healthcare Team Outcomes

Awareness of HBO for blood loss anemia is low, as is access to capable HBO facilities.[16] Increased awareness and a willingness to transfer to an HBO-capable site can benefit anemic patients who refuse blood transfusions. They can be managed by an interprofessional team that includes clinicians, nurse practitioners and physician assistants, respiratory therapists, hyperbaric technicians, hematologists, nurses, and pharmacists. Patients should be educated that there is a potential for death without blood. Some patients may benefit from HBO therapy, but this requires multiple sessions. However, the treatment is relatively safe and cost-effective, comparable in cost with a unit of packed red cells.[8] {harmcists can provide medication reconciliation and monitor the dosing of hematinic agents, which nurses will usually administer.

Often a patient wishing for treatment without blood transfusion is looked upon askance and may be marginalized. Physicians may feel compelled to offer suboptimal care, which may add to the ethical issues and risks. A multidisciplinary and patient-centered approach to care results in more favorable medical and psychological outcomes for the patients and their care teams.[12]



2/13/2023 8:45:04 PM



A systematic review of the application of hyperbaric oxygen in the treatment of severe anemia: an evidence-based approach., Van Meter KW,, Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc, 2005 Jan-Feb     [PubMed PMID: 15796315]

Level 1 (high-level) evidence


Management of the Jehovah's Witness in Obstetrics and Gynecology: A Comprehensive Medical, Ethical, and Legal Approach., Zeybek B,Childress AM,Kilic GS,Phelps JY,Pacheco LD,Carter MA,Borahay MA,, Obstetrical & gynecological survey, 2016 Aug     [PubMed PMID: 27526872]

Level 2 (mid-level) evidence


Van Meter KW, The effect of hyperbaric oxygen on severe anemia. Undersea     [PubMed PMID: 23045922]


BOEREMA I,MEYNE NG,BRUMMELKAMP WH,BOUMA S,MENSCH MH,KAMERMANS F,STERN HANF M,van AALDEREN, [Life without blood]. Nederlands tijdschrift voor geneeskunde. 1960 May 7;     [PubMed PMID: 13802034]


Greensmith JE, Hyperbaric oxygen reverses organ dysfunction in severe anemia. Anesthesiology. 2000 Oct;     [PubMed PMID: 11020776]


McLoughlin PL,Cope TM,Harrison JC, Hyperbaric oxygen therapy in the management of severe acute anaemia in a Jehovah's witness. Anaesthesia. 1999 Sep;     [PubMed PMID: 10460565]


Graffeo C,Dishong W, Severe blood loss anemia in a Jehovah's Witness treated with adjunctive hyperbaric oxygen therapy. The American journal of emergency medicine. 2013 Apr;     [PubMed PMID: 23380087]


Long B,Koyfman A, Emergency Medicine Evaluation and Management of Anemia. Emergency medicine clinics of North America. 2018 Aug;     [PubMed PMID: 30037447]


Gutierrez G,Brotherton J, Management of severe anemia secondary to menorrhagia in a Jehovah's Witness: a case report and treatment algorithm. American journal of obstetrics and gynecology. 2011 Aug;     [PubMed PMID: 21457912]

Level 3 (low-level) evidence


Johnson-Arbor K,Verstraete R, Use of hyperbaric oxygenation as an adjunctive treatment for severe pernicious anaemia in a bloodless medicine patient. BMJ case reports. 2021 Apr 12;     [PubMed PMID: 33846184]

Level 3 (low-level) evidence


Zumberg M,Gorlin J,Griffiths EA,Schwartz G,Fletcher BS,Walsh K,Dao KH,Vansandt A,Lynn M,Shander A, A case study of 10 patients administered HBOC-201 in high doses over a prolonged period: outcomes during severe anemia when transfusion is not an option. Transfusion. 2020 May;     [PubMed PMID: 32358832]

Level 3 (low-level) evidence


Johnson-Arbor K,Verstraete R, No Bad Blood-Surviving Severe Anemia Without Transfusion. JAMA internal medicine. 2021 Jan 1;     [PubMed PMID: 33226407]


Thenuwara K,Thomas J,Ibsen M,Ituk U,Choi K,Nickel E,Goodheart MJ, Use of hyperbaric oxygen therapy and PEGylated carboxyhemoglobin bovine in a Jehovah's Witness with life-threatening anemia following postpartum hemorrhage. International journal of obstetric anesthesia. 2017 Feb;     [PubMed PMID: 27890467]


Foster JH, Hyperbaric oxygen therapy: contraindications and complications. Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons. 1992 Oct;     [PubMed PMID: 1356147]


Shander A,Javidroozi M, The approach to patients with bleeding disorders who do not accept blood-derived products. Seminars in thrombosis and hemostasis. 2013 Mar;     [PubMed PMID: 23397555]


Leung JK,Lam RP, Hyperbaric oxygen therapy: its use in medical emergencies and its development in Hong Kong. Hong Kong medical journal = Xianggang yi xue za zhi. 2018 Apr;     [PubMed PMID: 29658485]