Pulmonary Arterial Hypertension (PAH)


Pulmonary arterial hypertension (PAH) is a progressive disorder in which the arteries of the lungs present with high blood pressure. Symptoms of PAH include shortness of breath, chest pain, and fainting. Affected individuals may also have fainting episodes, hemoptysis, hoarseness, hypotension, and swelling of the face, ankles, or abdomen.1 PAH is a rare disease that is idiopathic or secondary to other conditions.2 Even though no cure is currently available, several treatments can be used to manage this disease. Treating PAH is important to avoid further damage to the heart, which may weaken over time due to higher strain on its right side as it tries to pump blood through stiff vessels.1,3 Untreated right ventricular failure can eventually lead to death.4

What is Oxygen Therapy?

Treatment of PAH can be based on supportive therapy, which includes the use of anticoagulants to prevent the formation of blood clots, diuretics to reduce fluid overload resulting from heart failure, and oxygen supplementation. Targeted therapies such as phosphodiesterase-5 inhibitors, calcium channel blockers, prostaglandins, soluble guanylate cyclase stimulators, and endothelin receptor antagonists can be also prescribed.5

Patients with PAH who experience low levels of oxygen may have a poor quality of life, and vital organs may be compromised if these levels are not corrected.6 Oxygen therapy can help patients increase and maintain the amount of oxygen in their blood and therefore reduce symptoms of fatigue and dyspnea while improving concentration.7 

Oxygen is a potent and selective pulmonary vasodilator that helps decrease high pressure in the pulmonary arteries.7-9 Evidence shows that the pulmonary vascular effects induced by supplemental oxygen are mediated by both alveolar and arterial mechanisms and that the alveolar endothelium is a relevant therapeutic target.8 Patients’ cardiopulmonary responses to oxygen administration may vary,10 however, the systemic effects in PAH appear to be reduced following supplementation.9 

Guidelines for Oxygen Supplementation

Current treatment guidelines do not recommend supplemental oxygen therapy in patients with PAH unless severe hypoxemia develops (arterial oxygen saturation <91%).11 This recommendation is based on a negative observation from a study in which patients with chronic obstructive pulmonary disease who developed severe hypoxemia were prescribed oxygen therapy.12 As severe hypoxemia is not always observed in PAH, further studies on supplemental oxygen therapy are needed to ascertain the impact of the treatment on these patients.

A recent study has reviewed the acute and chronic effects of oxygen on patients with PAH and highlighted the potential benefit of oxygen therapy in all patients with PAH, regardless of the development of severe hypoxemia. Eleven cohorts of patients, including patients without hypoxemia, from 9 studies were analyzed. In 10 cohorts of patients, the acute administration of oxygen for 15 to 30 minutes led to a reduction of the mean pulmonary arterial pressure (mPAP) by 5% to 15%. Pulmonary vascular resistance (PVR) was also decreased by 20% to 30%. This review has highlighted 5 studies in which oxygen was administered at home and at night. Four of these studies were performed close to sea level and revealed benefits in all major outcomes, such as survival rates after 2 to 5 years, 6-minute walk distance, and echocardiographic measurements.9

Using Oxygen Therapy

There are 2 types of supplemental oxygen, gaseous and liquid, and patients with PAH may receive this oxygen through a nasal cannula or a face mask covering their nose and mouth. There are additional devices available for delivering oxygen. An oxygen concentrator plugged into the household electricity supply is indicated when a patient requires oxygen during most parts of the day, even while asleep. Large oxygen cylinders can be used to help overcome short periods of breathlessness. When outside the home, patients with PAH may use portable oxygen cylinders with reduced size and weight. These portable cylinders hold about 2 hours of oxygen at 2 liters per minute.7,13 

Despite the benefits associated with this treatment, supplemental oxygen therapy may present some difficulties for patients to overcome. These can be related to the purchase, maintenance, and running costs of the equipment, as well as practical issues such as carrying the oxygen cylinder when already tired.9 Additionally, compliance with therapy may be compromised by the use of nasal cannulas and face masks and in specific situations such as upper respiratory tract infections.14

References

1. Pulmonary arterial hypertension. National Organization for Rare Disorders (NORD). Accessed March 7, 2022.

2.  Simonneau G, Gatzoulis MA, Adatia I, et al. Updated clinical classification of pulmonary hypertension. J Am Coll Cardiol. 2013;62(25 Suppl):D34-D41. doi:10.1016/j.jacc.2013.10.029

3. What is PH? Pulmonary Hypertension Association UK. Accessed March 7, 2022.

4. Lan NSH, Massam BD, Kulkarni SS, Lang CC. Pulmonary arterial hypertension: pathophysiology and treatment. Diseases. 2018;6(2):38. doi:10.3390/diseases6020038

5. Treatment: pulmonary hypertension. National Health Service (NHS). Accessed March 7, 2022.

6. PAH: how does oxygen therapy work? Lung Foundation Australia. February 5, 2021. Accessed March 7, 2022.

7. Oxygen. Pulmonary Hypertension Association UK. Accessed March 7, 2022.

8. Green S, Stuart D. Oxygen therapy for pulmonary arterial hypertension: we need to rethink and investigate. Respirology. 2020;25(5):470-471. doi:10.1111/resp.13797

9. Green S, Stuart D. Oxygen and pulmonary arterial hypertension: effects, mechanisms, and therapeutic benefits. Eur J Prev Cardiol. 2021;28(1):127-136. doi:10.1093/eurjpc/zwaa001

10. Roberts DH, Lepore JJ, Maroo A, Semigran MJ, Ginns LC. Oxygen therapy improves cardiac index and pulmonary vascular resistance in patients with pulmonary hypertension. Chest. 2001;120(5):1547-1555. doi:10.1378/chest.120.5.1547

11. Galiè N, Humbert M, Vachiery JL, et al. 2015 ESC/ERS Guidelines for the diagnosis and treatment of pulmonary hypertension: the Joint Task Force for the Diagnosis and Treatment of Pulmonary Hypertension of the European Society of Cardiology (ESC) and the European Respiratory Society (ERS): endorsed by: Association for European Paediatric and Congenital Cardiology (AEPC), International Society for Heart and Lung Transplantation (ISHLT). Eur Respir J. 2015;46(4):903-975. doi:10.1183/13993003.01032-2015

12. Sandoval J, Aguirre JS, Pulido T, et al. Nocturnal oxygen therapy in patients with the Eisenmenger syndrome. Am J Respir Crit Care Med. 2001;164(9):1682-1687. doi:10.1164/ajrccm.164.9.2106076

13. Home oxygen therapy. National Health Service (NHS). Accessed March 7, 2022.

14. Green S, Stuart D. Effects of oxygen therapy in a pediatric normoxemic patient with pulmonary arterial hypertension and congenital heart disease. Pulm Circ. 2019;9(2):11772045894019845610. doi:10.1177/2045894019845610

Reviewed by Debjyoti Talukdar, MD, on 3/4/2022.