Pulmonary Hypertension

Pulmonary hypertension, in comparison to the more common arterial hypertension, routinely goes undiagnosed

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When it comes to diagnosis, there are certain disorders that have all the telltale signs, and can be diagnosed and subsequently treated quickly and in a consistent manner, but there are other problems that can remain more of a mystery for a longer period of time. Pulmonary hypertension, in comparison to the more common arterial hypertension, routinely goes undiagnosed - potentially leading to more dangerous complications the longer it remains unchecked. With causes that can sometimes be as difficult to diagnose as the problem, it's no wonder the disorder can go so long undiscovered.

In recent interviews with ADVANCE, Adam Benjafield, PhD, vice president of medical affairs at ResMed Americas, and Jock Lawrason, MD, chief medical officer, pulmonary and critical care specialist, Nantucket Cottage Hospital, discussed the obstacles of treating pulmonary hypertension and its varying causes.

Part of the problem is that pulmonary hypertension presents as any number of more common problems, with patients showing symptoms like fatigue, weakness, shortness of breath and a lack of energy. While the symptoms fit a variety of other disorders, Lawrason pointed out that the causes range across the map - from genetic variants, abnormal left heart problems, chronic heart failure and any number of complications from diseases like HIV, pulmonary diseases, liver diseases, connective tissue diseases and collagen vascular diseases. With such a broad target, it's easy to overlook certain possibilities in making a diagnosis.

"It's very important that complete care is given and that we find people with sleep-disordered breathing, because all the research and literature today shows that there may be additional cardiovascular benefits to treating patient with obstructive sleep apnea and other cardiovascular current morbidities," commented Benjafield.
Lawrason noted that sleep disorders like obstructive sleep apnea (OSA) cause chronic low oxygen levels in a patient and can also result in pulmonary hypertension. Despite the potentially deadly outcomes associated with it, OSA also routinely goes unnoticed by both patients and treating physicians. The sleep disorder has been linked to a growing number of cases of pulmonary hypertension, making it an easy-to-miss cause for an already hard-to-spot disorder.
"The research shows that, specifically with pulmonary hypertension, it can range 20 to 40 percent of pulmonary hypertension patients also have obstructive sleep apnea," explained Benjafield.

According to Lawrason, OSA is usually caused by tissue in a posterior part of the pharynx obstructing the patient's airway. The tissue can be one of several structures located in the throat - the tonsils, the uvula, even the tongue - and cause difficult breathing at night while a patient is sleeping. Although it is most commonly found in patients ranging from overweight to obese, it can also affect patient who are thin and can be found in both adults and children with signs including very loud snoring, gasping, gagging or simply long breaks in breathing. Treatment, however, is fairly simple and utilizes a CPAP machine or surgical procedure to remove the obstructive tissue.

"When patient stop breathing at night or obstruct, and the oxygen levels go down, the body's response is to release several different types of hormones," said Lawrason. "The blood pressure typically goes way up, the heart struggles, beating against the high pressure - in the systemic circulation, the response in the lungs to any low oxygen level is that the pulmonary vessels also constrict so that you're getting an increase in both the systemic pressure and the pulmonary pressure, which will gradually place a strain on the heart."

Both Benjafield and Lawrason noted that the link between pulmonary hypertension and OSA is the patient's hypoxemia.1 The low blood oxygen level cause by the sleep apnea puts a lot of strain on their body, leading to pulmonary hypertension. The longer OSA goes undertreated, the more difficult it is to treat the pulmonary hypertension. This doesn't necessarily make it a two-way street, however.

"The links between obstructive sleep apnea and cardiovascular disease are strongly connected with hypoxemia," Benjafield clarified. "The recurrent desaturations in the oxygen level would occur when a patient with obstructive sleep apnea stops breathing, because they do hundreds of times a night."

While pulmonary hypertension carries its own set of dangerous potential complications, it has no concrete impact in terms of affecting or awakening sleep disorders according to Benjafield. Treatments for pulmonary hypertension are usually based in varying drug cocktails, depending on the origin. These can be anticoagulants, vasodilators, phosphodiesterase inhibitors or endothelin pathway blockers among others. For patients with pulmonary hypertension in combination with OSA, the typical approach is a CPAP machine at night paired with pharmaceutical treatments as necessary.

"Depending on the ideology of the pulmonary hypertension, the medications might be limited or reduced, but if you don't treat the obstructive sleep apnea, it's very hard to get the optimal treatment for the pulmonary patient because the drugs used to treat hypertension don't have any effect on the obstructive sleep apnea," concluded Benjafield.

Both Benjafield and Lawrason commented on the importance of catching these disorders early on. For pulmonary hypertension, a recurring problem is that it's underdiagnosed -- the longer pulmonary hypertension goes untreated, the more life-threatening it becomes in the long. There is a similar lack of awareness in the case of OSA, which not only carries a separate set of problems, but can also lead to or exacerbate pulmonary hypertension and its additional complications. Despite being somewhat one-sided, the connection between pulmonary hypertension and sleep disorders like OSA is important to understand when it comes to two diseases that remain particular difficult to diagnose.

Michael Jones is on staff at ADVANCE. Contact: MJones@advanceweb.com

1-Mayo Clinic. Hypoxemia (Low Blood Oxygen). Mayo Clinic. http://www.mayoclinic.com/health/hypoxemia/MY00219

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