Nitric oxide therapy is a medical treatment that administers nitric oxide gas to patients. This therapy aims to improve oxygenation and support the pulmonary system. Nitric oxide is a naturally occurring molecule in the human body, playing a significant role in various physiological processes. The therapy delivers this gas directly to address specific respiratory and cardiovascular conditions.
The Biological Function of Nitric Oxide
Nitric oxide (NO) functions as a signaling molecule throughout the body. Its most recognized function is as a potent vasodilator, meaning it relaxes blood vessels. This relaxation causes blood vessels to widen, which increases blood flow and helps regulate blood pressure.
The molecule is synthesized from the amino acid L-arginine by enzymes called nitric oxide synthases (NOS). Beyond vasodilation, nitric oxide also contributes to neurotransmission, facilitating communication between nerve cells. It also plays a part in the immune response, helping the body defend against pathogens.
Medical Applications of Nitric Oxide Therapy
Inhaled nitric oxide (iNO) therapy is primarily used for pulmonary hypertension. Its most established application is in newborns with persistent pulmonary hypertension of the newborn (PPHN), a condition where lung blood vessels remain constricted after birth. iNO works by selectively dilating these pulmonary arteries, improving blood flow to the lungs and enhancing oxygen uptake. This selective action means it primarily affects the lungs without causing widespread blood pressure drops.
The therapy is also employed in adults with pulmonary hypertension linked to Acute Respiratory Distress Syndrome (ARDS). While not universally FDA-approved for ARDS, it is used off-label to improve oxygenation by redirecting blood flow to better-ventilated areas. Furthermore, iNO serves a supportive role during and after certain cardiac surgeries, where it helps manage pulmonary hypertension that can complicate recovery. Its use in these scenarios can lower pulmonary artery pressure and improve right ventricular function.
Administration and Monitoring
Nitric oxide therapy is delivered as a gas, typically mixed with oxygen, for the patient to inhale. This process requires specialized equipment for precise delivery and patient safety. The gas is administered through a ventilator circuit, often in an intensive care unit, managed by medical professionals.
Delivery systems provide a constant concentration of nitric oxide, often starting around 20 parts per million (ppm). Continuous monitoring of the patient’s response is performed, alongside measurements of nitric oxide, oxygen, and potential byproducts in the breathing circuit. This oversight helps medical teams adjust the dose and ensure the therapy’s effectiveness while minimizing potential complications.
Potential Risks of Treatment
Despite its benefits, medical nitric oxide therapy carries potential risks that require careful oversight. One primary concern is methemoglobinemia, a condition where hemoglobin, the oxygen-carrying protein in red blood cells, is altered and cannot effectively transport oxygen. This risk is closely monitored, as high methemoglobin levels can impair oxygen delivery to tissues.
Another potential complication is the formation of toxic nitrogen dioxide (NO2). Nitric oxide can react with oxygen to produce NO2, a potent pulmonary irritant. Delivery systems minimize this reaction, and NO2 levels are continuously measured to prevent patient exposure to harmful concentrations. Abruptly stopping inhaled nitric oxide therapy can also lead to rebound pulmonary hypertension, where lung pressures suddenly increase, potentially worsening the condition. To prevent this, the therapy is weaned slowly and gradually over several hours.
Distinguishing Medical Therapy From Supplements
It is important to differentiate between medical nitric oxide gas therapy and dietary supplements claiming to boost nitric oxide production. Medical therapy directly administers nitric oxide gas through inhalation in a controlled clinical setting. This direct delivery allows for precise dosing and targeted effects on conditions like pulmonary hypertension.
In contrast, dietary supplements, such as those containing L-arginine or L-citrulline, are precursors that the body uses to produce its own nitric oxide. These supplements do not contain actual nitric oxide gas. The effectiveness of these supplements in achieving specific health outcomes is often inconclusive, and they are not a substitute for prescribed medical treatment for serious conditions.