Persistent pulmonary hypertension, or PPHN, is a severe respiratory condition that affects newborn babies. It is also called persistent fetal circulation and it occurs in about two out of 1000 live births.

It is a major cause of illness and death in the newborn period in developing countries despite advancements in treatment.  It is a major cause of illness and death in the newborn period in developing countries despite advancements in treatment, and a high mortality rate, it remains one of the main causes of illness and death in infants despite advancements in treatment in recent years. Among the modern treatments for this illness, inhaled nitric oxide has caught attention due to its efficiency in treating the illness. Let us now take a look at the disease, its causes and symptoms, and the use of inhaled nitric oxide for its treatment.  

What is Pulmonary Hypertension in Newborns?

Neonatal pulmonary hypertension is a severe breathing issue that affects babies, and it happens when the circulatory system of the infant isn't adjusted to breathing outside of the uterus. The placenta and umbilical cord provide the fetus with oxygen while it is within the uterus, and during this stage, the pulmonary arteries, which provide blood to the lungs, are constricted. This means that very little blood reaches the lungs of the baby, and the blood usually travels to the remainder of the body bypassing the lungs. 

When the baby takes its first breath the lungs inflate with air containing oxygen. At this time these blood vessels normally would dilate (open up). Oxygen is then transferred from the air sacs (alveoli) of the lung, to the capillaries (very small blood vessels) surrounding the air sacs, from where it is taken to all parts of the body. However, pulmonary hypertension occurs when the blood arteries of the infant don't open up fully, and as a result, less oxygen can get to the baby's brain, heart, and other organs. PPHN is a potentially fatal medical condition that can arise soon after birth, but physicians are now able to recognize signs and start treatment immediately.

Use of Inhaled Nitric Oxide for Treating Pulmonary Hypertension in Newborns

Nitric Oxide is a gas when inhaled dilates ( opens up ) the pulmonary arteries, because of which it has become the therapy of choice for pulmonary hypertension. Decreasing the pulmonary pressure by dilating the pulmonary arteries increases the oxygen in the pulmonary blood vessels and systemic circulation and also reverses the right-to-left shunt that occurs due to the raised pulmonary blood pressure.

How is Nitric Oxide Therapy Performed on Newborns? 

The healthcare staff attending to the infant suffering from pulmonary hypertension will determine if they are a good candidate for inhaled nitric oxide treatment. Before this therapy, doctors may perform an echocardiography, on the infant in order to confirm the diagnosis and to rule out any other structural heart disease.

If the baby is a suitable candidate for iNO (inhaled Nitric Oxide ) then the gas is delivered to the baby through a modification in the ventilator circuit. These babies are quite sick and usually would already have been ventilated. The NO ( nitric oxide) is mixed with the ventilator gases in precise quantities with the help of a special machine. The gas is delivered to the lungs of the baby where it acts. The amount of nitric oxide is titrated to the response of the baby. As the baby improves the nitric oxide is gradually reduced ( weaned ) until finally it is discontinued. All this while the babys oxygensation status is monitored carefully.

Other Treatments for Pulmonary Hypertension in Newborns

• Before starting iNO doctors will usually ventilate the babies in an attempt to improve the oxygenation.
• Various modes of ventilation are used and if none f the conventional modes are successful then High Frequency Oscillatory Ventilation ( HFOV) is tried.
• In this form of ventilation the baby is given 600 or more extremely small breaths every minute. This seems to work in some babies when conventional ventilation fails and is thought to be similar to the panting breaths of dogs.

Medication

A number of drugs are used in the treatment of PPHN. Surfactant is administered in the trachea or wind pipe to ensure that all the alveoli in the lung are open. There are other drugs that can be injected directly into the veins or given orally eg sildenafil Bosentan.

Antibiotics are given if the child is suffering from infections, or there is a chance of infection. In certain cases, Inotropes (medicines that modify the blood pressure and circulation) are given to the baby with newborn pulmonary hypertension since these medications enter the circulation directly and ad improve the circulation by altering the strength of contraction of the heart, increasing the blood pressure, or altering the resistance of the systemic blood vessels to the blood flow. 

Causes of Persistent Pulmonary Hypertension of Newborn 

The cause of pulmonary hypertension cannot always be identified. The cause of pulmonary hypertension cannot always be identified.

• Respiratory distress syndrome (RDS): Premature neonates experience breathing difficulties due to incomplete lung development.
• Birth asphyxia: Low oxygen levels prior to or during birth is known as birth asphyxia. 
• Meconium aspiration: The baby may inhale their own sticky first faeces (meconium) leading to this condition.  
• Diaphragmatic hernia - A hole in the baby's diaphragm, the muscle that separates the chest from the abdomen, is known as a diaphragmatic hernia. The opening causes the abdominal contents to move to the chest hampering lung development and causing the baby to develop pulmonary hypertension.
• Some drugs can also predispose some babies to develop persistent pulmonary hypertension

Final Remarks 

Newborn pulmonary hypertension is a serious illness and frequently manifests in babies soon after birth. It happens when the baby's circulation does not change from the fetal state to the normal state, in which the heart pumps blood to the lungs. Only proper respiratory therapies and treatments specific to this condition can cure the newborn, and round-the-clock attention from experienced doctors is necessary during treatment.  

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