Pulmonary Tests for Sickle Cell Disease
Pulmonary (lung) disease is common and a leading cause of death for people with sickle cell disease (SCD). Pulmonary hypertension and acute chest syndrome are some of the most common and severe lung complications.
Many adults have undetected chronic lung disease that leads to life-threatening lung failure. Regular lung tests, often called pulmonary function tests, can help to diagnose lung problems early.
The most common lung function tests for people with SCD are spirometry and pulse oxygen saturation. These and other lung tests measure how well your lungs take in oxygen and deliver it to your red blood cells.
Why is testing for lung function important?
Chronic lung complications are a major cause of death in people with SCD. Some common lung complications of SCD include:1-3
- Acute chest syndrome
- Chronic dyspnea (shortness of breath)
- Pulmonary hypertension (high blood pressure in the lung)
- Venous thromboembolism (blood clots in veins that circulate and get stuck in the lungs)
- Pulmonary fibrosis (lung scarring and damage)
- Sleep-disordered breathing, most commonly obstructive sleep apnea
Many of these complications are more common in children. Regular tests for lung function can help identify issues early and monitor lung function after treatment. For example, lung tests can determine:4
- Your lung and airway growth
- The site and type of airway obstruction
- The impact of therapies on lung function
- The impact of environmental factors on lung function
- The degree and progression of lung complications
Lung function tests are usually performed by specialized lung doctors, called pulmonologists.
What are some common tests?
Spirometry measures how much air you inhale, how much you exhale, and how quickly you exhale. Doctors most often used it to diagnose and monitor lung disease in childhood, such as asthma. During the test, you will breathe into a tube attached to a machine called a spirometer. Doctors may perform spirometry tests in children with SCD every couple years and more frequently for those with dyspnea or asthma. Spirometry measurements that are lower than normal usually mean the airway is blocked.1,5,6
Pulse oxygen saturation
Oxygen saturation is how much of your blood carries oxygen. Doctors measure it with a pulse oximeter, which is a sensor placed on your fingertip or ear. Most children and adults with SCD have low oxygen saturation, especially after exercise and during sleep. Low oxygen saturation may indicate obstructive sleep apnea or other pulmonary complications.1,7
This is a technique that uses sound waves to look at blood flow from the heart. Doctors use it to measure your blood velocity (blood flow rate), which can help diagnose pulmonary hypertension. Adults with sickle cell anemia may undergo echocardiography every couple years since pulmonary hypertension is a major cause of death.8,9
When your amount of exhaled air is low, doctors may measure your lung volume. This measures the amount of air in your lungs after you exhale. This can help doctors determine your total lung capacity (how much air your lungs can hold after you inhale). Doctors will usually use a machine called a plethysmograph to measure your lung volume. You will sit inside it and breathe into a mouthpiece.
The diffusing capacity of the lung is how well it transfers oxygen to red blood cells. Low diffusing capacity in people with SCD may indicate pulmonary hypertension, embolism, or fibrosis.4
Maximal respiratory pressures
When your amount of exhaled air is low, doctors may measure your maximum respiratory pressure. This analyzes the strength of your inhalation and exhalation muscles. Low measurements may mean that certain respiratory muscles are weak.4
Doctors may perform a few exercise tests, but the most common version is the 6-minute walk test. This test will measure how far you walk in 6 minutes. It will also analyze how the walk affects your oxygen saturation and heart rate. It is a good index of your physical function and how well you are responding to treatment for pulmonary fibrosis or hypertension.10,11