One of the primary tests for assessing lung disorders is the use of spirometry. A spirometer measures the speed and volume of air inspired and expired by the pulmonary system. It plays a critical role in evaluating conditions like cystic fibrosis, pulmonary fibrosis, chronic obstructive pulmonary disease and asthma. A spirogram will tell the diagnostician whether a patient has one of two categories of abnormal lung function, obstructive or restrictive.

In persons suffering from restrictive lung disease (RLD), the expansion of the lungs is impaired when breathing in. This causes a decrease in lung volume, making it more difficult for the person to breathe, impairing both oxygenation and ventilation. One type of condition underlying RLD is pulmonary fibrosis. Pulmonary fibrosis is associated with scarring of the lungs, resulting in a honeycomb-like appearance. While rare, the disease is poorly understood and is frequently fatal.

Other disorders that fall under the umbrella of RLD include the autoimmune condition, sarcoidosis; myscular dystrophy, amyotrophic lateral sclerosis (ALS), and obesity. Most patients present initially with difficulty breathing. Sarcoidosis is recognized by red, swollen lesions known as granulomas, mostly affecting the lungs and the skin. Some patients may suddenly develop symptoms that disappear spontaneously. Other people may never know they have sarcoidosis until they have an x-ray for another condition.

Obstructive lung disease (OLD) is characterized by inflamed and obstructed airways. OLD obstructs airflow, leading to difficulty exhaling and frequent trips to the hospital. Bronchitis, asthma and COPD are examples of obstructive lung diseases. A common feature of OLD is loss of the ability to exhale 70 percent of breath within one second.

Asthma is caused by inflammation of the airways. One of the most common respiratory problems, it normally presents with wheezing, coughing and shortness of breath. Other, less frequent, symptoms, are fatigue, rapid breathing and sighing. Asthma can be life-threatening.

The most serious symptom of CF is impaired breathing. Cystic fibrosis affects the lungs, pancreas, liver and intestine. Twenty-first century improvements in treatment and diagnosis have resulted in a much better prognosis than 50 or 60 years ago. In 1959, the median age of survival was only six months. As of 2008 in the United States, this had risen to 37.5 years; in Canada, it improved from 24 years in 1982 to 47.7 years in 2007. In Russia, the cost of medical treatment is often prohibitive and lung transplants do not take place. Here, the median age of survival is only 25 years.

COPD encompasses diseases like chronic bronchitis and emphysema. In the case of emphysema, the inner surface of the lungs becomes permanently damaged, usually from exposure to cigarette smoke. Although there is no cure, removal of the trigger, cigarette smoking, results in an improved ability to exhale.

Spirometers are essential devices for diagnosing both restrictive and obstructive lung conditions. Obstructive lung diseases include COPD, bronchitis and asthma. Restrictive lung disorders refer to sarcoidosis, muscular dystrophy, amyotrophic lateral sclerosis, pulmonary fibrosis and obesity hyperventilation syndrome.