The Use Of A Spirometer To Diagnose Lung Disease

By Jaclyn Hurley


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.

A person with a restrictive lung disorder (RLD) has difficulty expanding the lungs when drawing in breath. This causes a decrease in lung volume and forces the lungs to work harder. Both oxygenation and ventilation are negatively affected. Pulmonary fibrosis, or scarring of the lungs, falls under the umbrella of RLD. Here, the normal tissue of the lung is dotted with lesions of scar tissue, creating a honeycomb-like appearance. Pulmonary fibrosis is badly understood, normally gets worse with time and is frequently fatal. Fortunately, it is a rare condition.

Other conditions that contribute to restrictive lung disease include obesity, sarcoidosis (an autoimmune condition), scoliosis and neuromuscular diseases including amyotrophic lateral sclerosis (ALS) and muscular dystrophy (MD). The primary presenting symptom that drives people to the doctor is almost always difficulty in breathing. Sarcoidosis is characterized by swollen and reddened tissue called granulomas. These mostly affect the skin and the lungs. Some people develop symptoms suddenly and recover spontaneously after a few months or years. Others never experience any symptoms; the condition is incidentally following an x-ray for another reason.

The main features of obstructive lung disorders are obstructed and reddened airways. Airflow is obstructed, resulting in difficulty breathing out and, inevitably, numerous visits to the hospital. A diagnostic feature of OLD is the inability to expire 70% of breath in one second. Examples of OLD include COPD, bronchitis and asthma.

Asthma, caused by inflammation of the airways, is a common respiratory condition most often characterized by coughing, wheezing and shortness of breath. Less common symptoms include sighing, fatigue and rapid breathing. Asthma is occasionally 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.

Spirometry is an important diagnostic tool in respiratory medicine. Distinguishing between obstructive and restrictive conditions, it enables doctors to inform interventions and determine prognoses.




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