vendredi 21 mars 2014

The Place Of The Spirometer In Diagnosing Lung Conditions

By Jaclyn Hurley


One of the most common tests for measuring lung function is the use of a spirometer. This is a device that measures the speed and volume of air inspired and expired by a person's lungs. Spirometry is used to assess conditions such as chronic obstructive pulmonary disorder (COPD), asthma, cystic fibrosis and pulmonary fibrosis. It is able to distinguish between two types of abnormal respiratory pattern, obstructive and restrictive. There are several types of spirometers in use and they have been evolving since the first century AD.

Restrictive lung disease (RLD) impedes the expansion of the lungs on inspiration. This results in a decreased lung volume, forcing the individual to work harder to draw breath. Both ventilation and oxygenation are impaired. Pulmonary fibrosis, or scarring of the lung is one condition underlying RLD. The normal lung parenchyma becomes interspersed with scar tissue, resulting in a honeycomb appearance. Thankfully rare, pulmonary fibrosis is poorly understood, worsens over time and is often fatal.

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.

Cystic fibrosis affects the lungs, liver, intestine and pancreas. Shortness of breath is the most serious symptom of cystic fibrosis. Improvements in diagnosis and treatment have extended the life span for people with CF. In 1959, the median survival age was 6 months. In the United States, it had increased to 37.5 years by 2008. In Canada, the median age at survival grew from 24 to 47.7 between 1982 and 2007. Patients are not so lucky in Russia, where lung transplants are not available and basic medical treatment is expensive. Here, the median age of survival is only 25 years.

The designation chronic obstructive pulmonary disease (COPD) includes conditions like chronic bronchitis and emphysema. With emphysema, the delicate lining of the lung becomes irreversibly damaged. This is usually a consequence of exposure to cigarette smoke, which restricts the patient's ability to breathe out. Although there is as yet no cure, removing the stimulus of cigarette smoke does bring improvement.

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.




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