Bronchitis is mainly caused by a chest infection that leads to pathological changes in the narrow airways of the lungs. Diagnosis is based on clinical history, physical examination as well as laboratory, imaging as well as breath analysis tests.
Diagnosis of acute bronchitis
The physical examination of patients presenting with symptoms of acute bronchitis reveals presence of fever, rapid breathing rate, wheezing, noisy respiration, rapid heart rate, prolonged and noisy expiration etc.
Fever may be present in some patients with acute bronchitis. High persistent fever however indicates pneumonia or influenza.
Sputum may be tested in laboratories for microbes. This however, is not very conclusive in acute bronchitis since most cases are caused by respiratory viruses.
A chest X ray is performed in patients whose physical examination suggests pneumonia or co-existing heart failure. A chest X ray may also be advised to elderly patients, those with chronic obstructive pulmonary disease, recent episode of pneumonia, cancer, tuberculosis patients and those with debilitated status or lowered immunity.
Lung function tests like spirometry are not routinely used in the diagnosis of acute bronchitis. These tests are needed in recurrent bronchitis cases. Pulse oximetry is recommended to check the blood oxygen levels.
Diagnosis of chronic bronchitis
Physical examination may not reveal any abnormality specifically. These patients however may have a history of previous episodes of flare ups and recurrent episodes of acute bronchitis.
On hearing the breath sounds with a stethoscope, the breath sounds rough or harsh and raspy with coarse sounding rales, rhonchi etc. on both inspiration and expiration. These sounds may clear completely on coughing and may be prominent at the lower ends of the lungs.
Decreased to absent breath sounds may be found at more than one place over the lungs. Wheezing may be noted on inspiration or expiration and expiration frequently is prolonged. Physical examination may also show lack of oxygen persistent leading to cyanosis (blue lips and nail beds).
Chest X ray may be normal in mild chronic bronchitis. However, occasionally there may be appearance of thickening of bronchial walls and crowding of bronchial structures in the lower part of the lungs on X ray in severe cases.
On imaging studies like CT scans the bronchi may also appear beaded like a rosary. This is caused by irregularly piled-up mucus interspersed with air pockets. The lower part of the lungs appear pinched and the diaphragm appears raised due to scarring and destruction of lung tissue and fibrosis. This is evident from bronchography examinations.
Fluoroscopy is not very useful but may reveal patterns of regional airpassages and ventilation within the lungs.
Routine blood examination is suggested. The white blood cell count is usually normal even during exacerbations or flare ups. The erythrocyte sedimentation rate may be raised. In advanced stages blood oxygen is lowered.
Bronchial secretions may be examined in the laboratory using bronchial lavage. The cells can be evaluated by simple examination of a wet preparation or a Papanicalaou stained smear. In stable patients there is a typical cellular pattern. Some cells appear degenerated and some altered or metaplastic under the microscope. Some may contain identifiable bacteria. There is presence of raised number of neutrophils as well.
Sputum cultures can be helpful in following the course of and suggesting the antibiotic treatment of chronic bronchitis. The usual organisms found are streptococci, Neisseria sp., D. pneumoniae, diphtheroids, and Hemophilus influenzae.
Bronchoscopy may be performed. This involves inserting a thin long tube within the airways with a light and camera at its tip. The physician views the inner walls of the bronchi on a connected monitor. The inner walls in chronic bronchitis appear red, edematous or swollen and friable (easily torn off).
A biopsy or a small tissue sample may also be taken from the inner walls during a bronchoscopy for examination under the microscope after staining appropriately.
Lung function studies including spirometry may appear normal initially. Over time the lung functions may deteriorate due to partial and complete obstruction of bronchi.
Further Reading
New study links childhood air pollution exposure to adult bronchitis