Chest Radiography and Assessment of Pulmonary Exacerbations in Cystic Fibrosis

Introduction

Pulmonary exacerbation is an important marker for cystic fibrosis progression. Imaging is an important diagnostic tool for noninvasive assessment of cystic fibrosis-related lung damage. The lung complication raises the risk of morbidity and mortality in affected individuals. Earlier spirometry was used to measure pulmonary exacerbations response to treatment. At present better imaging modalities are available and used to obtain clearer data.

What Is Cystic Fibrosis?

• Cystic fibrosis is an autosomal recessive condition.

• The condition affects multiple organs due to defects in the CF transmembrane receptor protein (CFTR).

• The development of cardiorespiratory complications can lead to mortality in cystic fibrosis-affected individuals.

• In the lungs, dysregulation of ion transport by defective CFTR causes accumulation of thick secretions in organs but more predominantly in the lungs. As a result, an inflammatory response is initiated. The patient finds it harder to breathe when thick secretions fill the lungs.

• Thick secretions act as a medium for the growth of pathogens like Pseudomonas aeruginosa and Aspergillus fumigatus.

• There is frequent exacerbation in lung complications along with decline in lung function in patients with cystic fibrosis.

• Cystic fibrosis-related diabetes development due to pancreatic dysfunction can harm lung function. Pulmonary oxidative stress causes stiffening of the lungs.

• Respiratory musculature and diaphragm functioning are impacted.

• The pulmonary status in cystic fibrosis is assessed with spirometry, gas transfer, and plethysmography of the full body for lung volume assessment.

• Diaphragmatic motion is evaluated with ultrasound, traditional fluoroscopy, and MRI (magnetic resonance imaging) fluoroscopy.

• Chest radiographs are normal in cystic fibrosis patients with mild lung damage.

What Are Plain Chest Radiography Findings in Cystic Fibrosis?

• Hyperinflation occurs that is reversible with early treatment. The symptoms become persistent.

• Hyperinflation is caused by mucus plugging small bronchioles.

• Hyperinflation can be the only sign of cystic fibrosis in children and adults.

• The classic sign of flattening of the diaphragm, anterior bowing of infant sternum, increased retrosternal air space, and generalized pulmonary overinflation appears.

• Bronchial wall thickening is caused by the infiltration of the submucosa by acute and chronic inflammatory cells.

• Linear streaking and scattered nodules appear due to obstruction to small airways with mucus.

• Areas of mucous accumulation appear as opacities in radiographic imaging.

• Atelectasis is a common condition present in children with cystic fibrosis with pulmonary involvement.

• The atelectasis can be segmental, patchy, or lobular and is caused by mucosal plugging and are more prevalent in the right upper lobe. The condition development leads to poor prognosis.

• Pneumothorax may be seen in a few patients.

• The heart appears small due to hyperinflation.

What Are Chest Radiographic Finding Categorizations?

The Birmhingam system of classification is used. The system utilizes five elements for assessment.

• Airtrappings.

• Linear markings.

• Nodular cystic lesions.

• General severity.

• Large lesions like atelectasis or consolidation.

The first four elements are scored from 0 to 4. The score 0 is given when the finding is absent and the score 4 is given when the findings are severe. The total accumulated points are subtracted with 25. The score for a very severe form of cystic fibrosis is 3. The normal chest radiograph has a score of 25.

What Are the Criteria for Pulmonary Exacerbation in Cystic Fibrosis?

The patient must have at least two of the following symptoms.

• Greater than or equal to a 10 % decline in mean forced expiratory rate volume.

• Cough.

• Malaise.

• Dyspnea (shortness of breath).

• Weight loss.

• Change in sputum volume and consistency.

What Are Spirometry and Its Limitations?

Spirometry is a simple test used to diagnose and monitor cystic fibrosis. They are also used in treatment outcome monitoring. The test requirse the patient to breath into a device called a spirometer. The test measures forced vital capacity, slow vital capacity, and forced expiratory volume in one second. A reduced forced expiratory volume in cystic fibrosis patients indicates an obstruction in the lungs caused by mucosal thickening or scarring of the lungs. Few patients show restrictive and obstructive conditions in the lung caused by reduced vital capacity and forced expiratory volume. Such patients struggle to exhale air.

Limitations of spirometry are as follows:

• It is an artificial technique requiring forced breathing maneuvers.

• The mouthpiece and nose clip used during diagnosis can interfere with airflow.

• In patients with cystic fibrosis, lung function can vary on a daily basis.

• The marker for improvement or deterioration of lung function is not described in spirometry.

• A spirometry test is not sensitive to lung damage occurring in cystic fibrosis.

• It increases the risk of air pathogen exposure to the operator by generating aerosol.

What Is Dynamic Chest Radiography (DCR)?

• Radiography has a wide field of view.

• Noninvasive procedure.

• The images are obtained in real-time.

• High spatial and temporal resolution imaging of the thorax is combined with computer-assisted tracking of moving thoracic structures like the thorax and chest wall.

• The imaging does not require the use of mouthpieces or artificial maneuvers.

• Posterior-anterior imaging is of diagnostic significance and lung area calculations.

• The radiation dose is kept low at a level of 0.13 mSv (sievert) for a 10-second exposure.

• The radiographic test is done in a short time with ease.

• The series of moving thorax images are obtained over 10 to 20 seconds up to 15 images per second.

• Rapidly moving diaphragm or pulmonary vessels can be clearly visualized.

• The DCR can detect diaphragmatic abnormalities like dis-coordinated diaphragmatic motion, hemidiaphragm immobility, and eventration.

• Patterns of breathing can be evaluated.

• Quantitative Measures Recorded by DCR.

• Diaphragmatic excursions which include maximal inspiration and expiration are recorded.

• Peak diagram velocity during inspiration and expiration are measured.

• From the apex to the diaphragm, peak distance is measured.

• Lung field area range during tidal and shallow breathing is measured.

• Changes Documented in DCR After Treatment.

The treatment of pulmonary symptoms of cystic fibrosis is followed by DCR imaging to determine treatment outcomes.

• The median right showed improvement from 18 mm (millimeter) to 25 mm and the left from 13 mm to 19 mm of hemidiaphragm excursion during deep breathing.

• Expiratory diaphragm velocity improved from 7mm /sec (millimeter per second) to 11 mm/sec on the left and 6mm/sec to 9mm/sec on the right side of the lung.

• Tidal breathing excursion improved from 12 mm to 15 mm on the left and 11 mm to 13 mm in right after treatment.

Dynamic chest radiography revealed improvement in diaphragm speed and chest wall movement during breathing after treatment of pulmonary symptoms.

Conclusion

Cystic fibrosis is a complex disease that can cause morbidity or mortality if adequate treatment is not administered. It is important to diagnose the disease early and treat the disease. Dynamic chest radiography can evaluate treatment progress in cystic fibrosis patients and prevent further lung function worsening.