Hyperinflated Lungs - Treatment Strategies

Introduction

The inability of the lungs to push out air when one exhales creates difficulty breathing, and excess air will get trapped inside the lungs causing them to overinflate. It is caused by an obstruction in the airways or when the alveolar sacs lose their elasticity, affecting the air's normal expulsion. Hyperinflation of the lungs can be most frequently seen in patients with chronic obstructive lung disease and other conditions like asthma and cystic fibrosis.

People with COPD (chronic obstructive pulmonary disease) often have limited performance in their day-to-day activities because of peripheral muscle weakness and exertional dyspnea. In COPD patients, hyperinflation occurs when exercising or during exacerbations are accompanied by intense, intolerable dyspnoea. Overinflation of the lungs may occur during everyday activities in milder forms of COPD. The dyspnea occurring as a sequel to normal or exertional activities leads to events such as physical deconditioning, activity avoidance, and reduced quality of life.

Several management strategies exist to control hyperinflation; notable among them are long-acting bronchodilators, which reduce the flow limitation and improve the emptying of air from the lungs. Various exercise programs are also introduced into the patient's lifestyle. Using bronchodilators and increasing the patient's ability to exercise, exertional dyspnoea can be reduced and improve the results of pulmonary rehabilitation programs.

What Changes in the Lungs Result in Hyperinflation?

Hyperinflation is most frequently seen in chronic obstructive pulmonary disease (COPD). Numerous factors contribute to the pathophysiology of this condition, and it varies from individual to individual. COPD is composed of two conditions:

• Chronic bronchitis, and

• Emphysema.

In chronic bronchitis, large airway inflammation and remodeling accompanied by edema and excess mucous production result in airway obstruction. On the other hand, irreversible destruction to the lung parenchyma and the surrounding vasculature results in emphysema. Recent research put forward that the obliteration of terminal bronchioles precedes destructive emphysema. The lungs will lose their elastic recoil pressure, decreasing the pressure for airflow out of the lungs. COPD patients will have a diminished expiratory flow rate at any given time compared with healthy individuals. In addition, the airway becomes more liable to collapse during expiration due to the depletion of alveolar walls and attachments. Alteration of the elastic properties of the lungs will change the equilibrium between the chest wall producing outward recoil, and the lung, producing inward recoil resetting the volume of the lungs at the end of a quiet expiration to a greater volume. These deteriorations give rise to limitations in expulsing air from the lungs giving rise to a hyper-inflated lung.

How Is Hyperinflation Related to COPD Progression and Co-morbidities?

Cross-sectional studies in COPD patients have demonstrated the signs of hyperinflation in even milder cases of COPD and suggested that everyday activities presented dynamic hyperinflation.

The human respiratory system can make adaptive modifications to adjust to mechanical changes. For instance, over-extended lungs are accommodated by reconfiguring the chest wall.

Hyperinflation of the lungs results in physical inactivity and physical deconditioning of the body, which proceeds to the development of co-morbidities. In the earlier stages, inactivity results in muscle wasting; this might also lead to co-morbidities. For example, some milder COPD cases with resting hyperinflation also depicted the presence of Subclinical left ventricular dysfunction.

Hyperinflation influences the progress of COPD. It increases the frequency of exacerbations in COPD and is a reliant marker of mortality. Quantitative computed tomography can assess COPD patients' expiratory volume decline. Recent studies suggest that most of the decline in lung volume is seen in milder cases. Early intervention could slow the condition's progression and maintain better organ function.

How to Measure Hyperinflation in COPD?

The usual investigations in general practice will not give a measure of hyperinflation. The relevant variables measured in COPD are

• Functional residual capacity - The air volume in the lungs at the end of the tidal expiration.

• Residual volume - The air volume in the lungs after a maximal expiration.

Highly sophisticated instruments like body plethysmography or spirometer with an analyzer for inert gasses are required to measure the variables.

What Are the Treatment Strategies for Hyperinflation?

The treatment implemented should improve the limitation in expiratory flow or reduce the ventilatory demand. A range of treatment strategies are available depending on the type of case; these include primary care with drug therapy and supplemental oxygen in case of hypoxia and oxygen desaturation, assisted ventilation for patients admitted to the hospital, and in case of advanced emphysema surgical approach is used.

Treatments that decrease the rate of respiration and increase ventilation are pulmonary rehabilitation and providing supplemental oxygen. Bronchodilators decrease airway inflammation and ease airflow through the bronchi, thus improving lung emptying. Surgical interventions can improve the elastic properties of the unaffected portion of the lung, thus preventing the condition's progress.

Pulmonary Rehabilitation/ Exercise Training:

Presently, pulmonary rehabilitation is the best way to improve the living quality of COPD patients. It involves education, smoking cessation, exercise training, and diet counseling.

Skeletal muscle function is drastically improved by exercise training which reduces dynamic hyperinflation. Bronchodilators used concurrently can improve the effectiveness of exercise training. Further, guideline recommendations are present to give bronchodilators before exercise training. In the absence of formal exercise training, patients are advised to take regular, less strenuous exercises like walking.

Pharmacotherapy:

Bronchodilators diminish airway obstruction and improve the emptying of air from the lungs.

It relaxes the smooth muscles of the airway, reducing respiratory muscle activity and improving the ventilatory mechanism.

Other treatments include roflumilast, theophylline, and mucoactive treatment (acetylcysteine).

Surgery:

Some cases necessitate a surgical procedure for management. Lung volume reduction surgery is performed to remove the damaged parenchyma of the lung so that the remaining healthy tissue can function normally.

Bullectomy can be performed to remove large pockets of air inside the lungs.

Conclusion

Persistent limitation in airflow is the main feature of chronic obstructive pulmonary disease (COPD), and the resultant hyperinflation produces exertional dyspnoea creating limitations in the individuals day to day activities that have a deleterious effect on the quality of life. In the earlier stages of COPD, some co-morbidities may start due to physical inactivity and deconditioning. The earlier the conditions are identified and treated, the better the prognosis.