As emphysema may take years to develop, signs and symptoms may be quite mild at the start. However, emphysema is a progressive decline in respiratory function – particularly exhalation – due to the loss of the alveolar tissue and remodelling with inelastic tissue.  As emphysema progresses, the patient will accumulate “trapped air” yet have signs of poor oxygenation and increased work of breathing since energy is now needed to both inhale and exhale (recall that exhalation is passive due to the elastic nature of the lungs).

Figure 5.18 Clinical Manifestations of Emphysema based on the Pathology

Exacerbations of emphysema

As emphysema progresses, the patient’s ability to exhale decreases yet work of breathing increases.  As such, emphysema patients may not be able to cough as deeply or forcibly as needed, due to the decreased exhalation abilities.  Normally, the cough reflex is helpful in expelling mucous which has trapped inhaled irritants or pathogens:  hopefully, before the pathogens have a chance to infect.  Thus, emphysema patients are more susceptible to lung infections.

Similarly, patients with emphysema are experiencing chronic inflammation from the frequent injury to the lungs (e.g. daily cigarette smoking).  An additional injury to the lungs (e.g. environmental pollution from forest fire smoke), on top of the daily injuries, will induce more of an inflammatory reaction which will make the signs and symptoms worse. This is known as exacerbation.  Exacerbations are, hopefully, temporary as withdrawal of the additional injury will stop the worsening of symptoms. However, dyspnea and changes in  gas exchange between alveoli and blood will cause great discomfort in patients without medical intervention.

Section Review

• Remodeling leads to stiffer, less compliant lung tissue which progressively makes exhalation more difficult requiring expenditure of energy.
• As emphysema progresses, the accumulated loss of alveolar membrane tissue leads to decreased gas exchange resulting in less oxygenation of blood and insufficient elimination of CO2.  Thus blood gases are affected (i.e. hypoxic and hypercapnic).  As blood is less oxygenated, all tissues will be less nourished resulting in impaired function (e.g. weakness, fatigue) and the sensation of difficult breathing (dyspnea).
• As emphysema progresses, there is an accumulation of “trapped air” leading to a hyperinflation of lungs, and hence, chest volume.
• Remodeling can also lead to an increase in mucous production to help protect airways from inhaled irritants, resulting in increased coughing to expel the mucous. However, coughing is an active process requiring open airways – thus coughing become less effective.
• As emphysema progresses, the patient can manage their daily activities based on how well their lungs tolerate the physical demand. However, any additional challenge to the lungs (e.g. increased irritants in the air due to forest fire smoke, lung infection) can lead to a sudden worsening of lung function  (i.e. exacerbation of emphysema) that can cause dyspnea, insufficient oxygenation of blood, and fatigue from the increased work of breathing an this additional challenge. Medical intervention is required as the patient will have difficulty adapting.

Review Questions