Metabolism

• Metabolism refers to the chemical processes that occur in the body that result in change. All of these processes require energy in order for the change to take place. Some people use a lot of energy very quickly and have a high metabolic rate, while others do not use as much energy and have a low metabolic rate. In advanced lung disease, the body has to work much harder in order to get a sufficient amount of oxygen. According to Dr. Lisa Bellini, author of Nutritional Support in Advanced Lung Disease, this results in an increased metabolic rate and nutritional deficiencies. The condition is known as pulmonary cachexia syndrome and can occur in all types of lung disease.
  
  

Weakness and Fatigue

• When oxygen levels become too low, muscles and other body tissues cannot keep up with the demands placed on them. This is because oxygen is needed to form adenosine tri-phosphate (ATP) molecules that eventually, through a complex series of chemical reactions known as the Kreb's Cycle, provide the energy the cell will use. Since little oxygen translates to little energy, advanced lung disease patients experience weakness and fatigue.
  
  

Muscle Mass

• Those with advanced lung disease may find it difficult to get enough exercise because it becomes so hard to get enough oxygen during physical activity. Because muscles are used less frequently or for shorter time periods, they eventually atrophy and decrease in size. This, when coupled with increased metabolic needs, may result in weight loss.
  
  

Inflammation

• Many types of lung disease are related to pleurisy, or inflammation of the lining of the lungs. It occurs because the bacteria, virus, or other agent associated with the lung disease irritates the surface of the pleura, the lining of the lungs. This irritation results in pain that gets worse when the patient coughs. In addition to inflammation, some types of lung disease also cause fluid to build up in the aveoli, which are tiny air filled sacs of tissue where the carbon dioxide/oxygen exchange occurs.
  
  

Hypertension

• According to the American Heart Association, blood pressure in the arteries that supply the lungs can rise and the patient can experience secondary pulmonary hypertension. It is known as secondary pulmonary hypertension because the hypertension is the result of another condition (the lung disease) rather than heart disease. It is thought that this is due to vascular changes (specifically, constriction and thickening) that occur during the course of the disease.