Question

How does emphysema affect acid-base balance? (pathophysiology) at a basic cellular level.

Answer 1

Emphysema is a pathalogical term that describes an abnormal distention of the air spaces beyond the terminal bronchioles , with destruction of the walls of the alveoli.It is the end stage of a process that has progressed slowly for many years.As the walls of alveoli are destroyed the alveolar surface area in direct contact with the pulmonary capillaries continually decreases, causing an increase in dead space(lung area where no gas exchange can occur)and impaired oxygen diffusion ,which leads to hypoxemia.As the disease progresses carbon di oxide elimination is impaired,resulting in increased carbon di oxide tension in arterial blood(hypercapnia) and causing respiratory acidosis. As the alveolar walls continue to break down ,the pulmonary capillary bed is reduced. Consequently, pulmonary blood flow is increased , forcing the right ventricle to maintain a higher blood pressure in the pulmonary artery.Hypoxemia may further increase pulmonary artery pressure.(Smeltzer,2004)

During exhalation, carbon dioxide produced by cellular respiration is projected into the environment. In the human body, carbon dioxide combines with water via carbonic anhydrase and forms carbonic acid which dissociates into a hydrogen ion and bicarbonate. This is why a reduced respiratory rate will lead to a decreased pH; the more carbon dioxide is exhaled, the less carbon dioxide present for this reaction.

Respiratory acidosis as a primary disorder is often caused by hypoventilation. This can be due to multiple causes including chronic obstructive pulmonary disease, opiate abuse/overdose, severe obesity, and brain injury. When respiratory acidosis occurs, the metabolic response should be to increase the amount of bicarbonate via the renal system. This does not always occur, and renal pathology can easily hinder the appropriate physiological response, leading to increased danger for the patient.(Sharma,2018)This happens in emphysema.

Ref:

1.Suzanne C.Smeltzer,Brenda Bare, 2004, Textbook of medical surgical nursing, Lippincott williams and wilkins, pg num:570,571

2.Erin Hopkins; Sandeep Sharma,2018,Physiology, Acid Base Balance.retrieved from ncbi journal.