62 Respiratory Homeostasis

The primary physiologic functions of the respiratory system are to provide oxygen for cellular metabolic processes and to remove the gaseous waste product carbon dioxide. When there is an increased need for oxygen, (best observed during rigorous exercise), our respiratory system responds with an increased rate and depth of breathing. In response to the adrenal hormone epinephrine, the bronchioles will also dilate, making it easier to move this increased volume in and out. With concurrent increases in cardiac output, we can typically meet our increased demands of those tissues with increased metabolic rates. Most of us do not make a conscious decision to increase our alveolar ventilation and the sympathetic nervous system does not control the diaphragm. Dilating the airways increases the rate at which air can move in and out, but does not affect volume.

Even when there is no need for an increase in oxygen levels in the tissues, the respiratory system will respond with increased ventilation if carbon dioxide levels start to increase. Increased carbon dioxide levels can occur in various forms of metabolic acidosis, where imbalances in metabolism lead to increased carbon dioxide levels in the body. Increased ventilation helps rid the body of carbon dioxide and limits the changes in pH the body would otherwise experience with the rising carbon dioxide levels.Chronic Obstructive Pulmonary Disease (COPD)

Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is a chronic, debilitating disease. COPD is a set of symptoms that can develop as a result of either chronic bronchitis or emphysema. People with chronic bronchitis constantly produce mucus in the conducting division in response to inhaled irritants or mild infections Emphysema which is permanent results from the progressive destruction of lung tissue. It is typically a more severe form of COPD than bronchitis, and may lead to death. The leading cause of both conditions is tobacco smoke, inhaled as either first-hand or second-hand smoke. Occasionally, emphysema can develop as a result of exposure to gases or fumes in the workplace. There is a low incidence of COPD resulting from a deficiency of the protein alpha-1-antitrypsin.

The symptoms of COPD include a cough with or without mucus, fatigue, frequent respiratory infections, shortness of breath (dyspnea), the inability to catch one’s breath, and wheezing. As the disease progresses, patients may have more symptoms which can progress in severity. Evaluating Lung sounds and X-rays are not necessarily useful in establishing a diagnosis for COPD. Spirometry and the examination of arterial blood gases to determine the blood concentrations of oxygen and carbon dioxide provide much better diagnostic tools.

As COPD worsens, blood oxygen levels decrease and blood carbon dioxide levels increase. The decreased oxygen leads to the fatigue, dizziness and decreased activity tolerance these people often experience. The increase in carbon dioxide can lead to respiratory acidosis, ultimately contributing to dysfunction in many of the body’s metabolic pathways.

There is no cure for COPD, but medications can help alleviate its effects. Inhalers that cause bronchodilation and contain steroids to reduce inflammation and mucus secretion are effective in many cases. Other anti-inflammatory medications may also help. If the conditions become severe, steroids can be administered orally or by intravenous methods. Oxygen may be needed, and mechanical breathing assistance may be used.



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