Acute respiratory failure is a potentially life-threatening complication of COPD.
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Chronic obstructive pulmonary disease is a progressive, irreversible lung disorder characterized by airway inflammation and impaired breathing. Although it usually takes years for COPD to cause significant symptoms, the condition is typically punctuated by periodic exacerbations, or downturns. A study published in the November 2012 issue of "Thorax" revealed that each exacerbation of COPD significantly increases a patient's risk of dying. Acute respiratory failure, a potentially life-threatening complication of COPD, may occur during an exacerbation.
Poor Gas Exchange
Your respiratory system is designed to exchange gases with the surrounding atmosphere. Each time you inhale, oxygen from incoming air is transferred into your bloodstream. When you exhale, carbon dioxide -- a waste product of metabolism -- is removed from your bloodstream and released into the atmosphere. Respiratory failure occurs when your lungs are not capable of efficient gas exchange or the muscular mechanism that expands and deflates your lungs is weakened for any reason.
Your doctor can determine if your respiratory system has failed by measuring the levels of oxygen and carbon dioxide in your bloodstream. The amount of a particular gas in your blood is measured as a partial pressure or "tension," which is expressed in millimeters of mercury (mmHg). Respiratory failure is generally defined as an arterial oxygen tension less than 60 mmHg or an arterial carbon dioxide tension greater than 45 mmHg. Respiratory failure due to a low oxygen level is called hypoxic respiratory failure, while that due to a high carbon dioxide level is called hypercapnic respiratory failure. People with COPD often have both types.
Conditions that lead to a sudden decline in oxygen uptake by the lungs and set the stage for hypoxic respiratory failure include severe infections, such as bacterial pneumonia and influenza; systemic inflammatory conditions, such as pancreatitis; fluid overload due to transfusions or kidney, liver or heart disease; and pulmonary emboli, which are blood clots in your lungs.
Hypercapnic respiratory failure usually stems from impairment of the mechanical process of air movement. Conditions that interfere with respiratory muscle function or chest wall movement, such as prolonged bed rest, a chest wall injury or respiratory muscle fatigue, increase carbon dioxide retention and may trigger acute respiratory failure.
Signs and Symptoms
Signs and symptoms of acute respiratory failure include severe shortness of breath, restlessness, anxiety, sweating, blue lips and extremities, rapid breathing, rapid heartbeat, confusion, disorientation, combativeness and, eventually, coma. Conscious patients suffering from respiratory failure typically have visibly labored breathing, using the muscles of their neck, shoulders and upper chest and back to assist with their respirations. People with pneumonia often have a fever and a cough that produces more phlegm than usual. If fluid overload is the cause of respiratory failure, your ankles may be swollen and your breathing may be accompanied by crackling or bubbling sounds.
Acute vs. Chronic Failure
Due to COPD's slowly progressive nature, most people are able to partially adapt to a gradual decline in lung function. Consequently, chronic respiratory failure -- characterized by abnormal blood gases and only mild or moderate shortness of breath -- is not unusual in COPD patients. If you already have chronic respiratory failure and develop pneumonia, heart failure or any other condition that impairs gas exchange or air movement, your blood gases may deteriorate rapidly and your symptoms could grow rapidly worse. Such "acute-on-chronic" respiratory failure is a common cause of hospitalization among people with COPD.
Similarly, people with mild COPD and normal blood gases -- that is, those who are not already in chronic respiratory failure -- can develop acute respiratory failure if they encounter a problem that suddenly interferes with their ability to move air or exchange oxygen and carbon dioxide. Thus, if you have COPD you could develop chronic, acute-on-chronic or acute respiratory failure.
Acute respiratory failure, including acute-on-chronic respiratory failure, significantly increases the risk of death for people with COPD. It usually requires a hospital stay, and doctors may use some type of mechanical support to help you breath. Advances in ventilatory support have made it possible to provide oxygen and improve many patients' lung function without placing a tube in their airway. Your doctor may prescribe medications to dilate your airways, reduce mucus production, treat infection and eliminate excess fluid. Your specific treatment plan will be guided by the underlying condition that triggered your acute respiratory failure and your response to initial therapy.