Chronic obstructive pulmonary disease
Thorough assessment performed by competent EMS personnel is critical to patient survival
Chronic obstructive pulmonary disease (COPD) affects 24 million Americans each year. In that same amount of time, approximately 1.5 million patients with the disease will seek emergency treatment, and half of those will require hospital admission (Mannino, Homa, Akinbami, Ford, & Redd, 2002).
It is the third leading cause of death in the United States (Kochanek, Xu, Murphy, Miniño, & Kung, 2011). One in every three patients with an acute exacerbation of COPD will die within a year of first contact with the EMS system (Steinmetz, Rasmussen, & Nielsen, 2006).
The American Thoracic Society and the European Respiratory Society (2004) define COPD as a progressive disease characterized by an abnormal inflammatory response within the lung tissue resulting in airflow limitation.
Experts subdivide COPD into two clinical conditions that are often present in the same patient simultaneously. Chronic bronchitis develops when glands along the walls of the central airways enlarge, resulting in excessive mucus production and inflammation of the cartilaginous airways (Mullen, Wright, Wiggs, Pare, & Hogg, 1985; Reid, 1960). The second condition, emphysema, occurs when the airway walls distal to the terminal bronchioles begin to break down, causing enlargement of the airspaces and loss of alveolar attachment, which contributes to peripheral airway collapse (Lamb et al., 1993).
One significant risk factor for the development of COPD is cigarette smoking. In general, the more a person smokes, the greater chances he or she has of developing COPD (Forey, Thornton, & Lee, 2011), although not all cigarette smokers develop clinically apparent COPD (Global Initiative for Chronic Obstructive Lung Disease [GOLD], 2011). Long-term smoking results in a cycle of repeated lung injury followed by attempts at self-repair and tissue remodeling (Corbridge, Wilken, Kapella, & Gronkiewicz, 2012).
COPD is non-reversible: Once the condition develops, eliminating exposure to cigarette smoke may only halt or slow the progression of the disease (Anthonisen, Connett, & Murray, for the Lung Health Study Research Group, 2002).
Patients with COPD often call EMS during periods of exacerbation, during which the symptoms worsen rapidly. Exacerbations are characterized by a change in the patient's baseline condition that is sufficient for a change in the management strategy (American Thoracic Society and the European Respiratory Society, 2004). About half to three-quarters of all exacerbations are the result of respiratory infections, with about 10 percent resulting from air pollution (Abbatecola, Fumagalli, Bonardi, & Guffanti, 2011).
Just prior to exacerbation, symptoms such as dyspnea, sore throat and cough worsen (Seemungal, Donaldson, Bhowmik, Jeffries, & Wedzicha, 2000). But airflow obstruction remains relatively normal with mild exacerbations (Saetta et al., 1994) and only slightly reduced with more severe exacerbations (Seemungal, Donaldson, Bhowmik, Jeffries, & Wedzicha, 2000).
The primary factor contributing to poor gas exchange during severe exacerbations is ventilation-perfusion mismatch, or the inequality between the volume of air flowing into the alveolar spaces and the volume of blood flowing the through the pulmonary capillaries (Barberà et al., 1997). This is likely caused by the increased work of breathing, yielding increased oxygen consumption by the respiratory muscles (Barberà et al., 1997).
Supplemental oxygen administration remains at the center of the prehospital management of acute COPD exacerbation. The goal of oxygen therapy is to keep the oxygen saturation values above 90 percent when measured by pulse oximetry (American Thoracic Society and the European Respiratory Society, 2004). Attempting to Increase the value much greater than that does not confirm significantly greater benefit and may actually lead to increased carbon dioxide retention and respiratory acidosis (American Thoracic Society and the European Respiratory Society, 2004).
A recent prehospital evaluation of oxygen administration in patients with a confirmed diagnosis of COPD (Austin, Wills, Blizzard, Walters, & Wood-Baker, 2010) found a significant increase in mortality when paramedics administered high-flow oxygen compared to oxygen administration titrated to pulse oximetry values (9 percent and 2 percent, respectively).
When delivering oxygen, EMS personnel should start with a nasal cannula or a venturi mask (American Thoracic Society and the European Respiratory Society, 2004).
For patients with respiratory rates greater than 24 per minute or capnography measurements above normal, EMS personnel should consider the use of non-invasive positive pressure ventilation (NPPV) (American Thoracic Society and the European Respiratory Society, 2004). NPPV increases alveolar ventilation, thus improving arterial blood gas measurements (Diaz et al., 1997).
One form of NPPV that is popular in the prehospital setting is continuous positive airway pressure (CPAP) ventilation. CPAP reduces oxygen consumption of the respiratory muscles by reducing the work of breathing (Appendini et al., 1994). Low oxygen concentration CPAP (28-30 percent) is safe and effective (Bledsoe et al., 2012) and may be a reasonable alternative to higher oxygen concentration CPAP.
There are no medications currently available that can reverse the physiological changes associated with COPD once they occur. Head-to-head comparisons of ipratropium bromide with beta agonists do not demonstrate an advantage of one medication over the other (Brown, McCrory, & White, 2001).
In addition, there is no evidence that a combination of the two medications offers any short or long term advantages of ether of the medications used alone (Nannini, Cates, Lasserson, & Poole, 2007). Administration of systemic corticosteroids significantly improves lung function and lowers the risk of future exacerbations, although there is still controversy about the optimal dose and duration of therapy (Albert, Martin, & Lewis, 1980; Quon, Gan, & Sin, 2008).
Exacerbation of COPD is a frequent and often life-threatening prehospital event. A thorough assessment performed by competent EMS personnel is critical to patient survival:
- Administer oxygen by nasal cannula while monitoring the patient's pulse oximetry and capnography values closely
- Consider using NPPV early in patients with clinical evidence of hypercapnea or significantly increased work of breathing.
- Inhaled bronchodilators may provide relief for patients associated bronchospasm, although the optimal medication remains unknown.
- Finally, systemic corticosteroids may be beneficial; however oral formulations of the drugs may be as effective as parenterally administered doses (Quon, Gan, & Sin, 2008).
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