In this section, common medical causes of respiratory distress will be presented. For each, this section will highlight the pathophysiology (causes) as well as the typical clinical presentation and general treatment.
COPD AND ASTHMA PATHOPHYSIOLOGY
The prevalence and incidence of asthma is very high in the Western world.10 The number of people with asthma continues to grow. One in 12 people (about 25 million, or 8% of the population) had asthma in 2009, compared with 1 in 14 (about 20 million, or 7%) in 2001.11
Asthma is a disease that is reversible and episodic. It is characterized by a chronic inflammatory disorder of the airways coupled with airway hyperresponsiveness that leads to recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. Children will often be awakened from a sound sleep with an episode and it may consist primarily of coughing (cough variant asthma). These episodes are associated with reversible airflow obstruction and between acute attacks, the patient often returns to a normal respiratory pattern. Patients with persistent inflammation may have lung remodeling over time, which eventually leads to a loss of lung function. Asthma patients tend to be younger patients and are more likely to have an allergy trigger or a strong family history.
Obstructive lung disease can be classified into two categories: chronic bronchitis and emphysema. Patients with COPD have significant fixed airway obstruction that remains, even when the disease in under control. Both diseases cause chronic cough and shortness of breath. Chronic inflammation causes structural changes and irreversible airflow limitation. This can be caused by an increase in resistance of the conducting airways or an increase in compliance due to destruction of the airway walls or both. Destruction of the lung parenchyma, also by inflammatory processes, leads to the loss of alveolar attachments to the small airways and decreases lung elastic recoil; in turn, these changes diminish the ability of the airways to remain open during expiration. Often, COPD patients have right heart failure and chest remodeling. Cigarette smoking is a primary cause of COPD. Other environmental and genetic factors can cause COPD including exposure to air pollution, second-hand smoke, occupational chemicals, and a history of childhood respiratory infections.12
Chronic bronchitis is characterized by chronic cough and sputum production. A working definition of chronic bronchitis can be defined as a chronic, productive cough for 3 months during two successive years in which other causes for chronic cough have been excluded.13
Emphysema is destruction and irreversible enlargement of the air spaces distal to the terminal bronchioles. The destruction of the alveoli reduces expiratory flow by decreasing the elastic recoil present in healthy lung parenchyma. Destruction of the airspace walls is found upon histologic examination. Bullae, radiolucent areas larger than 1cm in diameter that indicate severe local destruction, may be seen in macroscopic examination and on radiographs.
One must be cautious in diagnosing COPD in the field as other disease states may also present with breathlessness, wheezing, and sputum production. Remembering the adage, “All that wheezes is not asthma,” may help keep a broadened differential.
Clinically, patients have chronic difficulty breathing that persists daily and is acutely exacerbated by an inflammatory stimulus such as an infection, allergens, or noncompliance with medications, etc. Differentiating asthma from COPD is sometimes difficult and the patient's age, medical and social history are typically helpful. Asthma patients may be younger at age of onset but that is variable. Most COPD patients will be older and may be thin, have pursed lip breathing (exhalation), as well as clubbed or stained fingertips from long-term smoking. However, many patients have both asthma and COPD. Both diseases will present with increased work of breathing, and variably cough and wheezing. Wheezing is the clinical hallmark of bronchospasm and a diagnostic sign in COPD and asthma that patients will benefit from bronchodilator therapy. However, be warned that in severe cases, patients may not be able to move enough air through the lungs to generate wheezing. Quiet lungs in the setting of respiratory distress is an ominous sign. Vital signs will commonly show an increased heart and respiratory rate as well as decreased oxygen saturations. Asthmatics can typically compensate and maintain near normal oxygenation until severe, whereas COPD patients are typically chronically hypoxic and may have low oxygen saturations at baseline.
Chronic treatment of both conditions involves inhaled bronchodilators and also the use of steroids to reduce chronic inflammation. Treatment in the acute setting is similar. The ABCs should be managed first and supplemental oxygen given. For patients at risk for immediate respiratory failure, assisting ventilations or intubation should be considered. In alert patients a trial of CPAP or BiPAP may be appropriate.14,15 In asthma, high flow oxygen can be utilized liberally. However, in mixed disorders or COPD, oxygen should be titrated to keep pulse oximeter readings between 92% and 95%. Prolonged high flow oxygen in COPD can suppress the hypoxic respiratory drive and has been linked to worsened long-term outcomes.
Bronchodilators such as albuterol (Ventolin) and levalbuterol (Xopenex) are the mainstays of prehospital treatment and can be given in a range of dosing based on severity from a “unit dose,” typically 2.5mg of albuterol to continuous nebulizer treatments lasting 30 minutes or more and delivering 10 to 20mg of albuterol in some cases. Providers should remember that in addition to bronchodilation, β-agonists have activity on the heart and can produce significant tachycardia and hypertension which can be harmful in some patients with cardiovascular disease. The patient should be monitored for high heart rate, significant hypertension, or signs of cardiac ischemia such as chest pain or ECG changes. Ipratropium bromide (Atrovent) is a nebulized medication adjunct that can be combined with. Atrovent works by reducing airway secretions and synergizing bronchodilatory medications. Atrovent is used primarily in the prehospital and ER setting and has been less effective in the inpatient chronic care setting.
Steroids and IV fluids are also a mainstay of treatment and can be given in a variety of doses and ranges. Chronic therapy is usually delivered via inhaled steroids. For acute treatment, methylprednisolone (Solu-Medrol) and dexamethasone (Decadron) are common choices. Whether administered orally, IV, or IM, these medications take around an hour or more for onset of action and do not offer immediate benefit. Additionally, IV volume replacement is an important consideration as most patients with respiratory distress are volume depleted from increased respiratory losses and reduced oral fluid intake.
Severe COPD and asthma that do not respond to conventional treatment may require other β-agents such as subcutaneous epinephrine, terbutaline, or in some cases an IV infusion of those medications. Again, this carries a risk of significant increases in cardiac demand.
Lastly, the patient with complete respiratory failure and severe alterations in mental status will require intubation. However, intubation should be considered the last resort for obstructive lung disease patients. Mechanical ventilation of COPD and asthma patients is difficult and perilous. Responders must remember that air trapping continues to occur and ventilation requires more time for exhalation. Normal intubated patients require approximately 1 second for inhalation and 2 seconds for exhalation, thus a 1:2 ratio. COPD and asthma patients may benefit from a ratio of 1:3 or more requiring slower ventilation rates and making oxygenation difficult. Continue aggressive treatment for bronchospasm even after intubation with in-line β-agonist nebulizer treatments and continued IV medications.16
PULMONARY EDEMA AND CHF PATHOPHYSIOLOGY
Just as gases can diffuse across the thin alveolar membrane in the lungs, so can fluids. However, in the case of fluids this is typically due to hydrostatic or osmotic forces. Any fluid, excluding pus/blood, in the lungs can be termed “pulmonary edema” although the term is classically used to describe fluid that enters the alveoli from the capillary circulation. Pulmonary edema has many causes ranging from heart failure to alveolar injury (such as in ARDS, inhalation injury, burns, etc) or overly aggressive resuscitation with IV fluids. Congestive heart failure (CHF) is a common cause of pulmonary edema encountered by EMS. The right heart pumps blood into the pulmonary circulation and an impaired left heart is unable to “pump out” blood from the right heart. The high pressure in the pulmonary circulation causes fluid to shift into the alveoli. Left-sided heart failure produces pulmonary edema and symptoms whereas right heart failure produces the peripheral signs of heart failure, leg swelling, etc. Most patients have impairment of both sides of the heart and left-sided heart failure in the United States is most commonly due to ischemic heart disease (CAD).
EMS providers may encounter patients with new onset or existing CHF. Exacerbations may come on abruptly or gradually worsen over several days. Patients with CHF may give a worsening history of the disease as well as weight gain or increased peripheral edema in the time period preceding the trouble. Frequently, poor adherence to medications, diuretics, or excessive fluid or salt intake can cause CHF exacerbations. Patients will typically appear with increased work of breathing and distress. Coughing may be present and may produce classic “pink frothy” sputum, giving them a nickname of “pink puffer.” Vital signs are highly variable depending on how poor the patient's cardiac function is. Heart rate and blood pressure can range from high to low. And oxygen saturations may be low or normal. The most complicated CHF patient is one who has significant respiratory distress paired with hypotension and bradycardia. This is a clear sign of a very sick heart and contraindicates many mainstays of treatment for CHF. The lung examination classically reveals coarse crackles in the lung bases, formally called rales. This sound is produced from fluid in the small airways.
The goal for CHF and pulmonary edema is fundamentally simple—get the fluid back into the circulation and out of the alveoli. The ABCs must be managed and if airway or breathing adequacy is questioned, CPAP, BiPAP, or intubation may be indicated.17,18 For pulmonary edema from a non-CHF source, that is, IV fluids, altitude, irritants, etc, treatment involves stopping the offending agent and using positive pressure ventilation. Every CHF patients should have supplemental oxygen and positive pressure ventilation via NIPPV. For the “warm” CHF patient—those with adequate heart rate and blood pressure—the addition of nitrates is indicated. A common prehospital regimen is up to three sublingual nitroglycerin tablets followed by some nitroglycerin paste administration. For advanced providers, establishing a nitroglycerin IV infusion is also an option that allows rapid titration of treatment. Remember to ask all patients about use of erectile dysfunction drugs such as Viagra or Cialis. For the “cold” CHF patient—those with bradycardia or hypotension—treatment is far more difficult. Oxygen can still be used but nitrates must initially be avoided and CPAP is questionable based on its tendency to reduce venous return and lower blood pressure. Intubation should be performed if airway patency and breathing are not adequate and once done, hypotension may need to be treated initially with judicious IV fluid boluses if any suspicion of “intravascular” volume depletion is present (ie, recent hx of vomiting, diarrhea, etc). Vasopressors may be needed to support blood pressure. Dopamine is a good choice because of its positive effect on blood pressure, heart rate, and cardiac contractility as well. Once blood pressure and heart rate are corrected, CPAP and nitrates can carefully be administered to help mobilize pulmonary edema.19
LUNG MALIGNANCY PATHOPHYSIOLOGY
Cancer remains the second most common cause of death in the United States and lung cancer remains in the top five malignancies.20 At present, EMS providers render care to a large geriatric population with a significant incidence of lung malignancy. Lung malignancy is mentioned in this chapter because it presents with a variety of features that cause respiratory distress, ranging from acute to more chronic. Malignancy can cause bleeding, inflammation, physical obstruction, and mass effects that all reduce functional lung capacity or cause other problems such as pulmonary edema or pneumothorax.
For many patients, a nagging cough, worsening shortness of breath, or hemoptysis (coughing up blood) may be the first signs that lead to a diagnosis of lung cancer. For others, worsening disease may produce symptoms that mimic obstructive lung disease, CHF, or predispose the patient to recurrent infections like pneumonia. For patients with existing lung malignancy, the clinical presentation is highly variable. The above features may produce COPD or CHF type symptoms with wheezing, rales or rhonchi, and increased work of breathing. Decreased immune function in the lungs can lead to infection with a clinical picture of pneumonia with sputum, fever, and worsening shortness of breath. Also, unlike some other respiratory illness, the malignancy can erode structures within the lungs. Spontaneous pneumothorax or erosion into blood vessels producing massive bleeding or hemothorax is possible. Patients may have massive hemoptysis (bloody sputum) that cannot be controlled and compromises the airway.
Treatment of symptoms is the best approach. Supplemental oxygen provides a great deal of comfort for most patients with lung malignancy. Albuterol or other bronchodilatory medications should be used for wheezing and steroids may have some role in reducing inflammation. Pulmonary edema treatment is best accomplished with CPAP as other measures that would work on CHF-like nitrates and diuretics are less effective. IV fluids and pain medication should also be considerations but not in amounts that will depress or labor breathing further. Intubation is indicated for complete respiratory failure but the EMS provider should ensure that the patient does not have a DNR order or specific directive against mechanical ventilation. Intubation may also be required for massive hemoptysis if the airway cannot be kept clear. Evidence of pneumothorax should be treated with pleural decompression of the affected side. In lung cancer patients who request palliative treatment, oxygen, CPAP, and pain medication is the mainstay of treatment.