Assessment begins with a rapid, focused history and physical examination of the patient. This includes acute symptoms, recent illness, past history and prescribed medications, medication compliance, and diet. Together, this constitutes an important first step in the field diagnosis of AHF (Table 8.2). Critical elements of the physical examination include accurate determination of vital signs. Prehospital providers, even in the absence of peripheral edema, should strongly consider cardiogenic pulmonary edema in patients presenting with acute respiratory distress, hypoxemia, tachypnea, rales or wheezing, and marked hypertension. Such patients often have histories of poorly controlled hypertension and/or prior cardiac disease. Blood pressure of greater than 180/120 mmHg is common in this setting and is a good sign of reversibility. In these patients, a rapid reduction in blood pressure often produces prompt relief of respiratory distress. Marked hypertension associated with acute respiratory distress and wheezing, particularly in elderly patients without a history of asthma or pulmonary infection, is strongly suggestive of AHF. Such a presumptive diagnosis may be supported by the presence of cardiovascular medications and the absence of respiratory medications, such as metered-dose inhalers. Even when these facts are present, out-of-hospital personnel should always consider alternate etiologies such as pulmonary embolism, pneumonia, COPD and asthma, and drug overdose before diagnosing patients as having APE. Cardiac rhythm monitoring and 12-lead electrocardiograms (ECGs) are essential in patients suspected of AHF, particularly for identifying arrhythmia and/or acute coronary syndrome that may be the inciting event, and should be placed on the patient shortly after arrival on the scene.

A 12-lead ECG should be obtained on all patients to ascertain the presence of acute and/or chronic cardiac changes that may be creating or contributing to the current episode.

In addition to the ECG, a number of other diagnostic aids have been developed to improve accuracy in the evaluation and diagnosis of AHF. Although not currently used in the prehospital environment, a rapid bedside assay of blood levels of B-type natriuretic peptide (BNP) is now available. BNP is a neurohormone secreted mainly by the cardiac ventricles in response to volume expansion and pressure overload which rises in the setting of acute heart failure [15–20]. Application of such testing in the out-of-hospital environment may be a logical extension and further aid in diagnosis. Noninvasive cardiac output (NICO) devices, such as impedance cardiography [21, 22], have also been suggested as diagnostic tools, but their complexities and cost have to date precluded their out-of-hospital use.

APE is often difficult to distinguish clinically from an exacerbation of chronic obstructive pulmonary disease (COPD) or other acute pulmonary disorders. The misdiagnosis of AHF in the out-of-hospital setting has been documented to be 23 % in one study [23] and 32 % in another [24]. The need for the correct identification of precipitating events, and the rapid initiation of appropriate treatment, is critical to achieve a positive outcome. Inappropriate therapy, as a result of misdiagnosis, may result in harm to the patient. Hoffman and Reynolds reported that adverse effects were more common in misdiagnosed patients. Untoward effects included (a) respiratory depression in patients receiving morphine, (b) hypotension and bradycardia in patients receiving both morphine and nitroglycerin, and (c) hypotension and arrhythmias associated with hypokalemia in patients receiving furosemide.

An understanding of the scope of practice of EMS providers is critical to the discussion of the interventions that might be utilized in the prehospital care of AHF. While some countries, primarily European, staff their EMS with physicians and nurses, the majority of countries use individuals with limited and specific training in out-of-hospital care of the acutely ill and injured.

Although there is some degree of variability in differentiation, most of the western hemisphere and Australia utilize a tiered level of providers who at entry have the training and equipment to provide basic life support care for cardiac arrest and provide first aid care to victims of trauma and those complaining of chest pain and respiratory distress. The highest qualification of training includes the ability to administer drug therapy and utilize advanced airway techniques. For purposes of illustration, the US EMS scope of practice will be presented.

The United States has adopted the National Scope of Practice for EMS providers, a document created by the National Highway and Traffic Safety Administration in 2007. This describes four levels of prehospital providers. The first level, the emergency medical responder (EMR), was previously titled the first responder. This provider is trained in CPR and the use of the automatic external defibrillator (AED), as well as basic first aid, including oxygen administration and care of simple trauma. They are not associated with transportation of the patient by ambulance.

The following are the minimum psychomotor skills of the EMR:

The next level is the emergency medical technician (EMT). This provider has the capabilities of the EMR, in addition to noninvasive monitoring and assisting the patient with the administration of their own medications. This level of provider is given minimal education in pathophysiology, and their treatments are primarily driven by patient complaint and symptoms. As for airway management, some states currently allow this level to place blind insertion airway devices (BIAD) such as the King LT or Combitube. This level of provider is the minimum allowed to transport the patient in an ambulance.

The following are the minimum psychomotor skills of the EMT:

The next level, the advanced EMT (AEMT), is able to establish an intravenous line and administer a limited list of medications. Many states currently allow the EMT to administer many of the medications listed only for the advanced EMT.

The following are the minimum psychomotor skills of the AEMT:

The highest defined prehospital provider level is the paramedic. This level is permitted to administer the widest range of medications and procedures which are usually limited only by medical director authorization and in some instances state rule.

The following are the minimum psychomotor skills of the paramedic:

Due to the significant variability in scope of practice by the four EMS levels of training, the ability to provide care for the patient with AHF is limited by state or local implementation of this scope of practice model and the willingness of an EMS medical director to authorize various treatment modalities.

At first blush, the National Scope of Practice model would appear to limit the administration of nitroglycerin for AHF only to paramedics. This would limit care for many persons living in areas with only basic life support EMS response, which is often the case outside urban areas. However, since the EMT may assist the patient with administration of their own medications, and it is reasonable to assume that a large number of AHF patients would have NTG prescribed by their physician, EMS personnel will be able to help assure properly aggressive treatment with NTG.

Continuous positive airway pressure (CPAP) ventilation involves the administration of oxygen via a positive pressure device for spontaneously breathing patients. The EMT is allowed to assist a patient’s ventilations with a BVM and to provide positive pressure ventilation to the cardiac arrest victim. The application of CPAP has proven clinical benefit, is arguably easier than ventilating with a BVM, and has a similar or lower risk of adverse effects, so an increasing number of areas do allow EMTS to utilize this modality.

For the medical director of a paramedic service, the greatest challenge has been to adopt treatment protocols based on the current understanding of the pathophysiology of AHF. Traditionally, the use of diuretics by EMS has been commonplace, and the role of nitroglycerin has not been well accepted. Many service protocols include the administration of morphine for AHF despite no data to support its use. Further, some services that include NTG in their protocols are extremely conservative, allowing paramedics to administer NTG in a manner more appropriate for angina than the high adrenergic state of AHF. Some also rely too heavily on the transdermal route of NTG despite the poor pharmacodynamic properties of this route.