Pulmonary edema is a clinical phenomenon where fluid accumulates in the alveoli in the lungs, resulting in impaired oxygen exchange and shortness of breath.  Although pulmonary edema is associated with a number of clinical problems, in the prehospital environment it is most commonly the result of congestive heart failure (CHF).  Impairment of ventricular function causes blood to accumulate in both the pulmonary and systemic circulation. Pulmonary edema as a result of CHF may develop slowly, over days, or very suddenly (also known as “flash” pulmonary edema).  Treatment options for pulmonary edema depend heavily on underlying cause, so careful assessment is required.

• To the maximum extent possible, paramedics should attempt to determine the origin of the fluid and differentiate between cardiogenic pulmonary edema, asthma, pneumonia, or chronic obstructive pulmonary disease.
• Consider cardiogenic shock if the patient has a history of cardiac dysfunction, or if chest pain is present with hypotension, an altered level of consciousness, pale and cool skin, and/or decreased urine output.
• Position patients to limit venous return.  Be aware that many patients with pulmonary edema will be unable to tolerate a supine or semi-recumbent position.  Respiratory arrest may follow if patients are forced to lie down. 
• Patients with impending respiratory failure – i.e., those whose respiratory rate and/or tidal volume are decreasing, and whose level of consciousness is falling – must be ventilated with a bag-valve mask (including a PEEP valve, if indicated).

• Cardiogenic pulmonary edema is often accompanied by significant hypertension.  Nitroglycerin decreases systemic vascular resistance through a number of mechanisms.  The decision to use nitroglycerin is complex and requires a thorough understanding of the pathophysiology of the underlying condition, and an assessments of multiple clinical variables.  There are significant risks to the use of nitroglycerin in these cases. 
• CPAP is a form of non-invasive device that uses positive pressure to improve oxygenation, and is very effective in cases of pulmonary edema, regardless of underlying cause.  The greatest benefits of CPAP accrue from its use early in the disease course; paramedics should consider the use of CPAP as soon as pulmonary edema has been identified. 

• Pulmonary edema is not solely caused by congestive heart failure.  Exposure to toxic products (including smoke and bleach or chlorine) can produce primary pulmonary edema due to epithelial damage; pulmonary edema can also occur as a result of drug ingestion or submersion and drowning.  These patients are generally not hypertensive, do not have a history of heart disease, and have a history of exposure.  Although the in-hospital treatment of these patients is different from those with cardiogenic pulmonary edema, the principles remain the same: oxygen, supportive ventilation as required, and rapid transport.  CPAP can be effective in these cases.
• Early stage pulmonary edema may present as wheezing (“cardiac asthma”).  Salbutamol may alleviate some of these symptoms, however, the wheezes in these cases are associated with airway edema rather than bronchospasm.  Salbutamol has sympathomimetic properties that increase the workload of an already dysfunctional heart.  The risks and benefits of salbumatmol use must be considered for each individual patient. 
• Diuretics are no longer considered a mainstay of prehospital treatment for pulmonary edema.
• Some patients with pulmonary edema will require bag-valve mask ventilation, particularly after position changes.  Paramedics must be prepared to intervene during or immediately after a transfer, and should strive to minimize patient exertion during these maneuvers. 
• Patients in respiratory failure, or who otherwise do not improve with CPAP, should be ventilated using a bag-valve mask.  The use of positive end-expiratory pressure (PEEP) valves may be effective in improving both oxygenation and ventilation in these patients. 

Pulmonary Edema (CHF)

1. Alberta Health Services. AHS Medical Control Protocols. 2020. [Link]
2. Ambulance Victoria. Clinical Practice Guidelines: Ambulance and MICA Paramedics. 2018. [Link]
3. Gray A, et al. Noninvasive ventilation in acute cardiogenic pulmonary edema. 2008. [Link]
4. Purvey M, et al. Managing acute pulmonary oedema. 2017. [Link]
5. Tintinalli JE, et al. Tintinalli’s emergency medicine: A comprehensive study guide. 9th. 2019.