Dyspnea is unique in its universal significance. No activity may be continued in the face of mounting dyspnea, and ultimately nothing is more important than not being able to breathe. When asked “what would make you go to the emergency department?”, the surprisingly short list is either dyspnea or pain. But dyspnea is dominant and is the reason that it is one of the most common presentations to the emergency department.
Like pain, dyspnea is subjective. And like pain, precise measures to accurately and objectively determine its severity simply do not exist. Therefore, to evaluate the effect of treatment on its relief, recording the patient's perception of their symptoms may provide utility. A common technique to rate and track dyspnea is the Visual Analog Scale (VAS). This is performed by having a patient indicates their degree of discomfort by drawing an indicator on a 0–100 mm line (Fig. 1).
Although not validated for dyspnea, data from the pain literature data suggests that a clinically relevant change should be more than 13 mm. This method records the patient's perception of dyspnea at the moment the scale is administered. Alternatively, a second technique is commonly used that evaluates temporally relative dyspnea changes. This is performed by asking the patient, “compared to a prior time (e.g., emergency department presentation), how have your symptoms changed”. Box 1 demonstrates potential responses. It should be noted that, while it is still useful to evaluate therapeutic impact, relative scales cannot evaluate dyspnea at presentation and are limited as they tend to be less sensitive for smaller dyspnea changes than VAS scoring.
Although dyspnea may be the result of normal physiologic processes (e.g., strenuous activity), it is also the final common symptom of many potentially fatal events (Table 1). Irrespective of its cause, failure to ventilate or oxygenate sufficiently to meet the metabolic needs of the corpus results in dyspnea. Because the list of causes is long, overlapping, and complicated, it is the emergency physician's challenge to rapidly identify and reverse the primary cause of dyspnea. To further increase the complexity of the task, relatively harmless mimics, such as anxiety, can present with profound dyspnea. This last caveat represents a serious diagnostic challenge, especially when a patient is older and at risk for potential fatal comorbidities that are likely to be present.
Vital signs are vital, and must be measured as soon as feasible after presentation. They represent the earliest objective measure of the extent of distress. While extremely insensitive when near normal, increasing deviations are associated with a logarithmically increased risk of a serious underlying event. When evaluating respiratory status, extremely slow respiratory rates (e.g., <6 respirations/min) represent a premorbid condition, with immediate therapeutic intervention necessary (e.g., endotracheal intubation, naloxone, etc.) to obviate a fatality. An algorithmic approach to etiologic considerations in the nonapneic patient is shown in figure 3.
Conversely, while very high respiratory rates (>30 respirations/min) can be tolerated initially, they cannot be maintained for long periods and will ultimately lead to respiratory failure if prompt intervention does not correct the underlying pathology. When respiratory rates are near normal, pulse oximetry may aide in providing objective measures of the oxygen transport capability. However, oxygen delivery must be considered in context of hemoglobin concentration, as tissue hypoxia may exist in the setting of low hemoglobin. Ultimately, any oxygen saturation below 90% should prompt an immediate evaluation and corrective interventions.
Pulse oximetry is a rapid, noninvasive, inexpensive, objective measure of the total function of the body's oxygen delivery system and it suffers from several caveats. Abnormalities of hemoglobin from some toxins (e.g., cyanide and carbon monoxide) may present as having normal oxygen transport capability when in fact tissue oxygen delivery is distinctly impaired. Further, the presence of adequate oxygenation does not reflect on ventilatory status, which must be considered independently.
Measurement of the blood pressure can be extremely useful in determining the underlying etiology in a patient presenting with dyspnea. Hypertension, associated with jugular venous distention (JVD) and rales, is highly suggestive of acute pulmonary edema, and treatment to rapidly lower the blood pressure may be highly effective at resolving dyspnea. This is true regardless of the type of heart failure (HF) (reduced or preserved ejection fraction), even with blood pressures as low as 140 mmHg. In patients with lower blood pressures, few signs volume overload, and with wheezing on auscultation, chronic obstructive pulmonary disease is a more likely diagnosis.
Fig. 3: An approach to the patient presenting with acute severe dyspnea. The patient's process of breathing should be observed for several respiratory cycles. If afterward the physician is assured at least a modicum of time is available before immediate endotracheal intubation is required, the algorithm may be considered. While it is presented in a stepwise fashion, the entire process is performed in less than 15 seconds, while listening to the lung sounds
Finally, if the blood pressure is very low (e.g., <90 mmHg) in the setting of HF, immediate intervention is required, as the mortality rate in this patient phenotype approximates 70%.
When patients present with dyspnea, watching the mechanics of breathing can provide extremely useful information and should be performed as soon as possible after arrival. The parameters to consider include the depth of inhalation, the respiratory pattern, and how much effort the patient is expending. While the normal pattern of breathing is an apparently effortless inhalation or exhalation with a timing relationship of 1:3, alterations of this pattern can provide an early diagnosis. While inhalation wheezing suggests upper airway pathology (e.g., foreign body and anaphylaxis), prolonged expiration is consistent with lower respiratory tract obstruction secondary to asthma or chronic obstructive pulmonary disease.
The depth of breathing can suggest changes in minute ventilation (minute ventilation = tidal volume × breaths/minute). Increased minute ventilation can occur as respiratory compensation for metabolic acidosis from any cause, is also seen with anemia, or may be the result of severe anxiety.
Determining the work of breathing is important as extreme exertion will not be tolerated for prolonged periods. The presence of accessory muscle use, sitting in an upright position, and concurrent abdominal muscle use are each consistent with increased breathing effort, as is the number of words that the patients may speak between breaths. If diaphoresis is present secondary to the effort of breathing, the patient is likely to tire quickly and must be rapidly addressed. Finally, nonpulmonary observations may suggest the cause of dyspnea, e.g., persistent JVD is consistent with HF, tension pneumothorax, or pericardial tamponade.
As the physical examination provides very useful diagnostic information, after the vital signs have been measured and the respiratory status observed, if immediate treatment (e.g., endotracheal intubation) is not required, it should be performed. This begins by noting odors (e.g., spearmint suggests severe metabolic acidosis from aspirin poisoning with an oil of wintergreen ingestion) and touching the skin to determine the presence of fever (as may occur with pneumonia or sepsis), or if the patients is cold and wet from compensatory peripheral vasoconstriction (as may occur with acute pulmonary edema or in the setting of shock).
Pulmonary auscultation is useful to assist in determining the etiology for dyspnea. Asymmetric findings are consistent with asymmetric pathology (e.g., pneumonia, pneumothorax and pleural effusion). Although the detection of basilar rales is not diagnostic of a specific pathology, their extent may be related to the severity of the presentation. Finally, thoracic percussion may diagnose a pleural effusion when breath sounds are distant or absent.
Finally, inspection of the naked patient may also suggest a diagnosis. Notation of the presence or absence of JVD, abdominal distention (consistent with ascites), or peripheral edema (and its symmetry) can suggest the underlying cause of dyspnea.
While laboratory investigations can be extremely useful, in the severely ill patient, the focus should be on the obtainable history and physical exam. Even point of care labs take some amount of time to perform and usually only confirm a suspected diagnosis. In the acutely ill patient, treatment should not be delayed pending lab results. In those with less acute severity at presentation, and an intervention can be postponed without harming the patient, specific labs may be helpful. These may consist of measuring troponin, natriuretic peptides, or D-dimer in selected cases. Chemistry analysis may aid in risk stratification and impact diagnostic strategies (e.g., an elevated creatinine may preclude a computed tomographic angiogram), as well as identify iatrogenic complications of outpatient therapy (e.g., hypokalemia and digoxin toxicity).
Finally, while arterial blood gas may determine acid-base status and guide ventilator parameters, they are rarely of diagnostic assistance in the acute setting. They should not be used to evaluate the airway or the need for intubation at the acute presentation. Although they may be helpful later in the patient's clinical course, at presentation the time used obtaining an arterial blood gas sample is better spent performing the clinical assessment and initial interventions.
Bioimpedance Vector Analysis
Bioimpedance vector analysis is a technology for determining total body water by the measuring the electrical conductive properties of the body. It provides rapid, noninvasive, inexpensive, reproducible, and objective results that correlate with total body water, diuretic therapy need, and the likelihood of the necessity for hospitalization from the emergency department. Although knowledge of total body water volume is not diagnostic in itself (as many pathologies are associated with increased total body water), when it is considered in combination with other bedside and lab findings, it has been shown to improve diagnostic accuracy.
Chest X-rays are a very useful investigation, although they do suffer from a number of limitations (e.g., their findings may be delayed relative to the patient's presentation, they can be insensitive when done using a portable technique, they require radiation exposure, and are relatively more expensive than other procedures). Their significant advantage is that they can be performed rapidly and at the bedside. A normal chest radiograph in the setting of acute dyspnea should result in a marked change the differential diagnosis, if acute heart failure was initially suspected.
Lastly, the pulmonary computed tomography angiogram has become routine for evaluating suspected pulmonary embolism. It is very helpful in the acutely dyspneic patient, if the clinical diagnosis is likely acute pulmonary embolism. However, the pretest probability of the presence of a pulmonary embolism should be considered by using the Well's criteria (Table 2). Patients with higher scores should undergo scanning, while those a low score (<3) and a negative qualitative D-dimer test do not require further pulmonary embolism work up. Patients who are severely ill, hemodynamically unstable, and too dyspneic to lay flat are not computed tomography evaluation candidates and may best be served initially by empiric treatment.
When performed at the bedside by the emergency physician, ultrasound is a rapid, noninvasive and inexpensive measure to aid in determining the cause of dyspnea. It can evaluate for a possible pneumothorax, inform about cardiac contractility, and diagnose a pericardial effusion (Fig. 2). Lung ultrasound can help differentiate HF and chronic obstructive pulmonary disease by identifying B-lines, and it can detect volume overload by direct lung imaging or by observing the failure of vena cava diameter changes that normally occur during the respiratory cycle.
Dyspnea, the most common reason for patients with acute heart failure to present to the hospital, is the final common pathway for a large number of potentially fatal pathologies. Determining if an immediate airway intervention is necessary is defined by the acuity of the presentation and the diagnostic certainty of the practitioner. When severe, initial clinical decisions may be entirely based upon vital signs, the physical exam, and patient distress. However, if the patient is more stable and can tolerate investigations before therapy is initiated, then selected tests, bioimpedance measures, ultrasound, or radiographic testing may be considered to assist in limiting the differential diagnosis and increase diagnostic certainty.
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