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Syncope, hypoxemia, jugular venous distention, acute right heart strain on ECG, dilated right ventricle on portable echocardiogram.

The physical exam may be enhanced by point‐of‐care ultrasound of the chest in the patient with acute respiratory distress. Ultrasound can help differentiate many conditions, including acute pulmonary edema, pneumothorax, pleural effusion, pericardial effusion, and pneumonia. (See Chapter 69.) B‐lines, which are vertical lines extending from the pleural line to the bottom of the ultrasound image, are indicative of the interstitial lung fluid that is present in ADHF and SCAPE [9]. An absence of lung sliding on the affected side is highly sensitive and specific for the detection of pneumothorax [10, 11].

Figure 5.1 Normal capnographic waveform

Capnography plots the concentration of exhaled CO₂ throughout the respiratory cycle and provides a continuous assessment of metabolism, circulation, and ventilation. A normal capnogram is shown in Figure 5.1. End‐tidal CO₂ (EtCO₂) refers to the concentration of CO₂ at the end of exhalation. The displayed EtCO₂ value represents the highest measurement in a ventilation cycle, which, under a normal physiological state, is between 35 and 45 mmHg. Waveform capnography has become the criterion standard for confirming correct endotracheal tube placement and assessing for effective ventilation with advanced airways. It also a valuable noninvasive method for continuously monitoring a spontaneously breathing patient’s ventilatory and circulatory status.

^{Capnography can be used to monitor the response to treatment in some patients. With asthma and COPD, small airway obstruction leads to prolonged expiration and a “shark fin” appearance of the capnogram [12, 13]. Normalization of the capnograph waveform indicates favorable response to treatment. Alternatively, increasing EtCO}₂ ^{levels may be indicative of worsening respiratory failure in these patients.}

^EtCO ₂ ^{may help differentiate the causes of respiratory distress. Lower EtCO}₂ ^{levels may be more likely to be associated with a diagnosis of ADHF rather than COPD [14]. In patients with hyperglycemia, prehospital EtCO}₂ ^{levels were significantly lower in patients eventually diagnosed with diabetic ketoacidosis [15].}