may occur. Be especially suspicious if there are signs of

unilateral leg swelling. Entertain the thought of pulmonary embolism in any patient who is short of breath,

especially if the cause of dyspnea is unclear.

DIAGNOSTIC STUDIES

Diagnostic studies will vary based on the clinical presentation and physical exam.

� Laboratory

Pulse oximetry is a rapid, noninvasive test that is useful

to screen for hypoxia. An Sa02 >98% predicts a Pa02 >80

mmHg. An Sa02 >90% predicts a Pa02 >60 mmHg. This is

important because an Sa02 of 90% is at the precipitous edge

of the oxygen dissociation curve; the patient may drop from

90% to 70% far quicker than from 95% to 90%. An arterial

blood gas is the only way to directly measure the Pa02 and

the pCO r The pCO 2 is useful in the management of patients

with chronic obstructive pulmonary disease, asthma, or

sleep apnea. The complete blood count can help in assessing

whether anemia is a cause of dyspnea. A metabolic panel

can elucidate the patient's renal status as well as give further

information about the patient's acid-base status (bicarbonate). Blood cultures are important in cases of pneumonia.

Remember to obtain before starting antibiotics.

� Electrocardiogram

ECG is useful to assess for cardiac ischemia, arrhythmias,

and even pericarditis or pericardial effusion.

� Imaging

CXR can help to assess the bronchial tree, alveoli, and

interstitium. It is also useful for evaluating bony structures,

the mediastinum, heart silhouette, and even aberrations of

the pleural space. Chest CT can be useful to assess mass

lesions, consolidations, effusions/exudates or pulmonary

emboli. Soft tissue plain radiograph or CT of the neck can

be used in stable patients to determine the presence of

epiglottitis, foreign body, or neck abscesses.

MEDICAL DECISION MAKING

As stated previously, the first goal of a dyspnea work-up

is to determine whether the patient is in extreme respiratory distress. If the patient is unable to oxygenate, ventilate, or preserve the airway, the patient must be intubated

immediately ( question 1). Next, if the patient has signs

of a reversible cause of dyspnea, such as asthma, CHF,

anaphylaxis, or tension pneumothorax, initiate treatment as soon as possible (question 2). Finally, once the

patient is stable, begin the diagnostic work-up (question

3, begin walking down respiratory system anatomically)

(Figure 20- 1).

ABCs

IV, 02, mon itor, pulse

oximetry, lung exam

Answer 1:

Can patient

No oxyg enate, ventilate,

maintain airway?

Yes

DYSPNEA

Hypoxic? � g ive oxygen Answer question 2:

Is the cause of

severe respiratory

d istress rapidly

reversible?

Yes Bronchospasm? � beta-agonists vs. steroids vs. epinephrine

-----� Hypertensive pulmonary edema?� nitroglycerin, lasix

Pneumothorax?� needle decompression, chest tube, etc .

Allergic reaction? � steroids vs. epinephrine

No, and

unstable

No immediate

i nterventions

available/necessary

Answer question 3:

Can the patient run?

Yes

Obtain history from

patient, family,

careg ivers

Walk anatomically down

respiratory system

-ECG

-Radiographs/CT

-ABG, labs