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 v

volume may not be achieved. On the physical exam, gross

asymmetric chest wall expansion or abdominal distention/ascites can be clues of diaphragmatic dysfunction or

impairment. Look for asymmetric diaphragmatic excursion on a good inspiratory CXR.

Chest wall. Chest wall expansion is important for

unimpeded respiration. Any disorder that restricts wall

motion may cause dyspnea (ie, paresis/paralysis, neuro ­

muscular junction or muscular dysfunction, pain from

contusion or rib fractures). Do not underestimate splinting from chest wall pain-even from apparently minor

injuries. Inspection of the chest wall during respiration will

help you to assess this aspect of breathing. Use CXR to look

for rib fractures and/or pulmonary contusion (haziness at

site of trauma).

Pleural space. The pleural space is a potential space

present to facilitate movement of the lungs within the

chest wall. If the space is filled with fluid (ie, effusion, pus,

blood) or air, dyspnea can occur. If the pleural space is

occupied, it will typically cause decreased breath sounds

on the effected side. Fluid causes decreased resonance,

whereas air causes increased resonance. Abnormalities

will typically be seen on CXR; the addition of a lateral

decubitus radiograph of the chest may be helpful. Look

for extra-lucent edges that indicate a pneumothorax and

lenticular, dependent, or meniscal opacifications

consistent with an effusion.

Cardiac. The heart pumps deoxygenated blood to the

lungs and oxygenated blood to the tissues. Any impairment

of pump function (ie, ischemia, dysrhythmia, valvular

dysfunction, septal defects, pericardial fluid) can cause

dyspnea. Do not hesitate to initiate relevant cardiac workups when a patient presents with dyspnea. On the physical

exam, assess for cardiac murmurs, gallops, and rhythm

aberrations. These are important clues to expand the differential to cardiac problems.

Hemoglobin. There must be enough healthy red blood

cells to carry the oxygen to the tissues (ie, no significant

anemia), and the hemoglobin must be unadulterated so

that oxygen can bind in the lungs and release at the tissues

(ie, no CO or CN poisoning). A lack or impairment of

hemoglobin can also manifest as dyspnea. Consider a stool

guaiac exam if there is any clinical or historical signs of

anemia (eg, pallor, cachexia). Replete with a blood transfusion as necessary.

Blood volume. Adequate circulating volume is necessary to deliver red blood cells to the lungs and then distribute them throughout the body. Determine the volume

status by assessing vital signs, pulses, mucus membranes,

skin turgor, amount of secretions, etc.

Blood vessels. Blood must be able to flow freely to all

parts of the lungs to pick up oxygen. A PE may obstruct

blood flow to lung tissue and effect gas exchange, resulting in dyspnea. Unfortunately, the physical exam may

not reliably assist with this diagnosis, although wheezing