THORACIC AND RESPIRATORYDISORDERSCyanosis
Cyanosis is a bluish discoloration of the skin due to the presence of deoxy-
genated hemoglobin (deoxyhemoglobin or abnormal hemoglobin) in skin
capillaries. It is generally detected when there is 5 g/dL (absolute level) of
deoxygenated hemoglobin in the circulating capillary blood, although it can
sometimes be detected at lower levels. The presence of cyanosis suggests (but
does not diagnose) tissue hypoxia.
Central Cyanosis
■ When abnormal or deoxygenated hemoglobin is circulated
■ Causesinclude:
■ R to L cardiac shunt
■ V/Q mismatch (eg, PE, polycythemia)
■ Impaired diffusion (eg, interstitial fibrosis)
■ Hemoglobinopathy (eg, methemoglobinemia)
■ Toxins (eg, cyanide)
■ Polycythemia
■ High altitude
Peripheral Cyanosis
■ This is due to slowing of flow of normally oxygenated hemoglobin to the
extremity or extremities resulting in ↑O 2 extraction.
■ Causes include shock and arterial/venous obstruction (eg, thrombus, vaso-
constriction).
SYMPTOMS/EXAM
■ Central cyanosis is best seen on perioral skin, oral mucosa, or conjunctivae.
■ Look for symptoms/findings that suggest an underlying cause (eg, LE
cyanosis, hypotension, and abdominal pain in ruptured AAA, murmur and
central cyanosis in cardiac shunt).
TABLE 10.2. Causes of Wheezing
Upper airway (more likely to be stridor, may have element of wheezing)
Angioedema: allergic, ACE inhibitor, idiopathic
Foreign body
Infection: croup, epiglottis, tracheitis
Lower airway
Asthma
Transient airway hyperreactivity (usually caused by infection or irritation)
Bronchiolitis
COPD
Foreign body
Cardiovascular
Cardiogenic pulmonary edema (“cardiac asthma”)
Noncardiogenic pulmonary edema (ARDS)
Pulmonary embolus (rare)
Psychogenic(Reproduced, with permission, from Tintinalli JE Kelen GD, Stapczynski JS. Emergency Medicine:
A Comprehensive Study Guide, 6th ed. New York: McGraw-Hill, 2004:440.)