Introduction
Physical Examination
General
Cyanosis
Labored respirations
Tachypnea
Chest wall retractions
Nasal Flaring
Coughing/Sneezing
Grunting
Stridor
Differential Diagnosis
Specific Diseases
References
Other Lectures
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Cyanosis, while the most dramatic sign, has some inherent limitations as a diagnostic tool. Its presence requires the circulation of at least 4-5 gm% of reduced hemoglobin. A child with severe anemia, therefore, may have significant hypoxemia without manifesting cyanosis. Conversely, a very young infant whose hemoglobin has not yet fallen from the normally high levels found at birth and whose peripheral circulation is normally somewhat sluggish may show varying degrees of peripheral cyanosis despite a normal pO2.
Another limitation of cyanosis is that, even when present, it is a late accompaniment of respiratory disease. And the degree of cyanosis does not necessarily correlate with the severity of disease; in other words, it is extremely difficult to differentiate "moderate" from "severe" cyanosis. In addition, of course, there are many non-respiratory tract diseases, chiefly cardiac and hematologic, that also produce cyanosis. Finally, the presence of cyanosis does not localize the disease to a particular part of the respiratory tract.
For all these reasons, cyanosis is of limited diagnostic value. However, when present, it is an extremely important and ominous sign.
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