Peptide Aids Diagnosis of Hypoxic Respiratory Failure

A new study has found that brain natriuretic peptide (BNP) levels are useful in ruling out cardiogenic pulmonary edema in patients admitted to the intensive care unit (ICU) with hypoxic respiratory failure.

Researchers at Piedmont Hospital (Atlanta, GA, US) sought to find out if BNP might also be useful in differentiating between acute respiratory distress syndrome (ARDS) and cardiogenic pulmonary edema. Eighty subjects with acute hypoxemic respiratory failure and bilateral pulmonary infiltrates who were undergoing diagnostic right-heart catheterization in the ICU were enrolled in the study. Those with conditions such as end-stage renal disease and acute coronary syndrome were excluded.

The results showed that BNP levels were significantly associated with mortality regardless of diagnosis and independently of the Acute Physiology and Chronic Health Evaluation II (APACHE II) score. Median BNP level was 325 pg/ml in patients who had acute lung injury or ARDS, and 1260 pg/ml in those with cardiogenic pulmonary edema. Higher levels of BNP were associated with decreased odds of ARDS. Using a cut-off point of 200 pg/ml or less resulted in a 91% specificity for ARDS, and a cut-off point of 1200 pg/ml or greater yielded a specificity of 92% for cardiogenic pulmonary edema. The study was published in the April 2007 issue of the journal Chest.

"The brain natriuretic peptide may be most useful for excluding cardiogenic pulmonary edema in the setting of hypoxemic respiratory failure in the ICU,” said lead author Dr. Dimitri Karmpaliotis. "Also, if the approach is validated in prospective studies, in some cases, measurement of natriuretic peptides may obviate the need for an invasive procedure.

APACHE II is a severity of disease classification system, one of several ICU scoring systems. After admission of a patient to an ICU, an integer score from 0 to 71 is computed based on several measurements; higher scores imply a more severe disease and a higher risk of death.


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