"steal" phenomenon of inhaled nitric oxide (iNO)

"steal" phenomenon of inhaled nitric oxide (iNO)

iNO is frequently used as a rescue therapy in patients with no underlying pulmonary hypertension but who develop severe pneumonia or acute respiratory distress syndrome (ARDS). Although evidence is weak regarding any mortality benefits, it certainly provides breathing space for a clinician to provide more proven modalities like extracorporeal membrane oxygenation (ECMO). This benefit of iNO has been utilized frequently by clinicians during the COVID-19 pandemic.

iNO improves oxygenation by a phenomenon known as "steal" phenomenon. Contrary to popular belief, iNO has a relatively small effect on ventilation-perfusion (V/Q) mismatch by vasodilating the pulmonary vascular bed. The larger improvement in hypoxemia comes from the "steal" phenomenon in lung parenchyma by decreasing the intra-pulmonary shunt in areas less perfused. This also explains the immediate improvement in hypoxemia while patients are prone, particularly when obese. iNO and prone position, when combined, can have a highly synergistic effect.

#pulmonary 

#ARDS

Reference:

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2. De Wet CJ, Affleck DG, Jacobsohn E, et al. Inhaled prostacyclin is safe, effective, and affordable in patients with pulmonary hypertension, right heart dysfunction, and refractory hypoxemia after cardiothoracic surgery. J Thorac Cardiovasc Surg 2004; 127:1058.

3. Rossaint R, Falke KJ, López F, et al. Inhaled nitric oxide for the adult respiratory distress syndrome. N Engl J Med 1993; 328:399.