Acute asthma attack is a common cause of admission to emergency departments (EDs) among children, and triage by severity is important for determining appropriate clinical treatment.[2,3] Noting that PVi has been shown to be an accurate method for measuring the degree of pulsus paradoxus,[4,5] a reduction in systolic blood pressure associated with obstructive respiratory tract disease, the authors sought to understand whether PVi might be of assistance to ED clinicians needing to make rapid triage decisions in such cases. They enrolled 133 patients between the ages of 2 and 18 (median age 5 years old) who arrived at the ED between May 2020 and July 2021 with a diagnosis of asthma attack or reactive respiratory tract disease. During initial examination and after treatment, patients’ PVi levels were measured using Masimo Radical-7® Pulse CO-Oximeters®. Severity of the asthma attack/respiratory disease was graded using the Pulmonary Index Score (PIS). Treatment decisions, including to hospitalize or to discharge, were made by clinicians who were blinded to PVi values.

The researchers found that PVi values, both before and after treatment, were significantly higher in patients with “severe” disease, compared to “mild” or “moderate” disease (p < 0.001): “Severe” patients had median PVi values of 47% (42 - 51) before treatment and 38% (32 - 44) after treatment; “moderate” patients, 31.5% (26 - 39) before and 25% (20 - 29) after; and “mild” patients, 24% (19 - 27) before and 19.5% (17 - 22) after. PVi values were also significantly higher for patients who were hospitalized, compared to those who were discharged from the ED (p < 0.001): Hospitalized patients had median PVi values of 46.5% (39 - 49) before treatment and 38% (29 - 44) after treatment; discharged patients, 26% (22 - 34) before and 21% (18 - 26) after. For all severity levels, post-treatment PVi values were significantly lower than pre-treatment values (p < 0.001). The researchers calculated a pre-treatment PVi cut-off level of 37.5% for predicting whether a patient had “severe” disease (68.75% positive predictive power, with 100% sensitivity and 85% specificity, p < 0.001) and would require hospitalization (72.34% positive predictive power, with 91.89% sensitivity and 71.74% specificity, p < 0.001).

The authors concluded, “The severity of attacks of many patients who apply to the pediatric emergency department because of an attack due to obstructive respiratory tract diseases can be accurately defined with certain clinical evaluation tools. Although PIS is a very important tool for assessing attack severity, it includes some subjective parameters. Automatic PVi measurement can be useful in intensive emergency department conditions, especially in triage, in terms of predicting the response of patients to treatment and follow-up results by quickly determining the severity of attacks, and in terms of reducing subjective clinical decision variations among physicians. This is because it provides objective data.”

In the U.S., PVi is cleared as a noninvasive, dynamic indicator of fluid responsiveness in select populations of mechanically ventilated adult patients.