Prospective application of clinician-performed lung ultrasonography during the 2009 H1N1 influenza A pandemic: distinguishing viral from bacterial pneumonia

Abstract

Background: Emergency department visits quadrupled with the initial onset and surge during the 2009 H1N1 influenza pandemic in New York City from April to June 2009. This time period was unique in that >90% of the circulating virus was surveyed to be the novel 2009 H1N1 influenza A according to the New York City Department of Health. We describe our experience using lung ultrasound in a case series of patients with respiratory symptoms requiring chest X-ray during the initial onset and surge of the 2009 H1N1 influenza pandemic.

Methods: We describe a case series of patients from a prospective observational cohort study of lung ultrasound, enrolling patients requiring chest X-ray for suspected pneumonia that coincided with the onset and surge of the 2009 H1N1 influenza pandemic.

Results: Twenty pandemic 2009 H1N1 influenza patients requiring chest X-ray were enrolled during this time period. Median age was 6.7 years. Lung ultrasound via modified Bedside Lung Ultrasound in Emergency protocol assisted in the identification of viral pneumonia (n = 15; 75%), viral pneumonia with superimposed bacterial pneumonia (n = 7; 35%), isolated bacterial pneumonia only (n = 1; 5%), and no findings of viral or bacterial pneumonia (n = 4; 20%) in this cohort of patients. Based on 54 observations, interobserver agreement for distinguishing viral from bacterial pneumonia using lung ultrasound was ĸ = 0.82 (0.63 to 0.99).

Conclusions: Lung ultrasound may be used to distinguish viral from bacterial pneumonia. Lung ultrasound may be useful during epidemics or pandemics of acute respiratory illnesses for rapid point-of-care triage and management of patients.

Figure 1

Laboratory-confirmed H1N1 hospital admissions and emergency department visits for influenza-like illnesses in NYC. 26 April to 10 June 2009. ED visits quadrupled at peak surge. Adapted from [1].

Figure 2

Rate of influenza-like illness syndrome visits to NYC emergency departments by age group. Based on chief complaint. 01 April to 01 June 2009. Adapted from [1].

Figure 3

Bedside Lung Ultrasound in Emergency protocol - modified for ED. Includes posterior thorax scanning.

Figure 4

Six-zone lung scanning protocol. Top Row: Anterior Midclavicular Line; Middle Row: Lateral Midaxillary Line; Bottom Row: Posterior Paraspinal Line. Probes in transverse (columns in A and D) and parasagittal planes (columns B and C) in anterior and posterior lung fields, and in transverse and coronal planes (middle row) in lateral lung fields.

Figure 5

Small subpleural consolidations (arrows) with trailing comet tail artifacts consistent with viral pneumonia lung ultrasound pattern. (A, B, and C) are images of small subpleural lung consolidations in three different patients with suspected H1N1.

Figure 6

B-lines and confluent B-lines consistent with viral pneumonia lung ultrasound pattern.

Figure 7

Viral (B-lines) and bacterial pneumonia (lung consolidation with sonographic air bronchogram) pattern. A-lines are horizontal lines that represent the normal aerated lung.

Figure 8

Lung consolidation with sonographic air bronchograms consistent with bacterial pneumonia.