Lung ultrasound can be used to predict the potential of prone positioning and assess prognosis in patients with acute respiratory distress syndrome

Abstract

Background: It is very important to assess the effectiveness of prone positioning (PP) in patients with severe acute respiratory distress syndrome (ARDS). However, it is difficult to identify patients who may benefit from PP. The purpose of this study was to investigate whether prone positioning potential (PPP) can be predicted by lung ultrasound in patients with ARDS.

Methods: In this prospective study, 45 patients with ARDS were included for the assessment of PPP. A PP lung ultrasound examination (PLUE) protocol was performed in the dorsal regions of the lung in 16 areas at H0, H3, and H6 (0, 3, and 6 h after PP). The ultrasonography videos were blindly evaluated by two expert clinicians to classify the lung regions as normal pattern (N), moderate loss of lung aeration (B1), severe loss of lung aeration (B2), and consolidation (C). The aeration scores were collected at H0, H3, and H6. According to the ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (P/F ratio) at 7 days, patients were classified into PPP-positive (P/F ratio >300) and PPP-negative groups; also, the patients were classified into survival and nonsurvival groups according to 28-day mortality.

Results: Aeration scores was compared at H0, H3, and H6. The scores were significantly reduced between H3 and H0, but there was no difference between H3 and H6. The aeration score variation (ASV) of the PPP-positive group between H3 and H0 was significantly higher than that in the PPP-negative group, and the sensitivity and specificity of ASV ≥5.5 for the PPP-positive group were 73.9% and 86.4%, respectively. The area under the receiver operating characteristic curve (AUROC) was 0.852 for the ASV. The ASV between H3 and H0 in the survival group was significantly higher than in the nonsurvival group. The sensitivity and specificity of ASV ≥7 for survival were 51.5% and 75%, respectively. The AUROC was 0.702 for the ASV.

Conclusions: The PLUE protocol can be used to predict PPP and assess prognosis in patients with ARDS.

Keywords: Acute respiratory distress syndrome; Lung ultrasound; Prone position.

Fig. 1

The examination areas in the prone position lung ultrasound examination protocol. Line 1 paravertebral line, line 2 scapular line, line 3 posterior axillary line

Fig. 2

Flowchart of the study. ARDS Acute respiratory distress syndrome, PPP Prone positioning potential

Fig. 3

Lung ultrasound scores of the dependent region at different time points (** p < 0.01). NS No significant difference. H0 Start of prone positioning, H3 3 h after prone positioning, H6 6 h after prone positioning

Fig. 4

a Lung ultrasound scores at H0 and H3 in the PPP-positive and PPP-negative groups. b The aeration score variations between H3 and H0 in the PPP-positive and PPP-negative groups (** p < 0.01). ASV Aeration score variation, H0 Start of prone positioning, H3 3 h after prone positioning, LUS Lung ultrasound score, PPP Prone positioning potential

Fig. 5

a Receiver operating characteristic curve (ROC) predicting the prone positioning potential with the aeration score variation (ASV). b ROC predicting the survival state with the ASV. AUC Area under curve

Fig. 6

a Lung ultrasound scores at H0 and H3 in the survival and nonsurvival groups. b Aeration score variations between H3 and H0 in the survival and nonsurvival groups (** p < 0.01, * p < 0.05). LUS Lung ultrasound score, ASV Aeration score variation, H3 3 h after prone positioning, H0 Start of prone positioning

Fig. 7

a The ratio of partial pressure of arterial oxygen to fraction of inspired oxygen (P/F ratio) during prone positioning at H0 and H3. b The percentage of dead space during prone positioning at H0 and H3 (** p < 0.01). H3 3 h after prone positioning, H0 Start of prone positioning

Fig. 8

a Correlation of oxygenation improvement and aeration score variation (ASV). b Correlation of the change in dead space and ASV