Objective: To investigate the value of prone position lung ultrasound examination (PLUE) in monitoring the prone position during and predicting the outcome of Acute Respiratory Distress Syndrome (ARDS) patients.
Methods: All the ARDS patients needed to receive prone position were enrolled, a three hours PLUE was performed during the prone position for the first time. For each of the 16 regions examined, ultrasound patterns were recorded and the aeration scores were calculated at the beginning of the prone position and 3 hours later. The correlation of the aeration score variation (ASV) and the oxygen fraction were evaluated. The relationship between the ASV and the outcome indexes such as oxygen fraction, free of mechanical ventilation and mortality were also evaluated.
Results: A total of 29 patients were enrolled in this study. The aeration score of the lung was significantly reduced three hours after the beginning than the beginning (19.15 ± 7.98 vs 26.96 ± 6.43, P < 0.01) , with the significant increasing of the oxygen fraction. The ASV was significantly higher in the patients with oxygen fractions >300 mmHg (1 mmHg = 0.133 kPa) in Day 7 than those with oxygen fractions <300 mmHg (9.53 ± 4.34 vs 4.86 ± 2.96, P < 0.05). The ASV was also higher in the patients free of mechanical ventilation in Day 7 than those who needed mechanical ventilation (10.17 ± 4.45 vs 5.23 ± 3.03, P < 0.05). The area under the receiver operating characteristic curve was 0.840 and 0.824 respectively for detecting the validity of the prone position and the possibility of free of mechanical ventilation with ASV. For predicting the oxygen fraction >300 mmHg in Day 7, the cutoff value of ASV was ≥ 5.5, resulting a sensitivity of 86.7% and a specificity of 71.4%. For predicting the patients free of mechanical ventilation in Day 7, the cutoff value of ASV was 7, resulting a sensitivity of 75.0% and a specificity of 76.5%.
Conclusion: Bedside lung ultrasound is valuable in evaluating the ASV during the prone position in ARDS patients. The three hours PLUE can predict the outcome of ARDS patients such as validity of prone position and free of ventilation in Day 7. The value of predicting the mortality needs further investigation.