Utility of lung ultrasound in adjustment of the initial mechanical ventilation settings in patients with acute respiratory distress syndrome

Background
Bedside lung ultrasound (US) is an essential tool in assessing lung aeration in severely ill patients.


Aim
The goal of this study was to determine the use of lung US in evaluating changes in lung aeration in dependent lung areas during positive end expiratory pressure (PEEP) titration in patients with acute respiratory distress syndrome (ARDS).


Patients and methods
A total of 52 mechanically ventilated patients with ARDS admitted in the ICU of Abbassia Chest Hospital were enrolled in this study. Transthoracic sonography was performed at the posterior axillary line on either side after 30 min of initial ventilator settings; recruitment at the end of expiration was sonographically assessed while changing PEEP. Arterial blood gases were performed before and after recruitment maneuver along with continuous monitoring of hemodynamics and oxygen saturation throughout the procedure. The procedure was terminated if the plateau pressure exceeded 30 cmH2O or if there was hemodynamic compromise.


Results
A total of 52 mechanically ventilated patients with ARDS were enrolled in the study. Overall, 80% had severe ARDS. Initial US assessments were done, and subpleural consolidation (C) was found in 18 patients, whereas exaggerated B lines (B) were found in 33 patients. After PEEP titration, under US guidance, 13 patients changed the US pattern from C to B and 22 patients changed from B to A (A-line pattern). These results correlated with improvement of PaO2/FiO2 ratio from 69.98 ± 27.93 to 86.21 ± 31.64 and increased compliance from 26.49 ± 8.63 to 28.73 ± 8.74. However, there was an increase in plateau pressure from 25.12 ± 3.88 to 27.98 ± 3.18, and also PaCO2 increased from 51.00 ± 16.05 to 58.52 ± 15.93. The mean arterial blood pressure decreased from 84.87 ± 7.91 to 81.60 ± 8.72.


Conclusion
US is an effective tool in achieving PEEP titration in mechanically ventilated patients with ARDS. US finding of aeration correlates well with improvement in oxygenation and compliance. However, the patients should be monitored for safe limits of pressures, hemodynamics, and PaCO2 level that may rise.