Atelectasis Frequency in Different Ventilation Modes

Traditional and modified lung ultrasonography scoring systems can be used to evaluate atelectasis in the lung parenchyma by ultrasonography. The modified scoring system also provides the opportunity to evaluate small subpleural consolidations in addition to the traditional system.

Lung tissue is evaluated between the intercostal spaces. On ultrasound, the pleural line can usually be seen as bright white due to the acoustic impedance difference between the aerated lung tissue and the surrounding tissues. Most of the ultrasound waves are reflected from this line. Due to the constantly reflected ultrasound waves between the pleural line and the transducer, hyperechoic lines parallel to the pleural line, called A lines, can be observed in the parenchyma. Vertical hyperechoic lines emerging from the pleural line in the lung ultrasound image are defined as B lines. B lines follow perpendicular to A lines. B lines accompany the sliding movement of the lungs along with the respiratory movement.

The patient is usually evaluated while lying in the supine position. The thorax is divided into 12 quadrants when evaluated with ultrasound for atelectasis. Midsternal line, anterior axillary line, posterior axillary line form the vertical boundaries of the quadrants. Each area is divided into two parts, upper and lower, by a line passing through its midpoint. Left hemithorax anterior upper, lateral upper, posterior upper, anterior lower, lateral lower, posterior lateral; The right hemithorax consists of 12 quadrants: anterior upper, lateral upper, posterior upper, anterior lower, lateral lower, and posterior lateral. The ultrasound probe is advanced transversely and each quadrant is examined. The patient may be asked to turn slightly to the side to evaluate the posterior quadrants. The ultrasound probe is placed vertically on the ribs and the lung parenchyma seen between the intercostal spaces is evaluated. Loss of ventilation is evaluated according to the modified lung ultrasonography scoring system for each quadrant. The score is collected by evaluating 12 quadrants from 0 to 3 and a value between 0-36 is obtained. For each quadrant, 0 represents the region with no ventilation loss and 3 indicates the region with severe ventilation loss. 0 indicates normal tissue with no loss of ventilation and 2 or fewer B lines are observed. 1 indicates little loss of ventilation, 3 or more B lines or one or more subpleural consolidations separated by a normal pleural line are observed. 2 indicates moderate loss of ventilation, observed as multiple fused B lines or multiple small subpleural consolidations separated by thickened or irregular pleural lines. 3 indicates severe loss of ventilation and is observed as consolidation or subpleural consolidation larger than 1x2 cm.

Each patient underwent transthoracic lung ultrasonography a total of 4 times: before laryngeal mask airway (LMA), at the 10th minute after LMA, before extubation and at the 10th minute after extubation. In addition, data on respiratory mechanics and hemodynamic parameters were recorded twice, at the 10th minute after LMA and before extubation.