Introduction. Atelectasis occurs in about 90% of all patients who are anesthetized [1]. Lung Ultrasound provides relevant information on the state of lung aeration [2]. We wanted to evaluate atelectasis formation soon after anesthesia and to detect any difference in the study population.
Materials and Methods. We enrolled 86 healthy (ASA 1 and 2), young (<65 years), female patients, undergoing general anesthesia for hystero resection without complications and with an anesthesia no longer then one hour. We evaluated the lung with a convex probe, in twelve dorsal areas above the diaphragm, before anesthesia (T0) and soon after (T1). We counted the B lines from 0 to 10, we quantified the C lines (small subpleural consolidations) from 1 to 3 and we defined atelectasis as the presence of at least three B lines or a C line in an intercostal space [3]. We also calculated the lung ultrasound score as described by Via [2]. 
Results and Discussion.  84 patients completed the study, mean age: 48,5±9, BMI: 24,7±5 and smokers 29%. The procedure lasted 36±8 min. and nearly all the patients developed atelectasis (94%). The number of B lines, C lines and the lung score, all increased significantly. B lines T0: 1[0-2] T1: 17,5[9-34]; C lines T0: 0[0-0] T1: 3[1-7]; lung score T0: 0[0-0] T1: 7[3-15] (Wilcoxon signed ranks test p<0,0001). We found no differences in relation to age, BMI or smoke habit, but patients with a shorter procedure (less then 35 min.) developed fewer C lines: 2[1-3,5] vs. 5[1-9] (Mann-Whitney test p=0,02). Our findings are very similar to those obtained by Hedenstierna with chest CT scans [1].
Conclusion. Lung Ultrasound is a reliable, safe and repeatable method to detect anesthesia-induced atelectasis in adult healthy patients.  
 
 

Reference
[1]. Hedenstierna G, Edmark L. Mechanism of atelectasis in perioperative period. Best Pract Res Clin Anaesthesiol. 2010 June; 24(2): 157-69
[2]. Via G, Storti E, Gulati G, et al. Lung Ultrasound in the ICU: from diagnostic instrument to respiratory monitoring tool. Minerva Anestesiol. 2012; Nov 78(11): 1282-96
[3]. Lichtenstein DA. Whole Body Ultrasonography in the Critically ill. Berlin: Springer-Verlag; 2010

Lung Ultrasound to detect anesthesia-induced atelectasis in adult healthy patients