The regional ventilation distribution monitored by electrical impedance tomography during anesthesia induction with head-rotated mask ventilation

<i>Objective.</i>Abnormal regional lung ventilation can lead to undesirable outcomes during the induction of anesthesia. Head rotated ventilation has proven to change the airflow of upper airway tract and be effective in increasing the tidal volume. This study aimed to investigate the influence of head rotated mask ventilation on regional ventilation distribution during the induction phase of anesthesia.<i>Approach.</i>Ninety patients undergoing anesthesia induction were randomly assigned to receive either neutral head (neutral-head group) or rotated right side head (rotated-head group) mask ventilation. Pressure-controlled mode was used in all mechanical ventilation. The regional lung ventilation was monitored by electrical impedance tomography. The primary outcome was the ratio of left/right lung ventilation distribution. The secondary outcomes were global inhomogeneity index (GI), center of ventilation (CoV, 100% = entirely dorsal), and the regional lung distribution differences between spontaneous and mask ventilation.<i>Main results.</i>Forty-two patients with neutral-head and 38 with rotated-head mask ventilation were analyzed finally. Compared with spontaneous ventilation, mask positive-pressure ventilation caused significant changes in the ratio of left/right lung ventilation distribution [0.85 (0.27) versus 0.94 (0.30);<i>P</i>= 0.022]. However, there were no differences in the ratio of left/right lung ventilation distribution between neutral and rotated head groups (<i>P</i>= 0.128). When compared with spontaneous ventilation, mask ventilation caused regional distributions of ventilation shifts towards ventral lung areas (CoV: 45.7 ± 5.0% versus 39.2 ± 4.8%;<i>P</i>< 0.001), and significant lung ventilation inhomogeneity (GI: 0.40 ± 0.07 versus 0.49 ± 0.14;<i>P</i>< 0.001). Compared with neutral-head mask ventilation, rotated-head mask ventilation was associated with higher expiratory tidal volume (TVe) (575.1 ± 148.6 ml versus 654.2 ± 204.0 ml;<i>P</i>= 0.049).<i>Significance.</i>Mask positive ventilation caused regional lung ventilation changes. When compared with neutral-head mask ventilation, rotated-head mask ventilation did not improve the regional ventilation towards to left lung. However, rotated-head mask ventilation was associated with higher TVe, and has the potential for better oxygenation.<b>Trial Registration.</b>This study was registered on Chinese Clinical Trial Registry on 6 August, 2024 (ChiCTR2400087858).