A randomised trial evaluating mask ventilation using electrical impedance tomography during anesthetic induction: one-handed technique versus two-handed technique

Objective. Mask positive-pressure ventilation could lead to lung ventilation inhomogeneity, potentially inducing lung function impairments, when compared with spontaneous breathing. Lung ventilation inhomogeneity can be monitored by chest electrical impedance tomography (EIT), which could increase our understanding of mask ventilation-derived respiratory mechanics. We hypothesized that the two-handed mask holding ventilation technique resulted in better lung ventilation, reflected by respiratory mechanics, when compared with the one-handed mask holding technique. Approach. Elective surgical patients with healthy lungs were randomly assigned to receive either one-handed mask holding (one-handed group) or two-handed mask holding (two-handed group) ventilation. Mask ventilation was performed by certified registered anesthesiologists, during which the patients were mechanically ventilated using the pressure-controlled mode. EIT was used to assess respiratory mechanics, including ventilation distribution, global and regional respiratory system compliance (C (RS)), expiratory tidal volume (TVe) and minute ventilation volume. Hemodynamic parameters and the PaO2-FiO(2) ratio were also recorded. Main results. Eighty adult patients were included in this study. Compared with spontaneous ventilation, mask positive-pressure ventilation caused lung ventilation inhomogeneity with both one-handed(global inhomogeneity index: 0.40 +/- 0.07 versus 0.50 +/- 0.15; P < 0.001) and two-handed mask holding (0.40 +/- 0.08 versus 0.50 +/- 0.13; P < 0.001). There were no differences in the global inhomogeneity index (P = 0.948) between the one-handed and two-handed mask holding. Compared with the one-handed mask holding, the two-handed mask holding was associated with higher TVe (552.6 +/- 184.2 ml versus 672.9 +/- 156.6 ml, P = 0.002) and higher global C (RS) (46.5 +/- 16.4 ml/cmH(2)O versus 53.5 +/- 14.5 ml/cmH(2)O, P = 0.049). No difference in PaO2-FiO(2) ratio was found between both holding techniques (P = 0.743). Significance. The two-handed mask holding technique could not improve the inhomogeneity of lung ventilation when monitored by EIT during mask ventilation although it obtained larger expiratory tidal volumes than the one-handed mask holding technique.