Electrical Impedance Tomography Analysis Between Two Similar Respiratory System Compliance During Decremetal PEEP Titration in ARDS Patients

PURPOSE: The positive end-expiratory pressure (PEEP) level with best respiratory system compliance (Crs) is frequently used for PEEP selection in acute respiratory distress syndrome (ARDS) patients. On occasion, two similar best Crs (where the difference between the Crs of two PEEP levels is < 1 ml/cm H(2)O) may be identified during decremental PEEP titration. Selecting PEEP under such conditions is challenging. The aim of this study was to provide supplementary rationale for PEEP selection by assessing the global and regional ventilation distributions between two PEEP levels in this situation. METHODS: Eight ARDS cases with similar best Crs at two different PEEP levels were analyzed using examination-specific electrical impedance tomography (EIT) measures and airway stress index (SIaw). Five Crs were measured at PEEP values of 25 cm H(2)O (PEEP(25)), 20 cm H(2)O (PEEP(20)), 15 cm H(2)O (PEEP(H)), 11 cm H(2)O (PEEP(I)), and 7 cm H(2)O (PEEP(L)). The higher PEEP value of the two PEEPs with similar best Crs was designated as PEEP(upper), while the lower designated as PEEP(lower). RESULTS: PEEP(H) and PEEP(I) shared the best Crs in two cases, while similar Crs was found at PEEP(I) and PEEP(L) in the remaining six cases. SIaw was higher with PEEP(upper) as compared to PEEP(lower) (1.06 ± 0.10 versus 0.99 ± 0.09, p = 0.05). Proportion of lung hyperdistension was significantly higher with PEEP(upper) than PEEP(lower) (7.0 ± 5.1% versus 0.3 ± 0.5%, p = 0.0002). In contrast, proportion of recruitable lung collapse was higher with PEEP(lower) than PEEP(upper) (18.6 ± 4.4% versus 5.9 ± 3.7%, p < 0.0001). Cyclic alveolar collapse and reopening during tidal breathing was higher at PEEP(lower) than PEEP(upper) (34.4 ± 19.3% versus 16.0 ± 9.1%, p = 0.046). The intratidal gas distribution (ITV) index was also significantly higher at PEEP(lower) than PEEP(upper) (2.6 ± 1.3 versus 1.8 ± 0.7, p = 0.042). CONCLUSIONS: PEEP(upper) is a rational selection in ARDS cases with two similar best Crs. EIT provides additional information for the selection of PEEP in such circumstances. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40846-021-00668-2.