The calibration of esophageal pressure by proper esophageal balloon filling volume: A clinical study

BACKGROUND: Esophageal pressure (Pes) can be used as a reliable surrogate for pleural pressure, especially in critically ill patients requiring personalized mechanical ventilation strategies. How to choose the proper esophageal balloon filling volume and then find the optimal value of esophageal pressure remains a challenge. The study aimed to assess the feasibility of catheters for Pes monitoring in mechanically ventilated patients. MATERIALS AND METHODS: Twelve patients under pressure-controlled mechanical ventilation were included in this study. Raw esophageal pressure was recorded at different balloon filling volumes. Then, the P-V curves were determined. V(WORK) was the intermediate linear section on the end-expiratory P-V curve, and V(BEST) was the filling volume providing the maximum difference between Pes at end-inspiration and end-expiration. The raw value of Pes was recorded, and the calibrated values of Pes were calculated by calculating the esophageal wall pressure (Pew) and esophageal elastance (Ees). RESULTS: Twenty-four series of Pes measurements were performed. The mean V(MIN) and V(MAX) were 2.17 ± 0.49 ml (range, 1.0–3.0 ml) and 6.79 ± 0.83 ml (range, 5.0–9.0 ml), respectively, whereas V(BEST) was 4.69 ± 0.16 ml (range, 2.0–8.0 ml). Ees was 1.35 ± 0.51 cm H(2)O/ml (range, 0.26–2.38 cm H(2)O/ml). The estimated Pew at V(BEST) was 3.16 ± 2.19 cm H(2)O (range, 0–7.97 cm H(2)O). Patients with a body mass index (BMI) ≥ 25 kg/m(2) had a significantly lower V(MAX) (5.88 [5.25–6] vs. 7.25 [7–8] ml, p = 0.006) and a significantly lower V(BEST) (3.69 [2.5–4.38] vs. 5.19 [4–6] ml, p = 0.036) than patients with a BMI < 25 kg/m(2). Patients with positive end-expiratory pressure (PEEP) ≥ 10 cm H(2)O had a lower V(MIN) and V(BEST) than patients with PEEP < 10 cm H(2)O, P > 0.05. Patients in the supine position had a higher esophageal pressure than those in the prone position with the same balloon filling volume. CONCLUSIONS: Calibration of esophageal pressure to identify the best filling volume of esophageal balloon catheters is feasible. The esophageal pressure can be influenced by BMI, PEEP, and position. It is necessary to titrate the optimal inflation volume again when the PEEP values or the positions change.