Sitting and Supine Esophageal Pressures in Overweight and Obese Subjects

Esophageal pressure (P _Es) can be used to approximate pleural pressure (P _pl) and might be clinically useful, particularly in the obese e.g., to guide mechanical ventilator settings in critical illness. However, mediastinal artifact (the difference between true P _pl and P _Es) may limit acceptance of the measurement, and reproducibility of P _Es measurements remains unknown. Therefore, we aimed to assess the effect of body posture on P _Es in a cohort of obese, but healthy subjects, some of whom had multiple measurements, to address the clinical robustness of esophageal manometry. Twenty-five overweight and obese subjects (BMI > 25 kg/m 2) and 11 control lean subjects (BMI 25 kg/m 2) underwent esophageal manometry with pressures measured seated and supine. Twenty overweight and obese subjects had measurements repeated after ∼1 to 2 weeks. Anthropometric data and sitting and supine spirometry were recorded. The average end-expiratory P Es sitting and supine were greater in the overweight and obese group than the lean group (sitting 0.1 ± 2.1 vs. 3.3 ± 1.2 cmH 2 O, supine 9.3 ± 3.3 vs. 6.9 ± 2.8 cmH 2 O, respectively). The mean differences between repeated measurements were small (0.3 ± 1.7 cmH 2 O sitting and 0.1 ± 1.5 cmH 2 O supine). P _Es correlated with a number of anthropometric and spirometric variables. In conclusion, P _Es are slightly greater in overweight and obese subjects than lean subjects; but changes with position are similar in both groups. These data indicate that mediastinal weight and postural effects on P _Es are within a clinically acceptable range, and suggest that esophageal manometry can be used to inform clinical decision making across wide range of body types.