Electrical impedance tomography's correlation to lung volume is not influenced by anthropometric parameters.

ABSTRACT

STUDY OBJECTIVES: Electrical impedance tomography (EIT) is able to reflect physiological parameters such as real-time changes in global and regional lung volume. EIT can aid in the assessment of lung recruitment, and its use has been validated in preliminary studies monitoring mechanical ventilation at the bedside. ICU patients vary widely in their body habitus, and obesity is becoming more prevalent. Our primary research purpose was to establish whether anthropometric parameters influence EIT's reliability. Our secondary question was whether body position alters its correlation to spirometric measurements. SUBJECTS: 22 healthy adult volunteers (12 male, 10 female) with broadly variable anthropometric parameters. INTERVENTIONS: Simultaneous measurements of changes in lung volume using EIT imaging and a pneumotachograph were obtained with two breathing patterns (quiet and deep breathing) and in four body positions (standing, sitting, semi-reclining and supine). MEASUREMENTS AND RESULTS: Correlation between measurements of changes in lung volume using EIT imaging and a pneumotachograph was excellent. Variations attributable to anthropometric measurements accounted for at most a 1.3% difference. CONCLUSIONS: Anthropometric variability and body position do not adversely influence the EIT estimation of changes in lung volume. These data suggest EIT could be used to monitor critically ill mechanically ventilated adults with variable body habitus regardless of position.