Evaluation of Regional Distribution of Ventilation During Labor With or Without Epidural Analgesia

Overview

With an efficient epidural analgesia the physiological effects of pain are disabled during labor. Pain may cause an increase of minute volume, oxygen consumption and a decrease of paCO2 (Arterial CO2 pressure). The study will evaluate the lung function before and after labor with and without epidural analgesia. With more efficient breathing, the occurence of atelectasis should be reduced; this effect will be investigated in these settings for the first time with the electrical impedance tomography, which is a completely non-invasive measure.

The bedside efficacy of the electrical impedance tomography (EIT) in intensive care settings during mechanical ventilation is known. However, no studies demonstrate its utility during epidural analgesia for labor. The purpose of this study is to evaluate lung function and atelectasis in pregnant women with or without epidural analgesia, during labor and after delivery. Only adult consenting patients ASA I \& ASA II (American Society of Anaesthesiologists) are included in the study. According to institutional protocols lumbal epidural catheter is inserted and tested at the start of the labor, while patients' parameters are monitored. Refusal to epidural analgesia, technical difficulties to insert the epidural catheter or any medical contraindication will result in inclusion of these patients in the control group. Measurement with EIT is not invasive and harmful neither for the mother nor for the child. It consists of putting a belt around the chest; this belt is linked to a monitor which measures the impedance of the different lung regions. Electrical impedance measurements will be done for short periods of maximum 5 min. each as follows: 1. Placement before injection of local anesthetics through the epidural catheter in the study goup; in the control subset placement of the belt will be done when an epidural anesthetic would have been considered. 2. 1 hour after placement of the belt 3. 1 hour after delivery These periods will be compared.