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Abstract
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Background and Aims The electrical impedance tomography (EIT) measures non-invasively atelectasis, through changes in the thoracic impedance. The purpose of the present study was to assess by EIT the effects of lumbar epidural analgesia on ventilation, in pregnant women, during labor, in sitting position.
Methods After Institutional Ethics Committee approval and written consent, 37 adult ASA 2 at term pregnant patients were studied. The belt of the EIT was placed around the patient’s thorax at Th4–Th6 level. The study recordings were done 10 minutes before and after insertion and loading of the epidural analgesia. Student’s paired t-test with the Bonferroni correction was applied to compare data before and after epidural analgesia, for the global and regional ventilation. Data are expressed as mean [95%CI].
Results Good levels of analgesia were obtained in all cases (VAS 8,43 vs 0,97 [ -8,208 to -6,710], p<0.001), with upper sensory levels reaching from Th4 to Th10. Atelectasis was seen in all patients before the epidural analgesia, with better ventilated regions centrally than peripherally. No effects of epidural analgesia on atelectasis were noted neither for the global, nor for regional ventilation (figure 1).
Conclusions This is the first study assessing lung atelectasis before and after epidural analgesia during labor. The changes in lung volumes, as demonstrated by this study, are mostly due rather to the mechanical pushing of the abdominal content towards the diaphragm and lung, and not to shallow breathing due to pain. Further studies in left lateral position are needed.
Individual and mean (bold line) global electrical impedance values during labor recorded before and after epidural analgesia, for a period of 10 minutes