Corrective effect of diaphragm pacing on the decrease in cardiac output induced by positive pressure mechanical ventilation in anesthetized sheep

Respir Physiol Neurobiol. 2017 Feb:236:23-28. doi: 10.1016/j.resp.2016.10.009. Epub 2016 Nov 9.

Abstract

Positive pressure ventilation (PPV) is a fundamental life support measure, but it decreases cardiac output (CO). Diaphragmatic contractions produce negative intrathoracic and positive abdominal pressures, promoting splanchnic venous return. We hypothesized that: 1) diaphragm pacing alone could produce adequate ventilation without decreasing CO; 2) diaphragm pacing on top of PPV could improve CO. Of 11 anesthetized and mechanically ventilated ewes (39.6±5.9kg), 3 were discarded from analysis because of hemodynamic instability during the experiment, and 8 retained for analysis. Phrenic stimulation electrodes were inserted in the diaphragm (implanted phrenic nerve stimulation, iPS). CO was measured by the thermodilution technique (pulmonary artery catheter). CO during end-expiratory apnea served as reference. Median CO was 9.77 [6.25-11.25] lmin-1 during end-expiratory apnea, 8.25 [5.06-9.25] lmin-1 during "PPV" (-15%) (p<0.05), 9.19 [5.60-10.19] lmin-1 during "PPV-iPS" (NS vs apnea) and 9.37 [6.12-10.48] lmin-1 during "iPS" (NS vs. apnea). iPS-driven ventilation was comparable to its PPV counterpart (median 92% [74-97], NS). Diaphragm pacing alone can produce adequate ventilation without reducing CO. Superimposed onto PPV, diaphragm pacing can reduce the PPV-induced decrease in CO.

Keywords: Cardiac output; Diaphragm; Hemodynamics; Phrenic stimulation; Positive pressure ventilation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anesthesia*
  • Animals
  • Blood Pressure / drug effects
  • Blood Pressure / physiology
  • Cardiac Output / physiology*
  • Diaphragm / physiology*
  • Electrocardiography
  • Electrodes, Implanted
  • Female
  • Phrenic Nerve / physiology
  • Positive-Pressure Respiration*
  • Respiration* / drug effects
  • Sheep