title: Use of a Respiratory Volume Monitor to Assess Respiratory Competence in Cardiac Surgery Patients After Extubation.
abstract: BACKGROUND
  Patients who have undergone cardiac surgery are generally mechanically ventilated postoperatively. Early postoperative extubation is currently recommended in anesthesia guidelines. No current technology can accurately, non-invasively, measure respiratory competence after extubation. Pulse oximetry has been helpful, but this is a late indicator of respiratory compromise. A novel, non-invasive, respiratory volume monitor (RVM) has been shown to deliver accurate continuous, real-time minute ventilation (MV), tidal volume (TV) and respiratory rate (RR) measurements and provide an objective measure of respiratory competence. The RVM will accurately reflect MV, TV and RR in cardiac surgery patients before and after extubation.
  
  
  METHODS
  RVM traces were recorded from patients before and after cardiac surgery. Continuous monitoring began on admission to the unit and was ended at 24 h after extubation. RVM-based MV, TV and RR were calculated from 30-s segments. MV, TV and RR were also continuously recorded from the ventilator prior to extubation. The RVM was calibrated to each patient using the readings from the ventilator.
  
  
  RESULTS
  During mechanical ventilation, the RVM measured TVs strongly correlated with the ventilator TVs (r = 0.97). Following extubation, the patient's breathing became more erratic and TVs and MVs decreased. Within 1 h, all patients studied showed a marked recovery of MV and TV.
  
  
  CONCLUSIONS
  RVM-based MV, TV and RR correlated well with similar data collected from ventilators. After extubation, RVM shows promise as a means to monitor respiratory competence of non-intubated patients, and has implications for use in other settings and improving patient safety.
authors.affiliation: Tufts Medical Center, Boston, MA, USA.
authors.forename: Stephan
authors.initials: S
authors.lastname: Ianchulev
authors.affiliation: West Virginia University, Morgantown, WV, USA.
authors.forename: Diane
authors.initials: D
authors.lastname: Ladd
authors.affiliation: Respiratory Motion, Inc., Waltham, MA, USA.
authors.forename: C Marshall
authors.initials: CM
authors.lastname: MacNabb
authors.affiliation: Harvard Medical School, Boston, MA, USA.
authors.forename: Lizeng
authors.initials: L
authors.lastname: Qin
authors.affiliation: Tufts Medical Center, Boston, MA, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Marengi
authors.affiliation: Respiratory Motion, Inc., Waltham, MA, USA.
authors.forename: Jenny
authors.initials: J
authors.lastname: Freeman
keywords: Non-invasive; Postoperative; Respiratory volume monitor; Ventilation