Use of a Respiratory Volume Monitor to Assess Respiratory Competence in Cardiac Surgery Patients After Extubation

Abstract

BackgroundPatients 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.MethodsRVM 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.ResultsDuring 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.ConclusionsRVM-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.

Variations in respiratory rate do not reflect changes in tidal volume or minute ventilation after major abdominal surgery

“…This was later confirmed in the pediatric population, where respiratory volume monitor and spirometer measurements were also similar within a 10% error [ 15 ]. Also, in intubated patients, measurements correlated well with ventilator settings in cardiac surgery as well as in obese subjects [ 16 , 17 ]. This makes the monitor well suited to detect early changes in respiration before oxygenation is impaired.…”

Monitoring Breathing Frequency, Pattern, and Effort

“…Utilization of RVM after extubation in postoperative patients has also been evaluated. Ianchulev et al 53 noted that RVM was able to provide clinicians with comprehensive, quantitative information related to breathing pattern and trends in ventilation that are not available with other technology at the time of their study. 53 The authors concluded that RVM shows real promise in improving patient safety in postextubation patients, among others.…”

“…Ianchulev et al 53 noted that RVM was able to provide clinicians with comprehensive, quantitative information related to breathing pattern and trends in ventilation that are not available with other technology at the time of their study. 53 The authors concluded that RVM shows real promise in improving patient safety in postextubation patients, among others. Other tools with the ability to monitor postextubation respiratory status, like the integrated pulmonary index, 54 have been evaluated since the study by Ianchulev et al, 53 but to our knowledge they have not been compared directly.…”

“…53 The authors concluded that RVM shows real promise in improving patient safety in postextubation patients, among others. Other tools with the ability to monitor postextubation respiratory status, like the integrated pulmonary index, 54 have been evaluated since the study by Ianchulev et al, 53 but to our knowledge they have not been compared directly.…”

Color Spectrographic Analysis of Respiratory Sounds: A Promising Technology for Respiratory Monitoring

“…Later, with the invention of stethoscope, simple acoustical methods of respiratory assessment became available to the clinical community. With the subsequent invention of electronic amplification, a variety of new technologies became available, including respiratory monitoring belts placed on the chest and abdomen [6 -9], nasal pressure methods [10,11], nasal / oral thermistor methods [12,13] (the thermistor warms up with expired gases), nasal / oral capnography [14,15], extraction of respiratory information from the photoplethysmograph signal [16,17], and electrical impedance methods based on a small injected electrical current [18,19].…”