The evaluation of a non-invasive respiratory volume monitor in surgical patients undergoing elective surgery with general anesthesia

Abstract

Continuous respiratory assessment is especially important during post-operative care following extubation. Respiratory depression and subsequent adverse outcomes can arise due to opioid administration and/or residual anesthetics. A non-invasive respiratory volume monitor (RVM) has been developed that provides continuous, real-time, measurements of minute ventilation (MV), tidal volume (TV), and respiratory rate (RR) via a standardized set of thoracic electrodes. Previous work demonstrated accuracy of the RVM versus standard spirometry and its utility in demonstrating response to opioids in postoperative patients. This study evaluated the correlation between RVM measurements of MV, TV and RR to ventilator measurements during general anesthesia (GA). Continuous digital RVM and ventilator traces, as well as RVM measurements of MV, TV and RR, were analyzed from ten patients (mean 62.6±7.4 years; body mass index 28.6±5.2 kg/m2) undergoing surgery with GA. RVM data were compared to ventilator data and bias, precision and accuracy were calculated. The average MV difference between the RVM and ventilator was -0.10 L/min (bias: -1.3%, precision: 6.6%, accuracy: 9.0%. The average TV difference was 40 mL (bias: 0.4%, precision: 7.3%, accuracy: 9.1%). The average RR difference was -0.22 breaths/minute (bias: -1.8%, precision: 3.7% accuracy: 4.1%). Correlations between the RVM traces and the ventilator were compared at various points with correlations>0.90 throughout. Pairing the close correlation to ventilator measurements in intubated patients demonstrated by this study with previously described accuracy compared to spirometry in non-intubated patients, the RVM can be considered to have the capability to provide continuity of ventilation monitoring post-extubation This supports the use of real-time continuous RVM measurements to drive post-operative and post-extubation protocols, initiate therapeutic interventions and improve patient safety.

A Brief Review of Non-invasive Monitoring of Respiratory Condition for Extubated Patients with or at Risk for Obstructive Sleep Apnea after Surgery

“…An over 24-h study by Voscopoulos et al showed that RVM has similar accuracy and high correlation with spirometry in measuring MV, TV, and RR, based on comparison between RVM and ventilator measurements in both intubated and non-intubated patients (56, 57). It is also noteworthy that the patients’ average RR difference between the RVM measurements and the manual counting of individual breaths, by the technician, during the 24-ho study was 0.0 breaths/min, demonstrating that the RVM is extremely accurate in measuring RR (56).…”

Avoiding Adverse Events Secondary to Opioid-Induced Respiratory Depression

“…In an analysis of 178 patients receiving IV PCA, episodes of desaturation (defined as SPO 2 <90%) occurred in 12% of patients, within a mean timeframe of about 24 hours after initiation of PCA. 28,29 Patients older than 65 years and the morbidly obese were most likely to experience these episodes. Occurrences of decreased respiratory rate or bradypnea (defined as <10 breaths per minute lasting Q3 minutes) were also observed in these study populations.…”

“…Minute ventilation monitors are user friendly and may be found more effective than pulse oximetry in patients taking opioids for pain control. 29 Regardless of the type of monitor, nurse leaders should consider training clinicians on the use of continuous monitoring during sleep.…”

Continuous Postoperative Respiratory Monitoring with Calibrated Respiratory Effort Belts: Pilot Study

“…They found that abnormal breathing patterns are extremely common. Voscopoulos et al [14,15,16] have studied minute ventilation, tidal volume and respiratory rate of postoperative subjects using impedancebased electrodes placed to a subject's body. In addition to these, Masa et al [17] showed that respiratory effort-related arousals in sleep apnea patients could be identified satisfactorily by assessing the morphology of the thoracoabdominal bands output signal.…”