Background: Continuous monitoring of respiratory status is important for identifying potentially life-threatening respiratory compromise, performing clinically appropriate interventions, and monitoring patient recovery. A recently developed non-invasive Respiratory Volume Monitor (RVM) has been shown to have better than 10% accuracy for minute ventilation (MV), tidal volume (TV), and respiratory (RR) in both non-intubated and intubated patients. The current RVM requires a patient-specific calibration with a spirometer. To facilitate broader use, the RVM has been updated to measure MV and TV without the need for a patient-specific calibration. Here, we evaluated the accuracy of the RVM without patient-specific calibration compared to three FDA-cleared devices.

Methods: 20 subjects from a broad ambulatory population (11 males, BMI=26.8 kg/m2 (18-41), 49.2 yrs (22-80)) had MV, TV, and RR simultaneously recorded by the RVM without a patient-specific calibration and a comparison device: Pneumotachometer (Heated FVL, Morgan Scientific), Wright Respirometer (Mark 14, nSpire Health), and RVM with patient-specific calibration (ExSpiron, Respiratory Motion). Subjects completed 3 trials on Day 1 and repeated them on Day 2, wearing electrode pads continuously for 24 hours. Relative errors in measurements of MV, TV, and RR were calculated. Bias, precision, and accuracy were calculated using Bland-Altman analyses. Paired-difference equivalence tests were performed with equivalence margins of 10% relative error.

Results: The RVM’s mean measurement biases for MV and TV were within 2.2% compared to all three comparison devices and within 0.2% for RR (Table 1). The mean measurement accuracies were better than 11.6% for MV and TV and better than 4.1% for RR (Fig 1A). Equivalence tests showed that MV, TV, and RR were equivalent within ±10%.

Conclusion: We demonstrated that the RVM can deliver accurate MV, TV, and RR measurements without the need for patient-specific calibration.  This new capability streamlines the workflow of the RVM and enables healthcare providers to provide continuous and non-invasive respiratory assessments in a broader variety of clinical settings.

07 / Evaluation of a non-invasive respiratory volume monitor without patient-specific calibration