Background: Currently there is no technology that noninvasively measures the adequacy of ventilation in nonintubated patients. A novel, noninvasive Respiratory Volume Monitor (RVM) has been developed to continuously measure and display minute ventilation (MV), tidal volume (TV), and respiratory rate (RR) in a variety of clinical settings. We demonstrate the RVM's accuracy and precision as compared with a standard spirometer under a variety of clinically relevant breathing patterns in nonintubated subjects.
Methods: Thirty-one voluntary subjects completed the primary study. MV, TV, and RR measurements were collected from the RVM and spirometer simultaneously for each participant on day 1 and day 2 and analyzed to determine accuracy, precision, and bias for normal, fast, slow, irregular, and closed-glottis breathing.
Results: Data demonstrated that RVM and spirometer measurements of MV and TV are equivalent in a wide range of ambulatory subjects with an average error <10% (95% confidence interval for accuracy <16%, precision <12%, and bias <11%). Repeated measures analysis of variance found no significant difference between spirometry and RVM individual measurements of MV, TV, and RR (P > 0.7), whereas a paired-difference equivalent test demonstrated, with 99% power, that both MV and TV measurements from the 2 devices are equivalent within ±15%.
Conclusions: This study demonstrates RVM's clinically relevant accuracy and precision in measuring MV, TV, and RR over a 24-hour period and during various breathing patterns.