The Evaluation of a Non-Invasive Respiratory Volume Monitor in Patients Undergoing Dental Extractions During Moderate Sedation

This pilot study examines the clinical utility of the ExSpiron Respiratory Volume Monitor (RVM, ExSpiron™, Respiratory Motion, Inc.; Waltham, MA) in oral surgery patients during moderate sedation. Previous work demonstrated the ability of this novel technology to provide non-invasive, real-time, continuous measurements of tidal volume (TV), minute ventilation (MV) and respiratory rate (RR) in spontaneously breathing patients.^{1, 2}There are currently limited options for monitoring respiratory status in non-intubated patients including pulse  oximetry, capnography and subjective clinical assessment. Respiratory depression, due to the effects of sedatives and anesthetics, continues to be a significant concern. We studied the changes in ventilation with this device during moderate Fentanyl, Midazolam and Diazepam sedation.

Following IRB approval and written informed consent, subjects were enrolled in this prospective, observational study.  Tidal volume and vital capacity were measured with a hand-held spirometer for baseline comparison to the RVM that uses impedance based technology and proprietary algorithms to obtain respiratory values. Minute Ventilation (MV), Tidal Volume (TV), and Respiratory Rate (RR) were collected from the RVM prior and during moderate sedation until discharge.  Age, sex, BMI and sedatives (timing, type and dose) along with vital signs were recorded and correlated with the device data. For each subject we assessed a MV baseline before sedation, and determined the  MV change to a threshold value of 80% from baseline  at 2 time points; Sedation start and 10 minutes post drug administration. The paired-t test and MANOVA were used for statistical analysis; a p < 0.05 was significant.

40 subjects (18 males, 22 females) were enrolled in the study and 32 subjects were included for this analysis. For all patients MV decreased to below 80% from baseline immediately after start of sedation. At 10 minutes following initial drug administration, MV of 18 subjects remained below 80% of baseline and 14 had recovered to above 80%. The demographics and sedation variables between these two groups were not independently significantly different.

Our study demonstrated an early decline of MV to below 80% of baseline immediately following sedative administration. 43.8% of patients recovered to above this threshold within 10 minutes. It is not clear from these preliminary data, which factors influence this outcome. Further study is needed to determine how this new technology could improve monitoring and patient safety outcomes in this setting.

 

1. Evaluation of a Novel Noninvasive Respiration Monitor Providing Continuous Measurement of Minute Ventilation in Ambulatory Subjects in a Variety of Clinical Scenarios. Voscopoulos C, Brayanov J, Ladd D, Lalli M, Panasyuk A, Freeman J Anesthesia & Analgesia July 2013 117:91-100; published ahead of print June 3, 2013, doi:10.1213/ANE.0b013e3182918098. 
2. 2.Non-Invasive Monitoring of Tidal Volume and Minute Ventilation in Non-Intubated Patients. Freeman, Jenny; Lalli, Michael; Yocum, Nicole; Panasyuk, Alexander; Panasyuk, Svetlana; Lew, Robert Critical Care Medicine: December 2011 - Volume 39 - Issue 12 - p 88. doi: 10.1097/01.ccm.0000408627.24229.88.Poster, Pulmonary Diagnostics. 41st Critical Care Congress February 5th, 2012. Houston. Texas