Respiratory Volume Monitoring Reduces False Alarms in Non-Intubated Patients

WALTHAM, Mass., April 6, 2016 /PRNewswire/ -- Respiratory Motion, Inc. –Research presented at The International Symposium on Intensive Care and Emergency Medicine (ISICEM) Shows Respiratory Volume Monitoring Provides Early Warning of Respiratory Depression and can be Used to Reduce False Alarms in Non-Intubated Patients

In the post anesthesia care unit (PACU), monitoring for respiratory depression in extubated patients is by pulse oximetry (SpO2) and RR. SpO2 monitoring in PACU patients can be compromised by clinician alarm fatigue, a top patient safety concern that occurs when clinicians become desensitized or overwhelmed by the constant noise of alarms. Furthermore, measures to reduce alarm fatigue, including turning alarm limits down or alarm sounds off can exacerbate the problem. Pulse oximetry, a non-invasive method for monitoring a patient's saturation of peripheral oxygen (SpO2), is susceptible to motion artifact as it prevents the distinction between pulsing blood in the arteries and moving blood in the veins, causing the underestimation of oxygen saturation.

As a result, pulse oximetry is associated with high frequency of false alarms; to address this, clinicians change the alarm limits in an attempt to prevent false alarms. Unfortunately, SpO2 alarms are still more often triggered by sensor displacement than by actual respiratory events. Rather than alerting staff to a patient's deteriorating respiratory condition, true SpO2 alarms are often only triggered once the patient is already in respiratory distress.

The respiratory volume monitor (RVM) accurately measures minute ventilation (MV), tidal volume (TV), and respiratory rate (RR) in non-intubated patients. Its ability to non-invasively capture respiratory depression in advance of low SpO2 and with fewer false alarms was assessed.

Method
Equipment and Population: After obtaining written informed consent, monitoring data were collected from 240 extubated patients (none had an endotracheal tube) in the PACU following elective joint replacement surgery under either general or spinal anesthesia (130 females, 110 males; age: 66.8 ± 10.3 yrs; BMI: 29.6 ± 5.7 kg/m2). Respiratory data were recorded continuously from an RVM (ExSpiron, Respiratory Motion, Waltham, MA) via an electrode PadSet placed on the thorax. Simultaneously, SpO2 data were recorded at 1-min intervals.

Metrics: "Predicted" MV (MVPRED) and "Percent Predicted"(MVMEASURED/MVPREDx100%) were calculated for each patient. MVPRED was calculated using standard body surface area (BSA) formulas: BSA X 4 (men); BSA X 3.5 (women). MVPRED represents adequate MV during quiet respiration in awake, non-intubated patients. We defined SpO2 less than 90% as "Low SpO2", which triggered an alarm. Having "Low SpO2" for 2 minutes or more was defined as a "Desaturation Event". Having "Low SpO2" for less than 2 minutes was defined as a "False Alarm". "Un-Safe MV" was defined as MV less than 40% MVPRED.

Results In the 240 patients, 80 "Low SpO2" alarm conditions were recorded. Of them 62 (78%) were "False Alarms" (<2min). The remaining 18 "Desaturation Events" (≥ 2 min) occurred in 15 patients (longest 12 min). The RVM showed that 11 out of 18 "Desaturation Events" coincided with excessive patient motion (movement-induced) while still maintaining safe MV levels and only 7 events (1 per patient) were "True Desaturation" events (true indications of respiratory depression).

Distribution of the severity of desaturation events recorded in the EHR. The majority of the events (62/80) were less than 2 minutes long and as such considered to be "False Alarms." Only 1 event longer than 3 minutes was recorded.

Distribution across the patient cohort. 200/240 patients had no desaturation events, 25 patients had only "False Alarms", in 8 patients desaturation events coincided with excessive movement (movement-induced) while maintaining safe MV levels and only 7 patients (2.9% of the cohort) had "True Desaturations" which all coincided with "Un-safe MV" (and none of them coincided with excessive movement).

Each "True Desaturation" event was preceded by "Un-Safe MV" by an average of 16.7±4.6 min (mean ± SEM ) and the level of "Un-Safe MV" was strongly correlated with the time before an SpO2 alarm sounded (r=0.77, p<0.05). While MFANOVA found no difference in the demographics of the populations with real desaturation events versus "False Alarms" (p>0.2 for height, weight, age, BMI, sex), the length of stay in the PACU for the group with "True Desaturation" events was significantly longer (176±9 min v. 134±18 min, p<0.05).

Correlation between the severity of respiratory depression and the delay in registered desaturation. The lower the recorded MV the sooner the patient desaturates.

Conclusions

• Improvements in SpO2 monitoring equipment and conservative use of alarm limits have decreased false alarms; yet, this study showed that >90% of SpO2 alarm conditions in the PACU were most likely false.
• Continuous MV monitoring can be used to reduce false alarms in the PACU. More importantly, continuous MV monitoring gives advanced warning of developing respiratory depression. Early detection of desaturation leads to reduced severity of respiratory depression.
• RVM has the potential to improve patient safety and satisfaction and reduce the length of stay in the PACU associated with a true desaturation event.
• As respiratory depression is often caused by opioids, apnea, and other factors, continuous MV monitoring provides advanced warning and early point-of-care data for caregivers to modify opioid dosing or institute other interventions to prevent progression of respiratory depression to the point of true desaturation and severe compromise.

About ISICEM:
The International Symposium on Intensive Care and Emergency Medicine (ISICEM) is organized by the Departments of Intensive Care and Emergency Medicine of Erasme University Hospital, Université Libre de Bruxelles, in association with the Belgian Society of Intensive Care and Emergency Medicine (SIZ). The meeting is held every year in March. Started in 1980, this meeting has become established as one of the largest in its field, now attracting more than 6200 participants (including exhibitors and visitors) from countries worldwide. To learn more, visit  www.intensive.org

About Respiratory Motion, Inc.
Respiratory Motion, Inc. is a medical device company based in Waltham, MA, that develops innovative technology to monitor respiration and help clinicians and hospitals improve patient safety and outcomes. The company's monitoring systems can identify patients who are at risk for life-threatening respiratory depression. This allows physicians to prevent the dangerous condition before it harms a patient. To learn more, visit www.respiratorymotion.com

SOURCE Respiratory Motion, Inc.

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