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Unrecognized respiratory depression on the General Care Floor (GCF), culminating in respiratory arrest, is occurring every day at hospitals across the world. A significant portion of these respiratory arrests occur in postoperative patients receiving opioid analgesics and sedatives, which contribute to respiratory depression . Failure to recognize respiratory depression and institute timely resuscitation has led to cardiopulmonary arrest, resulting in anoxic brain injuries and deaths (only one in five patients suffering an in-hospital cardiac arrest survives to hospital discharge). While some patient populations - notably those patients with obstructive sleep apnea - appear to be at higher risk, it is important to emphasize that there is still a low but unpredictable incidence of life-threatening, opioid-induced respiratory depression in young healthy patients . Moreover, life-threatening, opioid-induced respiratory depression also occurs with intermittent parenteral injections of opioid analgesics.
The Anesthesia Patient Safety Foundation (APSF) recently called for “zero tolerance” to patient harm due to postoperative opioids . Among other and as previously stated by other standard bodies, APSF deems respiratory complications due to opioids to be preventable with better monitoring [1-5]. According to a "Closed Claims Analysis of Cases Involving Postoperative PCA and Neuraxial Narcotics” better monitoring could have prevented 73% of PCA related-cases and 56% of CNN related-cases . Therefore, to advance safety of postoperative patients receiving opioid analgesics and sedatives APSF urges clinicians to continuously monitor ventilation (i.e. patient’s PCO2 levels) and oxygenation (pulse oximetry) [2, 3]. Furthermore, considering lower staffing-to-patient ratios on the GCF - which typically preclude the level of direct surveillance – remote monitoring from a centralized station is essential and caregivers should be notified if adverse trends are observed that suggest hypoventilation [1, 2].
Monitoring patient ventilation and oxygenation on the general care floor
Arterial blood sampling - being intermittent and invasive - is obviously impractical to assess patients ventilation and oxygenation status on the general care floor routinely.
Pulse oximetry is an excellent means of continuously and noninvasively assessing patient oxygenation on the general care floor and helps avoid hypoxemia and tissue hypoxia. Furthermore, in patients who are breathing room air, pulse oximetry is – to a certain extent – an indirect indicator of hypoventilation. However, due to the physiology of the Hb-oxygen dissociation curve, pulse oximetry is NOT able to detect hypoventilation when supplemental oxygen is administered. In patients receiving supplemental oxygen and being monitored with pulse oximetry only, respiratory depression consequently may develop and deteriorate, remaining unnoticed until critical levels are reached.
- Sidestream endtidal PCO2 (etCO2) monitoring is continuous and relatively easy to use and potentially can reflect patient ventilation. However, etCO2 strongly depends on the gas sampling quality and on a regular/full breathing cycle. Adequate tidal volumes are required to reflect alveolar PCO2 and shallow breathing may result in too low etCO2 readings. In patient’s with lung disease such as COPD or lung perfusion/ventilation mismatch the quality of etCO2 further may deteriorate. In spontaneously breathing patients, making up the majority of patients in postoperative general care floor settings, the quality of etCO2 therefore is poor.
Being continuous, noninvasive, and independent from the quality of the airway transcutaneous pCO2 (tcpCO2) monitoring is the way of accurate PaCO2 estimation overcoming the drawbacks of etCO2 and the invasiveness of ABG’s. Furthermore, continous tcPCO2 montoring unambiguously reflects hypoventilation irrespectively of supplemental oxygen being administered or not and thereby helps to enhance patient safety.
For continuous ventilation and oxygenation monitoring on the general care floor the SenTec Digital Monitoring System offers the following key features:
Reliable Measurement Performance
Unique in industry tcpCO2 artifact detection/rejection algorithm
Lowest technical drift of the currently available tcpCO2 monitors Storre 2010.
- Combined tcpCO2/SpO2 monitoring being validated at a number of different measurement sites.
Remote Monitoring and secondary alarm suveillance
Remote Monitoring and secondary alarm surveillance with V-CareNeT™ System for up to 20 SenTec Digital Monitors (SDM). For each patient admitted to V-CareNeT™ system the central station on-line displays tcPCO2, SpO2, PR and alarms.
- Setup of V-CareNeT™ is easy and only requires a conventional Ethernet network, at least one SDM, a PC serving as a central station with V-STATS™ installed and V-CareNeT™ Package activated.
Comprehensive Data Management
On-screen viewing and printing of graphical trends and statistical summary for selected measurement(s).
Memory capacity of up to 12 days monitoring time
- V-STATS™ (PC software) enabling trend data download via the network for subsequent data analysis, reporting, and printing
Safe Sensor Temperature Management
- No burns due to sophisticated temperature management being optimized far above conventional standards of transcutaneous monitoring
Just one sensor to simultaneously monitor tcpCO2 and SpO2, which can be applied to various measurement sites
tcPCO2 monitoring unambiguously helps to detect hypoventilations that may be critically delayed or missed by SpO2 monitoring alone
Unique in industry SMART CALMEM function a) allowing to disconnect the digital V-Sign™ Sensor within a disconnection time of up to 30 minutes without an additional calibration request after reconnection and b) resulting in fewer calibration
Calibration interval of typically 12 hours allowing continuous monitoring of up to 12 hours
Membrane change interval of up to 42 days
Dedicated Parameters Setting for general care floor use (no auditory signals at the bed-side, display in sleep mode)
Various preconfigured, user-selectable measurement screens
Monitor mountable on roll/infusion stands, wall mounts/railings
- Flip feet serving as carrying handle or to adjust angle for improved table top viewing
 Frank J. Overdyk, Postoperative Respiratory Depression and Opioids, Initiatives in Safe Patient Care, Initiatives.
 Weinger MB. Dangers of postoperative opioids: APSF workshop and white paper address prevention of postoperative respiratory complications. APSF Newsletter Winter 2006-2007; 21:61-67.
 Stoelting and Weinger MB. Dangers of Postoperative Opioids - Is there a Cure? APSF Newsletter Summer 2009; 24:25-26.
 JCAHO, Patient controlled analgesia by proxy, Sentinel Event Alert 33, December 20, 2004
 Practice Guidelines for the Perioperative Management of Patients with Obstructive Sleep Apnea, Anesthesiology 2006; 104:1081–93