Experimental validation of the CompuFlo® epidural controlled system to identify the epidural space and its clinical use in difficult obstetric cases

Loss-of-Resistance Versus Dynamic Pressure-Sensing Technology for Successful Placement of Thoracic Epidural Catheters: A Randomized Clinical Trial

BACKGROUND

The traditional loss-of-resistance (LOR) technique for thoracic epidural catheter placement can be associated with a high primary failure rate. In this study, we compared the traditional LOR technique and dynamic pressure-sensing (DPS) technology for primary success rate and secondary outcomes pertinent to identifying the thoracic epidural space.

METHODS

This pragmatic, randomized, patient- and assessor-blinded superiority trial enrolled patients ages 18 to 75 years, scheduled for major thoracic or abdominal surgeries at a tertiary care teaching hospital. Anesthesiology trainees (residents and fellows) placed thoracic epidural catheters under faculty supervision and rescue. The primary outcome was the success rate of thoracic epidural catheter placement, evaluated by the loss of cold sensation in the thoracic dermatomes 20 minutes after injecting the epidural test dose. Secondary outcomes included procedural time, ease of catheter placement, the presence of a positive falling meniscus sign, early hemodynamic changes, and unintended dural punctures. Additionally, we explored outcomes that included number of attempts, needle depth to epidural space, need for faculty to rescue the procedure from the trainee, patient-rated procedural discomfort, pain at the epidural insertion site, postoperative pain scores, and opioid consumption over 48 hours.

RESULTS

Between March 2019 and June 2020, 133 patients were enrolled; 117 were included in the final analysis (n = 57 for the LOR group; n = 60 for the DPS group). The primary success rate of epidural catheter placement was 91.2% (52 of 57) in the LOR group and 96.7% (58 of 60) in the DPS group (95% confidence interval [CI] of difference in proportions: -0.054 [-0.14 to 0.03]; P = .264). No difference was observed in procedural time between the 2 groups (median interquartile range [IQR] in minutes: LOR 5.0 [7.0], DPS 5.5 [7.0]; P = .982). The number of patients with epidural analgesia onset at 10 minutes was 49.1% (28 of 57) in the LOR group compared to 31.7% (19 of 60) in the DPS group (P = .062). There were 2 cases of unintended dural punctures in each group. Other secondary or exploratory outcomes were not significantly different between the groups.

CONCLUSIONS

Our trial did not establish the superiority of the DPS technique over the traditional LOR method for identifying the thoracic epidural space (Clinicaltrials.gov identifier: NCT03826186).

FBG-Based Soft System for Assisted Epidural Anesthesia: Design Optimization and Clinical Assessment

Fiber Bragg grating sensors (FBGs) are considered a valid sensing solution for a variety of medical applications. The last decade witnessed the exploitation of these sensors in applications ranging from minimally invasive surgery to biomechanics and monitoring physiological parameters. Recently, preliminary studies investigated the potential impact of FBGs in the management of epidural procedures by detecting when the needle reaches the epidural space with the loss of resistance (LOR) technique. In this article, we propose a soft and flexible FBG-based system capable of detecting the LOR, we optimized the solution by considering different designs and materials, and we assessed the feasibility of the optimized soft sensor (SS) in clinical settings. The proposed SS addresses some of the open challenges in the use of a sensing solution during epidural punctures: it has high sensitivity, it is non-invasive, the sensing element does not need to be inserted within the needle, and the clinician can follow the standard clinical practice. Our analysis highlights how the material and the design impact the system response, and thus its performance in this scenario. We also demonstrated the system’s feasibility of detecting the LOR during epidural procedures.

Pressure monitoring devices may undetect epidural space: a report on the use of Compuflo® system for epidural injection

Lumbar epidural infiltration (EI) is a feasible procedure performed in pain therapy. Even though epidural analgesia is widely applied, it remains a blind technique, based on the operator's hand sensations, and it is associated with significant failure rate and several potential complications. Compuflo® (Compuflo, Milestone Scientific, Livingston, NJ) is a computerized injection pump which precisely detects the real time pressure at the tip of a Tuohy needle when placed in human tissues, thanks to a continuous fluid path. In our institution, we usually perform EI for chronic back pain guided by the Compuflo device, especially for expected difficult procedures. However, we report 6 false negative cases on a total number of 60 procedures in which the Compuflo system didn't meet the criteria of epidural space entry, even though the epidural space was actually reached. A mild pressure decrease (less than 50%) which lasted for more than 5 s was reported on the monitor, and the acoustic signal changed in a little bit lower sound, without a clear indication on stopping or not the needle advancement. This unspecific drop in monitored pressure gives false negatives using the Compuflo® system and may lead to excessive advancing of the needle. In conclusion, we consider the epidural pressure monitoring device Compuflo as a tool which may be able to ease the correct positioning of an epidural needle. The percentage of 10% false negative identifications of the epidural space in our case series however suggests more investigations on adequate or specific settings for this epidural system. In the meantime, in chronic pain patients, this anesthetic technique should only be used by experienced hands.

Soft System Based on Fiber Bragg Grating Sensor for Loss of Resistance Detection during Epidural Procedures: In Silico and In Vivo Assessment

Epidural analgesia represents a clinical common practice aiming at pain mitigation. This loco-regional technique is widely used in several applications such as labor, surgery and lower back pain. It involves the injections of anesthetics or analgesics into the epidural space (ES). The ES detection is still demanding and is usually performed by the techniques named loss of resistance (LOR). In this study, we propose a novel soft system (SS) based on one fiber Bragg grating sensor (FBG) embedded in a soft polymeric matrix for LOR detection during the epidural puncture. The SS was designed to allow instrumenting the syringe's plunger without relevant modifications of the anesthetist's sensations during the procedure. After the metrological characterization of the SS, we assessed the capability of this solution in detecting LOR by carrying it out in silico and in clinical settings. For both trials, results revealed the capability of the proposed solutions in detecting the LOR and then in recording the force exerted on the plunger.

Analysis of Epidural Waveform to Determine Correct Epidural Catheter Placement After CSE Labor Analgesia

Background

The epidural pressure is pulsatile and synchronized with arterial pulsations. Monitoring the epidural waveform has been suggested as a technique to reliably confirm the appropriate localization of the epidural catheter.

Objective

The aim of this study was to evaluate the sensitivity and specificity of the Computer Controlled Drug Delivery System with continuous pressure and waveform sensing technology (CCDDS) (CompuFlo^® CathCheck™) as an instrument to assess the correct placement of the catheter in the epidural space in parturients who have received combined spinal-epidural technique (CSE) for labor analgesia.

Methods

We enrolled 40 consecutive healthy patients undergoing CSE labor analgesia with successful analgesia. All the cases in which pulsatile waveforms in synchrony with heart rate were detected were considered to be true positives; all the cases in which there was the absence of pulsatile waves were followed up. If these patients had to eventually relocate or manipulate the epidural catheter, they were considered to be true negative. If the absence of pulse waves was observed in the presence of successful analgesia during labor, the patients were considered to be false negatives.

Results

Pulsatile waveforms synchronous with heart rate were observed in 33 cases associated with adequate analgesia. In 5 cases, the pulsatile waveforms were absent due to unilateral analgesia or catheter occlusion (true negatives). In 2 cases, the patients had effective analgesia but we were not able to observe a distinct pulsatile waveform. The pressure waveform analysis through the epidural catheter had a sensitivity of 95%, a positive predictive value of 100%, a specificity of 100% and a negative predictive value of 60%.

Conclusion

Pulsatile pressure waveform recording with CCDDS through the epidural catheter resulted in high sensitivity and positive predictive value which can help the proper placement of the epidural catheter.

Epidural Needle Extension through the Ligamentum Flavum Using the Standard versus the CompuFlo®-Assisted Loss of Resistance to Saline Technique: A Simulation Study

Background. The CompuFlo® epidural system has been recently introduced and validated as an objective and sensible tool to detect the epidural space. We aimed to verify whether the high sensitivity of the instrument may help the anesthesiologist to identify the epidural space very early, limiting the extension of the Tuohy needle into the epidural space. Methods. In this prospective, simulation study, we evaluated the Tuohy needle extension through a simulated ligamentum flavum during the epidural procedure performed by 52 expert anesthesiologists by using the CompuFlo® epidural instrument or their standard loss of resistance to saline technique (LORT). Results. The mean (SD) needle extension length was 3.90 (3.71) mm in the standard technique group and 0.68 (0.46) mm in the CompuFlo® group (P<000001). The extremely reduced variability of the data in the CompuFlo® group (F test 0.01) made the results obtained with this instrument highly predictable. Conclusions. Puncturing high-resistance material that simulated the ligamentum flavum, the use of CompuFlo® has determined the arrest of the needle more precociously when compared with the traditional LORT.

[Identification of the epidural space using pressure waveform analysis (CompuFlo® technology): a case series]

Anesthesiologists commonly perform the loss of resistance technique in order to identify the epidural space during neuraxial procedures; however, this technique is subjective and lacks reliability in certain cases. The so-called CompuFlo® technology provides objective information about the position of the epidural needle by means of a pressure curve and acoustic signals. The technology was introduced several years ago and was evaluated in several trials, which showed promising results. The purpose of the present publication is to report on the first experiences with the CompuFlo® technology in German-speaking countries. A series of 24 epidural procedures using the CompuFlo® device was carried out in routine daily practice. The epidural space was successfully identified in 23 cases. Conversion to the conventional loss of resistance technique was performed during the initial cases in a prolonged procedure. The CompuFlo® technique is considered to be a promising technology, which might help to reduce complications after epidural anesthesia, e.g. postdural puncture headache.

Compuflo®-Assisted Training vs Conventional Training for the Identification of the Ligamentum Flavum with an Epidural Simulator: A Brief Report

The ability of recognizing the ligamentum flavum is the first, crucial, important skill to teach novices when they are learning the epidural technique. The aim of this preliminary prospective study was to evaluate whether the Compuflo® Epidural instrument may help inexperienced trainees to better identify the ligamentum flavum during an epidural simulator training session. Compuflo® reduced the total number of attempts to identify the ligamentum flavum and increased three fold the chance to identify it at the first attempt during a simulator-assisted training module, making this identification easier for inexperienced trainees. This trial is registered with NCT03812926.

Recent technological advancements in regional anesthesia

Just two decades ago, regional anesthesia was performed blindly with dubious outcomes and little support from surgeons and patients. Technological advances in regional anesthesia have revolutionized techniques and largely improved outcomes. Ultrasound (US) technology continues to advance and has become more affordable. Improvements have come in the form of picture quality, resolution, portability, and smaller equipment. The US technology can identify otherwise unrecognized pathology and can help to optimize patient flow by allowing for more accurate triage and effective treatments and providing timelier interventions. In recent years, several different strategies to help improve and ease US-guided needle identification and placement have been developed, including magnetically guided needle US technology. Three-dimensional (3D) and four-dimensional (4D) US use is another potential way to help improve first-pass success and limit patient harm for regional anesthetics. The advent of echogenic needles and the resulting improvement in needle visualization under US has had a positive impact on physician comfort in performing regional anesthesia and on visualization time of the needle during US-guided procedures. To reduce variability and to reduce the anesthesiologist's workload, the use of robots in regional anesthesia has been assessed in recent years. Peripheral nerve stimulation (PNS) has also demonstrated efficacy in acute and chronic pain settings. Additional research and randomized controlled trials are necessary to evaluate novel technologies.

Differentiating False Loss of Resistance from True Loss of Resistance While Performing the Epidural Block with the CompuFlo® Epidural Instrument

Background

The occurrence of false losses of resistance may be one of the reasons for inadequate or failed epidural block. A CompuFlo® epidural instrument has been introduced to measure the pressure of human tissues in real time at the orifice of a needle and has been used as a tool to identify the epidural space. The aim of this study was to investigate the sensitivity and the specificity of the ability of CompuFlo® to differentiate the false loss of resistance from the true loss of resistance encountered during the epidural space identification procedure.

Method

We performed epidural block with the CompuFlo® epidural instrument in 120 healthy women who requested labor epidural analgesia. The epidural needle was considered to have reached the epidural space when an increase in pressure (accompanied by an increase in the pitch of the audible tone) was followed by a sudden and sustained drop in pressure for more than 5 seconds accompanied by a sudden decrease in the pitch of the audible tone, resulting in the formation of a low and stable pressure plateau. We evaluate the sensitivity, specificity, and positive and negative predictive values of the ability of CompuFlo® recordings to correctly identify the true LOR from the false LOR.

Results

The drop in pressure associated with the epidural space identification was significantly greater than that recorded after the false loss of resistance (73% vs 33%) (P=0.000001). The sensitivity was 0.83, and the AUC was 0.82.

Discussion

We have confirmed the ability of CompuFlo® to differentiate the false loss of resistance from the true loss of resistance and established its specificity and sensitivity.

Conclusion

An easier identification of dubious losses of resistance during the epidural procedure is essential to reduce the number of epidural attempts and/or needle reinsertions with the potential of a reduced risk of accidental dural puncture especially in difficult cases or when the procedure is performed by trainees.