Authors: Dong Y et al.
Anesthesia & Analgesia 142(2):264-273, February 2026.
This prospective observational study evaluated a new phonomyography (PMG) prototype device for quantitative neuromuscular monitoring and compared it with the widely used acceleromyography device, the Train-of-Four Watch SX (TOF-Watch SX). Quantitative neuromuscular monitoring is increasingly recommended to reduce the risk of residual neuromuscular blockade after surgery, but currently available technologies each have practical limitations. Phonomyography is a method that detects the acoustic signals produced by muscle contractions and converts them into measurable data, potentially providing a simple and interference-resistant monitoring technique.
The investigators enrolled 102 surgical patients at a single center, with 80 ultimately included in the final analysis. The goal was to evaluate the performance of the PMG prototype under the effects of different neuromuscular blocking agents (NMBs). Patients were divided into three groups based on the drug used:
• Group C – cisatracurium
• Group V – vecuronium
• Group S – succinylcholine
Both the PMG prototype and the TOF-Watch SX were placed on the same hand to monitor the adductor pollicis muscle. Measurements were taken from the time of neuromuscular blocker administration until recovery to a train-of-four ratio (TOFr) of at least 0.9, which is commonly used to define adequate recovery from neuromuscular blockade.
For non-depolarizing neuromuscular blockers (cisatracurium and vecuronium), the PMG device recorded significantly longer onset times than the TOF-Watch SX. Median onset time for cisatracurium was approximately 210 seconds with the PMG device compared with 150 seconds using TOF-Watch SX. Similar findings were seen with vecuronium.
Recovery times showed the opposite trend. The PMG prototype consistently measured shorter full recovery times compared with the acceleromyography device. For example, in the cisatracurium group, recovery time averaged approximately 4014 seconds using PMG versus 5072 seconds with TOF-Watch SX. Similar differences were observed with vecuronium.
The same overall pattern was also seen with the depolarizing agent succinylcholine, although the sample size for this group was smaller. The PMG system recorded a slightly longer onset time and a shorter recovery time compared with TOF-Watch SX.
These findings suggest that although the PMG prototype provides stable and clinically feasible measurements across different neuromuscular blocking agents, its results are not interchangeable with those obtained using acceleromyography. The systematic differences in onset and recovery measurements indicate that clinicians would need device-specific interpretation thresholds if PMG technology is adopted in practice.
The authors note that PMG offers several potential advantages. The technology is relatively resistant to electrical interference, may allow monitoring at multiple muscle sites, and could simplify sensor placement compared with some existing devices. However, additional validation studies will be required before the