To clarify features of photoplethysmography in monitoring balanced anesthesia, compared with Cerebral State Index

Photoplethysmography temporal marker-based machine learning classifier for anesthesia drug detection

Anesthesia drug overdose hazards and lack of gold standards in anesthesia monitoring lead to an urgent need for accurate anesthesia drug detection. To investigate the PPG waveform features affected by anesthesia drugs and develop a machine-learning classifier with high anesthesia drug sensitivity. This study used 64 anesthesia and non-anesthesia patient data (32 cases each), extracted from Queensland and MIMIC-II databases, respectively. The key waveform features (total area, rising time, width 75%, 50%, and 25%) were extracted from 16,310 signal recordings (5-s duration). Discriminant analysis, support vector machine (SVM), and K-nearest neighbor (KNN) were evaluated by splitting the dataset into halve training (11 patients, 8570 segments) and halve testing dataset (11 patients, 7740 segments). Significant differences exist between PPG waveform features of anesthesia and non-anesthesia groups (p < 0.05) except total area feature (p > 0.05). The KNN classifier achieved 91.7% (AUC = 0.95) anesthesia detection accuracy with the highest sensitivity (0.88) and specificity (0.90) as compared to other classifiers. Kohen’s kappa also shows almost perfect agreement (0.79) with the KNN classifier. The KNN classifier trained with significant PPG features has the potential to be used as a reliable, non-invasive, and low-cost method for the detection of anesthesia drugs for depth analysis during surgical operations and postoperative monitoring.

Effect of Laryngeal Mask Airway Insertion on Parameters Derived From Catacrotic Phase of Photoplethysmography Under Different Concentrations of Remifentanil

BACKGROUND

Some parameters have been extracted from photoplethysmography (PPG) with a good relativity with nociception, but without encouraging results in qualifying the balance of nociception-anti-nociception (NAN). The features of PPG have not been thoroughly depicted and more prospective univariate parameters deserve to be explored. The aim of this study was to investigate the ability of parameters derived from catacrotic phase of PPG to grade the level of analgesia.

METHODS

45 patients with ASA I or II were randomized to receive a remifentanil effect-compartment target controlled infusion (Ceremi) of 0, 1, or 3 ng/ml, and a propofol effect-compartment target controlled infusion to maintain an acceptable level of hypnosis with state entropy (SE) at 40~60. Laryngeal mask airway (LMA) insertion was applied as a noxious stimulus. Five diastole-related parameters, namely diastolic interval (DI), diastolic slope (DS), the minimum slope during catacrotic phase (DSmin), the interval between DSmin and its nearest trough (DTI), and area difference ratio (ADR), were extracted. Pulse beat interval (PBI) was calculated as a reference parameter.

RESULTS

LMA insertion elicited a significant variation in all parameters except ADR during Ceremi of 0 and 1 ng/ml. Compared to PBI (prediction probability ([Formula: see text]) = 0.796), the parameters of DI, DS, and DTI presented a better consistence with the level of anti-nociceptive medication, with [Formula: see text] of 0.825, 0.822, and 0.822 respectively.

CONCLUSION

The features extracted from catacrotic phase of PPG, including DI, DS, and DTI, could provide a promising potential to qualify the balance of NAN.

Comparison of speckleplethysmographic (SPG) and photoplethysmographic (PPG) imaging by Monte Carlo simulations and in vivo measurements

Noncontact photoplethysmography (PPG) is limited by a poor signal-to-noise ratio (SNR). A solution to this limitation is the use of alternate sources of optical contrast to generate a complementary pulsatile waveform. One such source is laser speckle contrast, which is modulated in biological tissues by the flow rate of red blood cells. Averaging a region of interest from a speckle contrast image over time allows for the calculation of a speckleplethysmogram (SPG). Similar to PPG, SPG enables monitoring of heart rate and respiratory rate. A gap in the knowledge base exists as to the precise spatiotemporal relationship between PPG and SPG signals. We have developed an eight-layer tissue model to simulate both PPG and SPG signals in a reflectance geometry via Monte Carlo methods. We modeled PPG by compression of the upper and lower blood nets due to expansion of the larger arterial layer below. The in silico PPG peak-to-peak amplitude percent was greater at 532 nm than at 860 nm (5.6% vs. 3.0%, respectively), which matches trends from the literature. We modeled SPG by changing flow speeds of red blood cells in both the capillaries and arterioles over the cardiac cycle. The in silico SPG peak-to-peak amplitude percent was 24% at 532 nm and 40% at 860 nm. In silico results are similar to in vivo results measured with a two-camera set up for simultaneous imaging of PPG and SPG. Both in silico and in vivo data suggest SPG has a much larger SNR than PPG, which may prove beneficial for noncontact, wide-field optical monitoring of cardiovascular health.

The Effect of Tracheal Intubation-Induced Autonomic Response on Photoplethysmography

Introduction. Intraoperative stress responses and postoperative pain can be monitored using photoplethysmography (PPG). PPG signal has two components, AC and DC. Effects of noxious stimuli-induced stress responses have not been studied on the DC component of PPG. The aim of this study was to investigate the effect of a known noxious stimulus (endotracheal intubation) on both the AC and DC components of PPG. Methods. 15 surgical patients having general anesthesia were enrolled into this clinical study. PPG was recorded electronically from a pulse oximeter. Maximum changes in the AC and DC components of the PPG and pulse rate were determined in response to endotracheal intubation from high frequency (62.5 Hz) PPG recordings. Results. Endotracheal intubation-induced autonomic stress response resulted in a significant decrease in the AC component of the PPG and an increase in pulse rate in every subject (p < 0.05 for all). The decrease in the AC component of the PPG was 50 ± 12% (p < 0.05) and the increase in pulse rate was 26 ± 10 bpm (p < 0.05). The response of the DC component was variable (p = NS). Conclusion. Endotracheal intubation-induced stress response resulted in a significant and consistent change in the AC, but not the DC component of the PPG. This trial is registered with ClinicalTrials.gov Identifier NCT03032939.

Comparison of propofol-hydromorphone and propofol-dexmedetomidine in patients with intubation after maxillofacial plastic surgery

Objective

To compare the sedation and analgesic effects between propofol–hydromorphone and propofol–dexmedetomidine in patients with postoperative intubation after maxillofacial plastic surgery.

Methods

Forty-two patients undertaking maxillofacial plastic surgery with intubation were randomly assigned into propofol plus hydromorphone (P–H) group or propofol plus dexmedetomidine (P–D) group, receiving intravenous infusion of P–H or P–D, respectively. Cerebral state index, Ramsay sedation score, arterial blood gas analysis, and physiology indices were recorded before admission (T0), 30 minutes (T1), 1 hour (T2), 2 hours (T3), 6 hours (T4), and 12 hours after admission (T5) to intensive care unit, and 10 minutes after extubation (T6). Blood interleukin-6 was measured with enzyme-linked immunosorbent assay.

Results

There was no significant difference in arterial blood gas analysis, oxygen saturation, mean arterial pressure, and respiratory rate between two groups at all time-points (P>0.05). The changes of heart rate (at T4, T5, and T6), cerebral state index (T1, T2, T3, T4, and T5), and Ramsay score (at T3) in P–H group were significantly different from that in P–D group (P<0.05). The plasma interleukin-6 at T4 in P–H group was significantly lower than that in P–D group (P<0.05).

Conclusion

The P–H approach takes advantages over P–D approach in relieving the pain and discomfort, reducing the overstimulation of sympathetic nerve and the stress level, and enhancing the tolerance of postoperative intubation after maxillofacial plastic surgery.