Reconstruction of missing channel in electroencephalogram using spatiotemporal correlation-based averaging.

Objective.Electroencephalogram (EEG) recordings often contain large segments with missing signals due to poor electrode contact or other artifact contamination. Recovering missing values, contaminated segments and lost channels could be highly beneficial, especially for automatic classification algorithms, such as machine/deep learning models, whose performance relies heavily on high-quality data. The current study proposes a new method for recovering missing segments in EEG.Approach.In the proposed method, the reconstructed segment is estimated by substitution of the missing part of the signal with the normalized weighted sum of other channels. The weighting process is based on inter-channel correlation of the non-missing preceding and proceeding temporal windows. The algorithm was designed to be computationally efficient. Experimental data from patients (N= 20) undergoing general anesthesia due to elective surgery were used for the validation of the algorithm. The data were recorded using a portable EEG device with ten channels and a self-adhesive frontal electrode during induction of anesthesia with propofol from waking state until burst suppression level, containing lots of variation in both amplitude and frequency properties. The proposed imputation technique was compared with another simple-structure technique. Distance correlation (DC) was used as a measure of comparison evaluation.Main results.: The proposed method, with an average DC of 82.48 ± 10.01 (µ± σ)%, outperformed its competitor with an average DC of 67.89 ± 14.12 (µ± σ)%. This algorithm also showed a better performance when increasing the number of missing channels.Significance.the proposed technique provides an easy-to-implement and computationally efficient approach for the reliable reconstruction of missing or contaminated EEG segments.

Doxapram as an additive to propofol sedation for endoscopic retrograde cholangiopancreatography: a placebo-controlled, randomized, double-blinded study.

BACKGROUND: Endoscopic retrograde cholangiopancreatography (ERCP) requires moderate to deep sedation, usually with propofol. Adverse effects of propofol sedation are relatively common, such as respiratory and cardiovascular depression. This study was conducted to determine if doxapram, a respiratory stimulant, could be used to reduce the incidence of respiratory depression. METHODS: This is a single-center, prospective randomized double-blind study performed in the endoscopy unit of Helsinki University Central Hospital. 56 patients were randomized in a 1:1 ratio to either receive doxapram as an initial 1 mg/kg bolus and an infusion of 1 mg/kg/h (group DOX) or placebo (group P) during propofol sedation for ERCP. Main outcome measures were apneic episodes and hypoxemia (SpO2 < 90%). Mann-Whitney test for continuous variables and Fisher's exact test for discrete variables were used and mixed effects modeling to take into account repeated measurements on the same subject and comparing both changes within a group as a function of time and between the groups. RESULTS: There were no statistically significant differences in apneic episodes (p = 0.18) or hypoxemia (p = 0.53) between the groups. There was a statistically significant rise in etCO2 levels in both groups, but the rise was smaller in group P. There was a statistically significant rise in Bispectral Index (p = 0.002) but not modified Observer's Assessment of Agitation/Sedation (p = 0.21) in group P. There were no statistically significant differences in any other measured parameters. CONCLUSIONS: Doxapram was not effective in reducing respiratory depression caused by deep propofol sedation during ERCP. Further studies are warranted using different sedation protocols and dosing regimens. Clinical trial registration ClinicalTrials.gov ID NCT02171910.

Assessment of sedation level for endoscopic retrograde cholangiopancreatography - a prospective validation study.

BACKGROUND AND AIMS: There is no consensus on how to assess the depth of sedation for endoscopic retrograde cholangiopancreatography (ERCP). This study was carried out in order to evaluate different methods of assessment of depth of sedation: bispectral index (BiS), modified Richmond Agitation/Sedation Scale (mRASS), modified Ramsay Sedation Scale (mRSS) and modified Observer Assessment of Alertness and Sedation (mOAAS) and their applicability to clinical practice. METHODS: Two hundred patients were recruited. Sedation was given by standard clinical practice using propofol sedation or patient controlled sedation. Sedation was assessed on all patients using the above-mentioned methods. BiS was considered the reference point for sedation scales. Cronbach's alpha was calculated to determine the consistency of different scales in respect to each other and prediction probability and Spearman's correlation coefficients of sedation scales were calculated to show the relationship between sedation scales and BiS. RESULTS: All scales showed high reliability with overall Cronbach's alpha 0.943. Dropping scales suggested better consistency between mOAAS, mRSS and mRASS than with BiS. Spearman's correlation and prediction probability showed similar results with all tested scales: mOAAS (0.695, 0.739), mRSS (0.673, 0.735), mRASS (0.683, 0.738), p < .01 for all scales. CONCLUSIONS: All tested methods were found to be reliable in the assessment of the depth of sedation when compared with each other. However, mRASS, mRSS and mOAAS require the patient to respond to verbal or tactile stimulus, which may impair execution of ERCP, whereas BiS information is collected directly from electroencephalogram and thus may be preferable in clinical setting.

How patient-controlled sedation is adopted in clinical practice of sedation for endoscopic retrograde cholangiopancreatography? A prospective study of 1196 cases.

OBJECTIVE: Patient-controlled sedation (PCS) has been shown to be a valid choice for sedation during endoscopic retrograde cholangiopancreatography (ERCP) in randomized studies. However, large-scale studies are lacking. MATERIAL AND METHODS: A single center, prospective observational study to determine how sedation for ERCP is administered in clinical setting. All 956 patients undergoing 1196 ERCPs in the endoscopy unit of Helsinki University Central Hospital 2012-2013, methods of sedation and adverse events associated with different sedations were recorded. RESULTS: PCS was attempted a total of 685 times (57%), successful use of PCS was achieved with 526 patients (77% of attempts). PCS device was operated by the anesthesiologist or anesthesia nurse 268 times (22%). PCS was more likely chosen for younger (80.6% for < =60 years vs. 63.8% for >60 years, p<.001) patients and by trainee anesthetists. Anesthesiologist administered propofol sedation was used 240 times (20%). The risk of failure of PCS was increased, if systolic arterial pressure was <90 mmHg, dosage of PCS >17 ml, duration of procedure exceeded 23 min. The risk of failure was lower in patients with primary sclerosing cholangitis (PSC) and if sedation was deeper RASS < =-2. Uneventful PCS was associated with less respiratory and cardiovascular depression than other methods. There were no statistically significant differences in safety profiles with all the methods of sedation. CONCLUSIONS: PCS is readily implemented in clinical practice, is suitable for younger and low-risk patients and is associated with less cardiorespiratory adverse effects.