- Photoplethysmographic characterization of vascular tone mediated changes in arterial pressure: an observational study. [Journal Article]
- JCJ Clin Monit Comput 2018 Dec 15
- To determine whether a classification based on the contour of the photoplethysmography signal (PPGc) can detect changes in systolic arterial blood pressure (SAP) and vascular tone. Episodes of normot...
To determine whether a classification based on the contour of the photoplethysmography signal (PPGc) can detect changes in systolic arterial blood pressure (SAP) and vascular tone. Episodes of normotension (SAP 90-140 mmHg), hypertension (SAP > 140 mmHg) and hypotension (SAP < 90 mmHg) were analyzed in 15 cardiac surgery patients. SAP and two surrogates of the vascular tone, systemic vascular resistance (SVR) and vascular compliance (Cvasc = stroke volume/pulse pressure) were compared with PPGc. Changes in PPG amplitude (foot-to-peak distance) and dicrotic notch position were used to define 6 classes taking class III as a normal vascular tone with a notch placed between 20 and 50% of the PPG amplitude. Class I-to-II represented vasoconstriction with notch placed > 50% in a small PPG, while class IV-to-VI described vasodilation with a notch placed < 20% in a tall PPG wave. 190 datasets were analyzed including 61 episodes of hypertension [SAP = 159 (151-170) mmHg (median 1st-3rd quartiles)], 84 of normotension, SAP = 124 (113-131) mmHg and 45 of hypotension SAP = 85(80-87) mmHg. SAP were well correlated with SVR (r = 0.78, p < 0.0001) and Cvasc (r = 0.84, p < 0.0001). The PPG-based classification correlated well with SAP (r = - 0.90, p < 0.0001), SVR (r = - 0.72, p < 0.0001) and Cvasc (r = 0.82, p < 0.0001). The PPGc misclassified 7 out of the 190 episodes, presenting good accuracy (98.4% and 97.8%), sensitivity (100% and 94.9%) and specificity (97.9% and 99.2%) for detecting episodes of hypotension and hypertension, respectively. Changes in arterial pressure and vascular tone were closely related to the proposed classification based on PPG waveform. Clinical Trial Registration NTC02854852.
- Reliability of effective arterial elastance using peripheral arterial pressure as surrogate for left ventricular end-systolic pressure. [Journal Article]
- JCJ Clin Monit Comput 2018 Dec 14
- To compare the effective arterial elastance (Ea) obtained from the arterial pressure with Ea calculated from left-ventricular (LV) pressure-volume analysis. Experimental study. LV pressure-volume dat...
To compare the effective arterial elastance (Ea) obtained from the arterial pressure with Ea calculated from left-ventricular (LV) pressure-volume analysis. Experimental study. LV pressure-volume data was obtained with a conductance catheter and arterial pressures were measured via a fluid-filled catheter placed in the proximal aorta, femoral and radial arteries. Ea was calculated as LV end-systolic pressure (ESP)/stroke volume (SV). Experimental protocol consisted sequentially changing afterload (phenylephrine/nitroprusside), preload (bleeding/fluid), and contractility (esmolol/dobutamine). 90% of systolic pressure (Eaao_SYS, Eafem_SYS, Earad_SYS), mean arterial pressure (Eaao_MAP, Eafem_MAP, Earad_MAP), and dicrotic notch pressure (Eaao_DIC, Eafem_DIC, Earad_DIC) were used as surrogates for LV ESP. SV was calculated from the LV pressure-volume data. When Ea was compared with estimations based on 90% SAP, the relationship was r2 = 0.95, 0.94 and 0.92; and the bias and limits of agreement (LOA): - 0.01 ± 0.12, - 0.09 ± 0.12, - 0.05 ± 0.15 mmHg ml-1, for Eaao_SYS, Eafem_SYS and Earad_SYS, respectively. For estimates using dicrotic notch, the relationship was r2 = 0.94, 0.95 and 0.94 for Eaao_DIC, Eafem_DIC and Earad_DIC, respectively; with a bias and LOA: 0.05 ± 0.11, 0.06 ± 0.12, 0.10 ± 0.12 mmHg ml-1, respectively. When Ea was compared with estimates using MAP, the relationship was r2 = 0.95, 0.96 and 0.95 for Eaao_MAP, Eafem_MAP and Earad_MAP, respectively; with a bias and LOA: 0.05 ± 0.11, 0.06 ± 0.11, 0.06 ± 0.11 mmHg ml-1, respectively. LV ESP can be estimated from the arterial pressure. Provided that the SV measurement is reliable, the ratio MAP/SV provides a robust Ea surrogate over a wide range of hemodynamic conditions and is interchangeably in any peripheral artery, so it should be recommended as an arterial estimate of Ea in further research.
- Closed-loop vasopressor control: in-silico study of robustness against pharmacodynamic variability. [Journal Article]
- JCJ Clin Monit Comput 2018 Dec 11
- Initial feasibility of a novel closed-loop controller created by our group for closed-loop control of vasopressor infusions has been previously described. In clinical practice, vasopressor potency ma...
Initial feasibility of a novel closed-loop controller created by our group for closed-loop control of vasopressor infusions has been previously described. In clinical practice, vasopressor potency may be affected by a variety of factors including other pharmacologic agents, organ dysfunction, and vasoplegic states. The purpose of this study was therefore to evaluate the effectiveness of our controller in the face of large variations in drug potency, where 'effective' was defined as convergence on target pressure over time. We hypothesized that the controller would remain effective in the face up to a tenfold variability in drug response. To perform the robustness study, our physiologic simulator was used to create randomized simulated septic patients. 250 simulated patients were managed by the closed-loop in each of 7 norepinephrine responsiveness conditions: 0.1 ×, 0.2 ×, 0.5 ×, 1 ×, 2 ×, 5 ×, and 10 × expected population response to drug dose. Controller performance was evaluated for each level of norepinephrine response using Varvel's criteria as well as time-out-of-target. Median performance error and median absolute performance error were less than 5% in all response levels. Wobble was below 3% and divergence remained negative (i.e. the controller tended to converge towards the target over time) in all norepinephrine response levels, but at the highest response level of 10 × the value approached zero, suggesting the controller may be approaching instability. Response levels of 0.1 × and 0.2 × exhibited significantly higher time-out-of-target in the lower ranges (p < 0.001) compared to the 1 × response level as the controller was slower to correct the initial hypotension. In this simulation study, the closed-loop vasopressor controller remained effective in simulated patients exhibiting 0.1 to 10 × the expected population drug response.
- A retrospective evaluation of the risk of bias in perioperative temperature metrics. [Journal Article]
- JCJ Clin Monit Comput 2018 Dec 08
- The prevention and treatment of hypothermia is an important part of routine anesthesia care. Avoidance of perioperative hypothermia was introduced as a quality metric in 2010. We sought to assess the...
The prevention and treatment of hypothermia is an important part of routine anesthesia care. Avoidance of perioperative hypothermia was introduced as a quality metric in 2010. We sought to assess the integrity of the perioperative hypothermia metric in routine care at a single large center. Perioperative temperatures from all anesthetics of at least 60 min duration between January 2012 and 2017 were eligible for inclusion in analysis. Temperatures were displayed graphically, assessed for normality, and analyzed using paired comparisons. Automatically-recorded temperatures were obtained from several monitoring sites. Provider-entered temperatures were non-normally distributed, exhibiting peaks at temperatures at multiples of 0.5 °C. Automatically-acquired temperatures, on the other hand, were more normally distributed, demonstrating smoother curves without peaks at multiples of 0.5 °C. Automatically-acquired median temperature was highest, 36.8 °C (SD = 0.8 °C), followed by the three manually acquired temperatures (nurse-documented postoperative temperature, 36.5 °C [SD = 0.6 °C]; intraoperative manual temperature, 36.5 °C [SD = 0.6 °C]; provider-documented postoperative temperature, 36.1 °C [SD = 0.6 °C]). Provider-entered temperatures exhibit values that are unlikely to represent a normal probability distribution around a central physiologic value. Manually-entered perioperative temperatures appear to cluster around salient anchoring values, either deliberately, or as an unintended result driven by cognitive bias. Automatically-acquired temperatures may be superior for quality metric purposes.
- Oxygen reserve index (ORi™) contributes to prediction of hypoxemia and patient safety during tracheal stent insertion using rigid bronchoscopy: a case report. [Journal Article]
- JCJ Clin Monit Comput 2018 Dec 05
- The oxygen reserve index (ORi™) is a new noninvasive and continuous variable, which represents a moderate hyperoxygenation status, with a unitless scale between 0.00 and 1.00. When percutaneous oxyge...
The oxygen reserve index (ORi™) is a new noninvasive and continuous variable, which represents a moderate hyperoxygenation status, with a unitless scale between 0.00 and 1.00. When percutaneous oxygen saturation (SpO2) exceeds 100%, arterial blood oxygen partial pressure cannot be evaluated without performing arterial blood gas analysis. Because of significant air leakage during rigid bronchoscopy, it is difficult to monitor respiration using capnography, which does not measure end-tidal carbon dioxide (ETCO2) accurately. A 66-year-old man (175 cm, 76.8 kg) with a chief complaint of difficulty in breathing was diagnosed with a thyroid tumor. Computed tomography revealed tracheal stenosis due to direct invasion of the thyroid tumor; therefore, tracheal stenting was planned immediately. After supplying 6 L/min oxygen with a face mask and administering 180 mg of propofol intravenously, the supraglottic airway was intubated. General anesthesia (total intravenous anesthesia) through continuous administration of 6-10 mg/kg/h of propofol and intermittent administration of 50 µg of fentanyl (total 200 µg) preserved spontaneous breathing. During tracheal stent insertion, disconnection between the oxygen supply system and rigid bronchoscopy, and tracheal stent expansion, the ORi tended to decrease before SpO2 decreased. Thus, measuring ORi could prevent hypoxemia during tracheal stent insertion using rigid bronchoscopy.
- Mindray 3-directional NMT Module (a new generation "Tri-axial" neuromuscular monitor) versus the Relaxometer mechanomyograph and versus the TOF-Watch SX acceleromyograph. [Journal Article]
- JCJ Clin Monit Comput 2018 Dec 05
- Recently introduced Mindray "3-directional" neuromuscular transmission transducer (NMT, Shenzhen, China) acceleromyograph) claim to monitor thumb movement in 3 different directions. We compared NMT w...
Recently introduced Mindray "3-directional" neuromuscular transmission transducer (NMT, Shenzhen, China) acceleromyograph) claim to monitor thumb movement in 3 different directions. We compared NMT with the gold standard Relaxometer® mechanomyograph (MMG, Groningen University, Netherlands) in Study-1 and with TOF-Watch SX™ (WTCH) acceleromyograph from which it was developed in Study-2. We used first twitch (T1%) and train-of-four (TOF) ratio rocuronium 0.6 mg kg-1 neuromuscular block to evaluate NMT diagnostic accuracy in indicating 3 clinically relevant time points namely; MMG T1 5% (95% twitch depression) for tracheal intubation, MMG T1 25% for repeat neuromuscular blocking agents (NMBAs) administration, and MMG 0.9 TOF ratio full neuromuscular block recovery. We compared onset time (time from beginning of rocuronium administration until maximal depression), Dur25 (time until T1 25% recovery) and Dur0.9 (time until 0.9 TOF ratio recovery). In Study-1, NMT showed low sensitivity in indicating MMG time for tracheal intubation, repeat NMBAs administration and full neuromuscular block recovery (6.25%, 38.9% and 38.9% respectively). NMT onset time, Dur25 and Dur0.9 (2:51 ± 00:57, 36:50 ± 24:25, 70:08 ± 25:27 min:s) were significantly longer than MMG (1:56 ± 00:46, 30:26 ± 20:24, 62:03 ± 20:01). In Study-2, NMT onset time, Dur25 and Dur0.9 (02:37 ± 00:53, 35:38 ± 11:54, 53:40 ± 13:49) were not significantly different than WTCH (02:23 ± 00:45, 33:27 ± 12:51, 53:57 ± 12:47). NMT could not efficaciously detect MMG time for tracheal intubation; NMBAs repeat dose administration or full neuromuscular block recovery. Data from NMT cannot be used interchangeably with MMG. Our study revealed that NMT Tri-axial acceleromyography seems to offer no advantage over the MMG gold standard or the classic Mono-axial TOF-Watch SX monitor.
- Patient intermittent epidural boluses (PIEB) plus very low continuous epidural infusion (CEI) versus patient-controlled epidural analgesia (PCEA) plus continuous epidural infusion (CEI) in primiparous labour: a randomized trial. [Journal Article]
- JCJ Clin Monit Comput 2018 Nov 30
- Epidural maintenance technique for labour analgesia updates constantly. Thanks to infusion pumps, the recently developed programmed intermittent epidural bolus (PIEB) may reduce the use of anesthetic...
Epidural maintenance technique for labour analgesia updates constantly. Thanks to infusion pumps, the recently developed programmed intermittent epidural bolus (PIEB) may reduce the use of anesthetic drugs and minimize unintended consequences such as cardio or neurotoxicity. Nevertheless, it is not yet a general practice. So far, there are no comparative studies in the literature that address levobupivacaine-based CEI + PCEA versus CEI + PIEB + PCEA. A randomized double-blind trial was carried out to evaluate if PIEB could reduce local anesthetic use compare to PCEA. Primiparous pregnant patients were divided into two groups: PIEB group (continuous infusion plus intermittent automatic doses) and PCEA group (continuous infusion plus PCEA). The primary objective was to analyze the differences between both groups regarding levobupivacaine total dose. The secondary objectives were to find out the differences concerning pain control, motor blockage, satisfaction score, labour time and delivery outcomes. Statistical analyses were done by protocol. The study recruited 200 patients (103 PIEB, 97 PCEA). The total dose administered was significantly higher in PIEB group: PCEA group 52.97 mg, IC 95% 45.65-60.28 mg and PIEB group 62.04 mg, IC 95% 55.46-68.61 mg (p = 0.021). PIEB group required fewer top up boluses (median value1; range 0-2) than CEI + PCEA group (median value 6; range 3-9) p < 0.05. Satisfaction scores were higher in PIEB group (p = 0.039, CI 95% 1.23-1.42). CEI + PIEB was found to be a good alternative to CEI + PCEA with very high rates of satisfaction in both groups although it was higher in PIEB group. PIEB group required fewer PCEA boluses. Further studies are needed to determine the best approach for epidural pain management.Clinical Trial Number and Registry URL: NCT03133091 ( https://clinicaltrials.gov/ct2/show/NCT03133091?term=MB+Rodriguez&rank=1) .
- Identification of return of spontaneous circulation during cardiopulmonary resuscitation via pulse oximetry in a porcine animal cardiac arrest model. [Journal Article]
- JCJ Clin Monit Comput 2018 Nov 29
- In this prospective study we investigated whether the pulse oximetry plethysmographic waveform (POP) could be used to identify return of spontaneous circulation (ROSC) during cardio-pulmonary resusci...
In this prospective study we investigated whether the pulse oximetry plethysmographic waveform (POP) could be used to identify return of spontaneous circulation (ROSC) during cardio-pulmonary resuscitation (CPR). Tweleve pigs (28 ± 2 kg) were randomly assigned to two groups: Group I (non-arrested with compressions) (n = 6); Group II (arrested with CPR and defibrillation) (n = 6). Hemodynamic parameters and POP were collected and analyzed. POP was analyzed using both a time domain method and a frequency domain method. In Group I, when compressions were carried out on subjects with a spontaneous circulation, a hybrid fluctuation or "envelope" phenomenon appeared in the time domain method and a "double" or "fusion" peak appeared in the frequency domain method. In Group II, after the period of ventricular fibrillation was induced, the POP waveform disappeared. With compressions, POP showed a regular compression wave. After defibrillation, ROSC, and continued compressions, a hybrid fluctuation or "envelope" phenomenon appeared in the time domain method and a "double" or "fusion" peak appeared in the frequency domain method, similar to Group I. Analysis of POP using the time and frequency domain methods could be used to identify ROSC during CPR.
- Phenylephrine-induced recruitable preload from the venous side. [Editorial]
- JCJ Clin Monit Comput 2018 Nov 26
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- Acoustic respiration rate and pulse oximetry-derived respiration rate: a clinical comparison study. [Journal Article]
- JCJ Clin Monit Comput 2018 Nov 26
- Respiration rate (RR) is a critical vital sign that provides early detection of respiratory compromise. The acoustic technique of measuring continuous respiration rate (RRa) interprets the large airw...
Respiration rate (RR) is a critical vital sign that provides early detection of respiratory compromise. The acoustic technique of measuring continuous respiration rate (RRa) interprets the large airway sound envelope to calculate respiratory rate while pulse oximetry-derived respiratory rate (RRoxi) interprets modulations of the photoplethsymograph in response to hemodynamic changes during the respiratory cycle. The aim of this study was to compare the performance of these technologies to each other and to a capnography-based reference device. Subjects were asked to decrease their RR from 14 to 4 breaths per minute (BPM) and then increase RR from 14 to 24 BPM. The effects of physiological noise, ambient noise, and head movement and shallow breathing on device performance were also evaluated. The test devices were: (1) RRa, Radical-7 (Masimo Corporation), (2) RRoxi, Nellcor™ Bedside Respiratory Patient Monitoring System (Medtronic), and (3) reference device, Capnostream20p™ (Medtronic). All devices were configured with their default settings. Twenty-nine healthy adult subjects were included in the study. During abrupt changes in breathing, overall RRoxi was accurate for longer periods of time than RRa; specifically, RRoxi was more accurate during low and normal RR, but not during high RR. RRoxi also displayed a value for significantly longer time periods than RRa when the subjects produced physiological sounds and moved their heads, but not during shallow breathing or ambient noise. RRoxi may be more accurate than RRa during development of bradypnea. Also, RRoxi may display a more reliable RR value during routine patient activities.