Youngjoon Chee

The use of dual accelerometers improves measurement of chest compression depth

BACKGROUND Chest compression (CC) feedback devices are used to perform CC measurements effectively and accurately on patients in hospital beds. However, these devices do not take account of the compression of the mattress, which results in overestimation of CC depth. In this study, we propose a new method using two accelerometers to overcome this limitation and thus measure compression depth more accurately when performing cardiopulmonary resuscitation (CPR) on patients. METHOD One accelerometer was placed on the manikins sternum (a1), and the other between the manikins back and the mattress (a2). The compression depth was calculated by integrating the acceleration twice using a digital signal processing technique. We compared CC depth from dual accelerometers and single accelerometer (a1) on the foam and inflated air mattress with eight CPR providers. RESULT When CC was done on a manikin lying on the floor, there was no significant difference between measurement techniques (p>0.05). When CC was done on a manikin lying on the foam and inflated air mattress supporting system, our method significantly improved the estimation of CC depth, irrespective of the presence or absence of a backboard (p<0.001). CONCLUSION Measuring CC depth using two accelerometers is more effective than using one in increasing the accuracy of CC depth estimation when CPR is performed on the foam and inflated air mattress, regardless of the presence or absence of a backboard.

Personal Identification Based on Vectorcardiogram Derived from Limb Leads Electrocardiogram

We propose a new method for personal identification using the derived vectorcardiogram (dVCG), which is derived from the limb leads electrocardiogram (ECG). The dVCG was calculated from the standard limb leads ECG using the precalculated inverse transform matrix. Twenty-one features were extracted from the dVCG, and some or all of these 21 features were used in support vector machine (SVM) learning and in tests. The classification accuracy was 99.53%, which is similar to the previous dVCG analysis using the standard 12-lead ECG. Our experimental results show that it is possible to identify a person by features extracted from a dVCG derived from limb leads only. Hence, only three electrodes have to be attached to the person to be identified, which can reduce the effort required to connect electrodes and calculate the dVCG.

Videographic Analysis of Glottic View With Increasing Cricoid Pressure Force

STUDY OBJECTIVE Cricoid pressure may negatively affect laryngeal view and compromise airway patency, according to previous studies of direct laryngoscopy, endoscopy, and radiologic imaging. In this study, we assess the effect of cricoid pressure on laryngeal view with a video laryngoscope, the Pentax-AWS. METHODS This cross-sectional survey involved 50 American Society of Anesthesiologists status I and II patients who were scheduled to undergo elective surgery. The force measurement sensor for cricoid pressure and the video recording system using a Pentax-AWS video laryngoscope were newly developed by the authors. After force and video were recorded simultaneously, 11 still images were selected per 5-N (Newton; 1 N = 1 kg·m·s(-2)) increments, from 0 N to 50 N for each patient. The effect of cricoid pressure was assessed by relative percentage compared with the number of pixels on an image at 0 N. RESULTS Compared with zero cricoid pressure, the median percentage of glottic view visible was 89.5% (interquartile range [IQR] 64.2% to 117.1%) at 10 N, 83.2% (IQR 44.2% to 113.7%) at 20 N, 76.4% (IQR 34.1% to 109.1%) at 30 N, 51.0% (IQR 21.8% to 104.2%) at 40 N, and 47.6% (IQR 15.2% to 107.4%) at 50 N. The number of subjects who showed unworsened views was 20 (40%) at 10 N, 17 (34%) at 20 and 30 N, and 13 (26%) at 40 and 50 N. CONCLUSION Cricoid pressure application with increasing force resulted in a worse glottic view, as examined with the Pentax-AWS Video laryngoscope. There is much individual difference in the degree of change, even with the same force. Clinicians should be aware that cricoid pressure affects laryngeal view with the Pentax-AWS and likely other video laryngoscopes.

The development of feedback monitoring device for CPR

CPR (Cardio-Pulmonary Resuscitation) is known as the most basic aid in emergency situations. For successful CPR, the chest compression depth, cycle, and compressing point are important factors. In I.C.U.s (Intensive Care Unit) and E.R.s (Emergency Room), monitoring devices are used to monitor the chest compressions correctly. These devices use accelerometers or pressure sensors. Because the mattress under the patient compresses together, these devices overestimate the compression depth. To overcome this problem, two accelerometers are used in this study, one is on the chest, and the other is between the back of the patient and the mattress. The measurement setup and algorithm to estimate the compression depth are explained. According to the experiment with the mannequin, when CPR is done on a mattress, the actual compression depth was 43.7mm (s.d. 1.93mm). The estimated compression depth was 61.4mm (s.d. 1.87mm) when using an acceleration sensor. This includes the depth of compression of the mattress. When we use two acceleration sensors, estimated compression depth is 44.6mm (s.d. 1.59mm), which is similar to the actual compression depth. In conclusion, the dual accelerometer gives more accurate estimated compression depth than conventional devices.

A Virtual Blind Cane Using a Line Laser-Based Vision System and an Inertial Measurement Unit

A virtual blind cane system for indoor application, including a camera, a line laser and an inertial measurement unit (IMU), is proposed in this paper. Working as a blind cane, the proposed system helps a blind person find the type of obstacle and the distance to it. The distance from the user to the obstacle is estimated by extracting the laser coordinate points on the obstacle, as well as tracking the system pointing angle. The paper provides a simple method to classify the obstacle’s type by analyzing the laser intersection histogram. Real experimental results are presented to show the validity and accuracy of the proposed system.

A novel method to decrease mattress compression during CPR using a mattress compression cover and a vacuum pump

BACKGROUND Mattress compression causes feedback devices to over-estimate the chest compression depth measurement during CPR. We propose a novel method to decrease the mattress compression using a vinyl cover. This mattress compression cover encloses the foam mattress and is compressed by a vacuum pump immediately prior to performing CPR. METHODS Nine CPR providers performed chest compressions on manikins placed on a conventional foam mattress on a bed frame (surface CONV), a backboard and foam mattress on a bed frame (surface BB), and a foam mattress, compressed with a vacuum pump, on a bed frame (surface VAC). Dual accelerometers were used to simultaneously measure the mattress compression and chest compression depths. RESULTS The mattress compression depth levels decreased from 14.9 mm (SD 1.4 mm) on surface CONV to 7.0 mm (SD 0.6 mm) on surface VAC (p<0.001) whereas 14.0 mm (SD 1.3 mm) on surface BB. The total compression depth was 65.4 mm (SD 3.8 mm) on surface CONV, and 58.3 mm (SD 3.0 mm) on surface VAC (p<0.001). CONCLUSION Using a mattress compression cover and a vacuum pump appears to increase the rigidity of the mattress and allow for efficient chest compressions. This novel method could decrease the mattress compression depth and increase the efficiency of chest compression during CPR in hospitals.

Smartwatches as chest compression feedback devices: A feasibility study

BACKGROUND Recently, there have been attempts to use smartphones and smartwatches as the feedback devices to improve the quality of chest compressions. In this study, we compared chest compression depth feedback accuracy between a smartphone and a smartwatch in a hands-only cardiopulmonary resuscitation scenario, using a manikin with a displacement sensor system. METHODS Ten basic life support providers participated in this study. Guided by the chest compression depths displayed on the monitor of a laptop, which received data from the manikin, each participant performed 2min of chest compressions for each target depth (35mm and 55mm) on a manikin while gripping a smartphone and wearing a smartwatch. Participants had a rest of 1h between the instances, and the first target depth was set at random. Each chest compression depth data value from the smartphone and smartwatch and a corresponding reference value from the manikin with the displacement system were recorded. To compare the accuracy between the smartphone and smartwatch, the errors, expressed as the absolute of the differences between the reference and each device, were calculated. RESULTS At both target depths, the error of the smartwatch were significantly smaller than that of the smartphone (the errors of the smartphone vs. smartwatch at 35mm: 3.4 (1.3) vs. 2.1 (0.8) mm; p=0.008; at 55mm: 5.3 (2.8) vs. 2.3 (0.9) mm; p=0.023). CONCLUSION The smartwatch-based chest compression depth feedback was more accurate than smartphone-based feedback.

Digital recording system of sphygmomanometry

ObjectivesValidation of blood pressure measurement devices is always difficult because the gold standard method depends on the observers manual assessment. To improve the assessment algorithm in automatic blood pressure measurement devices, knowing the reference blood pressure values and analyzing various data are always necessary. A digital system to record Korotkoff sound and cuff pressure is suggested. MethodsThe recording system consists of cuff, microphone, amplifier, and all the components of an oscillometric measurement device, which enable the collection of various data from patients. After collecting the data, the browsing software can playback the recorded sound and pressure variation on a computer. ResultsThe system records the Korotkoff sound faithfully. The sound can be played with sound card on a personal computer. Cuff pressure can also be displayed with Korotkoff sound at the same time. With this playback software, the observer can assess systolic blood pressure and diastolic blood pressure . The observer can listen again and discuss with others when the decision is not clear. ConclusionThe digital recording system of sphygmomanometry can be used for validation of blood pressure measurement devices, collecting of oscillometric data for research, and educating the students who learn blood pressure measurement.

Proper target depth of an accelerometer-based feedback device during CPR performed on a hospital bed: a randomized simulation study

PURPOSE Feedback devices are used to improve chest compression (CC) quality related to survival rates in cardiac arrest. However, several studies have shown that feedback devices are not sufficiently reliable to ensure adequate CC depth on soft surfaces. Here, we determined the proper target depth of feedback (TDF) using an accelerometer during cardiopulmonary resuscitation in hospital beds. METHODS In prospective randomized crossover study, 19 emergency physicians performed CCs for 2 minutes continuously on a manikin in 2 different beds with 3 TDFs (5, 6, and 7 cm). We measured CC depth, the proportion of accurate compression depths, CC rate, the proportion of incomplete chest decompressions, the velocity of CC (CC velocity), the proportion of time spent in CC relative to compression plus decompression (duty cycle), and the time spent in CC (CC time). RESULTS Mean (SD) CC depths at TDF 5, 6, and 7 were 45.42 (5.79), 52.68 (4.18), and 58.47 (2.48) on one bed and 46.26 (4.49), 53.58 (3.15), and 58.74 (2.10) mm on the other bed (all P<.001), respectively. The proportions of accurate compression depths and CC velocity at TDF 5, 6, and 7 differed significantly according to TDF on both beds (all P<.001).The CC rate, CC time, and proportion of incomplete chest decompression did not differ on both beds (all P>.05). The duty cycle differed significantly on only B2. CONCLUSIONS The target depth of the real-time feedback device should be at least 6 cm but should not exceed 7 cm for optimal CC on patients on hospital beds.

Does the accuracy of blood pressure measurement correlate with hearing loss of the observer

ObjectiveThe auscultatory method is influenced by the hearing level of the observers. If the observer has hearing loss, it is possible to measure blood pressure inaccurately by misreading the Korotkoff sounds at systolic blood pressure (SBP) and diastolic blood pressure (DBP). Because of the potential clinical problems this discrepancy may cause, we used a hearing loss simulator to determine how hearing level affects the accuracy of blood pressure measurements. Materials and methodsTwo data sets (data set A, 32 Korotkoff sound video clips recorded by the British Hypertension Society; data set B, 28 Korotkoff sound data acquired from the Korotkoff sound recording system developed by Hanyang University) were used and all the data were attenuated to simulate a hearing loss of 5, 10, 15, 20, and 25 dB using the hearing loss simulator. Five observers with normal hearing assessed the blood pressures from these data sets and the differences between the values measured from the original recordings (no attenuation) and the attenuated versions were analyzed. ResultsGreater attenuation of the Korotkoff sounds, or greater hearing loss, resulted in larger blood pressure measurement differences when compared with the original data. When measuring blood pressure with hearing loss, the SBP tended to be underestimated and the DBP was overestimated. The mean differences between the original data and the 25 dB hearing loss data for the two data sets combined were 1.55±2.71 and −4.32±4.21 mmHg for SBP and DBP, respectively. ConclusionThis experiment showed that the accuracy of blood pressure measurements using the auscultatory method is affected by observer hearing level. Therefore, to reduce possible error using the auscultatory method, observers’ hearing should be tested.