Plethysmographic Waveform Research Articles

Association between the Serum Soluble Urokinase Plasminogen Activator Receptor and Peripheral Arterial Stiffness According to the Cardio-Ankle Vascular Index in Patients Undergoing Kidney Transplantation.

High soluble urokinase plasminogen activator receptor (suPAR) levels are correlated with cardiovascular (CV) disease. Arterial stiffness is associated with aging-related vascular diseases and is an independent risk factor for CV morbidity and mortality. It can be measured by the cardio-ankle vascular index (CAVI). We evaluated the association between serum suPAR levels and arterial stiffness according to the CAVI in kidney transplantation (KT) recipients. In this study, 82 patients undergoing KT were enrolled. Serum suPAR levels were analyzed using an enzyme immunoassay. The CAVI was measured using a plethysmograph waveform device, and patients with a CAVI of 9.0 were assigned to the peripheral arterial stiffness (PAS) group. Twenty KT patients (24.4%) had PAS, were of older age (p = 0.042), and had higher serum triglyceride (p = 0.023) and suPAR levels (p 0.001) than the normal group. After adjusting for factors significantly associated with PAS by multivariate logistic regression analysis, serum suPAR levels (odds ratio [OR] 1.072, 95% confidence interval (CI) 1.023-1.123; p = 0.004) were independently associated with PAS in KT patients. The logarithmically transformed suPAR level (log-suPAR) was also positively correlated with the left or right CAVI values (all p 0.001) from the results of the Spearman correlation analysis in KT patients. Serum suPAR levels are positively associated with left or right CAVI values and are independently associated with PAS in KT patients.

Visual Evaluation of Plethysmographic Waveforms: Introducing the Simple Systolic Ratio as an Indicator of Fluid Responsiveness.

For patient safety, maintaining hemodynamic stability during surgical procedures is critical. Dynamic indices [such as systolic pressure variation (SPV) and pulse pressure variation (PPV)], have recently seen an increase in use. Given the risks associated with such invasive techniques, there is growing interest in non-invasive monitoring methods-and plethysmographic waveform analysis. However, many such non-invasive methods involve intricate calculations or brand-specific monitors. This study introduces the simple systolic ratio (SSR), derived from pulse oximetry tracings, as a non-invasive method to assess fluid responsiveness. This prospective observational study included 25 adult patients whose SPV, PPV, and SSR values were collected at 30-min intervals during open abdominal surgery. The SSR was defined as the ratio of the tallest waveform to the shortest waveform within pulse tracings. The correlations among SSR, SPV, and PPV were analyzed. Additionally, anaesthesia specialists visually assessed pulse oximetry tracings to determine fluid responsiveness using the SSR method. Strong correlations were observed between SSR and both SPV (r = 0.715, P < 0.001) and PPV (r = 0.702, P < 0.001). Receiver operator curve analysis identified optimal SSR thresholds for predicting fluid responsiveness at 1.47 for SPV and 1.50 for PPV. A survey of anaesthesia specialists using the SSR method to visually assess fluid responsiveness produced an accuracy rate of 83%. Based on the strong correlations it exhibits with traditional markers, SSR has great potential as a clinical tool, especially in resource-limited settings. However, further research is needed to establish its role, especially as it pertains to its universal applicability across monitoring devices.

Perfusion index as a predictor of hypotension following induction of general anaesthesia with propofol-An observational study

Background: Perfusion index (PI) is a somewhat novel parameter evaluating the pulsatility of blood in the extremities, calculated using the infrared spectrum as a component of plethysmography waveform processing. Aims and Objectives: To obtain a cutoff value of pre-anesthesia PI, which may be helpful for the prediction of hypotension following anesthetic induction with propofol. Materials and Methods: This descriptive observational research was carried out at the Sree Gokulam medical college and research foundation, Venjaramoodu, Trivandrum, Kerala, from June 2020 to June 2021. A total of 174 patients of age group 17–60 years, with ASA 1 or 2 scheduled for surgery under general anesthesia, were included. The parameters (systolic blood pressure [SBP], diastolic blood pressure, mean arterial pressure, PI, and SPO2) were recorded until 5 min of induction. Intravenous (IV) fentanyl 2 μg/kg was administered, propofol injected was given slowly at a rate of 10 mg per every 5 s, titrated to loss of verbal communication responseuronium 0.1 mg/kg IV was administered. The calculation for hypertension was done 5 min after anesthesia. The predictive validity of PI was calculated, keeping SBP as the standard gold test. For statistical analysis coGuide software. Results: The cutoff value for PI at 5 min was low (≤2.45) for 27 (90%) participants and high (&gt;2.45) for 3 (10%) participants. With a sensitivity of 90% in predicting hypotension and specificity of 87.50%, false-positive rate was 12.50%, false-negative rate was 10, positive predictive value was 60% (95 CI 44.43–74.30%), the negative predictive value (NPV) was 97.67%, and the total diagnostic accuracy was 87.93%. Conclusion: With the current study’s findings, we conclude that PI cutoff value 2.45 can be used to predict hypotension following anesthetic induction with propofol. It has a high NPV with fair diagnostic accuracy.

Noninvasive, Wearable Multi Biosensors for Continuous, Long-term Monitoring of Blood Pressure via Internet of Things Applications

Continuous blood pressure (BP) monitoring through various physical stress tests is important for the prediction of hypertension and cardiovascular mortality. This study proposes a multimodal wearable biosensor device for continuous BP monitoring through various tests during exercise and internet of things (IoT) applications. We evaluated three pulse transit time (PTT)-BP estimation models to identify the best mode for predicting BP response to exercise. Moreover, the proposed BP monitoring system was designed to connect to the cloud server for health data processing and management. The efficacy of the proposed device was validated by monitoring the natural variability of BP in various cycling tests. Thus, BP estimation based on the impedance plethysmography waveform and arterial impedance offers superiority compared to other conventional PTT estimation methods. These results suggest the feasibility of the multimodal biosensor device for continuous, long-term BP monitoring in remote diagnosis and management with IoT-based healthcare applications.

Manifestations of circulatory assist devices in noninvasive arterial duplex evaluation: A pictorial review.

Spectral Doppler and plethysmographic waveforms vary significantly in the presence of circulatory assist devices. Understanding the effect these devices have on the waveforms and flow characteristics is necessary for the appropriate interpretation of duplex ultrasound and other noninvasive vascular studies. We review the different arterial waveforms that can be seen with circulatory assist devices.

Abstract 9307: A Heart of Gold: A Case Report of Massive Pericardial Effusion Secondary to Cholesterol Pericarditis

A case of rare cholesterol pericarditis that developed over 12 years resulting in a massive pericardial effusion containing cholesterol crystals is described. A 41-year-old homeless man with history of polysubstance intravenous drug abuse and upper respiratory and soft-tissue infections presented with evidence of recurrent left lower extremity cellulitis, mild shortness of breath, and palpitations. Physical exam demonstrated soft-tissue infection, marked tachycardia and distant heart sounds on auscultation, and jugular venous distention. Unexpectedly, pulse-oximetry plethysmographic waveforms revealed pronounced respirophasic variability and pulsus paradoxus of 14 mmHg. Electrocardiogram demonstrated low voltage and electrical alternans. A transthoracic echocardiogram revealed a large pericardial effusion and findings consistent with tamponade physiology, such as elevated respiratory variation in mitral inflow velocity. Emergent pericardiocentesis yielded 3.6 L of fluid characterized by glittering, gold paint-like appearance and a cell count predominated by macrophages, leading to a provisional diagnosis of cholesterol pericarditis. This was confirmed by polarized light microscopy demonstrating cholesterol crystals. Retrospective review of prior emergency department visits revealed a 12-year development of the effusion, beginning with symptoms, imaging, and labs consistent with a presumably instigating viral respiratory illness. Over time, progressive enlargement and evidence of chronic pericarditis were demonstrated by chest x-ray and electrocardiography, while the effusion remained undiagnosed. Following improvement in his symptoms after pericardiocentesis, the patient deferred pericardial window and definitive surgical management with pericardiectomy. Given his high risk for recurrent cardiac tamponade, he was given clear return precautions and is now followed on an outpatient basis. The diverse etiologies of cholesterol pericarditis, such as hypothyroidism, tuberculosis, and rheumatoid arthritis, that guided the workup for this patient, and the pathophysiology of this disease and its treatment options, are reviewed.

Safe sleep after 1 year of age.

Safe sleep after 1 year of age.

Elevated Heart Rate and Pain During a Cold Pressor Test Correlates to Pain Catastrophizing.

To understand the variable response to pain, researchers have examined the change in cardiovascular measures to a uniform painful stimulation. Pain catastrophizing is the tendency to magnify or exaggerate pain sensations, and it affects the outcome of rehabilitation in a clinical setting. Its effect on cardiovascular changes during a painful stimulus is unclear. Twenty-four healthy human participants completed the study. All participants completed a cold pressor test while subjective pain intensity was measured with a numeric pain scale from 0-10. Continuous cardiac output measurements were obtained with finger-pulse plethysmograph waveform analysis. The measurements included systolic and diastolic blood pressure, heart rate averaged over 30s intervals. Pain catastrophizing and anxiety were assessed using the pain catastrophizing scale (PCS), and Spielberger's State-Trait Anxiety Inventories, respectively. Peak pain was correlated to pain catastrophizing (r = 0.628, p < 0.01). There was a strong correlation between change in heart rate (HR) and subjective peak pain (r = 0.805, p < 0.01), total PCS (r = 0.474, p < 0.05), and the helplessness subscale of the PCS (r = 0.457, p < 0.05). Peak pain and catastrophizing explained a significant amount of the variance for the change in HR during the cold pressor test (R2 of 0.649 and 0.224 respectively, p = 0.019). These novel findings demonstrate a psycho-physiological relationship between cardiovascular changes and pain catastrophizing. Further research should include participants with subacute or persistent pain.

Predicting hypotension during anesthesia: Variation in pulse oximetry plethysmography predicts propofol‐induced hypotension in children

The development of hypotension on administration of intravenous propofol is common and independently associated with adverse outcomes. Identifying patients with a high risk for anesthesia-induced hypotension may help anesthesiologists prepare for such an event. The authors hypothesized that propofol-induced hypotension is predictable by variables related to fluid responsiveness and investigated such variables to determine the factors which can predict hypotensive events. Patients 3-6years of age who underwent general were included. Intravenous midazolam 0.1mg kg-1 was administered as premedication, and preoperative noninvasive blood pressure, heart rate, perfusion index, pleth variability index, and respiratory variation of pulse oximetry plethysmographic waveform were measured. Intravenous propofol 2.5mg kg-1 was given, and blood pressure was measured 5 times at 1-min intervals. Subjects with significant hypotension (mean blood pressure decrease ≥20%) were allocated to the hypotensive group; those without significant hypotension were allocated to the relatively normotensive group. Of 77 patients, 50 (64.9%) developed significant hypotension. Patients in the hypotensive group exhibited significantly higher respiratory variation of pulse oximetry plethysmographic waveform (mean difference 11 [3.3] [95% confidence interval 4.9-18.1]; p=.001) and higher pleth variability index (mean difference 7.1 [2.8] [95% confidence interval 1.6-12.6]; p=.013) than the normotensive group. The areas under the receiver operating characteristic curve for respiratory variation of pulse oximetry plethysmographic waveform and pleth variability index were 0.722 and 0.649, respectively. High preoperative respiratory variation of pulse oximetry plethysmographic waveform and pleth variability index were both independently associated with propofol-induced hypotension in children.

Pulse oximeter plethysmograph waveform and automated oscillometric sphygmomanometer for ankle-brachial index measurement.

There are limited non-invasive methods to assess lower extremity arterial injuries in the emergency department (ED) and pre-hospital setting. The ankle-brachial index (ABI) requires careful auscultation by Doppler, an approach made difficult in noisy environments. We sought to determine the agreement of the ABI measured using the pulse oximeter plethysmograph waveform (Pleth) with auscultation by Doppler in a controlled setting. A secondary outcome sought to examine the agreement of ABI by automated oscillometric sphygmomanometer (AOS) with Doppler. We measured blood pressure in the right upper and lower extremities of healthy volunteers using: (1) Doppler and manual sphygmomanometer; (2) Pleth and manual sphygmomanometer; and (3) AOS. The Bland-Altman approach to assessing agreement between methods was used comparing mean differences between ABI pairs to their means for Doppler versus Pleth and Doppler versus AOS. The intraclass correlation coefficient (ICC) from mixed effects models examined intra- and inter-rater reliability. Among 100 participants with normal ABI the mean ABI (95%CI) were Doppler 1.11 (0.90-1.33), Pleth 1.10 (0.91-1.30), and AOS 1.10 (0.90-1.30). The ABI difference (95% CI for limits of agreement) were 0.01 (-0.20,0.18) for Doppler-Pleth and 0.02 (-0.26, 0.22) for Doppler-AOS. The ICC for the Doppler-Pleth comparison (ICC=0.56, 95% CI 0.47-0.63) was greater than for the Doppler-AOS (ICC=0.32, 95% CI 0.19-0.43). The ABI measured using the Pleth has a high level of agreement with measurement by Doppler. The AOS and Doppler have good agreement with greater measurement variability. Pleth and AOS may be reasonable alternatives to Doppler for ABI.

Pulse Oximeter Plethysmograph Variation During Hemorrhage in Beta-Blocker–Treated Swine

BackgroundBeta-blockers blunt the stress response to hemorrhage. Our aim was to investigate the feasibility of noninvasive pulse oximeter plethysmographic waveform variation (PoPV) for predicting blood volume loss in an esmolol-treated swine hemorrhagic shock model. Materials and MethodsControlled hemorrhage was induced in eight male domestic pigs. In four pigs, a total of 15% and 30% blood volume was drawn step-by-step over 10 min in each step (controlled hemorrhage–only pigs). In the other four pigs, the heart rate (HR) was reduced and maintained by 30% from baseline by esmolol infusion before controlled hemorrhage (esmolol-treated pigs). Diagnostic abilities of HR, pulse pressure variation (PPV), PoPV, and mean arterial pressure for 15% and 30% blood volume loss were determined by the area under the receiver operating characteristic curve (AUC). ResultsPoPV was well correlated with PPV in controlled hemorrhage–only pigs (r = 0.717) and esmolol-treated pigs (r = 0.532). In controlled hemorrhage-only pigs, HR (AUC = 0.841 and 0.864), PPV (0.878 and 0.843), and PoPV (0.779 and 0.793) accurately predicted 15% and 30% of blood volume loss. In esmolol-treated pigs, the diagnostic ability of HR was decreased (AUC = 0.766 and 0.733). However, diagnostic abilities of PPV (0.848 and 0.804) and PoPV (0.808 and 0.842) were not deteriorated. ConclusionsThe diagnostic ability of HR for blood volume loss was blunted by esmolol. However, those of PPV and PoPV were not altered. PoPV may be considered to be a useful noninvasive tool to predict blood volume loss in injured patients taking beta-blockers.

Pulse rate as an alternative, real-time feedback indicator for chest compression rate: a porcine model of cardiac arrest.

Feedback indicators can improve chest compression quality during cardiopulmonary resuscitation (CPR). However, the application of feedback indicators in the clinic practice is rare. Pulse oximetry has been widely used and reported to correlate spontaneous circulation restoration during CPR. However, it is unclear if pulse oximetry can monitor the quality of chest compression. We hypothesized that pulse rate monitored by pulse oximetry can be used as a feedback indicator of the chest compression rate during CPR in a porcine model of cardiac arrest. Seven domestic male pigs (30–35 kg) were utilized in this study. Eighteen intermittent chest compression periods of 2 min were performed on each animal. Chest compression and pulse oximetry plethysmographic waveforms were recorded simultaneously. Chest compression and pulse rates were calculated based on both waveforms. Compression interruption and synchronous pulse interruption times were also measured. Agreement was analyzed between pulse rates and synchronous chest compression rates, as well as between compression interruption times and synchronous pulse interruption times. A total of 126 compression periods of 2 min were performed on seven animals. Interclass correlation coefficients and Bland–Altman analysis revealed reliable agreement between pulse rates and synchronous chest compression rates. Similarly, compression interruption and synchronous pulse interruption times obtained also showed high agreement. Pulse rate can be used as an alternative indicator of chest compression rate during CPR in a porcine model of cardiac arrest. Pulse interruption time also can be used to reflect compression interruption time precisely in this model.

Using Dynamic Variables to Guide Perioperative Fluid Management.

Dynamic variables that quantify the variations in the arterial pressure and plethysmographic waveforms during mechanical ventilation reflect fluid responsiveness. These variables may be helpful in identifying occult hypovolemia and in preventing unnecessary fluid administration.

100EMF Ankle-Brachial Index Measured Using Pulse Oximeter Plethysmograph Waveform and Automated Blood Pressure Device to Assess Lower Extremity Vascular Integrity

There is no practical, readily available and accurate method to assess lower extremity vascular injuries in the emergency department (ED). The ankle-brachial index (ABI) assesses the integrity of the lower-extremity arterial vasculature and the need for emergent vascular imaging. However, ABI measurement requires careful auscultation by Doppler. This measurement is made more difficult by the noisy environment of the ED or during ambulance or helicopter transport. A critical knowledge gap is whether alternative methods of ABI measurement using the pulse oximeter plethysmograph waveform or automated oscillometric sphygmomanometer (Dynamap®) can be substituted for auscultation with Doppler interrogation of the pulse. We sought to test the hypothesis that the ABI measured using the pulse oximeter plethysmograph waveform and Dynamap® have high levels of agreement with measurement by Doppler, the criterion standard for this measurement. We also tested the hypothesis that each measurement technique has high intra-rater reliability. We conducted a cross-sectional study using a convenience sample of healthy adults age 18 or older. We measured systolic blood pressures in each participant’s right arm and right leg and calculated the ABI using three different methods: (1) Doppler and manual sphygmomanometer; (2) Pulse oximeter plethysmograph waveform (“plethysmograph”) and manual sphygmomanometer; and (3) Automated oscillometric sphygmomanometer (Dynamap®). We repeated each method three times and calculated the mean ABI obtained using each method. We used Bland-Altman plots to visually examine agreement of ABI measured using the Doppler and (1) the plethysmograph waveform and (2) the Dynamap®. We measured intraclass correlation coefficients (ICCs) for intra-rater reliability of the three measurements for each method using a two-way mixed effects model for absolute agreement. Among 58 participants enrolled to date, median age was 26 [24, 28] years, 24 (41.4%) were male, 4 (6.9%) Black, 46 (79.3%) White, and 5 (8.6%) Asian race, median BMI 24.08 [21.94, 38.36], and 0 smokers. Mean absolute difference between ABI measured using plethysmograph and Doppler was 0.01 [95% CI -0.12, +0.14] with limits of agreement -0.11 to 0.14. Mean absolute difference between ABI measured by Dynamap® and Doppler was 0.03 (95% CI -0.17, +0.23) with limits of agreement -0.16 to 0.22. The ICCs for intra-rater reliability were as follows: Doppler, 0.64 (95% CI 0.51, 0.76); plethysmograph, 0.67 (95% CI 0.54, 0.77); and Dynamap® 0.45 (95% CI 0.29, 0.60). ABI measured using the pulse oximeter plethysmograph waveform has a high level of agreement with measurement by Doppler. The Dynamap® and Doppler have good agreement but wider limits of agreement than plethysmograph measurement. The Doppler and plethysmograph measurements have good intra-rater reliability. ABI measured using the pulse oximeter plethysmograph waveform may be a valuable adjunct for assessing lower-extremity vascular integrity in noisy clinical environments.

The effect of different ventilation modes on the ventilation rate and prognosis in patients with cardiac arrest after advanced airway placement

Objective To investigate the effect of different ventilation modes on the ventilation rate and prognosis in patients with cardiac arrest after advanced airway placement. Methods Based on the national database of emergency cardiac arrest treatment, patients treated with advanced airway placement during cardiopulmonary resuscitation (CPR) were enrolled in PUMCH Emergency Department from December 2013 to June 2018. The physiological parameters, such as electrocardiograph waveform, pulse oximetry plethysmographic waveform and capnography, were recorded at least 18 minutes. The demographic data and resuscitation parameters were collected. Waveform capnography was used for calculating ventilation rate (VR) and the VR between 8 to 12 breaths/min was defined as the qualified ventilation rate (QVR). According to the ventilation modes, patients were divided into the bag-mask group (BMG) and mechanical ventilation group (MVG). According to the VR, patients in the mechanical ventilation group were divided into two subgroups, the high-frequency ventilation subgroup (HFV subgroup) with the VR more than 20 breaths/min and the low-frequency VR subgroup (LFV subgroup) with the VR less than 20 breaths/min. VR, the qualified ventilation rate ratio (QVRR), the return of spontaneous circulation (ROSC), and 24-h and 7-day survival were compared between the two groups and subgroups. Result A total of 90 patients were enrolled in the analysis with 22 patients in the bag-mask group and 68 patients in the mechanical ventilation group. The total rate of ROSC was 35.6%, 24-h survival was 1.1% and 7-day survival was 0. The first 18 minutes ventilation data were collected and added up to 1 620 min. The median VR was 16.5 (12.0, 26.0) breaths/min and the QVRR was 30%. Compared with the mechanical ventilation group, the VR in the bag-mask group were lower (10 breaths/min vs 21 breaths/min) and the QVRR was higher (88.9% vs 11.5%). The ROSC, 24-h survival and 7-day survival had no statistical differences between the two groups. In the mechanical ventilation group, the ratio of VR more than 20 breaths/min was 52.6%. Between the two subgroups, there was no statistical difference in ROSC, 24-h survival and 7-day survival. Conclusions Compared with the mechanical ventilation during CPR, the VR is lower with bag-mask ventilation, and the QVRR is higher. But there was no statistical difference on the outcomes. There was no difference on the outcomes between the two mechanical ventilation subgroups. Key words: Cardiac arrest; Cardiopulmonary resuscitation; Mechanical ventilation; Ventilation rate; Bag-mask ventilation

The effects of gel-based manicure on pulse oximetry.

Pulse oximetry is the standard monitoring technique of functional oxygen saturation (SpO2). As the use of fingernail polish has been described to alter SpO2 readings, its removal is commonly recommended prior to measurement. Gel-based manicures have gained popularity in recent years due to their attractiveness and longevity. However, the removal of gel nail polish requires a specialised procedure. Valuable time and resources can be saved if removal can be avoided. To our knowledge, there are no available studies on the effect of gel-based manicures on pulse oximetry readings. Hence, we evaluated the effect with two oximeters, using different technology and wavelength combinations. 17 healthy female adult volunteers were recruited for this single-blind randomised controlled trial. Subjects with hypothermia, hypotension, poor plethysmographic waveform and nail pathology were excluded. Colours tested were: black, purple, navy blue, green, light blue, white, yellow, orange, pink and red. Pulse oximetry was measured at 15- and 30-second intervals using two different pulse oximeters, the Philips M1191BL and Masimo SET®. Means were compared using paired t-tests. Using the Masimo oximeter, light blue (ΔM = 0.97% ± 0.96%; p = 0.001) and orange (ΔM = 0.76 ± 1.17%; p = 0.016) gel nail polish resulted in a statistically significant increase from baseline SpO2 readings. With the Philips oximeter, the limits of agreement ranged from 2% for pink to 17% for black, indicating imprecision. Gel-based manicures can result in overestimations of actual readings, delaying detection of hypoxaemia. Gel nail polish should be routinely removed or an alternative monitoring technique sought.

The value of cardiopulmonary resuscitation quality index in evaluating the prognosis during cardiopulmonary resuscitation

Objective To explore the timeliness value of cardiopulmonary resuscitation quality index (CQI) in patients’ prognostic evaluation during cardiopulmonary resuscitation (CPR). Methods A prospective descriptive study was conducted. According to whether they got return of spontaneously circulation (ROSC) or not, 45 patients receiving CPR were divided into the ROSC group and non-ROSC group. The changes of CQI and partial pressure of end-tidal carbon dioxide (PETCO2) during CPR were collected, and were analyzed to valuate the prognosis of patients. Results The initial, end, and average PETCO2 were statistically different between the ROSC group and the non-ROSC group [7.0(3.6, 14.6) vs 7.0(3.6, 14.6) mmHg; 29.5(19.8, 35.9) vs 4.0(2.3, 10.2)mmHg; and 22.2(11.8, 36.3) vs 4.0(2.5, 9.0) mmHg, respectively; P<0.05], and the end CQI was statistically different between the two groups (59.6±8.9 vs 34.8±5.2, P<0.05). The CQI differences between the two groups initiated at 11 min after CPR, and stopped at 29 min after CPR. The optimal cut-off point of terminal CQI and PETCO2 for prognostic was 33.2 and 16.1 mmHg respectively, and there was a statistically difference in the area under the curve between them (P<0.05). Conclusions During CPR, both CQI and PETCO2 can be used to evaluate the prognosis, and CQI is more capable of predicting in the late stage of CPR Key words: Cardiac arrest; Cardiopulmonary resuscitation; High-quality chest compressions; Pulse oximetry plethysmographic waveform; Cardiopulmonary resuscitation quality index; Partial pressure of end-tidal carbon dioxide; Prognosis; Return of spontaneously circulation

Identification of return of spontaneous circulation during cardiopulmonary resuscitation via pulse oximetry in a porcine animal cardiac arrest model.

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 ± 2kg) 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.

Usefulness of Oximetry Paradoxus to Diagnose Cardiac Tamponade

Although echocardiography is usually diagnostic of cardiac tamponade, it may not be readily available at the point-of-care. We sought to develop and validate a measurement of respirophasic variation in the amplitude of pulse oximetry plethysmographic waveforms as a diagnostic tool for cardiac tamponade. Pulse oximetry plethysmographic waveforms were recorded, and the ratio of maximum-to-minimum measured amplitude of these waveforms from one respiratory cycle was calculated by blinded observers. Ratios from 3 consecutive respiratory cycles were then averaged to derive an "oximetry paradoxus" ratio. Cardiac tamponade was independently confirmed or excluded according to a "blinded" objective interpretation of echocardiography or right heart catheterization. Seventy four subjects were enrolled (51% men; mean age 54 ± 15 years); 19 of whom had cardiac tamponade. Oximetry paradoxus area under the curve for diagnosis of cardiac tamponade was 0.90 (95% confidence interval, 0.84 to 0.97); its diagnostic performance was superior to sphygmomanometer-measured pulsus paradoxus (area under the curve difference = 0.16, p = 0.022). In a derivation cohort (n = 37; tamponade, 9 cases), 3 diagnostic oximetry paradoxus thresholds were identified and validated in an independent validation cohort (n = 37; tamponade, 10 cases): 1.2 (100% sensitivity, 44% specificity), 1.5 (80% sensitivity, 81% specificity), and 1.7 (80% sensitivity, 89% specificity). Furthermore, oximetry paradoxus was significantly reduced after draining pericardial fluid. In conclusion, we defined and validated oximetry paradoxus as a simple and ubiquitous point-of-care test to diagnose cardiac tamponade using respirophasic changes in pulse plethysmography waveforms. This test can aid in identifying patients with cardiac tamponade, thus expediting confirmatory testing and life-saving treatment.

Wearable speckle plethysmography (SPG) for characterizing microvascular flow and resistance.

In this work we introduce a modified form of laser speckle imaging (LSI) referred to as affixed transmission speckle analysis (ATSA) that uses a single coherent light source to probe two physiological signals: one related to pulsatile vascular expansion (classically known as the photoplethysmographic (PPG) waveform) and one related to pulsatile vascular blood flow (named here the speckle plethysmographic (SPG) waveform). The PPG signal is determined by recording intensity fluctuations, and the SPG signal is determined via the LSI dynamic light scattering technique. These two co-registered signals are obtained by transilluminating a single digit (e.g. finger) which produces quasi-periodic waveforms derived from the cardiac cycle. Because PPG and SPG waveforms probe vascular expansion and flow, respectively, in cm-thick tissue, these complementary phenomena are offset in time and have rich dynamic features. We characterize the timing offset and harmonic content of the waveforms in 16 human subjects and demonstrate physiologic relevance for assessing microvascular flow and resistance.