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BACKGROUND: Lower body negative Pressure (LBNP)-induced hypovolemia is simulating acute hemorrhage by sequestrating blood into lower extremities. Bioelectrical Impedance Analysis (BIA) is based on the electrical properties of biological tissues, as electrical current flows along highly conductive body tissues (such as blood). Changes in blood volume will lead to changes in bioimpedance. This study aims to study changes in upper (UL) and lower (LL) extremities bioimpedance during LBNP-induced hypovolemia. METHODS: This was a prospective observational study of healthy volunteers who underwent gradual LBNP protocol which consisted of 3-minute intervals: at baseline, -15, -30, -45, -60 mmHg, then recovery phases at -30 mmHg and baseline. The UL&LL extremities bioimpedance were measured and recorded at each phase of LBNP and the percentage changes of bioimpedance from baseline were calculated and compared using student's t-test. A P-value of < 0.05 was considered significant. Correlation between relative changes in UL&LL bioimpedance and estimated blood loss (EBL) from LBNP was calculated using Pearson correlation. RESULTS: 26 healthy volunteers were enrolled. As LBNP-induced hypovolemia progressed, there were a significant increase in UL bioimpedance and a significant decrease in LL bioimpedance. During recovery phases (where blood was shifted from the legs to the body), there were a significant increase in LL bioimpedance and a reduction in UL bioimpedance. There were significant correlations between estimated blood loss from LBNP model with UL (R = 0.97) and LL bioimpedance (R = - 0.97). CONCLUSION: During LBNP-induced hypovolemia, there were reciprocal changes in UL&LL bioimpedance. These changes reflected hemodynamic compensatory mechanisms to hypovolemia.
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Hipovolemia , Presión Negativa de la Región Corporal Inferior , Humanos , Impedancia Eléctrica , Volumen Sanguíneo , Hemodinámica , Presión SanguíneaRESUMEN
Develop a signal quality index (SQI) for the widely available peripheral venous pressure waveform (PVP). We focus on the quality of the cardiac component in PVP. We model PVP by the adaptive non-harmonic model. When the cardiac component in PVP is stronger, the PVP is defined to have a higher quality. This signal quality is quantified by applying the synchrosqueezing transform to decompose the cardiac component out of PVP, and the SQI is defined as a value between 0 and 1. A database collected during the lower body negative pressure experiment is utilized to validate the developed SQI. All signals are labeled into categories of low and high qualities by experts. A support vector machine (SVM) learning model is trained for practical purpose. The developed signal quality index coincide with human experts' labels with the area under the curve 0.95. In a leave-one-subject-out cross validation (LOSOCV), the SQI achieves accuracy 0.89 and F1 0.88, which is consistently higher than other commonly used signal qualities, including entropy, power and mean venous pressure. The trained SVM model trained with SQI, entropy, power and mean venous pressure could achieve an accuracy 0.92 and F1 0.91 under LOSOCV. An exterior validation of SQI achieves accuracy 0.87 and F1 0.92; an exterior validation of the SVM model achieves accuracy 0.95 and F1 0.96. The developed SQI has a convincing potential to help identify high quality PVP segments for further hemodynamic study. This is the first work aiming to quantify the signal quality of the widely applied PVP waveform.
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Corazón , Venas , Humanos , Presión Venosa , Bases de Datos Factuales , EntropíaRESUMEN
The photoplethysmographic (PPG) waveform contains hemodynamic information in its oscillations. We provide a new method for quantitative study of the waveform morphology and its relationship to the hemodynamics. A data adaptive modeling of the waveform shape is used to describe the PPG waveforms recorded from ear and finger. Several indices, based on the phase and amplitude information of different harmonics, are proposed to describe the PPG morphology. The proposed approach is illustrated by analyzing PPG waveforms recorded during a lower body negative pressure (LBNP) experiment. Different phase and amplitude dynamics are observed during the LBNP experiment. Specifically, we observe that the phase difference between the high order harmonics and fundamental components change more significantly when the PPG signal is recorded from the ear than the finger at the beginning of the study. In contrast, the finger PPG amplitude changes more when compared to the ear PPG during the recovery period. A more complete harmonic analysis of the PPG appears to provide new hemodynamic information when used during a LBNP experiment. We encourage other investigators who possess modulated clinical waveform data (e.g. PPG, arterial pressure, respiratory, and autonomic) to re-examine their data, using phase information and higher harmonics as a potential source of new insights into underlying physiologic mechanisms.
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Presión Negativa de la Región Corporal Inferior , Fotopletismografía , Humanos , Fotopletismografía/métodos , Presión Arterial , Hemodinámica , DedosRESUMEN
Rotational Thromboelastometry (ROTEM) Delta has been described in several postpartum hemorrhage algorithms, but this device requires pipetting and careful mixing of reagents to initiate the clotting reaction. In contrast, thromboelastography (TEG 6s) and the Quantra devices operate utilizing an automated pre-mixed cartridge that only requires a blood sample to start the clot strength analysis. We compared the correlation between 3 point of care viscoelastic testing (POCVT) devices to laboratory Clauss fibrinogen and platelets, their inter-device correlation, and the total running time difference between Quantra and ROTEM. A high correlation was noted between the Clauss fibrinogen and the fibrinogen parameters from ROTEM (r = 0.76-0.84, P < 0.0001), TEG6s (r = 0.71, P < 0.0001) and Quantra (r = 0.72, P = 0.0001). A moderate correlation between laboratory platelets and the ROTEM (r = 0.54;0.45, P < 0.0001; P = 0.0013) and Quantra (r = 0.66, P = 0.0001) parameters was noted. The inter-device correlation showed to be high when comparing the fibrinogen parameters of TEG6s and Quantra to that of ROTEM (r = 0.88 and 0.74, P < 0.0001, respectively). In contrast, a moderate correlation was noted between the platelet parameters of Quantra and ROTEM (r = 0.51, p = 0.0036). The Quantra device resulted 20.9 min (95% CI -0.2 to 4.7, P = 0.07) faster than the ROTEM if the warming and pipetting of reagents of the latter were considered. All the POCVT devices demonstrated a high correlation to laboratory Clauss fibrinogen, making each beneficial for the early recognition and management of hypofibrinogenemia.
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Coagulación Sanguínea , Tromboelastografía , Embarazo , Femenino , Humanos , Tromboelastografía/métodos , Tercer Trimestre del Embarazo , Estudios Prospectivos , FibrinógenoRESUMEN
We introduce a recently developed nonlinear-type time-frequency analysis tool, synchrosqueezing transform (SST), to quantify complicated and noisy physiological waveform that has time-varying amplitude and frequency. We apply it to analyze a peripheral venous pressure (PVP) signal recorded during a seven hours aortic valve replacement procedure. In addition to showing the captured dynamics, we also quantify how accurately we can estimate the instantaneous heart rate from the PVP signal.
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Frecuencia Cardíaca , Humanos , Presión VenosaRESUMEN
BACKGROUND: Scoliosis surgery is often associated with substantial blood loss, requiring fluid resuscitation and blood transfusions. In adults, dynamic preload indices have been shown to be more reliable for guiding fluid resuscitation, but these indices have not been useful in children undergoing surgery. The aim of this study was to introduce frequency-analyzed photoplethysmogram (PPG) and arterial pressure waveform variables and to study the ability of these parameters to detect early bleeding in children during surgery. METHODS: We studied 20 children undergoing spinal fusion. Electrocardiogram, arterial pressure, finger pulse oximetry (finger PPG), and airway pressure waveforms were analyzed using time domain and frequency domain methods of analysis. Frequency domain analysis consisted of calculating the amplitude density of PPG and arterial pressure waveforms at the respiratory and cardiac frequencies using Fourier analysis. This generated 2 measurements: The first is related to slow mean arterial pressure modulation induced by ventilation (also known as DC modulation when referring to the PPG), and the second corresponds to pulse pressure modulation (AC modulation or changes in the amplitude of pulse oximeter plethysmograph when referring to the PPG). Both PPG and arterial pressure measurements were divided by their respective cardiac pulse amplitude to generate DC% and AC% (normalized values). Standard hemodynamic data were also recorded. Data at baseline and after bleeding (estimated blood loss about 9% of blood volume) were presented as median and interquartile range and compared using Wilcoxon signed-rank tests; a Bonferroni-corrected P value <0.05 was considered statistically significant. RESULTS: There were significant increases in PPG DC% (median [interquartile range] = 359% [210 to 541], P = 0.002), PPG AC% (160% [87 to 251], P = 0.003), and arterial DC% (44% [19 to 84], P = 0.012) modulations, respectively, whereas arterial AC% modulations showed nonsignificant increase (41% [1 to 85], P = 0.12). The change in PPG DC% was significantly higher than that in PPG AC%, arterial DC%, arterial AC%, and systolic blood pressure with P values of 0.008, 0.002, 0.003, and 0.002, respectively. Only systolic blood pressure showed significant changes (11% [4 to 21], P = 0.003) between bleeding phase and baseline. CONCLUSIONS: Finger PPG and arterial waveform parameters (using frequency analysis) can track changes in blood volume during the bleeding phase, suggesting the potential for a noninvasive monitor for tracking changes in blood volume in pediatric patients. PPG waveform baseline modulation (PPG DC%) was more sensitive to changes in venous blood volume when compared with respiration-induced modulation seen in the arterial pressure waveform.
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Volumen Sanguíneo , Monitoreo Intraoperatorio/métodos , Oximetría , Oxígeno/sangre , Fotopletismografía , Respiración Artificial , Escoliosis/cirugía , Fusión Vertebral , Adolescente , Factores de Edad , Presión Arterial , Biomarcadores/sangre , Pérdida de Sangre Quirúrgica/prevención & control , Femenino , Análisis de Fourier , Humanos , Hipovolemia/etiología , Hipovolemia/fisiopatología , Hipovolemia/prevención & control , Masculino , Valor Predictivo de las Pruebas , Escoliosis/diagnóstico , Fusión Vertebral/efectos adversos , Factores de TiempoRESUMEN
During shoulder surgery, patients typically are placed in the beach chair position. In rare cases, this positioning has resulted in devastating outcomes of postoperative cerebral ischemia (Cullen and Kirby in APSF Newsl 22(2):25-27, 2007; Munis in APSF Newsl 22(4):82-83, 2008). This study presents a method to noninvasively and continuously hemodynamically monitor patients during beach chair positioning by using the photoplethysmograph signal recorded from a commercial pulse oximeter. Twenty-nine adults undergoing shoulder surgery were monitored before and after beach chair positioning with electrocardiogram, intermittent blood pressure, end tidal carbon dioxide, and photoplethysmograph via Nellcor finger pulse oximeter. Fast Fourier transform (FFT) was used to perform frequency-domain analysis on the photoplethysmograph (PPG) signal for data segments taken 80-120 s before and after beach chair positioning. The amplitude density of respiration-associated PPG oscillations was quantified measuring the height of the FFT peak at respiratory frequency. Results were reported as (median, interquartile range) and statistical analysis was performed using Wilcoxon sign rank test. Data were also collected when vasoactive drugs phenylephrine and ephedrine were used to maintain acceptable mean arterial pressure during a case. With beach chair positioning, all subjects who did not receive vasoactive drugs showed an increase in the FFT amplitude density of respiration-associated PPG oscillations (p < 0.0001) without change in pulse-associated PPG oscillations. The PPG was more accurate at monitoring the change to beach chair position than blood pressure or heart rate. With vasoactive drugs, pulse-associated PPG oscillations decreased only with phenylephrine while respiration-associated oscillations did not change. Frequency domain analysis of the PPG signal may be a better tool than traditional noninvasive hemodynamic parameters at monitoring patients during beach chair position surgery.
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Anestésicos Generales/administración & dosificación , Presión Sanguínea/fisiología , Frecuencia Cardíaca/fisiología , Posicionamiento del Paciente/métodos , Fotopletismografía/efectos de los fármacos , Fotopletismografía/métodos , Postura/fisiología , Anestesia General/métodos , Presión Sanguínea/efectos de los fármacos , Monitoreo de Drogas/métodos , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Photoplethysmography (PPG) is a non-invasive optical technique that measures changes in blood volume in the microvascular tissue bed of the body. While it shows potential as a clinical tool for blood pressure (BP) assessment and hypertension management, several sources of error can affect its performance. One such source is the PPG-based algorithm, which can lead to measurement bias and inaccuracy. Here, we review seven widely used measures to assess PPG-based algorithm performance and recommend implementing standardized error evaluation steps in their development. This standardization can reduce bias and improve the reliability and accuracy of PPG-based BP estimation, leading to better health outcomes for patients managing hypertension.
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OBJECTIVES: This prospective single-arm study investigated both laryngeal physiology and voice acoustic measures in patients undergoing minimally invasive parathyroidectomy (MIP) due to primary hyperparathyroidism (primary HPTH). BACKGROUND: Avoidance of recurrent or superior laryngeal nerve injury and maintenance of normal laryngeal physiology and vocal function are key goals in the treatment of primary HPTH. No data are available comparing pre- and postoperative MIP laryngeal physiology and voice acoustics. METHODS: Patients served as their own controls and underwent identical pre- and postoperative assessment. True vocal fold mobility was assessed and recorded using transnasal fiber-optic laryngoscopy. Vocal capacity was recorded with maximum phonation time and vocal stability by frequency-based voice measures, that is, mean fundamental frequency (F0), standard deviation of the fundamental frequency (F0SD), and jitter and shimmer as measured by relative average perturbation and mean shimmer in decibels, respectively. RESULTS: A total of 104 patients were enrolled [26 men, mean age = 53 years, range 29-79 years; 78 women, mean age = 56 years, range 16-83 years). All completed the protocol and were analyzed according to intent to treat. MIP was accomplished in 95 patients, and 9 were converted to general anesthesia. The cure rate was 100%, as evidenced by normalization of serum calcium levels. Both real-time agreement and blinded inter- and intrarater reliability testing for laryngeal physiology ratings were 100%. One patient (<1%) exhibited a recurrent laryngeal nerve injury. No significant differences (P > 0.05) were found for any voice acoustic parameter between pre- and postoperative MIP (ie, maximum phonation time, F0, F0SD, relative average perturbation, or shimmer in decibels). CONCLUSIONS: MIP can be performed with exquisite disease control and without significant effects on laryngeal physiology or voice acoustic measures. For the first time, both physiologic and acoustic data support the use of MIP.
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Hiperparatiroidismo Primario/cirugía , Procedimientos Quirúrgicos Mínimamente Invasivos , Paratiroidectomía , Pliegues Vocales/fisiología , Calidad de la Voz/fisiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Análisis de Intención de Tratar , Laringoscopía , Masculino , Persona de Mediana Edad , Fonación/fisiología , Estudios Prospectivos , Método Simple Ciego , Resultado del Tratamiento , Adulto JovenRESUMEN
Despite its many cited benefits, ultrasound guidance for neuraxial procedures is not widespread in anesthesiology. Some cited limitations include device cost and accessibility. We test the hypothesis that a handheld and relatively inexpensive ultrasound can improve neuraxial proficiency (e.g., decreased needle manipulations and block time). This prospective study compared the number of needle passes, redirections, and procedural time between epidural placed with a handheld ultrasound versus landmarks. Needle passes and attempts were defined as the number of times the Tuhoy needle was redirected, and the times skin was punctured (re-insertion). Procedural time was defined as the time from local anesthetic infiltration until loss of resistance was obtained. The impact of level of training and accuracy of the device were also analyzed. 302 patients receiving labor epidural were included in the study. No difference in body mass index (BMI) nor distribution of level of training was noted between the groups. Regression analysis adjusted for BMI demonstrated a decrease in needle passes (-1.75 (95% CI -2.62, -0.89), p < 0.001), needle attempts (-0.51 (95% CI -0.97, -0.04), p = 0.032) and procedural time (-154.67s 95% CI -303.49s, -5.85s), p = 0.042) when a handheld ultrasound was utilized. The mean (95% Confidence interval) difference between needle depth and ultrasound depth was 0.39 cm (0.32, 0.46), p < 0.001. The use of a handheld device resulted in statistically significant decrease of needle manipulations and block time. More research is needed to evaluate the impact of and increase in accessibility of ultrasound technology.
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Background: Point-of-care testing provides a representation of the patient's coagulability status during effective postpartum hemorrhage management. Baseline values of rotational thromboelastometry (ROTEM) have not yet been reported in a heterogeneous obstetric population. This study aimed to establish a baseline for a diverse population representative of the United States. The secondary aim was to evaluate the association of these hematologic parameters with comorbidities, race, and socioeconomic factors. Methods: The study was a retrospective review of collected ROTEM values of women undergoing vaginal or cesarean delivery with a history of or at risk for postpartum hemorrhage. Patients were divided into healthy and comorbid groups. Exclusion criteria for both groups included active or recent bleeding, receipt of blood products or clot-enhancing factors, and liver disease. Mean values of ROTEM by race and comorbidities were included. Median values were reported for intrinsic pathway thromboelastometry (INTEM), extrinsic pathway thromboelastometry (EXTEM), and fibrin polymerization thromboelastometry (FIBTEM) amplitude at 10 minutes (A10) and 20 minutes (A20), coagulation time, clot formation time, and maximum clot firmness. Results: A total of 681 records were reviewed; 485 met inclusion criteria, and 267 met healthy criteria. The mean (standard deviation) demographics for maternal age (years), body mass index (kg/m2), and gestational age (weeks) were 32.2 (5.7), 34 (7.3), and 35.4 (5), respectively. The median INTEM, EXTEM, and FIBTEM A10 were 63, 65, and 23 mm. The mean for INTEM, EXTEM, and FIBTEM A10 was increased for those who were Black or obese, whereas a decreased FIBTEM and EXTEM A10 was noted in those who were Asian or those who had the hemolysis, elevated liver enzymes, low platelet syndrome. Conclusions: Our heterogeneous population presents ROTEM values within the interquartile range of those previously reported in European studies. Black race, obesity, and preeclampsia were associated with hypercoagulable profiles.
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Objective. To study the photoplethysmographic (PPG) waveforms of different locations (ear and finger) during lower body negative pressure (LBNP) induced hypovolemia. Then, to determine whether the PPG waveform can be used to detect hypovolemia during the early stage of LBNP.Approach. 36 healthy volunteers were recruited for progressive LBNP induced hypovolemia, with an endpoint of -60 mmHg or development of hypoperfusion symptoms, whichever comes first. Subjects tolerating the entire protocol without symptoms were designated as high tolerance (HT), while symptomatic subjects were designated as low tolerance (LT). Subjects were monitored with an electrocardiogram, continuous noninvasive blood pressure monitor, and two pulse oximetry probes, one on the ear (Xhale) and one the finger (Nellcor). Stroke volume was measured non-invasively utilizing Non-Invasive Cardiac Output Monitor (NICOM, Cheetah Medical). The waveform morphology was analyzed using novel PPG waveforms indices, including phase hemodynamic index (PHI) and amplitude hemodyamaic index and were evaluated from the ear PPG and finger PPG at different LBNP stages.Main results. The PHI, particularly the phase relationship between the second harmonic and the fundamental component of the ear PPG denoted as∇φ2,during the early stage of LBNP (-15 mmHg) in the HT and LT groups is statistically significantly different (pvalue = 0.0033) with the area under curve 0.81 (CI: 0.616-0.926). The other indices are not significantly different. The 5 fold cross validation shows that∇φ2during the early stage of LBNP (-15 mmHg) as the single index could predict the tolerance of the subject with the sensitivity, specificity, accuracy andF1 as 0.771 ± 0.192, 0.71 ± 0.107, 0.7 ± 0.1 and 0.771 ± 0.192 respectively.Significance. The ear's PPG PHI which compares the phases of the fundamental and second harmonic has the potential to be used as an early predictor of central hypovolemia.
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Hipovolemia , Presión Negativa de la Región Corporal Inferior , Humanos , Hipovolemia/diagnóstico , Voluntarios Sanos , Hemodinámica , Oximetría , Presión SanguíneaRESUMEN
OBJECTIVES: Continuous hemodynamic monitoring offers the opportunity to individualize management in severe preeclampsia (PEC). We compared cardiac output (CO) and total peripheral resistance (TPR) measured by bioreactance (NICOM), Clearsite™ Fingercuff [CS), and 3D-echocardiography (3DE). STUDY DESIGN: This prospective observational study included 12 pregnant patients with early PEC. CO and TPR were measured simultaneously by NICOM, CS, and 3DE antepartum and 1-2 days postpartum. Using 3DE as the standard, CS and NICOM interchangeability, precision, accuracy, and correlation were assessed. RESULTS: Compared to 3DE-CO, CS-CO was highly correlated (R2 = 0.70, p = <0.0001) with low percentage error (PE 29%) which met criteria for interchangeablity. CS-TPR had strong correlation (R2 = 0.81, p = <0.0001) and low PE (29%). While CS tended to slightly overestimate CO (bias + 2.05 ±1.18 L/min, limit of agreement (LOA) -0.20 to 4.31) and underestimate TPR (bias -279 ±156 dyes/sec/cm5; LOA -580 to 18.4) these differences were unlikely to be clinically significant. Thus CS could be interchangeable with 3DE for CO and TPR. NICOM-CO had only moderate correlation with 3DE-CO (R2 = 0.29, p = 0.01) with high PE (52%) above threshold for interchangeability. NICOM-CO had low mean bias (-1.2 ±1.68 L/min) but wide 95% LOA (-4.41 to 2.14) suggesting adequate accuracy but low precision in relation to 3DE-CO. NICOM-TPR had poor correlation with 3DE-TPR (R2 = 0.32, p = 0.001) with high PE (67%), relatively low mean bias (238 ±256), and wide 95% LOA (-655 to 1131). NICOM did not meet the criteria for interchangeable with 3DE for CO and TPR. CONCLUSIONS: Clearsite Fingercuff, but not NICOM, has potential to be clinically useful for CO and TPR monitoring in severe preeclampsia.
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Monitorización Hemodinámica , Preeclampsia , Embarazo , Femenino , Humanos , Preeclampsia/diagnóstico , Monitoreo Fisiológico , Gasto Cardíaco , Resistencia VascularAsunto(s)
Anestesiólogos , Análisis de Ondículas , Adulto , Fenómenos Fisiológicos Cardiovasculares , Vasos Coronarios/fisiopatología , Interpretación Estadística de Datos , Electrocardiografía , Femenino , Hemodinámica , Humanos , Masculino , Feocromocitoma/diagnóstico , Feocromocitoma/fisiopatología , Fotopletismografía , Hemorragia Posoperatoria/diagnóstico por imagen , Adulto JovenRESUMEN
The photoplethysmographic waveform sits at the core of the most used, and arguably the most important, clinical monitor, the pulse oximeter. Interestingly, the pulse oximeter was discovered while examining an artifact during the development of a noninvasive cardiac output monitor. This article will explore the response of the pulse oximeter waveform to various modes of ventilation. Modern digital signal processing is allowing for a re-examination of this ubiquitous signal. The effect of ventilation on the photoplethysmographic waveform has long been thought of as a source of artifact. The primary goal of this article is to improve the understanding of the underlying physiology responsible for the observed phenomena, thereby encouraging the utilization of this understanding to develop new methods of patient monitoring. The reader will be presented with a review of respiratory physiology followed by numerous examples of the impact of ventilation on the photoplethysmographic waveform.
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Determinación del Volumen Sanguíneo/métodos , Modelos Biológicos , Oximetría/métodos , Oxígeno/sangre , Fotopletismografía/métodos , Ventilación Pulmonar/fisiología , Mecánica Respiratoria/fisiología , Animales , HumanosRESUMEN
Objectives: Not all labor and delivery floors are equipped with ultrasound machines which can serve the needs of both obstetricians and anesthesiologists. This cross-sectional, blinded, randomized observational study compares the image resolution (RES), detail (DET), and quality (IQ) acquired by a handheld ultrasound, the Butterfly iQ, and a mid-range mobile device, the Sonosite M-turbo US (SU), to evaluate their use as a shared resource. Methods: Seventy-four pairs of ultrasound images were obtained for different imaging purposes: 29 for spine (Sp), 15 for transversus abdominis plane (TAP) and 30 for diagnostic obstetrics (OB) purposes. Each location was scanned by both the handheld and mid-range machine, resulting in 148 images. The images were graded by three blinded experienced sonographers on a 10-point Likert scale. Results: The mean difference for Sp imaging favored the handheld device (RES: -0.6 [(95% CI -1.1, -0.1), p = 0.017], DET: -0.8 [(95% CI -1.2, -0.3), p = 0.001] and IQ: -0.9 [95% CI-1.3, -0.4, p = 0.001]). For the TAP images, there was no statistical difference in RES or IQ, but DET was favored in the handheld device (-0.8 [(95% CI-1.2, -0.5), p < 0.001]). For OB images, the SU was favored over the handheld device with RES, DET and IQ with mean differences of 1.7 [(95% CI 1.2, 2.1), p < 0.001], 1.6 [(95% CI 1.2, 2.0], p < 0.001] and 1.1 [(95% CI 0.7, 1.5]), p < 0.001), respectively. Conclusions: Where resources are limited, a handheld ultrasound may be considered as a potential low-cost alternative to a more expensive ultrasound machine for point of care ultrasonography, better suited to anesthetic vs. diagnostic obstetrical indications.
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OBJECTIVE: The photoplethysmographic (PPG) waveforms are modulated by the respiratory, cardiac and autonomic nervous system. Lower body negative pressure (LBNP) has been used as an experimental tool to simulate loss of central blood volume in humans. The aim of our research is to understanding PPG waveform changes during progressive hypovolemia. METHODS: With IRB approval, 11 volunteers underwent a LBNP protocol at baseline, 30, 75, and 90 mmHg (or until the subject became symptomatic). Subjects were monitored with finger and ear pulse oximeter probes, ECG, and finger arterial blood pressure monitor (FABP). Heart rate variability (HRV) was analyzed to high frequency (HRV-HF) (0.12-0.4 Hz) and low frequency (HRV-LF) (0.04-0.12 Hz). Frequency analysis of PPG waveforms were computed to low (0.04-0.11 Hz) frequency (PPG-LF), intermediate (0.12-0.18 Hz) frequency (PPG-IF), respiratory (0.19-0.3 Hz) frequency (PPG-Resp.) and cardiac (0.75-2.5 Hz) frequency (PPG-Cardiac)during different phases of LBNP protocol RESULTS: Heart rate increased significantly while systolic, mean and pulse pressure of the FABP declined slowly together with significant reductions in HRV-HF (0.12-0.4 Hz) and HRV-LF (0.04-0.12 Hz) power at LBNP(75). There was significant reduction in finger PPG-Cardiac modulation which is consistent with the reduction in the pulse pressure of the FABP. As the LBNP progress there was shift in the amplitude density of the ear PPG-Cardiac to PPG-Resp. Oscillation as an evidence of progressive hypovolemia with reduction in pulse pressure and increase in the respiratory induced variations. At LBNP(75), there were significant increased (>140% increase from the baseline) in ear PPG-IF (0.12-0.18 Hz) in the meantime HRV-HF showed significant reduction (>89%) from the baseline. At the symptomatic phase; there was a shift in ear PPG-IF to PPG-Resp. With an increase in the ear PPG-Resp. Modulation to ≥175% from the baseline CONCLUSION: The pulse oximeter waveform contains a complex mixture of the effect of cardiac, venous, autonomic, and respiratory systems on the central and peripheral circulation. The occurrence of autonomic modulation needs to be taken into account when studying signals that have their origins from central sites (e.g. ear and forehead).
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Algoritmos , Determinación del Volumen Sanguíneo/métodos , Diagnóstico por Computador/métodos , Hipovolemia/diagnóstico , Hipovolemia/fisiopatología , Presión Negativa de la Región Corporal Inferior , Fotopletismografía/métodos , Adulto , Femenino , Humanos , Masculino , Valores de Referencia , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
INTRODUCTION: Our study sought to explore changes in photoplethysmographic (PPG) waveform param- eters, during lower body negative pressure (LBNP) which simulated hypovolemia, in spontaneously breathing volunteers. We hypothesize that during progressive LBNP; there will be a preservation of ear PPG parameters and a decrease in finger PPG parameters. METHODS: With IRB approval, 11 volunteers underwent a LBNP protocol at baseline, 30, 75, and 90 mm Hg (or until the subject became symptomatic). Subjects were monitored with finger and ear pulse oximeter probes, an ECG, and a finger arterial blood pressure monitor. The square root of the mean of the squared differences between adjacent NN intervals (RMSSD) which is the time domain analysis of the heart rate variability (HRV) was measured. PPG waveforms were analyzed for height, area, width 50, maximum and minimum slope. Data are presented as median and inter-quartile range. Friedman ANOVA and Wilcoxon tests were used to identify changes in hemo- dynamic and PPG parameters, P < 0.017 was considered statistically significant. RESULTS: There were no significant changes in the blood pressure variables at LBNP(30), but at and beyond LBNP(75), the decreases in systolic, mean and pulse pressure were significant as was the increase in diastolic pressure. Heart rate increased significantly at LBNP(30), reaching a maximum of 75.4% above baseline at the symptomatic phase while RMSSD showed significant reduction at LBNP(75). Finger PPG height, area, width 50, and maximum slope decreased significantly at LBNP(30) and during symptomatic phase they showed a reduction of 59.4, 76.9, 27.4 and 51.6%, respectively. Ear PPG height, area, width 50 and maximum slope did not change significantly until the LBNP(75), reached. During symptomatic phase, the respective declines reached 39.3, 61.0, 21.4 and 34.9%. CONCLUSION: PPG waveform parameters may prove to be sensitive and specific as early indicators of blood loss. These PPG changes were observed before profound decreases in arterial blood pressure. The relative sparing of central cutaneous blood flow is consistent with the increased parasympathetic innervation of central structures.
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Algoritmos , Determinación del Volumen Sanguíneo/métodos , Diagnóstico por Computador/métodos , Hipovolemia/diagnóstico , Hipovolemia/fisiopatología , Presión Negativa de la Región Corporal Inferior , Fotopletismografía/métodos , Adulto , Femenino , Humanos , Masculino , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
OBJECTIVES: Aberrant automated blood pressure (BP) readings during caesarean delivery may lead to disruptions in monitoring. The present study compared the frequency of aberrant BP readings across two types of commercially available BP monitoring systems in use during caesarean delivery. METHODS: This was a retrospective observational study using two comparable patient cohorts that resulted from simultaneous introduction of two types of monitors into a single obstetric surgical center in which similar patients were treated for the same surgical procedure by the same set of clinicians during the same year. Our primary hypothesis was that aberrant readings were significantly associated with the type of monitor being used for BP measurement, controlling for a variety of relevant covariates as specified in the analytic plan. RESULTS: A total of 1418 cesarean delivery patients met inclusion criteria. Gaps of at least 6 min in machine-captured BP readings occurred in 159 (21.1%) of cases done in the operating room using a Datex-Ohmeda monitor vs. 183 (27.5%) of cases in the operating rooms using Phillips monitors (P = 0.005). In multivariable logistic regression analysis, the relative odds of the occurrence of monitoring gaps was 35% higher in rooms with the Phillips BP monitors as compared to the Datex-Ohmeda monitor while controlling for pre-specified covariates (odds ratio = 1.35, 95% confidence interval = 1.04-1.74, P = 0.02). CONCLUSION: The present analysis suggests that aberrant BP readings for parturients undergoing caesarean delivery are significantly different between the two types of automated BP monitoring systems used in the operating rooms at our institution.
Asunto(s)
Determinación de la Presión Sanguínea , Cesárea , Presión Sanguínea , Monitoreo Ambulatorio de la Presión Arterial , Monitores de Presión Sanguínea , Femenino , Humanos , Embarazo , Prevalencia , Estudios RetrospectivosRESUMEN
Over the past 30 years, maternal mortality has increased in the United States to 18 deaths per 100,000 live births. Obstetric emergencies, including hemorrhage, hypertensive disorders in pregnancy, HELLP syndrome, and amniotic fluid embolism, and anesthesia complications, including high neuraxial blockade, local anesthetic systemic toxicity, and the difficult obstetric airway, contribute to maternal cardiac arrest and maternal and fetal morbidity and mortality. Expeditious intervention by the obstetric anesthesiologist is critical in these emergent scenarios, and knowledge of best practices is essential to improve maternal and fetal outcomes.