Effect of Peripheral Vasoconstriction on Pulse Oximetry

Objective. We tested the hypothesis that peripheral vasodilation has an effect on arterial oxygen saturation measurements by pulse oximetry, independent of temperature. Methods. Study 1 compared finger arterial oxygen saturation values (SpO₂), before and after peripheral vasoconstriction while temperature was kept constant. This was achieved by administering dexmedetomidine (peripheral vasoconstrictor) to 16 volunteers given general anesthesia. Study 2 compared SpO₂ before and after peripheral vasodilation (brachial plexus block) in a neurally denervated left hand and a neurally innervated right hand in ten awake volunteers. In both studies measurements were also made of finger blood volume (an indicator of vasoconstriction) by photoplethysmographic determination of light transmission through a finger (LTF), finger temperature and of hemodynamic variables. Results. In Study 1, systolic blood pressure, SpO₂ and LTF values increased (vasoconstriction) during dexmedetomidine infusion, (P<0.0001 for all) while there were no changes in finger temperature. In Study 2, in the left hand (axillary block), temperature increased by 1.9 ± 1.6 °C (P=0.004), SpO₂ decreased by 2.5 ± 1.0 % (P<0.0001) and LTF values decreased (vasodilation) by 42 ± 8 % (P<0.0001) after axillary block. Simultaneously, the axillary block did not induce any changes in temperature, SpO₂ or LTF values in the neurally innervated right hand. Conclusions. Our results demonstrate that finger pulse oximeter SpO₂ measurements can be affected by peripheral vascular tone independent of temperature. The mechanism for this effect remains speculative and unproven.     

Global versus local linear beat-to-beat analysis of the relationship between arterial pressure and pulse transit time during dynamic exercise

Global linear analysis has been traditionally performed to verify the relationship between pulse transit time (PTT) and systolic arterial pressure (SAP) at the level of their spontaneous beat-to-beat variabilities: PTT and SAP have been plotted in the plane (PTT,SAP) and a significant linear correlation has been found. However, this relationship is weak and in specific individuals cannot be found. This result prevents the utilization of the SAP–PTT relationship to derive arterial pressure changes from PTT measures on an individual basis. We propose a local linear approach to study the SAP–PTT relationship. This approach is based on the definition of short SAP–PTT sequences characterized by SAP increase (decrease) and PTT decrease (increase) and on their search in the SAP and PTT beat-to-beat series. This local approach was applied to PTT and SAP series derived from 13 healthy humans during incremental supine dynamic exercise (at 10, 20 and 30% of the nominal individual maximum effort) and compared to the global approach. While global approach failed in some subjects, local analysis allowed the extraction of the gain of the SAP–PTT relationship in all subjects both at rest and during exercise. When both local and global analyses were successful, the local SAP–PTT gain is more negative than the global one as a likely result of noise reduction.     

Filtering techniques for the removal of ventilator artefact in oesophageal pulse oximetry

The oesophagus has been shown to be a reliable site for monitoring blood oxygen saturation (SpO₂). However, the photoplethysmographic (PPG) signals from the lower oesophagus are frequently contaminated by a ventilator artefact making the estimation of SpO₂ impossible. A 776th order finite impulse response (FIR) filter and a 695th order interpolated finite impulse response (IFIR) filter were implemented to suppress the artefact. Both filters attenuated the ventilator artefact satisfactorily without distorting the morphology of the PPG when processing recorded data from ten cardiopulmonary bypass patients. The IFIR filter was the better since it conformed more closely to the desired filter specifications and allowed real-time processing. The average improvements in signal-to-noise ratio (SNR) achieved by the FIR and IFIR filters for the fundamental component of the red PPG signals with respect to the fundamental component of the artefact were 57.96 and 60.60 dB, respectively. The corresponding average improvements achieved by the FIR and IFIR filters for the infrared PPG signals were 54.83 and 60.96 dB, respectively. Both filters were also compared with their equivalent tenth order Butterworth filters. The average SNR improvements for the FIR and IFIR filters were significantly higher than those for the Butterworth filters.     

Transcatheter closure of patent foramen ovale during a radiofrequency ablation procedure

A 43-year-old woman was undergoing radiofrequency catheter ablation of a symptomatic supraventricular tachycardia when a patent foramen ovale (PFO) was detected with passage of the diagnostic electrocatheter into the left atrium. Prior echocardiographic studies had been unrevealing. Upon questioning during the procedure, the patient now admitted to frequent and disabling daily migraine attacks, while her family described two recent brief episodes of disorientation and dysarthria, consistent with transient ischemic attacks. The patient was informed of the option of future closure of the PFO, but she insisted on having this done concurrently with her ablation procedure. After successful ablation of the slow pathway considered responsible for the supraventricular tachycardia, an Amplatzer closure device was utilized and the PFO was successfully closed during the same procedure. A postprocedural transesophageal echocardiogram showed complete sealing of the PFO, while over the ensuing 10 months the patient reported virtual elimination of her daily attacks of migrainous headaches, limited to a single episode the day after the procedure and none thereafter.     

双极射频消融心房颤动同时手术治疗器质性心脏病的临床效果

目的：探讨双极射频消融钳治疗心房颤动同期行开胸手术治疗器质性心脏病的手术方法和临床结果,提高对此类疾病的治疗水平。方法：回顾分析2009年8月～2012年5月对58例器质性心脏病并发心房颤动用双极射频消融钳治疗房颤的临床资料。结果：本组患者手术均顺利完成。射频时间16～38（24±4） min,主动脉阻断时间64～200（126±36） min,体外循环时间91～238（150±37） min;手术结束及出院时窦性心率分别为46（79%）,45（78%）例,随访3个月,6个月和12个月,窦性心率分别为41（71%）,40（69%）和42（72%）例。全组病例无手术死亡和射频相关并发症。所有患者均无需安装永久起搏器。双心房消融与单独左房消融比较无显著差异。结论：此方法可行,效果满意,但要注意把握适应证。     

Non-invasive 24 hour ambulatory monitoring of aortic wave reflection and arterial stiffness by a novel oscillometric device: The first feasibility and reproducibility study

Background

Surrogates of aortic wave reflection and arterial stiffness, such as augmentation index (AIx), augmentation pressure, pulse wave velocity (PWV) and pulse pressure amplification (PPampl) are independent predictors of cardiovascular risk. A novel ambulatory, brachial cuff-based oscillometric device has been recently developed and validated, yielding 24-h assessment of the aforementioned parameters (Mobilo-O-Graph). Aim of this study was to investigate the feasibility and reproducibility of wave reflection and arterial stiffness estimation by pulse wave analysis using this device.

Methods

Thirty treated or untreated hypertensives (mean age: 53.6 ± 11.6 years, 17 men) had test–retest 24-h monitoring one week apart using the test device.

Results

Mean numbers of valid aortic readings per subject, between test and retest, were comparable. Approximately 12 aortic readings per subject (17%) were not feasible or valid. No differences were observed for any 24-h parameter between the two assessments. Bland–Altman plots showed no systemic difference, while the limits of agreement for each parameter indicated high reproducibility (AIx: − 7.2 to 8.2%, AP: − 3.7 to 4.1 mm Hg, PWV: − 0.39 to 0.41 m/s, PPampl: − 0.08 to 0.06). This was further verified by intraclass correlation coefficients which were > 0.8 for each parameter.

Conclusions

Non-invasive 24-h estimation of wave reflection and arterial stiffness indices, derived by the test device, appear to be highly reproducible. Future studies should investigate whether these measurements have additive prognostic value for cardiovascular risk stratification, beyond common brachial blood pressure measurements or single estimations of wave reflection and PWV at office settings.     

内镜头端透明帽辅助食管上段异物治疗的对照研究

目的通过比较非镇静状态下透明帽辅助治疗与常规内镜治疗前、治疗中2 min时血压、脉搏、血氧饱和度的动态变化,作呕反应程度,治疗完成时间,食管黏膜损伤情况和视野清晰度,以评价内镜头端透明帽辅助食管上段异物取出的可行性、安全性、有效性和耐受性。方法将144例患者随机分为透明帽辅助治疗组(72例)和常规内镜治疗组(72例);分别监测患者检查前、检查中2 min时的血压、脉搏、血氧饱和度,作呕反应程度,治疗完成时间,食管黏膜损伤情况和视野清晰度。结果透明帽辅助治疗组的血压、脉搏、血氧饱和度变化与常规内镜治疗组比较差异无统计学意义(P>0.05);透明帽辅助治疗组的视野清晰度明显高于常规内镜治疗组(P<0.01);透明帽辅助治疗组的治疗完成时间、作呕反应、黏膜损伤率均低于常规内镜治疗组(P<0.05)。结论内镜头端透明帽辅助食管上段异物治疗是一种可行、安全、有效的治疗方法,并具有较好的耐受性。     

超声心动图对ICU心源性休克患者心输出量测定准确性的临床研究

目的:对入住ICU的心源性休克患者,同时使用脉搏指示的连续性心输出量(Pulse indicator continuous cardiac output,PiCCO)监测技术以及超声心动图进行心输出量(Cardiac output,CO)测定,以PiCCO测定的有创数据为标准,对超声心动图CO测定的准确性进行评估。方法:选择2011年1月-2012年12月入住我院ICU需要进行血流动力学监测的心源性休克患者共43例,对这些患者同时进行PiCCO监测技术以及使用双平面Simpson法进行无创CO测定,对比两者CO差异,以判断超声心动图CO测定的准确性。结果:共有40例患者获得满意的二维图像,其中男28例,女12例,最大年龄78岁,最小年龄22岁,另外3例患者因未获得满意图像而被放弃。对比结果显示,超声心动图和PiCCO测定的CO分别为(3.18±0.60)ml/min及(3.58±0.97)ml/min(P>0.05),两组数据无显著差异。结论:超声心动图CO测定是一种快速、准确、无创的血流动力学监测技术,适合在ICU心源性休克患者中进行CO测定。     

经皮射频消融序贯~(125)I粒子植入治疗恶性肿瘤的疗效观察

目的评估射频消融序贯~(125)I粒子植入方法治疗恶性实体肿瘤的近期疗效和安全性。方法回顾性分析2009年8月—2012年12月广东省中医院肿瘤科经皮射频消融序贯~(125)I粒子植入治疗14例恶性肿瘤患者的临床资料,并分析短期疗效(目标肿瘤控制率)及安全性。结果经皮射频消融治疗术后复查手术病灶影像,14例患者共21处病灶肿瘤仍有活性,且患者可耐受进一步局部治疗,遂行~(125)I粒子植入治疗。14例患者肿瘤中位直径5.8(2.0～7.8)cm,治疗均获成功,无治疗相关死亡,主要并发症为胆心反射2例,发热9例,所有患者射频消融时均有治疗相关疼痛,轻度疼痛10例(71.4%),中重度疼痛4例(28.6%)。目标肿瘤完全缓解(CR)率为35.7%(5/14),部分缓解(PR)率50.0%(7/14),中位无疾病进展时间(PFS)为12个月,中位生存时间(OS)为30个月。1年目标肿瘤控制率(CR+PR)为60.0%,1年生存率为70.0%。结论对直径较大(>5 cm)或特殊部位的肿瘤,经皮射频消融序贯~(125)I粒子植入是安全、有效的,值得进一步研究。