Photoplethysmographic waveform characteristics of newborns with coarctation of the aorta.

OBJECTIVE: Fetal echocardiography, physical examination and pulse oximetry detect only half of coarctation of aorta (CoA) cases. We aimed to quantify delayed arrival and diminished amplitude of lower extremity photoplethysmographic (PPG) pulses relative to the right hand in affected patients. STUDY DESIGN: We studied 8 CoA infants and 32 healthy controls. The pulse arrival time difference between foot and hand (f-hTD) and pulse amplitude ratio (F/H) were measured on PPG signal waveforms by digitally-determining maxima and minima of systolic decrease of light transmission. Mann-Whitney test was used for group comparisons. RESULTS: In comparison to healthy newborns, CoA infants' PPG waveforms demonstrated prolonged f-hTD (mean±s.d. of 73.2±26.6 versus 35.2±8.3 ms, P<0.001) and lower F/H (0.57±0.26 versus 0.99±0.58, P=0.014). CONCLUSIONS: F-hTD and F/H are quantifiable from hand- and foot-derived PPG waveforms and are significantly different in CoA versus healthy newborns. Larger studies are needed to validate PPG for improved critical congenital heart disease screening.

Effect of lingual gauze swab placement on pulse oximeter readings in anaesthetised dogs and cats.

This study aimed to evaluate the effect of lingual gauze swab placement on pulse oximeter readings in anaesthetised dogs and cats. Following anaesthetic induction, the following pulse oximeter probe configurations were performed: no gauze swab (control), placement of a gauze swab between the tongue and the probe, placement of different thicknesses of gauze swab, placement of red cotton fabric, placement of a sheet of white paper and placement of the probe and gauze swab on different locations on the tongue. Oxygen saturation (SpO2) and peripheral perfusion index (PI) were recorded. Placement of a gauze swab between the pulse oximeter probe and the tongue in anaesthetised dogs and cats resulted in significantly higher SpO2 values compared with the control group. In dogs, PI values were significantly higher than the control in all groups except the quarter thickness swab group. In cats, PI was significantly higher in the double thickness swab and white paper groups compared with the control. Cats had significantly higher SpO2 and lower PI values than dogs. The authors propose that increased contact pressure is responsible for significantly higher SpO2 and PI readings with the use of a lingual gauze swab resulting from changes in transmural pressure and arterial compliance.

Pulse oximeter perfusion index as an early indicator of sympathectomy after epidural anesthesia.

BACKGROUND: The pulse oximeter perfusion index (PI) has been used to indicate sympathectomy-induced vasodilatation. We hypothesized that pulse oximeter PI provides an earlier and clearer indication of sympathectomy following epidural anesthesia than skin temperature and arterial pressure. METHODS: Forty patients received lumbar epidural catheters. Patients were randomized to receive either 10 ml 0.5% bupivacaine or 10 ml 0.25% bupivacaine. PI in the toe, mean arterial pressure (MAP) and toe temperature were all assessed at baseline and at 5, 10 and 20 min following epidural anesthesia. The effect of epidural anesthesia over time was assessed by repeated measures analysis of variance. Additionally, we defined clinically evident sympathectomy criteria (a 100% increase in the PI, a 15% decrease in MAP and a 1 degrees C increase in toe temperature). The numbers of patients demonstrating these changes for each test were compared using the McNemar test for each time point. RESULTS: Twenty-nine subjects had photoplethysmography signals that met a priori signal quality criteria for analysis. By 20 min, PI increased by 326%, compared with a 10% decrease and a 3% increase in MAP and toe temperature, respectively. For PI 15/29, 26/29 and 29/29 of the subjects met the sympathectomy criteria at 5, 10 and 20 min, respectively, compared with 4/29, 6/29 and 18/29 for MAP changes and 3/29, 8/29 and 14/29 for toe temperature changes. CONCLUSIONS: PI was an earlier, clearer and more sensitive indicator of the development of epidural-induced sympathectomy than either skin temperature or MAP.

Right-left correlation of the sympathetically induced fluctuations of photoplethysmographic signal in diabetic and non-diabetic subjects.

Photoplethysmography (PPG) records the cardiac-induced changes in tissue blood volume by light-transmission measurements. The baseline and amplitude of the PPG signal show very low-frequency (VLF) spontaneous fluctuations, which are mediated by the sympathetic nervous system, and high correlation between right and left extremities of healthy subjects. As sympathetic neuropathy is one of the diabetic complications, the right-left correlation of the PPG fluctuations was examined in diabetic patients. The PPG signal was simultaneously measured in the two index fingers and the two second toes of 35 diabetic patients and 33 non-diabetic subjects. For each PPG pulse, the baseline and amplitude were determined, and the right-left correlation coefficients of the VLF fluctuations in the baseline and amplitude were derived. The VLF fluctuations in the baseline showed high right-left correlation, both for fingers (0.93 +/- 0.05) and toes (0.93 +/- 0.06), for the non-diabetic subjects, and significantly lower correlation (0.78 +/- 0.22 and 0.84 +/- 0.17, respectively) for the diabetic patients. Similar results were obtained for the amplitude VLF fluctuations. The right-left correlation coefficients for diabetic patients decreased with the disease duration for the toe baseline and toe amplitude fluctuations and correlated with heart rate response to deep breathing for the finger baseline and toe amplitude fluctuations. The right-left correlation coefficients of the PPG fluctuations provide a simple and convenient means for assessing the adequacy of the sympathetic nervous system function.

Sympathetically induced spontaneous fluctuations of the photoplethysmographic signal.

The photoplethysmographic signal shows very low-frequency (VLF) spontaneous fluctuations that have been shown to be mediated by the sympathetic nervous system. In the current study, the photoplethysmographic signal was simultaneously measured in the two index fingers and the two second toes of 54 healthy male subjects. For each photoplethysmographic pulse, two parameters were derived: the pulse amplitude and its baseline, which are related to the arterial wall compliance and to the arterial blood volume, respectively. The baseline and the amplitude VLF fluctuations showed high right-left correlation both for hands (mean +/- SD 0.94 +/- 0.05 and 0.92 +/- 0.07, respectively) and for feet (0.90 +/- 0.08 and 0.89 +/- 0.07, respectively) that only slightly depended on the subject's age. Lower correlation was found between the hand and the foot (0.73 +/- 0.12 and 0.72 +/- 0.12 for the baseline and the amplitude, respectively). For each hand and foot the baseline and the amplitude VLF fluctuations were also correlated, with the baseline fluctuations lagging the amplitude fluctuations by 3-20 pulses. The amplitude-baseline correlation and the standard deviation of the amplitude or the baseline divided by its mean significantly decreased with age. The VLF fluctuations of the photoplethysmographic parameters and the correlation coefficients between them provide better understanding of the autonomic nervous regulation of the blood circulation.

The difference in pulse transit time to the toe and finger measured by photoplethysmography.

Blood pressure pulse wave velocity (PWV) is a parameter which is related to arterial distensibility. Its direct assessment, by measuring the appearance time of a pressure pulse in two sites along an artery and the distance between the two sites, is complicated and inaccurate. In the current study, pulse transit time (PTT) to the toes and fingers of 44 normotensive male subjects was measured by photoplethysmography (PPG) and ECG. The arrival time of the pulses at the toe and finger was determined from the foot of the systolic rise of the PPG signal, i.e. at end-diastolic time. Two parameters, which are related to PWV, were tested: the time delay between the ECG R-wave and the arrival time of the pulses at the toe (E-T PTT), and the difference in the transit time of the blood pressure pulses between the toe and finger (T-F PTTD). E-T PTT and T-F PTTD decreased as functions of the subject's age and systolic blood pressure (SBP), but their dependence on the diastolic blood pressure (DBP) was not statistically significant. The decrease of the PTT parameters with age is attributed to the direct structural decrease of the arterial compliance with age and not to functional effects associated with the increase of the blood pressure with age, since the PTT parameters did not depend on DBP though the measurements were performed at end-diastole.

Influence of thoracic sympathectomy on cardiac induced oscillations in tissue blood volume.

The photoplethysmographic (PPG) signal, which measures cardiac-induced changes in tissue blood volume by light transmission measurements, shows spontaneous fluctuations. In this study, PPG was simultaneously measured in the right and left index fingers of 16 patients undergoing thoracic sympathectomy, and, from each PPG pulse, the amplitude of the pulse (AM) and its maximum (BL) were determined. The parameter AM/BL is proportional to the cardiac-induced blood volume increase, which depends on the arterial wall compliance. AM/BL increased after the thoracic sympathectomy treatment (for male patients, from 2.60+/-1.49% to 4.81+/-1.21%), as sympathetic denervation decreases arterial tonus in skin. The very low-frequency (VLF) fluctuations of BL or AM showed high correlation (0.90+/-0.11 and 0.92+/-0.07, respectively) between the right and left hands before the thoracic sympathectomy, and a significant decrease in the right-left correlation coefficient (to 0.54+/-0.22 and 0.76+/-0.20, respectively) after the operation. The standard deviation of the BL or AM VLF fluctuations also reduced after the treatment, indicating sympathetic mediation of the VLF PPG fluctuations. The study also shows that the analysis of the PPG signal and the VLF fluctuations of the PPG parameters enable the assessment of the change in sympathetic nervous system activity after thoracic sympathectomy.

Photoplethysmographic measurement of changes in total and pulsatile tissue blood volume, following sympathetic blockade.

Epidural anaesthesia, used for pain relief, is based on blocking the sensory and the sympathetic nerves in the lower part of the body. Since the sympathetic nervous system regulates blood vessel diameter, the sympathetic block is also associated with several haemodynamic changes. In the current study photoplethysmography (PPG) was measured on toes and fingers of patients undergoing epidural anaesthesia. Three parameters, which are related to the change in total and pulsatile tissue blood volume, were derived from the PPG baseline and amplitude. All parameters showed statistically significant increase in the toes after the sympathetic block, indicating higher arterial and venous blood volume and higher pulsatile increase in the arterial blood volume (higher arterial compliance) in the toe. These haemodynamic changes originate from the lower tonus of the arterial and venous wall muscles after the sympathetic block. In the fingers the PPG parameters based on the change in PPG amplitude decreased after the sympathetic block, indicating lower compliance. The measurement of the haemodynamic changes by PPG enables the assessment of the depth of anaesthesia, and can help control the adverse effects of the blockade on the vascular system.

Measurement of oxygen saturation in venous blood by dynamic near infrared spectroscopy.

A method for the measurement of oxygen saturation in the venous blood, SvO2, based on optical measurements of light absorption in the infrared region is presented. The method consists of applying relatively low external pressure of 25 mm Hg on the forearm, thereby increasing the venous blood volume in the tissue, and comparing the light absorption before and after the external pressure application. SvO2 has been determined from light absorption measurements in two wavelengths, before and after the pressure application, using a formula derived for two adjacent wavelengths. The method has been applied to the hands and fingers of 17 healthy male subjects, using wavelengths of 767 and 811 nm. SaO2, the oxygen saturation for arterial blood, was also obtained from photoplethysmographic measurements in these two wavelengths (pulse oximetry) using the same formula. The mean (+/- SD) value of SaO2 was 94.5% (+/- 3.0). The mean value of SvO2 was 86.2% (+/- 4.1) for the finger and 80.0% (+/- 8.2) for the hand. These SvO2 values are reasonable for the finger and the hand where arterio-venous anastomoses exist. The method enables the measurement of SvO2 in the limbs, a parameter which is related to tissue blood flow and oxygen consumption.

Soluble CD14 in children with status asthmaticus.

BACKGROUND: Inflammation is a major component in the pathogenesis of asthma. CD14 is an endotoxin (lipopolysaccharide) receptor, and is expressed mainly on monocytes and macrophages. Binding of LPS to CD14 activates the monocyte or macrophage and causes the release of different cytokines. The soluble form of CD14 is present in serum, and its concentration increases in several clinical conditions, including infections, autoimmune disorders, allergic disorders, and lung diseases. The possible role of CD14/sCD14 in asthma has been investigated in a few adult patients only. OBJECTIVES: To measure serum concentrations of sCD14 in children with status asthmaticus. METHODS: We compared serum concentration of sCD14 in 10 children with status asthmaticus measured within 24 hours of admission and after recovery from the acute episode. RESULTS: Levels of sCD14 were significantly higher during acute asthma attacks than at recovery. CONCLUSIONS: The elevated serum levels of sCD14 during status asthmaticus may be the result of the activation of monocytes, macrophages or other cells. The influence of medications on serum sCD14 cannot be ruled out. The possible use of sCD14 as a marker of lung inflammation in asthma warrants further investigation.

Increase in pulse transit time to the foot after epidural anaesthesia treatment.

Epidurally induced anaesthetic treatment is a routine treatment for pain relief during surgical procedure, based on blocking the sensory and sympathetic fibres that mediate pain. The epidural sympathetic block results in relaxation of the muscle walls in the lower limbs, which can be assessed by the resultant haemodynamic changes. In the current study, the difference tt,f in the transit time of the blood pressure pulses between the toe and the finger is measured by photoplethysmography (PPG). Fifteen patients are administered 10 ml 0.25% of bupivacaine, ten patients are administered 10 ml 0.5%, and 17 patients are administered 40 ml 0.0625%. tt,f decreases as a function of the patient's age and blood pressure, both before and after the sympathetic block, owing to the decrease in arterial compliance with age and blood pressure. The time delay tt,f increases after the epidural treatment by 10.1+/-7.0 and by 16.8+/-10.8 ms for the 0.25% and the 0.5% concentrations, respectively. The time delay increase for the lowest concentration is not statistically significant. The toe-finger time delay change is found to reflect the haemodynamic changes induced by the sympathetic block with higher reliability than the routine methods of skin temperature or arterial blood pressure.

Very low frequency variability in arterial blood pressure and blood volume pulse.

Several parameters of the cardiovascular system fluctuate spontaneously owing to the activity of the autonomic nervous system. In the study, the simultaneous very low frequency (VLF) fluctuations of the arterial blood pressure, the tissue blood content and the tissue blood volume pulse are investigated. The latter two parameters are derived from the baseline BL and the amplitude AM of the photoplethysmographic (PPG) signal, measured on the fingertips of 20 healthy male subjects: the changes in the PPG parameters AM and BV, defined by BV = const.-BL, are related to the change in the tissue blood volume pulse and the total tissue blood volume, respectively. The VLF fluctuations in BV and AM are directly correlated, those of AM preceding those of BV by 4-13 heart-beats. The VLF fluctuations in the systolic (SBP) and the diastolic (DBP) blood pressure are inversely correlated to those of AM and BV, those of AM preceding those of SBP and lagging behind those of DBP by about one heart-beat. For most subjects, the period P of the PPG pulse, which is equal to the cardiac cycle period, directly correlates with AM and BV and inversely correlates with DBP and SBP. On average, the fluctuations of P precede those of AM by more than three heart-beats. The measurement of the VLF fluctuations in tissue blood volume, systolic blood volume pulse, diastolic and systolic blood pressure, and heart period, together with their interrelationship, can provide a better understanding of the autonomic nervous control of the peripheral circulation and a potential tool for the evaluation of its function.

Analysis of umbilical artery flow parameters during fetal variable decelerations using computerized Doppler waveforms.

Umbilical artery velocity waves were obtained by Doppler ultrasonography before, during, and after 20 episodes of fetal heart rate (FHR) variable decelerations (VD) during the active stage of labor in 8 women. During 50% of the VD periods, the umbilical artery resistance flow parameters increased significantly (p < 0.01). The increase in resistance preceded the decrease in FHR in six episodes (30%) of VD (AR-VD group; arterial resistance VD) and did not precede the change in FHR in another ten episodes (50%) of VD (VR-VD group; venous resistance VD). In the AR-VD group the FHR accelerations occurred before the decelerations in only 1 case (17%), while in the VR-VD group FHR accelerations preceded the decelerations in 8 out of the 10 episodes (80%). Using these Doppler studies, it may be possible to differentiate between two groups of VD: AR-VD - which are caused by umbilical artery occlusion and thus preceded by a measurable increase in umbilical artery resistance - and VR-VD - which are not preceded by a measurable increase in umbilical artery resistance and may be caused by fetal hypoxia.

Low frequency spontaneous fluctuations in tissue blood volume in neonates.

Low frequency spontaneous fluctuations in tissue blood volume (BV) which originate from the activity of the autonomic nervous system were studied in the toes of healthy adults and in the feet of preterm and full-term neonates. Fluctuations of cardiac-induced blood volume changes (AM) were also investigated using photoplethysmography, the measurement of changes in light absorption by tissue and its constituents. Both fluctuations showed right-left correlations, which indicates mediation of central origin. The average right-left correlation coefficient for adults was significantly higher than that for neonates, probably due to incomplete maturation of the autonomic nervous system for some of the neonates.

Fiber optic sensor for the measurement of respiratory chest circumference changes.

A fiber optic sensor for the measurement of the respiratory depth has been developed. The sensor is composed of a bent optic fiber which is connected to an elastic section of a chest belt so that its radius of curvature changes during respiration due to respiratory chest circumference changes (RCCC). The measurement of light transmission through the bent fiber provides information on its changes in curvature since a higher fraction of light escapes through the core-cladding surface of a fiber bent to a lower radius of curvature. The sensor can quantitatively measure the RCCC, although in relative terms, and it is sensitive enough to detect changes of the chest circumference due to the heart beat. Measurements of the RCCC were simultaneously performed with photoplethysmography (PPG)-the measurement by light absorption of the cardiac induced blood volume changes in the tissue-and a significant correlation was found between the RCCC and some parameters of the PPG signal. The fiber optic respiratory depth sensor enables a quantitative assessment of the respiratory induced changes in the cardiovascular parameters. © 1999 Society of Photo-Optical Instrumentation Engineers.

The variability of the photoplethysmographic signal--a potential method for the evaluation of the autonomic nervous system.

The heart rate variability is composed of low- and high-frequency fluctuations, which are mediated by the sympathetic and the parasympathetic nervous systems. The baseline and the amplitude of the photoplethysmographic (PPG) signal also show fluctuations in the same frequencies. In the current study, PPG examinations were performed on the fingers of normal subjects and diabetic patients, and three parameters were derived from each PPG pulse: the baseline of the pulse, its amplitude and its period (which is equal to the heart period). The level of the variability of each PPG pulse parameter was measured by the ratio of the standard deviation of the parameter to its mean value. The level of the low-frequency fluctuations for the PPG amplitude and for the heart cycle period did not differ between males and females, but was lower for diabetic patients, indicating lower activity of the autonomic nervous system. The curves of the baseline and the amplitude of the PPG signal for the non-diabetic subjects showed high correlation between the left and the right hands. For most of the diabetic patients the right-left correlation coefficients were significantly lower than those for the non-diabetic subjects. Our initial results have shown that the variability of the PPG parameters shows promise for the assessment of the function of the autonomic nervous system.

Sweet syndrome associated with G-CSF treatment in a child with glycogen storage disease type Ib.

Acute febrile neutrophilic dermatosis (Sweet syndrome) is rare in children and is regularly associated with underlying malignancies or inflammtory diseases. A 5-year-old girl with glycogen storage disease type Ib, neutropenia, and recurrent infections developed characteristic skin eruption of Sweet syndrome after 2 years of granulocyte colony-stimulating factor (G-CSF) therapy. This association points to a possible role of G-CSF-induced granulopoiesis and granulodyte activation in the pathogenesis of Sweet syndrome.

Vertical plane short and middle latency vestibular evoked potentials in humans.

In order to determine whether short and middle latency vestibular evoked potentials (VsEPs) can be recorded in humans in response to angular acceleration stimuli in the vertical plane, a drum, head-holder, and stepper motor were designed to deliver upward acceleration impulses of 10,000 degrees/s2 (1.8 degrees displacement) to the human head. Forehead and mastoid electrodes recorded electrical activity that was filtered, differentially amplified, and averaged in short (12.7 milliseconds) and middle (63.5 milliseconds) latency time frames. Control recordings were used to eliminate various types of artifact. Recordings were conducted in 7 normal subjects and in 4 control patients with congenital, profound hearing loss and absence of caloric responses. Short and middle latency VsEPs with high intrasubject and intersubject consistency were recorded in normal subjects and not in control patients. The middle latency responses were larger in amplitude than the short latency responses. The effects of stimulus intensity and repetition rate on VsEP waveform, latency, and amplitude studied. Experiments have shown that the responses are not electrical artifact, nor are they contaminated by auditory, somatosensory, or passive eye movement potentials.

Irradiation induced blood flow changes in the breast during radiotherapy--a pilot study.

Skin blood flow and underskin temperature were measured in breasts during the complementary radiotherapy following lumpectomy, using the noninvasive transient thermal clearance method. On average, blood flow and tissue temperature increased at the start of the irradiation then slightly decreased. The response varied significantly among the patients. The increase in blood flow is associated with the vasodilatation which accompanies irradiation-induced inflammation and the method enables the assessment of this vasodilatation during the irradiation treatment. The decrease of blood flow after the initial increase is attributed to vascular damage. The method provides a noninvasive means for the evaluation of radiation effects on individual patients during radiotherapy.

Acute haemorrhagic oedema of infancy, a benign variant of leucocytoclastic vasculitis.

Acute haemorrhagic oedema of infancy (AHEI) is an acute leucocytoclastic vasculitis affecting infants and young children. It has a striking appearance of large purpuric skin lesions in a target-like pattern and marked oedema mainly on the face, auricles and extremities. In some patients there is mucosal involvement as well. We present five patients with skin lesions characteristic of AHEI with no visceral involvement and complete resolution within 7-14 days. In three of our five cases, histopathological examination was performed, and demonstrated typical leucocytoclastic vasculitis. Although sometimes confused with Schönlein-Henoch purpura, we suggest that AHEI should be regarded as a separate entity. Clinical criteria for diagnosis are proposed.