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At least 361 records · Page 20Linked to original sources

PubMed2003

Increase in tear film lipid layer thickness following treatment with warm compresses in patients with meibomian gland dysfunction.

PURPOSE: Warm-compress therapy applied to the skin of the closed eyelids has been recommended as a treatment for meibomian gland dysfunction (MGD). Previous studies have evaluated the effects of warm-compress therapy on tear-film fluorescein break-up time and tear evaporation rate. The purpose of this study was to determine if tear-film lipid layer thickness (TFLLT) was altered following 5, 15, and 30 minutes of warm, moist compress therapy. METHODS: Twenty patients with a diagnosis of dry eye associated with MGD and a baseline TFLLT of <or= 90 nm (baseline difference between experimental and control eyes <or= 25 nm) were studied. The skin of the closed eyelids of one eye of each subject was treated for a total of 30 minutes with a compress saturated with warm (40.0 +/- 2.0 degrees C) water used as a compress; and the skin of the closed eyelids of the contralateral control eye was treated for a total of 30 minutes with a compress saturated with room-temperature (24.0 degrees C +/- 1.0 degrees C) water used as a compress. The subjects' eyes were randomized into experimental and control eyes. TFLLT was measured at the following time points: 5, 15, and 30 minutes during the 30-minute treatment period, and after 5 minutes following the 30-minute treatment period. RESULTS: The mean baseline TFLLT of the experimental eye prior to treatment with a warm, moist compress was 57.8 +/- 12.9 (standard error) nm; after 5 minutes of treatment, TFLLT was 105.8 +/- 23.7 nm; after 15 minutes of treatment, 117.8 +/- 26.4 nm; after 30 minutes of treatment, 121.5 +/- 27.1 nm; and after 5 minutes following the 30-minute treatment, 96.0 +/- 21.5 nm. The mean baseline TFLLT of the control eye prior to treatment with a room temperature, moist compress was 63.0 +/- 14.1 nm; after 5 minutes of treatment, TFLLT was 63.8 +/- 14.3 nm; after 15 minutes of treatment, 62.3 +/- 13.9 nm; after 30 minutes of treatment, 64.5 +/- 14.4 nm; and after 5 minutes following the 30-minute treatment period, 58.5 +/- 13.1 nm. Using a paired-data t-test, the results demonstrated a significant increase in mean TFLLT in the experimental eye after 5 minutes (P < 0.001), 15 minutes (P < 0.001), and 30 minutes (P < 0.001) of treatment, and after 5 minutes following the 30-minute treatment period (P < 0.001) when compared to baseline TFLLT. In comparison, there was no significant increase in TFLLT of the control eye after 5 minutes (P = 0.79), 15 minutes (P = 0.77), and 30 minutes (P = 0.81) of treatment, and after 5 minutes following the 30-minute treatment period (P = 0.20) when compared to baseline TFLLT. CONCLUSIONS: Warm, moist compress therapy applied to the skin of the closed eyelids increases TFLLT for subjects with MGD by more than 80%, 5 minutes after initiating treatment and an additional 20% after 15 minutes of treatment. This study supports clinical experience and previous reports on warm, moist compress therapy as an effective treatment for meibomian gland dysfunction.

Adult↗

PubMed1990

ECG data compression techniques--a unified approach.

A broad spectrum of techniques for electrocardiogram (ECG) data compression have been proposed during the last three decades. Such techniques have been vital in reducing the digital ECG data volume for storage and transmission. These techniques are essential to a wide variety of applications ranging from diagnostic to ambulatory ECG's. Due to the diverse procedures that have been employed, comparison of ECG compression methods is a major problem. Present evaluation methods preclude any direct comparison among existing ECG compression techniques. The main purpose of this paper is to address this issue and to establish a unified view of ECG compression techniques. ECG data compression schemes are presented in two major groups: direct data compression and transformation methods. The direct data compression techniques are: ECG differential pulse code modulation and entropy coding, AZTEC, Turning-point, CORTES, Fan and SAPA algorithms, peak-picking, and cycle-to-cycle compression methods. The transformation methods briefly presented, include: Fourier, Walsh, and K-L transforms. The theoretical basis behind the direct ECG data compression schemes are presented and classified into three categories: tolerance-comparison compression, differential pulse code modulation (DPCM), and entropy coding methods. The paper concludes with the presentation of a framework for evaluation and comparison of ECG compression schemes.

Algorithms↗

PubMed1999

Context-based lossless and near-lossless compression of EEG signals.

In this paper, we study compression techniques for electroencephalograph (EEG) signals. A variety of lossless compression techniques, including compress, gzip, bzip, shorten, and several predictive coding methods, are investigated and compared. The methods range from simple dictionary-based approaches to more sophisticated context modeling techniques. It is seen that compression ratios obtained by lossless compression are limited even with sophisticated context-based bias cancellation and activity-based conditional coding. Though lossy compression can yield significantly higher compression ratios while potentially preserving diagnostic accuracy, it is not usually employed due to legal concerns. Hence, we investigate a near-lossless compression technique that gives quantitative bounds on the errors introduced during compression. It is observed that such a technique gives significantly higher compression ratios (up to 3-bit/sample saving with less than 1% error). Compression results are reported for EEG's recorded under various clinical conditions.

Electroencephalography↗

PubMed2004

Effects of 5-HT2A receptor antagonist on blood flow in chronically compressed nerve roots.

Neurogenic intermittent claudication (NIC) can be caused by compression of the cauda equina by spinal stenosis and is a major clinical problem. A reduction of blood flow is an important mechanism for inducing NIC and may be caused by a vasoconstrictive effect mediated by the serotonin 5-HT2A receptor in chronic cauda equina compression lesions. This study assessed the effects of the 5-HT2A receptor antagonist on nerve vasculature in chronically compressed nerve roots. A plastic balloon was placed under the lamina of L7 and inflated to 10 mmHg and left for 1 week in several cauda equina compression models. All experimental animals received an acute administration of serotonin. One group received sarpogrelate hydrochloride (5-HT2A receptor antagonist: 5-HTRA) before administration of serotonin, and another group was administered 5-HTRA after administration of serotonin. Diameters and blood flow in the vasculature of S2 or S3 nerve roots were measured after injection of serotonin. In animals without compression of the cauda equina (sham), blood vessels contracted and the blood flow was reduced after administration of serotonin. In sham and compression animals receiving both serotonin and 5-HTRA, blood vessel diameter was not reduced and was significantly larger than that in the compression group receiving only serotonin (p<0.05). Likewise, the blood flow was not reduced in sham and compression animals receiving serotonin and 5-HTRA and was significantly greater in the compression group treated only with serotonin. 5-HTRA inhibited vasoconstriction and the reduction of blood flow in chronically compressed nerve roots challenged with serotonin. This fact suggests that 5-HTRA might be effective at improving blood flow in chronically compressed nerve roots in patients with spinal canal stenosis and changes in circulation levels of serotonin.

Animals↗

PubMedDate not supplied

The evolution of abdominal compression in cardiopulmonary resuscitation.

OBJECTIVE: To review the history of external abdominal compression as an adjunct to cardiopulmonary resuscitation (CPR), tracking the development of five major themes over the course of the 20th century: 1) augmentation of peripheral resistance by physical means, 2) risk of hepatic injury with abdominal compression, 3) counterpulsation vs sustained compression, 4) the abdominal pump mechanism, and 5) contact compression techniques. METHODS: Literature retrieved from successive MEDLINE English-language searches was received with a special emphasis on work and concepts highlighted by participants at the First Purdue Conference on Interposed Abdominal Compression-CPR, September 1992. RESULTS: External abdominal compression of one form or another has been studied as a means of resuscitation by many investigators throughout the 20th century. Experimental and clinical studies have shown generally consistent evidence of hemodynamic augmentation by abdominal compression during various forms of CPR. Recent advances include a modified theoretical understanding of hemodynamic mechanisms and demonstration of clinical potential in humans. Inconsistencies in published results may be due to differences in mechanical techniques of abdominal compression. Based on these studies, a modified manual technique for "contact compression" of the abdominal aorta is recommended. CONCLUSIONS: A technique for left-of-center, angled compression of the abdominal aorta against the crest of the spine is recommended. Further well-supervised and controlled clinical trials using this standardized technique are warranted as a prelude to more widespread clinical application of abdominal compression in CPR.

Abdomen↗

PubMed1995

Theoretically optimal duty cycles for chest and abdominal compression during external cardiopulmonary resuscitation.

OBJECTIVE: To use an electronic model of human circulation to compare the hemodynamic effects of different durations of chest compression during external CPR, both with and without interposed abdominal compression (IAC). METHODS: An electrical analog model of human circulation was studied on digital computer workstations using SPICE, a general-purpose circuit simulation program. In the model the heart and blood vessels were represented as resistive-capacitive networks, pressures as voltages, blood flow as electric current, blood inertia as inductance, and cardiac and venous valves as diodes. External pressurization of the heart and great vessels, as would occur in IAC-CPR, was simulated by the alternate application of damped rectangular voltage pulses, first between intrathoracic vascular capacitances and ground, and then between intra-abdominal vascular capacitances and ground. With this model compression frequencies of 60, 80, and 100 cycles/min and duty cycles ranging from 10% to 90%, both with and without IAC, were compared. RESULTS: There was little difference in hemodynamics when the overall compression frequency was varied between 60 and 100 cycles/min, but the effects of duty cycle were substantial. During both standard CPR and IAC-CPR, total flow and coronary flow were greatest at chest compression durations equal to 30% of cycle time. Interposed abdominal compression substantially improved simulated systemic blood flow and perfusion pressure at all duty cycles, compared with standard CPR without abdominal compression. Mean arterial pressure > 75 mm Hg and artificial cardiac output > 2.0 L/min could be generated by 30% duty cycle compression with IAC. Coronary perfusion in the model is clearly optimized at 30% chest compression (i.e., high-impulse chest compression technique). CONCLUSION: Combined high-impulse chest compressions and IACs maximize blood flow during CPR in the electrical analog model of human circulation.

Abdomen↗

PubMed1994

Reflex increase in blood pressure induced by leg compression in man.

1. We tested the hypotheses that the increase in mean arterial pressure with the application of external leg compression in man is (i) blocked with epidural anaesthesia, and (ii) dependent upon the level of external pressure applied, the quantity of leg muscle mass compressed and the vascular volume of the leg. Fourteen healthy subjects were fitted with an anti-shock trouser garment to provide three levels (30, 60 and 90 mmHg) of leg compression, while cephalad translocation of fluid was prevented by upper-thigh cuffs inflated to a supra-systolic pressure. Cardiovascular responses were recorded during leg compression before and after the administration of epidural anaesthesia in eight subjects, while blood pressure responses from six subjects were compared with their single leg pressor response. 2. Both mean arterial and diastolic pressures were elevated with increasing leg compression, with no changes in heart rate, cardiac output, thoracic impedance, and central venous pressure. The leg compression-induced blood pressure increases were abolished by epidural anaesthesia. Furthermore, when only one leg was compressed at 90 mmHg, the pressor response was less than that elicited from compression of both legs at the same external pressure. Changes in vascular volume of the leg did not influence the pressor response to leg compression. 3. The results indicate that the mean arterial pressure increases in response to external compression of the legs and that a reflex mechanism, mediated by muscle afferent nerves, is involved. The response is dependent upon both the changes in intramuscular pressure and the quantity of muscle mass compressed.

Adult↗

PubMed2005

Detection of simulated lesions on data-compressed digital mammograms.

PURPOSE: To evaluate retrospectively the effect of a wavelet-based compression method on the detection of simulated masses of various sizes and clustered microcalcifications on data-compressed digital mammograms. MATERIALS AND METHODS: The images used in this study were acquired with institutional review board approval and patient informed consent, both of which allowed subsequent image data analysis. Patient identification was removed from images, and the study complied with requirements of the Health Insurance Portability and Accountability Act. Masses 3, 6, and 8 mm in diameter were analytically simulated and added to clinical mammographic backgrounds. In addition, microcalcifications were extracted from a clinical mammogram and hybridized with simulated microcalcifications for use in this study. Image compression conditions of 1:1, 15:1, and 30:1 were investigated. Observer responses were recorded with a six-point rating scale, and receiver operating characteristic (ROC) analysis was performed. In addition, two well-established numeric observer models were used to study the effect of image compression under the same compression conditions as were used with human observers. Analysis of variance was performed after observer adjustment to compare the mean values for area under the ROC curve (A(z)) across the three compression levels for the masses and microcalcification clusters. RESULTS: The results of the study indicated no significant differences in the A(z) values for masses with the compression conditions investigated. For images of microcalcifications, there were significant differences in A(z) values between compression ratios of 1:1 and 30:1 (P = .0005) and of 15:1 and 30:1 (P = .004); the difference between compression ratios of 1:1 and 15:1 was nonsignificant (P = .053). The observer models and human observers exhibited similar trends in detection of the masses investigated in this study. CONCLUSION: Detection of simulated masses was not affected by the compression method with the conditions used in this study, while the detection of microcalcifications was significantly reduced with a compression ratio of more than 15:1.

Analysis of Variance↗

PubMed2006

High-performance wavelet compression for mammography: localization response operating characteristic evaluation.

PURPOSE: To evaluate the accuracy of a visually lossless, image-adaptive, wavelet-based compression method for achievement of high compression rates at mammography. MATERIALS AND METHODS: The study was approved by the institutional review board of the University of South Florida as a research study with existing medical records and was exempt from individual patient consent requirements. Patient identifiers were obliterated from all images. The study was HIPAA compliant. An algorithm based on scale-specific quantization of biorthogonal wavelet coefficients was developed for the compression of digitized mammograms with high spatial and dynamic resolution. The method was applied to 500 normal and abnormal mammograms from 278 patients who were 32-85 years old, 85 of whom had biopsy-proved cancer. Film images were digitized with a charge-coupled device-based digitizer. The original and compressed reconstructed images were evaluated in a localization response operating characteristic experiment involving three radiologists with 2-10 years of experience in reading mammograms. RESULTS: Compression rates in the range of 14:1 to 2051:1 were achieved, and the rates were dependent on the degree of parenchymal density and the type of breast structure. Ranges of the area under the receiver operating characteristic curve were 0.70-0.83 and 0.72-0.86 for original and compressed reconstructed mammograms, respectively. Ranges of the area under the localization response operating characteristic curve were 0.39-0.65 and 0.43-0.71 for original and compressed reconstructed mammograms, respectively. The localization accuracy increased an average of 6% (0.04 of 0.67) with the compressed mammograms. Localization performance differences were statistically significant with P = .05 and favored interpretation with the wavelet-compressed reconstructed images. CONCLUSION: The tested wavelet-based compression method proved to be an accurate approach for digitized mammography and yielded visually lossless high-rate compression and improved tumor localization.

Adult↗

PubMed2005

Chest compression rates during cardiopulmonary resuscitation are suboptimal: a prospective study during in-hospital cardiac arrest.

BACKGROUND: Recent data highlight a vital link between well-performed cardiopulmonary resuscitation (CPR) and survival after cardiac arrest; however, the quality of CPR as actually performed by trained healthcare providers is largely unknown. We sought to measure in-hospital chest compression rates and to determine compliance with published international guidelines. METHODS AND RESULTS: We developed and validated a handheld recording device to measure chest compression rate as a surrogate for CPR quality. A prospective observational study of adult cardiac arrests was performed at 3 hospitals from April 2002 to October 2003. Resuscitations were witnessed by trained observers using a customized personal digital assistant programmed to store the exact time of each chest compression, allowing offline calculation of compression rates at serial time points. In 97 arrests, data from 813 minutes during which chest compressions were delivered were analyzed in 30-second time segments. In 36.9% of the total number of segments, compression rates were <80 compressions per minute (cpm), and 21.7% had rates <70 cpm. Higher chest compression rates were significantly correlated with initial return of spontaneous circulation (mean chest compression rates for initial survivors and nonsurvivors, 90+/-17 and 79+/-18 cpm, respectively; P=0.0033). CONCLUSIONS: In-hospital chest compression rates were below published resuscitation recommendations, and suboptimal compression rates in our study correlated with poor return of spontaneous circulation. CPR quality is likely a critical determinant of survival after cardiac arrest, suggesting the need for routine measurement, monitoring, and feedback systems during actual resuscitation.

Aged↗

PubMed1999

Pressor response to compression of the ventrolateral medulla mediated by glutamate receptors.

The rostral ventrolateral medulla (RVLM) is considered a major center for the regulation of sympathetic and cardiovascular activities. Several clinical studies have indicated a possible causal relationship between neurovascular contact of the left RVLM and essential hypertension, and some investigators have suggested that the left RVLM is more sensitive to pulsatile compression than the right RVLM. Previously, we reported that pulsatile compression of the RVLM elevates arterial pressure by enhancing sympathetic outflow in rats; however, we have not investigated the laterality of the responses to the compression. In addition, it remains to be elucidated whether RVLM neurons are activated by compression and, if so, how they are activated. Therefore, we performed compression experiments in rats to investigate these issues. Pulsatile compression was performed on the unilateral RVLM with a pulsating probe in anesthetized and artificially ventilated rats. Pulsatile compression of the unilateral RVLM increased arterial pressure, heart rate, and sympathetic nerve activity. The pressor response to compression was inhibited significantly after local microinjection of glutamate receptor antagonists. Pulsatile compression of the RVLM increased Fos immunoreactivitiy, a marker of neuronal activation, within the nuclei of postsynaptic RVLM neurons. All results were observed symmetrically. The data indicate that the responses to pulsatile compression of the unilateral RVLM are similar on both sides. They also suggest that pulsatile compression of the RVLM increases sympathetic and cardiovascular activities by activating postsynaptic RVLM neurons through the stimulation of the local glutamate receptors in rats.

Animals↗

PubMed1995

Maximal expiratory flows generated by rapid chest compression following end-inspiratory occlusion or expiratory clamping in young children.

Partial forced expiratory flow-volume curves obtained by the rapid chest compression technique are being widely used to assess pulmonary function in infants and young children. The aim of this study is to assess whether in this age group flow limitation is achieved with the partial forced expiratory flow-volume curve with rapid chest compression. In eight infants and young children sedated with chloral hydrate, flow-volume curves were obtained by regular rapid chest compression technique, end-inspiratory airway occlusion prior to rapid chest compression, and expiratory clamping prior to rapid chest compression. In each technique, beginning with a cuff pressure of 20 cmH2O, the cuff pressure was increased by 10 cmH2O increments until the compression pressure reached 90 cmH2O. Maximal flow-volume curves were generated by each technique. End-inspiratory occlusion prior to rapid chest compression caused higher flows over the entire phase of expiration than the regular rapid chest compression. This increase could be observed over the entire phase of expiration. Forced expiratory flow at 50% and at 75% of vital capacity (V50 and V75) with regular rapid chest compression were 207 +/- 44 ml.s-1 (mean +/- SD) and 138 +/- 59 ml.sec-1, respectively. When end-inspiratory occlusion preceded rapid chest compression, V50 and V75 increased to 283 +/- 114 and 206 +/- 61 ml.sec-1 respectively, with a mean increase in V50 of 34% and in V75 of 31%. When expiratory clamping preceded the compression, even higher expiratory flows resulted.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗

PubMed1994

Application of wavelet compression to digitized radiographs.

OBJECTIVE: Image data compression is an enabling technology for teleradiology and picture archive and communication systems. Compression decreases the time and cost of image transmission and the requirements for image storage. Wavelets, discovered in 1987, constitute a new compression technique that has been described in radiologic publications but, to our knowledge, no previous studies of its use have been reported. The purpose of this study was to demonstrate the application of wavelet-based compression technology to digitized radiographs. MATERIALS AND METHODS: Twelve radiographs with abnormal findings were digitized, compressed, and decompressed by using a new wavelet-based lossy compression algorithm. Images were compressed at ratios from 10:1 to 60:1. Seven board-certified radiologists reviewed images on a two-headed, high-resolution (2K x 2K) diagnostic workstation. Paired original and compressed/decompressed images were presented in random order. Reviewers adjusted contrast and magnification to judge whether image degradation was present, and if so, whether it was of diagnostic significance. Quantitative error measures were tabulated. RESULTS: Reviewers found no clinically relevant degradation below a compression ratio of 30:1. Skeletal radiographs appeared more sensitive to compression than did chest or abdominal radiographs, but the trend was not statistically significant. Quantitative error measures increased gradually with compression ratio. CONCLUSION: On the basis of subjective assessment of image quality and the computational efficiency of the algorithm, wavelet-base techniques appear promising for the compression of digitized radiographs. The results of this initial experience can be used to design appropriate observer performance studies.

Adult↗

PubMed2003

Quantitative assessment of diffusion abnormalities in benign and malignant vertebral compression fractures by line scan diffusion-weighted imaging.

OBJECTIVE: Acute vertebral collapse is common, and it is sometimes difficult to determine whether the cause is benign or malignant. Recently, diffusion-weighted imaging has been reported to be useful for differentiating the two types. The purpose of this study was to evaluate diffusion abnormalities quantitatively in benign and malignant compression fractures using line scan diffusion-weighted imaging. SUBJECTS AND METHODS. Line scan diffusion-weighted imaging was prospectively performed in 17 patients with 20 acute vertebral compression fractures caused by osteoporosis or trauma, in 12 patients with 16 vertebral compression fractures caused by malignant tumors, and in 35 patients with 47 metastatic vertebrae without collapse. Images were obtained at b values of 5 and 1,000 sec/mm(2). The apparent diffusion coefficient (ADC) was measured in vertebral compression fractures and metastatic vertebrae without collapse. RESULTS: The ADC (mean +/- SD) was 1.21 +/- 0.17 x 10(-3) mm(2)/sec in benign compression fractures, 0.92 +/- 0.20 x 10(-3) mm(2)/sec in malignant compression fractures, and 0.83 +/- 0.17 x 10(-3) mm(2)/sec in metastatic vertebral lesions without collapse. The ADC was significantly higher in benign compression fractures than in malignant compression fractures (p < 0.01), although the two types showed considerable overlap. CONCLUSION: Although the quantitative assessment of vertebral diffusion provides additional information concerning compressed vertebrae, the benign and malignant compression fracture ADC values overlap considerably. Therefore, even a quantitative vertebral diffusion assessment may not always permit a clear distinction between benign and malignant compression fractures.

Aged↗

PubMed1997

[The effect on bowel sounds of very hot compresses applied to the lumbar region].

In Japan, very hot moist compresses applied to the lumbar region have been used to promote intestinal movement and flatus or defecation. This skill was based on empirical knowledge. One of the purposes of this study is to make clear the effect of very hot compresses on intestinal movement. The other purpose is to prove the safety of the skin where very hot compresses applied. The sample consisted of 8 healthy female volunteers, ranging in age from 27 to 47 with a mean age of 37.4. A very hot compress was applied to the lumbar region for 10 minutes. The results were as follows: 1) Bowel sounds immediately after hot compresses increased 1.7 times compared with bowel sounds before the hot compresses. 2) Skin temperature of the back increased to 41.1-43.1 degrees centigrade under the hot compresses, then decreased rapidly. 3) Blood flow to the back during hot compresses, increased to 156%. Blood flow to the upper arm also increased. 4) Body temperature, pulse rate and blood pressure were not remarkably changed by the hot compresses. The results of the experiments show that very hot compresses applied to the lumbar region affect intestinal movement. And the results suggest that a very hot compress is a useful nursing skill to promote flatus or defecation.

Adult↗

PubMed2001

[Evaluation of diagnostic accuracy of CRT monitor display for personal computer in the detection of small lung nodules: with particular emphasis on comparison between JPEG and wavelet compression].

PURPOSE: To compare observer performance on cathode-ray-tube(CRT) monitors for personal computers with that on conventional radiographs in the detection of small lung nodules. MATERIALS AND METHODS: Fifty-eight normal chest radiographs and 58 chest radiographs with a small lung nodule were selected. Ten radiologists examined the original conventional films on a viewbox and digitized (8 bit) uncompressed and compressed images of the same patient on a color CRT monitor with a matrix of 1,600 x 1,200, and rated the presence of lung nodules with a five-level scale of confidence. The methods of compression used in this study were the JPEG and wavelet methods, with compression ratios of 6:1 and 15:1. Results were analyzed by receiver operating characteristic methods. RESULTS: There was no significant difference between film and digitized uncompressed and compressed images obtained by the JPEG and wavelet methods with a compression ratio of 6:1. No statistically significant difference was detected between film and digitized image with wavelet compression at 15:1. However, detection was less accurate on digitized images with JPEG compression at 15:1. CONCLUSION: Digitized (8 bit) uncompressed and compressed images with a compression ratio of 6:1 are acceptable for the detection of small lung nodules. Digitized compressed images at a compression ratio of 15:1 are also acceptable when the wavelet method is used.

Data Display↗

PubMed1992

Mechanical enhancement and myocardial oxygen saving by synchronized dynamic left ventricular compression.

Dynamic cardiomyoplasty with synchronously paced skeletal muscle grafts has recently been developed to augment the performance of impaired myocardium. This method has been reported effective to improve patients' general status and some hemodynamic parameters. It is unknown, however, how a systolic dynamic cardiac compression, as in dynamic cardiomyoplasty, affects left ventricular energetics. The purpose of this study was to characterize the effects of dynamic cardiac compression on the ventricle in terms of the pressure-volume relationship and myocardial oxygen consumption. In an isolated cross-circulated dog heart model, a dynamic cardiac compression device was set to directly compress the ventricle during systole. End-systolic pressure, contractility index (Emax), pressure-volume area, external mechanical work, coronary blood flow, and myocardial oxygen consumption were determined before and during dynamic cardiac compression. Dynamic cardiac compression significantly increased Emax. When end-diastolic and stroke volumes were fixed, end-systolic pressure, pressure-volume area, and external mechanical work significantly increased during dynamic cardiac compression while coronary blood flow and myocardial oxygen consumption remained unchanged. When end-systolic pressure was matched with the pre-dynamic cardiac compression control level by decreasing end-diastolic volume at a constant stroke volume so that external mechanical work under dynamic cardiac compression returned to the control level, both pressure-volume area and myocardial oxygen consumption significantly decreased. In contrast to a marked increase in myocardial oxygen consumption for a given increase in external mechanical work by either volume loading or dobutamine, dynamic cardiac compression did not increase myocardial oxygen consumption for the same increase in external mechanical work. Thus dynamic cardiac compression augments left ventricular pump function without increasing myocardial oxygen demand or compromising coronary blood flow.

Animals↗

PubMed1993

The effects of ice and compression wraps on intramuscular temperatures at various depths.

While ice and compression wraps are commonly used to treat musculoskeletal injuries, the literature describing intramuscular temperatures has not addressed the combination of ice and compression wraps. The purpose of this study was to evaluate intramuscular temperatures at three sites on the anterior thigh (skin surface, 1 cm below the fat layer, and 2 cm below the fat layer) using both ice and compression wraps. Temperatures were recorded in 11 subjects with an isothermex, using implantable and surface thermocouples. Each subject was tested under four conditions: control, compression only, ice only, and ice + compression according to a balanced Latin square. Surface and intramuscular temperatures were recorded at 30 second intervals during 5 minutes of preapplication, 30 minutes application, and 20 minutes postapplication. A repeated measures ANOVA and Duncan post hoc tests were used to evaluate peak temperature differences between the treatment conditions and the depths of measurement. Both ice alone and ice + compression produced significant cooling at all three depths (F(6,60) = 168.5, p<.0005). Likewise, during the 20-minute postapplication period, these temperatures did not return to their preapplication levels. The compression-only condition produced significant warming at the skin surface, but did not have any effect on intramuscular temperature. At all depths, the ice + compression condition produced significantly cooler temperatures than ice alone. We suggest that compression increases the effectiveness of ice in reducing tissue temperatures. Therefore, ice combined with compression should be more effective than ice alone in reducing the metabolism of injured tissue. This provides an additional rationale for combining ice with compression in treating acute musculoskeletal injuries.

Journal Article↗