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PubMed1993

Interposed abdominal compression-CPR: a case study in cardiac arrest research.

When the abdomen is compressed manually in counterpoint to the rhythm of chest compression, in the performance of interposed abdominal compression-CPR, artificial circulation is approximately doubled in animal experiments and in electronic models of the circulatory system. These studies suggest that external manual compression of the abdominal aorta acts like an intra-aortic balloon pump to increase aortic pressure, whereas external manual compression of the abdominal veins acts to prime the right heart and pulmonary vessels before the next chest compression. As a result, perfusion pressures and flows are increased. Several clinical studies of this technique have shown promising results including improved hemodynamics, resuscitation success, and survival. The history of interposed abdominal compression-CPR research suggests a number of principles that may be useful in the development of other new methods for the management of cardiac arrest, including the virtues of vigorously pursuing a new idea suggested by serendipitous observations, developing and refining a working hypothesis as to pathophysiologic mechanisms, working in interdisciplinary groups, refining a novel technique in stages as experience is gained, and recognizing the need for staged phase 1, 2, and 3 clinical trials in the context of the approximately ten-year gestation period from laboratory inspiration to clinical practice.

Abdomen↗

PubMed2001

Precordial compression without airway management induces lung injury in the rodent cardiac arrest model with central apnea.

To investigate whether the lung injury induced by precordial compression without ventilation or not, in the cardiac-arrest animal model with central apnea. Thirty male Sprague-Dawley rats were anesthetized with halothane. The cardiac arrest was induced by 100 mg/kg ketamine (IV) and accompanied with central apnea. They were allocated to four groups by means of resuscitation. Group A was treated with only precordial compression without the other treatments. In group B with tracheotomy and precordial compression. In group C was performed tracheotomy, oxygenation, and precordial compression. The animals in group D were treated with tracheotomy, oxygen administration, artificial ventilation, and precordial compression. Four minutes after cardiac arrest, the resuscitation was started and continued for 20 min. PaCO(2) in the group without mechanical ventilation increased significantly after the start of the resuscitation. All animals were sacrificed after resuscitation procedure. The wet/dry weight ratio of lung in group A (6.9+/-0.8) was significantly higher than that of the other groups B, C and D (5.9+/-0.6, 5.7+/-0.4 and 5.6+/-0.4, P<0.05 in each). The pathological findings also demonstrated the lung injuries, such as edema, migration, and destruction of structure in group A. The precordial compression alone did not improve CO(2) elimination in the gasping-less cardiac arrest model, as well as maybe inducing more severe lung injury than that with the protective management. This experimental model raises the possibility that chest compressions without airway management might result in lung injury.

Animals↗

PubMed2002

Does the compression to ventilation ratio affect the quality of CPR: a simulation study.

Experience has shown that better quality CPR leads to a greater chance of a patient surviving a cardiac arrest. Simple CPR techniques, such as using only chest compressions, lead to better skill retention and greater willingness to attempt resuscitation on strangers. However, it is not clear from clinical or experimental studies whether such techniques offer any physiological benefit over more usual 5:1 or 15:2 compression:ventilation ratios. Computer simulations of blood flow and gas exchange during CPR showed that continuous chest compressions produced much greater blood flow (1.39 l/min) than 5:1 (0.73 l/min), 15:2 (0.86 l/min) or 50:5 (0.94 l/min) ratios. However, the ratio of 5:1 produced the highest arterial oxygen levels, with continuous chest compressions the lowest. The most appropriate measure of CPR efficiency appears to be the amount of oxygen delivered to the body during CPR. The ratios of 15:2 and 50:5 produced significantly greater oxygen delivery to the body than 5:1, the greater blood flow with these techniques offsetting the slightly lower arterial oxygen levels. The best oxygen delivery was provided by continuous chest compression in the early stages of CPR. After 3-4 min however, hypoxia meant that continuous compressions became worse than the other techniques. Spontaneous gasping by the patient during CPR was able to extend the effectiveness of chest compression only CPR for much longer.

Blood Gas Analysis↗

PubMed1997

Quality of mechanical, manual standard and active compression-decompression CPR on the arrest site and during transport in a manikin model.

The quality of mechanical CPR (M-CPR) was compared with manual standard CPR (S-CPR) and active compression-decompression CPR (ACD-CPR) performed by paramedics on the site of a cardiac arrest and during manual and ambulance transport. Each technique was performed 12 times on manikins using teams from a group of 12 paramedic students with good clinical CPR experience using a random cross-over design. Except for some lost ventilations the CPR effort using the mechanical device adhered to the European Resuscitation Council guidelines, with an added time requirement of median 40 s for attaching the device compared with manual standard CPR. Throughout the study, in comparison with mechanical CPR the quality of CPR with either manual method was significantly worse. In particular, there were considerable individual variations during stretcher transport. With S-CPR and ACD-CPR the median compression times were 38 and 31%, significantly lower than the recommended 50%, and 46-98% of the decompression efforts with ACD-CPR were too weak, particularly during transport on the stairs. With both manual methods, there were no significant differences in the CPR effort between the site of the arrest and the ambulance transport. However, compression rates were reduced and became more erratic during stretcher transport to the ambulance. When walking horizontally, a median of 19% of S-CPR compressions and 84% of ACD-CPR compressions were to weak. On the stairs, 68% of S-CPR compressions and 100% of ACD-CPR compressions were too weak. In conclusion, when evaluated on a manikin, in comparison with manual standard and ACD-CPR, mechanical CPR adhered more closely to ERC guidelines. This was particularly true when performing CPR during transport on a stretcher.

Cardiopulmonary Resuscitation↗

PubMed1998

Effect of different compression--decompression cycles on haemodynamics during ACD-CPR in pigs.

The haemodynamic effects of variations in the relative duration of the compression and active decompression (4 cm/2 cm) during active compression-decompression cardiopulmonary resuscitation (ACD-CPR), 30/70, 50/50 and 70/30, were tested in a randomized cross-over design during ventricular fibrillation in seven anaesthetized pigs (17-23 kg) using an automatic hydraulic chest compression-decompression device. Duty cycles of 50/50 and 70/30 gave significantly higher values than 30/70 for mean carotid blood flow (32 and 36 vs. 21 ml min-1, transit time flow probe, cerebral blood flow (30 and 34 vs. 19, radionuclide microspheres), mean aortic pressure (35 and 41 vs. 29 mmHg) and mean right atrial pressure (24 and 33 vs. 16 mmHg). A higher mean aortic, mean right atrial and mean left ventricular pressure for 70/30 were the only significant differences between 50/50 and 70/30. There were no differences in myocardial blood flow (radionuclide microspheres) or coronary perfusion pressure (CPP, aortic-right atrial pressure) between the three different duty cycles. CPP was positive in both the early and late compression period and during the whole decompression period. The expired CO2 was significantly higher with 70/30 than 30/70 during the compression phase of ACD-CPR. Beyond that no significant differences in the expired CO2 levels were observed. In conclusion a reduction of the compression period to 30% during ACD-CPR reduced the cerebral circulation, the mean aortic and right atrial pressures with no effect on the myocardial blood flow of varying the compression-decompression cycle.

Animals↗

PubMed1998

The study of the effectiveness of chest compressions using the CPR-plus.

Effective cardiopulmonary resuscitation (CPR) requires a high level of skill from both healthcare professionals and the lay public. Inadequate chest compressions are a common cause of ineffective CPR. The CPR-plus is a non-invasive, hand-held, simple to use CPR adjunct designed to assist the rescuer to monitor and modify the compression technique during CPR, hopefully resulting in improved rescuer performance and more effective CPR. Forty qualified nurses were evaluated while they performed chest compressions on a training manikin. During simulated two-rescuer CPR (compression/ventilation ratio 5:1) the participants performed 150 compressions at a rate of 80-100 min. Compressions were performed with and without the CPR-plus and the results compared. The use of the CPR-plus was randomised with regard to whether the adjunct or the standard method was used first. The average number of correctly applied compressions was significantly better when the CPR-plus was used: 138.35/150 versus 110.70/150 (p = 0.0001). Improvements in techniques associated with the use of the CPR-plus also included a reduction in excessive application of pressure and incorrect hand position. The device provided reassurance of satisfactory compressions and an indication of impending fatigue in the rescuer.

Cardiopulmonary Resuscitation↗

PubMed2003

Compensation of log-compressed images for 3-D ultrasound.

In this study, a Bayesian approach was used for 3-D reconstruction in the presence of multiplicative noise and nonlinear compression of the ultrasound (US) data. Ultrasound images are often considered as being corrupted by multiplicative noise (speckle). Several statistical models have been developed to represent the US data. However, commercial US equipment performs a nonlinear image compression that reduces the dynamic range of the US signal for visualization purposes. This operation changes the distribution of the image pixels, preventing a straightforward application of the models. In this paper, the nonlinear compression is explicitly modeled and considered in the reconstruction process, where the speckle noise present in the radio frequency (RF) US data is modeled with a Rayleigh distribution. The results obtained by considering the compression of the US data are then compared with those obtained assuming no compression. It is shown that the estimation performed using the nonlinear log-compression model leads to better results than those obtained with the Rayleigh reconstruction method. The proposed algorithm is tested with synthetic and real data and the results are discussed. The results have shown an improvement in the reconstruction results when the compression operation is included in the image formation model, leading to sharper images with enhanced anatomical details.

Algorithms↗

PubMed2001

Vascular complications after percutaneous coronary interventions following hemostasis with manual compression versus arteriotomy closure devices.

OBJECTIVES: We evaluated the vascular complications after hemostasis with arteriotomy closure devices (ACD) versus manual compression after percutaneous coronary interventions (PCI). BACKGROUND: Previous clinical studies have indicated that ACD can be used for achievement of hemostasis and early ambulation after PCI. This study investigated the safety of ACD in achieving hemostasis after PCI compared with manual compression in a large cohort of consecutive patients. METHODS: A total of 5,093 patients were followed after PCI was performed with the transfemoral approach. Univariate and multivariate analysis were used to identify the predictors of vascular complications with ACD (n = 516) or with manual compression (n = 5,892) as a hemostasis option after sheath removal. RESULTS: The use of ACD was associated with a more frequent occurrence of hematoma compared with manual compression (9.3 vs. 5.1%, p < 0.001). There was also a higher rate of significant hematocrit drop (>15%) with ACD versus manual compression (5.2% vs. 2.5%, p < 0.001). Similar rates of pseudoaneurysm and arteriovenous fistulae were noted with either hemostasis technique. Vascular surgical repair at the access site was required more often with ACD versus manual compression (2.5 vs. 1.5%, p = 0.03). CONCLUSIONS: In this early experience with ACD after PCI, their use was associated with higher vascular complication rates than hemostasis with manual compression.

Aged↗

PubMed2001

The effect of dynamic compression on the response of articular cartilage to insulin-like growth factor-I.

Articular cartilage is routinely subjected to mechanical forces and to cell-regulatory molecules. Previous studies have shown that mechanical stimuli can influence articular chondrocyte metabolic activity, and biochemical studies have shown that growth factors and cytokines control many of the same cell functions. Little is known, however, of the relationships or interplay, if any, between these two key components of the articular environment. This study investigated the comparative and interactive effects of low amplitude, sinusoidal, dynamic compression and insulin-like growth factor-I (IGF-I), a polypeptide in synovial fluid that is anabolic for cartilage. In bovine patellofemoral cartilage explants, IGF-I increased protein and proteoglycan synthesis 90% and 120%, respectively while dynamic compression increased protein and proteoglycan synthesis 40% and 90%, respectively. Stimulation by IGF-I was significantly greater than by dynamic compression for both protein and proteoglycan synthesis. When applied together, the two stimuli enhanced protein and proteoglycan synthesis by 180% and 290%, respectively, a degree greater than that achieved by either stimulus alone. IGF-I augmented protein synthesis with a time constant of 12.2 h. Dynamic compression increased protein synthesis with a time constant of 2.9 h, a rate significantly faster than that of IGF-I, suggesting that these signals act via distinct cell activation pathways. When used together, dynamic compression and IGF-I acted with a time constant of 5.6 h. Thus, dynamic compression accelerated the biosynthetic response to IGF-I and increased transport of IGF-I into the articular cartilage matrix, suggesting that, in addition to independently stimulating articular chondrocytes, cyclic compression may improve the access of soluble growth factors to these relatively isolated cells.

Animals↗

PubMed2002

Static and dynamic compression modulate matrix metabolism in tissue engineered cartilage.

Static and dynamic compression are known to modulate the metabolism of articular cartilage. The present study focused on determining the effects of compressive loading on the metabolism of sulfated glycosaminoglycans (S-GAG) and protein in tissue engineered cartilage constructs. Cartilage constructs were subjected to static or dynamic compression for 24 h and radiolabeled with 35SO4 and 3H-proline to assess the total synthesis and percentage retention of S-GAG and total protein, respectively. Static compression at an amplitude of 50% suppressed the synthesis of both S-GAG and protein by 35% and 57%, respectively. Dynamic compression at an amplitude of 5% had stimulatory effects on synthesis that were dependent on the static offset compression amplitude (10% or 50%) and dynamic compression frequency (0.001 or 0.1 Hz). Thus, tissue engineered cartilage demonstrated the ability to respond to mechanical loading in a manner similar to that observed with articular cartilage. Mechanical loading may therefore potentially be used to modulate the growth of cartilaginous tissues in vitrd, potentially facilitating the culture of functional cartilage tissues suitable for implantation.

Animals↗

PubMed2002

Effect of mechanical compression on the vascular permeability of the dorsal root ganglion.

The dorsal root ganglion contains primary sensory neurons and is closely related to low back pain and sciatia. The present study investigated whether endoneurial edema, which is involved in the onset of pain and nerve dysfunction, was increased in the dorsal root ganglion by compression. The influence of mechanical compression on the vascular permeability of the lumbar dorsal root ganglion was determined. The dorsal root ganglion is reported to have a higher vascular permeability compared with other nerve tissues as well as lacking a blood-nerve barrier. However, only a few studies have assessed the influence of mechanical compression on the dorsal root ganglion. especially its vascular permeability. In dogs, laminectomy was performed at L7 and the dorsal root ganglion of the seventh lumbar spinal nerve was compressed for 1 h using four kinds of clips with various strengths. After clip removal, Evans blue albumin (EBA) or horseradish peroxidase (HRP) was administered intravenously as a tracer. After sacrifice, the EBA-injected specimens were observed by fluorescence microscopy and the HRP-injected specimens were observed by light and transmission electron microscopy. After compression of the dorsal root ganglion at 15 gf or more, leakage of tracer into the endoneurial space was markedly increased compared with the sham-operated group and severe edema was noted. Extravascular leakage of tracer was obvious around venules and capillaries. Electron microscopy showed an increase of extravascular HRP in the gap junctions and fenestrae between endothelial cells due to increased vascular permeability. However, the dorsal root ganglion was covered with a thick perineurium and HRP that leaked from the blood vessels did not enter the epineurium even after compression at 60 gf. It was proven that the increased vascular permeability occurred as well as in leakage of dye within the dorsal root ganglion after a single hour of compression of the dorsal root ganglion.

Animals↗

PubMed1999

Sequential foot compression reduces lower limb swelling and pain after total knee arthroplasty.

Two common prophylactic measures to prevent deep vein thrombosis (DVT) in patients after orthopedic lower limb surgeries are pneumatic foot and calf compression and antithrombotic treatment. These preventive measures differ in their mechanisms of operation. Antithrombotic agents are aimed to minimize the risk of clot formation, whereas pneumatic foot and calf compression therapy prevents venous stasis, which is a primary factor leading to thrombus formation in patients with leg trauma. DVT, however, is not the only consequence of patient immobility and venous stasis. Additional sequelae of venous stasis include lower limb swelling and pain resulting from the increase in venous pressures and change of normal compartmental circulatory pressures. We therefore hypothesized in the present study that antithrombotic treatment alone is not as effective as combined with pneumatic foot compression in reducing limb swelling and pain. Forty-eight patients after total knee arthroplasty participated in this randomized, controlled study. Low-molecular-weight heparin was the prophylactic measure used for the control group, whereas the pneumatic compression group received low-molecular-weight heparin and foot compression therapy for approximately 7 days after surgery. Lower limb swelling and pain were significantly reduced for the foot compression group in relation to the control group. Ultrasound and venography demonstrated no significant DVT in either group. We conclude that foot compression therapy is an important prophylactic addition to antithrombotic treatment in overcoming the hazardous clinical implications of venous stasis.

Aged↗

PubMed1999

Thromboembolic disease prophylaxis in total knee arthroplasty using intraoperative heparin and postoperative pneumatic foot compression.

A prospective study was performed to assess the clinical efficacy of intraoperative heparin combined with postoperative pneumatic foot compression and aspirin for thromboembolic disease prophylaxis after primary total knee arthroplasty (TKA). This group of 48 patients all had a primary TKA performed under epidural anesthesia. The cohort of patients was compared with a similar cohort of patients matched for age and comorbidity. The control group consisted of 61 patients (41 unilateral patients, 20 bilateral patients) with 81 TKAs who received epidural anesthesia and postoperative pneumatic foot compression and aspirin. The same surgeon and anesthesiologist performed all cases. All patients had the pneumatic foot compression device applied in the recovery room and received 325 mg of enteric-coated aspirin twice a day beginning the night of surgery. Venography was performed on the fifth postoperative day for both groups to determine the incidence of deep vein thrombosis (DVT). In the control group with postoperative pneumatic foot compression (group 1), the overall incidence of DVT was 27% (22 of 81), with 10% (8 of 81) major calf DVT and no proximal (popliteal or femoral) DVT. In the study group with intraoperative heparin and postoperative pneumatic foot compression (group 2), the overall incidence of DVT was 25% (12 of 48), with 8% (4 of 48) major calf DVT and no proximal DVT. There was no statistically significant difference between groups 1 and 2 for the incidence of overall DVT (P > .05) or major calf DVT (P > .05). No complications were associated with the use of intraoperative heparin or the pneumatic compression device, and no patient developed a symptomatic pulmonary embolism up to 3 months postoperatively. Although this study confirms that pneumatic foot compression combined with aspirin is an effective form of DVT prophylaxis after TKA, the added benefit of intraoperative heparin was not statistically proven. Although greater statistical power is needed to determine whether intraoperative heparin provides an added benefit, this study reveals a low incidence of DVT in TKA with this protocol.

Anticoagulants↗

PubMedDate not supplied

JPEG compression of digital echocardiographic images: impact on image quality.

Routine echocardiograms are not handled digitally because of enormous storage needs. Image compression techniques can reduce memory requirements, but the impact on diagnostic content is unknown. We studied the effect of an internationally accepted compression algorithm called Joint Photographic Experts Group (JPEG) on digital echocardiographic images. Diagnostic and image quality of JPEG compressed, two-dimensional echocardiograms at ratios ranging from 4:1 to 40:1 was compared with that of uncompressed images both subjectively by a blinded expert panel (540 observations) and objectively by quantitative image-processing parameters (180 images). Accuracy of 432 measurements performed on compressed M-mode and spectral Doppler tracings was determined. Simultaneously acquired videotaped images and their never-compressed digital counterparts were compared quantitatively for image fidelity. This study demonstrates that the JPEG compression algorithm produces little degradation of echocardiographic images at compression ratios of at least 20:1, with less measured distortion than is produced by videotape recording. With JPEG, digital storage and retrieval in routine echocardiography are feasible.

Algorithms↗

PubMed2000

Applying computer-assisted detection schemes to digitized mammograms after JPEG data compression: an assessment.

RATIONALE AND OBJECTIVES: The authors' purpose was to assess the effects of Joint Photographic Experts Group (JPEG) image data compression on the performance of computer-assisted detection (CAD) schemes for the detection of masses and microcalcification clusters on digitized mammograms. MATERIALS AND METHODS: This study included 952 mammograms that were digitized and compressed with a JPEG-compatible image-compression scheme. A CAD scheme, previously developed in the authors' laboratory and optimized for noncompressed images, was applied to reconstructed images after compression at five levels. The performance was compared with that obtained with the original noncompressed digitized images. RESULTS: For mass detection, there were no significant differences in performance between noncompressed and compressed images for true-positive regions (P = .25) or false-positive regions (P = .40). In all six modes the scheme identified 80% of masses with less than one false-positive region per image. For the detection of microcalcification clusters, there was significant performance degradation (P < .001) at all compression levels. Detection sensitivity was reduced by 4%-10% as compression ratios increased from 17:1 to 62:1. At the same time, the false-positive detection rate was increased by 91%-140%. CONCLUSION: The JPEG algorithm did not adversely affect the performance of the CAD scheme for detecting masses, but it did significantly affect the detection of microcalcification clusters.

Algorithms↗

PubMed1995

Effects of compression and type of bed surface on the microcirculation of the heel.

OBJECTIVE: To assess the effects of compression on the skin microcirculation of the heel using laser Doppler fluxmetry. DESIGN: Parallel groups comparing patients with control groups. SETTING: Department of Surgery, University College London Medical School, London. SUBJECTS AND MATERIALS: Ten patients at risk of developing pressure ulceration, 10 age- and sex-matched healthy subjects and 10 young, healthy volunteers. An acrylic indenter with a slot to accommodate a laser Doppler probe was used to apply compression to the heel region. A pressure sensor was used to measure the applied compression. OUTCOME MEASURES: The resting laser Doppler flux was measured with the subject lying supine. Compression forces were then applied in increments from 50 g to 1500 g and the corresponding interface pressure (IP) and laser Doppler flux (LDF) recorded. The IP and LDF were also measured from the heel while the subject was lying on a low air-loss system and then on an NHS conventional hospital bed. RESULTS: The resting LDF is lower in the patient group compared to the control groups (p < 0.05). Compression of the heel caused a progressive decrease in LDF in all groups. Compression greater than 50 mmHg as well as lying on an NHS bed reduced the LDF signal to a minimal value (biological zero). On the low air-loss system, the median LDF was 17% of the resting value in the age-matched control group and 32% in the patient group. CONCLUSIONS: The results indicate that the heel microcirculation is vulnerable to compression. The low air-loss system maintained the IP sufficiently low to prevent complete cessation of the heel microcirculation.

Adult↗

PubMed1999

Joint Photographic Experts Group compression of intraoral radiographs for image transmission on the World Wide Web.

OBJECTIVE: The purpose of this study was to evaluate the subjective quality of Joint Photographic Experts Group (JPEG) compressed images of intraoral radiographs with file sizes of 30 kilobytes or less, which can be transmitted quickly on the World Wide Web. STUDY DESIGN: Conventional intraoral radiographs were digitized at sampling rates of 100, 200, 300, 400, and 600 dots per inch through use of a flatbed scanner and saved in JPEG format in 11 compression degrees. Fifty-five combinations of sampling rate and compression degree were evaluated by means of a visual analog scale. Sampling rate and compression degree combinations whose quality was inferior to that of an average image were excluded. The quality of the remaining combinations was subsequently evaluated through assessment of 8 anatomical features in each image. RESULTS: Forty of the 55 combinations provided a file size less than 30 kilobytes. Thirty combinations obtained VAS scores of 0 or higher on the standardized VAS. As a result, 16 combinations of sampling and compression conditions were selected for the second part of the study. Only one combination of sampling rate and compression degree was found to provide sufficient image quality for all 8 anatomical features. CONCLUSIONS: Under the file size limit of the study design, the full-sized compressed image of an intraoral radiograph did not always provide sufficient quality. This problem will be reduced by improvements in telecommunications infrastructure, which will permit faster transfer of files of larger size.

Algorithms↗

PubMed2002

An effective coding technique for the compression of one-dimensional signals using wavelet transforms.

This paper introduces an effective technique for the compression of one-dimensional signals using wavelet transforms. It is based on generating a binary stream of 1s and 0s that encodes the wavelet coefficients structure (i.e., encodes the locations of zero and nonzero coefficients). A new coding algorithm, similar to the run length encoding, has been developed for the compression of the binary stream. The compression performances of the technique are measured using compression ratio (CR) and percent root-mean square difference (PRD) measures. To assess the technique properly we have evaluated the effect of signal length, threshold levels selection and wavelet filters on the quality of the reconstructed signal. The effect of finite word length representation on the compression ratio and PRD is also discussed. The technique is tested for the compression of normal and abnormal electrocardiogram (ECG) signals. The performance parameters of the proposed coding algorithm are measured and compression ratios of 19:1 and 45:1 with PRDs of 1% and 2.8% are achieved, respectively. At the receiver end, the received signal is decoded and inverse transformed before being processed. Finally, the merits and demerits of the technique are discussed.

Algorithms↗