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PubMed2005

Changes of calcitonin gene-related peptide in primary sensory neurons and their central branch after nerve root compression of the dog.

OBJECTIVE: To investigate changes in axonal flow after nerve root compression by using immunohistochemical techniques to detect calcitonin gene-related peptide (CGRP), which is thought to be involved in pain sensation. DESIGN: Experimental, controlled study. SETTING: University medical school in Japan. ANIMALS: Forty adult mongrel dogs (weight, 7-15kg). INTERVENTIONS: In dogs, the lumbar nerve roots were compressed using 4 types of clips with different pressures. Changes of CGRP levels in the spinal dorsal horn, dorsal root, and dorsal root ganglia (DRG) were examined immunohistochemically after compression for 24 hours or for 1 week. MAIN OUTCOME MEASURES: CGRP-positive neurons and CGRP-positive fibers. RESULTS: After compression, axonal flow in the dorsal root was impaired, accumulation of CGRP was observed distal to the site of compression, and the number of DRG cells showing positively for CGRP decreased. Compression for 1 week resulted in a decrease in the number of CGRP-positive fibers in the spinal dorsal horn. CONCLUSIONS: These findings indicate that CGRP dynamics are modified by nerve compression.

Animals↗

PubMed2004

A model for sedimentation in inhomogeneous media. II. Compressibility of aqueous and organic solvents.

The effects of solvent compressibility on the sedimentation behavior of macromolecules as observed in analytical ultracentrifugation are examined. Expressions for the density and pressure distributions in the solution column are derived and combined with the finite element solution of the Lamm equation in inhomogeneous media to predict the macromolecular concentration distributions under different conditions. Independently, analytical expressions are derived for the sedimentation of non-diffusing particles in the limit of low compressibility. Both models are quantitatively consistent and predict solvent compressibility to result in a reduction of the sedimentation rate along the solution column and a continuous accumulation of solutes in the plateau region. For both organic and aqueous solvents, the calculated deviations from the sedimentation in incompressible media can be very large and substantially above the measurement error. Assuming conventional configurations used for sedimentation velocity experiments in analytical ultracentrifugation, neglect of the compressibility of water leads to systematic errors underestimating sedimentation coefficients by approximately 1% at a rotor speeds of 45000 rpm, but increasing to 2-5% with increasing rotor speeds and decreasing macromolecular size. The proposed finite element solution of the Lamm equation can be used to take solvent compressibility quantitatively into account in direct boundary models for discrete species, sedimentation coefficient distributions or molar mass distributions. Using the analytical expressions for the sedimentation of non-diffusing particles, the ls-g*(s) distribution of apparent sedimentation coefficients is extended to the analysis of sedimentation in compressible solvents. The consideration of solvent compressibility is highly relevant not only when using organic solvents, but also in aqueous solvents when precise sedimentation coefficients are needed, for example, for hydrodynamic modeling.

Centrifugation, Density Gradient↗

PubMed2004

The study of diagnostic accuracy of chest nodules by using different compression methods.

BACKGROUND: The purpose of this study was to compare the diagnostic accuracy of small nodules in the chest by using different compression methods. METHOD: Two radiologists with 5 years experience twice interpreted 39 chest images by using lossless and lossy compression methods. The time interval was 3 weeks. Each time the radiologists interpreted one kind of compressed images. The image browser used the Unisight software provided by Atlastiger Company in Shanghai. The interpreting results were analyzed by the ROCKIT software and the ROC curves were painted by Excel 2002. RESULTS: In studies of receiver operating characteristics for scoring the presence or absence of nodules, the images with lossy compression method showed no statistical difference as compared with the images with lossless compression method. CONCLUSION: The diagnostic accuracy of chest nodules by using the lossless and lossy compression methods had no significant difference, we could use the lossy compression method to transmit and archive the chest images with nodules.

Algorithms↗

PubMed2005

The influence of superficial venous surgery and compression on incompetent calf perforators in chronic venous leg ulceration.

OBJECTIVES: Previous studies have suggested that perforating vein incompetence is reduced by surgery to superficial veins. This study analysed the effect in a randomised clinical trial. DESIGN: Retrospective analysis of duplex data. METHODS: Patients in this study were part of the ESCHAR randomised controlled trial. All patients had chronic venous leg ulceration with superficial venous reflux. Patients were treated with compression bandaging alone or compression plus superficial venous surgery. Legs were assessed using colour venous duplex prior to treatment and at 3 and 12 months. RESULTS: Of 500 patients recruited to the ESCHAR trial, 261 were included in this study. One hundred and forty six of 261 legs were treated with compression alone and 115/261 underwent compression and superficial venous surgery. In the compression group, more legs had incompetent perforators at 12 months (77/131) compared to baseline (61/146, p =0.010, Wilcoxon Signed Ranks test for paired data in 131 legs). Following surgery, significantly fewer legs had incompetent calf perforators (59/115 vs 44/104 at 12 months, p =0.001, Wilcoxon Signed Ranks test for paired data in 104 legs). In addition, significantly fewer legs in the compression and surgery group developed new perforator incompetence in comparison to the group treated with compression alone (12/104 vs 36/131, p =0.003, Chi-Squared test). CONCLUSION: Surgical correction of superficial reflux may abolish incompetence in some calf perforators and offer protection against developing new perforator incompetence.

Bandages↗

PubMed2006

Human hoppers compensate for simultaneous changes in surface compression and damping.

On a range of elastic and damped surfaces, human hoppers and runners adjust leg mechanics to maintain similar spring-like mechanics of the leg and surface combination. In a previous study of adaptations to damped surfaces, we changed surface damping and stiffness simultaneously to maintain constant surface compression. The current study investigated whether hoppers maintain spring-like mechanics of the leg-surface combination when surface damping alone changes (elastic and 1000-4800 N s m(-1)). We found that hoppers adjusted leg mechanics to maintain similar spring-like mechanics of the leg-surface combination and center of mass dynamics on all surfaces. Over the range of surface damping, vertical stiffness of the leg-surface combination increased by only 12% and center of mass displacement decreased by only 6% despite up to 55% less compression of more heavily damped surfaces. In contrast, a simulation predicted a 44% decrease in vertical displacement with no adjustment to leg mechanics. To compensate for the smaller and slower compression of more heavily damped surfaces, the stance legs compressed by up to 4.1 +/- 0.2 cm further and reached peak compression sooner. To replace energy lost by damped surfaces, hoppers performed additional leg work by extending the legs during takeoff by up to 3.1 +/- 0.2 cm further than they compressed during landing. We conclude that humans simultaneously adjust leg compression magnitude and timing, as well as mechanical work output, to conserve center of mass dynamics on damped surfaces. Runners may use similar strategies on natural energy-dissipating surfaces such as sand, mud and snow.

Adult↗

PubMed2004

The structural adaptations in compressed articular cartilage by microscopic MRI (microMRI) T(2) anisotropy.

OBJECTIVES: To detect structural adaptations of collagen fiber matrix in compressed articular cartilage in individual sub-tissue zones by microscopic magnetic resonance imaging (microMRI) at 23 microm in-depth resolution. DESIGN: Each of the six beagle humeral cartilage specimens was placed in a specially built nonmetallic compression device inside an in-situ rotation device, and was imaged four times at 7T: without and during static compression, and at two orientations: 0 degrees and 55 degrees . Proton intensity images and quantitative T(2) maps were constructed and analyzed. RESULTS: Upon compression at 55 degrees (the magic angle), rather than appearing homogenous, T(2)-weighted intensity images of cartilage showed a distinct laminar appearance and the T(2) profiles exhibited two distinctive peaks. At both 0 degrees and 55 degrees orientations, lower values of T(2) were observed in compressed tissue. A significant correlation was established between changes in tissue T(2) at 55 degrees and a thickness reduction due to compression. At a mean of 20% strain value, modifications in cartilage structure were studied at each histological zone. We found that the percentage of superficial zone was significantly doubled, the percentage of radial zone was significantly decreased by 10%, and no significant change in the transitional zone. CONCLUSIONS: External loading can induce a new kind of laminar appearance at the magic angle. microMRI T(2) anisotropy can be used to analyze the zone-specific alterations in collagen fibril organization in articular cartilage in response to mechanical compression.

Adaptation, Physiological↗

PubMed2005

Prestrain decreases cartilage susceptibility to injury by ramp compression in vitro.

BACKGROUND: Injurious mechanical loading of articular cartilage can be an initiating factor in the development of degenerative joint disease. The tissue response to compression depends on the loading conditions and matrix mechanical properties. The short-term loading history of cartilage can affect its water content and microstructural organization, and may thereby modify its susceptibility to injury. We therefore examined the role of prestrain on the response of articular cartilage to injurious compression. METHODS: The full-thickness cartilage of bovine osteochondral explants was subjected to prestrains of 0, 5, 10, 25 or 50% before application of injurious ramp compression characterized by a strain rate of 7x10(-2) or 7x10(-3)s-1 and peak stress of 3.5 or 14 MPa. Effects of prestrain were evaluated in terms of fluid exudation, tissue mechanical stiffening, and the tissue response to injurious compression as characterized by macroscopic crack formation, cell viability and glycosaminoglycan release to culture media. RESULTS: Macroscopic crack formation due to injurious compression decreased with increasing prestrain in association with lower cell mortality. Significantly decreased susceptibility to injury was already evident for 10% prestrain. In contrast, explant mechanical stiffness was unchanged up to 25% prestrain. CONCLUSION: Findings demonstrate that compressive strains due to the short-term loading history of cartilage may strongly reduce its susceptibility to mechanical injury. Conversely, matrix swelling may render cartilage more vulnerable to injury. The cartilage response to injurious compression is therefore strongly influenced by matrix fluid content, and possibly also by other structural parameters such as collagen fiber orientation.

Animals↗

PubMed2006

Prevention of recurrence of venous ulceration: randomized controlled trial of class 2 and class 3 elastic compression.

OBJECTIVE: To compare venous ulcer recurrence and compliance with two strengths of compression hosiery. METHODS: This study was a randomized controlled trial with a 5-year follow-up. The setting was the leg ulcer clinics of a teaching and a district general hospital in Scotland, United Kingdom. Patients were 300 outpatients with recently healed venous ulcers, with no significant arterial disease, rheumatoid disease, or diabetes mellitus. Interventions were fitting and supply of class 2 or class 3 compression hosiery. Four-monthly refitting by trained orthotists and surveillance by specialist nurses were performed. The main outcome measures were recurrence of leg ulceration and compliance with treatment. RESULTS: Thirty-six percent (107/300) of patients had recurrent leg ulceration by 5 years. Recurrence occurred in 59 (39%) of 151 class 2 elastic compression cases and in 48 (32%) of class 3 compression cases. One hundred six patients did not comply with their randomized compression class, 63 (42%) in class 3 and 43 (28%) in class 2. The difference in recurrence is not statistically significant, but our estimate of the effectiveness of class 3 hosiery is diluted by the lower compliance rate in this group. Restricted ankle movement and four or more previous ulcers were associated with a higher risk of recurrence. CONCLUSIONS: There was no evidence of a difference in recurrence rates at the classic level of significance (5%), but the lowest recurrence rates were seen in people who wore the highest degree of compression. Therefore, patients should wear the highest level of compression that is comfortable.

Adult↗

PubMed2004

The influence of cyclic compression and distraction on the healing of experimental tibial fractures.

Interfragmentary displacement has a main effect on callus formation in fracture healing. To test whether compressive or distractive displacements have a more pronounced effect on new bone formation, a sheep osteotomy model was created whereby the gap tissue was subjected to constant bending displacement. A diaphyseal osteotomy with a gap of 2 mm was created in 18 sheep tibiae and stabilized with a special unilateral actuator-driven external fixator. Two experimental groups with six sheep each received either 10 or 1000 cycles evenly distributed over 24 h. The third group of six sheep served as a control group without actively induced displacement. The amount and direction of cyclic displacement was kept constant throughout the observation period, resulting in 50% compressive and 50% distractive displacement within the osteotomy gap. At sacrifice, six weeks after surgery, bending stiffness was measured and new bone formation was assessed radiologically and microradiographically. In all cycled groups, the amount of periosteal callus formation was up to 25 times greater on the compression compared to the distraction side (p < 0.001). The application of the higher number of daily cycles resulted in an up to 10-fold greater amount of periosteal new bone formation on the compression side (p < 0.012), while the difference on the distraction side was not significant. Ten cycles applied a day were sufficient to create an abundant periosteal callus on the compression side. In the 1000 cycle group, bending stiffness revealed slightly lower values but the difference was not significant. Solid periosteal bridging of the gap was observed in two sheep in the control group, whereas bridging in the cycled groups was observed exclusively at the medullary side. In conclusion, cyclic compressive displacements were found to be superior over distractive displacements. A higher number of enforced and maintained compressive displacements enhanced periosteal callus formation but did not allow bony bridging of the gap.

Animals↗

PubMed2005

A comparison of CPR delivery with various compression-to-ventilation ratios during two-rescuer CPR.

BACKGROUND: The number of chest compressions required for optimal generation of coronary perfusion pressure remains unknown although studies examining compression-to-ventilation ratios higher than 15:2 (C:V) in animals have reported higher C:V to be superior for return of spontaneous circulation and neurologic outcome. We examined human performance of two-rescuer CPR using various C:V. METHODS: Thirty six EMT-Basic students in their final week of training performed two-rescuer CPR using C:V of 15:2, 30:2, 40:2, 50:2, and 60:2 on a recording resuscitation manikin. Compression and ventilation variables were recorded by computer while the number of pauses for ventilations and the hands-off time (time not spent performing chest compressions) were abstracted by hand. Data were analyzed by ANOVA and significant differences from the standard treatment of C:V = 15:2 were assessed by Tukey's HSD post hoc test. FINDINGS: The number of compressions delivered per minute increased with increasing C:V while the hands-off time and pauses for ventilations decreased. All comparisons were significantly different from C:V = 15:2 (P < 0.001). The ventilation numbers decreased with increasing C:V although mean minute volume exceeded 1l for all C:V. INTERPRETATION: A 15:2 compression-to-ventilation ratio when performed during two-rescuer CPR results in 26s of hands off time each minute while only delivering 60 compressions. Alternative C:V ratios of 30:2, 40:2, 50:2, and 60:2 all exceed the AHA recommended 80 compressions/min while still delivering a minute volume in excess of 1l.

Cardiopulmonary Resuscitation↗

PubMed1999

Compression of the central airways by a dilated aorta in infants and children with congenital heart disease.

BACKGROUND: Children with congenital heart disease often experience respiratory symptoms in the preoperative and perioperative periods, which can complicate their management. An uncommon but important cause of respiratory insufficiency in such children is external airway compression. METHODS: We operated on 5 patients (median age, 6 months) with significant respiratory distress attributable to compression of the central airways by a dilated ascending aorta before or after repair of concomitant cardiovascular defects. Four of these patients had right aortic arch and 3 had pulmonary atresia with a ventricular septal defect and major aortopulmonary collaterals. In all patients, aortopexy was performed at the time of operation for the cardiovascular defects (n = 3) or after symptoms developed in the postoperative period (n = 2). The 3 patients in whom airway compression produced symptoms preoperatively also underwent reduction ascending aortoplasty. RESULTS: Symptoms resolved immediately after operation in 3 patients, whereas symptoms persisted in the other 2 patients and tracheostomy was required. At follow-up of 20 months to 5 years, all patients are alive and well, with mild or moderate respiratory symptoms in the 2 patients who required tracheostomy, both of whom were decannulated within 13 months. CONCLUSIONS: External airway compression can cause significant morbidity in patients with congenital heart defects other than vascular rings. In patients with respiratory symptoms in the context of a lesion that involves increased aortic outflow during intrauterine life and consequently, an enlarged ascending aorta, such as tetralogy of Fallot with pulmonary atresia, airway compression should be considered as a cause, especially if a right aortic arch is present or the patient also has pulmonary atresia with a ventricular septal defect and collaterals. Attempts to address this problem surgically may provide substantial relief, but increasing duration of airway compression is likely to lead to tracheal or bronchial malacia and persistent symptoms even after the compression is relieved.

Airway Obstruction↗

PubMed1985

Critical dependence of calcium-activated force on width in highly compressed skinned fibers of the frog.

Force development by skinned frog semitendinosus fibers was studied at various levels of lateral compression to compare the results with intact fibers and to evaluate the limits on cross-bridge movements during isometric contraction. The skinned fibers were compressed osmotically using a high molecular weight polymer, dextran T500. Ca-activated force remained constant down to 58% of the fiber width (w0) after skinning, corresponding to a nearly twofold change in separation between the thin and thick filaments in the myofilament lattice. This agrees with the earlier result on intact fibers, and gives additional evidence that the cross-bridge mechanism for force generation is relatively insensitive to large changes in interfilament separation. Further compression, below 0.58 w0, produced a sharp drop in force, and the force was practically zero at a fiber width of 50%. The effect at high compression was the same at all pCa's, which indicates that the Ca sensitivity of the myofilaments is unaffected by radial compression. The stiffness of the fiber remained high in rigor in the presence of dextran, which indicates that the rigor cross-bridge attachment is not inhibited, and actually may be improved, with decreases in the interfilament space. Also, the drop in active force with the highest compression was similar when the compressed fibers were put in rigor before contraction, which suggests that the force drop also was not due to a hindrance to cross-bridge attachment. The results appear to exclude large motions such as tilting and rocking of the bridge as a rigid molecule, but suggest that at least some molecular movement is essential for force development; they also raise the possibility that there is a critical interfilament separation in the fiber, below which the cross-bridge cannot function.

Animals↗

PubMed1998

Confined compression of articular cartilage: linearity in ramp and sinusoidal tests and the importance of interdigitation and incomplete confinement.

Experimental and theoretical methods were used to investigate the linearity of the stress response of articular cartilage to ramp and sinusoidal tests in confined compression, as well as the role of cartilage-porous platen and lateral confinement boundary conditions in determining material responses. With respect to linearity, we posed the question as to whether the elicited stress responses to ramp compression, ramp release and sinusoidal tests were similar. With respect to boundary conditions we inquired as to the necessity of specifying a detailed interdigitating contact with the porous filter and of specifying the level of confinement present at the lateral edge of the disk. We found that the stress responses to the three types of tests were dissimilar, with ramp compression the only test exhibiting linear behavior. Ramp release from a static compression offset was non-linear in a manner such that the cartilage maintained a compressive stress higher than expected by a linear theory. Sinusoidal compression also displayed a non-linear response consistent with the presence of a release phase in each cycle. The actual boundary conditions present at the cartilage/porous-filter interface were visualized histologically. Areas (tens of microns) of cartilage in contact with the metal of the filter were interspersed with areas expanded into the pores of the filter. Finite-element analysis incorporating this information suggested that precise specification of this interface and of the level of the extent of lateral confinement would be necessary for the estimation of material properties, such as the hydraulic permeability, from these tests. The trends of the linearity studies did not appear to be significantly affected by the problems posed by these difficult to quantitate boundary conditions. The non-linear cartilage response to release and sinusoidal displacements therefore appear to be physiologically interesting. The maintained, that is higher than would be linear, compressive stress observed during release may be a beneficial adaptation to repeated loading where temporal variations in tissue stresses would be minimized.

Animals↗

PubMed1996

Determinants of success of color-flow duplex-guided compression repair of femoral pseudoaneurysms.

BACKGROUND: Ultrasonography-guided compression repair is reported to be effective therapy for femoral pseudoaneurysms that develop after catheterization procedures. This study summarizes our experience with color-flow duplex-guided repair of these lesions. METHODS: A retrospective chart review of all patients who underwent this procedure was undertaken, with statistical analysis to identify factors associated with success. RESULTS: Compression repair of 69 pseudoaneurysms was attempted. Pseudoaneurysms developed after therapeutic catheterization in 48 patients and after diagnostic procedures in 21. Sites of arterial puncture were the common femoral artery in 59 patients and the superficial femoral or profunda femoris arteries in 10. Diameters of the pseudoaneurysms ranged from 3 to 60 mm (mean, 28 mm). Compression was attempted at a mean of 5 days (range, 1 to 21 days) after catheterization. Compression produced complete thrombosis of the pseudoaneurysm at the initial attempt in 43 (62%) of 69 patients. With repeated attempts the ultimate success was 47 (68%) of 69. Success was achieved in 44 (75%) of 59 common femoral pseudoaneurysms but in only 3 (30%) of 10 superficial femoral or profunda femoris lesions (p = 0.009). Anticoagulation, sheath size, pseudoaneurysm chamber size, and time between catheterization and compression were not significantly different between lesions that were successfully compressed and those that were not. No ischemic or embolic complications were observed. CONCLUSIONS: Color-flow duplex-guided compression repair can be safely attempted as the initial therapy for all uncomplicated pseudoaneurysms arising from the common femoral artery after catheterization, with the expectation of success in most.

Adult↗

PubMed1996

Comparison of leg compression stocking and oral horse-chestnut seed extract therapy in patients with chronic venous insufficiency.

BACKGROUND: Diseases of the venous system are widespread disorders sometimes associated with modern civilisation and are among the major concerns of social and occupational medicine. This study was carried out to compare the efficacy (oedema reduction) and safety of compression stockings class II and dried horse chestnut seed extract (HCSE, 50 mg aescin, twice daily). METHODS: Equivalence of both therapies was examined in a novel hierarchical statistical design in 240 patients with chronic venous insufficiency. Patients were treated over a period of 12 weeks in a randomised, partially blinded, placebo-controlled, parallel study design. FINDINGS: Lower leg volume of the more severely affected limb decreased on average by 43.8 mL (n = 95) with HCSE and 46.7 mL (n = 99) with compression therapy, while it increased by 9.8 mL with placebo (n = 46) after 12 weeks therapy for the intention-to-treat group (95% CI: HCSE: 21.1-66.4; compression: 30.4-63.0; placebo: 40.0-20.4). Significant oedema reductions were achieved by HCSE (p = 0.005) and compression (p = 0.002) compared to placebo, and the two therapies were shown to be equivalent (p = 0.001); in this design, however, compression could not be proven as standard with regard to oedema reduction in the statistical test procedure. Both HCSE and compression therapy were well tolerated and no serious treatment-related events were reported. INTERPRETATION: These results indicate that compression stocking therapy and HCSE therapy are alternative therapies for the effective treatment of patients with oedema resulting from chronic venous insufficiency.

Bandages↗

PubMed2000

Isostatic compression, a new process for incorporating vancomycin into biphasic calcium phosphate: comparison with a classical method.

Isostatic compression has rarely been used to load calcium-phosphate biomaterials with therapeutic agents. This report, concerning four processes associating vancomycin, compares isostatic compression with wet granulation, a classical method. In the wet granulation study, vancomycin was associated with biphasic calcium-phosphate (BCP) granules either by adsorption or incorporation with a new granulation. In the isostatic compression study, BCP powder was compressed at 100, 140 and 200 MPa. The blocks obtained were crushed and 200-500 microm, sieved; thus, the vancomycin solution was absorbed on these granules. Compaction of BCP and vancomycin powders gave, after crushing and sieving, granules loaded with vancomycin. In each study, 5% vancomycin was associated with BCP. Vancomycin release profiles were assessed by an in vitro culture chamber dissolution test. Physicochemical studies of BCP and vancomycin showed their structural integrity after isostatic compression. Isostatic compression prolonged vancomycin release time from 3 to 7 days and the release time became greater as isostatic pressure increased, probably because of the porosity decrease of the granules during compression.

Calcium Phosphates↗

PubMed1997

Impact of various compression rates on interpretation of digital coronary angiograms.

According to the ACC/ACR/NEMA/ESC-guidelines, digital techniques should be replaced by cinefilm for coronary angiography. The ad hoc group of experts recently chose CD-R (CD recordable) as transport media and the JPEG standard for image compression. To avoid a possible loss of image quality, the guidelines allow a maximal data compression of only 2:1. This, however, leads to a considerable limitation: coronary angiograms cannot be viewed in real-time directly from CD. Since the possible influence of higher compression rates on image quality of coronary angiograms had not been investigated in a controlled study, we evaluated 8 various compression rates (ranging from 5:1 to 43:1) according to a prospective, randomized and blinded protocol. Four independent observers assessed 1440 angiograms using a semiquantitative score. We found that angiograms with a compression rate of 5:1 and 6:1 did not lead to a clinically relevant deterioration of image quality, whereas 11:1 was still acceptable, but 43:1 becomes unacceptable. Since no clinically relevant loss of information at a compression rate of 6:1 was experienced in our study, a modification of the ACC/ACJ/NEMA/ESC-guidelines allowing higher compression rates should be considered.

Angiography, Digital Subtraction↗

PubMed1993

Two-thumb versus two-finger chest compression during CRP in a swine infant model of cardiac arrest.

STUDY OBJECTIVE: To test the hypothesis that two-thumb chest compression generates higher arterial and coronary perfusion pressures than the current American Heart Association-approved two-finger method. DESIGN: Randomized, crossover experimental trial. SETTING AND PARTICIPANTS: Animal laboratory experiment with seven swine of either sex weighing 9.4 kg (SD, 0.8 kg), representing infants less than 1 year old. INTERVENTIONS: Animals were sedated with IM ketamine/xylazine, intubated with a 6.0 Hi-Lo endotracheal tube, anesthetized with alpha-chloralose, and paralyzed with pancuronium. ECG was monitored continuously. Left femoral arterial and Swan-Ganz catheters were placed. Cardiac arrest was induced with an IV bolus of KCl and verified by ECG and pressure tracings. Five American Heart Association-certified basic rescuers were randomly assigned to perform external chest compressions for one minute by either the currently recommended two-finger method or the two-thumb and thorax-squeeze method. After all five completed their first trial, rescuers crossed over to the other method for a second minute of compressions. Ventilation was performed with a bag-valve device, and no drugs were given during CPR. After three complete cycles, the fourth through sixth cycles of compressions were recorded. Every compression was analyzed for arterial systolic, diastolic, mean, and coronary perfusion pressures. One thousand fifty compressions were analyzed with repeated-measures analysis of variance and Scheffé multiple comparisons. RESULTS: Systolic blood pressure, diastolic blood pressure, mean arterial pressure, and coronary perfusion pressure were all significantly higher (P < .001) with the two-thumb thoracic squeeze technique: systolic blood pressure, 59.4 versus 41.6 mm Hg; diastolic blood pressure, 21.8 versus 18.5 mm Hg; mean arterial pressure, 34.2 versus 26.1 mm Hg; and coronary perfusion pressure, 15.1 versus 12.2 mm Hg. CONCLUSION: The two-thumb method of chest compression generates significantly higher arterial and coronary perfusion pressures than the two-finger method in this infant model of cardiac arrest.

Animals↗