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PubMed1982

Effectiveness of leg compression in preventing venous stasis.

To compare the ability of intermittent calf compression with that of sequential leg compression to prevent venous stasis, the clearance time of radiopaque dye, as determined by sequential phleborheograms performed on anesthetized patients, were compared. Calf compression was superior to no compression in clearing the dye from the calf alone, but did not aid clearance from the rest of the leg. Sequential leg compression was superior to intermittent calf compression in clearing dye from the calf and popliteal areas. Since intermittent leg compression has been as effective as small-dose heparin therapy in preventing postoperative deep venous thrombosis [7], the use of sequential leg compression may prove to be more effective and have less complication than heparin administration.

Humans↗

PubMed1996

Spinal compression at peak isometric and isokinetic exertions in simulated lifting in symmetric and asymmetric planes.

OBJECTIVE: To determine if the spinal compression can be used as a criterion for the safety of the back. DESIGN: Various lifting strength activities were analysed using a 3-D biomechanical model to determine spinal compression forces. BACKGROUND: Despite many standards being set and the use of varied strategies, low-back injuries continue to be common in our society. Since the injuries occur to the tissues in the body, it may be more appropriate to investigate the effects of external loads on the tissues. Therefore it was decided to determine the spinal compression in standardized lifting tasks. METHODS: Twenty young adults (12 males and 8 females) performed maximal stoop and squat lifts in sagittal, 30 degrees lateral, and 60 degrees lateral planes at half, three-quarters, and full horizontal reach distances. The stoop lifts were performed in isokinetic and isometric modes; the isometric mode was performed with the hip at 60 degrees and 90 degrees. The squat lifts were also performed in isokinetic and isometric modes; the isometric mode consisted of postures with knee at 90 degrees and 135 degrees of flexion. In addition, the subjects also performed isometric lifts in stoop and squat postures at a self-selected optimum posture. During these activities the strength was measured using a static dynamic strength tester employing a load cell and force monitor. Three-dimensional postural recording was made using a 3-D Peak Performance Technologies imaging system. Using the postural and force data as input to a 3-D biomechanical model, the lumbosacral spinal compression was calculated. The values of strength and spinal compression were analysed and compared. RESULTS: The strength was significantly affected by the gender, the type of lift, plane of lift and reach of lift (P < 0.01); whereas the spinal compression was not affected by the reach at all. Two-way and three-way interactions were significant for strength (P < 0.02) but not for spinal compression. CONCLUSION: It was concluded that the spinal compression was the ultimate cost function in the safety of the back and as such preventative strategies should be based on this. RELEVANCE: The use of an appropriate cost function in a manner in which it can maximize the safety of the back will be of considerable value. Since injuries are biomechanical perturbation of the tissues, it is argued that the cost function be used in a manner where tissue load be considered as the primary factor.

Journal Article↗

PubMed1994

Ventilation caused by external chest compression is unable to sustain effective gas exchange during CPR: a comparison with mechanical ventilation.

OBJECTIVE: To compare the tidal volume, minute ventilation, and gas exchange caused by mechanical chest compression with and without mechanical ventilatory support during cardiopulmonary resuscitation (CPR) in a laboratory model of cardiac arrest. DESIGN: A laboratory swine model of CPR was used. Eight animals with and eight animals without mechanical ventilation received chest compression (100/min) for 10 min. Coronary perfusion pressure, tidal volume, and minute ventilation were recorded continuously. INTERVENTIONS: Ventricular fibrillation for 6 min without CPR, then mechanical chest compression for 10 min. RESULTS: During the first minute of chest compression, mean (+/- S.D.) minute ventilation was 11.2 +/- 5.9 l/min in the mechanically ventilated group and 4.5 +/- 2.8 l/min in the group without mechanical ventilation (P = 0.01). Minute ventilation gradually declined to 5.8 +/- 1.4 l/min and 1.7 +/- 1.6 l/min, respectively, during the last minute of chest compression (P < 0.0001). After 10 min of chest compression, mean arterial pH was significantly more acidemic in the group without mechanical ventilation (7.16 +/- 0.13 compared with 7.30 +/- 0.07 units) and PCO2 was higher (62 +/- 19 compared with 35 +/- 9 mmHg). Mixed venous PCO2 was also higher (76 +/- 15 compared with 61 +/- 8 mmHg). CONCLUSION: Standard chest compression alone produced measurable tidal volume and minute ventilation. However, after 10 min of chest compression following 6 min of untreated ventricular fibrillation, it failed to sustain pulmonary gas exchange as indicated by significantly greater arterial and mixed venous hypercarbic acidosis when compared with a group receiving mechanical ventilation.

Acid-Base Equilibrium↗

PubMed2004

Likelihood of left main coronary artery compression based on pulmonary trunk diameter in patients with pulmonary hypertension.

PURPOSE: In patients with pulmonary hypertension, extrinsic compression of the left main coronary artery by a dilated pulmonary trunk may cause angina, left ventricular ischemia, and sudden death. We assessed coronary artery compression in relation to pulmonary trunk diameter and other demographic, echocardiographic, hemodynamic, and scintigraphic variables. METHODS: Thirty-six patients (aged 15 to 86 years) with pulmonary hypertension, either idiopathic or associated with congenital heart disease, were enrolled. Left main coronary artery compression was defined angiographically as > or =50% obstruction associated with downward displacement of the vessel. Pulmonary trunk and aortic diameters were measured by transthoracic echocardiography. RESULTS: Twenty-six patients had angina, of whom 7 had left coronary artery compression. Compression was related to pulmonary trunk diameter (P = 0.002) and to the ratio of pulmonary trunk diameter to aortic diameter (P = 0.02). Compression was not seen at pulmonary artery diameters <40 mm; among 19 patients with values > or =40 mm, the rate was 37%. Similarly, compression did not occur at pulmonary trunk to aortic diameter ratios <1.21; among 27 patients with ratios > or =1.21, the rate was 26%. CONCLUSION: In pulmonary hypertension, noninvasive measurement of pulmonary trunk diameter may be helpful in determining the likelihood of left coronary artery compression and in selecting patients for diagnostic coronary angiography.

Adolescent↗

PubMed2006

Local fluorouracil chemotherapy interferes with neural and behavioral recovery after brain tumor-like mass compression.

In this study, we investigated the impact of intracerebral delivery of chemotherapy on functional recovery from focal cortical tissue displacement, characteristic of brain tumors. Unilateral focal brain compression was induced by epidural implantation of an inverted hemisphere-shaped bead over the sensorimotor cortex. Microinjections of a total of 1mg chemoagent fluorouracil or the same volume of saline were made into the compressed cortex. Behavioral tests of forelimb sensorimotor function were conducted during 4 weeks' observation. Rats subjected to any of the three types of lesions, saline microinjection plus cortical compression, chemoagent microinjection alone, or chemoagent microinjection combined with cortical compression, demonstrated significant behavioral deficits in several sensorimotor tasks, compared with saline-microinjected control animals. In placing tests, behavioral deficits elicited by each single treatment were worsened by combined treatment with chemoagent microinjection and focal cortical compression. Concurrently, local delivery of chemoagent into the compressed cortex induced increased cortical tissue loss, necrosis and apoptosis. These data indicate that local chemotherapy exacerbates compression-induced neurological impairment, and a model of controlled focal cortical compression may provide a valuable means to improve anti-cancer therapeutic designs with reduced deterioration of brain function.

Animals↗

PubMed2004

Computed tomography findings in 10 cases of iliac vein compression (May-Thurner) syndrome.

OBJECTIVE: To present the computed tomography (CT) findings for the iliac veins of 10 patients who had left-sided lower extremity deep vein thrombosis due to iliac vein compression syndrome. MATERIALS AND METHODS: The CT findings for 10 cases of left-sided acute or chronic deep vein thrombosis caused by iliac vein compression syndrome were retrospectively evaluated. The patients were five women and five men (mean age+/-S.D., 49.9+/-15.6 years). In each patient with iliac vein compression syndrome, the diagnosis of the compression was established by venography performed during endovascular treatment. Diameter of the left common iliac vein was also measured in 14 control subjects without any lower extremity venous disease for comparison. RESULTS: In all 10 cases, CT images in the transverse plane demonstrated the left common iliac vein being compressed by the overlying right common iliac artery. The mean diameter at the origin of the left common iliac vein (3.5 mm) in patients group was much smaller than the mean diameter of the same vein (11.5 mm) in the control group (p<0.01). The mean percent stenosis of the left common iliac vein due to compression by the artery was 68%. CONCLUSION: Pelvic CT images in the transverse plane are useful for detecting iliac vein compression by the overlying right common iliac artery in patients with left-sided deep vein thrombosis. Radiologists should be aware of this imaging finding of iliac vein compression by the artery where the inferior vena cava bifurcates into the common iliac veins.

Adult↗

PubMed2005

The role of adsorption compression in nanocapillarity.

Influence of adsorption compression on nanocapillarity is discussed. Kelvin's equation for a compressible liquid is written in a form that takes into account not only Laplace's pressure, but also adsorption compression. This leads to a simple analytical equation for pressure in nanocapillaries. It is shown that the ratio of Laplace's pressure to the adsorption compression pressure determines different types of nanocapillary behavior. When the Laplace pressure dominates, it results in classical capillarity that is well studied and understood. There is an intermediate range where Laplace's pressure is partially or fully compensated by adsorption compression, and the resulting pressure in a capillary is an interplay between attraction to walls and repulsions from neighboring molecules in compressed adsorbed fluid. If the adsorption compression pressure dominates, it results in inversion of capillary pressure and the fluid adsorbed in the nanocapillary presses on walls from inside. This phenomenon has been observed experimentally for fluids in nanoporous solids; in particular, high-precision measurements have shown significant expansion of nanoporous adsorbents loaded with various fluids. It is also shown that oscillatory adhesion forces and internal forces in nanoporous adsorbents have a common thermodynamic origin and can be discussed in the framework of adsorption compression mechanisms.

Journal Article↗

PubMed2006

A new device producing manual sternal compression with thoracic constraint for cardiopulmonary resuscitation.

OBJECTIVE: Blood flow during conventional cardiopulmonary resuscitation (CPR) is usually less than adequate to sustain vital organ perfusion. A new chest compression device (LifeBelt) which compresses both the sternum and the lateral thoraces (compression and thoracic constraint) has been developed. The device is light weight, portable, manually powered and mechanically advantaged to minimize user fatigue. The purpose of this study was to evaluate the mechanism of blood flow with the device, determine the optimal compression force and compare the device to standard manual CPR in a swine arrest model. METHODS: Following anesthesia and instrumentation, intravascular contrast injections were performed in four animals and the performance characteristics of the device were evaluated in eight animals. In a comparative outcome study, 42 anesthetized and instrumented swine were randomized to receive LifeBelt or manual CPR. Ventricular fibrillation (VF) was induced electrically and was untreated for 7.5 min. After 7.5 min, countershocks were administered and chest compressions initiated. Pulseless electrical activity (PEA) was observed after one to three shocks in all animals. CPR was continued until restoration of spontaneous circulation (ROSC) or for 10 min after the first shock. If ROSC had not occurred within 5 min of beginning CPR, 0.01 mg/kg of epinephrine (adrenaline) was administered. During CPR, peak systolic aortic pressure (Ao), diastolic coronary perfusion pressure (CPP-diastolic aortic minus diastolic right pressure) and end-tidal CO(2) were measured. RESULTS: Angiographic studies demonstrated cardiac compression as the mechanism of blood flow. Optimal performance, determined by coronary perfusion pressure, was observed at a sternal force of 100-130 lb (45-59 kg). In the comparative trial, significant differences in the measured CPP were observed between LifeBelt and manual CPR both at 1 min (15+/-8 mmHg versus 10+/-6 mmHg, p<0.05) and 5 min (17+/-4 mmHg versus 13+/-7 mmHg, p<0.02) of chest compression. A greater (p<0.05) ETCO(2), a marker of cardiac output and systemic perfusion, was observed with LifeBelt CPR (20+/-7 mmHg) than with manual CPR (15+/-5 mmHg) at 1 min. Peak Ao pressures were not different between methods. With the device, 86% of animals were resuscitated compared to 76% in the manual group. CONCLUSIONS: Blood flow with the LifeBelt device is primarily the result of cardiac compression. At a sternal force of 100-130 lb (45-59 kg), the device produces greater CPP than well-performed manual CPR during resuscitation from prolonged VF.

Animals↗

PubMed2006

The quality of chest compressions by trained personnel: the effect of feedback, via the CPREzy, in a randomized controlled trial using a manikin model.

Even after training, the ability to perform effective cardiac compressions has been found to be poor and to decrease rapidly. We assessed this ability with and without a non-invasive feedback device, the CPREzy, during a 270s CPR session in an unannounced, single-blinded manikin study using 224 hospital employees and staff chosen at random and using a non-cross over design. The two groups self-assessed their knowledge and skills as adequate. However, the control group (N=111) had significantly more difficulty in delivering chest compressions deeper than 4 cm (25 versus 1 candidate in the CPREzy group), P=0.0001. The control group compressed ineffectively in 36% (+/-41%) of all compressions as opposed to 6+/-13% in the CPREzy group (N=112, P=0.0001). If compressions were effective initially, the time until >50% of compressions were less than 4 cm deep was 75+/-81s in the control group versus 194+/-87 s in the CPREzy group (P=0.0001 [-180 to -57.5]). After a few seconds of training in its use, our candidates used the CPREzy effectively. Against the background knowledge that estimation of compression depth by the rescuer or other team members is difficult, and that performing effective compressions is the cornerstone of any resuscitation attempt, our data suggests that a feedback device such as the CPREzy should be used consistently during resuscitation.

Adult↗

PubMed2006

Radiological assessment of the adult chest: implications for chest compressions.

The recommended depth for chest compression during adult cardiopulmonary resuscitation (CPR) is 4-5 cm, and for children one-third the anterior-posterior (AP) chest diameter. A compression depth of one-third of the AP chest diameter has also been suggested for adult CPR. We have assessed chest CT scans to measure what proportion of the adult AP chest diameter is compressed during CPR. Measurements of AP diameter of chest CT scans were taken from the skin anteriorly at the middle of the lower half of the sternum, perpendicularly to the skin on the posterior thorax. The anatomical structure that would be compressed at this level was also noted. One hundred consecutive CT scans were examined (66 males and 34 females). The age (mean +/- S.D.) was 68+/-12 years. AP chest diameter was 253 +/- 27 mm for males and 235 +/- 30 mm for females. The proportion of total AP chest diameter compressed with current compressions is 15.8-19.8% for males and 17.0-21.3% for females. The commonest anatomical structures that would be compressed are the ascending aorta (38%) and the top of the left atrium (36%). There is also a wide anatomical variation in the shape of the adult chest. A chest compression depth of 4-5 cm in adults equates to approximately one-fifth of the AP diameter of the adult chest.

Adult↗

PubMed1996

Compression of digital coronary angiograms does not affect visual or quantitative assessment of coronary artery stenosis severity.

Digital coronary angiographic techniques are now widely used in many cardiac catheterization laboratories. However, the full potential of digital imaging technology remains to be achieved because of its enormous storage and exchange requirements. Compression of digital imaging data allows a reduction in the volume of data so that storage and transmission are more efficient and cost-effective. Three angiographers reviewed the original and compressed formats of 96 coronary angiographic sequences in a blinded fashion to assess coronary lesion severity. Compression was achieved using the Joint Photographic Experts Group (JPEG) standard, which resulted in a compression ratio of approximately 15:1. The original format was reviewed in a blinded fashion a second time to assess for intraobserver variability of similar formats. Lesion severity was graded in quartiles. Coronary stenosis >50% was considered "significant." In parallel, the reproducibility of quantitative coronary angiographic (QCA) measurements of coronary artery dimensions was also evaluated. For the visual assessment of lesion severity in the compressed versus original formats, kappa=0.52, suggesting moderate agreement. When lesions were assessed as significant versus "insignificant," however, kappa=0.88, suggesting excellent agreement. In the 2 separate readings of the original data formats, kappa=0.44 for assessment of lesion severity by quartiles and kappa=0.72 for lesions assessed as significant versus insignificant. Analysis of the compressed versus original data sets using QCA resulted in an excellent correlation for the measurement of lesion severity (r=0.99). The correlation was equally strong when the original format was analyzed sequentially (r=0.98). Lossy JPEG (15:1) compression is a valid means for reducing storage and exchange requirements of coronary angiographic data. The variability in assessing lesion severity between the original and compressed formats is comparable to the reported variability in visual assessment of lesion severity in sequential analysis of cine film.

Angiography, Digital Subtraction↗

PubMed2003

A role for the interleukin-1 receptor in the pathway linking static mechanical compression to decreased proteoglycan synthesis in surface articular cartilage.

Loading of articular cartilage during weight bearing is essential for the maintenance of cartilage function. Although certain cyclic loading protocols stimulate extracellular matrix synthesis, constant or static compression decreases proteoglycan and collagen synthesis in cartilage explants. The goal of this study was to determine whether the compression-induced decrease in proteoglycan synthesis involves an interleukin-1 (IL-1) signaling pathway. Cartilage explants were compressed 50% in the presence of IL-1 receptor antagonist (IL-1ra), and the incorporation of [35S]sulfate into macromolecules was measured. IL-1ra increased sulfate incorporation in compressed cartilage but not in cartilage maintained at the in situ thickness (0% compression). IL-1alpha and IL-1beta mRNAs were detected in cartilage compressed 50% for at least 3h, while nitric oxide synthase II mRNA was only detected in cartilage compressed 50% for 6h. The data support a role for the IL-1 receptor in the pathway linking static compression to reduced proteoglycan synthesis.

Animals↗

PubMed1998

Transmural compression-induced proliferation and DNA synthesis through activation of a tyrosine kinase pathway in rat astrocytoma RCR-1 cells.

Gliosis results from abnormal proliferation of glial cells and often occurs in response to brain or spinal cord injury. There are many factors that trigger gliosis associated with such injuries, including ischemia, humoral factors produced by the injured tissue, and possibly mechanical compression itself. In the present study, the effects of mechanical compression on cell proliferation and DNA synthesis were examined in vitro with the rat astrocyte cell line RCR-1. Pressure was applied to cells by instilling compressed helium into sealed plates or flasks in which the partial pressure of oxygen were maintained constant. Compression resulted in time- and intensity-dependent increases in cell number and [3H]thymidine incorporation, with maximum effects apparent at 10 min and 120 mmHg. Compression-induced cell proliferation and DNA synthesis were not inhibited by gadolinium (Gd3+), a blocker of stretch-activated ion channels, or by inhibitors of protein kinase A, protein kinase C, or Ca2+/calmodulin-dependent protein kinases. However, the tyrosine kinase inhibitor genistein inhibited these effects of compression in a concentration-dependent manner. Conditioned medium from compressed cells also induced cell proliferation and DNA synthesis at atmospheric pressure in a genistein-sensitive manner. These results suggest that transmural compression triggers the release of a factor (or factors) that induces cell proliferation and DNA synthesis through a tyrosine kinase pathway in RCR-1 cells.

Animals↗

PubMed1997

Dynamic cardiac compression improves contractile efficiency of the heart.

The effect of dynamic cardiac compression on left ventricular contractile efficiency was assessed in terms of the pressure-volume relationship and myocardial oxygen consumption. In 11 excised cross-circulated dog hearts, the ventricle was directly compressed during systole (dynamic cardiac compression). Measurements for pressure-volume area (a measure of total mechanical energy), external work, and myocardial oxygen consumption were done before and during dynamic cardiac compression. Dynamic cardiac compression increased pressure-volume area by 28% +/- 17% (mean plus or minus the standard deviation) and external work by 24% +/- 20% (p = 0.0000185 and 0.0000212, respectively) at given end-diastolic and stroke volumes without affecting myocardial oxygen consumption. As a result, the oxygen cost of pressure-volume area, that is, the slope of the myocardial oxygen consumption-pressure-volume area relationship, significantly decreased by 16% +/- 13% (p = 0.0000135) whereas the pressure-volume area-independent myocardial oxygen consumption was unchanged. Then, contractile efficiency, that is, the reciprocal of the slope of the myocardial oxygen consumption-pressure-volume area relationship in joules significantly improved from 45% +/- 8% to 53% +/- 13% (p = 0.0000437). When the native myocardial oxygen consumption-pressure-volume area relationship was assessed by subtracting the dynamic cardiac compression pressure applied to the heart, the slope of the myocardial oxygen comsumption-pressure-volume area relationship returned to the control level. This indicates that the contractile efficiency of the native heart was not affected by dynamic cardiac compression. We conclude that dynamic cardiac compression enhances left ventricular pump function by improving the contractile efficiency of the overall heart leaving the energetics of the native heart unchanged.

Animals↗

PubMed1993

The effect of intermittent pneumatic compression devices on intraoperative blood loss during radical prostatectomy and radical cystectomy.

Intermittent pneumatic compression devices are a widely used, effective and presumed risk-free method of deep venous thrombosis prophylaxis, presumably by increasing peak venous blood velocity, and stimulating local and systemic fibrinolysis. We investigated whether intermittent pneumatic compression devices had any effect on intraoperative blood loss or transfusion during radical pelvic urological surgery. To our knowledge no previous study has addressed these issues. Records were reviewed for patients undergoing radical retropubic prostatectomy or radical cystectomy with diversion from 1985 to 1990. A total of 91 cases was reviewed: 38 radical retropubic prostatectomies and 53 radical cystectomies with diversion (34 male and 19 female patients). There were 59 patients with intermittent pneumatic compression devices (29 radical retropubic prostatectomies and 30 radical cystectomies with diversion) and 32 without intermittent pneumatic compression devices (9 radical retropubic prostatectomies and 23 radical cystectomies with diversion). Intraoperative blood loss and transfusions were calculated for each group with and without intermittent pneumatic compression devices. No clinically apparent lower extremity deep venous thrombosis or pulmonary embolus was diagnosed in any patient. For the group with intermittent pneumatic compression devices mean intraoperative blood loss was 2,541 ml. (range 700 to 8,850) versus 1,807 ml. (range 450 to 5,100) without a device, for a statistically significant difference of 734 ml. (p = 0.005). When 5 patients with excessive intraoperative blood loss (more than 5,000 ml.) were excluded the statistically significant difference was maintained. When comparing radical retropubic prostatectomy and radical cystectomy with diversion, with and without intermittent pneumatic compression devices, blood loss was greater for the group with a device for each procedure. Differences in intraoperative blood loss were independent of sex or tumor stage. Intraoperative transfusions were increased by approximately 0.6 units per patient with the device. Our study suggests that intermittent pneumatic compression devices may increase blood loss during a radical pelvic operation.

Blood Loss, Surgical↗

PubMed1998

Ultrasound-guided compression of femoral pseudoaneurysm: an audit of practice.

OBJECTIVE: To audit the practice of ultrasound-guided compression of femoral pseudoaneurysm in a specialist cardiac hospital. BACKGROUND: Femoral pseudoaneurysm is an important complication of invasive cardiac procedures. This may require surgical repair but more recently ultrasound-guided compression for ablating pseudoaneurysms has been described. We investigated the success of such a procedure. METHODS AND RESULTS: In a 26-month period, 56 patients were referred for ultrasound scanning to exclude the formation of a femoral pseudoaneurysm following transfemoral cardiac procedures. During this period, 5756 diagnostic cardiac catherisations and 1165 coronary angioplasties were performed in our hospital (total of 6921 procedures). Of the 56 patients, 20 patients (0.3% of 6921) were found to have a pseudoaneurysm. Ultrasound-guided compression was attempted in 11 patients and was successful in 7 patients (64%). Of the patients who had failed ultrasound-guided compression, 2 proceeded to surgical closure and 2 were treated conservatively with compression stockings to facilitate thrombosis of the pseudoaneurysm. Of those who did not have an attempted ultrasound-guided compression of the pseudoaneurysm (n=9), a conservative approach consisting of resting the leg was adopted to facilitate spontaneous thrombosis of the pseudoaneurysm; repeat ultrasound scanning was needed for follow-up and 1 patient required surgical closure in this group. CONCLUSIONS: In patients with a femoral pseudoaneurysm following an invasive cardiac procedure, ultrasound-guided compression may be useful as an immediate step to ablate the pseudoaneurysm. This avoids either prolonged leg rest and repeated ultrasound scanning or surgical intervention. However, ultrasound-guided compression is not always successful; in these patients, a period of conservative management with repeat ultrasound scanning is appropriate to allow for the possible spontaneous thrombosis of the pseudoaneurysm. Surgical closure is needed in those patients whose pseudoaneurysm is enlarging, painful or remain patent.

Adult↗

PubMed2000

The relationship between ankle plantar flexor muscle moments and knee compressive forces in subjects with and without pain.

OBJECTIVE: The purpose of this study was to compare the compressive knee joint reaction force and ankle plantar flexor muscle moment during the terminal stance phase in symptomatic osteoarthritic and non-symptomatic subjects.DESIGN. The study design was a comparative investigation of walking patterns.BACKGROUND. Patients with knee osteoarthritic symptoms may employ altered gait patterns to reduce the loading of painful joints. Speculation is that decreased ankle plantar flexor moments in the terminal stance phase may be an attempt to minimize compressive knee joint reaction forces.METHODS. Twenty community-dwelling men (52-83 years old), ten with knee osteoarthritis and ten non-symptomatic, were studied while walking across a walkway containing two force plates at a comfortable speed. Retroreflective markers were placed in accordance with the Helen Hayes marker system and recorded with six 120 Hz cameras. Three-dimensional kinematics and kinetics were computed.RESULTS. Group means for gait velocity, peak ankle plantar flexor moment and compressive knee joint reaction force were significantly less for the osteoarthritic group relative to the non-symptomatic group. When accounting for the decreased velocity in the osteoarthritic group, however, no group differences were observed. There were significant correlations between all three gait parameters (r>0.75), but peak ankle plantar flexor moment was the greatest predictor of compressive knee joint reaction force.CONCLUSIONS. While no group differences were found for compressive knee joint reaction forces when accounting for gait velocity, it appears that subjects with osteoarthritis utilize gait velocity as a mechanism to reduce compressive knee joint reaction forces. RelevanceAn understanding of compressive knee joint reaction forces is important to the understanding of the disabling effects of knee osteoarthritis on physical function and to the understanding of appropriate and safe interventions to improve not only global parameters (e.g., pain, gait velocity), but also to "re-program" the locomotor pattern to develop "normal" muscle moments without increasing compressive knee joint reaction forces to painful levels.

Age Factors↗

PubMed2003

Quality of CPR with three different ventilation:compression ratios.

Current adult basic cardiopulmonary resuscitation (CPR) guidelines recommend a 2:15 ventilation:compression ratio, while the optimal ratio is unknown. This study was designed to compare arterial and mixed venous blood gas changes and cerebral circulation and oxygen delivery with ventilation:compression ratios of 2:15, 2:50 and 5:50 in a model of basic CPR. Ventricular fibrillation (VF) was induced in 12 anaesthetised pigs, and satisfactory recordings were obtained from 9 of them. A non-intervention interval of 3 min was followed by CPR with pauses in compressions for ventilation with 17% oxygen and 4% carbon dioxide in a randomised, cross-over design with each method being used for 5 min. Pulmonary gas exchange was clearly superior with a ventilation:compression ratio of 2:15. While the arterial oxygen saturation stayed above 80% throughout CPR for 2:15, it dropped below 40% during part of the ventilation:compression cycle for both the other two ratios. On the other hand, the ratio 2:50 produced 30% more chest compressions per minute than either of the two other methods. This resulted in a mean carotid flow that was significantly higher with the ratio of 2:50 than with 5:50 while 2:15 was not significantly different from either. The mean cerebrocortical microcirculation was approximately 37% of pre-VF levels during compression cycles alone with no significant differences between the methods. The oxygen delivery to the brain was higher for the ratio of 2:15 than for either 5:50 or 2:50. In parallel the central venous oxygenation, which gives some indication of tissue oxygenation, was higher for the ratio of 2:15 than for both 5:50 and 2:50. As the compressions were done with a mechanical device with only 2-3 s pauses per ventilation, the data cannot be extrapolated to laypersons who have great variations in quality of CPR. However, it might seem reasonable to suggest that basic CPR by professionals should continue with ratio of 2:15 at present if it can be shown that similar brief pauses for ventilation can be achieved in clinical practice.

Animals↗