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PubMed1988

Cardiac tamponade: a comparison of right versus left heart compression.

It has been postulated that in cardiac tamponade, the hemodynamic effects of compression of the right heart chambers and great veins are more important than are the effects of left heart compression. In 10 anesthetized dogs with surgically compartmented pericardium, the hemodynamic effects of right atrial and right ventricular compression were compared with the hemodynamic effects of left atrial and left ventricular compression. The effects of right heart compression, left heart compression, and then effects of combined right and left heart compression, were compared at three levels of intrapericardial pressure: 10, 15 and 20 mm Hg. Aortic mean pressure decreased significantly at each level of intrapericardial pressure with right-sided tamponade but not with left-sided tamponade. Left atrial mean pressures decreased significantly with right-sided tamponade and increased with left-sided and combined tamponade. Right atrial mean pressures increased significantly with right-sided and combined tamponade, but not with left-sided tamponade. Heart rate increased significantly with each of the three varieties of tamponade. Cardiac output and stroke volume, which decreased with each variety of tamponade, were significantly lower during right-sided than during left-sided tamponade. Combined tamponade lowered stroke volume more than did right-sided tamponade, and lowered cardiac output more at 15 and 20 mm Hg intrapericardial pressure. It is concluded that, in this preparation, right-sided cardiac compression has more important hemodynamic effects than does left-sided compression. However, left-sided tamponade still makes a significant contribution to the total hemodynamic picture of cardiac tamponade.

Animals↗

PubMed2006

Influence of bicycle seat pressure on compression of the perineum: a MRI analysis.

It is a common belief that bicycle seat pressure compresses neurovascular tissues in the perineum and may lead to perineal and penile pathologies in male cyclists. The purpose of this study was to examine the effect bicycle seat pressure has on compression of the perineal cavernous spaces, which house the penile neurovascular tissues. A second purpose was to identify where peak cavernous compression occurs in relation to a bicycle seat. Five males were assessed for compression of the corpus spongiosum and corpora cavernosa with and without bicycle seat pressure using MRI. Seat pressure was applied using a custom loading device designed to replicate seat pressure recorded during stationary bicycling. The distance between a horizontal midline of the seat and the point of peak cavernous space compression was made on sagittal plane images. Diameter measurements of the cavernous spaces at the point of peak compression were made on coronal plane images. Results revealed that peak cavernous space compression occurred below the pubic symphysis, 40.7(+/-11.4) mm anterior to the midline of the seat. Corpus spongiosum values in the unloaded condition were 148% greater than the loaded condition (p=0.008). Similarly, the left and right corpora cavernosa values for the unloaded condition were 252% and 232% greater, respectively, than the loaded condition (p=0.02-0.03). Cavernous spaces that house penile arteries and nerves were compressed maximally below the pubic symphysis. Because this location of peak compression was not different between subjects, it may be a universal impingement zone that limits blood flow and neural activity to and from the penis. This information can be used to optimize seat design and thus reduce perineal injuries.

Adult↗

PubMed2005

Optimal compressive force induces bone formation via increasing bone morphogenetic proteins production and decreasing their antagonists production by Saos-2 cells.

Orthodontic tooth movement induced alveolar bone resorption and formation around the teeth applied mechanical force. Although mechanical force can promote bone formation, the molecular mechanism that underlies this phenomenon is not fully understood. The purposes of this study were to determine how mechanical stress affects the osteogenic response of human osteoblastic cells (Saos-2), and also to examine the optimal compressive force for osteogenesis in vitro. Saos-2 cells were cultured with or without continuously compressive force (0.5-3.0 g/cm2). The expression of bone morphogenetic proteins (BMPs), their antagonists, and transcription factors which involved in osteogenesis were measured using real-time PCR and/or Western blot analysis. Phosphorylation of Smad1 was determined by Western blot. Loading with 1.0 g/cm2 of compressive force significantly increased the expression of BMPs, Runx2 and osterix. In contrast, the expression of BMP antagonists and AJ18 was decreased with 1.0 g/cm2 of compressive force. Loading with 1.0 g/cm2 of compressive force also induced phosphorylation of Smad1. Noggin inhibited the compressive force-induced phosphorylation of Smad1 markedly, and also partially blocked compressive force-induced Runx2 mRNA expression. Moreover, the conditioned medium from 1.0 g/cm2 of compressive force applied cells apparently increased calcium content in mineralized nodules of Saos-2 culture. This study demonstrates that an optimal compressive force stimulates in vitro mineralization via increasing BMPs production and decreasing their antagonists production.

Bone Morphogenetic Proteins↗

PubMed2006

Pituitary stalk compression by the dorsum sellae: possible cause for late childhood onset growth disorders.

PURPOSE: The purpose of this study was to evaluate the relationship between pituitary stalk compression by the dorsum sellae and clinical or laboratory findings in short stature children. MATERIALS AND METHODS: We retrospectively reviewed magnetic resonance images of the pituitary gland and pituitary stalk for 34 short stature children with growth hormone (GH) deficiency and 24 age-matched control cases. We evaluated the degree of pituitary stalk compression caused by the dorsum sellae. Body height, GH level, pituitary height and onset age of the short stature were statistically compared between cases of pituitary stalk compression with associated stalk deformity and cases without compression. RESULTS: Compression of the pituitary stalk with associated stalk deformity was seen in nine cases within the short stature group. There were no cases observed in the control group. There were no significant differences found for body height, GH level and pituitary height between the cases of pituitary stalk compression with associated stalk deformity and cases without compression. However, a significant difference was seen in the onset age between cases with and without stalk compression. CONCLUSION: Pituitary stalk compression with stalk deformity caused by the dorsum sellae was significantly correlated with late childhood onset of short stature.

Adolescent↗

PubMed2004

Uninterrupted chest compression CPR is easier to perform and remember than standard CPR.

INTRODUCTION: It has long been observed that CPR skills rapidly decline regardless of the modality used for teaching or criteria used for testing. Uninterrupted chest compression CPR (UCC-CPR) is a proposed alternative to standard single rescuer CPR (STD-CPR) for laypersons in witnessed unexpected cardiac arrest in adults. It delivers substantially more compressions per minute and may be easier to remember and perform than standard CPR. METHODS: In this prospective study, 28 medical students were taught STD-CPR and UCC-CPR and then were tested on each method at baseline (0), 6, and 18 months after training. The students' performance for at least 90 s of CPR was evaluated based on video and Laerdal Skillreporter Resusci Anne recordings. RESULTS: The mean number of correct chest compressions delivered per minute trended down over time in STD-CPR (23 +/- 3, 19 +/- 4 , and 15 +/- 3; P = 0.09) but stayed the same in UCC-CPR (43 +/- 9, 38 +/- 7, and 37 +/- 7 = 0.91) at 0, 6, and 18 months, respectively. The mean percentage of chest compressions delivered correctly fell over time in STD-CPR (54 +/- 6%, 35 +/- 6%, and 32 +/- 6%; P = 0.02) but stayed the same in UCC-CPR (34 +/- 5%, 41 +/- 7%, and 38 +/- 8%) at 0, 6, and 18 months, respectively. The number of chest compressions delivered per minute was higher in UCC-CPR at 0, 6, and 18 months (113 versus 44, P < 0.0001; 94 versus 47, P < 0.0001; and 92 versus 44, P < 0.001). The greater number of chest compressions was due to a mean ventilaroty pause of 13-14 s during STD-CPR at all three time points. CONCLUSIONS: Chest compression performance during STD-CPR declined in repeated testing over 18 months whereas there was minimal decline in chest compressions performance on repeated testing of UCC-CPR. In addition, substantially more chest compressions were delivered during UCC-CPR compared to STD-CPR at all time points primarily because of long pauses accompanying rescue breathing.

Adult↗

PubMed2005

Incomplete chest wall decompression: a clinical evaluation of CPR performance by EMS personnel and assessment of alternative manual chest compression-decompression techniques.

BACKGROUND: Complete chest wall recoil improves hemodynamics during cardiopulmonary resuscitation (CPR) by generating relatively negative intrathoracic pressure and thus draws venous blood back to the heart, providing cardiac preload prior to the next chest compression phase. OBJECTIVE: Phase I was an observational case series to evaluate the quality of chest wall recoil during CPR performed by emergency medical services (EMS) personnel on patients with an out-of-hospital cardiac arrest. Phase II was designed to assess the quality of CPR delivered by EMS personnel using an electronic test manikin. The goal was to determine if a change in CPR technique or hand position would improve complete chest wall recoil, while maintaining adequate duty cycle, compression depth, and correct hand position placement. Standard manual CPR and three alternative manual CPR approaches were assessed. METHODS AND RESULTS: Phase I--The clinical observational study was performed by an independent observer noting incomplete chest wall decompression and correlating that observation with electronically measured airway pressures during CPR in adult patients with out-of-hospital cardiac arrest. Rescuers were observed to maintain some residual and continuous pressure on the chest wall during the decompression phase of CPR, preventing full chest wall recoil, at some time during resuscitative efforts in 6 (46%) of 13 consecutive adults (average +/- S.D. age 63 +/-5.8 years). Airway pressures were consistently positive during the decompression phase (>0 mmHg) during those observations. Phase II: This randomized prospective trial was performed on an electronic test manikin. Thirty EMS providers (14 EMT-Basics, 5 EMT-Intermediates, and 11 EMT-Paramedics), with an average age +/- S.D. of 32 +/- 8 years and 6.5 +/- 4.2 years of EMS experience, performed 3 min of CPR on a Laerdal Skill Reporter CPR manikin using the Standard Hand Position followed by 3 min of CPR (in random order) using three alternative CPR techniques: (1) Two-Finger Fulcrum Technique--lifting the heel of the hand slightly but completely off the chest during the decompression phase of CPR using the thumb and little finger as a fulcrum; (2) Five-Finger Fulcrum Technique--lifting the heel of the hand slightly but completely off the chest during the decompression phase of CPR using all five fingers as a fulcrum; and (3) Hands-Off Technique--lifting the heel and all fingers of the hand slightly but completely off the chest during the decompression phase of CPR. These EMS personnel did not know the purpose of the studies prior to or during this investigation. Adequate compression depth was poor for all hand positions tested and ranged only from 29.9 to 48.5% of all compressions. When compared with the Standard Hand Position, the Hands-Off Technique decreased mean compression duty cycle from 46.9 +/- 6.4% to 33.3 +/- 4.6%, (P < 0.0001) but achieved the highest rate of complete chest wall recoil (95.0% versus 16.3%, P < 0.0001) and was 129 times more likely to provide complete chest wall recoil (OR: 129.0; CI: 43.4-382.0). There were no significant differences in accuracy of hand placement, depth of compression, or reported increase in fatigue or discomfort with its use compared with the Standard Hand Position. CONCLUSIONS: Incomplete chest wall decompression was observed at some time during resuscitative efforts in 6 (46%) of 13 consecutive adult out-of-hospital cardiac arrests. The Hands-Off Technique decreased compression duty cycle but was 129 times more likely to provide complete chest wall recoil (OR: 129.0; CI: 43.4-382.0) compared to the Standard Hand Position without differences in accuracy of hand placement, depth of compression, or reported increase in fatigue or discomfort with its use. All forms of manual CPR tested (including the Standard Hand Position) in professional EMS rescuers using a recording manikin produced an inadequate depth of compression more than half the time. These data support development and testing of more effective means to deliver manual as well as mechanical CPR.

Adult↗

PubMed2006

A randomized comparison of manual, mechanical and high-impulse chest compression in a porcine model of prolonged ventricular fibrillation.

BACKGROUND: Elevated coronary perfusion pressure (CPP) during CPR is associated with return of spontaneous circulation (ROSC). We compared CPP achieved with three methods of chest compression: manual (MAN), mechanical (MECH) and high-impulse mechanical (HI) in a porcine model of prolonged ventricular fibrillation (VF). We hypothesized that HI (very rapid acceleration of the down-stroke) would produce greater CPPs than MAN or MECH, and that HI would also produce a higher rate of ROSC. METHODS: Twenty-eight domestic swine (mean 27.8 kg) were randomly assigned to three methods of chest compression. Animals were instrumented under anesthesia, and VF was induced and untreated for 8 min. After 2 min of CPR, epinephrine (adrenaline) (0. 1 mg/kg), vasopressin (40 U) and propranolol (1.0 mg) were administered. CPR continued for three more minutes, after which up to three rescue shocks were delivered. CPP was determined in an automated fashion by measuring the difference between aortic and right atrial pressures 0.1s prior to the down-stroke of each compression (i.e. end-relaxation). ROSC was defined as a systolic pressure greater than 80 mmHg sustained for at least 1 min. We analyzed CPP and ROSC using repeated measures ANOVA and Fisher's exact test. RESULTS: Over the 5 min of CPR, CPP increased more with HI compression than with MAN compression (p=0.017). ROSC was attained in 4/9 MAN, 6/9 MECH and 10/10 HI (HI versus MAN p=0.01). CONCLUSIONS: Over the course of CPR, HI compression increased CPP more than MAN compression. HI compression produced a significantly higher rate of ROSC than MAN, but not MECH compression.

Adrenergic alpha-Agonists↗

PubMed2006

Incomplete chest wall decompression: a clinical evaluation of CPR performance by trained laypersons and an assessment of alternative manual chest compression-decompression techniques.

BACKGROUND: Complete chest wall recoil improves hemodynamics during CPR by generating relatively negative intrathoracic pressure, which draws venous blood back to the heart, providing cardiac preload prior to the next chest compression. OBJECTIVE: This study was designed to assess the quality of CPR delivered by trained laypersons and to determine if a change in CPR technique or hand position would improve complete chest wall recoil, while maintaining adequate duty cycle, compression depth, and proper hand position placement. Standard manual CPR and three alternative manual CPR approaches were assessed. METHODS: This randomized prospective trial was performed on an electronic test manikin. Thirty laypersons (mean age of 40.6 years (range 28-55)), who were trained in CPR within the last 24 months, signed an informed consent and participated in the trial. Subjects performed 3 min of CPR on a Laerdal Skill Reportertrade mark CPR manikin using the Standard Hand Position followed by 3 min of CPR (in random order) using three alternative CPR techniques: (1) Two-Finger Fulcrum Technique - lifting the heel of the hand slightly but completely off the chest during the decompression phase of CPR using the thumb and little finger as a fulcrum; (2) Five-Finger Fulcrum Technique - lifting the heel of the hand slightly but completely off the chest during the decompression phase of CPR using all five fingers as a fulcrum; (3) Hands-Off Technique - lifting the heel and all fingers of the hand slightly but completely off the chest during the decompression phase of CPR. The participants did not know the purpose of the study prior to, or during this investigation. RESULTS: Adequate compression depth was poor for all hand positions tested and ranged only from 18.6 to 35.7% of all compressions. When compared with the Standard Hand Position, the Hands-Off Technique decreased the mean compression duty cycle from 39.0 +/- 1.0 to 33.5 +/- 1.0%, (P < 0.0001) but achieved the highest rate of complete chest wall recoil (92.5% versus 24.1%, P < 0.0001) and was 46.3 times more likely to provide complete chest wall recoil (OR: 46.3; CI: 16.4-130.3). There were no significant differences in accuracy of hand placement, adequate depth of compression, or perceived discomfort with its use compared with the Standard Hand Position. CONCLUSIONS: The Hands-Off Technique decreased compression duty cycle but was 46.3 times more likely to provide complete chest wall recoil (OR: 46.3; CI: 16.4-130.3) compared to the Standard Hand Position without differences in accuracy of hand placement, adequate depth of compression, or perceived discomfort with its use. All forms of manual CPR tested (including the Standard Hand Position) in trained laypersons produced an inadequate depth of compression for two-thirds of the time. These data support development and testing of more effective layperson CPR training programmes and more effective means to deliver manual as well as mechanical CPR.

Adult↗

PubMed2001

Static compression of articular cartilage can reduce solute diffusivity and partitioning: implications for the chondrocyte biological response.

Chondrocytes depend upon solute transport within the avascular extracellular matrix of adult articular cartilage for many of their biological activities. Alterations to bioactive solute transport may, therefore, represent a mechanism by which cartilage compression is transduced into cellular metabolic responses. We investigated the effects of cartilage static compression on diffusivity and partitioning of a range of model solutes including dextrans of molecular weights 3 and 40 kDa, and tetramethylrhodamine (a 430 Da fluorophore). New fluorescence methods were developed for real-time visualization and measurement of transport within compressed cartilage explants. Experimental design allowed for multiple measurements on individual explants at different compression levels in order to minimize confounding influences of compositional variations. Results demonstrate that physiological levels of static compression may significantly decrease solute diffusivity and partitioning in cartilage. Effects of compression were most dramatic for the relatively high molecular weight solutes. For 40 kDa dextran, diffusivity decreased significantly (p<0.01) between 8% and 23% compression, while partitioning of 3 and 40 kDa dextran decreased significantly (p<0.01) between free-swelling conditions and 8% compression. Since diffusivity and partitioning can influence pericellular concentrations of bioactive solutes, these observations support a role for perturbations to solute transport in mediating the cartilage biological response to compression.

Animals↗

PubMed1993

A comparison of chest compressions between mechanical and manual CPR by monitoring end-tidal PCO2 during human cardiac arrest.

STUDY OBJECTIVE: To compare the use of mechanical and manual chest compressions during cardiac arrest based on continuous monitoring of end-tidal PCO2 (PETCO2). DESIGN: Prospective, randomized, crossover design. SETTING AND PARTICIPANTS: Fifteen consecutive adults ranging in age from 33 to 78 years who presented in nontraumatic cardiac arrest to the emergency department of a large teaching hospital. INTERVENTIONS: Study protocols were begun late in the resuscitation after initial resuscitation attempts were unsuccessful. Patients received four alternating five-minute trials (two manual and two mechanical), being randomized to begin with either technique. Mechanical compressions were performed by a mechanical device at a compression depth of 2 in. Both mechanical and manual compressions were delivered at a rate of 80 with a ventilation delivered after every fifth compression. Persons performing manual CPR were experienced American Heart Association basic life support providers, and no person performed manual CPR more than once during the study period. No resuscitative drugs were administered during the study period. PETCO2 was monitored continuously; those performing manual CPR were blinded to the PETCO2 monitor. Data were analyzed with repeated-measures analysis of variance and Scheffé multiple comparisons with the alpha error rate set of .05. MEASUREMENTS AND RESULTS: Mean PETCO2 during mechanical CPR was 13.6 +/- 4.14 mm Hg compared with 6.9 +/- 2.42 mm Hg during manually performed CPR (P < .001), a difference of 97%. Average mechanical CPR PETCO2 was higher in all cases. No patient was resuscitated successfully. Capnography also indicated that most CPR providers were inconsistent in their chest compressions. CONCLUSION: This study suggests that cardiac output produced with mechanical chest compressions is greater than that produced with manual compressions as demonstrated by the significantly higher PETCO2 levels during mechanical CPR. Reasons for this are unclear. In addition, monitoring of PETCO2 may help optimize chest compressions during CPR.

Adult↗

PubMed2002

Improving the effectiveness of continuous closed chest compressions: an exploratory study.

UNLABELLED: This study was carried out to establish the length of time over which an individual can maintain effective chest compressions and the most effective pattern of rest and handover among a team. The continuing effectiveness of chest compressions was compared between groups of 2 or 3 rescuers performing chest compressions for 1, 2 or 3 min during scenarios lasting 18 min. Evaluation of the effectiveness of compressions was achieved using a computerised resuscitation manikin (Laerdal/Skillmeter) on a hospital trolley. Twenty-one volunteers competent in basic life support participated. The results were analysed using one-way analysis of variance and Dunnett's contrast of the various scenarios. The results demonstrated that a three person team delivering 1 min periods of chest compressions in rotation is significantly better than other sequences at 5 min and beyond (P<0.0001). At 18 min 91.5% of all chest compressions delivered by this three person team were greater than 70% effective. There was no significant difference between the first and final set of chest compressions. CONCLUSION: Continuous chest compressions performed for 1 min, preferably by three rescuers in rotation, maintain a high level of effectiveness. Longer periods of chest compressions should be discouraged.

Adult↗

PubMed1997

Restenosis of endovascular stents from stent compression.

OBJECTIVES: We sought to determine the basis for restenosis within superficial femoral arteries (SFAs) and hemodialysis conduits treated with balloon-expandable stents. BACKGROUND: Use of stents within coronary and peripheral vessels continues to increase exponentially. The mechanism of restenosis within stents placed at various vascular sites is not well understood. In particular, the implications of deploying a balloon-expandable stent in a compressible site are not well understood. METHODS: After the serendipitous detection of stent deformation during intravascular ultrasound (IVUS) examination of a restenosed dialysis fistula, we evaluated a consecutive series of patients with stents placed in compressible vascular sites, including the SFA (six patients) and hemodialysis fistulae (five patients). Clinical, angiographic and IVUS examinations were performed to evaluate mechanisms of restenosis. RESULTS: Stent compression was identified as the principal cause of restenosis in all dialysis conduits and SFAs. Stent deformity was not reliably identified by angiography; however, IVUS identified compression of two forms: eccentric deformation, implicating two-point compressive force, and complete circumferential encroachment of stent struts around the catheter, suggesting multidirectional compressive force. Despite redilation, secondary restenosis resulting from recurrent compression recurred in most sites. CONCLUSIONS: Restenosis within balloon-expandable endovascular stents may occur as a result of stent compression, a phenomenon readily detected by IVUS, but often not by angiography. These findings have significant implications for the use of balloon-expandable stents within vascular sites subject to extrinsic compression, such as hemodialysis conduits, the adductor canal segment of the SFA and carotid arteries.

Aged↗

PubMed2003

Differential effects of static and dynamic compression on meniscal cell gene expression.

Cells of the meniscus are exposed to a wide range of time-varying mechanical stimuli that may regulate their metabolic activity in vivo. In this study, the biological response of the meniscus to compressive stimuli was evaluated in vitro, using a well-controlled explant culture system. Gene expression for relevant extracellular matrix proteins was quantified using real-time RT-PCR following a 24 h period of applied static (0.1 MPa compressive stress) or dynamic compression (0.08-0.16 MPa). Static and dynamic compression were found to differentially regulate mRNA levels for specific proteins of the extracellular matrix. Decreased mRNA levels were observed for decorin ( approximately 2.1 fold-difference) and type II collagen ( approximately 4.0 fold-difference) following 24 h of dynamic compression. Decorin mRNA levels also decreased following static compression ( approximately 4.5 fold-difference), as did mRNA levels for both types I ( approximately 3.3 fold-difference) and II collagen ( approximately 4.0 fold-difference). Following either static or dynamic compression, mRNA levels for aggrecan, biglycan and cytoskeletal proteins were unchanged. It is noteworthy that static compression was associated with a 2.6 fold-increase in mRNA levels for collagenase, or MMP-1, suggesting that the homeostatic balance between collagen biosynthesis and catabolism was altered by the mechanical stimuli. These findings demonstrate that the biosynthetic response of the meniscus to compression is regulated, in part, at the transcriptional level and that transcription of types I and II collagen as well as decorin may be regulated by common mechanical stimuli.

Animals↗

PubMed2004

Pathology of lumbar nerve root compression. Part 2: morphological and immunohistochemical changes of dorsal root ganglion.

STUDY DESIGN: This study is to investigate the changes of dorsal root ganglion (DRG) induced by mechanical compression using in vivo model. OBJECTIVES: The effect of axonal flow disturbance induced by nerve root compression was determined in DRG. SUMMARY OF BACKGROUND DATA: The dorsal root ganglion should not be overlooked when considering the mechanism of low back pain and sciatica, so it is important to understand the morphologic and functional changes that occur in primary sensory neurons of the dorsal root ganglion as a result of nerve root compression. However, few studies have looked at changes of neurons within the dorsal root ganglion caused by disturbance of axonal flow and the axon reaction as a result of mechanical compression of the dorsal root through which the central branches of the primary sensory nerves pass. METHODS: In mongrel dogs, the seventh lumbar nerve root was compressed for 24 h, one week, or three weeks using a clip with a pressure of 7.5 gf. Morphologic changes of the primary sensory neurons in the dorsal root ganglion secondary to the axon reaction were examined by light and electron microscopy. Changes of immunostaining for substance P (SP), calcitonin gene-related peptide (CGRP), and somatostatin (SOM) in the primary sensory neurons affected by central chromatolysis after nerve root compression were also examined. RESULTS: Light microscopy showed central chromatolysis of neurons in the dorsal root ganglion from one week after the start of compression. Electron microscopy of the affected neurons revealed movement of the nucleus to the cell periphery and the loss of rough endo-plasmic reticulum and mitochondria from the central region. Immunohistochemical studies showed a marked decrease of SP, CGRP, and SOM staining in small ganglion cells with central chromatolysis when compared with cells from control ganglia. CONCLUSION: It is important to be aware that in patients with nerve root compression due to lumbar disc herniation or lumbar canal stenosis, dysfunction is not confined to degeneration at the site of compression, but also extends to the primary sensory neurons within the dorsal root ganglion as a result of the axon reaction. Patients with sensory disturbance should therefore be fully informed of the fact that these symptoms will not resolve immediately after surgery.

Animals↗

PubMed1994

Microangiopathy of the skin and the effect of leg compression in patients with chronic venous insufficiency.

PURPOSE: The reasons for the efficacy of leg compression in the treatment of chronic venous insufficiency are not clear. We have used laser Doppler fluxmetry to assess the effect of external compression on the skin microcirculation. METHODS: Fifteen patients with lipodermatosclerosis caused by chronic venous insufficiency and 15 control subjects were studied in the supine and sitting positions. The laser Doppler probe, incorporated in a polyethylene chamber, was applied to the lower leg underneath a blood pressure cuff. Pressures were applied from 10 to 100 mm Hg in increments of 10 mm Hg. A computer data logging system recorded laser Doppler flux blood cell velocity, and concentration of moving blood cells. RESULTS: In patients in the supine position, 20 mm Hg compression resulted in a median increase of 33% in laser Doppler flux, and a median increase of 79% in blood cell velocity, but higher pressures caused a progressive decrease in laser Doppler flux and blood cell velocity. With the patient in the sitting position, compression up to 60 mm Hg caused an increase in laser Doppler flux (median percentage increase at 20 mm Hg compression 84%) and blood cell velocity (median percentage increase at 20 mm Hg compression 22%). At 20 mm Hg compression, the concentration of moving blood cells decreased in the supine position (median percentage fall 27%) but did not change significantly in the dependent position. The effects of compression in control subjects were similar to those in patients, but to a lesser degree. CONCLUSION: Our study suggests that compression treatment may achieve part of its effect by causing an increase in the microcirculatory flow velocity.

Aged↗

PubMed2003

Acoustic analysis of pathological voices compressed with MPEG system.

The MPEG-1 Layer 3 compression schema of audio signal, commonly known as mp3, has caused a great impact in recent years as it has reached high compression rates while conserving a high sound quality. Music and speech samples compressed at high bitrates are perceptually indistinguishable from the original samples, but very little was known about how compression acoustically affects the voice signal. A previous work with normal voices showed a high fidelity at high-bitrate compressions both in voice parameters and the amplitude-frequency spectrum. In the present work, dysphonic voices were tested through two studies. In the first study, spectrograms, long-term average spectra (LTAS), and fast Fourier transform (FFT) spectra of compressed and original samples of running speech were compared. In the second study, intensities, formant frequencies, formant bandwidths, and a multidimensional set of voice parameters were tested in a set of sustained phonations. Results showed that compression at high bitrates (96 and 128 kbps) preserved the relevant acoustic properties of the pathological voices. With compressions at lower bitrates, fidelity decreases, introducing some important alterations. Results from both works, Gonzalez and Cervera and this paper, open up the possibility of using MPEG-compression at high bitrates to store or transmit high-quality speech recordings, without altering their acoustic properties.

Acoustic Stimulation↗

PubMed2000

Effects of MPEG compression on the quality and diagnostic accuracy of digital echocardiography studies.

The advantages of digital echocardiography studies include ease of retrieval, review, comparison, duplication, and quantitation as well as the potential for moving studies over networks. However, the large amounts of data associated with digital echocardiography studies have posed new problems. Reduction of the amount of data can be accomplished with image compression, in particular MPEG-1 (Moving Pictures Expert Group), which is designed for dynamic image sequences. However the effects of different levels of compression on the quality and diagnostic content of echocardiographic images need to be established. Digital sequences of single cardiac cycles were acquired in 40 consecutive patients, MPEG-1-compressed at different effective ratios (60:1, 80:1, 120:1, 200:1, 300:1, 370:1, 500:1), reviewed, and scored for endocardial visualization. The overall visualization scores and percentages of nonvisualized segments in the compressed images were not different from the uncompressed images up to a compression ratio of 200:1. Differential effects of compression were noted on a segmental basis and also varied with baseline image quality. The ability to correctly identify regional wall motion abnormalities did not decrease until compression ratios of 1:200 or higher were used. Digital echocardiography loops, MPEG-1-compressed at an effective ratio of 200:1, demonstrate no degradation in endocardial visualization quality or diagnostic content. Compression at this ratio has the potential to reduce the storage size of digital echocardiography studies to less than 1% of their current size.

Echocardiography↗

PubMed2003

A randomised controlled trial comparing the use of manual versus mechanical compression to obtain haemostasis following coronary angiography.

Cardiac interventions have become a commonly accepted treatment option for patients with coronary heart disease. Managing the arterial puncture site and femoral sheath removal is an important aspect of cardiac nursing practice for patients who have had cardiac diagnostic and interventional procedures. The purpose of this study was to compare the use of manual compression with a mechanical compression device in achieving haemostasis after femoral sheath removal in coronary angiography patients and to determine the ability of these two techniques to reduce groin complications. A randomised controlled trial comparing two compression protocols (manual and QuicKlamp) was undertaken on a sample of 100 patients scheduled to have coronary angiography. Descriptive statistics were used to analyse and describe the data. Inter-group comparisons were analysed using either Chi-squared analysis for nominal data, or the Mann-Whitney U-test for continuous variables. The results indicated that the QuicKlamp device took longer to effect haemostasis after femoral sheath removal (P=0.000) and subjects took longer to mobilise than after manual compression (P=0.001). More haematomas occurred following manual compression after pressure dressing removal (P=0.027). At 5-day follow-up, more bruising was identified in those subjects in the QuicKlamp compression group (P=0.046), as was swelling in female subjects (P=0.044). More episodes of chest pain at 5-day follow-up were identified in the manual compression group (P=0.014). The findings demonstrate that QuicKlamp mechanical compression is a safe alternative to manual compression for attaining haemostasis after femoral sheath removal.

Adult↗