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PubMed2003

Physical properties and compact analysis of commonly used direct compression binders.

This study investigated the basic physico-chemical property and binding functionality of commonly used commercial direct compression binders/fillers. The compressibility of these materials was also analyzed using compression parameters derived from the Heckel, Kawakita, and Cooper-Eaton equations. Five classes of excipients were evaluated, including microcrystalline cellulose (MCC), starch, lactose, dicalcium phosphate (DCP), and sugar. In general, the starch category exhibited the highest moisture content followed by MCC, DCP, lactose, and finally sugar; DCP displayed the highest density, followed by sugar, lactose, starch, and MCC; the material particle size is highly processing dependent. The data also demonstrated that MCC had moderate flowability, excellent compressibility, and extremely good compact hardness; with some exceptions, starch, lactose, and sugar generally exhibited moderate flowability, compressibility, and hardness; DCP had excellent flowability, but poor compressibility and hardness. This research additionally confirmed the binding mechanism that had been well documented: MCC performs as binder because of its plastic deformation under pressure; fragmentation is the predominant mechanism in the case of lactose and DCP; starch and sugar perform by both mechanisms.

Cellulose↗

PubMed1986

External pneumatic calf compression reduces deep venous thrombosis in patients with ruptured intracranial aneurysms.

We evaluated the ability of intermittent external pneumatic calf compression to prevent deep venous thrombosis after subarachnoid hemorrhage from ruptured intracranial aneurysms. Fifty-six subarachnoid hemorrhage patients not given external pneumatic calf compression were compared with 90 patients who had calf compression after their subarachnoid hemorrhages. Both groups of patients were on strict bedrest for 7 to 21 days after aneurysm rupture, and both received epsilon-aminocaproic acid, 30 to 36 g/day intravenously, until operation. The risk factors in the two groups were similar, and the nursing and medical care did not seem to differ. Of patients without external pneumatic compression, 18% had venographically proven deep venous thrombi, which contrasts with 6% of patients receiving calf compression. This was a significant difference (P less than 0.05; chi 2). These retrospective data suggest that external pneumatic calf compression helps to prevent deep venous thrombosis in patients with subarachnoid hemorrhage when delayed operation, bedrest, and antifibrinolytic agents are used.

Adult↗

PubMed1994

Changes in systemic blood pressure and cardiac rhythm induced by therapeutic compression of the trigeminal ganglion.

Percutaneous compression of the trigeminal ganglion, which is currently being used for the control of trigeminal neuralgia, induces marked intraoperative elevations of the systemic blood pressure and heart rate changes, which may increase the risk of cardiovascular complications. We have analyzed the characteristics of the arterial hypertensive response and the cardiac rhythm changes induced by percutaneous compression of the trigeminal ganglion in 42 consecutive, unselected patients undergoing operations for essential trigeminal neuralgia under three different regimens of anesthesia. The first 22 patients (Group 1) underwent operations under brief general anesthesia without endotracheal intubation. The following 10 patients (Group 2) had general anesthesia with intubation and mechanical ventilation and received larger doses of hypnotic and analgesic agents. Finally, 10 more patients (Group 3), who had general anesthesia with intubation, underwent local anesthetic blockade of Meckel's cave (injection of 1 ml of 1% lidocaine) before ganglion compression. Foramen ovale puncture elicited bradycardia in the majority of the patients of Groups 2 and 3, but only four patients (18%) of Group 1 showed bradycardia. Ganglion compression caused marked tachycardia in all patients of Groups 1 and 2; about one-third of the patients also had extrasystoles. By contrast, patients of Group 3, who had local anesthetic blockade of Meckel's cave before ganglion compression, did not develop tachycardia or extrasystoles. Foramen ovale puncture elicited marked elevations of the systemic blood pressure in all patients. Ganglion compression further increased blood pressure, except in patients of Group 3, who had local anesthetic blockade of Meckel's cave.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2004

Trochlear nerve palsy after repeated percutaneous balloon compression for recurrent trigeminal neuralgia: case report and pathogenic considerations.

OBJECTIVE AND IMPORTANCE: Repeated percutaneous balloon compression for the treatment of idiopathic trigeminal neuralgia is infrequent. When a second procedure is performed, the outcome is unknown. A patient developed an isolated trochlear nerve palsy after undergoing percutaneous trigeminal ganglion balloon compression for a second time. The mechanism of diplopia and the complications associated with this technique were studied. CLINICAL PRESENTATION: The patient was a 67-year-old woman with a history of medically refractory idiopathic trigeminal neuralgia involving all three divisions of the right trigeminal nerve. INTERVENTION: Percutaneous balloon compression was performed. Despite initial total relief from pain without complications, the patient again displayed manifestations of trigeminal neuralgia 3 months after the procedure. The pain disappeared after she underwent a second balloon compression procedure, but she developed an isolated trochlear nerve palsy, which spontaneously resolved in 2 months. CONCLUSION: Isolated trochlear nerve palsy is a rare and reversible complication after percutaneous balloon compression for trigeminal neuralgia. This case illustrates that the mechanism of injury to the fourth nerve is the result of an erroneous technique: excessive penetration of the Fogarty catheter in Meckel's cave beyond the porus trigemini and compression of the cisternal segment of the trochlear nerve when the inflated balloon is pushed against the tentorium.

Aged↗

PubMed1998

Compressive force promotes sox9, type II collagen and aggrecan and inhibits IL-1beta expression resulting in chondrogenesis in mouse embryonic limb bud mesenchymal cells.

The initial modeling and subsequent development of the skeleton is controlled by complex gene-environment interactions. Biomechanical forces may be one of the major epigenetic factors that determine the form and differentiation of skeletal tissues. In order to test the hypothesis that static compressive forces are transduced into molecular signals during early chondrogenesis, we have developed a unique three-dimensional collagen gel cell culture system which is permissive for the proliferation and differentiation of chondrocytes. Mouse embryonic day 10 (E10) limb buds were microdissected and dissociated into cells which were then cultured within a collagen gel matrix and maintained for up to 10 days. Static compressive forces were exerted onto these cultures. The time course for expression pattern and level for cartilage specific markers, type II collagen and aggrecan, and regulators of chondrogenesis, Sox9 and IL-1beta, were analyzed and compared with non-compressed control cultures. Under compressive conditions, histological evaluation showed an apparent acceleration in the rate and extent of chondrogenesis. Quantitatively, there was a significant 2- to 3-fold increase in type II collagen and aggrecan expression beginning at day 5 of culture and the difference was maintained through 10 days of cultures. Compressive force also causes an elevated level of Sox9, a transcriptional activator of type II collagen. In contrast, the expression and accumulation of IL-1beta, a transcriptional repressor of type II collagen was down-regulated. We conclude that static compressive forces promote chondrogenesis in embryonic limb bud mesenchyme, and propose that the signal transduction from a biomechanical stimuli can be mediated by a combination of positive and negative effectors of cartilage specific extracellular matrix macromolecules.

Aggrecans↗

PubMed1994

Effects of compression pressure on physical and chemical stability of tablets containing an anticancer drug TAT-59.

(E)-4-[1-[4-[2-(Dimethylamino)ethoxy]phenyl]-2-(4-isopropyl) phenyl]-1-butenyl]phenyl monophosphate (TAT-59) is a new drug for the treatment of breast cancer. Physical and chemical stability of mixtures of TAT-59 and microcrystalline cellulose (1:9) compressed at 0, 300, 600 and 1400 kg/cm2 was evaluated by determination of water content, porosity and the amount of hydrolysis product, DP-TAT-59, formed. The water contents and porosity of these tablets scarcely changed during 57 d at 25-60 degrees C under 50% relative humidity (RH). The degradation rate of TAT-59 increased with increasing compression pressure as well as temperature. The apparent activation energy and frequency factor were determined from an Arrhenius plot of the degradation rate. Activation energy of these tablets was almost the same, while the frequency factor tended to increase with increasing compression pressure. The porosity and pore sizes in TAT-59-containing tablets decreased with increasing compressive force. We speculated from these observations that the increase in compression pressure decreased the distance and increased the contact area between TAT-59 and microcrystalline cellulose. The proximity between TAT-59 and moisture presented at the surface of microcrystalline cellulose by compression was considered to enhance the degradation of TAT-59.

Antineoplastic Agents↗

PubMed1992

[The effect of stationary time of punch in the process of compression on dividing properties of scored tablets].

The significance of the stationary time of punch in the process of compression on the dividing properties of scored tablets was investigated in several tablets prepared from lactose, corn starch, hydroxypropyl starch, synthetic aluminum silicate, microcrystalline cellulose or Perfiller. The dividing strength of scored tablets was not affected by the stationary time of punch. The effect of the stationary time of punch on the coefficient of variation of divided tablet weight differed in the compacting characteristics and compaction profiles of powders. In case of tablets prepared from microcrystalline cellulose, the effect of stationary time of punch was not observed. However, in the other excipients, there existed a specific stationary time of punch to minimize the coefficient of variation of divided tablet weight. The time was different due to the change of compression pressure. The coefficient of variation of divided tablet weight showed minimum at the longer stationary time of punch when tablets were compressed at the low compression pressure, and the time showed a tendency to become short with the increase of compression pressure. These results suggested that the effect of the stationary time of punch on the coefficient of variation of divided tablet weight was concerned with the compaction structure of powders produced by the movement of punch in the process of compression.

Pressure↗

PubMed2000

Diagnosis of glaucoma using telemedicine--the effect of compression on the evaluation of optic nerve head cup-disc ratio.

A photograph of the optic nerve head requires a lot of disk space (over 1 MByte) for storage and may require substantial bandwidth and time for transmission to a remote practitioner for a second opinion. To test whether compression degrades the image quality of the images, 302 slides were digitized at an optical resolution of 2400 pixels/inch (945 pixels/cm) and 30 bit/pixel. The images were saved both in non-compressed TIFF format and in compressed JPEG (compression ratio of 60) format. A blinded observer measured the optic nerve head cup-disc ratio for all three groups: the original slides, uncompressed TIFF and compressed JPEG images. The results showed that digital images were less accurate than slides. However, compression, even up to a ratio of 40, did not make matters worse.

Glaucoma↗

PubMed2004

Effect of graduated compression stockings on limb oxygenation and venous function during exercise in patients with venous insufficiency.

Despite the established role of compression as the basis for nonoperative treatment of chronic venous insufficiency (CVI), its mechanism of action remains unclear. Near-infrared spectroscopy (NIRS) provides continuous noninvasive monitoring of changes in tissue oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb). We applied NIRS to evaluate the effect of graded stockings on venous function and calf muscle oxygenation during exercise in patients with CVI. Ten patients (age 56 +/- 5 years) with CVI were rested in supine posture for 20 minutes. NIRS optodes were attached to the calf. Venous function was assessed in each patient with and without graded compression stockings (classes I to III) at rest in the supine position, standing, with 10 tiptoe exercises, and on standard walking at 1.6 km/h for 5 minutes. Venous function was assessed by measuring changes in Hb and total hemoglobin (HbT) during the test, and muscle oxygenation was assessed by the oxygenation index (HbD), which is the difference between HbO2 and Hb. Standing without stockings caused a significant increase in Hb concentration by 10.75 +/- 2.24 micromol/L compared with the supine position (p < .001). This value was reduced when stockings were applied to 6.38 +/- 2.75 micromol/L with class III stockings (p = .005). During tiptoe exercise, the residual Hb concentration value without stockings was 7.62 +/- 2.12 micromol/L compared with 5.88 +/- 2.87, 3.77 +/- 3.37, and 3.46 +/- 2.73 micromol/L for class I, II, and III stockings, respectively. The reduction in Hb concentration reached significance with class II and III stockings compared to without stockings (p = .04). The HbT concentration was also reduced during tiptoe exercise, with increasing compression from 15.46 +/- 5.31 micromol/L without compression to 11.52 +/- 4.26 pmol/L with class III stockings (p = .048). During walking, the Hb concentration was 11.40 +/- 3.10 pmol/L without stockings, decreasing significantly (p < .001) and progressively to 8.49 +/- 3.24, 7.71 +/- 3.51, and 6.89 +/- 3.16 micromol/L with class I, II, and III stockings, respectively. Limb oxygenation (as measured by HbO2 concentration) during walking exercise, however, increased with higher-compression stockings and reached significance with class III stockings only (p = .03). In patients with venous insufficiency, graduated compression stockings may achieve their beneficial effects by reducing venous pooling and improving deeper tissue oxygenation.

Adult↗

PubMed1991

The most advantageous timing of external ureteric compression during intravenous urography.

The objective of this study was to ascertain the most advantageous time during an intravenous urogram to apply external ureteric compression to gain the greatest calyceal distension. This was a prospective randomized trial of 60 patients, divided into three equal groups with compression applied immediately after injection, at 5 minutes and after the 5 minutes film had been viewed. Patients with the usual criteria for avoiding compression were excluded. A statistically significant improvement in calyceal distension occurred when compression was applied at 5 minutes compared with that applied after the 5 minute film had been viewed. No improvement was seen when the compression was applied immediately after injection. We recommend that external ureteric compression should be applied immediately after the 5 minute film.

Humans↗

PubMed2003

Effect of data compression on proximal caries detection: observer performance with DenOptix photostimulable phosphor images.

OBJECTIVES: To study the effect of lossy image compression on caries detection. Null hypothesis states no difference in caries detection efficacy among observers using original digital images versus images compressed at various rates of compression. METHODS: Digital images of 41 extracted posterior teeth were obtained with a storage phosphor DenOptix (Gendex DenOptix Imaging system) system. Images were exported in Tagged Image File Format (TIFF) and compressed with Joint Photographic Experts Group File Interchange Format (JFIF), as provided by the software of the imaging system. The compressions options JFIF100%, JFIF75% and JFIF50% resulted in reducing the image size to 1:2, 1:11 and 1:16, respectively. Eight observers evaluated the presence or absence of caries on a 5-point confidence scale. The actual caries status of each proximal surface was determined by ground section histology. Responses were evaluated by receiver operating characteristic (ROC) analysis. Areas under the curves (Az) were assessed using analysis of variance (ANOVA). RESULTS: The mean Az scores were 0.85 for original/uncompressed images, and 0.89 for JFIF100%, 0.88 for JFIF75% and 0.88 for JFIF50% images. These differences were not statistically significant (P = 0.26). Differences between observers were also not statistically significant (P = 0.12). CONCLUSIONS: JFIF compression at the level of 1:16 can be used without significant deterioration in diagnostic accuracy for proximal caries detection.

Analysis of Variance↗

PubMed2001

Venous haemodynamics and the effects of compression stockings.

Over the years, graduated compression stockings exerting varying ankle pressures have been used with differing degrees of effectiveness in the prevention of deep venous thrombosis and ulcer recurrence, and the treatment of venous ulceration (Stemmer et al, 1980; Partsch and Horakova, 1994; Veraart et al, 1997). Whether in the hospital or community setting, nurses often have the responsibility of measuring the limb and fitting the compression stocking on the patient and it is he/she who often influences the patient on the type of stocking and level of compression required. Understanding the influence of graduated compression on the venous haemodynamics of the lower limb and having a good working knowledge of the claims of the manufacturers as to expected levels of compression from each garment will aid the nurse and patient in decision making. An awareness of the hazards of inappropriate use of compression therapy should ensure that the nurse is a safe practitioner.

Bandages↗

PubMed2003

How effective is training in compression bandaging techniques?

The aim of this review was to investigate whether formalized compression bandage training is required for nurses to achieve compression bandaging of high quality, that is bandaging which produces sustained graduation from toe to knee. Medline, CINAHL and Embase databases were used in the search. Randomized controlled trials and quasi-experimental trials were included where (at a minimum) nurses experienced in compression bandaging had their skills reviewed before and after training, and then reviewed once more at a later follow-up session. Three studies matched these criteria. In all three, nurses in general did not achieve sustained graduated compression before training, despite being defined as experienced bandagers. There was a substantial improvement in bandaging skills immediately following training. Two trials found that this improvement was sustained for between 2 and 4 weeks. The results of the third study suggested that improvements might not be sustained in the longer term. This review raises issues for further research including the current standard of compression bandaging, by those individuals who consider themselves competent in this skill. In addition, there needs to be argument on how nurses' bandaging skills can be improved and maintained, including the depth of role of feedback. In the meantime, nurses need to be as diligent as possible in maintenance of their compression bandaging skills, and the training they give junior staff. The effectiveness of current training cannot be assessed by short-term improvements and must not be assumed.

Bandages↗

PubMed2000

When is reduced-compression bandaging safe and effective?

During a one-year period 44 patients were treated with reduced-compression bandaging in the vascular unit at a district general hospital. Twenty patients with venous ulcers were referred from community leg ulcer clinics because they could not tolerate standard compression bandaging (group 1). A further 24 patients had mixed aetiology leg ulcers (group 2), and high-compression bandaging was not attempted because of significant peripheral vascular disease (ankle brachial pressure index < 0.8). Forty-two patients tolerated reduced-compression bandaging without discomfort or skin pressure changes. Healing was achieved in 32 patients (13 in group 1 and 19 in group 2). All non-healed ulcers were considered smaller at the time of final follow-up, and had less exudate. Reduced-compression bandaging has been shown to be effective and well tolerated by patients with venous ulcers who cannot comply with high-compression bandaging. With close supervision, it is safe to use in patients with significant peripheral vascular disease.

Adult↗

PubMed2004

An evaluation of Hyalofill-F plus compression bandaging in the treatment of chronic venous ulcers.

OBJECTIVE: Hyaluronan, a component of the extracellular matrix, plays a significant role in several aspects of tissue repair and the wound healing process. METHOD: In this Italian study Hyalofill-F, a partial benzyl ester derivative of hyaluronan, used in combination with compression bandaging, was compared with the well-established therapy in Italy of non-adherent gauze plus compression therapy in the treatment of chronic venous leg ulcers. RESULTS: Hyalofill-F plus compression bandaging performed significantly better than non-adherent gauze plus compression bandage in all of the clinically relevant efficacy parameters. Mean reduction in ulcer area in the hyaluronan-derivative group was 8.1 cm2 after eight weeks of treatment, compared with 0.4 cm2 in the comparator group. The resulting difference of 7.7 cm2 between the two groups was statistically significant (p = 0.0019). Furthermore, statistically significant results in favour of the hyaluronan-derivative group were obtained in the following: speed of epithelialisation; leveling of the margins; degree of maceration; pain intensity and frequency. CONCLUSION: Hyalofill-F plus compression bandaging resulted in an earlier and greater decrease in ulcer area compared with non-adherent gauze plus compression bandaging, therapy supporting its use in the treatment of chronic venous ulcers.

Adjuvants, Immunologic↗

PubMed1998

A new provocative test for carpal tunnel syndrome. Assessment of wrist flexion and nerve compression.

To establish the value of median nerve compression with wrist flexion as a provocative test for carpal tunnel syndrome (CTS), we performed a prospective study of 64 patients (95 hands) with CTS confirmed by electrodiagnostic studies and 50 normal subjects (96 hands). We recorded results for the common provocative tests (Tinel's percussion test, Phalen's wrist flexion test and the carpal compression test) and the new test which combines wrist flexion with median nerve compression. Using a receiver operator characteristic curve (ROC) technique, we found that the optimal cut-off time for the wrist-flexion and median-nerve compression test was 20 s, giving a sensitivity of 82% and a specificity of 99%. These results were significantly better than for Phalen's wrist flexion test (61% and 83%, respectively) and for the sensitivity of Tinel's test (74%). The positive predictive values of the wrist flexion and median-nerve compression test, which is more important clinically, were 99%, 95% and 81% at population prevalences of 50%, 20% and 5%, respectively. These were significantly better than those of the three other provocative tests at each prevalence. Electrodiagnostic studies have significant false-positive and false-negative rates in CTS, and therefore provocative tests remain important in its diagnosis. We have shown that wrist flexion combined with the median-nerve compression test at 20 s, is significantly better than the other methods, and may thus be clinically useful.

Adult↗

PubMed1992

Extracorporeal circulation as an alternative to open-chest cardiac compression for cardiac resuscitation.

Open-chest direct cardiac compression represents a more potent but highly invasive option for cardiac resuscitation when conventional techniques of closed-chest cardiac resuscitation fail after prolonged cardiac arrest. We postulated that venoarterial extracorporeal circulation might be a more effective intervention with less trauma. In the setting of human cardiac resuscitation, however, controlled studies would be limited by strategic constraints. Accordingly, the effectiveness of open-chest cardiac compression was compared with that of extracorporeal circulation after a 15-min interval of untreated ventricular fibrillation in a porcine model of cardiac arrest. Sixteen domestic pigs were randomized to resuscitation by either peripheral venoarterial extracorporeal circulation or open-chest direct cardiac compression. During resuscitation, epinephrine was continuously infused into the right atrium, and defibrillation was attempted by transthoracic countershock at 2-min intervals. Systemic blood flows averaged 198 ml.kg-1.min-1 with extracorporeal circulation. This contrasted with direct cardiac compression, in which flows averaged only 40 ml.kg-1.min-1. Coronary perfusion pressure, the major determinant of resuscitability on the basis of earlier studies, was correspondingly lower (94 vs 29 mm Hg). Extracorporeal circulation, in conjunction with transthoracic DC countershock and epinephrine, successfully reestablished spontaneous circulation in each of eight animals after 15 min of untreated ventricular fibrillation. This contrasted with the outcome after open-chest cardiac compression, in which spontaneous circulation was reestablished in only four of eight animals (p = .038). We conclude that extracorporeal circulation is a more effective alternative to direct cardiac compression for cardiac resuscitation after protracted cardiac arrest.

Acidosis↗

PubMed1994

Reliability of the radial arterial pressure during anesthesia. Is wrist compression a possible diagnostic test?

STUDY OBJECTIVE: To evaluate wrist compression as a test to identify low radial from low systemic pressure and to see if the gradient found after cardiopulmonary bypass is also present whenever hand vascular resistance may decrease. DESIGN: This was a prospective study. SETTING: Operating room area of a university medical center. PARTICIPANTS: (1) Forty patients undergoing coronary bypass grafting studied at discontinuation of cardiopulmonary bypass. (2) Twenty-six patients received isoflurane anesthesia before major noncardiac operations. (3) Hydraulic model: a fluid container with a tube 66-cm long, 6- to 1.8-mm internal diameter, connected at its base. INTERVENTIONS: Before induction of anesthesia, the radial artery was cannulated and, in the first group, the aorta or femoral arteries as well. The radial pressure was compared consecutively with and without wrist compression. In the model, the pressure was recorded simultaneously at three sites along the tube while different flows ran through its distal end. MEASUREMENTS AND RESULTS: Overall, wrist compression increased radial (p < 0.001) systolic, diastolic, and mean arterial pressures. In the first group, compression reduced the femoral/aortic-radial mean pressure difference by 50 percent and never produced higher radial than central mean pressure. Plot of the pressure difference produced by wrist compression against the average of the (compared) radial pressures and considering increases > or = 4 mm Hg as real, showed that, in the first group, systolic arterial pressure (SAP) increased 13 +/- 1.4 mm Hg in 22 of 40 patients; diastolic arterial pressure (DAP) increased 7.8 +/- 1.1 mm Hg in 4; and mean arterial pressure (MAP) increased 7.7 +/- 1.6 mm Hg in 9 patients. In the second group, SAP increased 16.0 +/- 1.7 mm Hg in 24 of 26 patients, DAP increased 6.0 +/- 1.4 mm Hg in 5, and MAP increased 7.0 +/- 0.7 mm Hg in 18 of 26 patients. In the model, base pressure at 94 mm Hg, the pressures were 1.2 to 28.1 mm Hg lower for flows ranging from 10 to 122 ml/min at the 54-cm distance (wrist equivalent). CONCLUSION: The systemic-radial artery pressure gradient seen at the end of cardiopulmonary bypass seems to be a phenomenon common to patients with decreased hand vascular resistance. Wrist compression decreases or abolishes the gradient in most cases. It does not produce false positives, so an increase indicates a greater aortic than radial pressure. The difference is likely to be only temporary.

Anesthesia, General↗