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PubMed1996

Inclusion of supine period in short-duration pH monitoring is essential in diagnosis of gastroesophageal reflux disease.

Prolonged esophageal pH monitoring is the most accurate method for detecting abnormal gastroesophageal reflux (GER) in patients with gastroesophageal reflux disease (GERD). However, some investigators have found that short-duration postprandial pH monitoring in the upright position is also useful, while others have failed to find such results. Therefore, we have compared a 6-hr period of pH monitoring (3-hr postprandial period after daytime meal and 3-hr supine period) with a total 24-hr period in detecting abnormal gastroesophageal reflux. Sixty-five patients (44 men, mean age 41.3 years) with GERD and 16 healthy volunteers (11 men, mean age 34.3 years) underwent 24-hr pH monitoring according to a standard protocol. Various reflux parameters during 24-hr pH monitoring were compared with reflux parameters during the 6-hr period. Abnormal GER was detected in 56 patients presenting with typical symptoms of GERD (sensitivity 86.2%). These patients could be further divided into upright (N = 18), supine (N = 15), and combined (N = 23) refluxers, depending on the posture in which abnormal reflux occurred. Esophageal pH monitoring during the 3-hr postprandial upright period showed abnormal reflux in only 35 patients (sensitivity 53.8%; P < 0.00005, compared with the 24-hr pH monitoring period). Abnormal GER was identified in 13 of 18 upright, 19 of 23 combined, and only one of 15 supine refluxers, as well as in two of nine patients with normal 24-hr pH-metry. However, inclusion of the 3-hr supine monitoring period in the 3-hr postprandial upright period improved detection of abnormal GER to 78.5% (51 patients; P = NS compared with 24-hr pH monitoring period). This was related mainly to improved detection of abnormal GER in supine refluxers (11 of 15; 73.3%). Esophageal acid exposure time correlated significantly with severity of esophagitis only during the total and supine periods of both the 24- and 6-hr periods and not during the upright period. Esophageal acid clearance correlated significantly with increasing grades of esophagitis for the supine and total periods only. We conclude that 3-hr postprandial pH monitoring, as has been conventionally practiced, is not appropriate in the detection of abnormal GER; inclusion of a supine period in the short-duration pH monitoring schedule increases the detection of pathological reflux. We therefore recommend that a supine period should be included in short-duration pH monitoring schedules. We also found that supine reflex was the most important factor in the development of esophagitis.

Adult↗
PubMed2001

What happens to the triangular fibrocartilage complex during pronation and supination of the forearm? Analysis of its morphology and diagnostic assessment with MR arthrography.

OBJECTIVE: To evaluate the dynamic morphologic changes of the triangular fibrocartilage complex (TFCC) during pronation and supination of the forearm using high-resolution MR arthrography in cadavers and to evaluate the impact of these changes on the diagnostic assessment of the normal and abnormal TFCC. DESIGN AND SPECIMENS: High-resolution MR arthrography of 10 wrists of cadaveric specimens was obtained in maximum pronation, in the neutral position, and in maximum supination of the forearm. The structures of the TFCC were evaluated by two musculoskeletal radiologists and correlated with anatomic sections. The position of the forearm that allowed the best visualization of normal structures and lesions of the TFCC was determined. RESULTS: The shape and extent of the articular disc as well as the radial portions of the radioulnar ligaments did not change with pronation and supination. The articular disc was horizontal in the neutral position and tilted more distally to align with the proximal carpal row in pronation and supination. The fibers of the ulnar part of the radioulnar ligaments (ulnar attachment of the articular disc) revealed the most significant changes: their orientation was coronal in the neutral position and sagittal in positions of pronation and supination. The ulnomeniscal homologue was largest in the neutral position and was reduced in size during pronation and supination. The extensor carpi ulnaris tendon was centered in its groove in the neutral position and pronation. In supination this tendon revealed subluxation from this groove. The dorsal capsule of the distal radioulnar joint was taut in pronation, and the palmar capsule was taut in supination. The preferred forearm position for analysis of most of the structures of the TFCC was the neutral position, followed by the pronated position. The neutral position was rated best for the detection of ulnar and radial detachments of the TFCC, followed by the pronated position, except for two central perforations of the TFCC which were best seen with supination. CONCLUSION: The articular disc and the surrounding radial portions of the radioulnar ligaments form a rigid, unified complex with the radius without change in their shape in positions of pronation and supination of the forearm, while the ulnar attachment of the TFCC shows important dynamic changes. The neutral forearm position is the best position to analyze both the normal and the abnormal TFCC.

Arthrography↗
PubMed1999

The supination effect of tendon transfer of the flexor carpi ulnaris to the extensor carpi radialis brevis or longus: a cadaveric study.

Flexor carpi ulnaris (FCU) transfer to the extensor carpi radialis brevis (ECRB) and/or the extensor carpi radialis longus (ECRL) has been commonly used to provide wrist extension. The ability of this wrist extension transfer to also provide forearm supination has been inferred but not formally investigated. This laboratory study investigated the forearm supination effect of FCU transfer to the ECRB and to the ECRL in a cadaveric model. Two vectors of pull were investigated: freeing either the distal one third or the distal two thirds of the FCU ulnar origin. Five fresh-frozen, above-elbow, non-matched cadaveric specimens placed in a mounting device that allowed the arm to rotate about its ulnar axis starting from a full pronated position were measured for resultant supination after tendon transfer and loading. This study showed that the transfer of the FCU into either the ECRB or the ECRL resulted in no significant difference in maximum supination. The vector of origin, however, did significantly affect the maximum supination obtained. Releasing the distal two thirds of the FCU ulnar origin resulted in a mean supination that was significantly greater than the mean supination achieved with releasing the distal one third of the FCU ulnar origin. We concluded that in the cadaveric model, transfer of the FCU into either the ECRB or ECRL provided similar resultant supination and that freeing the distal two thirds of the FCU ulnar origin provided significantly more supination than freeing only the distal one third. For the hand surgeon treating wrist flexion in combination with forearm pronation deformity, transfer of the FCU into the ECRB and/or the ECRL can be used to concomitantly provide wrist extension and forearm supination.

Cadaver↗
PubMed2006

Changes in vertebral wedging rate between supine and standing position and its association with back pain: a prospective study in patients with osteoporotic vertebral compression fractures.

STUDY DESIGN: Prospective consecutive series. OBJECTIVE: To analyze supine and standing radiographs and the association of back pain using subjective pain criteria. SUMMARY OF BACKGROUND DATA: It has been considered that there is little correlation between the degree of collapse of the vertebral body and the level of pain. In previous studies, however, measurements have only been based on supine radiographs. Although there were 2 authors who reported the results of supine lateral and standing lateral radiographs in patients with thoracolumbar vertebral fractures, as far as we know, there has not been any detailed report concerning the correlation between radiologic findings using supine and standing lateral radiographs and back pain. METHODS: We examined 100 consecutively treated patients, prospectively. Back pain and the supine and standing radiographs were assessed 1 month after injury. Changes in vertebral wedging rate (WR) from supine to standing position (Delta WR) was reported by the following equation: Delta WR = WR(standing)-WR(supine). RESULTS: The median age of the cohort was 75 years (range, 60-89 years). The median VAS of back pain at supine position, at standing position, and when standing erect was 13, 33, and 41, respectively. The median wedging rate on the supine and standing radiographs were 28% and 37%, respectively (P < 0.001). There was a significant correlation between Delta WR and back pain when standing erect (r = 0.79, P < 0.001). CONCLUSION: Changes in vertebral wedging rate between supine and standing position and its association with back pain may give a clue to the pathogenesis of pain from osteoporotic thoracolumbar vertebral compression fractures.

Aged↗
PubMed2006

Barriers to following the supine sleep recommendation among mothers at four centers for the Women, Infants, and Children Program.

OBJECTIVES: The risk for sudden infant death syndrome in black infants is twice that of white infants, and their parents are less likely to place them in the supine position for sleep. We previously identified barriers for parents to follow recommendations for sleep position. Our objective with this study was to quantify these barriers, particularly among low-income, primarily black mothers. DESIGN/METHODS: We conducted face-to-face interviews with 671 mothers, 64% of whom were black, who attended Women, Infants, and Children Program centers in Boston, Massachusetts, Dallas, Texas, Los Angeles, California, and New Haven, Connecticut. We used univariate analyses to quantify factors that were associated with choice of sleeping position and multivariate logistic regression to calculate adjusted odds ratios for the 2 outcome variables: "ever" (meaning usually, sometimes, or last night) put infant in the prone position for sleep and "usually" put infant in the supine position to sleep. RESULTS: Fifty-nine percent of mothers reported supine, 25% side, 15% prone, and 1% other as the usual position. Thirty-four percent reported that they ever placed infants in the prone position. Seventy-two percent said that a nurse, 53% a doctor, and 38% a female friend or relative provided source of advice. Only 42% reported that a nurse, only 36% a doctor, and only 15% a female friend or relative recommended the supine position for sleep. When a female friend or relative recommended the prone position, mothers were more likely ever to place their infants in the prone position and less likely usually to choose supine compared with those who received no advice from friends or relatives. When a doctor or a nurse recommended a nonsupine position, the mothers were less likely to choose supine compared with those who received no advice from a doctor or a nurse. Mothers who trusted the opinion of a doctor or a nurse about infant sleeping position were more likely to place their infants in the supine position. Half of the mothers believed that infants were more likely to choke when supine, and they were less likely to place their infants supine. Mothers who believed that infants are more comfortable in the prone position (36%) were more likely to place their infants prone. Twenty-nine percent believed that having their infants sleep with an adult helps prevent sudden infant death syndrome, and only 43% believed that sudden infant death syndrome is related to sleeping position. CONCLUSIONS: We identified specific barriers to placing infants in the supine position for sleep (lack of or wrong advice, lack of trust in providers, knowledge and concerns about safety and comfort) in low-income, primarily black mothers that should be considered when designing interventions to get more infants onto their back for sleep.

Adult↗
PubMed1991

[Effect of maternal postural change on maternal hemodynamics in late pregnancy--supine hypertension].

The purpose of this investigation was to ascertain the effect of postural change in late pregnant women from the left lateral recumbent position to the supine position on their blood circulation. Patients in whom the blood pressure at the right upper limb in the supine position increased by at least 20mmHg or more (diastolic and/or systolic pressure) were classified as the supine hypertensive group. Patients in whom the blood pressure of the right upper limb decreased by at least 20mmHg or more were classified as the supine hypotensive group. And other patients were classified as the no blood pressure change group. The results were as follows. 1. The incidence of supine hypertension was 48% in primigravidas and 38% in multigravidas. Supine hypertension was especially common in PIH (pregnancy induced hypertension) complicated women (75%). 2. Maternal cardiac function: With postural change from the left lateral recumbent position to the supine position, CO (cardiac output) decreased and SVR (systemic vascular resistance) was increased in both the supine hypertensive and the no blood pressure change groups by the thermodilution method (n = 14). CVP (central venous pressure) and PCWP (pulmonary capillary wedge pressure) shows different pattern of change in the supine hypertensive group and the no blood pressure change group. In the former group, CVP was decreased by 45 +/- 16% and PCWP was increased by 21 +/- 9% in the supine position compared with in the left lateral recumbent position. However, in the latter group, CVP decreased by 87 +/- 69% and PCWP decreased by 53 +/- 46% as the result of the same postural change.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed2000

The healthy human infant tends to sleep in the prone rather than the supine position.

There are few reports about developmental behavior relating to roll over among healthy infants. We assessed the relationship between the placed position on sleeping and altered sleeping position the next morning by roll over among healthy infants. A health check-up clinic distributed a total of 1626 questionnaires to parents whose infant's ages are 1.5 years (or 18 months) old. The age at the first roll over and the change in sleeping position the next morning after they started to roll over, were investigated. The mean age of roll over from the supine to the prone among infants who were placed mainly in the prone sleeping position, at least in the first week of life, was 4.0 months (S.D., 1.1). The mean age of roll over from the supine to the prone among infants who were placed mainly in the supine sleeping position during early neonatal life and thereafter was 4.4 months (S.D., 1.2). The age of the first roll over from supine to prone was significantly younger in infants who were placed mainly in the prone sleeping position during early neonatal life. Among 651 infants who had been placed supine, 34.7% were found prone by roll over the next morning. Among 211 infants who had been placed prone, 14.2% were found supine by roll over the next morning. The number of infants who rolled over from supine to prone position was statistically greater than those from prone to supine. It is likely that the healthy human infant tends to sleep in the prone rather than the supine position. The finding is especially important for the correct assessment of the position in which SIDS cases were found dead.

Humans↗
PubMed2004

Electromyographic activity and strength during maximum isometric pronation and supination efforts in healthy adults.

There exists a lack of quantitative data in the literature related to the torque produced during axial forearm rotation and the electromyographic (EMG) activity of the muscles involved. Therefore, the purpose of this study was to compare the relative EMG activity of four forearm muscles during resisted forearm rotation. A custom-built device capable of measuring torque in the absence of grip was employed. Fourteen healthy volunteers performed maximum isometric voluntary contractions in five positions of axial forearm rotation for both pronation and supination. EMG data were collected simultaneously from the supinator, biceps, pronator quadratus (deep and superficial heads), and pronator teres muscles using fine-wire bipolar electrodes. Data were analyzed to determine the contributions of each muscle to pronation and supination torque over five positions of forearm rotation. In the absence of grip no significant difference was found between supination and pronation torque in neutral position. Supination torque generation was greater in the pronated forearm positions, and pronation torque was greater in the supinated positions (p<0.05). A root-mean-square EMG analysis verified the major contributions of the pronator teres and both heads of the pronator quadratus muscle to pronation torque, and supinator and biceps to supination torque. The deep head of the pronator quadratus was active during both pronation and supination, lending support to the theory that it may act primarily as a dynamic distal radioulnar joint stabilizer. This information may be helpful in upper extremity modeling, surgical treatments, and rehabilitation strategies.

Adult↗
PubMed1998

Comparison of umbilical artery Doppler velocimetry between maternal supine position and complete left lateral position in predicting obstetric complications.

The aim of this study was to compare the predictive value of umbilical artery Doppler velocimetry in women in the supine position with that in women in the complete left lateral position as a screening test for abnormal obstetric outcomes. Umbilical artery resistance index (RI) was measured at 27-29 weeks and 35-37 weeks in 202 pregnant women. The measurements were performed with the mother in the supine position in 100 cases (supine group), and in the complete left lateral position in 102 cases (lateral group). Predictive values of the tests for abnormal outcomes (small for gestational age, fetal distress, pregnancy-induced hypertension) were compared between both groups. When abnormal RIs were defined as being greater than the 90th centile in the supine group, the sensitivities for any of the abnormal outcomes at 27-29 weeks were 18% in the supine group and 6% in the lateral group; the positive predictive values were 30% and 25%, respectively. For measurement at 35-37 weeks, the sensitivity and positive predictive value were 29% and 45%, respectively in the supine group, and 0% in both cases in the lateral group. When abnormal RIs were defined as being greater than the 90th centile in the lateral group, the sensitivities at 27-29 weeks were 41% in the supine group and 6% in the lateral group; the positive predictive values were 44% and 8%, respectively. At 35-37 weeks, the sensitivity and positive predictive value were 53% and 43% in the supine group, and 6% and 8% in the lateral group. Umbilical artery Doppler velocimetry when the mother was in the complete left lateral position was of little value as a screening test. However, when the mother is in the supine position, it may serve as a kind of stress test and disclose latent obstetric abnormalities in certain cases.

Adult↗
PubMed2003

Is there any difference in measurement of pelvic floor muscle strength in supine and standing position?

BACKGROUND: Traditionally, pelvic floor muscle function and strength have been measured in a supine position. However, stress urinary incontinence most often occurs in an upright position, and an important clinical question is whether measurement of pelvic floor muscle strength in the supine position reflects strength in standing. The purpose of the present study was to investigate whether there is a significant and clinical difference in pelvic floor muscle strength measurement in supine and standing position. METHODS: Eighteen women, mean age 43.4 years (range 31-64 years), with symptoms of stress and mixed incontinence attending a pelvic floor muscle-training program participated in the study. Measurement of pelvic floor muscle strength was conducted with a fiberoptic microtip transducer connected to a balloon catheter inserted into the vagina (Camtech AS, Sandvika, Norway). Measurement of resting pressure, maximum squeeze pressure, and holding period in seconds, were assessed in random order in supine and standing position. RESULTS: The mean difference between supine and standing resting pressure was 8.6 cmH2O (95% CI 4.9-12.3), p < 0.001, between supine and standing maximum strength 0.3 cmH2O (95% CI - 4.0 to 3.4), p = 0.884, and between supine and standing holding period 0.9 s (95% CI - 3.3 to 1.4), p = 0.409. CONCLUSION: Vaginal resting pressure was significantly higher in the standing compared to the supine position. Neither maximal strength nor holding time was different when comparing the two positions. Measurement of vaginal squeeze pressure is easier to perform and standardize in the supine compared to the standing position, and seems to reflect pelvic floor muscle strength in the standing position.

Adult↗
PubMed2001

The crura and crura-sphincter pressure dynamics in patients with isolated upright and isolated supine reflux.

The reason why patients with isolated supine reflux do not reflux in the upright position and patients with isolated upright reflux do not reflux in the supine position is unknown. Our objective was to determine the characteristics of the crura, lower esophageal sphincter, crura-sphincter dynamics, and esophageal body on manometry, endoscopy, and X-ray in patients with isolated upright and isolated supine reflux. Eighty consecutive patients with isolated upright reflux were compared with 82 consecutive patients with isolated supine reflux. Manometrically there was no difference in lower esophageal sphincter characteristics and esophageal contractions between the two groups. The prevalence of a hiatal hernia on manometry was similar between upright and supine refluxers (88% vs 88%). Upright refluxers had shorter hiatal hernias [median (interquartile range) 1.1 (0.65-1.8) vs 1.2 (1-2.3), P < 0.046)]. The median crural pressure, crura-sphincter pressure gradient, and crura-sphincter pressure ratio in upright refluxers was 14.96 (9.5-21.27), 3.28 (1.7-12.2), and 1.33 (0.87-2.8) mm Hg, respectively. These values were significantly higher (P < 0.001) in supine refluxers at 21.43 (16.6-29.9), 10.66 (4.3-19.7), and 2.1 (1.3-4.2) mm Hg, respectively. We conclude that the significantly higher crural pressure in patients with supine reflux acts as a mechanical ring and as a physiologic protector against the unfolding of the sphincter in the postprandial and upright periods. Higher crura-sphincter pressure gradient and larger-size hiatal hernias in patients with supine reflux results in pressurization of the hernia sac and subsequent reflux when these patients are in a supine position.

Esophagus↗
PubMed1994

Supine hypotensive syndrome.

OBJECTIVE: To review reports of the supine hypotensive syndrome with reference to clinical presentation, suggestions on the mechanism of onset, and the possibility of advance detection. DATA SOURCES: We used worldwide obstetric, anesthesia, and general medical journals from 1922 onward, a Medline search from 1966 onward, and manual cross-referencing for prior publications. METHODS OF STUDY SELECTION: We selected approximately 100 case reports of supine hypotensive syndrome and studies on supine blood pressure responses during late pregnancy. DATA EXTRACTION AND SYNTHESIS: Publications that recorded novel clinical observations, specific hemodynamic or biochemical measurements, or associated complications were included. CONCLUSIONS: Supine hypotensive syndrome is characterized by severe supine symptoms and hypotension in late pregnancy, which compel the unconstrained subject to change position. Rarely, it may manifest even from the fifth month of pregnancy or postpartum, as well as in the pelvic tilt or sitting positions. Although inferior vena cava compression, influenced primarily by the size of the uterus and exact maternal and fetal position, is the major determinant in its development, other factors may also be important in modulating the circulatory effects of such compression. Advance recognition of susceptibility to the syndrome depends on a history of severe supine symptoms or supine intolerance and an increase in maternal heart rate and decrease in pulse pressure in the supine position. As there seems to be a spectrum of severity from minimal central cardiovascular alterations to severe syncopal shock resulting from supine inferior vena cava compression, it is difficult to define a cutoff point at which the syndrome occurs. Although usually recognizable by maternal symptoms, severe hypotension without symptoms has been reported on three occasions.

Animals↗
PubMed2003

Quadriceps femoris torque and EMG activity in seated versus supine position.

PURPOSE: To compare voluntary and electrically evoked knee extensor torque, surface electromyography (EMG), and activation level obtained under seated versus supine position, i.e., with shortened versus lengthened rectus femoris (RF) muscle. METHODS: The knee extensor torque obtained during maximal voluntary contractions (MVC) and after single and paired stimuli applied at rest was measured under seated (i.e., 90 degrees hip angle) and supine (i.e., 180 degrees hip angle) conditions. The associated EMG activity from biarticular RF and monoarticular vasti was also recorded, and activation level was estimated by means of the twitch interpolation technique. RESULTS: Knee extensor MVC was 10.6% higher in the seated compared with the supine position (P < 0.01). EMG normalized to the M-wave amplitude for respective muscles and for respective positions was significantly lower under supine conditions, and deficits averaged approximately 20% for vasti and approximately 41% for RF (P < 0.05). Similarly, activation level estimated in the supine position was approximately 4% lower than the seated counterpart. Relative MVC losses observed supinely were significantly correlated with the corresponding activation level deficits (P < 0.05). On the other hand, both single and paired stimuli resulted in higher torque amplitudes in the supine with respect to the seated position, and mean differences were comprised between 10% (single twitch, P < 0.05) and 20% (potentiated doublet, P < 0.001). RF M-wave amplitude recorded supinely was 19% higher than the seated counterpart (P < 0.01). CONCLUSION: The higher neural activation observed for the knee extensor muscles in the seated versus supine position, likely attributable to improved motor unit recruitment, may reflect a neurophysiological mechanism partly compensating the neuromuscular transmission-propagation impairment and/or mechanical disadvantage of shortened RF muscle.

Adult↗
PubMed1992

Electromyography of pronators and supinators in great apes.

We obtained electromyographic recordings from the supinator, biceps brachii, pronator quadratus, and pronator teres muscles of a chimpanzee and a gorilla and from the supinator, pronator quadratus, and biceps brachii muscles of an orangutan as they stood and walked quadrupedally on horizontal and inclined surfaces, engaged in suspensory behavior, reached overhead, and manipulated a variety of foods and artifacts. In Pan troglodytes and Pan gorilla, as in Homo sapiens, the supinator muscle is the prime supinator, with the biceps brachii muscle serving to augment speed or force of supination. Primary of the pronator quadratus muscle over the pronator teres muscle during pronation is less clear in the African apes than in humans. Possibly, pongid radial curvature or forelimb elongation or both factors are related to the somewhat different patterns of activity that we observed in the pronator muscles of Pan versus those reported for Homo sapiens. In Pongo pygmaeus, as in P. troglodytes and P. gorilla, the pronator quadratus muscle acts as a pronator and the supinator muscle acts to supinate the hand at the radioulnar joints. The biceps brachii muscle is active at low levels as the orangutan supinates its hand with the elbow flexed.

Animals↗
PubMed2000

Difference in human cardiovascular response between upright and supine recovery from upright cycle exercise.

Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (fc) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions. The average fc at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis) in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line--mean R-R interval = 0.006 x HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in fc following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography) decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar to that at rest before exercise. The resultant cardiac output (Qc) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Qc were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated with fc, SV, Qc, and TPR during rest and recovery in different body positions.

Adult↗
PubMed2000

Patient positioning in prostate radiotherapy: is prone better than supine?

PURPOSE: To assess potential dose reductions to the rectum and to the bladder with three-dimensional conformal radiotherapy (3D-CRT) to the prostate in the prone as compared with the supine position; and to retrospectively evaluate treatment position reproducibility without immobilization devices. METHODS AND MATERIALS: Eighteen patients with localized prostate cancer underwent pelvic CT scans and 3D treatment planning in prone and supine positions. Dose-volume histograms (DVHs) were constructed for the clinical target volume, the rectum and the bladder for every patient in both treatment positions. "Comparative DVHs" (cDVHs) were defined for the rectum and for the bladder: cDVH was obtained by subtracting the organ volume receiving a given dose increment in the prone position from the corresponding value in the supine position. These values were then integrated over the entire dose range. The prescribed dose to the planning target volume (PTV) was 74 Gy using a 6-field technique. To evaluate reproducibility, portal films were subsequently reviewed in 12 patients treated prone and 10 contemporary patients treated supine (controls). No immobilization devices were used. Deviations in the anterio-posterior (X) and cranio-caudal (Y) axes were measured. Mean treatment position variation, total setup variation, systematic setup variation, and random setup variation were obtained. RESULTS: Prone position was associated with a higher dose to the rectum or to the bladder in 6 (33%) and 7 (39%) patients, respectively. A simultaneously higher dose to rectum and bladder was noted in 2 (11%) patients in prone and in 7 (39%) patients in supine. Rectal and bladder volumes were frequently larger in prone than in supine: mean prone/supine volume ratios were 1.21 (SD, 0.68) and 1.03 (SD, 1.32), respectively. In these cases cDVH analysis more often favored the prone position. Mean treatment position variation and total setup variation were similar for both prone and supine plans. A higher systematic setup variation was observed in prone positioning: 2.7 mm vs. 1.9 mm (X axis) and 4.1 mm vs. 2.2 mm (Y axis). The random variation was similar for both prone and supine: 4. 0 mm vs. 3.6 mm (X axis) and 3.7 mm vs. 3.6 mm (Y axis). CONCLUSIONS: Prone position 3D-CRT is frequently, but not always, associated with an apparent dose reduction to the rectum and/or to the bladder for prostate cancer patients. As suggested by the increased mean prone/supine rectal volume ratio, the advantage of prone positioning for the rectum may be artifactual, at least partly reflecting a position-dependent rectal air volume, which may significantly vary from treatment to treatment. In the absence of immobilization devices, daily setup reproducibility appears less accurate for the prone position, primarily due to systematic setup variations.

Aged↗
PubMed2002

Upper-limb surface electro-myography at maximum supination and pronation torques: the effect of elbow and forearm angle.

Forearm pronation and supination, and increased muscular activity in the wrist extensors have been both linked separately to work-related injuries of the upper limb, especially humeral epicondylitis. However, there is a lack of information on forearm torque strength at ranges of elbow and forearm angles typical of industrial tasks. There is a need for strength data on forearm torques at different upper limb angles to be investigated. Such a study should also include the measurement of muscular activity for the prime torque muscles and also other muscles at possible risk of injury due to high exertion levels during tasks requiring forearm torques.Twenty-four male subjects participated in the study that involved maximum forearm torque exertions for the right arm, in the pronation and supination directions, and at four elbow and three forearm rotation angles. Surface EMG (SEMG) was used to evaluate the muscular activity of the pronator teres (PT), pronator quadratus (PQ), biceps brachi (BB), brachioradialis (BR), mid deltoid (DT) and the extensor carpi radialis brevis (ECRB) during maximum torque exertions. Repeated measures ANOVA indicated that both direction and forearm angle had a significant effect on the maximum torques (p<0.05) while elbow angle and the interactions were highly significant (p<0.001). The results revealed that supination torques were stronger overall with a mean maximum value of 16.2 Nm recorded for the forearm 75% prone. Mean maximum pronation torque was recorded as 13.1 Nm for a neutral forearm with the elbow flexed at 45 degrees. The data also indicated that forearm angle had a greater effect on supination torque than pronation torque. Supination torques were stronger for the mid-range of elbow flexion, but pronation torques increased with increasing elbow extension. The strength profiles for the maximum torque exertions were reflected in the EMG changes in the prime supinators and pronators. In addition, the EMG data expressed as the percentage of Maximum Voluntary Electrical activity (MVE), revealed high muscular activity in the ECRB for both supination (26-43% MVE) and pronation torques (17-55% MVE). The results suggest that the ECRB acts as a stabiliser to the forearm flexors for gripping during pronation torques depending on forearm angle, but acts as a prime mover in wrist extension for supination torques with little effect of elbow and forearm angle. This indicates a direct link between forearm rotations against resistance and high muscular activity in the wrist extensors, thereby increasing stress on the forearm musculo-skeletal system, especially the lateral epicondyle.

Adult↗
PubMed2003

Renal and hormonal responses to isotonic saline infusion after 3 days' head-down tilt vs. supine and seated positions.

AIM: The study aimed to determine whether prolonged exposure to simulated microgravity produces a level of thoracic volume receptor loading similar to that seen in the upright position or immediately after lying down. METHODS: We used a cross-over design to compare responses to a saline infusion in eight healthy subjects during a 4-day, -6 degree head-down tilt (HDT) and in the acute seated and acute supine positions. RESULTS: The first 24 h of HDT were associated with greater urinary excretion of water and sodium (UV, UNaV) than seated and acute supine [cumulative UV, 3035 +/- 219, 2311 +/- 156 (P < 0.05), and 2448 +/- 182 mL (P < 0.05), respectively; cumulative UNaV, 256 +/- 19, 180 +/- 11 (P < 0.05), and 189 +/- 15 mmol (P < 0.05), respectively]. Haemoglobin and haematocrit were increased after 24 h and plasma volume decreased after 48 h of HDT (P < 0.05). With prolongation of HDT, UV and UNaV returned near the baseline values, and plasma atrial natriuretic factor (ANF) and renin values returned to acute seated levels; in acute supine, ANF values were higher and renin lower than in the two other positions. After a 30-min infusion of 20 mL kg(-1) isotonic saline on the fourth HDT day or during acute seated or acute supine, sodium excretion within 4 h was similar during HDT and acute seated (83 +/- 6 and 84 +/- 9 mmol, respectively) and greater during supine (104 +/- 8 mmol, P < 0.05). The renin decrease was greater in HDT and seated than in supine. The plasma ANF increase was greater during HDT than during supine; during seated, plasma ANF was unchanged. CONCLUSION: These data suggest that, after 4 days of HDT, thoracic volume receptor loading returns to the same level as in the seated position, leading to blunted responses to volume expansion as compared with the acute supine position.

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