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PubMed1994

Effects of wearing compression stockings on cardiovascular responses.

To investigate the effects of wearing compression stockings on cardiovascular responses, the heart rate (HR), cardiac output (Q) measured by CO2 rebreathing method, and oxygen intake were measured at rest in a supine position for 40 min and standing position for 120 min. Six female subjects wore the compression stockings after 20 min of rest at supine position. The oxygen intake and ventilation showed no significant difference between with and without the stockings. Q at standing position was lower than that at supine position by an act of hydrostatic pressure. However this decrease was lower with stockings than that without stockings. The compression stockings used in this study might improve the venous return to the heart. However, the subjects complained of discomfort due to the high clothing pressure. In the second experiment, the authors estimated the minimum pressure required in improving the venous return. The subjects wore the trousers having two bladders inflated by air pressure. The trousers could compress the leg (contain the foot) and thigh individually. From the relationship between air pressure and Q, the estimated minimum pressures were 17 mmHg for the leg and 15 mmHg for the thigh.

Bandages↗

PubMed1998

Venous air embolism in sitting and supine patients undergoing vestibular schwannoma resection.

OBJECTIVE: This study retrospectively compares the incidence of venous air embolism (VAE) detection and morbidity in the sitting and supine positions. All patients underwent vestibular schwannoma resection via the retrosigmoid approach by a single surgical team. METHODS: A total of 432 consecutive operations were reviewed, 222 of which were performed with the patients in the sitting position and 210 of which were performed with the patients in the supine position. Charts were reviewed for evidence of intraoperative VAE, intraoperative hypotension secondary to VAE, postoperative morbidity related to VAE, and other variables to compare the groups. RESULTS: This study demonstrated a 28% incidence of VAE detection when patients were in the sitting position compared to a 5% incidence of VAE detection when patients were in the supine position (P < 0.0001). Intraoperative hypotension secondary to VAE was noted in 1.8% of the sitting patients and 1.4% of the supine patients (P=0.72, no significant difference). Postoperative morbidity caused by VAE was noted in one sitting patient (0.5%) (pulmonary edema) and in no supine patients (P=0.48, no significant difference). Blood loss was slightly greater in the supine group, and operative times were similar in both groups, despite that the average tumor size of patients operated on in the sitting position was 2.8 cm versus 2.2 cm in the supine group (P < 0.0001). CONCLUSION: Our results indicate that although there is a higher incidence of VAE detection in sitting patients, the morbidity is not statistically greater. We conclude that because morbidity from VAE is similar in either position, patient positioning should be based on surgical team preference.

Cerebral Veins↗

PubMed1994

Preoperative duplex venous mapping: a comparison of positional techniques in patients with and without atherosclerosis.

PURPOSE: Preoperative duplex venous mapping is the preferred modality to measure the diameter of the greater saphenous vein and its suitability as an arterial conduit for infrainguinal bypass. We wanted to determine the optimal mapping technique and maximal venous diameter in patients with and without atherosclerosis. METHODS: Three groups of patients were prospectively studied: younger control subjects (n = 20), preoperative atherosclerotic patients (n = 10), and older control subjects (n = 10). All patients underwent greater saphenous vein duplex mapping in a standardized manner. Maximal internal vein diameters were measured with the subjects in the supine position in bed, in the 20 degree reversed Trendelenburg position, sitting on the edge of the bed, standing, and in the supine position with a high-thigh, low-pressure tourniquet. Measurements were taken just beyond the saphenofemoral junction, in the distal thigh, below the knee, at midcalf, and superior to the medial malleolus. RESULTS: In younger control subjects an increasingly more erect position resulted in progressively larger measured vein diameters at all levels along the length of the leg. Both patients with atherosclerosis and older control subjects had no such increase in venous diameter with any positional change from the supine position to standing. Patients with atherosclerosis also had significantly smaller measured veins than either younger or older control subjects. A high-thigh tourniquet significantly increased vein diameters in the atherosclerotic group to the size of vein diameters in the older control group, although the absolute size differences were not large. CONCLUSIONS: The optimal position for venous mapping is with the patient in a supine position. If the internal vein diameter is below an acceptable minimum size, a high-thigh tourniquet will maximally distend the vein in patients with atherosclerosis. Vein diameter decreases with age and is less distended in patients with atherosclerosis compared with older patients without atherosclerosis.

Adult↗

PubMed2004

Use of preoperative assessment of positionally induced cyclotorsion: a video-oculographic study.

PURPOSE: Positionally induced cyclotorsion could be an important factor concerning correction of astigmatism in refractive surgery. The method of binocular three dimensional infrared video-oculography (3D-VOG) was used to determine a possible influence of body position on cyclotorsion. METHODS: 38 eyes (19 healthy subjects, median value of age 25.5) with normal binocular vision were examined using 3D-VOG. This method records ocular motions and positions of both eyes simultaneously in the x, y, and z axis. Cycloposition of the eyes was recorded first in a seated position (both eyes open, test 1), then in a supine position (right eye closed, test 2), occlusion of both eyes (test 3), both eyes open (test 4). Cyclovergence was calculated as the difference between the right and the left eye positions. RESULTS: The range of cyclotorsion of the right and left eye in all four tests was between 1.13 degrees excyclotorsion and 0.34 degrees incyclotorsion. There was no statistically significant difference of the median values for torsion for the four test situations. Concerning the influence of body position on cyclotorsion, a statistically significant difference between the different test positions and settings did not exist. Median values for right/left torsion/cyclovergence were: 0.17/0.04/0.02 (test 1), -0.31/-0.71/-0.16 (test 2), -1.09/-0.60/0.82 (test 3), 0.28/0.28/-0.82 (test 4). CONCLUSIONS: Cyclotorsion does not significantly change between seated and supine position in subjects with normal binocular vision and stable fixation. In these subjects, an erroneous refractive surgery due to incorrect measurement of the axis of astigmatism in the seated position and performing the refractive surgery in the supine position, is very unlikely.

Adult↗

PubMed1987

Effects of sitting position on uterine activity during labor.

To determine which components of uterine activity are affected by different positions of labor, 116 intrauterine pressure records in the sitting and supine positions were analyzed in order to measure resting, contraction, and bearing down pressures. The resting pressure in the sitting position showed consistent elevation compared to the supine position, while the contraction pressure did not differ strikingly in the two positions. The bearing down pressure in the sitting position for nulliparas during the second stage and for multiparas at the time of the 8- to 10-cm dilation was significantly higher than that in the supine position. Also, the sitting position led to a significantly shorter duration of the second stage in nulliparas and the 5- to 10-cm dilation period in multiparas. These findings suggest that the maternal position does not affect uterine contractility, that the increased resting pressure in the sitting position is of some importance in supplementing the downward delivery force, and that the increased bearing down pressure in the sitting position could help to significantly shorten the duration of labor.

Female↗

PubMed2002

Effects of sodium intake on cardiovascular variables in humans during posture changes and ambulatory conditions.

The hypothesis was tested that cardiac output (CO) and stroke volume (SV) are increased by a moderate physiological elevation in sodium intake with a more pronounced effect in the ambulatory upright seated than supine position. Fourteen healthy males were investigated during ambulatory and controlled laboratory conditions at the end of two consecutive 5-day periods with sodium intakes of 70 (low) and 250 (high) mmol/24 h or vice versa, respectively. Comparing high and low sodium intake, plasma volume and plasma protein concentrations were 9 and 8% higher in the seated and the supine position, respectively. When seated during laboratory conditions, CO was 5.3 +/- 0.2 l/min on the high sodium intake vs. 4.8 +/- 0.2 l/min on the low (P < 0.05), and SV was 81 +/- 3 vs. 68 +/- 3 ml (P < 0.05). In the supine position, SV was 107 +/- 3 ml on the high vs. 99 +/- 3 ml (P < 0.05) on the low sodium intake, while CO remained unchanged. The difference in CO and SV induced by the change in sodium intake was significantly higher in the seated than in the supine position (P < 0.05). During upright ambulatory conditions, CO was 5.9 +/- 0.2 l/min during the high and 5.2 +/- 0.2 l/min during the low sodium intake (P < 0.05), and SV was 84 +/- 3 and 69 +/- 3 ml (P < 0.05), respectively. Mean arterial pressure was unchanged by the variations in sodium intake. In conclusion, increments in sodium intake within the normal physiological range increase CO and SV and more so in the seated vs. the supine position. These changes are readily detectable during upright, ambulatory conditions. The results indicate that the higher SV and CO could constitute an arterial baroreflex stimulus for the augmented renal sodium excretion.

Adult↗

PubMed1983

Oesophageal transit of a radionuclide solid bolus in normals.

The purpose of this study was to evaluate the physiological transit pattern of a compact bolus through the oesophagus in normal subjects. A standard gelatine bolus labelled with 99mTechnetium pertechnetate was swallowed in the erect and the supine positions and traced by a gamma-camera in 20 subjects. In the erect position, the mean overall transit time was 5.5 +/- 1.1 s (SD) which differed significantly (P less than 0.001) from the longer mean overall transit time of 6.9 +/- 1.4 s (SD) in the supine position. The transit patterns differed between erect and supine positions. In the erect position, the bolus travelled at a constant velocity until the most distal part of the oesophagus where a slight retardation of the velocity occurred, whilst in the supine position, a uniform retardation of the velocity was seen which was slightly accentuated in the most distal part. The present data provide a basis for the evaluation of studies on the bolus transport in patients with suspected oesophageal dysfunction.

Adult↗

PubMed2002

The impact of patient positioning on the adequate coverage of the uterus in the primary irradiation of cervical carcinoma: a prospective analysis using magnetic resonance imaging.

BACKGROUND AND PURPOSE: The intention of this prospective study is to assess the influence of different patient positionings and the use of belly boards on the coverage of the uterus by standard radiation fields. MATERIAL AND METHODS: In 21 women with carcinoma of the uterine cervix magnetic resonance imaging (MRI) scans in prone patient position with and without belly board and computed tomography (CT) scans in supine position were analysed after superimposing standard pelvic box fields. Further, all patients underwent a second MRI field control in prone position with belly board to detect intraindividual variations in the uterus position during treatment. RESULTS: Standard portals did not completely cover the uterus in supine position in 7/21 (33%), in prone position with belly board in 7/21 (33%) and without belly board in 5/21 (24%). Insufficient uterine coverage was found only in the anteroposterior direction. The mean distance (+/- standard deviation) between the field borders of the lateral portals and the uterus was in supine position anteriorly 3.4 cm (+/-2.2 cm) and posteriorly 1.8 cm (+/-1.3 cm), in prone position with belly board anteriorly 2.2 cm (+/-2.7 cm) and posteriorly 2.6 cm (+/-1.6 cm), prone without belly board anteriorly 3.3 cm (+/-2.4 cm) and posteriorly 1.9 cm (+/-1.1 cm). The difference was statistically significant between supine and prone position with belly board and between prone position with and without belly board. Repeated MRI controls during therapy showed no significant changes compared to the MRIs at the beginning of therapy. CONCLUSIONS: The use of standard radiation fields results in a high percentage of geographical misfits. Three-dimensional treatment planning is a prerequisite for adequate uterus coverage.

Adult↗

PubMed1999

Effects of posture on left ventricular diastolic filling during exercise.

BACKGROUND: Measuring the transmitral flow velocity with Doppler echocardiography is a useful method for evaluating left ventricular diastolic function. However, there are few data regarding the effect of posture during exercise on transmitral flow velocity. METHODS: The transmitral flow velocity with pulsed-wave Doppler echocardiography was measured during supine and upright bicycle ergometer exercise in 10 normal young men without cardiac disease (26.7 +/- 5.5 yr). RESULTS: The ratio of the early rapid filling wave to the atrial filling wave (E/A) was gradually decreased with increasing exercise intensity. At rest and during recovery, the E/A ratio was significantly higher (P < 0.01) in the supine position than in the upright position. This difference was caused mainly by the higher E wave in the supine position. However, E wave and E/A ratio did not differ between the upright and supine position during exercise. CONCLUSION: Although measurement of left ventricular filling is completely noninvasive and clinically useful for evaluating diastolic function, it was found that the E/A ratio was profoundly influenced by posture and exercise intensity. These results suggest that the potential influences of posture and exercise intensity on the filling velocities should be taken into account when interpreting diastolic function by Doppler echocardiography.

Adolescent↗

PubMed1994

Prone position breast irradiation.

PURPOSE: An alternative technique for irradiating the breast following breast conserving surgery is described. METHODS AND MATERIALS: The technique utilizes the prone position and has been developed to improve the dose distribution within the breast and reduce the volume of normal tissues irradiated during whole breast treatment. Improvements in the dosimetry of breast irradiation are obtained through the optimization of the shape of the breast and result in a reduction in the magnitude of high-dose regions and isodose gradients at the base of the breast. RESULTS: The high dose region at the base of the breast, without lung correction, generally ranges from 116-118% for large breasted women treated in the supine position. These high dose regions are reduced to 102-103% for the same women treated in the prone position. Irradiation of the heart, lungs, chest wall and contralateral breast are minimized with this technique. The improvements appear to benefit women with large breasts, pendulous breasts, large separations and/or irregularly shaped chest contours. CONCLUSION: The prone position technique takes advantage of the reproducibility characteristics of the supine position technique and combines them with the homogeneity and normal tissue-sparing characteristics of the lateral decubitus position technique. Prone position breast irradiation appears to be a simple and effective alternative to irradiation of the breast in the conventional supine position when the supine position is likely to result in unacceptable dose inhomogeneity or significant doses to normal tissues.

Breast↗

PubMed1995

Maximal values of sniff nasal inspiratory pressure in healthy subjects.

BACKGROUND: Inspiratory muscle strength is often better reflected by oesophageal pressure during a maximal sniff (sniff POES) than by maximal inspiratory pressure (PImax). Sniff POES can be estimated non-invasively by measuring the sniff nasal inspiratory pressure (SNIP). The aim was to establish maximal normal values for the SNIP and to compare them with PImax. METHODS: One hundred and sixty healthy subjects (80 men) aged 20-80 years were recruited. All subjects had a forced vital capacity (FVC) of > 80%, a forced expiratory volume in one second (FEV1)/FVC of > 85% predicted value, and a body mass index of 18-31 kg/m2. Because PImax is known to be reduced in the supine posture, the SNIP was measured in both the sitting and the supine positions. PImax sustained over one second was measured from functional residual capacity (FRC) in the sitting position with a standard flanged mouthpiece during four manoeuvres. SNIP was measured from FRC in the sitting and supine positions using a catheter through a plug occluding one nostril during 10 maximal sniffs through the contralateral nostril. For each test the largest pressure measured in cm H2O was taken into account. RESULTS: For both men and women maximal SNIP was negatively correlated with age, and was similar in the sitting and the supine positions. In the sitting position maximal SNIP was greater or equal to PImax in 107 of 160 subjects. The mean (SD) ratio SNIP/PImax was 1.08 (0.22) in men and 1.17 (0.29) in women. CONCLUSIONS: Normal values of maximal SNIP can be predicted from age and sex. Maximal SNIP is similar in the sitting and the supine position and is significantly higher than PImax in healthy subjects. The low level of agreement between maximal SNIP and PImax indicates that the two manoeuvres are not interchangeable but complementary.

Adult↗

PubMed1999

The effect of posture and exercise on elastic stocking compression at different sites of the leg.

BACKGROUND: In compression therapy, the importance of the degree of pressure has been emphasized. The aim of this study was to examine the influence of posture and exercise on the compression at different sites of the leg. PATIENTS AND METHODS: In 16 normal volunteers, the pressure was determined simultaneously at 5 sites on the leg during lying, sitting, standing, walking, running, knee-bending exercise and squatting using an air pack type analyzer. Pressure was measured under 3 experimental conditions: with a thigh-length gradient stocking, with foam rubber pads included under the elastic stocking, and after removal of both elastic stocking and compression pads. RESULTS: When the stocking was worn, a pressure gradient was observed in the proximal direction during the sequence from the supine position to running. When the pads were included, the pressure in the supine position was significantly elevated at all sites examined, and the graduated pressure drop was also maintained from supine position to running. However, the pressure at the tibia was significantly higher than that at the gastrocnemius in both supine and sitting positions when the pads were used, while no significant difference was observed between both sites in the standing position. A marked increase in pressure at the ankle, gastrocnemius, and hollow of the knee was observed during squatting when the stocking was worn either with or without pads, while a significant decrease in pressure was observed at the tibia. CONCLUSION: The pressure exerted by elastic stockings varies with the posture and exercise. Furthermore, the changes in pressure vary from site to site.

Adolescent↗

PubMed1989

Effect of the knee-chest position on cerebral blood flow in patients undergoing lumbar spinal surgery.

The cerebral haemodynamic effect of the knee-chest position was evaluated in 15 anaesthetised patients undergoing elective lumbar disc surgery and divided into a control group (n = 8) where cerebral blood flow (CBF) was measured twice in the supine position and an experimental group (n = 7) where the first CBF was measured in the supine position and the second in the knee-chest position. CBF was measured by a modified intravenous 133xenon washout technique. Mean global CBF did not change in control group (56.1, SD 9.2 versus 52.8, SD 10.8 units) and was not significantly modified by the knee-chest posture, 51.8, SD 8.8 units versus 53.9, SD 7.4 units in the supine position. The results indicate that mean global CBF in the knee-chest position is not different from CBF in the supine position in healthy patients.

Adult↗

PubMed2003

The effect of mosapride on oesophageal motor function and acid reflux in patients with gastro-oesophageal reflux disease.

OBJECTIVE: To evaluate the efficiency of the 5-HT4 agonist and 5-HT3 antagonist mosapride, as compared with cisapride, on oesophageal acid reflux variables and oesophageal motor function in patients with chronic gastro-oesophageal reflux disease (GORD). METHOD: Forty-one patients with proven GORD were included in a double-blind, randomised, double-dummy, three-way crossover study. All patients received mosapride 60 mg twice daily, mosapride 30 mg three times daily, and cisapride 20 mg twice daily for seven days in a randomised order, separated by a washout period of at least five days. Twenty-three patients underwent four combined ambulatory 24-h motility and pH recordings within two weeks before the start of treatment and on day seven of each treatment period. The remaining 18 patients underwent three ambulatory 24-h pH recordings only, i.e. on treatment day seven of each treatment period. RESULTS: Mosapride had no significant effect on the total number of contractions in the oesophagus, or on the effectiveness, or possible effectiveness, of the propagations. Significant but numerically small effects on peristaltic durations and amplitudes were noted during both mosapride and cisapride treatment as compared with baseline values. The effect on acid reflux for both mosapride and cisapride was most pronounced for the duration of the longest reflux episode. The fraction of time with pH less than 4 was reduced by mosapride 30 mg three times daily in the supine position and by cisapride both totally and in the supine position. The number of reflux episodes was reduced significantly only by cisapride. Oesophageal clearance was reduced significantly by cisapride only in the supine position. CONCLUSION: Mosapride had small but statistically significant effects, comparable to those of cisapride, on acid reflux variables and oesophageal motor function in patients with GORD.

Adult↗

PubMed1999

Influences of bilateral endoscopic transthoracic sympathicotomy on cardiac autonomic nervous activity.

OBJECTIVES: Endoscopic transthoracic sympathicotomy (ETS) is a minimal invasive procedure of thoracic sympathetic blockage. The purpose of this study was to evaluate cardiac autonomic nervous activity after ETS in order to confirm the reliability and safety of ETS. METHODS: A series of electrophysiological studies were performed before and 1 week after bilateral 2nd and 3rd thoracic sympathicotomy in 13 patients with primary palmar hyperhydrosis. Palmar perspiration was measured under sympathetic stress, and body surface mapping was recorded in a supine position. In the head-up tilt test of 0, 30, 60 and 90 degrees, corrected QT interval (QTc) and T wave amplitude (Twa) were assessed. The power spectral analysis of heart rate variability was processed to attain power values of the low-frequency (0.04-0.15 Hz), the high-frequency (0.15-0.40 Hz) and the low/high frequency ratio. RESULTS: In all patients, the perspiration response on the palm to sympathetic stimulation was completely inhibited after ETS. Isointegral mapping revealed that ETS altered electroactivity on the heart. In the head-up tilt study, R-R intervals significantly increased after the surgery in the head-up tilt positions (P < 0.05), although there was no significant difference in the supine position. There is no significant difference in QTc and Twa before and after the surgery, both in the supine and the head-up tilt positions. There was no significant difference in the LF or HF before and after surgery, either in the supine position or the head-up tilt positions. In the LF/HF, there was no significant difference before and after surgery in the supine position. However, the LF/HF in the head-up tilt positions was significantly decreased after surgery (P < 0.05). Sympathetic suppression of ETS was recognized more obviously under the steeper head-up tilt positions. CONCLUSIONS: The influences on the cardiac autonomic nerve system of the ETS of upper thoracic sympathetic nerve were seen to be of a lesser degree at rest. However, the response to sympathetic stimulation was suppressed after the surgery.

Adolescent↗

PubMed1999

Age-related differences in blood pressure and heart rate responses to changes in body position: results from a study with serial measurements in the supine and standing positions in 30-, 50- and 60-year-old men.

This population-based study presents the blood pressure and heart rate responses to sudden changes in body position in representative groups of men aged 30 (n = 50), 50 (n = 44) and 60 (n = 69) years, using an unbiased method for non-invasive blood pressure measurements. Blood pressure and heart rate were measured every minute during three 7-min periods in the supine, standing and again supine positions. Whereas there was an initial decrease in systolic blood pressure upon standing in men aged 50 and 60 years, an increase was seen in the 30-year-olds. The diastolic blood pressure increased in all age groups, but less in the older compared to the younger men. In all age groups, the changes in systolic blood pressure upon standing were transient, while the changes in the diastolic blood pressure lasted during the entire observation period. The heart rate increased to a similar extent upon standing in all age groups. No symptomatic hypotension was observed. After resuming the supine position, both blood pressure and heart rate returned towards the levels initially recorded. This population-based study confirms previous observations in selected subjects of age-related attenuation in blood pressure response to change in body position. The study also shows that blood pressure and heart rate are rapidly stabilized upon standing up.

Adult↗

PubMed1994

The effect of posture change on blood volume, serum potassium and whole body electrical impedance.

After standing for 1 h, ten subjects (7 male, 3 female) assumed a supine position for a further hour. Whole body bioelectrical impedance increased progressively during the hour spent in the supine position: after 60 min supine the increase was 13(6 to 32) omega. Blood and plasma volumes, estimated from haematocrit and haemoglobin concentration, increased by 8.0(6.7 to 12.4)% and 16.7(12.3 to 20.8)% (median(range)) respectively after 60 min supine. Serum potassium concentration had fallen after 10 min supine (4.1(0.1)mmol l-1; mean (SEM)) relative to the standing value (4.6(0.1)mmol l-1) and was unchanged thereafter. Serum osmolality (P = 0.991) and sodium (P = 1.000) and chloride (P = 0.998) concentrations remained unchanged throughout the study. The fall in serum potassium concentration in the supine position does not appear to be a simple dilutional effect consequent upon increases in blood and plasma volume as there was no effect of postural change on serum sodium or chloride concentrations.

Adult↗

PubMed1992

Effect of prone versus supine patient positioning on pelvic magnetic resonance image quality.

RATIONALE AND OBJECTIVES: Magnetic resonance imaging (MRI) of the pelvis in the prone position has been proposed as a means of reducing motion-related image blurring. The authors performed a randomized controlled trial to determine if patient positioning affects image quality. METHODS: All women undergoing pelvic MRI during a 7-month period, who could lie both prone and supine, were randomized to the supine or prone position. The quality of axial T2-weighted spin-echo images was rated by two radiologists using a 1-to-4 scale (1 = marked blurring to 4 = sharp definition of pelvic structures). RESULTS: Of 78 eligible women, 61 were randomized. Two patients could not complete the examination. The mean image quality rating of 2.8 for the 32 patients imaged prone was not significantly different from the mean rating of 2.9 for the 27 patients imaged supine (P = .5, Mann-Whitney U test). CONCLUSION: Patient positioning did not significantly affect pelvic MRI quality. The choice of patient position should be based on other considerations, such as patient comfort or ease of patient positioning.

Adult↗