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PubMed2000

Postural-induced changes in intracranial pressure evaluated non-invasively using the MMS-10 tympanic displacement analyser in healthy volunteers.

Inner ear pressure reflects intracranial pressure (ICP) primarily because of the direct communication of perilymph and cerebrospinal fluid (CSF) through the cochlear aqueduct (CA). The MMS-10 tympanic displacement analyser (TDA) is a relatively new device for measuring perilymphatic pressure non-invasively, and thereby also indirectly measuring intracranial pressure. The aim of the present study was to evaluate the use of the TDA in a daily clinical setting. Other aims were to investigate changes in perilymphatic pressure from sitting to lying position in healthy volunteers in two age groups (mean age: 33 years and 50 years) and to compare the patency of the CA in these groups using the MMS-10 TDA. Tympanic membrane displacement (TMD) analyses were performed in the test subjects initially twice in sitting position (test-retest) and then in sitting and supine positions. We found that the MMS-10 TDA is easy to use, and that it gives reproducible values in repeated tests, but with large inter-subject differences. The TMD test showed curves, which, in the whole test group, were more negative in supine position, in accordance with an increasing intracranial and inner ear pressure when lying down. The change from sitting to lying position was larger in the younger group than in the older group. In 11% of the younger group (males) and in 30% of the older group (females), the CA was considered to be non-patent, although the difference was not statistically significant. However, the finding is in keeping with the hypothesis of a greater proportion of patent CA in younger than in older individuals.

Adult↗

PubMed1991

A comparative study between a new, 50-degree right-semidecubital scanning and usual supine scanning of thallium-201 myocardial tomography for evaluation of coronary artery disease.

Images of thallium-201 cardiac tomography in the 50-degree right-lateral-semidecubital vs. usual supine positions were compared after a single dose of the isotope in 225 patients with or suspected of coronary artery diseases. Compared with the supine position method, the semidecubital position method enabled 25% shortening of the orbital radius (20.0 +/- 0.9 cm to 15.3 +/- 0.6 cm, n = 174, p less than 0.05), higher posteroinferior wall counts in both exercise and 3-hour-delayed images by up to 18%, better image sharpness and contrast, less motion artifact, more marked redistribution in the ischemic walls, and significantly higher specificity (57% vs. 78%, p less than 0.05) and accuracy (63% vs. 79%, p less than 0.05) for inferior wall lesions. The results indicate that the thallium cardiac scan is significantly affected by patient position during scanning, i.e., artifactual inferior wall defects due to photon attenuation in the supine position method. The semidecubital position method is recommended to minimize this artifact. The method is simple, easy to perform, well tolerated, feasible in any 1-headed tomography system, inexpensive, and free of running costs.

Angina Pectoris↗

PubMed1998

Effect of body position on tidal volume and minute ventilation in very low birthweight infants.

BACKGROUND: To progress the clinical treatment of neonates, especially in the management of respiration, we have to be able to measure their pulmonary function appropriately. Various methods have been developed, but little is known about the pulmonary function of very low birthweight infants (VLBWI) because of the difficulty in taking their measurements with existing equipment. We have developed a very low dead space pneumotachograph to measure lung function in VLBWI. METHODS AND RESULTS: We used our pneumotachograph on 30 infants each weighing less than 1500 g at birth. The infants were intubated with endotracheal tubes of 2.5 or 2.0 mm diameter to measure tidal volume and minute ventilation in the prone and supine position. The tidal volume in the supine position was 6.99 +/- 0.42 mL/kg and 7.58 +/- 0.38 mL/kg in the prone position (mean +/- SE). The tidal volume was significantly larger in the prone than the supine position (P < 0.05). However, no significant difference was observed in minute ventilation and respiratory rates. CONCLUSION: The tidal volume significantly increased in the prone position in VBLWI, confirming the previous observation of larger healthy infants is also applicable to the very low birthweight infants.

Equipment Design↗

PubMed1999

Effect of body position changes on pulmonary gas exchange in Eisenmenger's syndrome.

Preliminary studies on sleep of patients with congenital heart disease and Eisenmenger's syndrome (ES) at our institution demonstrated nocturnal worsening arterial unsaturation, which appeared to be a body position-related phenomenon. To investigate the potential effect of body position on gas exchange in ES, we carried out a prospective study of 28 patients (mean age, 34.8 +/- 11.7 yr) with established ES due to congenital heart disease. In every patient, arterial blood gases were performed during both sitting and supine positions under three different conditions: room air, while breathing 100% oxygen, and after breathing oxygen at a flow rate of 3 L/min through nasal prongs. Alveolar oxygen pressure (PaO2) for the calculation of alveolar-arterial oxygen tension differences (AaPO2) was derived from the alveolar gas equation using PaCO2 and assuming R = 1. We used paired t test, repeated-measures two-way ANOVA with Bonferroni's test, and regression analysis. From sitting to supine position on room air, there was a significant decrease in PaO2 (from 52.5 +/- 7.5 to 47.5 +/- 5.5 mm Hg; p < 0. 001) and SaO2 (from 86.7 +/- 4.6 to 83.3 +/- 4.9%; p < 0.001), both of which were corrected by nasal O2 (to 68.2 +/- 21 mm Hg and to 92 +/- 4%, respectively, p < 0.005). PaCO2 and pH remained unchanged. The magnitude of the change in PaO2 correlated with the change in AaPO2 on room air (r = 0.77; p < 0.01) but not with the change in AaPO2 on 100% oxygen. It is concluded that in adult patients with ES there is a significant decrease in PaO2 and SaO2 when they change from the sitting to the supine position. A ventilation-perfusion (V/Q) distribution abnormality and/or a diffusion limitation phenomenon rather than an increase in true shunt may be the mechanisms responsible for this finding. The response to nasal O 2 we observed warrants a trial with long-term nocturnal oxygen therapy in these patients.

Adult↗

PubMed1976

The effect of standing and exercise on plasma catecholamines, serum insulin, and serum gastrin.

Glucose-stimulated insulin secretion was measured in six normal subjects in the resting supine position, during standing, and during a period of moderate exercise in the supine position. Plasma noradrenaline averaged 0.26 ng/ml in the supine, resting position and rose to 0.57 and 0.61 ng/ml at the end of the standing experiment and the exercise period, respectively. Plasma adrenaline was unchanged in the standing position but rose threefold during exercise (to 0.09 ng/ml). Serum gastrin tended to decrease in all three experiments after the injection of glucose. Glucose-stimulated insulin secretion was the same during the first 10 min after the injection of glucose in the three experiments. It is concluded that a moderate increase in adrenergic activity has no influence on glucose-stimulated insulin secretion.

Adult↗

PubMed1993

Prone or supine body position and sleep characteristics in infants.

OBJECTIVE: To evaluate the potential relation between body position and sleep characteristics in normal infants. PATIENTS: Two groups of 3-month-old healthy infants were evaluated: 40 infants who usually slept supine, and 40 who usually slept prone. The two groups were matched for gender, gestational age, postnatal age, birth weight, and total recording time. RECORDING TECHNIQUES: The 80 infants were studied polygraphically during one night in the pediatric sleep laboratory. They were allowed to fall asleep in their usual sleep position, and every 3 hours were gently turned from prone to supine, or from supine to prone. RESULTS: In each group, 6 infants were excluded from the analysis, because they woke up after having been turned over. In both groups, no significant difference was seen between the prone and the supine body positions for the following variables: number of sleep state changes; number of gross body movements; percent of rapid eye movement sleep; saturation with oxygen, arterial blood levels; number and duration of acid esophageal reflux; rectal temperature; mean respiratory rates; water evaporation rates from the forehead skin; and number or duration of central or of obstructive apneas. In both groups of infants, prone body position was associated with a significant increase in sleep duration (+16%) and in non-rapid eye movement sleep (+25%) and a significant decrease in number of arousals (-40%) and in their duration (-43%). CONCLUSIONS: No explanation has been found for the sleep-promoting effect of prone body positioning. The finding could be of interest to the study of infants' sleep quality, as well as to the potential relation between body positions and sudden death during sleep.

Female↗

PubMed1997

Predictive value of several signs of infection as surrogate markers for mortality in a neutropenic guinea pig model of Pseudomonas aeruginosa sepsis.

Infected, neutropenic animals are used as experimental models to evaluate the relative efficacies of antimicrobial agents and host-pathogen-antibiotic interactions. In the past, these models used death as the study end point. Because of the concern about use of death as an end point, we evaluated the accuracy with which various signs of infection predicted mortality in a neutropenic guinea pig model of treated and untreated Pseudomonas aeruginosa sepsis. The potential surrogate markers studied included ruffled fur, respiratory distress, diarrhea, hunched posture, lethargy, abnormal neurologic movements (twitching, paralysis of a limb), inappetence for > 48 h, the inability to ambulate, and the inability of a supine animal to stand. In addition, we evaluated whether percentage of weight loss or change in daily food and water consumption were predictive of mortality. Animals were inspected for these signs at least every 4 h during the day and every 8 h in the evening. In treated and untreated animals, 100% of subjects that were unable to ambulate or to rise from the supine position died (positive predictive value for death was 100% for either sign). Guinea pigs that could not rise from a supine position expired between 1 and 8 h after this sign was observed. Those that could not ambulate died between 4 and 40 h after that sign was observed. In treated and untreated animals, none of the survivors manifested either sign of disease (100% specificity for each sign). However, 59% of untreated and 69% of treated animals that were ambulatory were found dead at the next observation period, underscoring the rapidity with which this infection progresses to death when it enters its final stage. No other signs of infection distinguished animals that survived or died. Thus, the inability of neutropenic, infected guinea pigs to rise from a supine position and the inability to ambulate were the only signs that accurately predicted death and, therefore, are the only signs that can be used as surrogates for death in this experimental model of P. aeruginosa sepsis.

Animals↗

PubMed2006

Common peroneal nerve palsy: an unexpected complication of liver surgery.

BACKGROUND: Common peroneal nerve palsy is a well-recognized complication following surgery in lithotomy position, particularly colorectal and gynecologic surgery. But it is quite rare after liver surgery because patients are usually placed in supine position. CASE REPORT: There were three cases of common peroneal nerve palsy after liver surgery in the past 2 years, including two cases of liver transplantation and one case of extended right hepatectomy. Two cases were bilateral and one case was unilateral. They were placed in supine position and the mean operative time was 8 hours. Patients complained symptom of foot drop within 1 week after operation. Electromyographic examinations showed evidence compatible with common peroneal nerve palsy. All of them improved with conservative treatment within 6 months. CONCLUSION: Common peroneal nerve palsy may develop after liver surgery even in supine position. Injury to common peroneal nerve should be a concern before and during the operation. This complication could be managed conservatively with an uneventful result.

Adult↗

PubMed1996

Central venous pressure in humans during microgravity.

Based on the results of head-down simulation studies and the results of parabolic flights, the hypothesis was tested that central venous pressure (CVP) in humans increases during microgravity (weightlessness) compared with during the ground-based supine position. CVP was recorded with an intravascular pressure transducer in seven healthy humans during short (20-s) periods of microgravity created by parabolic-flight maneuvers and in one astronaut before, during, and up to 3 h after launch of the Spacelab D-2 mission (Space Transport System-55). When the subjects were supine during the parabolic maneuver, CVP decreased during microgravity from 6.5 +/- 1.3 to 5.0 +/- 1.4 mmHg (P < 0.05). during the Spacelab D-2 mission, CVP was 6.2 mmHg during the initial minutes of microgravity, which was very similar to the value of 6.5 mmHg in the supine position 3.5 h before launch of the space shuttle. During the subsequent 3 h of weightlessness, CVP during rest varied between 2.0 and 6.2 mmHg. We conclude that CVP during short (20-s) and longer (3-h) periods of microgravity is close to or below that of the supine position on the ground.

Adult↗

PubMed2002

Prone versus supine sleep position: a review of the physiological studies in SIDS research.

A number of physiological studies, published over the last 10 years, have investigated the links between prone sleeping and sudden infant death syndrome (SIDS). This review evaluates those studies and derives an overview of the different affects of sleeping prone or supine in infancy. Generally, compared with the supine, the prone position raises arousal and wakening thresholds, promotes sleep and reduces autonomic activity through decreased parasympathetic activity, decreased sympathetic activity or an imbalance between the two systems. In addition, resting ventilation and ventilatory drive is improved in preterm infants, but in older infants (>1 month), there is no improvement in ventilation, and in 3-month-old infants, the position is adverse in terms of poorer ventilatory drive (in active sleep only). The majority of findings suggest a reduction in physiological control related to respiratory, cardiovascular and autonomic control mechanisms, including arousal during sleep in the prone position. Since the majority of these findings are from studies of healthy infants, continued reinforcement of the supine sleep recommendations for all infants is emphasized.

Arousal↗

PubMed1997

Improved dialysis dose by optimizing intraperitoneal volume prescription thanks to intraperitoneal pressure measurements in children.

An optimal intraperitoneal volume (Vip) may be the most critical and least-used option to enhance higher clearances of small solutes. A higher Vip is more effective in increasing small solute clearances when compated to a lower Vip and more frequent exchanges. Additionally, a higher Vip generates minimal intraperitoneal pressure (Pip) in the supine position. Therefore, the highest tolerated Vip should be used at night while the child is sleeping in the supine position. Therefore, in 5 children, mean age 7 years, 4 months, on continuous cyclic peritoneal dialysis (CCPD) (Baxter HomeChoice), we tested the impact of Vip on tolerance (measured by Pip) measurements, and efficiency [assessed by daily Kt/Vurea and weekly creatinine clearance (Kcreatinine]. Basal Pip was determined for the usually prescribed Vip. Then Vip was increased during a morning outpatient study day, in 30-minute stages, stepping up to an increase of 25% of the basal Pip (upper limit 18 cm of water) level reached at the so-called optimized Vip used for the prescription of an optimal total dialysate volume for a 4-week period. The latest study week was compared to the prestudy week. The optimized Vip of 1230 +/- 70 mL/m2 was significantly higher than the basal Vip, 940 +/- 90 mL/m2. The dialysis dose improved both in terms of Kt/V urea from 0.23 +/- 0.02 to 0.29 +/- 0.03 and Kcreatinine from 60 +/- 5 to 76 +/- 9 L/1.73 m2/week. The supine position allowed the 25% Pip increment from 10.2 +/- 2.5 to 12.5 +/- 3.1 cm water, without any obvious clinical side effects.

Child↗

PubMed1986

Plasma renin and aldosterone changes during twenty minutes' moderate exercise. Influence of posture.

The influence of posture on plasma renin and aldosterone changes during exercise performed at a constant relative work load (40%-50% maximal oxygen uptake) was studied in eight healthy men. Each subject carried out two 20-min exercises on an ergocycle at an interval of 8 days; the first exercise was performed in the normal sitting position (upright exercise), the second in a comfortable supine position (supine exercise). In both cases, heart rate and blood pressure were measured as well as plasma renin activity (PRA), aldosterone (ALDO) and osmolality, before and immediately after exercise, and 15 min following the end of exercise. An increase in heart rate, blood pressure, PRA, ALDO and osmolality was noted at the end of each exercise. This increase was greater in the supine exercise than when upright for PRA and ALDO; plasma osmolality and blood pressure showed identical increases for both types of exercise; increase in heart rate was greater when supine than when upright. PRA and ALDO were still elevated 15 min after the upright activity, but had regained their base values in that time after the supine exercise. Our results show that moderate, relatively brief periods of exercise stimulate the production of renin and aldosterone, but the response is less when supine than in the normal upright position.

Adult↗

PubMed1991

Orthostatic function during a stand test before and after head-up or head-down bedrest.

Astronauts may exhibit orthostatic dysfunction upon returning to 1 g after space flight. Understanding cardiovascular changes at 0 G will provide insights into the mechanisms of the loss of orthostatic tolerance, whether due to space flight or bedrest. Bedrest is one model used to produce cardiovascular changes that are associated with space flight. In the current study, young male adults were placed at -5 degrees, +10, +20, or +42 degrees bedrest (0, 1/6, 1/3, and 2/3g, respectively) for 6 hours on 4 different days. This was preceded and followed by a stand test: 5 minutes in the supine position, and then 5 minutes in the standing position, with the feet 9 inches apart and 6 inches from the wall. Cardiovascular values were measured at 1-minute intervals. Systolic and diastolic pressures were measured using an automated blood pressure device; mean arterial pressure (MAP; mm Hg) was calculated. Heart rate (bpm) and cardiac parameters were measured with a thoracic impedance device. Minute 3, 4, and 5 values were used to determine whether there were time or angle effects. Of six subjects, one reported nausea upon 3 minutes of standing after 6 hours of bedrest at -5 degrees. The same subject was lightheaded in the first minute of standing after 6 hours of bedrest at +10 degrees. Mean heart rate pre-bedrest in the supine position was 63 and increased by 24 bpm on standing. Heart rate post-bedrest in the supine position was 65 and increased by 35 bpm on standing; standing heart rate increased 11 bpm after -5 degrees bedrest. The increases after +10 degrees, +20 degrees, and +42 degrees tilts were 4, 3, and 4 bpm, respectively. Changes in the mean arterial blood pressure were minimal. Results from the stand test pre- and post- 6 hours of bedrest at -5 degrees but not at +10 degrees, +20 degrees, or +42 degrees are similar to those after space flight.

Adult↗

PubMed1993

Alcohol consumption and hypertension.

The effect of acute alcohol consumption was studied in healthy subjects (Group-I) and in nondrinking hypertensive (Group-II) and in regularly drinking hypertensive patients (Group-III). All subjects consumed alcohol (1gm/kg body weight daily) for 5 days, then abstained for 5 days. Blood pressure was recorded in standing and supine position every morning. Group-I showed no significant difference in blood pressures during and after alcohol consumption. Group-II showed a statistically significant increase in the supine and standing systolic/diastolic and mean blood pressure when consuming alcohol (P < 0.01) as compared to the period of abstinence. In Group-III, hypertensive patients who drank regularly showed significant decrease in systolic blood pressure in the period of abstinence during standing (p < 0.02) as well as in supine position (p < 0.001) and diastolic and mean blood pressure reduction in standing and supine position (p < 0.01) as compared to the period of drinking.

Adult↗

PubMed1999

[Variability of heart auscultation in patients with mitral valve prolapse].

The aim of the study was to analyze the auscultatory findings and its variability in 84 patients (pts) with mitral valve prolapse syndrome (MVPS) who were examined in the different body positions. All the pts underwent the echocardiographical examination and in 32 subjects (38%) prolapse of the anterior mitral leaflet was found, in 40 pts (48%) prolapse of the posterior mitral leaflet and in 12 (14%) pts prolapse of the both mitral leaflets. The auscultation of the heart was done in the supine position, in the lying position on the left side and in the upright position of the patient's body. Characteristic for the mitral valve prolapse (MVP) auscultatory findings (midsystolic murmur, late-systolic murmur and/or mid-systolic "non ejection" click) were demonstrated by 43 pts (51%) in the supine position. During the auscultation in the lying position of the pts on the left side, the auscultatory findings were found in 57 pts (68%) while in the upright position in 64 pts with MVPS (76%). The study showed that the auscultatory findings in pts with MVPS were demonstrated more frequently in the lying position of the body on the left side or in the upright position compared with the supine position. Moreover we found that 20 pts with MVPS (24%) did not demonstrate the characteristic auscultatory findings of MVP.

Adolescent↗

PubMed1988

Posture-induced airflow limitation in asthma: relationship to plasma catecholamines and an inhaled anticholinergic agent.

Postural influence on ventilatory function was investigated in thirteen asthmatic subjects on three consecutive days starting at 10.00 am. Lung function was measured in the seated position before and after four hours lying supine. Peak expiratory flow (PEF) was measured every 0.5 h in the supine position. Blood samples for determination of plasma catecholamines were collected before, during and after lying supine. After the initial lung function testing, placebo or ipratropium bromide (0.125 mg) was inhaled. On the third day the whole trial was performed seated, without any drug, as a control experiment. On the placebo day lying supine induced an initial, rapid fall of PEF followed by a progressive decrease during the four hours. The progressive decrease in PEF was apparently caused by bronchoconstriction. Ipratropium bromide prevented this posture-induced bronchoconstriction. On the day seated there was also a tendency towards a decline of PEF though less pronounced than in the supine position on the placebo day. No significant alterations in plasma levels of catecholamines were observed. We conclude that the supine posture is a stimulus to bronchoconstriction in asthma, likely to be involved in nocturnal wheezing. Postural bronchoconstriction is not explained by lowered plasma levels of adrenaline, as has been suggested for nocturnal asthma. The results raise the question of whether cholinergic mechanisms are involved.

Acute Disease↗

PubMed2004

Development of respiratory motion reduction device system (RMRDs) for radiotherapy in moving tumors.

BACKGROUND: The internal target volume (ITV) for tumors in the abdomen or thorax includes sufficient margin for breathing-related movement of tumor volumes during treatment. Depending on the location of the tumor, the magnitude of the ITV margin extends from 1 to 3 cm, which increases substantially the volume of the irradiated normal tissue, hence resulting in an increase in normal tissue complication probability (NTCP). We developed a simple and handy method which can reduce ITV margins in patients with moving tumors: the respiratory motion reduction device system (RMRDs). METHODS: The patient's clinical database was structured for moving tumor patients and patient set-up error measurement and immobilization device effects were investigated. The system is composed of the respiration presser device (RPD) utilized in the prone position and the abdominal strip device (ASD) utilized in the supine position, and the analysis program, which enables analysis of patient set-up reproducibility. It was tested for analyzing the diaphragm movement from patients with RMRDs, the magnitude of the ITV margin was determined and the dose-volume histogram (DVH) was computed using treatment planning software. The dose to normal tissue in patients with and without RMRDs was analyzed by comparing the fraction of the normal liver receiving 50% of the isocenter dose. RESULTS: Average diaphragm movement due to respiration was 16 +/- 1.9 mm in the case of the supine position, and 12 +/- 1.9 mm in the case of the prone position. When utilizing the RMRDs, which was personally developed in our hospital, the value was reduced to 5 +/- 1.4 mm, and in the case in which the belt immobilization device was utilized, the value was reduced to 3 +/- 0.9 mm. In the case where the strip device was utilized, the value was proven to reduce to 4 +/- 0.3 mm. As a result of analyzing the volume of normal liver where 50% of the prescription dose is irradiated in DVH according to the radiation treatment planning, the use of the RMRD can create a reduction of 30% to the maximum. Also by obtaining the digital image, the function of comparison between the standard image, automated external contour subtraction, etc. was utilized to develop a patient set-up reproducibility analysis program that can evaluate the change in patient set-up. CONCLUSION: Internal organ motion due to breathing can be reduced using RMRDs, which is simple and easy to use in the clinical setting. It can reduce the organ motion-related planning target volume margin, thereby decreasing the volume of irradiated normal tissue.

Humans↗

PubMed2000

Effects of the supine and prone position on diaphragm thickness in healthy term infants.

BACKGROUND: The physiological basis underlying the decline in the incidence of sudden infant death syndrome (SIDS) associated with changing the sleep position from prone to supine remains unknown. AIMS: To evaluate diaphragm thickness (t(di)) and shortening in healthy term infants in the prone and supine positions in order to determine whether changes in body position would affect diaphragm resting length and the degree of diaphragm shortening during inspiration. METHODS: In 16 healthy term infants, diaphragm thickness at the level of the zone of apposition on the right side was measured using ultrasonography. Heart rate (HR), breathing frequency (f), and transcutaneous oxyhaemoglobin saturation (SaO(2)) were recorded simultaneously during diaphragm imaging with the infants in the supine and prone positions during quiet sleep. RESULTS: At end expiratory (EEV) and at end inspiratory lung volumes (EIV), t(di) increased significantly in the prone position. The change in t(di) during tidal breathing was also greater when the infant was prone. SaO(2), HR, and f were not significantly different at EEV and at EIV in both positions. CONCLUSION: In healthy term infants, placed in the prone position, the diaphragm is significantly thicker and, therefore, shorter, both at EEV and EIV. Diaphragm shortening during tidal breathing is greater when the infant is prone. In the prone position, the decreased diaphragm resting length would impair diaphragm strength, and the additional diaphragm shortening during tidal breathing represents added work performed by the diaphragm. This may compromise an infant's capacity to respond to stressful situations when placed in the prone position and may contribute to the association of SIDS with prone position.

Algorithms↗