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PubMed2004

Power spectral analysis of heart rate in relation to sleep position.

We used spectral analysis of heart rate variability, as a measure of autonomic tone, to determine spectral power differences in infants sleeping supine and prone. We studied 29 infants with a birth weight of 1,915 +/- 939 g, at the postconceptional age of 36 +/- 2 weeks. We then calculated total power (TP), low-frequency power (LF, 0.03-0.15 Hz), and high-frequency power (HF, 0.5-1.0 Hz). TP corresponds to overall heart rate variability, LF to both sympathetic and parasympathetic activity, and HF to parasympathetic activity only. Median (25th, 75th percentile) TP (beats/min2) in the supine position was 32.60 (23.12, 59.90), which was significantly higher than the prone position of 25.87 (14.94, 35.57). Similarly, LF (beats/min2) in the supine position of 13.82 (8.63, 23.31) was significantly higher than the prone position of 9.79 (5.46, 14.33). No significant difference was seen in the HF. We conclude that the prone position is associated with decreased heart rate variability and probably decreased sympathetic tone, which imply decreased autonomic stability in this position.

Birth Weight↗

PubMed1980

Saralasin infusion in renovascular hypertension: increased response rate in seated patients.

Most series report a significant percentage of nondepressor (negative) responses to saralasin infusions in patients with surgically curable renovascular hypertension. Usually the infusions have been performed with the supine position. In the present study saralasin infusions were done in 33 acutely sodium-depleted hypertensive patients--17 with renovascular and 16 with the essential variety. Most patients were infused in the seated and supine positions to test the hypothesis that there might be a higher incidence of positive (vasodepressor) responses to the saralasin infusion when patients are in a sitting position. The results did, in fact, show a larger number of positive responses to saralasin in the seated patients with renovascular hypertension than in those in the supine position (88% versus 71%). There was a modest increase in the rate of false-positive responses in the patients with essential hypertension who were infused in the seated position (31% versus 23%). However, inasmuch as the saralasin infusion test is proposed as a screening procedure for renovascular hypertension, some false-positive responses are acceptable.

Angiotensin II↗

PubMed2003

Intra-esophageal pH probe movement during eating and talking. A videoradiographic study.

PURPOSE: To registrate the oscillations of the pH probe in the esophagus during phonation and swallowing in the erect and supine positions. MATERIAL AND METHOD: Sixty-seven patients with suspicion of gastroesophageal reflux disease underwent manometry, 24-h pH monitoring, and videoradiography. In 43 patients the effect of dry, wet, and solid swallows in the erect and supine positions was determined, making a total of 258 swallows. In another 24 patients the effect of pH probe movement during phonation was studied. RESULTS: During every swallow the probe moved in the proximal direction from 0.5 to 2.0 cm, returned to baseline, and in 48 swallows an additional descendent movement of up to 2.0 cm was seen, the last mentioned more pronounced during solid swallows. In the erect position, no significant difference was observed for the different swallowing types, whereas in the supine position, movements were significantly more pronounced during solid food swallows. During phonation the pH probe only ascended and returned to the baseline, with no descending part. CONCLUSION: The pH probe movements are dependent on body position, bolus size, bolus composition, and talking. The ascending movements can only partially compensate for the esophageal shortening during swallow because of the time difference, and could perhaps explain the variation in results and reproducibility of 24-h pH monitoring.

Adolescent↗

PubMed2002

Can the tomographic aspect characteristics of patients presenting with acute respiratory distress syndrome predict improvement in oxygenation-related response to the prone position?

BACKGROUND: In some patients with acute respiratory distress syndrome, the prone position is able to improve oxygenation, whereas in others it is not. It could be hypothesized that the more opacities that are present in dependent regions of the lung when the patient is in the supine position, the better the improvement in oxygenation is observed when the patients are turned prone. Therefore, we conducted a prospective study to identify computed tomographic scan aspects that could accurately predict who will respond to the prone position. METHODS: We included 46 patients with acute respiratory distress syndrome (31 responders and 15 nonresponders). Computed tomographic scan was performed in the 6-h period preceding prone position. Blood gas analyses were performed before and at the end of the first 6-h period of prone position. RESULTS: Arterial oxygen partial pressure/fraction of inspired oxygen increased from 117 +/- 42 (mean +/- SD) in the supine position to 200 +/- 76 mmHg in the prone position (P < 0.001). There were 31 responders and 15 nonresponders. There was a vertebral predominance of the opacities (P < 0.0001). However, there was no difference between responders and nonresponders. When only the amount of consolidated lung located under the heart was evaluated, there was more consolidated tissue under the heart relative to total lung area in nonresponders than in responders (P = 0.01). CONCLUSIONS: There are no distinctive morphologic features in the pattern of lung disease measured by computed tomographic scanning performed with the patient in the supine position that can predict response to the prone position.

Aged↗

PubMed1993

[The hemodynamic and ventilatory effects between Trendelenburg and reverse Trendelenburg position during laparoscopy with CO2-insufflation].

Thirty ASA class I female patients underwent gynecologic pelvioscopy and laparoscopic cholecystectomy were included in this study. All of them received general anesthesia and certain volume of CO2 pneumoperitoneum. We evaluated the effect of positioning (Trendelenburg as group I and reverse Trendelenburg as group II) on hemodynamic parameters and ventilation. The hemodynamic parameters, ventilation, and arterial blood gas were determined at the following stages: (1) after 10 minutes of normoventilation and before CO2 pneumoperitoneum (as control), (2) 5 minutes after CO2 pneumoperitoneum and positioning, (3) 25 minutes after positioning, (4) 50 minutes after positioning, (5) 10 minutes after resumption of supine position and decompression of abdomen. Arterial blood pressure, heart rate, minute volume, end-tidal CO2, oxygen saturation and blood gas analysis were taken during normoventilation. We found that there was no statistical difference between either group in respect to hemodynamic parameters. For the ventilation, both groups had appropriate SpO2 during the period of CO2 pneumoperitoneum, but PaCO2 was significantly increased in group I 25 min after CO2 pneumoperitoneum and Trendelenburg positioning. Nonetheless, end-tidal CO2 was not significantly increased. pH value and PaCO2 did respectively decrease and increase significantly in group I 50 min after Trendelenburg position. However, no change was found in end-tidal CO2. All data were not significantly different after resumption of supine position and decompression of abdomen. Conclusively, except that pH and PaCO2 had changed after a period of Trendelenburg positioning with CO2 pneumoperitoneum, the patients who underwent laparoscopic surgery with normoventilation have no hemodynamic and respiratory change.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2006

Venous bubble count declines during strenuous exercise after an open sea dive to 30 m.

INTRODUCTION: The effect of post-dive exercise on bubble formation remains controversial, although the current practice of divers and aviators is to avoid strenuous exercise after diving. Previously, we have shown that exercising 24 h before a dive, or during a decompression stop, significantly reduces bubble formation in man. The objective of this study was to determine whether a short period of strenuous post-dive exercise promotes venous bubble formation. METHODS: Seven male military divers performed an open-sea field dive to a maximum depth of 30 m for 30 min. At maximum depth, subjects performed mild underwater fin swimming, followed by standard decompression. Diving was followed by a post-dive exercise session consisting of short, strenuous incremental upright cycle ergometry, up to 85% of maximal oxygen uptake, for about 10 min. Subjects were monitored for venous gas bubbles in the right heart with an echo-imaging system starting 20 min post-dive while in the supine position, during cycle ergometry in the seated upright position, and immediately after exercise in a supine position. RESULTS: The average number of bubbles was 1.5 +/- 1.4 bubbles x cm(-2) 20 min after diving. Changes in posture from supine to seated upright resulted in significant reduction of bubbles to 0.6 +/- 1.3 bubbles x cm(-2) (p = 0.043), with further reduction to 0.2 +/- 0.3 bubbles x cm(-2) at the end of exercise (p = 0.02). No cases of DCS or intra-pulmonary shunt were observed during or following post-dive exercise. DISCUSSION: These results suggest that post-dive strenuous exercise after a single field dive reduces post-dive gas bubble formation in well-trained military divers. Additional findings are needed for normal sports divers.

Adult↗

PubMed1992

Esophageal scintigraphy: reproducibility and normal ranges.

Esophageal scintigraphy has been rather widely used, but much debated as a simple screening method of esophageal dysfunction. However, reports of normal ranges, age dependence and reproducibility are very limited. We studied 60 healthy subjects with a mean age of 43 yr (26, 19, 15 subjects aged 20-39, 40-59, and 60-79 yr) to establish normal ranges and variations of esophageal mean transit time and residual activity measured by a radionuclide method using [99mTc] pertechnetate labeled water. Mean transit time was calculated by Zierler's formula. The median values and 95% percentiles of single measurements of MTT and residual activity in the supine position were 6.1 (3.2-11.5) sec and 11.5 (3.0-50)%, respectively. The coefficients of variation (CV) were 20%-35% for mean transit time and 85%-120% for residual activity in the sitting and supine positions. When double measurements were used, the CVs were reduced to 10% for MTT and 40% for residual activity in the supine position. The values did not change with age except for a higher frequency of spikes in subjects over 40 yr. The study has demonstrated that mean transit time for radiolabeled water in the esophagus of healthy subjects, measured by double determinations, has rather low, age-independent, interobserver and intersubject variabilities. In contrast, measurements of residual activity shows unacceptably high variations.

Adult↗

PubMed1997

Hemodynamic changes during laparoscopic cholecystectomy in patients with severe cardiac disease.

STUDY OBJECTIVE: To evaluate the hemodynamic changes and need for pharmacologic interventions during laparoscopic cholecystectomy in patients with severe cardiac dysfunction. DESIGN: Prospective open study. SETTING: University hospital. PATIENTS: 17 ASA physical status III and IV patients with severe cardiac dysfunction undergoing elective laparoscopic cholecystectomy. INTERVENTIONS: A standardized general anesthetic and surgical technique was used for all patients. In addition to routine monitoring, invasive hemodynamic monitoring included radial and pulmonary artery (PA) cannulation. MEASUREMENTS AND MAIN RESULTS: Hemodynamic parameters were recorded prior to induction of anesthesia, 5 minutes after induction of anesthesia but prior to incision, 5 minutes after carbon dioxide (CO2) insufflation and head-up tilt, every 10 minutes after change of position, after deflation of the abdomen and return to supine position, and 10 minutes after attaining supine position. Need for any pharmacologic interventions [to maintain mean arterial pressure (MAP) < 100 mmHg and/or systemic vascular resistance (SVR) < 2,000 dynes sec/cm-5, and/or cardiac index (CI) > 1.5 L/min/m2] and the incidence of any myocardial morbidity and mortality was noted. CI decreased significantly (p < 0.05) following insufflation and remained low until exsufflation. MAP, SVR, and PA occlusion pressure increased significantly (p < 0.05) after CO2 insufflation. Three of the 17 patients required administration of nitroglycerin to maintain the MAP and SVR within the accepted limits, one of whom also required administration of dobutamine to maintain CI. There was no myocardial morbidity or mortality in the perioperative period. CONCLUSION: Laparoscopic cholecystectomy in patients with severe cardiac dysfunction results in significant hemodynamic changes.

Adult↗

PubMedDate not supplied

Power spectral analysis of heart rate variability in children with aortic stenosis.

Aortic stenosis is a progressive disorder and can be the cause of serious arrhythmias and possibly sudden death. Evaluation and follow-up of the autonomic nervous system may provide some useful information for management of the disease. Our study aimed to examine heart rate variability in children with aortic stenosis in the supine position and to detect the changes in autonomic activity during head-up tilt testing. Sixteen patients and 11 healthy controls participated in the study. In the supine position, seven minutes of continuous echocardiographic (ECG) recording was performed, followed by four consecutive ECG recordings, each consisting of seven minutes in 70 degrees tilt position. To obtain power spectrums, the tachograms were taken on the autoregressive mode. The mean RR interval duration, standard deviation of RR interval, central frequencies of low and high frequency oscillations, their powers, total power and percents of normalized low and high frequency powers were accepted for statistics. There were no significant differences between the groups in the supine position. In tilt position, mean RR interval and its standard deviation were decreased in both groups. The central frequency of low freuquency power significantly (p<0.05) shifted to left, normalized low frequency power increased and normalized high frequency power decreased in the control group at the beginning of tilt position, but at the second phase of tilt position in the patient group. We conclude from the results that children with mild-to-moderate aortic stenosis reflect delayed response to sympathetic provocation.

Adolescent↗

PubMed1987

Postural relief of food impaction in a patient with stenosed esophagus--a case report.

A patient with past history of esophageal stenosis complained of sudden dysphagia in the erect position which was relieved transiently in the supine position. Initial esophagoscopy failed to detect any mass in the lumen. Esophagogram revealed shifting foreign body from lower stenotic site to upper dilated area with postural change from the erect to the supine position. A French bean was detected and removed during the second esophagoscopy.

Aphasia↗

PubMed2005

[Diaphragmatic weakness and its impact on respiratory function in primary myopathies].

BACKGROUND: Diaphragmatic weakness (DW) is a potential manifestation of primary myopathies. Prevalence and impact on respiratory function have not been defined. METHODS: Respiratory function (inspiratory vital capacity, IVC; maximal inspiratory muscle pressure, PImax; respiratory muscle effort, P (0.1)/PImax) and polysomnography/nocturnal capnometry (PtcCO(2)) was analysed in 49 patients with primary myopathies. DW was defined as > 25 % drop of IVC upon shift from upright to supine position. RESULTS: 19/54 (35 %) of patients, mostly AMD (68 %) and DMD (42 %) had DW. Restrictive ventilatory defect was moderate (IVC 37.2 +/- 26.2 %) in patients with and without DW (IVC 46 +/- 26 %, p = n. s.). DW caused a -33 %, respective - 25 %, supine drop of IVC and PImax, resulting in severe restriction in supine position (IVC (supine) 24.9 +/- 19.1 %, PImax (supine) 2.0 +/- 1.0 kPa, P (0.1)/PImax (supine) 19.9 +/- 12,8 %). All patients with DW and 75 % without had sleep-disordered breathing. This was significantly more severe in DW: 90 % (vs 17 % without DW) had continuous nocturnal hypoventilation (PtcCO(2) 62 +/- 2 mm Hg), 70 % (vs 18 % without DW) had combined nocturnal and diurnal hypercapnic respiratory failure (PaCO(2) 54,7 +/- 11.8 mm Hg). DW was an independent risk factor for sleep disordered breathing, for nocturnal and diurnal respiratory failure (r = 0.95, p < 0,05). Predictive thresholds thereof were accurate and identical to previously determined only for supine function data. CONCLUSION: DW is common in primary myopathies and predictive of nocturnal and diurnal respiratory failure. Supine respiratory function tests are necessary for clinical diagnosis and respiratory risk stratification.

Adolescent↗

PubMed2001

[Change of cross-sectional area of the right internal jugular vein: effect of Trendelenburg position and valsalva maneuver].

To compare the effect of Valsalva maneuver and 10 degrees Trendelenburg position on the right internal jugular vein (RIJV), we measured RIJV cross-sectional area using ultrasound imaging during these procedures. The study group consisted of 13 normal healthy volunteers (6 males, 7 females, aged 25-47) with no history of neck surgery or right internal jugular vein (RIJV) puncture. All ultrasound images were obtained at the level of the cricoid cartilage. The subjects were positioned supine, and the measurements were taken with the subjects supine, under Valsalva maneuver, and under 10 degrees Trendelenburg tilt position. The cross-sectional areas of the RIJV during Valsalva maneuver and 10 degrees Trendelenburg position compared to those with supine position were 314 +/- 162%, and 192 +/- 96%, respectively. We conclude that both procedures increase cross-sectional area of IRJV significantly and in this respect Valsalva maneuver is more effective than Trendelenburg position.

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↗

PubMed1999

Respiratory and haemodynamic effects of the prone position at two different levels of PEEP in a canine acute lung injury model.

This study was designed to examine whether the oxygenation response in the prone position differs in magnitude depending on the level of positive end-expiratory pressure (PEEP) applied in the supine position, and whether cardiac output (CO) increases in the prone position. In seven supine dogs, acute lung injury was established by saline lavage (arterial oxygen tension (Pa,O2)/inspiratory oxygen fraction (FI,O2) 17.8+/-9.6 kPa (134+/-72 mmHg)), and inflection point (Pflex) of the respiratory system was measured (6.6+/-1.4 cmH2O). Pa,O2/FI,O2 and CO of the supine and prone positions were obtained under the application of low PEEP and then under optimal PEEP (2 cmH2O below and above Pflex, respectively). The net increase in Pa,O2/FI,O2 by prone positioning was greater at low PEEP (27.3+/-12.0 kPa (205+/-90 mmHg)) than at optimal PEEP (4.4+/-13.0 kPa (33+/-98 mmHg)) (p=0.006). CO decreased significantly with optimal PEEP in the supine position (2.4+/-0.5 versus 3.1+/-0.4 L x min(-1) at baseline, p<0.001), and increased to 3.4+/-0.6 and 3.6+/-0.7 L x min(-1) in the prone position at 5 min and 30 min, respectively (both p=0.018). When the dogs were turned supine at optimal PEEP, CO again decreased (2.4+/-0.5 L x min(-1), p<0.001). In conclusion, the prone position augmented the effect of relatively low positive end-expiratory pressure on oxygenation, and attenuated the haemodynamic impairment of relatively high positive end-expiratory pressure in a canine acute lung injury model.

Animals↗

PubMed2001

Effects of posture and positive airway pressure on plasma atrial natriuretic peptide and renal urodilatin excretion.

AIMS: To determine whether a coupling of plasma atrial natriuretic peptide (ANP) and renal excretion of urodilatin (U(URO)V)--recently observed during supraphysiological concentrations of ANP--may also be detected during moderate changes in ANP levels, i.e. if ANP is increased by supine positioning and decreased by applying continuous positive airway pressure (CPAP). MATERIAL AND METHODS: We investigated 10 healthy male volunteers, orally hydrated with 200 ml water/h, in a randomized crossover study for periods of 1 hour following 2 protocols. Protocol 1: sitting and supine position. Protocol 2: sitting with and without a CPAP of 8 cm H2O. RESULTS: ANP increased ongoing from the sitting to the supine position (SIT-1: 13.2 +/- 4.7; SUP: 27.9 +/- 21.9 pg x ml(-1); p < 0.01) during protocol 1 and decreased after the onset of CPAP in seated subjects (SIT-2: 16.9 +/- 7.9; SIT-CPAP: 13.9 +/- 6.5 pg x ml(-1); p < 0.05) during protocol 2. U(URO)V decreased slightly, but not significantly, during protocol I (SIT-1: 63.9 +/- 21.7; SUP: 49.9 +/- 13.2 fmol x min(-1)) and remained unchanged after institution of CPAP in the sitting position (SIT-2: 68.5 +/- 25.2; SIT-CPAP: 68.5 +/- 50.2 fmol x min(-1)). Correlation analysis revealed no relationship between plasma ANP and U(URO)V. CONCLUSIONS: Moderate variations in the levels of ANP in water-loaded volunteers do not induce parallel changes in the urinary excretion of urodilatin.

Adult↗

PubMed1999

Tongue shape in obstructive sleep apnea patients.

Clinicians have long suspected that tongue shape differs between obstructive sleep apnea (OSA) patients and normal subjects. The purpose of this study was to determine whether such differences exist. Because of the difficulty in specifying reproducible homologous landmarks for the tongue, a morphometric technique-the eigenshape analysis-was used. The eigenshape analysis transforms an outline contour into a set of discrete numbers that are tangent angles of the curvature along the outline at each digitized point on the outline. Pairs of cephalograms were taken of 80 male patients in upright and supine positions. The subjects were subgrouped into four categories according to severity of symptoms. The contour of the tongue was traced, digitized, and subgrouped. When the major portion of the tongue shape variations in the supine position were graphically compared between subgroups, variations in the nonapneic group were distinguished from those in the apneic groups. The results suggest that the eigenshape analysis on cephalograms in the supine position may be a useful tool to distinguish OSA subjects from nonapneic subjects.

Adult↗

PubMed2003

Nitric oxide synthase inhibition does not affect regulation of muscle sympathetic nerve activity during head-up tilt.

To test the hypothesis that systemic inhibition of nitric oxide (NO) synthase does not alter the regulation of sympathetic outflow during head-up tilt in humans, in eight healthy subjects NO synthase was blocked by intravenous infusion of NG-monomethyl-L-arginine (L-NMMA). Blood pressure, heart rate, cardiac output, total peripheral resistance (TPR), and muscle sympathetic nerve activity (MSNA) were recorded in the supine position and during 60 degrees head-up tilt. In the supine position, infusion of L-NMMA increased blood pressure, via increased TPR, and inhibited MSNA. However, the increase in MSNA evoked by head-up tilt during L-NMMA infusion (change in burst rate: 24 +/- 4 bursts/min; change in total activity: 209 +/- 36 U/min) was similar to that during head-up tilt without L-NMMA (change in burst rate: 23 +/- 4 bursts/min; change in total activity: 251 +/- 52 U/min, n = 6, all P > 0.05). Moreover, changes in TPR and heart rate during head-up tilt were virtually identical between the two conditions. These results suggest that systemic inhibition of NO synthase with L-NMMA does not affect the regulation of sympathetic outflow and vascular resistance during head-up tilt in humans.

Adult↗

PubMed1988

The effect of the M1-selective telenzepine on esophageal acid exposure in healthy volunteers.

In order to study the effect of the new M1-selective antimuscarinic compound telenzepine on physiological esophageal acid exposure, ten healthy volunteers underwent a 24-hour esophageal pH-monitoring during a one week treatment with either tablets containing telenzepine 3 mg nightly or placebo in a double-blind cross-over trial. Side-effects were recorded, and stimulated salivary output was assessed. Using a cut-off pH less than 4, under telenzepine a significant reduction of reflux time and of maximum reflux duration was observed in supine position. Using a cut-off pH less than 2, reflux time was reduced during and after meals, number of refluxes was decreased during meals, and esophageal clearance was improved with telenzepine in supine position. Telenzepine reduced salivary output significantly on day 4 and on day 7. From the results it can be concluded that the drug is not contraindicated in peptic ulcer patients with heartburn. As telenzepine reduces gastroesophageal reflux time during and after meals and in supine position it may be tried as adjuvant treatment in esophageal reflux disease.

Adult↗