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At least 667 records · Page 37Linked to original sources

PubMed2000

New descriptors of homogeneity of the propagation of ventricular repolarization.

Available descriptors of irregularities of ventricular repolarization are of limited clinical value. We studied the effect of autonomic variations on several new descriptors of the three-dimensional T loop. Twelve-lead digital ECGs were recorded continuously in 40 healthy subjects at baseline in the supine position, during postural changes (supine-->sitting-->standing-->supine-->standing), and during Valsalva maneuver performed three times in the supine and three times in the standing positions. A minimum dimensional space was constructed from the 12-lead ECG, using singular value decomposition, on the basis of median ECG beats constructed from 10-second consecutive ECG recordings. Temporal variations (TLA and PL, which measure the T loop area, and LD, the interlead relationship during repolarization) and wavefront direction descriptors (TCRT, the deviation between the QRS and T vectors) were calculated and expressed as normalized values. Values of TLA, PL, and TCRT were significantly lower in the sitting than in the supine position (-38,139 +/- 9099 vs 47,133 +/- 7511, -0.017 +/- 0.005 vs 0.033 +/- 0.005 and -0.032 +/- 0.019 vs 0.071 +/- 0.015, respectively, P < 0.001 for all) and decreased further in the standing position (-88,288 +/- 14,468, -0.067 +/- 0.013, -0.198 +/- 0.025, respectively, P < 0.001 for all). LD increased from supine to sitting (98.7 +/- 29.4 vs -87.5 +/- 15.2, P < 0.001) and increased further, though nonsignificantly in the standing position (118.3 +/- 35.2). TLA, PL, and TCRT decreased from baseline during Valsalva in the supine (-34,118 +/- 11,424 vs 62,234 +/- 12,215, -0.038 +/- 0.014 vs 0.065 +/- 0.010, -0.08 +/- 0.03 vs 0.10 +/- 0.02, respectively, P < 0.001 for all) and standing positions (-108,263 +/- 21,051 vs -68,909 +/- 10,271, -0.109 +/- 0.014 vs -0.048 +/- 0.009, -0.30 +/- 0.035 vs -015 +/- 0.016, respectively, P < 0.05 for all). LD was significantly increased by Valsalva in the supine position (13 +/- 46 vs -153 +/- 30, P < 0.001) and nonsignificantly in the standing position (99 +/- 50 vs 86 +/- 30, P = NS). There were significant correlations among TLA, PL, and LD, and no significant correlation between TCRT and any of the temporal variation descriptors. These new temporal and wavefront direction descriptors are sensitive and rapid detectors of autonomic effects on ventricular repolarization.

Adolescent↗

PubMed2004

Does the level of chronic physical activity alter heart rate variability in healthy older women?

In the present study, we investigated the effects of three levels of chronic physical activity on HRV (heart rate variability) in healthy older women. ECG recordings were taken in three (low-, moderate- and high-) activity groups in supine position with free and with controlled breathing, and during orthostatic stress. Temporal and spectral HRV indices were obtained from the ECG signal processing. The main results showed that, in supine position with free and controlled breathing, the HF (high-frequency) spectral component (P<0.01) and the rMSSD (square root of the mean squared differences) between two adjacent RR intervals (P<0.05 and P<0.01 respectively) were elevated in the high-activity group compared with the low-activity group. No significant difference was observed between groups during the orthostatic test. Within groups, in the supine position, the change from free to controlled breathing produced a decrease in the LF (low-frequency) spectral component in all three groups (P<0.01). The change from supine to standing position produced a decrease in RR in all three groups (P<0.05 in low- and moderate-activity groups, and P<0.01 in high-activity group); the rMSSD and the HF spectral component decreased only in the high-activity group (P<0.01). In conclusion, this study performed on older women showed that parasympathetic indices of resting HRV were significantly elevated in a high physical activity group compared with in a low physical activity group. Furthermore, parasympathetic indices of HRV decreased during an orthostatic test only in the high-activity group. The influence of chronic moderate physical activity on HRV in older women was small in the present study.

Aged↗

PubMed1979

Ventilation-perfusion lung imaging in diaphragmatic paralysis.

We have described a patient with paralysis of the diaphragm, in whom dyspnea, hypoxemia, and hypercapnia increased when he changed from the upright to the supine position. Ventilation (V) and perfusion (P) images of the right lung appeared to be normal and remained nearly the same in the upright and supine positions. In contrast, V and P images of the left lung were smaller than those of the right lung in the upright position and decreased further in the supine position. In addition, the ventilation image of the left lung was much smaller than the perfusion image in both positions.

Diaphragm↗

PubMed1997

[Work of breathing in differentiation of various forms of sleep-related breathing disorders].

BACKGROUND: In contrast to the obstructive sleep apnoea syndrome (OSA) the obesity-hypoventilation syndrome (OHS) is characterised by persistent hypercapnia during the day and predominant hypoventilation during sleep. In this study we wanted to know whether work of breathing (WOB) in a sitting and supine position separates both groups. PATIENTS AND METHODS: OSA population: 20 men, 50.5 +/- 9.2 years, Body Mass Index (BMI: 54.1 +/- 6.9 kg/m2, pO2: 65.6 +/- 6.6 mmHg, pCO2: 40.6 +/- 3.1 mmHg, OHS-group: 14 patients, 13 men age: 53.1 +/- 9.3 years, BMI: 53.1 +/- 9.3 kg/m2, pO2: 51.8 +/- 10.5 mmHg, pCO2: 53.8 +/- 9.2 mmHg. The control group consisted of 10 normal weighted subjects. The intrathoracic pressures were assessed by an oesophageal catheter; at the same time, the minute ventilation (VE) and the breathing frequency (fb) were measured via a pneumotachygraph. The area under the pressure-volume loop was correlated to WOB. After reaching steady state VE, fb, and WOB were determined in sitting and supine position. RESULTS: In the OSA-group the apnoea index (AI) was 48.6 +/- 17.7/h and the respiratory disturbance index (RDI) was 66.3 +/- 19.4/h. The forced expiratory volume (FEV1) was 77.3 +/- 23% pred. and the vital capacity (VC) was 76.3 +/- 18.6% pred.; 7 out of 20 patients suffered from chronic bronchitis. In the OHS-group the AI was 21.5 +/- 19/h and the RDI 44.3 +/- 28.2/h. The majority of OHS patients had an airway obstruction (FEV1: 55.8 +/- 17.5% pred., VC: 58.8 +/- 12.8% pred.); 12 out of 14 patients suffered from chronic bronchitis. Compared to the OSA population WOB in the OHS group was significantly higher both in the sitting (0.67 +/- 0.28 J/I versus 1.04 +/- 0.32 J/I, p < 0.001) and supine positions (1.23 +/- 0.25 J/I versus 1.91 +/- 0.43 J/I, p < 0.001). Compared to the sitting position VE and fb did not change significantly in both groups lying supine. CONCLUSIONS: Compared to the OSA group at the same BMI the WOB of the OHS population was significantly increased in the sitting and supine position. The main reason for these findings may be the increased airway obstruction due to chronic bronchitis. Both populations did not change the breathing patterns during the different positions.

Adult↗

PubMed2005

Effects of the muscle pump and body posture on cardiovascular responses during recovery from cycle exercise.

The purpose of the study was to characterize the effects of muscular contractions (the muscle pump) and body posture on cardiovascular responses during recovery from moderate exercise in the upright-sitting or supine positions. Heart rate (HR), stroke volume (SV), and cardiac output (CO) were measured in seven young male subjects at rest and during 10-min of cycle exercise at 60% of peak oxygen uptake (VO2peak). This was followed by either complete rest for 5 min (inactive recovery) or cycling at VO2peak for 5 min (active recovery) in the upright or supine positions. In the upright position, an initial rapid decrease in HR was followed by a gradual decrease in HR, and this response was similar when comparing inactive and active recoveries. Upright SV during inactive recovery decreased gradually to the pre-exercise resting level, whereas upright SV during active recovery remained significantly elevated. In contrast, in the supine position, the HR during active recovery decreased, but remained significantly higher than that during inactive recovery. Changes in supine SV were similar when comparing inactive and active recovery. Thus, maintenance of SV and HR resulted in significantly greater CO during active recovery than during inactive recovery, regardless of body position. HR was greater during supine active-recovery than during supine inactive-recovery, and there was no difference in SV. These data suggest that the muscle pump is less important in facilitating venous return and vagal resumption in the supine position as compared to the upright position.

Adult↗

PubMed2004

Prone versus supine patient positioning during gated 99mTc-sestamibi SPECT: effect on left ventricular volumes, ejection fraction, and heart rate.

UNLABELLED: Gated myocardial perfusion SPECT allows assessment of left ventricular end-diastolic volume (EDV), left ventricular end-systolic volume (ESV), left ventricular stroke volume (SV), and left ventricular ejection fraction (LVEF). Acquiring images with the patient both prone and supine is an approved method of identifying and reducing artifacts. Yet prone positioning alters physiologic conditions. This study investigated how prone versus supine patient positioning during gated SPECT affects EDV, ESV, SV, LVEF, and heart rate. METHODS: Forty-eight patients scheduled for routine myocardial perfusion imaging were examined with gated (99m)Tc-sestamibi SPECT (at rest) while positioned prone and supine (consecutively, in random order). All parameters for both acquisitions were calculated using the commercially available QGS algorithm. RESULTS: Whereas EDV and SV were significantly lower (P < 0.0004) for prone acquisitions (EDV, 110.5 +/- 39.1 mL; SV, 55.9 +/- 13.3 mL) than for supine acquisitions (EDV, 116.9 +/- 36.2 mL; SV, 61.0 +/- 14.5 mL), ESV and LVEF did not differ significantly. Heart rate was significantly higher (P < 0.0001) during prone acquisitions (69.1 +/- 10.5 min(-1)) than during supine acquisitions (66.5 +/- 10.0 min(-1)). CONCLUSION: The observed position-dependent effect on EDV, SV, and heart rate might be explained by decreased arterial filling and increased sympathetic nerve activity. Hence, supine reference data should not be used to classify the results of prone acquisitions.

Adult↗

PubMed1993

The influence of position and PEEP on arterial blood gas during operation.

From December, 1990 to December, 1991, we studied the influence of PEEP and positional change to arterial blood gas in 60 ASA class II or III, aged 20 to 65 years, non-obese patients. The patients were assigned randomly into six groups. Group 1: head down position without PEEP. Group 2: head down position with PEEP 5 cmH2O. Group 3: lithotomy position without PEEP. Group 4: lithotomy position with PEEP 5 cmH2O. Group 5: supine position without PEEP. Group 6: supine position with PEEP 5 cmH2O. Blood gas analysis were performed at 5, 15, 30, 60, 120, and 180 minutes after positional change in group 1-4 and after anesthesia in group 5 and 6. The ventilator settings were: tidal volume -10 ml x 25 x (height in meters)2, rate 8/min. The results of significant difference inter-grouply were: PaO2 at 15 minutes; PaCO2 at 5 minutes; pH at 60, 120, and 180 minutes; base excess (BE) at 120 and 180 minutes. As the time progressed, PaO2 decreased in group 1, 2, and 3; PaCO2 decreased in group 3 and 5; pH decreased in group 3; BE decreased in all groups. PaCO2 were between 30-40 mmHg and no hypocarbia produced in all groups. In conclusion, ventilation of the non-obese patient based on 10 ml x 25 x (height in meters)2 x 8/min produce normocarbia and PaO2 more than 80 mmHg with 50% oxygen. No significant difference of PaO2 were found whether there were position change or PEEP 5 cmH2O.

Adult↗

PubMed2004

Measurement of inferior vena cava diameter for evaluation of venous return in subjects on day 10 of a bed-rest experiment.

We evaluated the usefulness of measurements of the inferior vena cava (IVC) diameters on abdominal echograms as an indicator of changes of venous return in subjects with orthostatic intolerance (OI) induced by simulated microgravity. We performed a standing test and recorded the IVC diameters on abdominal echograms in 12 subjects placed on a 20-day 6 degrees head-down-tilt bed-rest experiment. We found that different patterns of changes in IVC diameter occurred in the standing test on day 10 of the experiment; in five subjects with a marginal decrease in pulse pressure, IVC diameters in the upright position were markedly decreased compared with those in the supine position. In five subjects with feelings of discomfort, the IVC diameters in the upright position distended or did not decrease from those in the supine position. These results suggested that the changes in IVC diameter on the standing test indicated the presence of various types of hemodynamic responses of OI caused by simulated microgravity. In this study, we also evaluated changes in body-water compartments by conducting multifrequency bioelectrical impedance analysis. Longitudinal data analysis showed that the total body-water-to-fat-free mass and extracellular fluid-to-fat-free mass ratios decreased during the experimental period and recovered thereafter, and that the ratio of intracellular fluid to fat-free mass decreased during the experiment. No significant difference in changes in body-water compartments was seen among subjects with different patterns of changes in IVC diameters. Measurement of IVC diameter was useful to estimate hemodynamic changes in subjects with OI.

Adult↗

PubMedDate not supplied

A new noninvasive method for the accurate and precise assessment of varicose vein diameters.

The feasibility and reproducibility of a new ultrasonic method for the direct assessment of maximal varicose vein diameter (VVD) were evaluated. A study was also performed to demonstrate the capacity of the method to detect changes in venous diameter induced by a pharmacologic treatment. Patients with varicose vein disease were recruited. A method that allows the precise positioning of patient and transducer and performance of scans in a gel-bath was developed. Maximal VVD was recorded both in the standing and supine positions. The intraassay reproducibility was determined by replicate scans made within 15 minutes in both positions. The interobserver variability was assessed by comparing VVDs measured during the first phase baseline examination with those obtained during baseline examinations in the second phase of the study. The error in reproducibility of VVD determinations was 5.3% when diameters were evaluated in the standing position and 6.4% when assessed in the supine position. The intramethod agreement was high, with a bias between readings of 0.06 +/- 0.18 mm and of -0.02 +/- 0.19 mm, respectively, in standing and supine positions. Correlation coefficients were better than 0.99 in both positions. The method appears to be sensitive enough to detect small changes in VVDs induced by treatments. The proposed technique provides a tool of potential valid use in the detection and in vivo monitoring of VVD changes in patients with varicose vein disease. The method offers an innovative approach to obtain a quantitative assessment of varicose vein progression and of treatment effects, thus providing a basis for epidemiologic surveys.

Adult↗

PubMed1999

Improvement in oxygenation by prone position and nitric oxide in patients with acute respiratory distress syndrome.

OBJECTIVE: Inhaled nitric oxide (NO) and prone position improve arterial oxygenation in patients with the acute respiratory distress syndrome. This study was undertaken to assess the combined effects of NO and prone position in these patients. DESIGN: Prospective clinical study. SETTING: General intensive care service in a community teaching hospital. PATIENTS: 14 mechanically ventilated adult patients with the acute respiratory distress syndrome (mean lung injury score 3.23+/-0.27). MEASUREMENTS AND RESULTS: We measured hemodynamic and oxygenation parameters in the supine position and 2 h later in the prone position, before and during inhalation of 10 ppm NO. A positive response in oxygenation was defined as a > or =20% increment in the arterial oxygen tension/fractional inspired oxygen ratio (PaO2/FIO2). In the prone position PaO2/FIO2 increased significantly (from 110+/-55 to 161+/-89 mm Hg, p<0.01) and venous admixture decreased (from 38+/-12 to 30+/-7%, p<0.01) compared to the supine position. Ten of the 14 patients were responders in the prone position. In the supine position, inhalation of NO improved oxygenation to a lesser extent, increasing PaO2/FIO2 to 134+/-64 mm Hg (p<0.01) and decreasing venous admixture to 35+/-12%, (p<0.01). Five of the 14 patients responded to NO inhalation supine and 8 of 14 responded prone (p = 0.22). The combination of NO therapy and prone positioning was additive in increasing PaO2/FIO2 (197+/-92 mm Hg) and decreasing venous admixture (27+/-8%) (p<0.01). This combination also showed a positive oxygenation response on compared to the supine value without NO in 13 of the 14 patients (93 %). NO-induced changes in PaO2/FIO2 were correlated to changes in pulmonary vascular resistance only in the prone position. CONCLUSIONS: In patients with the acute respiratory distress syndrome, the combination of NO and prone position is a valuable adjunct to mechanical ventilation.

Administration, Inhalation↗

PubMed1991

Relative contribution of gravity to pulmonary perfusion heterogeneity.

We designed a series of experiments and analyses to quantify the contribution of gravity to pulmonary perfusion heterogeneity. Regional pulmonary perfusion was measured in five anesthetized and ventilated dogs in both supine and prone positions by use of radiolabeled microspheres injected during apnea at functional residual capacity. Measurements of flow were repeated in each position, and the sequence of positions was prospectively designed to nullify any effect of order. The lungs of each animal were excised, perfused with saline until clear, dried at an inflation pressure of 25 cmH2O, and cut into 1.9-cm3 pieces. Each piece was weighed and the radioactivity determined in a scintillation counter. Measurement errors were minimized by excluding lung pieces that had greater than 25% airway and weighed less than 10 mg or greater than 60 mg. Weight-normalized flows in each position and repetition were determined for each lung piece. An analysis of variance model was used to identify the percentage of variation in regional flow that was due to position (supine vs. prone), to random error and time (measurement and repetition), and to structure, where structure was defined as the component of flow that remained constant across position and replication. The contributions of position, error/time, and structure to the total variability of flow across the five dogs were 7.8 +/- 0.6, 8.4 +/- 8.3, and 83.8 +/- 8.4%, (SD), respectively. Because the contribution of position represents the additive effect of gravity between two opposite positions, the contribution of gravity to perfusion heterogeneity in one position may be as little as 4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1997

Body position and late postoperative nocturnal hypoxaemia.

Thirteen patients were monitored for nocturnal body position (supine vs. side) and arterial oxygen saturation pre-operatively and on the second postoperative night after major abdominal surgery. The number of positional changes were significantly decreased after operation (p < 0.05) with a trend towards more time spent in the supine position (p = 0.1). Individual mean arterial oxygen saturation decreased postoperatively (p < 0.05) but without a difference between the supine and side positions (p = 0.9). Pre-operatively, episodic desaturations were significantly more frequent in the supine position than on the side (p < 0.05) but not postoperatively. Pain was the most frequent reason for decreased nocturnal movements.

Adult↗

PubMed2002

Characteristics of acid reflux in Barrett's esophagus.

To determine the relationship between Barrett's esophagus (BE) and features of gastroesophageal acid reflux, 24 h esophageal pH monitoring was performed in 90 patients. The patients were divided into 3 groups: 31 subjects with BE, 21 with mild esophagitis and 38 with severe esophagitis. The following parameters were evaluated: the percentage time of pH < 4; the number of reflux episodes over 5 min; the duration of longest episodes and DeMeester score over total period and the auterior three parameters in erect and supine position. All these parameters in BE were significantly different from those with mild esophagitis (P < 0.01) and not significantly different from those with severe esophagitis (P > 0.05). During supine position all the above parameters in BE were significantly different from those with reflux esophagitis (P < 0.05). It is concluded that the quantity of acid reflux is not an important factor in development of BE in gastroesophageal reflux (GER), and the acid reflux in supine position might be important in development of BE in GER.

Adult↗

PubMed2000

Sustained microgravity reduces the human ventilatory response to hypoxia but not to hypercapnia.

We measured the isocapnic hypoxic ventilatory response and the hypercapnic ventilatory response by using rebreathing techniques in five normal subjects (ages 37-47 yr) before, during, and after 16 days of exposure to microgravity (microG). Control measurements were performed with the subjects in the standing and supine postures. In both microG and in the supine position, the hypoxic ventilatory response, as measured from the slope of ventilation against arterial O(2) saturation, was greatly reduced, being only 46 +/- 10% (microG) and 52 +/- 11% (supine) of that measured standing (P < 0.01). During the hypercapnic ventilatory response test, the ventilation at a PCO(2) of 60 Torr was not significantly different in microG (101 +/- 5%) and the supine position (89 +/- 3%) from that measured standing. Inspiratory occlusion pressures agreed with these results. The findings can be explained by inhibition of the hypoxic but not hypercapnic drive, possibly as a result of an increase in blood pressure in carotid baroreceptors in microG and the supine position.

Adult↗

PubMed1992

Effect of positioning on the breathing pattern of preterm infants.

Respiration, as judged by gas exchange and pulmonary function, is improved in preterm infants kept in the prone rather than the supine position. The influence of position on the breathing pattern as documented by the pneumogram was studied in 14 stable preterm infants with recent clinical apnoea. Ten of the infants had oximetry and nasal flow studies simultaneously with the impedance pneumogram. Each infant had consecutive nocturnal pneumograms, one in the prone, one in the supine position. The infants were kept for more than six hours in the assigned position. A significant increase in apnoea density and in periodic breathing was found in the supine v the prone position (mean (SE) 4.5 (0.7)% v 2.5 (0.5)%, and 13.6 (3.2)% v 7.7 (2.2)%, respectively). There was no positional difference in the incidence of bradycardia and prolonged apnoea. The examination of obstructive apnoea, mixed apnoea, and cyanotic spells did not reveal a consistent disparity between the two positions. These findings indicate an increase in central apnoea in preterm infants kept predominantly in the supine position. Possible relations of positional changes to lung mechanics are discussed. When evaluating pneumograms, attention must be given to the position in which they were performed.

Apnea↗

PubMedDate not supplied

A study of autonomic status and its effect on ventilatory functions in bronchial asthma.

The present study was undertaken to evaluate the autonomic nervous function in patients with bronchial asthma after indirect autonomic stimulation by seven different manoeuvres. A total of 30 cases of bronchial asthma and 20 healthy matched controls were studied after excluding all other diseases and drugs which could have a modulating effect on autonomic function. The tests used were: heart rate responses to the Valsalva manoeuvre, deep breathing, intravenous atropine, carotid sinus massage and standing from the supine position, and, the blood pressure responses to sustained handgrip and to standing from the supine position, the former five being tests of parasympathetic function and the latter two of sympathetic function. A significant difference in responses was observed in asthmatics who showed heightened cardiovascular responses to tests of parasympathetic function as compared to controls. Ventilatory function parameters (FVC and PEFR) also showed a parallel enhanced response (marked decrease) to parasympathetic stimulation by Valsalva manoeuvre, deep breathing and carotid sinus massage in asthmatics compared to controls. This aspect of differences in ventilatory response has not been previously reported in literature. No significant differences were found in the blood pressure responses to sustained handgrip and to standing from the supine position. Correlations between the autonomic status of the asthmatics with the clinical characteristics of the patients were analysed.

Adolescent↗

PubMed1996

Effect of apparatus on functional residual capacity.

As the route of breathing and use of airway apparatus such as mask, mouthpiece and noseclip can alter breathing pattern, this study has used the helium dilution method to estimate the effects of mouthpiece and mask breathing on functional residual capacity (FRC) in the supine position, and the change in FRC that occurs between the sitting and supine positions while breathing by mouthpiece. In 13 normal subjects, breathing by mouthpiece, FRC was smaller, by a median of 1.07 litre (interquartile values 0.73-1.43 litre) in the supine compared with the sitting position (P < 0.01), but residual volume (RV) did not change significantly. FRC measured in the supine position was significantly greater when breathing by mask than by mouthpiece (0.25, 0.04-0.38 litre) and RV was greater by similar amounts (0.20, -0.02 to 0.49 litre). This difference may result from increased inspiratory activity while breathing via the mask.

Anesthesiology↗

PubMed1999

A simple method to increase the diagnostic efficiency of gastroesophageal scintigraphy using the knee-chest position.

PURPOSE: The influence of patient posture on the incidence and severity of gastroesophageal reflux is well known. Scintigraphic imaging, however, is routinely performed with the patient lying in the supine position, because current gamma camera designs do not allow for changes to the angle of the patient table. METHODS: To overcome this difficulty and to increase the diagnostic sensitivity of scintigraphy, we used an alternative patient position. Twenty-seven adult patients (eight men, 19 women; mean age, 47.5+/-11.5 years) with gastroesophageal reflux disease were prospectively studied consecutively using two body positions, the supine and the knee-chest positions. Each consisted of dynamic acquisition of 450 seconds. An entire study for each patient required only 15 minutes. Images were interpreted qualitatively by three observers. RESULTS: Although gastroesophageal reflux was positively identified in only 9 of 27 (33%) patients using the supine position, 20 of 27 (74%) patients were shown to have gastroesophageal reflux in the knee-chest position (P < 0.05). No reflux was detected in seven patients using both positions. In five patients, whose study results were positive using both positions, the number of reflux episodes was greater in the knee-chest position compared with the supine position. CONCLUSION: The knee-chest position increases the diagnostic efficiency of gastroesophageal reflux scintigraphy.

Female↗