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PubMed2002

Hemodynamic changes and baroreflex gain in the supine hypotensive syndrome.

OBJECTIVE: The purpose of this study was to determine whether supine hypotensive syndrome is caused by a decreased baroreflex gain that results in inadequate compensatory responses to restore cardiac output. STUDY DESIGN: Ten third-trimester gravid women with symptoms that were suggestive of supine hypotensive syndrome and 10 control subjects without symptoms were studied. Patients were studied initially for 30 minutes in the lateral recumbent position with continuous heart rate, blood pressure, external cardiotocography, and cardiac output determinations every 5 minutes. After 30 minutes, the patient was repositioned supine for up to an additional 30 minutes, and all measurements were repeated similarly. This lateral-supine sequence was repeated twice or until symptoms precluded further testing. RESULTS: The two groups were demographically similar. With maternal position change to supine, cardiac output (-2.7 L/min vs -1.0 L/min, P =.04) and mean arterial blood pressure (-10.7 mm Hg vs -2.5 mm Hg, P =.03) were respectively lower, and heart rate (+26.9 vs +14.4 beats/min, P =.04) was higher in the subjects with supine hypotensive syndrome than in the control subjects. Baroreflex gain, however, did not differ between the subjects with supine hypotensive syndrome and control subjects (P =.26). CONCLUSION: We were unable to demonstrate a decrease in baroreflex gain as a possible cause of supine hypotensive syndrome. Inadequate pelvic collateral circulation that leads to a greater decrease in cardiac output may be causative in the syndrome.

Baroreflex↗
PubMed2001

A mechanical study of the moment-forces of the supinators and pronators of the forearm.

We determined the torque generated by the muscles rotating the forearm at varying degrees of pronation and supination. We used 8 human cadaveric upper extremity specimens with the humerus and ulna rigidly fixed with the elbow in 90 degrees of flexion, while free rotation of the radius around the ulna was allowed. The tendons of the flexor carpi ulnaris (FCU), extensor carpi ulnaris (ECU), supinator, biceps, pronator teres (PT), and the pronator quadratus' (PQ) superficial and deep heads were isolated. After locking the forearm at intervals of 10 degrees from 90 degrees of pronation to 90 degrees of supination, we loaded each muscle/tendon with a ramp profile. We found that the biceps and supinator are both active supinators, the biceps generating four times more torque with the forearm in a pronated position. As for pronation, the PT and both heads of the PQ are active throughout the whole rotation, being most efficient around the neutral position of the forearm. The ECU and FCU contribute significantly less to pronation and supination torque. However, they do generate potential pronating torque while the forearm is positioned maximally in supination and, to a lesser extent, potential supination torque while the forearm is positioned maximally in pronation.

Adult↗
PubMed2000

Emergence from anesthesia in the prone versus supine position in patients undergoing lumbar surgery.

BACKGROUND: Conventional supine emergence in patients undergoing prone lumbar surgery frequently results in tachycardia, hypertension, coughing, and loss of monitoring as the patient is rolled supine. The prone position might facilitate a smoother emergence because the patient is not disturbed. No data describe this technique. METHODS: Fifty patients were anesthetized with fentanyl, nitrous oxide, isoflurane, and rocuronium. By the conclusion of surgery, all patients achieved spontaneous ventilation and full reversal of neuromuscular blockade in the prone position, as the volatile anesthetic level was reduced. Baseline heart rate and mean arterial pressure were recorded. Patients were then randomized at time 0 to the supine (n = 24) or prone (n = 21) position as 100% oxygen was administered. Patients in the supine position were then rolled over, while those in the prone position remained undisturbed. Heart rate, mean arterial pressure, and coughs were recorded until extubation. Tracheas were extubated on eye opening or purposeful behavior. RESULTS: When compared with the supine group, prone patients had significantly less increase in heart rate (P = 0.0003, maximum increase 9.3 vs. 25 beats/min), less increase in mean arterial pressure (P = 0.0063, maximum increase 4.8 vs. 19 mmHg), less coughing (P = 0.0004, 7.0 vs. 23 coughs), and fewer monitor disconnections (P < 0.0001). Time to extubation from time 0 was similar (4.0 vs. 3.7 min, prone vs. supine). No one required airway rescue. There was no significant difference in need for restraint (three prone, four supine). CONCLUSIONS: Prone emergence and extubation is associated with less hemodynamic stimulation, less coughing, and less disruption of monitors, without specifically observed adverse effects, when compared with conventional supine techniques.

Androstanols↗
PubMed1998

Does it matter whether blood pressure measurements are taken with subjects sitting or supine?

BACKGROUND: Several guidelines for the management of hypertension do not give special preference to a specific position of the patient during blood pressure measurement, suggesting that blood pressure readings taken with patients sitting and with patients supine are interchangeable. OBJECTIVE: To test whether there is any difference between the blood pressure readings with patients sitting and supine. DESIGN AND METHODS: Blood pressure and heart rate were measured three times each for 245 subjects (171 hypertensives), with subjects both sitting and supine, simultaneously on both arms, with a Hawksley random-zero sphygmomanometer on the right arm and a semi-automatic oscillometric device (Bosomat) on the left arm. The sequence of the two positions was randomized. The procedure was repeated on a second occasion for 49 subjects (41 hypertensives) with the sequence of the positions reversed. Because there was no systematic difference among the three readings per position, the averages of the three blood pressure and heart rate readings with subjects sitting and supine were compared and the influences of age, body mass index, hypertension and medication on the difference were examined. RESULTS: We found no influence of the subject's body posture on the systolic blood pressure. We found a higher diastolic blood pressure [by 5.2+/-0.4 mmHg (mean+/-SEM), P< 0.001 with Hawksley random-zero sphygmomanometer] and a greater heart rate [by 1.5+/-0.3 beats/min (mean+/-SEM), P< 0.001] with subjects sitting. The sitting minus supine differences for diastolic blood pressure and heart rate decreased significantly with increasing age (P< 0.001). We found no effect of body mass index, hypertension and medication on the sitting - supine differences. CONCLUSIONS: The subject's body posture influenced especially the diastolic blood pressure and heart rate, both of them being significantly higher with patients sitting rather than supine. This effect decreased with age. Thus, for indirect blood pressure measurement, diastolic blood pressure values obtained with subjects sitting and supine cannot automatically be regarded as equivalent.

Adult↗
PubMed1996

Cardiovascular and peak VO2 responses to supine exercise: effects of age and training status.

Although stroke volume during exercise is affected by aging and posture, few studies have carefully examined the heart rate, blood pressure, and peak oxygen uptake (VO2) responses of older subjects to supine exercise. The present study examined these responses during graded supine cycling in younger (21-30 yr) and older (51-62 yr) untrained (Treadmill VO2max = 47.0 vs 32.3 ml.kg-1.min-1) and endurance-trained (66.3 vs 52.7 ml.kg-1.min-1) men (N = 6/group). All subjects had lower (P < 0.05) peak VO2 (ml.min-1) and peak heart rate responses during supine cycling compared with treadmill exercise. Additionally, the age-related reduction in peak VO2 (approximately 20-30%) was similar for supine compared with treadmill testing, even when normalized to fat-free leg volume and fat-free mass, respectively. However, at given absolute intensities (VO2) of supine exercise, heart rates were 10-15 beats.min-1 less (P < 0.05) in both older groups. Across relative supine work intensities (% of peak), systolic pressure increased most rapidly in the younger trained and older untrained groups. These findings suggest that the effects of aging on peak VO2 are similar during treadmill and supine exercise in both endurance-trained and untrained men. These data also indicate that the heart rate response to supine exercise is attenuated in healthy older men and contributes to their reduced peak VO2.

Adult↗
PubMed1998

Do supine oblique views provide better imaging of the cervicothoracic junction than swimmer's views?

OBJECTIVE: To determine whether a swimmer's view or supine (trauma) oblique views are more likely to visualise the lower cervical spine when a lateral view fails to show the cervicothoracic junction. DESIGN: A prospective study comparing two 20 week periods. In the first phase the swimmer's view was performed as an additional view when the cervicothoracic junction was not demonstrated. In the second phase paired supine oblique views replaced the swimmer's view. RESULTS: 230 patients were included in the first phase, of whom 60 required swimmer's views. In the second phase 62 of 197 patients required supine oblique views. Radiology analysis of 53 pairs of supine oblique views showed that the vertebral bodies were adequately demonstrated at the cervicothoracic junction in only 20 patients (38%) compared with 22 in the swimmer's group (37%). The facet joints and posterior elements were, however, clearly seen in 37 (70%) of the supine oblique patients compared with 22 (37%) of the swimmer's group (p < 0.001, chi2 test). Exposure dose calculations showed a substantial reduction for a pair of supine oblique views (1.6 mGy) over a single swimmer's view (7.2 mGy). CONCLUSIONS: In injured patients for whom the standard three view series fails to demonstrate the cervicothoracic junction, swimmer's views and supine oblique views show the alignment of the vertebral bodies with equal frequency. However, supine oblique films are safer, expose patients to less radiation, and are more often successful in demonstrating the posterior elements.

Cervical Vertebrae↗
PubMed1993

Faster O2 uptake kinetics at onset of supine exercise with than without lower body negative pressure.

The kinetics of oxygen uptake (VO2) were observed at the onset of submaximal cycling exercise in seven men and one woman [mean age 22.6 +/- 0.9 (SE) yr] in the upright and supine positions and the supine position with -40 mmHg lower body negative pressure (LBNP). There was no significant difference for peak VO2 and ventilatory threshold between the supine (3,081 +/- 133 and 1,954 +/- 138 ml/min, respectively) and the supine + LBNP positions (3,062 +/- 152 and 1,973 +/- 122 ml/min); however, both were reduced compared with upright exercise (3,483 +/- 200 and 2,353 +/- 125 ml/min). Kinetic analysis applied to six repetitions by each subject indicated a slowing from a mean total lag time (time required to achieve 63% of the difference in VO2 between baseline and new steady state) of 36.3 +/- 2.7 s in upright exercise to 44.1 +/- 3.5 s in the supine position. However, total lag time for the supine + LBNP position (36.0 +/- 2.8 s) did not differ from upright exercise but was significantly faster than supine exercise. These data have been interpreted in support of an O2 transport limitation to VO2 kinetics at the onset of supine exercise that is countered by LBNP, likely through a more rapid increase in perfusion to the exercising muscle at these submaximal work rates.

Adult↗
PubMed2006

Mechanical response to methacholine and deep inspiration in supine men.

The effects of supine posture on airway responses to inhaled methacholine and deep inspiration (DI) were studied in seven male volunteers. On a control day, subjects were in a seated position during both methacholine inhalation and lung function measurements. On a second occasion, the whole procedure was repeated with the subjects lying supine for the entire duration of the study. On a third occasion, methacholine was inhaled from the seated position and measurements were taken in a supine position. Finally, on a fourth occasion, methacholine was inhaled from the supine position and measurements were taken in the seated position. Going from sitting to supine position, the functional residual capacity decreased by approximately 1 liter in all subjects. When lung function measurements (pulmonary resistance, dynamic elastance, residual volume, and maximal flows) were taken in supine position, the response to methacholine was greater than at control, and this was associated with a greater dyspnea and a faster recovery of dynamic elastance after DI. By contrast, when methacholine was inhaled in supine position but measurements were taken in sitting position, the response to methacholine was similar to control day. These findings document the potential of the decrease in the operational lung volumes in eliciting or sustaining airflow obstruction in nocturnal asthma. It is speculated that the exaggerated response to methacholine in the supine posture may variably contribute to airway smooth muscle adaptation to short length, airway wall edema, and faster airway renarrowing after a large inflation.

Adult↗
PubMed2004

Distributions of lung ventilation and perfusion in prone and supine humans exposed to hypergravity.

When normal subjects are exposed to hypergravity [5 times normal gravity (5 G)] there is an impaired arterial oxygenation that is less severe in the prone compared with supine posture. We hypothesized that under these conditions the heterogeneities of ventilation and/or perfusion distributions would be less prominent when subjects were prone compared with supine. Expirograms from a combined rebreathing-single breath washout maneuver (Rohdin M, Sundblad P, and Linnarsson D. J Appl Physiol 96: 1470-1477, 2004) were analyzed for vital capacity (VC), phase III slope, and phase IV amplitude, to analyze heterogeneities in ventilation (Ar) and perfusion [CO(2)-to-Ar ratio (CO(2)/Ar)] distribution, respectively. During hypergravity, VC decreased more in the supine than in the prone position (ANOVA, P = 0.02). Phase III slope was more positive for Ar (P = 0.003) and more negative for CO(2)/Ar (P = 0.007) in the supine compared with prone posture at 5 G, in agreement with the notion of a more severe hypergravity-induced ventilation-perfusion mismatch in supine posture. Phase IV amplitude became lower in the supine than in the prone posture for both Ar (P = 0.02) and CO(2)/Ar (P = 0.004) during hypergravity as a result of the more reduced VC in the supine posture. We speculate that results of VC and phase IV amplitude are due to the differences in heart-lung interaction and diaphragm position between postures: a stable position of the heart and diaphragm in prone hypergravity, in contrast to supine in which the weight of the heart and a cephalad shift of the diaphragm compress lung tissue.

Adult↗
PubMed2004

Non-apneic snoring and the orthodontist: radiographic pharyngeal dimension changes with supine posture and mandibular protrusion.

OBJECTIVE: To evaluate the radiographic changes that occur in the pharynx and surrounding structures with alteration of posture from the upright to the supine position and the effect that mandibular protrusion whilst supine has on these dimensions. DESIGN: Prospective cephalometric study. SETTING: University Dental Hospital and School. SUBJECTS AND METHOD: This prospective study involved 35 consecutively referred adults with proven non-apneic snoring. Lateral skull radiographs were obtained with the subjects upright in occlusion, supine in occlusion and supine with the mandible protruded to the maximum comfortable position. Radiographs were traced and digitized, and the pharyngeal dimensional changes and hyoid position were examined. Males and females were examined separately. RESULTS: Radiographic pharyngeal dimensions were changed with altered posture, resulting in significant reductions in the minimum post-palatal (p<0.01) and post-lingual (p<0.05) airway measurements in the supine position. Mandibular protrusion whilst in the supine position produced increases in the functioning space for the tongue. CONCLUSION: A supine posture results in significant reductions in pharyngeal airway measurements of non-apneic snorers. Mandibular protrusion whilst in the supine position produces an increase in the functioning space for the tongue.

Adult↗
PubMed2007

Is supine rest necessary before blood sampling for plasma metanephrines?

BACKGROUND: The impact of blood sampling in sitting vs supine positions on measurements of plasma metanephrines for diagnosis of pheochromocytoma is unknown. METHODS: We compared plasma concentrations of free metanephrines in samples from patients with primary hypertension obtained after supine rest with those obtained in the sitting position without preceding rest. We also assessed the effects on diagnostic test performance retrospectively in patients with and without pheochromocytoma, and we calculated cost-effectiveness for pheochromocytoma testing. RESULTS: Upper reference limits of plasma free metanephrines were higher in samples obtained from seated patients without preceding rest than from supine patients with preceding rest. Application of these higher upper reference limits to samples from supine patients with pheochromocytoma decreased the diagnostic sensitivity from 99% to 96%. In patients without pheochromocytoma, adjusting the plasma concentration for the effects of sitting while preserving the 99% sensitivity by use of the supine upper reference limits increased the number of false-positive test results from 9% to 25%. CONCLUSIONS: To preserve high diagnostic sensitivity we recommend the use of upper reference limits determined from blood samples collected in the supine position. Under these conditions, negative test results for blood samples obtained with patients sitting are as effective for ruling out pheochromocytoma as negative results from samples obtained after supine rest. Repeat testing with samples obtained in the supine position offers a cost-effective approach for dealing with the increased numbers of false-positive results expected after initial sampling in the sitting position.

Adrenal Gland Neoplasms↗
PubMed1992

Hemodynamic responses to seated and supine lower body negative pressure: comparison with +Gz acceleration.

Hemodynamic changes between upright and supine lower body negative pressure (LBNP) to levels of -70 mm Hg were compared in 8 subjects (5 males, 3 females) and correlated with their findings during simulated Shuttle reentry acceleration with a slow onset rate of 0.002 G/s (1,020 s to peak +2 Gz) and during gradual onset exposures (0.03 G/s) to +3 Gz and +4 Gz. Six of the 8 subjects were able to tolerate 2 min at peak +2 Gz, 2-5 min at +3 Gz, and 1-2 min at +4 Gz. Heart rate (HR) at any given level of upright LBNP regularly exceeded supine levels. HR change at -50 mm Hg in upright subjects (+47.7 bpm from 74.1 +/- 1.9 (M +/- S.E.) bpm, control) was 2.6 times greater than in supine subjects (+18.3 bpm from 64.8 +/- 2.8 bpm, control). HR values at -40 mm Hg supine (73.7 +/- 2.6) matched seated upright pre-LBNP control levels (74.1 +/- 1.9 bpm), while values at -70 mm Hg supine (102.5 +/- 4.4 bpm) were not significantly different from those at -40 mm Hg upright (103.1 +/- 4.0 bpm). Peak HR during +3 Gz (145.8 +/- 7.7 bpm) and +4 Gz (152.3 +/- 6.5 bpm) significantly exceeded recorded supine and upright LBNP levels, whereas values at +2 Gz (104.8 +/- 5.5 bpm) closely matched those at -40 mm Hg upright (103.1 +/- 4.0 bpm) and -70 mm Hg supine (102.5 +/- 4.4 bpm). Supine LBNP HR changes in this relatively small group of subjects closely matched those previously reported in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2004

[Pro- and supination impairments due to torsional deformities of the radial diaphysis before and after ulna osteotomy].

The aim of this experimental study was to measure the exact influence of torsional deformities at the middle third of the radial shaft before and after osteotomy of the ulnar shaft on the rotation of the forearm. Intact and fresh cadaver specimens were fixed in a newly developed apparatus that allowed free pronation and supination. A ring fixator was applied to the radial shaft with K wires that allowed torsional deformities to be stabilized in steps of 10 degrees. The middle of the radial shaft was osteotomized via a small soft tissue window leaving the other soft tissues including the interosseous membrane intact. Supination and pronation were measured using a goniometer in a standardized fashion. The mean supination value before osteotomy of the radius was 71.6 degrees [standard deviation (SD)15.2 degrees], the mean pronation value was 64.5 degrees (SD 12.4 degrees). Radial osteotomy caused no significant difference in the range of motion prior to creation of torsional deformities. Supination torsional deformities greater than 30 degrees showed a significant loss of pronation and pronation torsional deformities greater than 30 degrees resulted in a significant loss of supination in 14 fresh cadavers, respectively. The amount of mean rotational loss was approximately the same in the respective pronation and supination torsional deformities. In the next step the influence of an ulna osteotomy on the range of motion was evaluated in different torsional deformities. In the four cadavers measured, there was an increase of the range of motion in the direction of the torsional deformity. These values were not significant when compared to values before ulna osteotomy, but there were significant changes to the non deformity (p=0.004 for pronation, p=0.003 for supination). Impairment of range of motion in the opposite direction of the deformity showed a similar appearance as values before ulna osteotomy. Again, there were significant changes to the non deformity (p=0.003 for pronation, p=0.005 for supination).

Adult↗
PubMed1981

Comparison of upright and supine bicycle exercise in the detection and evaluation of extent of coronary artery disease by equilibrium radionuclide ventriculography.

Upright and supine multiple gated cardiac blood pool scintigraphy was performed at rest and during maximum exercise in 37 patients, 15 with normal coronary arteriograms, 12 with coronary artery disease (CAD) without myocardial infarction (MI), and 10 with CAD and previous MI. Heart rate and systolic blood pressure were similar during upright and supine exercise in normal patients, but were significantly lower during supine exercise in both CAD groups. Left ventricular (LV) ejection fraction (EF), right ventricular (RV) EF, and LV segmental wall motion were similar in the upright and supine positions at rest or during maximum exercise within each group and showed high concordance of exercise responses. Although LV end-diastolic volume increased in all three groups during upright exercise and in both CAD groups when exercised supine, it did not change during supine exercise in patients without CAD. The fall of LV end-systolic volume in normals was greater during supine exercise than during upright exercise. LV end-systolic volume rose in the CAD patients in both positions. Therefore, although LVEF, RVEF, and LV segmental wall motion responses are similar in the upright and supine positions, LV end-systolic and LV end-diastolic volume changes are not. For detecting and evaluating CAD, the two different positions of exercise appear to have similar diagnostic content.

Coronary Circulation↗
PubMed1985

Doppler echocardiographic measurement of flow velocity in the ascending aorta during supine and upright exercise.

Doppler echocardiography was used to measure stroke volume, peak flow velocity, and acceleration of flow in the ascending aorta in 10 healthy young volunteers during unlimited supine bicycle exercise and upright treadmill exercise. High quality studies were obtained in all subjects through the suprasternal notch acoustic window; there was no appreciable degradation in Doppler signal caused by interference by increased respiration or chest wall motion. Stroke volume index increased from 54 ml/m2 at rest to 63.5 ml/m2 at peak supine exercise and from 38 ml/m2 standing at rest to 63.3 ml/m2 during peak upright exercise. Mean peak flow velocity rose from 0.91 m/s at supine rest to 1.36 m/s during maximum supine exercise. In the upright position mean peak flow velocity increased from 0.75 m/s at rest to 1.39 m/s during maximum exercise. Mean peak velocities were lower in the upright position at rest but were not significantly different at peak exercise. Mean acceleration of flow in the ascending aorta increased from 12.02 m/s2 during supine rest to 21.6 m/s2 during supine exercise and from 10.8 m/s2 at rest on the treadmill to 21.9 m/s2 during peak upright exercise. This study shows that echocardiographic measurement of ascending aortic blood flow by the Doppler technique is feasible even during vigorous exercise; that stroke volume and peak flow velocity at rest are lower in the upright position than in the supine position but equalise at peak exercise; and that acceleration of flow in the ascending aorta is the same in both the supine and upright positions and increases equally at peak exercise in both positions.

Adult↗
PubMed1986

Effects of supine and lateral positions on cardiac output and intracardiac pressures: an experimental study.

Hemodynamic measurements in human subjects and in experimental animals are generally made in the supine position; not much attention is paid to potential beneficial or harmful effects of right or left lateral positions on cardiac output or other hemodynamic variables. To evaluate the potential influence of such positional changes on cardiac performance, we measured cardiac output and left and right ventricular pressures (with micromanometer catheters) in anesthetized experimental animals (eight dogs and nine pigs) in the supine, right lateral, and left lateral positions. Cardiac output increased from supine to left lateral (mean +/- SD, 2.6 +/- 0.9 to 3.1 +/- 1.0 liters/min; p less than .001) and from supine to right lateral positions (2.6 +/- 0.9 to 3.1 +/- 1.1 liters/min; p less than .001). There was an associated decrease in arteriovenous oxygen saturation difference from supine to left lateral position (31 +/- 8% to 24 +/- 4%; p less than .001) and from supine to right lateral position (32 +/- 9% to 25 +/- 6%; p less than .001). Left ventricular systolic and end-diastolic pressures increased from supine to left lateral (128 +/- 17/9 +/- 2 to 147 +/- 19/16 +/- 4 mm Hg; both p less than .001) and from supine to right lateral positions (128 +/- 19/9 +/- 2 to 141 +/- 16/16 +/- 7 mm Hg; p less than .01 and p less than .001, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The hemodynamic and metabolic basis for decreased aerobic capacity in the supine exercise compared with the upright exercise in coronary artery disease.

To elucidate the mechanism of reduced exercise tolerance in the supine position, 14 patients with coronary artery disease were studied by both supine ergometer exercise and upright treadmill exercise. Maximal oxygen consumption in the supine position amounted to 80% of that in the upright position (1110 +/- 453 vs 1387 +/- 470 ml/min; p less than 0.001). Maximal cardiac output was identical in both positions (12.07 +/- 4.44 vs 12.55 +/- 4.49 l/min; ns). Maximal arteriovenous oxygen difference in the supine position amounted to 83% of that in the upright position (9.22 +/- 1.92 vs 11.14 +/- 1.88 vol%; p less than 0.01). Thus, the lower maximal oxygen consumption in the supine position was not caused by the decreased cardiac output but by the impaired augmentation of arteriovenous oxygen difference. Lactate concentration at the same oxygen consumption was higher in the supine position, which means early augmentation of anaerobic metabolism. We concluded that the aerobic capacity in the supine position was significantly lower than that in the upright position in patients with coronary artery disease, and the impaired utilization of transported oxygen was considered to be one of the mechanisms of the decreased aerobic capacity in the supine position.

Adult↗
PubMed1984

Recognition of pleural effusion on supine radiographs: how much fluid is required?

A prospective analysis of supine radiographs in 40 patients with pleural effusions was undertaken to determine the radiographic manifestations of pleural effusion on supine radiographs and the quantity of fluid that may be detected in the supine position. The presence of pleural effusion was predicted from supine radiographs using the following signs: increased homogeneous density superimposed over the lung fields, obliteration of the silhouette of the diaphragm, meniscus sign, apical capping, and accentuation of the right minor fissure. The supine radiographic findings were correlated with findings on subsequent standing erect posteroanterior and lateral radiographs. This study indicates that effusion of sufficient quantity to produce blunting of the lateral costophrenic angle on an erect posteroanterior radiograph (175-525 ml) will produce a noticeable increase in the density of the lower lung zone on supine radiographs. As the quantity of effusion increases, the abnormality of the supine chest radiograph increases in a stepwise manner. The classical findings of increased density over the entire hemithorax and apical capping described in pleural effusion on supine radiographs are late findings seen typically in large effusions.

Diaphragm↗