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PubMed1980

Halothane anesthesia and respiratory mechanics in dogs lying supine.

Functional residual capacity (FRC) and quasi-static deflation pressure-volume (PV) curves of the total respiratory system, lung, and chest wall were measured in eight trained dogs lying supine, first awake and then anesthetized with halothane. Two of the eight dogs were repetitively examined 10 times during a 15-mo period. FRC decreased with anesthesia in six of the eight dogs and incresed with anesthesia in the remaining two dogs. There was a significant mean anesthesia-induced reduction in FRC of 16.9% (P < 0.05). FRC change with anesthesia varied between studies in one of the two dogs repetitively examined. Mean PV curves of the total system, lung, and chest wall of the six dogs whose FRC decreased with anesthesia were shifted to the right by anesthesia. PV curves from the two dogs whose FRC increased with anesthesia were shifted to the left. Anesthesia produced a significant reduction (P < 0.05) in mean lung compliance and significant increases (P < 0.05) in mean chest wall and total system compliances.

Anesthesia, Inhalation↗
PubMed1981

Hypoxia effects on plasma volume shifts at rest, work, and recovery in supine posture.

The purpose of this study was to determine the effects acute exposure to hypoxia (less than 1.5 h; gas mixture 12.6% O2-87.4% N2) has on plasma volume (PV) shifts during rest and exercise. Nine unacclimatized males performed identical protocols in the supine posture in both normoxic (N) and hypoxic (H) conditions. The protocol was rest 60 min, submaximal exercise (PWC 140, work rate eliciting a heart rate of 140 beats/min) for 30 min, immediately followed by maximal exercise, and 10 min of passive recovery. There were slight but significant losses of 2.7 and 1.4% PV at rest in H and N conditions, respectively. At the same relative intensity of submaximal exercise (work loads reduced by 22% in H conditions), PV losses were nearly identical (N = 11.2%, H = 11.8%). There was a further PV efflux subsequent to maximal exercise (N = 7.9%, H = 5.2%). The maximum PV efflux, from the beginning of rest to the end of maximal exercise, was 20% for both conditions. Total plasma protein (PP) content was unchanged during rest or exercise for either N or H conditions. After 10 min of recovery, restitution of PV was 10% below preexercise values for both N and H conditions. We conclude that acute hypoxic exposure does not influence the loss of VP or PP during submaximal or maximal exercise.

Adult↗
PubMed1982

Respiratory mechanics in supine subjects during progressive partial curarization.

Respiratory mechanics were studied in six supine conscious volunteers during progressive muscle weakness produced by infusion of d-tubocurarine. Partial curarization was carried out to the point of abolishing head lift ability and handgrip strength. At all levels of partial paralysis, expiratory muscle strength was significantly more impaired than inspiratory strength. Despite this, subjects maintained relatively normal maximal expiratory flow rates, whereas inspiratory flows decreased significantly. The diminished inspiratory flows are not fully explained by decreased driving pressures during force inspiration, since inspiratory resistance increased significantly with the decreased flow. Inspiratory flow patterns suggest a variable extrathoracic obstruction most likely due to the absence of normal airway abductor activity during inspiration. Maximal respiratory muscle weakness decreased forced vital capacity by 29% and total lung capacity by 15%. The decreased level of lung inflation did not alter lung elastic recoil. Functional residual capacity was unchanged, but inspiratory capacity decreased by 25% and residual volume increased by 38%. These changes are in accord with predictions based on the decreased muscle strength and normal respiratory system recoil.

Adult↗
PubMed1985

Mechanical output following muscle stretch in forearm supination against inertial loads.

Muscle stretch enhances force produced in both single fibers and voluntarily activated human muscle. This study determined how initial conditions of muscle stretch (and associated eccentric work), muscle length, and load inertia contributed to human concentric muscular output during maximal voluntary forearm supination. Outputs of angular velocity and concentric work over specific displacements and times of motion were calculated. Multiple regression analysis was performed using these outputs and initial conditions as dependent and independent variables, respectively. Initial conditions were shown to be significant and systematic determinants of muscle output in concentric contraction. Evidence of a temporary shift in the force-velocity curve was found and discussed regarding its beneficial contribution to load movement. Greater benefit was considered to be due to the fact that muscle stretch allows time for achievement of maximal muscular recruitment prior to concentric contraction. This produces large forces at the onset of the concentric phase, in comparison with contractions starting from rest. These findings were discussed with regard to both single- and multi-segment movement patterns.

Biomechanical Phenomena↗
PubMed1986

Respiratory function of intercostal muscles in supine dog: an electromyographic study.

It is traditionally considered that the difference in orientation of the muscle fibers makes the external intercostals elevate the ribs and the internal interosseous intercostals lower the ribs during breathing. This traditional view, however, has recently been challenged by the observation that the external and internal interosseous intercostals, when contracting alone in a single interspace, have a similar effect on the ribs into which they insert. This view has also been challenged by the observation that the external and internal intercostals in a given interspace often change their length in the same direction during breathing. In an attempt to clarify the respiratory function of these muscles, we studied eight supine lightly anesthetized dogs during quiet breathing and during static inspiratory efforts. In each animal electromyographic (EMG) recordings from the external and internal interosseous intercostals were obtained in all interspaces from the second to the eighth, and selective denervations were systematically performed to ensure with complete certainty the origin of the recorded EMG activities. The external intercostals were only activated in phase with inspiration, whereas the internal interosseous intercostals were only activated in phase with expiration. These phasic EMG activities, however, were generally small in magnitude, and the muscles were often silent. Indeed, activation of the externals was always confined to the upper portion of the rib cage, whereas activation of the internals was limited to the lower portion of the rib cage. Internal intercostal activation always occurred sequentially along a caudocephalic gradient. These observations are thus compatible with the traditional view of intercostal muscle action.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Pressure-diameter relationships of the upper airway in awake supine subjects.

In awake supine normal subjects, dimensional changes of the oropharyngeal airway were measured during exposure to negative intraluminal pressures. The pressure was generated 1) "actively" by subjects inspiring against an externally occluded airway or 2) "passively" by external suction at the mouth during voluntary glottic closure with no inspiratory effort. Airway dimensions were imaged with X-ray fluoroscopy and anteroposterior diameters measured at levels corresponding to cervical vertebra 3 and 4 (C3 and C4). Cephalad axial displacement of the hyoid bone (CDHY) was also measured. During the "active" maneuver, airway diameters and position were maintained at resting levels despite airway pressure up to -15 cmH2O. In contrast, during the passive maneuver at -15 cmH2O, C3 was only 15 +/- 9% and C4 only 47 +/- 8% of control; CDHY was 5.6 +/- 1.8 mm. In three subjects airway wall apposition occurred and persisted until an active inspiratory effort. We conclude that, in the absence of inspiratory effort, negative oropharyngeal airway pressures result in marked narrowing and cephalad displacement of the upper airway, even during wakefulness. Therefore, our data suggest that the complex interaction of upper airway and thoracic muscle activity is critical in determining the effective compliance and patency of the upper airway, which is readily collapsible even in normal subjects.

Adult↗
PubMed1988

A polygraphic study of systolic time intervals and their correlations with heart rate and workload during supine ergometry in one hundred normal subjects.

The present study was designed to investigate systolic time intervals (STI) in 100 normal subjects undergoing continuous-maximal supine cycle ergometry and to search for possible linear correlations between STI (dependent variables) and heart rate, diastolic blood pressure, systolic blood pressure, age, sex, weight, and height (independent variables), by stepwise regression analysis. The only significant correlation discovered in the study was between the contractility index (isometric contraction time-ICT) and the total work produced by each participant. Exercise tolerance was limited primarily by shortening of the ICT interval, all subjects discontinuing the test when ICT reached 13.7 +/- 7 ms.

Adult↗
PubMed1980

Evaluation of the supine pressor test.

115 normotensive healthy primigravidae have been investigated during 28-32 weeks of pregnancy for early detection of pregnancy-induced hypertension (PIH) by performing the roll-over test (ROT) of according to Gant et al. No statistically significant relation was found between a positive supine pressor test and development of PIH. The hydrostatic effect, calculated in 15 of these women, seems to influence the results of the ROT. The other factors which can influence the blood pressure with change of position have also been enumerated.

Blood Pressure Determination↗
PubMed1977

Sequential evaluation of the supine hypertension or 'roll-over' test in a high risk population.

The supine hypertensive or 'roll-over' test (ROT) was performed serially in 24 primigravid patients between 27 and 35 weeks of gestational age. Pregnancy-induced hypertension (PIH) developed in 3 women (12.5%). Test producibility one week to the next in the same patient was poor. A false-positive ROT was noted for 83% of our patients a false-negative test for 12.5%. We conclude that serial testing reveals marked variations in response that reflect inherent biologic fluctuations that limit the predictive value of the ROT for screening outpatients.

Adolescent↗
PubMed1977

Left precordial isopotential mapping during supine exercise.

Junctional depression is often observed during physical exercise in overtly normal subjects. To explore its pathogenesis, 15 normal volunteers were studied during supine, bicycle ergometer, submaximal stress tests. Electrocardiograms were simultaneously recorded from 42 electrodes on the left anterior precordium at two minute intervals at rest and during exercise. Data were used to construct isopotential maps throughout the P-QRS-T intervals. At rest, maps throughout the ST segment were dominated by a single maximum along the upper left sternal border. During exercise, all subjects developed junctional depression that was maximal along the lower left sternal border. Exercise maps during the early to mid-ST segment showed an intense minimum along the lower left sternal border that was continuous with terminal QRS forces in both intensity and location. Later in ST, this minimum decreased in strength and was replaced by a maximum located in the same area as that observed at rest. These observations suggest that junctional depression is the result of competition between two effects, one being normal repolarization which is obscured in the early ST segment by the second, possibly representing delayed terminal depolarization forces.

Action Potentials↗
PubMed1982

Assessment of right ventricular function during supine bicycle exercise after Mustard's operation.

Right ventricular (RV) performance during supine bicycle exercise was evaluated by gated equilibrium nuclear angiography in 19 clinically well children with d-transposition of the great arteries (d-TGA), 6.4 +/- 2.7 years after Mustard's operation. Comparisons were made between rest and peak exercise. The mean resting ejection fraction was 44 +/- 12% (range 30-75%) and was unchanged at peak exercise. Eight children had a normal ejection fraction response, whereas 11 children had either no increase or a decrease in ejection fraction. Relative end-diastolic volumes decreased from resting values in all patients who had an abnormal ejection fraction response. Among patients whose ejection fraction increased, the end-diastolic volume increased in three, decreased in four and was unchanged in one at peak exercise. Heart rate increased 84% (range 52-135%) and systolic blood pressure increased 16% (range 0-28%) at peak exercise. There was no correlation between exercise response and age at surgery or interval since surgery. These data indicate that clinically well children after Mustard's procedure may have abnormal right ventricular function under stress, raising concerns about the ability of the right ventricle to function as the systemic ventricle.

Adolescent↗
PubMed1985

Hemodynamic findings at rest and during mild supine exercise in adults with isolated, uncomplicated ventricular septal defects.

Fifty-two patients with isolated congenital ventricular septal defects (VSDs), studied for the first time at age 10 or older, were restudied an average of 16 years later (range 4 to 21). The study protocol included a symptom-limited bicycle ergometer test, M mode echocardiographic examination, and hemodynamic studies at rest and during mild supine exercise. Of the 52, 17 had been operated on an average of 19 years earlier (range 11 to 21) (group 1) and 35 with smaller defects were not operated on (group 2). Although more pronounced findings were made in group 1, a similar pattern was observed in group 2: In most subjects in both groups a subnormal working capacity was observed. A subnormal left ventricular fractional shortening and circumferential shortening velocity was noted in a high proportion at echocardiography. A number of hemodynamic aberrations were observed in a high proportion of patients during exercise but not at rest. Thus a subnormal increase in left and right ventricular cardiac output was found in addition to pathologic increase in right and left ventricular end-diastolic, pulmonary arterial, and pulmonary capillary wedge pressures. In group 1, elevated pulmonary arterial pressures before operation and/or small residual VSDs were associated with a poor hemodynamic outcome. In neither group could significant correlations be observed between hemodynamic aberrations, shunt size, and/or age. Among patients who underwent surgery, the earlier surgical trauma might have contributed to the functional aberrations, but in group 2 the only likely explanation for the findings seems to be the VSD itself. Possibly a long-standing VSD--found unnecessary to repair according to commonly accepted criteria--may lead to disturbed systolic function and increase in compliance of both ventricles via a chronic pressure and volume overload.

Adult↗
PubMed1988

Norepinephrine spillover to plasma during steady-state supine bicycle exercise. Comparison of patients with congestive heart failure and normal subjects.

This study was performed to determine the relative contributions of plasma norepinephrine clearance and norepinephrine release to the increase in plasma norepinephrine concentration that occurs during exercise and to determine whether the high rates of cardiac norepinephrine release from the heart and kidney in patients with heart failure are associated with diminished reserve for regional sympathetic nervous stimulation. During supine steady-state bicycle exercise at 50% of maximum voluntary exercise capacity, the plasma norepinephrine concentration of six patients with congestive heart failure rose from 385 +/- 88 to 2,200 +/- 497 pg/ml, whereas that of nine normal subjects rose from 208 +/- 21 to 882 +/- 257 pg/ml. The change in plasma concentration in both groups was due to an increase in norepinephrine spillover to plasma without a change in plasma norepinephrine clearance. In patients with heart failure, cardiac spillover increased from 80 +/- 26 to 528 +/- 265 ng/min during exercise, and renal spillover rose from 146 +/- 71 to 418 +/- 69 ng/min. In the normal subjects, cardiac spillover rose from 5 +/- 2 to 73 +/- 23 ng/min, and renal spillover increased from 76 +/- 27 to 275 +/- 106 ng/min. There is no evidence of a reduced reserve for overall or regional sympathetic stimulation in patients with heart failure. Reduced reflex responses in these patients are more likely due to end-organ refractoriness than to inadequate stimulation.

Bicycling↗
PubMed1981

A radiographic method for measuring steady-state functional residual capacity in the supine patient. A method suitable for sleep studies.

We have devised a method to measure functional residual capacity (FRC) in the recumbent, spontaneously breathing patient. Simultaneous anteroposterior and lateral chest radiographs were exposed at the end of an exhalation, as determined by tracings of flow sensed by a nasal thermistor. The volume of the lungs was then planimetrically measured. Functional residual capacity was sequentially measured in 20 supine subjects, both by a helium dilution technique and by the radiographic technique. Planimetric measurement of FRC correlated well with the helium dilution technique, with a range of FRC measurements from 1.53 to 6.41 L (r = 0.94). This method of measuring lung volume should be useful in evaluating changes in FRC associated with different sleep stages and in explaining the mechanisms causing nocturnal oxygen desaturation in patients with chronic obstructive lung disease.

Functional Residual Capacity↗
PubMed1987

Functional residual capacity in healthy preschool children lying supine.

Functional residual capacity (FRC) was measured by the closed-circuit helium dilution method in 41 supine healthy children 1 month to 8 yr of age. In 20 children, the measurement was carried out while they were awake, and in the others, who were less cooperative, testing was done during ketamine anesthesia before elective surgery. There was no significant difference in the FRC values between these groups, and they were subsequently analyzed as a single group. For males and females separately and combined, FRC correlated significantly with height, age, and weight, both with linear and nonlinear regression analyses. No significant difference between the sexes was found. The best correlation of FRC was with height; the linear equation being FRC (ml) = -457.3 + 8.8 X height (cm) (r2 = 0.662), and the nonlinear equation being FRC (ml) = 0.0052 X [height (cm)]2.44 (r2 = 0.827).

Child↗
PubMed1987

Supination-eversion fractures of the ankle joint: changes in incidence over 30 years.

The sex- and age-specific incidence has been calculated for ankle fractures from the first part of the 1950s and compared with the 1980s, a 30-year interval. The fractures were also classified according to Lauge-Hansen. Altogether 1784 fractures were found. During that time interval ankle fractures had become more common, particularly those with extensive skeletal involvement, such as the stage IV supination-eversion fractures, which today have an incidence pattern more typical of a fragility fracture in elderly women.

Adult↗
PubMed1994

Effect of pronation and supination orthosis on Morton's neuroma and lower extremity function.

Twenty-three adult patients with Morton's neuroma of one foot were randomized to receive in-shoe orthoses made from a hard, compressed, felt material that would either pronate or supinate both feet. The response of the neuroma pain was measured using subjective visual analogue scales, an objective examination, and the MACTAR patient-specific measure of maximal function. The development of any other lower limb symptoms was also recorded. The pain associated with Morton's neuroma was not significantly altered by changing the position of the foot with the compressed felt orthosis. Forcibly pronating the foot did not produce a significant incidence of lower limb symptoms in the short term.

Adult↗
PubMedDate not supplied

Supine hypotensive syndrome caused by intra-abdominal mass: a case report.

An obese woman who presented with 3 separate intra-abdominal masses developed a supine hypotensive syndrome following induction of general anesthesia. The hypotension was corrected by positioning the patient in a left lateral tilt and by releasing intra-abdominal pressure. Following decompression of the vena cava, arterial and central venous pressure rose and remained at a high level. Urine output was poor until IV furosemide was administered.

Adult↗