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A prospective, randomised controlled trial comparing the efficacy of pre-oxygenation in the 20 degrees head-up vs supine position.

We investigated whether positioning patients undergoing general anaesthesia for cholecystectomy in a 20 degrees head-up position, as opposed to supine, improved the efficacy of 3 min of standard pre-oxygenation via a circle breathing system. Following pre-oxygenation, patients received a standard induction of anaesthesia and the apnoea time (from administration of rocuronium to the arterial oxygen saturation to fall to 95%) was recorded. Mean (95% CI) apnoea time was 386 (343-429) s in the 20 degrees head-up position (n = 17) vs 283 (243-322) s in the supine position (n = 18; p = 0.002). Pre-oxygenation is significantly more efficacious and by inference more efficient in the 20 degrees head-up position than in the supine position.

Adult↗

Comparison of umbilical artery Doppler velocimetry between maternal supine position and complete left lateral position in predicting obstetric complications.

The aim of this study was to compare the predictive value of umbilical artery Doppler velocimetry in women in the supine position with that in women in the complete left lateral position as a screening test for abnormal obstetric outcomes. Umbilical artery resistance index (RI) was measured at 27-29 weeks and 35-37 weeks in 202 pregnant women. The measurements were performed with the mother in the supine position in 100 cases (supine group), and in the complete left lateral position in 102 cases (lateral group). Predictive values of the tests for abnormal outcomes (small for gestational age, fetal distress, pregnancy-induced hypertension) were compared between both groups. When abnormal RIs were defined as being greater than the 90th centile in the supine group, the sensitivities for any of the abnormal outcomes at 27-29 weeks were 18% in the supine group and 6% in the lateral group; the positive predictive values were 30% and 25%, respectively. For measurement at 35-37 weeks, the sensitivity and positive predictive value were 29% and 45%, respectively in the supine group, and 0% in both cases in the lateral group. When abnormal RIs were defined as being greater than the 90th centile in the lateral group, the sensitivities at 27-29 weeks were 41% in the supine group and 6% in the lateral group; the positive predictive values were 44% and 8%, respectively. At 35-37 weeks, the sensitivity and positive predictive value were 53% and 43% in the supine group, and 6% and 8% in the lateral group. Umbilical artery Doppler velocimetry when the mother was in the complete left lateral position was of little value as a screening test. However, when the mother is in the supine position, it may serve as a kind of stress test and disclose latent obstetric abnormalities in certain cases.

Adult↗

Biomechanics of lower limb raising from the supine position.

AIM: This study analyses the kinematics of the lower limb raising movement from the supine position and the electromyography activity of the muscles involved. METHODS: Twenty healthy right hand subjects performed the right lower limb raising from the supine position, starting from the clinical bed plane and up to a 70 degrees inclination of the thigh over the horizontal plane, while the knee was kept flexed at 120 degrees by a soft splint. The same exercise was executed with no resistance and with 2 kg and 8 kg respectively applied to the ankle. The kinematics was recorded utilising an optoelectronic system, whereas the electromyography activity was recorded by a surface electromyography (EMG) applied to the following muscles: right rectus femoris, left biceps femoris, rectus abominalis from both sides and dorsal major from both sides. RESULTS: In all the cases the pelvis performed a backwards rotation retroversion. The highest increase of EMG activation was recorded on the right rectus femoris as well as on the left biceps femoris; the increase was lower in the right rectus abdominis and in the right dorsal major, whereas it was minimum in the left rectus abdominis and in the left dorsal major. A great variability in the activation times was reported in the various muscles of the different subjects, regardless of the trials. The only muscle anticipating the right rectus femoris activation was the left biceps femoris. CONCLUSIONS: The research has shown how the simple movement under study is more complex than what is usually described by the text books, both in regard to the kinematics and to muscles' actions. Even the individual variability in utilising the agonist and stabilisation muscles can be of relevance for a more rational utilisation of the physical exercise in motor re-education.

Adult↗

A cephalometric and electromyographic study of upper airway structures in the upright and supine positions.

Obstructive sleep apnea (OSA) is characterized by recurrent upper airway obstruction during sleep, usually in the supine position. To investigate the relationship between upper airway size and genioglossus (GG) muscle activity, upright and supine cephalograms were obtained in 20 OSA patients and 10 symptom-free control subjects. Tongue electromyographic (EMG) recordings were obtained with surface electrodes, and pressure transducers were placed in the 10 symptom-free controls. The tongue cross-sectional area increased 4.3% (p < 0.05), and the oropharyngeal area decreased 36.5% (p < 0.01) when the OSA patients changed their body position from upright to supine. No changes were observed in the tongue area, but soft palate thickness increased (p < 0.01) when the control subjects changed from the upright to the supine position. Furthermore, the oropharyngeal cross-sectional area decreased 28.8% (p < 0.01) despite a 34% increase (p < 0.05) in resting GG EMG activity. Posterior tongue pressure increased 17% (p < 0.05) with the change from upright to supine. On the basis of these findings, we propose that body posture has a substantial effect on upper airway structure and muscle activity. This postural effect should be taken into account when assessing upper airway size in the erect posture (conventional cephalography) and in the supine position (computed tomography). The vertical and anteroposterior position of the tongue and its relationship to airway size may be more important than soft palate size in the pathogenesis of OSA.

Airway Resistance↗

Avoiding the supine position during sleep lowers 24 h blood pressure in obstructive sleep apnea (OSA) patients.

Obstructive sleep apnea (OSA), is a common clinical condition affecting at least 2-4% of the adult population. Hypertension is found in about half of all OSA patients, and about one-third of all patients with essential hypertension have OSA. There is growing evidence that successful treatment of OSA can reduce systemic blood pressure (BP). Body position appears to have an important influence on the incidence and severity of these sleep-related breathing disturbances. We have investigated the effect of avoiding the supine position during sleep for a 1 month period on systemic BP in 13 OSA patients (six hypertensives and seven normotensives) who by polysomnography (PSG) were found to have their sleep-related breathing disturbances mainly in the supine position. BP monitoring was performed by 24-h ambulatory BP measurements before and after a 1 month intervention period. We used a simple, inexpensive method for avoiding the supine posture during sleep, namely the tennis ball technique. Of the 13 patients, all had a reduction in 24-h mean BP (MBP). The mean 24-h systolic/diastolic (SBP/DBP) fell by 6.4/2.9 mm Hg, the mean awake SBP/DBP fell by 6.6/3.3 mm Hg and the mean sleeping SBP/DBP fell by 6.5/2.7 mm Hg, respectively. All these reductions were significant (at least P < 0.05) except for the sleeping DBP. The magnitude of the fall in SBP was significantly greater in the hypertensive than in the normotensive group for the 24 h period and for the awake hours. In addition, a significant reduction in BP variability and load were found. Since the majority of OSA patients have supine-related breathing abnormalities, and since about a third of all hypertensive patients have OSA, avoiding the supine position during sleep, if confirmed by future studies, could become a new non-pharmacological form of treatment for many hypertensive patients.

Adult↗

The lithotomy versus the supine position for laparoscopic advanced surgeries: a historical review.

Laparoscopic advanced surgery has been taught in many institutions in the United States. Initially, proctoring for the laparoscopic technique was performed by European surgeons; therefore, the lithotomy position was suggested as the preferred approach. Many American and European surgeons have adopted the supine position. Laparoscopy initially entered the clinical realm in the field of gynecology. Albert Decker, at the Knickerbocker and Gouverneur Hospital in New York, performed culdoscopy as early as 1928. This was done in the "knee-chest" position without the use of pneumoperitoneum. Raoul Palmer, at the Hopital Broca in Paris, popularized "colposcopie," utilizing pneumoperitoneum, with the patient in the lithotomy position. Laparoscopy then advanced in Europe to the general surgery arena. As a result, patient positioning for laparoscopic procedures in Europe was performed in what is now referred to as the French position (i.e., lithotomy). Many of these procedures are modified to a side approach, or American position, when performed in the United States. There is a clear association between the dorsal lithotomy position and the development of postoperative compartment syndrome. Compartment syndrome occurs when elevated pressure in an osteofascial compartment compromises local perfusion, and often results in neurovascular damage and permanent disability. Many centers have adopted the lithotomy position for their laparoscopic advanced procedures. At our institution, however, we prefer all procedures be performed in the American position (patient supine and the surgeon at the side of the patient), since this resembles the position used for other, open surgeries. The advantage of this approach is that it eliminates the risks associated with placement of the patient in the lithotomy position.

Compartment Syndromes↗

A simple technique for craniospinal radiotherapy in the supine position.

PURPOSE: Craniospinal irradiation poses technical difficulties that may be addressed with the use of the newer technologies that have become available over the past decade. The use of CT simulation allows improved target localisation and beam geometry definition while significantly reducing the treatment simulation time. We have developed a CT-based technique for whole CNS irradiation in the supine position that uses fixed field parameters, asymmetric jaws for field matching and drastically reduces simulation and treatment times. METHODS: The patient is CT scanned and treated in the supine position. The clinical target volume and relevant critical structures are outlined on a planning CT scan. Half beam blocked lateral fields with a collimator rotation are used to match the beam divergence from the superior border of the spinal field at the C2 vertebral body. The shielding for the cranial fields is generated automatically, and the dose distribution is calculated using a 3D treatment planning system. Fixed field parameters are used for the planning and treatment. The position of the isocenter of the spine field is always a fixed longitudinal distance from the isocenter of the brain fields. If multiple posterior fields are required, the isocenter of the second spine field is always a fixed longitudinal distance from that of the first and the gap between the fields is determined using virtual simulation and feathered during treatment using the asymmetric jaws of the linear accelerator. All treatment portals are filmed daily during the first week of treatment, and after each junction change thereafter. RESULTS AND CONCLUSION: The supine position provides numerous advantages. Patients are more comfortable, the treatment position is more reproducible, and access to the airway is possible, if necessary, for patient sedation. The use of CT simulation decreases the simulation time, allows for increased planning accuracy, and enables the use of multimodality image registration, and 3D treatment planning. The use of asymmetric jaws allows for junction feathering without changing the patient setup or using a couch angle.

Axis, Cervical Vertebra↗

A comparison of triceps skinfold and upper arm circumference measurements taken in standard and supine positions.

Because hospitalized patients are often unable to assume the upright position recommended for anthropometric measurements, the effect of patient position on accuracy of triceps skinfold and arm circumference measurements was investigated. Three measurements of triceps skinfold and arm circumference were taken on the right arm of 74 patients by trained technicians with extensive experience in anthropometric evaluation using a Lange caliper and Inser-tape. Measurements were repeated in the supine position 5 hours later on the same day by the same observer. Mean triceps skinfold, arm circumference, and calculated arm muscle circumference values obtained in the upright position correlated highly with those obtained in the supine position. Differences were less than one measurement unit and not significant when compared using parametric (Student t-test) and non parametric (Wilcoxon Matched-Pairs Signed-Ranks Test) statistically analysis. This study indicates that triceps skinfold and arm circumference can be measured accurately, reproducibly, and comparably in the supine position when the patient is unable to assume the recommended upright stance.

Adult↗

Regional variations in lung expansion in rabbits: prone vs. supine positions.

We studied the vertical gradient in lung expansion in rabbits in the prone and supine body positions. Postmortem, we used videomicroscopy to measure the size of surface alveoli through transparent parietal pleural windows at dependent and nondependent sites separated in height by 2-3 cm at functional residual capacity (FRC). We compared the alveolar size measured in situ with that measured in the isolated lungs at different deflationary transpulmonary pressures to obtain transpulmonary pressure (pleural surface pressure) in situ. The vertical gradient in transpulmonary pressure averaged 0.48 +/- 0.16 (SD) cmH2O/cm height (n = 10) in the supine position and 0.022 +/- 0.014 (SD) cmH2O/cm (n = 5) in the prone position. In mechanically ventilated rabbits, we used the rib capsule technique to measure pleural liquid pressure at different heights of the chest in prone and supine positions. At FRC, the vertical gradient in pleural liquid pressure averaged 0.63 cmH2O/cm in the supine position and 0.091 cmH2O/cm in the prone position. The vertical gradients in pleural liquid pressure were all less than the hydrostatic value (1 cmH2O/cm), which indicates that pleural liquid is not generally in hydrostatic equilibrium. Both pleural surface pressure and pleural liquid pressure measurements show a greater vertical gradient in the supine than in the prone position. This suggests a close relationship between pleural surface pressure and pleural liquid pressure. Previous results in the dog and pony showed relatively high vertical gradients in the supine position and relatively small gradients in the prone position. This behavior is similar to the present results in rabbits. Thus the vertical gradient is independent of animal size and might be related to chest shape and weight of heart and abdominal contents.

Animals↗

Anatomical configuration of the spinal column in the supine position. I. A study using magnetic resonance imaging.

In order to clarify the anatomical configuration of the spinal column in the supine position, we have examined T1-weighted sagittal midline magnetic resonance images of the spinal column in 20 healthy volunteers (11 men, nine women) in the supine position. The mean maximum angles of decline of the lumbar spinal canal in men and women were 12.6 (SD 3.9) degrees and 13.4 (3.3) degrees in the cephalad direction, respectively. The maximum angles of incline of the upper thoracic spinal canal in men and women were 20.3 (4.0) degrees and 18.5 (2.5) degrees, respectively. The median highest points of the lumbar spinal canal in men and women were located at L4 (range L3-4 to L4) and L4 (L4), respectively. The lowest point of the thoracic spinal canal was located at T8 (T7-T9) in both men and women. We have demonstrated that both lumbar lordosis and thoracic kyphosis differ between individuals, particularly with respect to the lowest point of the thoracic spinal canal, which is located between T7 and T9.

Adolescent↗

Hip arthroscopy: the supine position.

Hip arthroscopy performed with the patient in the supine position is an effective, reproducible procedure. Advantages include ease and simplicity of patient positioning, use of a standard fracture table, operating room layout that is user friendly, familiar joint orientation, and optimal access for all portal placements. All technical aspects of performing the procedure are detailed, including necessary equipment, patient positioning, landmarks, portal placement, and arthroscopic anatomy. Effective and safe performance of this procedure is dependent on careful attention to every detail of the operation.

Arthroscopy↗

Correlation of motor control in the supine position and assistive device used for ambulation in chronic incomplete spinal cord-injured persons.

Neurocontrol of movement after spinal cord injury (SCI) is often spared, but few studies have investigated the chronic incomplete SCI patient. Multichannel surface electromyography (SEMG) can describe characteristics of neurocontrol during a series of volitional and reflex events. The relationship of these neurocontrol characteristics to clinical function is incompletely described. This study, retrospectively, evaluated the relationship between neurocontrol patterns evoked by lower limb movement in the supine position and the assistive device used for ambulation in chronic, incomplete SCI persons. The records of 15 neurologically healthy (9 male, 6 female) and 36 incomplete SCI persons (27 male, 9 female) (C2-T10) were used. SEMG was recorded from both quadriceps, adductors, hamstrings, anterior tibialis and triceps surae muscles and displayed on a stripchart for analysis. SEMG patterns of activity recorded in the supine position during volitional, unilateral, multijoint (hip and knee flexion and extension) movement attempts were characterized, divided into seven groups and compared with the subjects' self-selected ambulation device (independent, cane, crutches, walker or nonambulatory). The neurocontrol patterns recorded in the supine position correlated well with the SCI subjects ambulatory assistive device. Marked decreases in motor unit output and/or loss of motor organization were found in the nonambulatory group. Coactivation of proximal muscles, poor timing of muscle activity and radiation of activity into contralateral muscles were also noted in subjects who required a walker or crutches. To a lesser degree, abnormal motor patterns were also noted in subjects who ambulated with a cane or independently.

Adult↗

Assessment of visual acuity in the supine position.

OBJECTIVE: To determine whether a modified Snellen eye chart could be used to accurately assess visual acuity (VA) in the supine position. METHOD: This was a prospective study involving ED staff volunteers comparing VA on a standard Snellen eye chart with VA on a size-reduced ceiling-mounted modified Snellen eye chart. RESULTS: Fifty-six volunteers participated. VA ranged from 20/10 to 20/200 on both of the charts, but 87% of the volunteers had VA of 20/50 or better. The VA results for the 2 charts were highly correlated; right eye r = 0.931 and left eye r = 0.953. Weighted ks showed substantial agreement for both eyes; kappa = 0.63 and 0.79 for the right and left eyes, respectively. In only 4 of 112 paired measurements did the VA recorded with the ceiling chart differ by > 1 line from that recorded on the Snellen chart. CONCLUSION: There is an excellent correlation between VAs determined in the erect and the supine positions using the standard Snellen eye chart and the modified ceiling-mounted version. Substantial agreement exists between readings using the 2 charts. Although additional testing is warranted in an ophthalmologically diverse patient population, use of this chart for the assessment of VA in the supine ED patient may allow for earlier VA evaluation.

Adolescent↗

Effect of the supine position on uterine and umbilical blood flow during the third trimester of uncomplicated pregnancies in multiparous patients.

We established the effects of the supine position on umbilical blood flow when measured during the third trimester in 30 multiparous, normotensive patients. Blood flow in the umbilical and uterine arteries and blood pressure in the brachial and popliteal arteries were blindly taken by two different observers: first in the lateral and 5 min later in the supine position. There was a significant difference in mean blood pressure between the two postures. However, there was no statistical difference in the pulse pressure or in systolic/diastolic ratio in the umbilical and uterine arteries between the two positions. Postural changes in normotensive multiparous patients do not affect uterine and umbilical blood flow during the third trimester of uncomplicated pregnancies.

Adult↗

Effects of upright and supine position on cardiac rest and exercise response in aortic regurgitation.

The effects of upright and supine position on cardiac response to exercise were assessed by radionuclide ventriculography in 15 patients with moderate to severe aortic regurgitation (AR) and in 10 control subjects. In patients with AR, heart rate was higher during upright exercise, but systolic and diastolic blood pressure and left ventricular (LV) output were similar during both forms of exercise. LV stroke volume and end-diastolic volume were not altered during supine exercise. LV end-systolic volume increased and ejection fraction decreased during supine exercise, but both were unchanged during upright exercise. Of 15 patients, 5 in the upright and 12 in the supine position had an abnormal LV ejection fraction response to exercise (p less than 0.01). Right ventricular ejection fraction increased and regurgitant index decreased with both forms of exercise and was not significantly different between the 2 positions. Thus, posture is important in determining LV response to exercise in patients with moderate to severe AR.

Adult↗

Technique and complications of percutaneous nephroscopy: experience with 557 patients in the supine position.

PURPOSE: Percutaneous nephroscopy is usually performed with the patient prone, which is uncomfortable for the patient and does not prevent damage to the colon. We assess the possibility of performing percutaneous nephroscopy using local anesthesia with the patient supine, and evaluate the advantages and complications. MATERIALS AND METHODS: A total of 557 consecutive percutaneous nephroscopies were attempted in 221 men and 242 women in the supine position. Patient age ranged from 8 to 87 years (mean 55.1). Patients are supine with a 3 l. serum bag below the ipsilateral flank. We catheterize the affected uretheral meatus with a 5F catheter through a flexible cystoscope. The tract is infiltrated with local anesthesia. The skin is punctured in the posterior axillary line which corresponds to approximately 1 cm. above the bag. We use an Alken set to dilate the tract to 30F, which is the size of the Amplatz sheath we commonly use. RESULTS: Nephroscopy was performed in 519 cases (93.1%). Mean operation time was 85 minutes (range 15 to 240). Serious bleeding occurred in 3 cases. The colon was never damaged in patients treated in the supine position. CONCLUSIONS: Percutaneous nephroscopy using local anesthesia with the patient supine is safe and easy. According to our experience the advantages in comfort to the patient and feasibility to the surgeon justify its use.

Adolescent↗

Use of the scapular manipulation method to reduce an anterior shoulder dislocation in the supine position.

We report the successful use of the scapular manipulation method to reduce an anterior shoulder dislocation in a multiply traumatized patient in the supine position. We discuss the treatment options for multiply traumatized patients with anterior shoulder dislocations in whom cervical spine injury is a possibility. Although larger patient studies are necessary for confirmation, we show that in this particular case the scapular manipulation technique was safely employed. To our knowledge, this is the first reported case of use of the scapular manipulation method with the patient in the supine position.

Adult↗