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PubMed2004

Development of respiratory motion reduction device system (RMRDs) for radiotherapy in moving tumors.

BACKGROUND: The internal target volume (ITV) for tumors in the abdomen or thorax includes sufficient margin for breathing-related movement of tumor volumes during treatment. Depending on the location of the tumor, the magnitude of the ITV margin extends from 1 to 3 cm, which increases substantially the volume of the irradiated normal tissue, hence resulting in an increase in normal tissue complication probability (NTCP). We developed a simple and handy method which can reduce ITV margins in patients with moving tumors: the respiratory motion reduction device system (RMRDs). METHODS: The patient's clinical database was structured for moving tumor patients and patient set-up error measurement and immobilization device effects were investigated. The system is composed of the respiration presser device (RPD) utilized in the prone position and the abdominal strip device (ASD) utilized in the supine position, and the analysis program, which enables analysis of patient set-up reproducibility. It was tested for analyzing the diaphragm movement from patients with RMRDs, the magnitude of the ITV margin was determined and the dose-volume histogram (DVH) was computed using treatment planning software. The dose to normal tissue in patients with and without RMRDs was analyzed by comparing the fraction of the normal liver receiving 50% of the isocenter dose. RESULTS: Average diaphragm movement due to respiration was 16 +/- 1.9 mm in the case of the supine position, and 12 +/- 1.9 mm in the case of the prone position. When utilizing the RMRDs, which was personally developed in our hospital, the value was reduced to 5 +/- 1.4 mm, and in the case in which the belt immobilization device was utilized, the value was reduced to 3 +/- 0.9 mm. In the case where the strip device was utilized, the value was proven to reduce to 4 +/- 0.3 mm. As a result of analyzing the volume of normal liver where 50% of the prescription dose is irradiated in DVH according to the radiation treatment planning, the use of the RMRD can create a reduction of 30% to the maximum. Also by obtaining the digital image, the function of comparison between the standard image, automated external contour subtraction, etc. was utilized to develop a patient set-up reproducibility analysis program that can evaluate the change in patient set-up. CONCLUSION: Internal organ motion due to breathing can be reduced using RMRDs, which is simple and easy to use in the clinical setting. It can reduce the organ motion-related planning target volume margin, thereby decreasing the volume of irradiated normal tissue.

Humans↗
PubMed1992

Three-component analysis of caloric nystagmus in humans.

Three-component analysis of caloric nystagmus, focusing on the horizontal, vertical, and torsional, using a computerized eye movement analysis system, was carried out in 10 normal human subjects. The caloric response was induced by cold stimulation to the right ear of the subjects in the supine and prone positions. In the supine position, the three components of nystagmus were toward the left (10 subjects), upward (eight subjects) or downward (two subjects), and clockwise (10 subjects). In the prone position, on the other hand, the three components were directed toward the right (10 subjects), downward (five subjects), upward (three subjects), and counterclockwise (10 subjects); there was no vertical direction in two subjects. These findings indicate that caloric stimulation activates the three semicircular canals simultaneously. Also the changes in the nystagmus direction in the supine and prone positions could be explained, at least partially, by the nonconvective component of caloric stimulation.

Adult↗
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↗
PubMed1996

Quadriplegia after lumbar disc surgery. A case report.

STUDY DESIGN: Case report. OBJECTIVE: To report a case of quadriplegia after surgery in the prone position for a herniated lumbar disc. SUMMARY OF BACKGROUND DATA: Ischemia in the vascular territories of the vertebral arteries after back surgery in the prone position is rare. Degenerative changes of the cervical spine or decreased blood flow to the head with mechanical vessel obstruction during extreme neck movements, systemic hypotension, and thromboembolism have mostly been implicated in the pathogenesis. METHODS: The case of a 33-year-old man undergoing surgery for an unilateral single level disc herniation at L4-L5 is presented. Within a few hours after surgery he developed quadriplegia and signs of occipital lobe dysfunction. He underwent magnetic resonance imaging investigation. Therapy included arterial blood pressure control, low molecular dextran, dexamethasone, bladder catheterization, and physiotherapy. RESULTS: Magnetic resonance imaging demonstrated intramedullary ischemic changes in the cervical spinal cord and at the borderline between anterior and posterior circulation. Outcome after 2 years is fair regarding the severe initial deficit-the patient walks alone with a cane and bladder function is under control. He is employed in a sedentary job. CONCLUSIONS: The authors believe that a temporary mechanical occlusion of a vertebral artery led to stasis, formation of thrombi, and subsequent embolism in the vertebrobasilar vascular territory. Extreme head rotation and neck extension is to be avoided in the prone position.

Adult↗
PubMedDate not supplied

Visual loss as a complication of non-ophthalmic surgery: a review of the literature.

Decreased visual acuity and loss of visual ability are devastating anesthetic and surgical complications. The incidence is greater in patients with preexisting hypertension, diabetes, sickle cell anemia, renal failure, gastrointestinal ulcer, narrow-angle glaucoma, vascular occlusive disease, cardiac disease, arteriosclerosis, polycythemia vera, and collagen vascular disorders. Precipitating factors for ischemic optic neuropathy include prolonged hypotension, anemia, surgery trauma, gastrointestinal bleeding, hemorrhage, shock, prone position, direct pressure on the globe, and long operative times. Prone and Trendelenburg positions can lead to visual loss related to decreased venous return from the head. Visual impairment may result from increased intracranial pressure, which contributes to undue pressure on the optic nerve. The prone position increases the risk of direct compression injury to the orbit and corneal abrasion. Astute attention to positioning is imperative, especially with the prone position. At-risk patients should receive transfusion once the calculated allowable blood loss has been surpassed Unacceptable hemoglobin and hematocrit values should be corrected preoperatively and levels monitored during the case to avoid intraoperative anemia in at-risk patients. The blood pressure of patients with predisposing diseases should be kept within normal limits. To avoid this devastating complication, it is imperative that anesthesia providers understand contributing factors and prevention strategies.

Anesthesia↗
PubMed2004

Visual loss as a complication of nonophthalmologic surgery: a review of the literature.

Decreased visual acuity and loss of visual ability are devastating anesthetic and surgical complications. The incidence is greater in patients with preexisting hypertension, diabetes, sickle cell anemia, renal failure, gastrointestinal ulcer, narrow-angle glaucoma, vascular occlusive disease, cardiac disease, arteriosclerosis, polycythemia vera, and collagen vascular disorders. Precipitating factors for ischemic optic neuropathy include prolonged hypotension, anemia, surgery, trauma, gastrointestinal bleeding, hemorrhage, shock, prone position, direct pressure on the globe, and long operative times. Prone and Trendelenburg positions can lead to visual loss related to decreased venous return from the head. Visual impairment may result from increased intracranial pressure, which contributes to undue pressure on the optic nerve. The prone position increases the risk of direct compression injury to the orbit and corneal abrasion. Astute attention to positioning is imperative, especially with the prone position. At-risk patients should receive transfusion once the calculated allowable blood loss has been surpassed. Unacceptable hemoglobin and hematocrit values should be corrected preoperatively and levels monitored during the case to avoid intraoperative anemia in at-risk patients. The blood pressure of patients with predisposing diseases should be kept within normal limits. To avoid this devastating complication, it is imperative that anesthesia providers understand contributing factors and prevention strategies.

Anesthesia↗
PubMed2002

Cerebellar hemorrhage after spinal surgery: report of two cases and literature review.

OBJECTIVE AND IMPORTANCE: Cerebellar hemorrhage remote from the site of surgery may complicate neurosurgical procedures. We describe our experience with two cases of cerebellar hemorrhage after spinal surgery and review the three cases previously reported in the literature to determine whether these cases provide insight regarding the pathogenesis of remote cerebellar hemorrhage. CLINICAL PRESENTATION: One of our patients developed cerebellar hemorrhage in the vermis and right hemisphere after transpedicular removal of a partially intradural T9-T10 herniated disc with the patient in the prone position. The other patient developed cerebellar hemorrhage in the vermis and bilateral hemispheres after L3-S1 decompression and instrumentation with the patient in the prone position, during which the dura was inadvertently opened. INTERVENTION: The first patient was treated conservatively and had mild residual dysarthria and gait ataxia 2 months after surgery. The second patient underwent exploration and revision of the lumbar wound with primary dural repair. The cerebellar hemorrhage was treated conservatively, and the patient had mild dysarthria and ataxia 1 month after surgery. CONCLUSION: Cerebellar hemorrhage must be considered in patients with unexplained neurological deterioration after spinal surgery. Dural opening with loss of cerebrospinal fluid has occurred in every reported case of cerebellar hemorrhage complicating a spinal procedure, supporting the hypothesis that loss of cerebrospinal fluid is central to the pathogenesis of this condition. Because remote cerebellar hemorrhage can occur after procedures with the patient in the supine, sitting, and prone positions, patient positioning seems unlikely to play a causative role in its occurrence.

Adult↗
PubMed2005

Comparison of lung area by chest radiograph, with estimation of lung volume by helium dilution during prone and supine positioning in mechanically ventilated preterm infants: a pilot study.

Measurement of lung volume may be useful in determining the degree of lung disease and for optimizing an infant's mechanical ventilator settings. A chest radiograph (CXR) is often used to estimate lung volume, because direct measurement, e.g., functional residual capacity (FRC), is neither practical nor possible in the neonatal intensive care unit. In supinely positioned infants, good correlation was found between lung area determined by CXR and lung volume, e.g., functional residual capacity (FRC). Whether this is true for the prone position is unknown. Since positioning may affect oxygenation and pulmonary function, we studied the relationship between lung area measured from CXR and FRC during both supine and prone positioning in 14 mechanically ventilated preterm infants. Lung area was determined from CXRs using computed radiography and FRCs obtained by helium dilution at end-expiration in both supine and prone positions. Reproducibility of lung area measurements was demonstrated by high correlations between two observers (R2 = 0.92 and 0.99 for supine and prone, respectively). When supine, lung area was 15.4 +/- 3.1 cm2, and FRC was 19.5 +/- 7.3 ml. In prone position, lung area was 16.7 +/- 4.2 cm2, and FRC 23.0 +/- 9.4 ml. There was a moderate to strong positive correlation between lung area and FRC for both positions (supine: r = 0.57, P < 0.03; prone: r = 0.63, P < 0.02). Lung area measured by computed radiography is a reproducible and practical method for estimating lung volume from routine chest X-rays in both supine and prone positions in mechanically ventilated preterm infants.

Female↗
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↗
PubMedDate not supplied

Fifteen-hour continuous esophageal pH monitoring: influence of position on gastroesophageal reflux among asymptomatic babies.

Using continuous esophageal pH monitoring, we examined 40 asymptomatic babies to evaluate the influence of different positions (prone, supine, right and left side lying position) on gastroesophageal reflux (GER). Several parameters including percent of time with a pH < 4, numbers of reflux episode, numbers of reflux episode lasting more than 5 min, average duration of longest reflux and average pH were studied. All babies were born fullterm and were 1 to 14 days old (average: 4 days). Male to female ratio was 1.7:1. For all parameters, except for average pH, we obtained more favorable results in prone position (p < 0.05). Continuous esophageal pH monitor is a suitable technique to evaluate GER under physiologic circumstances.

Esophagus↗
PubMed1985

Pleural space thickness in situ by light microscopy in five mammalian species.

The thickness of the pleural space was measured by a focusing method using a light microscope (X157, 2.5-micron depth of focus). In anesthetized animals, thin transparent parietal pleural windows were made by dissection of intercostal muscle. Multiple postmortem measurements were made of the combined thickness of the pleural space and the window by focusing in sequence on the lung surface and on 1- to 2-micron tantulum particles sprayed on the window. The window thickness was measured after creating a pneumothorax and retracting the lungs. In supine rabbits the pleural space measured at various heights on the costal surface was of uniform thickness (16 micron) except for a thicker region (62 micron) located within 3 mm of the most dependent part of the lung. The thicker region reverted to the uniform thickness after it was placed in a nondependent position by inverting the animal from the supine to prone position, indicating fluid drainage by gravity. In the prone position near midchest, pleural space thickness (t) averaged 6.9 micron in the mouse, 10.2 in the rat, 17.2 in the rabbit, 18.3 in the cat, and 23.6 in the dog. Animals of larger body mass (M, kg) had a wider pleural space: t = 13.1 X M0.20. There was no contact between the two pleurae, indicating that fluid lubrication facilitates sliding between the lung and chest wall. Based on the t vs. M relationship and estimates of the viscous flow of pleural liquid, pleural fluid exchange rate would be proportional to body mass and the work of sliding as a fraction of the work of breathing would be smaller in larger animals.

Animals↗
PubMed1994

Operative positioning for patients undergoing repair of craniosynostosis.

A further modification of our operative positioning protocol is presented, with several novel approaches to positioning that give only slightly less exposure than that obtained with the modified prone position, but that enable the entire cranial vault remodeling to be done in one operation. The addition of two techniques has obviated both the need to use the modified prone position (except in certain difficult cases) in recent years and the need to get preoperative cervical spine film evaluation. Two new operative positioning techniques that enable a large calvarial exposure are described: one (the gel-filled collar technique) focuses on the more anterior portion of the cranial vault, and the other (the angled horseshoe technique) focuses on the posterior portion; both provide an extensive exposure of the opposite portion of the calvarium.

Craniosynostoses↗
PubMed1993

Increase of hydroxyl free radical formation during venous stasis of dogs.

In the passive upright position, arterial and venous pressure in human feet increases capillary pressure, which leads to the filtration of fluid from the circulating plasma into the tissues of the feet. Loss of fluid concentrates both red cells and plasma so that the hematocrit and plasma protein concentration of venous blood leaving the feet greatly exceed their mean values in the circulation. To study this phenomenon in animals, the authors used beagle dogs maintained in an upright position and compared the results to those maintained in a prone position. In the passive upright position, red cell count, hematocrit, and total plasma protein concentrations were significantly increased. Therefore, we have determined the level of hydroxyl free radical formed as assessed by salicylate hydroxylation in the saphenous vein of dogs in an upright and normal position. Hydroxyl free radical formation was significantly higher in the veins of dogs in an upright position than in those in a prone position. The upright position model, which causes increases in hematocrit red cell count and total plasma protein in the saphenous vein, seems suitable for the study of drugs interfering in the pathophysiology of venous stasis. Indeed, the hematocrit increase of red cell count and total plasma protein in the saphenous vein of the beagle is similar to modifications observed in venous blood leaving the human foot after sitting. Moreover, the increase of .OH, concomitant with these modifications, may explain certain pathological observations, for instance, edema. The data clearly suggest that macromolecular extravasculation may be due to tissue injury caused by oxygen free radical formation in the blood vessels.

Animals↗
PubMedDate not supplied

Prevalence of prone sleeping position and selected infant care practices of North Dakota infants: a comparison of whites and Native Americans.

A cross-sectional prevalence study was done in four primary care clinics (two rural and two urban sites) and four Native American clinics serving members of the Chippewa, Sioux, Hidasta, Arikara, and Mandan tribes, all in North Dakota, to determine the prevalence of prone, supine, and side sleeping position in white and Native American infants. Questionnaires for 325 infants (259 whites and 66 Native Americans) between birth and 6 months of age were completed by the infants' mothers. They reported that 69 percent of the infants slept prone, 17 percent slept supine, and 14 percent slept on their side. Native American infants, who are at 3.2 times the risk of Sudden Infant Death Syndrome compared with other North Dakota infants, slept prone 46.9 percent of the time compared with 74.4 percent of white infants (chi 2 = 23.61; 1 df; P < .0001). No differences were observed in the prevalence of the side sleeping position. Eighteen percent of the infants slept in the position reported due to advice from a physician or nurse, 8 percent of the infants slept with more than two blankets, and 5 percent slept with a pillow. Native American infants in North Dakota did not have a higher prevalence of exposure to prone sleeping position.

Bedding and Linens↗
PubMed1993

[Six cases of anesthesia mumps].

Six cases of acute transient enlargement of the parotid gland under general anesthesia, so called anesthesia mumps, are reported. Patient 1 was placed in the left lateral position and the left parotid gland was subsequently observed to be diffusely enlarged. With five patients in the prone position, bilateral parotid gland enlargement was observed. Patient 1 complained of parotid swelling. Patient 4 suffered from slight tenderness of the right parotid gland. However, the others had no subjective symptoms. All cases of parotid swelling resolved spontaneously within 7 days. Changes in serum amylase during parotid enlargement were almost within normal range. Mechanical compression by sheet amadou may have produced the swelling in the patient who was placed in a lateral position. In the prone position, changes in the autonomic nervous system during surgical procedures and anesthesia, vascular congestion resulting from the surgical position, an overactive pharyngeal reflex stimulated by endotracheal intubation and mechanical ventilation are discussed as possible causes. Evaluation of the occurrence and clinical course of anesthesia mumps provided useful diagnostic and management data.

Aged↗
PubMed2004

Mechanical ventilation in children with acute respiratory failure.

PURPOSE OF REVIEW: Acute respiratory failure requiring mechanical ventilation continues to contribute to mortality and affect long-term functional outcomes in patients admitted to the pediatric intensive care unit (ICU). Studies in adults with acute respiratory distress syndrome (ARDS) far outnumber those conducted in the pediatric age group, and pediatric intensivists are left with the task of carefully selecting and critically appraising relevant adult data and extrapolating results to their domain of practice. RECENT FINDINGS: The recent ARDSNet study reinforces the use of low tidal volumes. Administration of surfactant is safe, but once again its beneficial effect was not sustained in a randomized trial. Surfactant proteins A and D have been shown to be of prognostic value in cases of acute lung injury. The effect of inhaled nitric oxide (NO) in patients with ARDS can be enhanced by aggressive lung recruitment strategies such as can be achieved using high-frequency oscillatory ventilation (HFOV). A recent adult trial shows good response rates but no significant long-term outcome benefit from prone positioning in patients with ARDS. Routine scheduled assessments of readiness for weaning and extubation may be more important than specific weaning modes and weaning criteria for children. A recent meta-analysis suggests that prophylactic dexamethasone use may decrease postextubation stridor and possibly reduce the need for reintubation in selected patients. Outcome data in children requiring mechanical support is encouraging, especially for high-risk groups such as bone marrow transplant (BMT) recipients, and may guide ethically challenging decision-making for these patients. SUMMARY: Mechanical ventilation strategies aiming for optimal alveolar recruitment with the judicious use of positive end-expiratory pressure (PEEP) and low tidal volumes will remain the mainstay for managing respiratory failure in children. Dexamethasone may prevent postextubation stridor. Prone positioning, surfactant therapy, HFOV, and inhaled NO are used sporadically and need to be evaluated for their effect on mortality and duration of ventilation.

Child↗
PubMed1997

A motor milestone change noted with a change in sleep position.

OBJECTIVE: To evaluate whether sleeping in the supine position resulted in changes in gross or fine motor developmental milestones observed at routinely scheduled well-child checkups at 4 or 6 months of age. DESIGN: A retrospective chart review. SETTING: One private pediatric practice involving 2 full-time and 2 part-time board-eligible or board-certified pediatricians. SUBJECTS: The study included 343 full-term infants whose weights were appropriate or large for gestational age, had no history of hospitalization other than for normal newborn care, and were examined in the office for their 4-month well-child checkup within 2 weeks of being 4 months old. METHODS: The Denver Developmental Screening Test-Revised was administrated at the 4- and 6-month well-child checkups. The primary sleep positions of the infants were determined by telephone survey, office interview, or letter after the 6-month checkup was completed. Background data collected from the mother for each mother-infant pair included maternal age at the time of birth, parity, and marital status, Medicaid status and ethnicity of the infant, and whether the infant was breast-fed. RESULTS: Infants who slept in the side or supine position were less likely to roll over at the 4-month checkup than infants who slept primarily in the prone position (P < .001). No significant differences were found when comparison by maternal age, parity, or marital status, Medicaid status or ethnicity of the infant, or the use of breast-feeding were considered. Other motor milestones screened did not show statistically significant changes. CONCLUSIONS: Sleep position significantly influences the age of achieving the gross motor developmental milestone of rolling over; infants who sleep in the side or supine position roll over later than infants who sleep in the prone position.

Child Development↗