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PubMed2006

[Pulmonary atelectasis in patients with neurological or muscular disease; gravity-related lung compression by the heart and intra-abdominal organs on persistent supine position].

We report 10 cases of pulmonary atelectasis diagnosed by chest computed tomography in patients with neurological or muscular disease. Atelectasis was frequently seen in hypotonic patients who could not roll over on their own. The atelectases located mostly in the dorsal bronchopulmonary segments, adjacent to the heart or diaphragm. Atelectasis diminished in two patients after they became able to roll themselves over. Gravity-related lung compression by the heart and intra-abdominal organs on persistent supine position can cause pulmonary atelectasis in patients with neurological or muscular disease who can not roll over by their own power. To confirm that the prone position reduces compression of the lungs, chest computed tomography was performed in both the supine and the prone position in three patients. Sagittal images with three-dimensional computed tomographic reconstruction revealed significant sternad displacements of the heart and caudal displacements of the dorsal portion of the diaphragm on prone position compared with supine position. The prone position, motor exercises for rolling over, and biphasic cuirass ventilation are effective in reducing gravity-related lung compression. Some patients with intellectual disabilities were also able to cooperate in chest physiotherapy. Chest physiotherapy is useful in preventing atelectasis in patients with neurological or muscular disease.

Abdomen↗

PubMed1997

Contributions of pulmonary perfusion and ventilation to heterogeneity in V(A)/Q measured by PET.

To estimate the contributions of the heterogeneity in regional perfusion (Q) and alveolar ventilation (V A) to that of ventilation-perfusion ratio (V A/Q), we have refined positron emission tomography (PET) techniques to image local distributions of Q and V A per unit of gas volume content (sQ and sV A, respectively) and V A/Q in dogs. sV A was assessed in two ways: 1) the washout of 13NN tracer after equilibration by rebreathing (sV A(i)), and 2) the ratio of an apneic image after a bolus intravenous infusion of 13NN-saline solution to an image collected during a steady-state intravenous infusion of the same solution (sV A(p)). SV A(p) was systematically higher than sV A(i) in all animals, and there was a high spatial correlation between sQ and sV A(p) in both body positions (mean correlation was 0.69 prone and 0.81 supine) suggesting that ventilation to well-perfused units was higher than to those poorly perfused. In the prone position, the spatial distributions of sQ, sV A(p), and V A/Q were fairly uniform with no significant gravitational gradients; however, in the supine position, these variables were significantly more heterogeneous, mostly because of significant gravitational gradients (15, 5.5, and -10%/cm, respectively) accounting for 73, 33, and 66% of the corresponding coefficient of variation (CV)2 values. We conclude that, in the prone position, gravitational forces in blood and lung tissues are largely balanced out by dorsoventral differences in lung structure. In the supine position, effects of gravity and structure become additive, resulting in substantial gravitational gradients in sQ and sV A(p), with the higher heterogeneity in V A/Q caused by a gravitational gradient in sQ, only partially compensated by that in sV A.

Animals↗

PubMed2001

Body position-dependent changes in cerebral hemodynamics during apnea in preterm infants.

The objective of the present study was to evaluate sleeping position-dependent effects on cerebral hemodynamics during apnea in preterm infants. To this end, polygraphic studies were performed on 15 stable preterm infants lying prone and lying supine. Changes in cerebral blood volume (DeltaCBV) and in cerebral hemoglobin oxygenation ((Delta)cHbD) in association with apnea were measured by near infrared spectroscopy. For comparison, apnea in the prone position was matched for duration to apnea in the supine position. A total number of 98 pairs of apnea were compared. The mean duration of apnea was 8.2+/-3 s. In both positions there was a predominance of decrease in CBV and cHbD in association with apnea. The mean decrease of cHbD (-1.57+/-1.82 micromol/l) and of CBV (-0.120+/-0.137 ml/100g brain) in the supine position was significantly pronounced compared to prone position (DeltacHbD: -1.18+/-1.77 micromol/l, DeltaCBV: -0.080+/-0.095 ml/100 g brain). The degree of DeltaCBV and DeltaHbD did not correlate with postconceptional or postnatal age (r2<0.01). In both positions there was a similar small decrease of SaO2 in association with apnea. In the supine position heart rate decreased slightly during apnea, whereas in the prone position no change in heart rate could be observed. The present study revealed a position-dependent different impact of apnea on cerebral hemodynamics. With regard to cerebral blood volume and oxygenation in association with apnea no negative effects of prone sleeping position could be observed in preterm infants.

Apnea↗

PubMed2005

Management of inferior breaks in pseudophakic rhegmatogenous retinal detachment with pars plana vitrectomy and air.

OBJECTIVE: To determine the role of pars plana vitrectomy without scleral buckling and air as a tamponade with 24 hours of prone positioning in the management of inferior breaks in primary pseudophakic rhegmatogenous retinal detachment. METHODS: Prospective, noncomparative, interventional case series. Fifteen consecutive eyes (15 patients) with primary pseudophakic rhegmatogenous retinal detachment with causative breaks located between the 4-o'clock and 8-o'clock positions underwent pars plana vitrectomy with air tamponade. The prone position was maintained for 24 hours. Anatomic and functional results are presented. RESULTS: The anatomic reattachment rate was 93.3% after 1 procedure and 100% at the 6-month visit. Mean preoperative best-corrected visual acuity was 20/60 (range, 20/400 to 20/25) and mean postoperative best-corrected visual acuity was 20/30 (range, 20/100 to 20/20). In 1 case the retina redetached at the second week because of an undetected break. Postoperative epiretinal membrane was observed in 1 case. CONCLUSION: Pars plana vitrectomy and air tamponade with only 24 hours of prone positioning postoperatively is effective in the management of primary pseudophakic rhegmatogenous retinal detachment with causative breaks between the 4-o'clock and 8-o'clock positions.

Adult↗

PubMed2005

Factors and circumstances influencing the development of hemorrhages in livor mortis.

Petechial hemorrhages or ecchymoses in the skin of the face and/or in eyelids and/or conjunctivae are one important feature in postmortem diagnosis of lethal strangulation. On the other hand, petechial bleedings can occur in various causes of death, especially in cases of neck or thoracic compression, they can occur in acute cardiac failure, as a result of blood or skin diseases or as a postmortem phenomenon. The focus of this investigation (retrospective study of 279 corpses, found initially in a prone position or some other face down position) was to analyse the frequency of postmortem (hypostatic) hemorrhages and factors which may influence their development. Petechial hemorrhages in livor mortis in the skin of the trunk and extremities were found in 110 cases (39%). The frequency ranged from 41% in the side position and 44% in the kneeling position to 50% in the prone position. Increasing intensity of livor mortis resulted in an increasing frequency of hemorrhages, up to 59%. In cases with a body-mass-index (BMI) of more than 26 the frequency of hemorrhages increased up to 64%. In cases without livor mortis when the corpses were found as well as in cases with complete movement of livor mortis after turning the corpses, no hemorrhages were found. If hypostasis was partly or completely fixed, the rate of hemorrhages increased up to 50%, without additional increase in longer postmortem intervals. Obviously postmortem petechiae develop neither very soon nor days after death, but within a period of several hours after death.

Abdomen↗

PubMed1995

Effect of body position on ventricular CSF methotrexate concentration following intralumbar administration.

PURPOSE: Intralumbar methotrexate is one of the primary therapeutic modalities for the prevention and treatment of meningeal leukemia. However, methotrexate distribution to the ventricles is limited and highly variable following intralumbar dosing, and cytotoxic concentrations of methotrexate are not always achieved or sustained in the ventricular CSF. We used a nonhuman primate model to determine the effect of body position on the caudal distribution of an intralumbar dose of methotrexate. METHODS: Methotrexate (1.0 mg) was administered by intralumbar injection to four animals, which were then immediately placed either in an upright sitting position or in a prone position for 1 hour, then upright. Each animal served as its own control and was studied in each position on at least one occasion. RESULTS: The mean peak ventricular methotrexate concentration was 0.12 mumol/L (range, 0.091 to 0.20) in animals that were immediately placed upright, compared with 2.81 mumol/L (range, 0.21 to 8.9) in animals that remained prone for 1 hour. The mean area under the concentration-versus-time curves (AUC) was 0.51 mumol/L.h (range, 0.26 to 1.1) in the upright animals and 12.0 mumol/L.h (range, 0.9 to 35.4) in the prone animals. CONCLUSION: Maintaining a prone position for 1 hour after an intralumbar dose increased the peak methotrexate concentration and drug exposure in ventricular CSF. CSF drug distribution following intralumbar therapy can be influenced by body position after the injection.

Animals↗

PubMed1997

Arterial to end-tidal carbon dioxide gradient and physiological dead space monitoring during general anaesthesia: effects of patients' position.

METHODS: One hundred and five ASA I-II patients, scheduled for elective surgical procedures were studied in order to evaluate the effect of different surgical postures on physiological pulmonary dead space (VDphys/ VT) and arterial to end-tidal carbon dioxide gradient [P(a-Et)CO2]. Patients were divided into four groups according to their position on the operating table: supine position (acting as control group, n = 33), 20 degree Trendelenburg position (n = 24), lateral position (n = 24) and prone position with convex saddle frame (n = 24). Physiologic dead space was measured using Enghoff modification of Bohr equation. Arterial CO2 partial pressure was measured by blood gas analysis and end tidal CO2 was measured by means of an infrared CO2 analyser. All measurements were performed 20 minutes after general anaesthesia induction, with patients mechanically ventilated by a constant inspiratory flow (TV = 8 ml kg-1, RR = 10-14, EIP = 10%) in order to reach a steady state end tidal CO2 ranging between 32 and 36 mmHg; afterwards surgery started. RESULTS: Arterial blood pressure showed a mean decrease of about 5-10% compared to baseline values, but no significant differences in arterial pressure decrease were found between the four groups. A significant VDphys/VT increase in postures other than supine was observed, unless it was statistically significant in lateral and prone position only; while P(a-Et)CO2 was higher in all postures compared to supine. Changes of intrapulmonary gas and blood distribution due to patients' posture are probably responsible for the observed physiologic dead space and CO2 gradient differences. CONCLUSIONS: In conclusion, the clinical practice of predicting PaCO2 from EtCO2 must be tempered by recognition of the potential magnitude of P(a-Et)CO2 gradient, which is higher than normal during general anaesthesia and further increased when positioning the patient other than supine.

Adult↗

PubMed1977

Cycloscopy of angle-closure glaucoma.

Cycloscopy was performed in eyes with primary angle-closure glaucoma and non-glaucomatous wide-angle. In all eyes of primary angle-closure glaucoma, the ciliary processes were accessible through the small pupil by cycloscopy with minimal or no indentation. In fellow eyes of the previously acute-attack eyes, the ciliary processes were visualized through the small pupil without indentation. On the contrary, in primary angle-closure glaucoma eyes the significant shallow chamber depth was seen in 66%, and the positive prone-position test in 41%. The results obtained seem to suggest that morphological changes of the ciliary processes might be causally related to the manifestation of primary angle-closure glaucoma, and that cycloscopy is a reliable diagnostic method.

Acute Disease↗

PubMed2005

Clinical usefulness of somatosensory evoked potentials for detection of brachial plexopathy secondary to malpositioning in scoliosis surgery.

STUDY DESIGN: A retrospective longitudinal study of 434 consecutive pediatric patients who underwent surgical correction of scoliosis, while being monitored for positional brachial plexopathy. OBJECTIVE: To evaluate the effectiveness of intermittent monitoring of ulnar nerve somatosensory evoked potentials (SSEPs) for detecting brachial plexus injury caused by malpositioning during scoliosis surgery. SUMMARY OF BACKGROUND DATA: Continuous intraoperative SSEP monitoring for spinal cord function has been well reported, and is widely accepted as the standard for spinal deformity correction surgery to detect and avoid neurologic injury. The use of SSEPs for the monitoring of ulnar nerve function intraoperatively as an indicator of brachial plexus function is becoming more accepted as a valid and useful technique to minimize intraoperative neurologic injuries during deformity corrections. METHODS: A review was conducted to assess the effect of ulnar nerve SSEP monitoring, as a measure of brachial plexus function, during anterior, posterior, or combined approach surgeries. The type of scoliosis, type of surgery and positioning, and surgical event at noted amplitude decrease were included in an analysis of variance for repeated measures, and a Student t test was performed for significant differences. RESULTS: A total of 27 patients had ulnar nerve amplitude decreases of > or =30%, resulting in a point prevalence of 6.2% for positional brachial plexopathy during positioning for all scoliosis surgeries. A significant difference was noted between the types of positioning, with prone positioning accounting for a higher rate of brachial plexopathy compared with anterior approach positioning (P < 0.01). No statistical difference exists as to the type of scoliosis present and the incidence of brachial plexopathy (P < 0.01). CONCLUSIONS: Avoidance of neurologic injury to the brachial plexus during scoliosis surgery is possible by early detection with ulnar nerve SSEP monitoring.

Brachial Plexus↗

PubMed1997

Interest of a therapeutic optimization strategy in severe ARDS.

STUDY OBJECTIVE: Evaluate the interest of the response to a therapeutic optimization as a predictor of prognosis in ARDS. DESIGN: Prospective study. SETTING: ICU of a University Hospital. PATIENTS: Thirty-six consecutive patients with severe ARDS addressed for extracorporeal carbon dioxide removal (ECCO2R). INTERVENTIONS: We studied the response during the first 2 days after arrival to the therapeutic optimization strategy consisting in a combination of the following: (1) decrease in extravascular lung water (diuretics or hemofiltration); (2) selection of the best ventilatory mode; (3) permissive hypercarbia; and (4) correction of hypoxemia by alveolar recruitment, additional continuous oxygen insufflation, body position changes (prone position), inhaled nitric oxide, enhancement of hypoxic pulmonary vasoconstriction with almitrine, and drainage of pleural or mediastinal effusions. In patients remaining severely hypoxemic despite these modalities, ECCO2R was then proposed. MEASUREMENTS AND RESULTS: Thirty-six patients were addressed after 8.3+/-5.5 days of mechanical ventilation. On arrival, mean simplified acute physiologic score was 46.8+/-14.2, multiple system organ failure score was 1.8+/-1.6, Murray score was 3.4+/-0.4, PaO2 was 75.3+/-31.3 (fraction of inspired oxygen [FIO2]=1) for a positive end-expiratory pressure level of 12.3+/-3.4 cm H2O. Nineteen of 36 patients improved their gas exchange within 2 days and their mortality was 21%. The seventeen remaining patients did not improve PaO2/FIO2; PaCO2 and airway pressures remained high and their mortality was 88%. This different response to therapeutic optimization appeared using stepwise logistic regression as the most predictive factor for mortality (p<0.05). CONCLUSIONS: In patients with severe ARDS, the response to an early performed therapeutic optimization used to improve hypoxemia appeared to be a highly discriminant factor distinguishing deceased from surviving patients.

Adolescent↗

PubMedDate not supplied

Design of an ultrasonic therapy system for breast cancer treatment.

This paper describes the design of a novel ultrasonic therapy system dedicated to the breast cancer treatment and the theoretical investigation of the heating characteristics of the system. The applicator is a cylinder comprised of a stack of rings. Each ring has up to 48 transducers mounted on the inside of the ring and directed towards the centre. The transducers operate in one of two frequency bands (1.8-2.8 MHz and 4.3-40.8 MHz), arranged alternately in each ring. During treatment the patient is positioned in prone position, with the breast immersed in water and surrounded by this array. This design was modelled and optimized by 3-D simulations for a variety of treatment conditions. The simulated results demonstrate that the system has an excellent capability to achieve and maintain a temperature distribution (41.5-44 degrees C) in a quadrant to a whole breast. Initial experiments using a single ring of transducers has been performed to verify the power deposition calculation.

Breast Neoplasms↗

PubMed1999

[Evaluation of child-rearing environmental factors that affect the occurrence of sudden infant death syndrome: interview conducted by public health nurses].

PURPOSE: We examined the child-rearing environmental factors that affect the occurrence of sudden infant death syndrome (SIDS) by using a nation-wide survey. METHOD: Infants who died due to SIDS between January 1996 and June 1997 in Japan were identified from death certificates. Controls of the same sex, birthplace, and birth months as the corresponding SIDS were chosen from birth certificates. Interviews of both cases and controls were undergone in January and February 1998 by public health nurses. RESULTS: The following Child-rearing factors exhibited a significant relationship with the occurrence of SIDS: 1. Concerning the sleeping position, the prone position was associated with increased risk compared to the supine position, with an odds ratio of 3.02 (95% c.i. 2.07-4.65). 2. Regarding the feeding method, artificial feeding only demonstrated a higher risk than breast feeding only, with an odds ratio of 4.92 (95% c.i. 2.78-9.63). 3. With regard to smoking, infants with both parents who smoked exhibited a higher risk than infants where neither parents smoked, with an odds ratio of 3.50 (95% c.i. 1.74-8.32).

Child Rearing↗

PubMed2003

The relationship between awake positioning and motor performance among infants who slept supine.

PURPOSE: The purpose of this study was to describe the gross motor development of infants who slept supine and spent different amounts of time in the prone position when awake. METHOD: Thirty infants who were six months old and slept supine were evaluated using the Alberta Infant Motor Scale (AIMS) and then divided into two groups: prone (n = 16) and no prone (n = 14) based on the number of times per day they were placed in prone position while awake. RESULTS: The prone group scored higher than the no prone group on the AIMS total scores (U = 36, p = 0.004), total percentile scores (U = 42, p = 0.003), and prone subscale scores (U = 25, p < 0.001). CONCLUSIONS: Gross motor performance as measured by the AIMS was more advanced in infants who slept supine and had been placed in the prone position when awake than in infants who slept supine but had limited or no experience in the prone position while awake. The influence of awake positioning needs to be considered when interpreting the developmental motor performance of infants who are six months old.

Journal Article↗

PubMed1991

Sleeping position and rectal temperature.

The effects of sleeping position upon body temperature were assessed by continuous monitoring of rectal temperature in 137 babies sleeping at home under conditions chosen by their parents. There were three groups of subjects: (1) normal babies aged 12-22 weeks whose temperature rhythms were developed, (2) normal babies aged 6-12 weeks who were developing their night time temperature rhythms, and (3) babies the night after diphtheria, pertussis, and tetanus immunisation, whose temperature rhythms were disturbed. Sleeping in the prone position was not associated with higher rectal temperatures at any time of night in young babies, nor did it exaggerate the disturbance of rectal temperature rhythm after immunisation. In older normal babies the prone position did not disturb rectal temperature in the first part of the night, though prone sleepers warmed a little faster prior to walking, especially in warm conditions. Prone sleepers were, however, born earlier in gestation and tended to be of lower birth weight. Normal babies can therefore thermoregulate effectively whatever their sleeping posture, even in warm conditions, though the prone position may make it slightly more difficult to lose heat. It is difficult to see how the prone position, even interacting with warm conditions, could induce lethal hyperthermia in otherwise normal babies. Perhaps the prone position is associated with other risk factors for sudden infant death syndrome.

Bedding and Linens↗

PubMed1994

Child safety seat use for infants with Pierre Robin sequence.

OBJECTIVE: To determine what child restraints would accommodate infants with Pierre Robin sequence who often require special attention in motor vehicle travel since microagnathia usually requires a prone position to keep the infant's airway open. RESEARCH DESIGN: Dynamic testing and clinical trial. SETTING: An Indiana children's hospital providing primary and tertiary care. PATIENTS: Four patients with Pierre Robin sequence are described to illustrate use of the modified infant car seat and the appropriateness of the car bed restraints for meeting requirements for prone positioning during travel. SELECTION PROCEDURES: Convenience sample. INTERVENTION: Selected restraints were loaned to families through a clinical setting until the patient was able to use a conventional child restraint. MEASUREMENTS AND RESULTS: Three child restraint systems were determined to accommodate the prone position necessary to keep the airway open for children with Pierre Robin sequence. Dynamic crash testing demonstrated the crashworthiness of an infant car seat modified to allow for prone positioning. Through a clinical trial, two car bed restraints were also found to provide safe prone positioning of infants. CONCLUSIONS: To enable safe transportation for infants with Pierre Robin sequence, health care providers can direct parents to appropriate resources for travel and can monitor the airway and oxygenation of the infant with Pierre Robin sequence before hospital discharge.

Equipment Design↗

PubMed2007

The effects of positioning on the Hering-Breuer reflex in the preterm infant.

The aim of this study was to determine the effect of positioning on the Hering-Breuer inflation reflex (HBIR) in the preterm infant. Seven, non-intubated, premature infants, ranging in birthweight from 732 to 1450 g with post-conceptual ages of 32-36 weeks were studied. In each infant, pulmonary function testing, including the HBIR was obtained using the SensorMedics 2600 during quiet sleep in the supine and prone position. The strength of the HBIR was quantified by the measurement of the percent prolongation of expiration after an occluded breath. Sleep states were categorized by the criteria of Prechtl. There was a significant difference in Hering-Breuer activity in the prone position versus the supine position with a consistently stronger reflex in the prone position. The mean percent prolongation of expiration was 237 +/- 108% in the prone position versus 95 +/- 32% in the supine position. Analysis of the data, using paired t-testing revealed a mean difference of 142 +/- 119% between prone and supine positions (P=0.028). Significant differences in the strength of the HBIR occur in relation to positioning in the preterm infant. Newborn positioning may affect pulmonary reflexes and may play a role in control of breathing.

Humans↗

PubMed1990

Caloric nystagmus in three dimensions under otolithic control in rhesus monkeys. A preliminary report.

The caloric nystagmus of rhesus monkeys in the 'optimum' supine or prone position was recorded three-dimensionally using magnetic search coils. The horizontal component of the nystagmus was in the direction expected from the convection flow theory of Bárány. The torsional component changed its direction according to the side of caloric stimulation independent of head position with regard to gravity, i.e., counterclockwise nystagmus by right ear stimulation and clockwise nystagmus by left ear stimulation both in the supine or in the prone positions. The direction of the vertical component depended upon the head position and not upon the side of stimulation, i.e., up-beating nystagmus in the supine position and down-beating nystagmus in the prone position. The durations and the contours of slow phase velocity of the horizontal, vertical and torsional components were different from each other. The origins of the first phase of caloric nystagmus in three dimensions may be explained by activation of all the three semicircular canals. As for the second phase of caloric nystagmus in the supine or in the prone position, the torsional component was comparatively strong and lasted the longest among the three components. The second phase of caloric nystagmus was markedly modified by head position with regard to gravity. These findings suggest that it is the otolithic organs that determine the moving plane of second phase caloric nystagmus.

Animals↗

PubMed2003

Sequential image analysis and measurement of pigmented lesions: false variations due to patient positioning.

Clinical researchers are evaluating the utility of obtaining sequential images of pigmented lesions taken over time for purposes of comparison with the aim of detecting subtle changes suggestive of melanoma. Therefore, the image acquisition process is critical and will need to be strictly standardized before any firm conclusions can be drawn from analysis of sequential images. The influence of patient positioning on the accuracy of sequential image analysis has not been considered in most studies evaluating sequential images. In this experimental study, the influence of patient positioning on the size and shape of an inked circle placed on the skin was determined and measured. Inked circular marks (15 mm in diameter, area 176.71 mm2) were placed on the skin of the lumbar and suprascapular areas of 60 consecutive patients. The diameter and area of the 'circle' was measured with the patient in the prone position with head centred, prone position with head turned to the right, prone position with head turned left, and in the seated position. Statistical analysis was performed with Student's t-tests (paired data). We observed statistically significant differences in the shape, mean maximal diameter and area of the inked circular marks on both the suprascapular area and in the lumbar area after changes of patient positioning (P<0.001). To conclude, the position of the patient must be fixed and standardized during acquisition of sequential images, at least for lesions 15 mm in diameter or larger. Furthermore, it is our opinion that the methods used to control for patient positioning should be reported in the methodology section of studies that report on comparison of sequential images. Only then can we accurately compare sequential images and avoid 'false positive lesion enlargement' being categorized as a true change.

Adolescent↗