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PubMed1988

Sleep apnea and body position during sleep.

In patients with obstructive sleep apnea, it is believed that body position influences apnea frequency. Sleeping in the lateral decubitus position often results in significantly fewer apneas, and some have recommended sleeping on the side as the major treatment intervention. Previous studies, although calculating apnea-hypopnea index (AHI) for supine and lateral decubitus positions, have not taken sleep stage into account. To examine the effect of both sleep stage and body position on apnea duration (AD) and frequency, we determined AHI and AD in all spontaneous body positions during rapid eye movement (REM) and non-REM (NREM) sleep by reviewing videotapes and polysomnograms from 11 overnight studies of 7 obese patients with severe sleep apnea. Consistent with previous work, AD was significantly longer in REM then in NREM (32.5 +/- 2.3 s versus 23.5 +/- 1.9 s; p less than 0.05). This difference persisted when adjusting for body position. AHI was greater on the back than on the sides (84.4 +/- 4.9/h versus 73.6 +/- 7.5/h, p less than 0.05), but after accounting for sleep stage, this difference remained only for NREM (103 +/- 4.8/h versus 80.3 +/- 9.2/h, p less than 0.05) and not for REM (83.6 +/- 5.3/h versus 71.1 +/- 4.2/h, p NS). Although reduced, AHI on the sides still remained clinically very high. Body position changed frequently throughout the night, but some patients spent little or no time on their back. We conclude that AD is longer in REM than NREM, regardless of position, and AHI is higher on the back only in NREM. As AHI remains very high on the sides, favoring the lateral decubitus position may not be as beneficial as previously thought in very obese patients. Less obese patients are more likely to benefit by position changes.

Adult↗
PubMed1998

Pulmonary blood flow does not redistribute in dogs with reposition from supine to left lateral position.

BACKGROUND: Recent studies have questioned the classical gravitational model of pulmonary perfusion. Because the lateral position is commonly used during surgery, the authors studied the redistribution of pulmonary blood flow in the left lateral decubitus position using a high spatial resolution technique. METHODS: Distributions of pulmonary blood flow were measured using intravenously injected 15-microm diameter radioactive-labeled microspheres in eight halothane-anesthetized dogs, which were studied in the supine and left lateral decubitus positions in random order. Lungs flushed free of blood were air-dried at total lung capacity and sectioned into 1,498-2,396 (1.7 cm3) pieces per animal. Radioactivity was measured by a gamma counter, and signals were corrected for piece weight and normalized to mean flow. RESULTS: Blood flow to the dependent left lung did not increase, and blood flow to the nondependent right lung did not decrease in the lateral position. The left lung received 39.3 +/-7.0% and 39.2+/-8.8% (mean +/- SD) of perfusion in the supine and left lateral positions, respectively. Detailed assessment of the spatial distributions of pulmonary blood flow revealed the lack of a gravitational gradient of blood flow in the lateral position. The distributions of blood flow did not differ in the supine and left lateral decubitus positions. CONCLUSIONS: Perfusion to each lung did not change with movement from the supine to the left lateral position. These findings contradict the prediction of increased dependent lung and decreased nondependent lung blood flow based on the gravitational model. It was concluded that the distribution of blood flow in the lateral position in dogs is dominated by pulmonary vascular structure.

Anesthetics, Inhalation↗
PubMed1988

Topographic location of the left atrium by computed tomography: reducing pulmonary artery catheter calibration error.

Two potential errors of pulmonary artery wedge pressure measurement that have received little attention are improper anatomic referencing of the transducer and nondependent placement of the pulmonary artery catheter tip. Transducers are often referenced to the midaxillary line of the supine patient. We utilized CT of the chest to determine accurately the topographic location of the left atrium to evaluate the accuracy of referencing the transducer in this position and to investigate atrial location in the lateral decubitus positions vis-à-vis external landmarks, so that more accurate referencing could be performed with a pulmonary artery catheter tip in the dependent lung. A prospective group consisting of ten patients referred for chest CT as well as retrospective review of 40 chest CT scans served as the study population. This study demonstrated a discrepancy between the perceived midaxillary line and the true location of the midleft atrium. Lateral decubitus CT scanning revealed a more readily localizable surface anatomic landmark which consistently and accurately predicts midleft atrial location. In addition, the appropriate decubitus position guarantees dependent catheter tip placement (Zone 3).

Calibration↗
PubMed1999

Relation of body position at the time of discovery with suspected aspiration pneumonia in poisoned comatose patients.

OBJECTIVE: The left lateral decubitus position is generally accepted as the position of choice to protect against aspiration pneumonia in comatose poisoned patients. We studied the relationship between initial body position during coma and subsequent development of suspected aspiration pneumonia (SAP). DESIGN: Observational, descriptive study. SETTING: Toxicology intensive care unit in a university hospital. PATIENTS: Acutely poisoned comatose patients admitted to our intensive care unit. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Glasgow Coma Scale score (GCS) and body position were recorded in poisoned patients on discovery. Chest radiographs were examined for infiltrates suggesting SAP within 24 hrs of hospitalization. The prone positioned patients had a lower incidence of SAP than patients in the lateral decubitus and supine positions, despite similar GCS scores. Patients in the semi-recumbent position had an incidence of SAP similar to prone patients, but with higher GCS values. CONCLUSIONS: The prone position appears to be associated with a lower incidence of SAP than the lateral decubitus position in comatose poisoned patients.

Acute Disease↗
PubMed1994

Body position affects recumbent postprandial reflux.

There is a lack of consensus as to whether there is a difference in the amount of gastroesophageal reflux when lying with the right versus the left side down. In an attempt to answer this question we conducted a two-part study. The first consisted of a questionnaire distributed to 103 gastroenterologists with a special interest in the esophagus. The second was a randomized study in 20 normal subjects given a high-fat meal to induce reflux. Postprandial reflux was monitored by esophageal pH testing for 4 h after random assignment to either the left or right lateral decubitus position (left or right side down) on different days. Of the 87 gastroenterologists responding to our survey, 45 were uncertain as to which position was associated with worse reflux. Among the 42 who did specify, 27 (64%) favored the right lateral decubitus position as associated with more reflux symptoms. The direct comparison of the two positions demonstrated that the total amount of reflux time was significantly (p < 0.05) greater with subjects in the right decubitus position (231 min) than in the left (117 min). Although total episodes of reflux were greater when lying on the right side (227), compared with the left (198), the difference was not significant. In addition, average overall acid clearance was significantly (p < 0.001) prolonged with right side down (0.77 +/- 0.14 min/episode) compared with left side down (0.29 +/- 0.08 min/episode).

Adult↗
PubMed2005

Breathing type and body position effects on sternocleidomastoid and suprahyoid EMG activity.

The objective of this study was to determine the effects of breathing type and body position on sternocleidomastoid and suprahyoid electromyographic (EMG) activity. The sample included 18 subjects with upper costal breathing type (study group) and 15 subjects with costo-diaphragmatic breathing type (control group). All individuals had natural dentition and bilateral molar support. EMG recordings at rest and while swallowing saliva were carried out by placing surface electrodes on the left sternocleidomastoid and left suprahyoid muscles. EMG activity was recorded while standing, seated upright, and in the lateral decubitus position. Upper costal breathing type subjects showed a significantly higher suprahyoid EMG activity at rest than costo-diaphragmatic subjects in all body positions studied (mixed model with unstructured covariance matrix). In the lateral decubitus position, both breathing types showed a significantly higher sternocleidomastoid EMG activity at rest and while swallowing saliva. The suprahyoid muscles demonstrated a significantly higher EMG activity at rest as well as in the lateral decubitus position (mixed model with unstructured covariance matrix). These results are relevant because sternocleidomastoid and suprahyoid muscles play an important role in controlling the head posture and mandible dynamics. The neurophysiological mechanisms involved are discussed.

Adult↗
PubMed1998

Effects of isoflurane on oxygenation during one-lung ventilation in pulmonary emphysema patients.

BACKGROUND: Hypoxic pulmonary vasoconstriction has an important role in human one-lung ventilation (OLV) in the lateral decubitus position under general anesthesia. During OLV, inhalational anesthesia may inhibit hypoxic pulmonary vasoconstriction and the decrease in arterial oxygenation. We studied the effect of isoflurane administration on arterial oxygen tension in chronic obstructive pulmonary disease patients. METHODS: Ten patients who had thoracoscopic laser ablation of bullous emphysema were studied. Patients received 2% isoflurane in oxygen from induction until the first 20 min of OLV in the lateral decubitus position, then were switched to 1% isoflurane lasting 20 min and next were switched to 0.5% isoflurane lasting 20 min. After each 20-min inhalation, pulmonary and hemodynamic parameters were measured. The given concentrations for isoflurane were merely vapor meter concentrations. RESULTS: PaO2/FIO2, Qs/Qt respiratory rate peak inspiratory pressure and PaCO2 showed no significant changes at each point of isoflurane. Expiratory tidal volume significantly decreased (P < 0.05) with 0.5% isoflurane compared to that with 2% isoflurane. Cardiac output, mean arterial pressure, mean pulmonary arterial pressure, systemic vascular resistance and pulmonary vascular resistance showed no significant changes at each point of isoflurane. CONCLUSIONS: In patients with pulmonary emphysema, arterial oxygenation is not affected by low isoflurane concentration during OLV in the lateral decubitus position.

Aged↗
PubMed1998

Effectiveness of prosthetic mandibular advancement for obstructive sleep apnea: analysis by sleep position.

Fifteen patients with obstructive sleep apnea were treated using prosthetic mandibular advancement (PMA). Each patient was evaluated in the supine and lateral decubitus positions with and without PMA. After PMA treatment, the mean intraesophageal pressure (Peso) in the supine position improved from -42.6 to -27.3 cmH2O and the mean apnea + hypopnea index (AHI) decreased from 48.8/h to 23.7/h. The mean Peso in the lateral decubitus position improved from -27.9 to -18.6 cmH2O and the mean AHI decreased from 9.6/h to 6.6/h. With PMA, respiratory, disturbance during sleep further improved by changing the body position from the supine to lateral decubitus position.

Adult↗
PubMed1990

The use of urethral, condom, and suprapubic catheters in aged nursing home patients.

In this study of 4,259 aged patients in 53 randomly selected nursing homes in Maryland, we found that 10% of women and 15% of men used a urine collection device. Among bedfast patients, 47% of women and 58% of men and, among patients with decubitus ulcers, 37% of women and 33% of men were using a urine collection device. The indwelling urethral catheter was the most commonly used device. Indeed, for women, few other options were available: 93% of women used this device. In women, multiple logistic regression analysis indicated that presence of a decubitus ulcer and occupation of a long-term care bed were the attributes most strongly associated with the use of the urethral catheter. Of men with urine collection devices, 43% were using the urethral catheter; poor mobility status was the characteristic most strongly associated with its use. Long-term urethral catheterization has been well studied and is associated with universal bacteriuria and with a number of complications. Options need to be further explored, particularly external urine collection devices for women. Furthermore, because urethral catheterization may be used as a management technique for decubitus ulcers, prevention of the latter may diminish the use of urethral catheters and their subsequent complications.

Activities of Daily Living↗
PubMed2006

Disparities between two common data sources on hospital nurse staffing.

PURPOSE: To compare nurse staffing measures derived from two widely used data sources: the American Hospital Association (AHA) Annual Survey of Hospitals and the California Office for Statewide Health Planning and Development (OSHPD). DESIGN: Descriptive cross-sectional study with measures of nurse staffing level and skill mix constructed from each database for 372 nonfederal, acute care hospitals in California. METHODS: Discrepancies in nurse staffing estimates between the two databases were examined. Relationships of nurse staffing with risk-adjusted patient outcomes (decubitus ulcer, failure to rescue, and mortality) were assessed through multivariate analyses and compared for nursing measures derived from the two databases. FINDINGS: For small, rural, or nonteaching hospitals, AHA reported substantially higher registered nurse (RN) hours per patient day than did OSHPD. RN proportion among licensed nurses matched most closely in the two databases. RN hours per patient day derived from both databases showed significant inverse relationships with decubitus ulcer and mortality, and the association was stronger for the measure based on the OSHPD data. RN proportion derived from the OSHPD data was significantly associated with all three patient outcomes, but the AHA measure had a significant relationship only with decubitus ulcer. CONCLUSIONS: Compared with the AHA survey, the OSHPD data on hospital nurse staffing appear to be more complete and also were more closely associated with patient outcomes. Efforts to refine the AHA survey as a national database for nurse staffing will significantly enhance the capacity for monitoring nurse workforce and its effect on quality of care.

American Hospital Association↗
PubMed1989

Effects of posture on the distribution of pulmonary ventilation and perfusion in children and adults.

In the adult the distributions of ventilation and of perfusion show the same directional dependence on gravity. In children, however, the distribution of ventilation in response to gravity is the reverse of that seen in adults. The aim of the current study was to determine whether perfusion showed the same reversal in children or followed the adult pattern. Distribution of perfusion was measured with intravenous technetium-99m macroaggregated albumin and distribution of ventilation with inhaled krypton-81m. Eighteen children and seven adults were studied; they had been referred for lung scanning for various respiratory problems. The effect of gravity was examined by giving aliquots of macroaggregated albumin and 81mKr by inhalation to the subject in the supine and the lateral decubitus position. Counts in the dependent lung were compared with those in the upper lung. The dependent lung in the lateral decubitus position received more of the total perfusion than it did in the supine position in seven children with a normal chest radiograph (mean 7.0%, range 4.8-10.9% more) and in 11 children with an abnormal radiograph (mean 3.4%(0.1-10.0%)). Ventilation, however, changed in the opposite direction, falling by 7.1% (-3.2% to -12.8%) in five children with a normal chest radiograph and 11.2% (-2.8% to -19.3%) in eight children with an abnormal radiograph. Fractional V/fractional Q (an index of the ventilation:perfusion ratio) decreased in the dependent lung in the children when they moved from the supine to the decubitus position. The same directional change was recorded in adults, but it was significantly less than in the children, irrespective of whether the chest radiograph was abnormal. In children and adults with various respiratory problems the effect of posture on the distribution of perfusion is similar.

Adult↗
PubMed2006

Cold pressor test protocol to evaluate cardiac autonomic function.

The primary objective of this study was to develop a cold pressor test (CPT) protocol to evaluate cardiac autonomic function. Secondary objectives were to assess CPT protocol reliability and to examine gender differences in response to orthostatic stress and the CPT. Healthy, normotensive men and women (n = 12 per group) completed 2 trials on different days in the left lateral decubitus and standing postures and during a 6 min CPT (hand immersion while seated). Measurements included R-R interval, blood pressure, ventilatory responses, spontaneous baroreflex sensitivity, and heart rate variability indices. During the CPT, blood pressure and the sympathetic nervous system (SNS) indicator increased significantly and low-frequency power, high-frequency power (normalized for tidal volume), and the parasympathetic nervous system (PNS) indicator decreased significantly. Standing caused significant increases in the SNS indicator and decreases in the R-R interval in both genders. The PNS indicator was higher in women than in men in the left lateral decubitus posture. The 6 min hand-immersion CPT provoked cardiac sympathetic activation and parasympathetic withdrawal; however, it is best suited to studies with a repeated measures design, as analysis of reliability suggests that responses are highly variable between individuals. Performing the CPT in the left lateral decubitus position may prevent vasovagal responses.

Adult↗
PubMed2002

High-frequency Doppler US of the prostate: effect of patient position.

PURPOSE: To evaluate cancer detection with directed biopsy of the prostate on the basis of high-frequency Doppler ultrasonographic (US) findings, and to determine the effect of patient position on the observed flow pattern. MATERIALS AND METHODS: Thirty-two patients were evaluated in the left lateral decubitus position with gray-scale, color Doppler, and power Doppler transrectal US. Up to four directed biopsy specimens were obtained on the basis of gray-scale and Doppler US findings, and modified sextant biopsy followed. Analysis of variance and the Wilcoxon signed rank test were used to evaluate the distribution of Doppler signals within the prostate. Three healthy volunteers with no known prostate disease were also examined in supine and both decubitus positions. RESULTS: In the patient group, both color and power Doppler US demonstrated increased flow on the left side of the prostate, with greater flow toward the base of the gland (P <.002). Consequently, 62 of 90 directed-biopsy cores were obtained in the left base and mid-gland. The positive biopsy rate for directed biopsy was not significantly different from that of sextant biopsy (P =.4). Seven patients had cancer that was identified with sextant biopsy, but only four cancers were identified with directed biopsy. Each of the three healthy volunteers demonstrated increased Doppler flow on the dependent side when the subject was in the lateral decubitus position. CONCLUSION: The positive yield of directed biopsy was similar to the yield of sextant biopsy. On the basis of observations made in healthy volunteers, the authors conclude that flow asymmetry in patients who underwent biopsy may have been related to patient position.

Adult↗
PubMed1984

Pleural effusion. Use of the semi-supine position for radiographic detection.

Chest radiographs of 100 routinely examined patients were evaluated to study the effectiveness of the oblique semi-supine position when attempting to identify pleural effusion. Comparisons were made to images obtained with the patient in the lateral decubitus position. Radiography was performed without noticeable discomfort for 62 patients in the lateral decubitus position and for 97 patients in the oblique semi-supine position. The visualization of free pleural fluid was not affected by the different body positions, but demonstration of encapsulated fluid was superior in views obtained with the patient in the oblique semi-supine posture. For most individuals with suspected pleural effusion, the oblique semi-supine position is preferable to the lateral decubitus position.

Adolescent↗
PubMed1992

Plain and computed radiography for detecting experimentally induced pneumothorax in cadavers: implications for detection in patients.

Pneumothorax was induced in cadavers to determine the effects of patient positioning and imaging modality (conventional screen-film and computed radiography) on radiographic findings. Chest radiography, with cadavers in the supine frontal, erect frontal, and left lateral decubitus positions, was performed at baseline and after injection of incremental quantities of air into the pleural space. Five radiologists independently interpreted each radiograph. The ability of the radiologists to diagnose pneumothorax varied by cadaver position and depended on volume of air. Overall, the left lateral decubitus view was most sensitive (88%) for diagnosis of pneumothorax, followed by the erect (59%) and supine (37%) views. Receiver operating characteristic curves and multiple repeated measures analysis of variance revealed no statistically significant difference between diagnostic proficiency with conventional screen-film radiography and that with computed radiography. The authors conclude that the lateral decubitus view is superior to the erect and supine views for pneumothorax detection and that conventional and computed radiography perform similarly in pneumothorax detection.

Cadaver↗
PubMed1986

Modification of pulmonary gas mixing by postural changes.

Mixing for two gases of markedly different gaseous diffusivity, helium (He) (mol wt = 4) and sulfur hexafluoride (SF6) (mol wt = 146) has been studied by a rebreathing method in different postures. In nine normal subjects duplicate measurements were made in the erect (seated), supine, and lateral decubitus posture, at a constant tidal volume (700 ml) and frequency (1 Hz) starting from functional residual capacity (FRC). Additional measurements were made on four of the subjects, rebreathing seated erect at a volume similar to the relaxed FRC supine and supine at a volume similar to the relaxed FRC seated. In the supine posture the mean breath number to reach 99% equilibrium (n99), was not significantly different for the two gases, 8.9 for He and 9.8 for SF6. There was a difference (P less than 0.01) when erect; n99 (He) = 8.2 and n99 (SF6) = 10.9. The greatest He-SF6 difference (P less than 0.001) was in the lateral decubitus position n99 (He) = 10.1 and n99 (SF6) = 15.9. The mean relaxed FRC as percent of seated was 71% supine and 75% in lateral decubitus posture. Rebreathing seated at a lower volume did not abolish the He-SF6 mixing difference nor did rebreathing at a higher volume when supine induce a He-SF6 mixing difference. Thus the effect of posture on gas mixing cannot be due solely to lung volume and must represent a convective and diffusive dependent change in the distribution of ventilation per unit lung volume.

Adult↗
PubMed1987

Lung epithelial permeability to aerosolized solutes: relation to position.

The lung epithelial permeability to inhaled solutes is primarily attributed to the degree of distension of the interepithelial junctions and thus of the alveolar volume. To assess this hypothesis, a submicronic aerosol of technetium-99m-labeled diethylenetriamine pentaacetate (99mTc-DTPA) was inhaled by eight normal subjects in left lateral decubitus (LLD). The regional lung clearance of 99mTc-DTPA was measured in LLD, then in right lateral decubitus (RLD) to reverse the relative distension of the alveoli. Although in LLD the deposition of the aerosol is the greatest in the gravity-dependent regions of the left lung, their 99mTc-DTPA clearances are significantly lower than those of the nondependent regions of the right lung (0.7 +/- 0.3 vs. 2 +/- 0.8%/min, P less than 0.001). In RLD, these regions placed in opposite positions significantly reversed their clearances (1.6 +/- 0.8 vs. 0.6 +/- 0.2%/min, P less than 0.001). Results indicate in lateral decubitus a gravity gradient of 99mTc-DTPA clearances independent of the aerosol deposition. This gradient of epithelial permeability to solutes appears to be influenced by the gradient of alveolar volume.

Adult↗
PubMed1982

Comparison of intraesophageal balloon pressure measurements with a nasogastric-esophageal balloon system in volunteers.

Recently, an esophageal balloon incorporated into a nasogastric tube was designed that allowed measurement of intraesophageal pressure. To define the performance of this nasogastric-esophageal balloon (NG-EB) system, comparative measurements were made with a standard esophageal balloon while subjects were in the sitting, supine, and left lateral decubitus and right lateral decubitus positions. Values for dynamic pulmonary compliance, pulmonary resistance, and cough pressure were not statistically different between the two systems. Mean static deflation pressure-volume (P-V) curves using the NG-EB were shifted to the left of the esophageal balloon P-V curve in all body positions, but static lung compliance (CL) was not statistically different. For both balloon systems, CL showed no significant difference between sitting and right lateral decubitus positions. Results from this study indicate that the NG-EB system acceptably reflects esophageal balloon pressure measurements and should be useful in estimating lung and chest wall mechanics in acutely ill patients requiring mechanical ventilation.

Adult↗