Right Lateral Positions Research Articles

Effects of unilateral superimposed high-frequency jet ventilation on porcine hemodynamics and gas exchange during one-lung flooding.

Superimposed high-frequency jet ventilation (SHFJV) is suitable for respiratory motion reduction and essential for effective lung tumor ablation. Fluid filling of the target lung wing one-lung flooding (OLF) is necessary for therapeutic ultrasound applications. However, whether unilateral SHFJV allows adequate hemodynamics and gas exchange is unclear. To compared SHFJV with pressure-controlled ventilation (PCV) during OLF by assessing hemodynamics and gas exchange in different animal positions. SHFJV or PCV was used alternatingly to ventilate the non-flooded lungs of the 12 anesthetized pigs during OLF. The animal positions were changed from left lateral position to supine position (SP) to right lateral position (RLP) every 30 min. In each position, ventilation was maintained for 15 min in both modalities. Hemodynamic variables and arterial blood gas levels were repeatedly measured. Unilateral SHFJV led to lower carbon dioxide removal than PCV without abnormally elevated carbon dioxide levels. SHFJV slightly decreased oxygenation in SP and RLP compared with PCV; the lowest values of PaO2 and PaO2/FiO2 ratio were found in SP [13.0; interquartile range (IQR): 12.6-5.6 and 32.5 (IQR: 31.5-38.9) kPa]. Conversely, during SHFJV, the shunt fraction was higher in all animal positions (highest in the RLP: 0.30). In porcine model, unilateral SHFJV may provide adequate ventilation in different animal positions during OLF. Lower oxygenation and CO2 removal rates compared to PCV did not lead to hypoxia or hypercapnia. SHFJV can be safely used for lung tumor ablation to minimize ventilation-induced lung motion.

Potential differences in ephedrine requirements between left lateral and right lateral decubitus positions during neuraxial anesthesia for cesarean delivery.

The recent article by Wen et al., published in PLOS ONE, titled "Effects of neuraxial anesthesia in sitting and lateral positions on maternal hemodynamics in cesarean section: A systematic review and meta-analysis," caught my attention. In their study, the authors observed the effects of neuraxial anesthesia in sitting and lateral positions on maternal hemodynamics during cesarean section. Given the anatomical differences between the left and right sides of the body, which could result in differences in maternal hemodynamics and vasopressor requirements during neuraxial anesthesia for cesarean delivery, I was intrigued by the idea of further dividing the lateral position data from Wen et al.'s study into three subgroups: "left lateral position," "right lateral position," and "not mentioned" (where the included original study did not mention the lateral position) for a subgroup analysis. It seems to be more rigorous, the subgroup analysis revealed that the usage rate of ephedrine support was 1.42 times higher for parturients in the right lateral position compared to those in the sitting position. This finding supports our recommendation to distinguish between left and right lateral decubitus positioning in neuraxial anesthesia for cesarean delivery. But in contrast, no significant difference was observed between the sitting and lateral positions in terms of the number of parturients requiring ephedrine in Wen et al.'s. Given the limited research on the right-lateral position and its hemodynamic effects, further studies are needed to explore its clinical applications. Future research should also focus on conducting larger trials with greater sample sizes to evaluate the long-term neonatal outcomes associated with varying maternal positions. Additionally, researchers should conduct subgroup analyses that separate the left- and right-lateral positions to provide clearer guidance for anesthesiologists.

432 A Rare Case of Ipsilateral Foot Drop Due to Common Peroneal Nerve Palsy at the Level of Fibular Head Following Total Hip Arthroplasty

Abstract Background Common peroneal nerve (CPN) palsy after primary total hip arthroplasty (THA) is a rare complication with poor functional outcome and has a prevalence of 0.3-2.1%. Case Presentation A 77-year-old gentleman was diagnosed with severe osteoarthritis of the left hip and underwent a hybrid left total hip replacement via posterior approach in right-lateral position. There was no usage of spinal anaesthesia, leakage from the wound, intra-operative nerve injury or any localised haematoma. Post-operatively on day 3, he was noted to have foot drop with loss of foot eversion and dorsiflexion with sensory loss along the distribution of the superficial peroneal and tibial nerve. Clinical Outcomes Nerve conduction study of left lower limb showed absent left superficial peroneal sensory response, absent left peroneal to extensor digitorum brevis and tibialis anterior motor responses with denervation across the anterior and lateral left lower leg muscles suggestive of a severe partial lesion of the left common peroneal nerve at the level of fibular head. Patient was placed in a foot drop splint with follow-up neurological evaluation. Discussion Post-operative CPN palsy are mostly neuropraxias caused due to direct compression, either by surgical instruments or anatomical structures, or from tension or ischemia to the nerve during intra-operative limb manipulation or limb lengthening. Additionally, usage of cement less components combined with Enoxaparin or due to any haematoma may compress the nerve. Age, BMI and initial severity of sensory and motor neurological deficits are prognostic factors indicating recovery. Full recovery is between 16-56% of cases at an average of 15 months.

Ultrasound assessment of gastric contents and volume in patients undergoing endoscopic endonasal transsphenoidal surgery: a prospective observational study

Intraoperative ingestion of blood, cerebrospinal fluid, and irrigation fluid can lead to an increase in gastric volume, resulting in the potential risk of aspiration in patients after endoscopic endonasal transsphenoidal surgery (EETS). In this prospective observational study, we aimed to assess the volume of gastric contents in patients undergoing this neurosurgical procedure using ultrasound, and to determine the factors associated with volume change. Eighty-two patients diagnosed with pituitary adenoma were recruited consecutively. Semi-quantitative (Perlas scores: 0, 1 and 2) and quantitative (cross-sectional area, CSA) ultrasound assessments of the gastric antrum were performed immediately before and after surgery in the semi-recumbent and semi-recumbent right-lateral positions. Seven (8.5%) patients had antrum scores from preoperative grade 0 to postoperative grade 2; nine (11%) patients had antrum scores from preoperative grade 0 to postoperative grade 1. The mean ± standard deviation (SD) of increased gastric volume was 71.0 ± 33.1 mL and 236.5 ± 32.4 mL in postoperative grade 1 and 2 groups, respectively. Subgroup analysis showed that 11 (13.4%) patients (4 in grade 1 and all in grade 2) had postoperative estimated gastric volume > 1.5 mL kg−1 (mean ± SD 3.08 ± 1.67, range 1.51–5.01 mL kg−1). Logistic regression analysis revealed that older age, diabetes mellitus, and long surgical duration were independent risk factors for significant volume change (all P < 0.05). Our results showed a significant increase in gastric volume in some patients who underwent EETS. Bedside ultrasound measurements of gastric volume can be used to assess the postoperative aspiration risk, particularly in older diabetic patients with a longer surgical duration.

Effect of pre-operative carbohydrate loading on aspiration risk evaluated with ultrasonography in type 2 diabetes patients: a prospective observational pilot study

Owing to concerns about delayed gastric emptying or hyperglycemia, evidence is lacking regarding whether pre-operative carbohydrate loading can be routinely administered to patients with type 2 diabetes. The objective of this study was to determine the aspiration risk and gastric volume after pre-operative carbohydrate loading in patients with type 2 diabetes. A prospective, single-center, observational cohort study. The study was conducted at a tertiary teaching hospital in Seoul, Korea, from May 2020 to May 2021. Patients (n = 49) with type 2 diabetes underwent elective noncardiac surgery. All patients were administered carbohydrate loading two hours before surgery. Once in the operating room, they underwent gastric ultrasonography to determine gastric volume. The anesthesiologists monitored the patients' glucose concentrations during and after surgery. The primary outcome was the predicted risk of aspiration. The secondary outcomes were gastric volume, antral grade, satisfaction score, and perioperative glucose profile. Forty-nine patients were analyzed. All patients had a low risk of aspiration after carbohydrate loading, as follows: 33 (67.3%) patients classified as antral grade 0 and 16 (32.7%) patients classified as antral grade 1. The median time from carbohydrate drink ingestion to ultrasound examination was 120 min (IQR 115–139). After carbohydrate loading, the median gastric volume in the right-lateral position after carbohydrate loading was 2.64 ml (IQR 0.00–32.05). The mean glucose concentrations (SD) were 134 (24) mg/dl, 159 (37) mg/dl, 150 (32) mg/dl, and 165 (36) mg/dl at baseline, after induction, 30 min after surgery, and in the post anesthesia care unit, respectively. The median satisfaction score of the patients was 5 (IQR 4–5). Pre-operative carbohydrate loading may be feasible for patients with type 2 diabetes and without complications.Trial registration: ClinicalTrials.gov (NCT04456166). Registered on 2 July 2020.

Evaluation of gastric contents using ultrasound in full-term pregnant women fasted for 8h: a prospective observational study.

We aimed to evaluate the gastric volume and contents after an 8-h fasting period in full-term, non-laboring, pregnant women following a standardized meal. In this prospective observational study, we included full-term pregnant women scheduled for elective cesarean delivery. The participants were instructed to fast after a standardized meal (apple juice, bread, and cheese). Participants were scanned in the semi-recumbent and right-lateral positions 8h after the standardized meal. The primary outcome was the proportion of patients with gastric volume > 1.5mLkg-1 calculated by two equations. Secondary outcomes included the antral cross-sectional area and gastric volume. Data are expressed as frequency (%, 95% confidence interval [CI]), mean ± standard deviation (95% CI of the mean), or median (quartiles) as appropriate. Forty-one women were available for the final analysis. For the primary outcome, one participant (2.4%, 95% CI of 0.06 to 12.8%) had gastric volume > 1.5mLkg-1, and none had solids in the antrum. For the secondary outcomes, the mean (95% CI of the mean) of the antral cross-sectional area was 2.11 ± 0.72 (1.88 to 2.34) cm2 and 4.08 ± 1.80 (3.51 to 4.65) cm2 during the semi-recumbent and right-lateral position, respectively. The median (quartiles) gastric volume was 0.53 (0.32, 0.66) mLkg-1 and 0.33 (0.13, 0.52) mLkg-1 as estimated by Perlas et al. and Roukhomovsky et al. equations, respectively. After 8-h fasting following a standardized meal, full-term pregnant non-laboring women are less likely to have a high residual gastric volume.

Superimposed High Frequency Jet Ventilation Minimises Diaphragm, Bronchus, and Mediastinum Motion during One-Lung Flooding

Background: One-Lung Flooding (OLF) represents an ideal acoustic pathway for focused ultrasound ablation of lung tumours. Despite stabilization of the adjacent hemidiaphragm by OLF, standard Pressure-Controlled Ventilation (PCV) of the contralateral lung causes an unacceptable movement of the flooded lung. We examined whether Superimposed High Frequency Jet Ventilation (SHFJV) reduces lung motion compared to PCV during OLF. Methods: The study included 15 pigs: 10 underwent OLF; 5 controls underwent two-lung ventilation without OLF. Using ultrasound, diaphragm displacement on the flooded lung side was measured during PCV and SHFJV in the left lateral (LLP), Supine (SP), and Right Lateral Positions (RLP). Bronchus and mediastinum displacements were measured in the right lateral position. Results: Diaphragm displacement on the flooded lung side was significantly reduced during SHFJV, compared with PCV, in all animal positions (LLP: 7mm [4.75-8.0] vs. 17mm [14.75-19.0], P=0.0039; SP: 4mm [3.75-4.25] vs. 17mm [16.0–18.5], P=0.0039; RLP: 8mm [5.75-9.0] vs. 20mm [14.0-23.25], P=0.0078). Displacement of both the bronchus and mediastinum were significantly reduced during SHFJV, compared with PCV, in RLP (bronchus: 2.0mm [1.75-2.25] vs. 3.0mm [2.75-3.0], P=0.027; mediastinum: 4.5mm [4.0-5.0] vs. 10mm [7.0-10.0], P=0.0078. Conclusion: Thus, SHFJV minimises diaphragm, bronchus, and mediastinum motion during OLF, which is a prerequisite for effective lung tumour ablation.

Gastric Residual Volume Assessment by Gastric Ultrasound in Fasting Obese Patients: A Comparative Study

BackgroundGastric ultrasound is an emerging tool for preoperative evaluation of gastric content and volume.ObjectivesTo assess gastric residual volume in normal-weight and obese patients scheduled for elective surgery.MethodsThis prospective observational study was conducted on 100 patients assigned to two groups of 50 patients each. The obese group included patients with body mass index (BMI) of 30 - 40 and American Society of Anesthesiologists (ASA) grade II and those with BMI > 40 and ASA III without other comorbidities; the normal-weight group included patients with normal BMI and ASA I. Gastric volume was predicted in each group using sonographic measurement of antral cross-sectional area (CSA) in semi-sitting and right lateral positions (RLP); the two groups were compared to assess the risk of aspiration for each group preoperatively.ResultsDespite intergroup differences in antral CSA, the sonographically predicted gastric volume was < 1.5 mL/kg in both groups in both positions. Both groups were at a low risk for aspiration, and 98% of the patients showed grade 0 or 1 in antrum assessments, corresponding to an empty antrum and minimal fluid only in the RLP, respectively. Only 2% of the patients in both groups showed a distended antrum in both positions.ConclusionsDespite the differences in CSA between obese and normal-weight participants in both positions (obese > normal-weight), both groups showed a low predicted gastric residual volume < 1.5 mL/kg and were at low risk for aspiration, provided that fasting was initiated at least 8 hours before elective surgery.

Nystagmus characteristics of healthy controls.

BACKGROUND:Healthy controls exhibit spontaneous and positional nystagmus which needs to be distinguished from pathological nystagmus.OBJECTIVE:Define nystagmus characteristics of healthy controls using portable video-oculography.METHODS:One-hundred and one asymptomatic community-dwelling adults were prospectively recruited. Participants answered questions regarding their audio-vestibular and headache history and were sub-categorized into migraine/non-migraine groups. Portable video-oculography was conducted in the upright, supine, left- and right-lateral positions, using miniature take-home video glasses.RESULTS:Upright position spontaneous nystagmus was found in 30.7% of subjects (slow-phase velocity (SPV)), mean 1.1±2.2 degrees per second (°/s) (range 0.0 – 9.3). Upright position spontaneous nystagmus was horizontal, up-beating or down-beating in 16.7, 7.9 and 5.9% of subjects. Nystagmus in at least one lying position was found in 70.3% of subjects with 56.4% showing nystagmus while supine, and 63.4% in at least one lateral position. While supine, 20.8% of subjects showed up-beating nystagmus, 8.9% showed down-beating, and 26.7% had horizontal nystagmus. In the lateral positions combined, 37.1% displayed horizontal nystagmus on at least one side, while 6.4% showed up-beating, 6.4% showed down-beating. Mean nystagmus SPVs in the supine, right and left lateral positions were 2.2±2.8, 2.7±3.4, and 2.1±3.2°/s. No significant difference was found between migraine and non-migraine groups for nystagmus SPVs, prevalence, vertical vs horizontal fast-phase, or low- vs high-velocity nystagmus (<5 vs > 5°/s).CONCLUSIONS:Healthy controls without a history of spontaneous vertigo show low velocity spontaneous and positional nystagmus, highlighting the importance of interictal nystagmus measures when assessing the acutely symptomatic patient.

Lateral position during severe mono-lateral pneumonia: an experimental study

Patients with mono-lateral pneumonia and severe respiratory failure can be positioned in lateral decubitus, with the healthy lung dependent, to improve ventilation-perfusion coupling. Oxygenation response to this manoeuvre is heterogeneous and derecruitment of dependent lung has not been elucidated. Nine pigs (32.2 ± 1.2 kg) were sedated and mechanically ventilated. Mono-lateral right-sided pneumonia was induced with intrabronchial challenge of Pseudomonas aeruginosa. After 24 h, lungs were recruited and the animals were randomly positioned on right or left side. After 3 h of lateral positioning, the animals were placed supine; another recruitment manoeuvre was performed, and the effects of contralateral decubitus were assessed. Primary outcome was lung ultrasound score (LUS) of the dependent lung after 3-h lateral positioning. LUS of the left non-infected lung worsened while positioned in left-lateral position (from 1.33 ± 1.73 at baseline to 6.78 ± 4.49; p = 0.005). LUS of the right-infected lung improved when placed upward (9.22 ± 2.73 to 6.67 ± 3.24; p = 0.09), but worsened in right-lateral position (7.78 ± 2.86 to 13.33 ± 3.08; p < 0.001). PaO2/FiO2 improved in the left-lateral position (p = 0.005). In an animal model of right-lung pneumonia, left-lateral decubitus improved oxygenation, but collapsed the healthy lung. Right-lateral orientation further collapsed the diseased lung. Our data raise potential clinical concerns for the use of lateral position in mono-lateral pneumonia.

The Effect of Semirecumbent and Right Lateral Positions on the Gastric Residual Volume of Mechanically Ventilated, Critically Ill Patients.

Delay in stomach discharge is a challenge for patients who are tube fed and may result in serious side effects such as pneumonia and malnutrition. This study was designed to determine the respective effects of the semirecumbent (SR) supine and right lateral (RL) with a flatbed positions on the gastric residual volume (GRV) of mechanically ventilated, critically ill adult patients. A randomized, crossover clinical trial design was used to investigate GRV in 36 critically ill, ventilated adult patients who were hospitalized in the intensive care unit. GRV was measured at 3 hours after three consecutive feedings. GRV was first measured in all of the participants in the supine position; after which, participants were randomly assigned into one of two therapeutic positioning groups (Group A: assessment in the SR position and then the RL position; Group B: assessment in the RL position and then the SR position). GRV was significantly lower in both the SR and RL positions than in the supine position. GRV in the SR and RL positions did not vary significantly. The in-group measurements for GRV did not significantly differ for any of the three positions. In Group A, GRV was significantly lower at each subsequent measurement point. Positioning patients in the RL and SR positions rather than in the supine position is an effective strategy to reduce GRV. Furthermore, placing patients in either the RL or SR position is an effective intervention to promote faster digestion and feedings.

Comparison of bolus- and filtering-based EIT measures of lung perfusion in an animal model

Objective: Two main functional imaging approaches have been used to measure regional lung perfusion using electrical impedance tomography (EIT): venous injection of a hypertonic saline contrast agent and imaging of its passage through the heart and lungs, and digital filtering of heart-frequency impedance changes over sequences of EIT images. This paper systematically compares filtering-based perfusion estimates and bolus injection methods to determine to which degree they are related. Approach: EIT data was recorded on seven mechanically ventilated newborn lambs in which ventilation distribution was varied through changes in posture between prone, supine, left- and right-lateral positions. Perfusion images were calculated using frequency filtering and ensemble averaging during both ventilation and apnoea time segments for each posture to compare against contrast agent-based methods using Jaccard distance score. Main results: Using bolus-based EIT measures of lung perfusion as the reference frequency filtering techniques performed better than ensemble averaging and both techniques performed equally well across apnoea and ventilation data segments. Significance: Our results indicate the potential for use of filtering-based EIT measures of heart-frequency activity as a non-invasive proxy for contrast agent injection-based measures of lung perfusion.

Ultrasound assessment of gastric emptying time after a standardised light breakfast in healthy children: A prospective observational study.

Current guidelines recommend 6 h of fasting for solids before anaesthesia. However, prolonged fasting may lead to discomfort, hunger, thirst, misbehaviour and lipolysis. To prevent this, a more liberal fasting regimen has been empirically implemented in our children's hospital, allowing a shorter fasting time of 4 h for a standardised light breakfast. The aim of this study was to determine the gastric emptying time after a standardised light breakfast in healthy children. A prospective observational noninterventional study. After fasting overnight, the children had a standardised light breakfast. Before and afterwards, ultrasound examinations of the gastric antrum were performed hourly to determine the gastric antral area (GAA), which is a surrogate parameter for gastric volume in children in the right lateral position (RLP). Demographic data and fasting times are presented as mean ± SD (range) and GAA as median (interquartile range). Twenty-two children aged 7.8 (2.5 to 13.6) years volunteered for this study. After fasting overnight [735 ± 120 (467 to 930) min], the initial GAA was 3.06 (2.35 to 4.03) cm in RLP. After the light breakfast, GAA in RLP initially increased and decreased subsequently. After 4 h, GAA in RLP was lower than the initial value (median of differences -0.54, 95% confidence interval -1.00 to -0.07, P < 0.05). Correlation between GAA in RLP and fasting time was significant (r = -0.62, P < 0.0001). Using a linear regression model, the calculated mean gastric emptying time after the standardised light breakfast was 211 min for GAA = 3.06 cm. The study showed a mean gastric emptying time of less than 4 h after a standardised light breakfast in children. These results encourage our current clinical practice and support the efforts towards a more liberal fasting regimen for light meals in paediatric anaesthesia. German Registry of Clinical Studies (DRKS-ID: DRKS 00013893).

Combined spinal-epidural anesthesia with hypobaric ropivacaine in sitting position significantly increases the incidence of hypotension in parturients undergoing cesarean section.

Maternal position during induction of combined spinal-epidural anesthesia (CSEA) may affect hemodynamics and block characteristics. This study aimed to assess whether the sitting position is more likely to induce hypotension and higher block level than the lateral position in CSEA with hypobaric ropivacaine. Ninety American Society of Anesthesiologists physical status I and II parturients undergoing elective cesarean section were randomized into three groups: the sitting, left-lateral, and right-lateral position groups. The L3-4 interspace was selected as the puncture site, and subarachnoid injection of 2.5 mL 0.5% hypobaric ropivacaine was administered. After the epidural catheter was inserted and fixed, the patient's position was changed to the left-leaning supine position. The blood pressure was measured once every 1 min followed by once every 3 min after the delivery. The sensory block level was regularly measured. A total of 88 parturients were included in this study. The incidences of hypotension in the sitting, left-lateral, and right-lateral position groups were 72%, 38%, and 40%, respectively, P = 0.012. Incidence and total dose of the phenylephrine supplement in the sitting position group were significantly higher than in the other two groups. The sitting position group showed a significantly higher block level (T4 [T3, T4]) as compared to the left-lateral (T6 [T5, T6]) and right-lateral position groups (T6 [T4, T6]), P < 0.01. The Apgar scores of neonates at 1 min and 5 min, and the pH values of the umbilical arterial and venous blood were similar among the three groups. As compared to the lateral positions, CSEA with hypobaric ropivacaine in the sitting position is more likely to cause hypotension and excessively high block level.

Comparison of Macintosh laryngoscope and C-MAC video laryngoscope for intubation in lateral position.

Background and Aims:Endotracheal intubation is conventionally performed when the patient is in supine position. It may be required to secure airway in laterally positioned patient. Tracheal intubation in lateral position seems to be difficult because the laryngeal view is compromised. Hence, C-MAC video laryngoscope (Karl Storz, Germany), a newer device using a modified macintosh blade may be useful for intubation in lateral position.Material and Methods:A total of 100 American Society of Anesthesiologists Grade I and II patients, randomly allotted to C-MAC or direct laryngoscopy group. Patients with difficult airway were excluded. After induction of anesthesia, patient was put in right-lateral position and intubation was carried out by consultant who is well-versed in using C-MAC laryngoscope. Time for intubation, number of attempts, Modified Cormack – Lehane grade, mucosal injury, and external laryngeal manipulation applied were noted.Statistical Analysis:Demographics and baseline airway assessments were analyzed using summary statistics. Unpaired t-test was used to assess intubation time. Number of attempts, esophageal intubation, dental injury, mucosal injury, use of stylet, and application of external laryngeal manipulation were analyzed using Chi-square test.Results:Overall intubation success rate was 100%. The time taken in C-MAC group was 24.8 ± 8.5 s and in direct group was 33.8 ± 9.12 s. The number of intubation attempts was not significant. Cormack – Lehane grade was better with C-MAC laryngoscope. Mucosal injury and use of external laryngeal manipulation was more in direct group.Conclusion:C-MAC is better than Macintosh laryngoscope for intubation in lateral position.

Effects of Ventilation and Catheter Position on Catheter Movement on the Tricuspid Annulus during Ablation in Children

There are little data on the effect of catheter position and mechanical ventilation on ablation catheter stability during electrophysiology study in children. We sought to determine the magnitude of catheter movement with mechanical ventilation, the effect of ventilation maneuvers on catheter movement, and to compare the degree of movement observed between the right lateral (RL) and right posteroseptal (RPS) regions. From June 2012 to June 2013, patients ≤ 21 years of age undergoing ablation for supraventricular tachycardia with CARTO® 3 (Biosense Webster, Diamond Bar, CA, USA) were included. During mapping the ablation catheter was placed in the RPS and RL regions and the magnitude of catheter movement (mm) was measured using CARTO® 3. Measurements were made during routine ventilation and with a maximal inspiration maneuver between end-expiration (ENDEX) and peak-inspiration (PEAKINS). Twenty-one patients were included: 12 males (57%), age 13 ± 3 years, weight 55 ± 14 kg. Indications for ablation were: 10 Wolff-Parkinson-White, seven atrioventricular node re-entry tachycardia, four concealed accessory pathway. Mechanical ventilation was used in all cases. The magnitude of catheter movement was 3.6 ± 1.7 mm with routine ventilation and 6.2 ± 4.1 mm between ENDEX and PEAKINS (P ≤ 0.01). Catheter movement was greater in the RL compared to the RPS region with routine ventilation (RL 4.3 ± 1.6 vs RPS 3.0 ± 1.5; P < 0.01) and between ENDEX and PEAKINS (RL 8.3 ± 4.7 vs RPS 4.0 ± 1.7; P < 0.01). Ventilation and catheter position both have significant impact on the degree of catheter movement during ablation. Movement was greatest in the RL position. This may partially explain the lower success rates of ablation in the RL region.

Effect of lateral positioning on gastroesophageal reflux (GER) and underlying mechanisms in GER disease (GERD) patients and healthy controls

Posture has been shown to influence the number of transient lower esophageal sphincter relaxation (TLESRs) and gastroesophageal reflux (GER), however, the physiology explaining the influence of right lateral position (RLP), and left lateral position (LLP) is not clear. The aim of this study was to determine the influence of RLP and LLP on TLESRs and GERD after a meal in GER disease (GERD) patients and healthy controls (HC) while monitoring gastric distension and emptying. Ten GERD patients and 10 HC were studied for 90 min (30 min test meal infusion, 30 min postprandial in either RLP or LLP (randomly assigned) and 30 min in alternate position). The study was repeated on a separate day in reverse position order. TLESRs, GER, and gastric emptying rate were recorded using manometry, multichannel intraluminal impedance, and (13) C-octanoate breath tests. Gastric distension was visualized by five serial gastric volume scintigraphy scans during the first 30 min. Gastroesophageal reflux, (GER) disease patients had increased numbers of TLESRs in RLP compared to LLP in the first postprandial hour [5 (4-14) and 4.5 (2-6), respectively, P = 0.046] whereas the number of TLESRs was not different in RLP and LLP [4 (2-4) and 4 (3-6), respectively, P = 0.7] in HC. Numbers of GER increased similar to TLESRs in GERD patients. In GERD patients, gastric emptying reached peak (13)CO(2) excretion faster and proximal gastric distension was more pronounced. In GERD patients, TLESRs, GER, distension of proximal stomach, and gastric emptying are increased in RLP compared to LLP. This effect is not seen in HC.

SU-E-J-25: Dosimetric Characterization of an OBI System Using Gafchromic XRQA2 Film.

Accurate knowledge about the radiation dose due to the imaging component of an OBI supported linear accelerator is very important. Though films provide excellent spatial resolution, there are problems regarding sensitivity and energy dependence at kV energies. XRQA2 film (0.1-20 cGy) is primarily for measurements in kV range. We demonstrate their use for absolute dosimetry for an OBI system. H&D curves were generated using a kV therapy x-ray unit in the range of 0-15 cGy. A 25-cm diameter water-equivalent cylindrical phantom with 2.5-cm thick slabs was used on Varian Trilogy linac. XRQA2 films were cut into circular diameter and sandwiched between 2 slabs of the cylindrical phantom to measure the percentage depth dose of the CBCT scans. Additional film pieces were wrapped around the cylinder for surface dose. To get sufficient signal, 5 CBCT scans were taken per imaging acquisition template e.g. head standard dose. After 24 hours post-irradiation, films were scanned using Epson V700 scanner in reflection mode. Only red channel was used for dosimetric analysis using RIT software. High-Quality head acquisition template resulted in a dose at 0.2, 1.3, 2.7, and 2.7 cGy on AP, left-lateral, posterior and right-lateral positions of the phantom, respectively. Low-quality thorax acquisition resulted in 1.4, 1.6, 1.5, and 1.4 cGy. The PDD at 12.5-cm (isocenter) was of the order of 40%. While the PDD was fairly uniform from left to right, the PDD along the AP/PA direction were showing almost continuous fall off with PDD at isocenter of ∼40%. Analysis of low-quality head PDDs show little fall off dose with depth though the overall magnitude was less with PDD at the isocenter only marginally lower than the maximum along the medial and anterior posterior axis. Gafchromic XRQA2 film provides a useful tool to evaluate and characterize an OBI system.

Airway Scope for Tracheal Intubation in the Lateral Position

Tracheal intubation in the lateral position is difficult because the laryngeal view is compromised during direct laryngoscopy. The Airway Scope facilitates intubation even when laryngeal views are poor with direct laryngoscopy, as they often are in the lateral position. We thus compared the efficacy of the Airway Scope in supine patients with those in the left- and right-lateral positions. Anesthetized adults were randomly assigned to supine, left-lateral, or right-lateral position (n = 43 for each group). Laryngeal views were obtained in the designated position with a Macintosh laryngoscope, and patients' tracheas were subsequently intubated with the Airway Scope. Specifically, we tested the hypothesis that the time required for intubation in the left- and right-lateral positions is not increased by >10 seconds compared with tracheal intubation in the supine position. Overall intubation success was 100% in the 2 lateral positions, and 98% in the supine position. Intubation times were similar in the left-lateral (24 [5] seconds, mean [SD]), right-lateral (24 [6] seconds), and supine (22 [7] seconds) positions. The numbers of required intubation attempts were similar in the 2 lateral positions and in the supine and left-lateral positions. However, more intubation attempts were required in the supine position than in the right-lateral position (P = 0.004). The incidences of airway complications were similar in each position; no hypoxia, dental injury, or esophageal intubation was observed. Modified Cormack-Lehane and the percentage of glottic opening scores obtained with the Macintosh laryngoscope did not differ between the 2 lateral positions, but the modified Cormack-Lehane and percentage of glottic opening scores were superior in the supine position (all P < 0.001) compared with either of the lateral positions. Despite worse laryngoscopic views in either lateral position than when patients were supine, intubation with the Airway Scope offered high success rates. Furthermore, intubation time using the Airway Scope in either lateral position was not longer by >10 seconds than in the supine position. The Airway Scope thus seems to be a useful tool when tracheal intubation is required in a laterally positioned patient.

Predictors of Response to a Nasal Expiratory Resistor Device and Its Potential Mechanisms of Action for Treatment of Obstructive Sleep Apnea

A one-way nasal resistor has recently been shown to reduce sleep disordered breathing (SDB) in a subset of patients with Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS). The purpose of this study was to examine characteristics predictive of therapeutic response to the device and provide pilot data as to its potential mechanisms of action. PATIENTS, INTERVENTIONS, AND MEASUREMENTS: 20 subjects (15M/5F, age 54 ± 12 years, BMI 33.5 ± 5.6 kg/m²) with OSAHS underwent 3 nocturnal polysomnograms (NPSG) including diagnostic, therapeutic (with a Provent® nasal valve device), and CPAP. Additional measurements included intranasal pressures and PCO₂, closing pressures (Pcrit), and awake lung volumes in different body positions. In 19/20 patients who slept with the device, RDI was significantly reduced with the nasal valve device compared to the diagnostic NPSG (27 ± 29/h vs 49 ± 28/h), with 50% of patients having an acceptable therapeutic response. Among demographic, lung volume, or diagnostic NPSG measures or markers of collapsibility, no significant predictors of therapeutic response were found. There was a suggestion that patients with position-dependent SDB (supine RDI > lateral RDI) were more likely to have an acceptable therapeutic response to the device. Successful elimination of SDB was associated with generation and maintenance of an elevated end expiratory pressure. No single definitive mechanism of action was elucidated. The present study shows that the nasal valve device can alter SDB across the full spectrum of SDB severity. There was a suggestion that subjects with positional or milder SDB in the lateral position were those most likely to respond.