Centimeters Of Water Research Articles

Mechanical ventilation guided by driving pressure optimizes local pulmonary biomechanics in an ovine model.

Mechanical ventilation exposes the lung to injurious stresses and strains that can negatively affect clinical outcomes in acute respiratory distress syndrome or cause pulmonary complications after general anesthesia. Excess global lung strain, estimated as increased respiratory system driving pressure, is associated with mortality related to mechanical ventilation. The role of small-dimension biomechanical factors underlying this association and their spatial heterogeneity within the lung are currently unknown. Using four-dimensional computed tomography with a voxel resolution of 2.4 cubic millimeters and a multiresolution convolutional neural network for whole-lung image segmentation, we dynamically measured voxel-wise lung inflation and tidal parenchymal strains. Healthy or injured ovine lungs were evaluated as the mechanical ventilation positive end-expiratory pressure (PEEP) was titrated from 20 to 2 centimeters of water. The PEEP of minimal driving pressure (PEEPDP) optimized local lung biomechanics. We observed a greater rate of change in nonaerated lung mass with respect to PEEP below PEEPDP compared with PEEP values above this threshold. PEEPDP similarly characterized a breaking point in the relationships between PEEP and SD of local tidal parenchymal strain, the 95th percentile of local strains, and the magnitude of tidal overdistension. These findings advance the understanding of lung collapse, tidal overdistension, and strain heterogeneity as local triggers of ventilator-induced lung injury in large-animal lungs similar to those of humans and could inform the clinical management of mechanical ventilation to improve local lung biomechanics.

Positive end-expiratory pressure and postoperative complications in patients with obesity: a review and meta-analysis.

In patients with obesity, use of positive end-expiratory pressure (PEEP) > 5 cm H2 O (centimeters of water) has been shown to prevent intraoperative atelectasis. This study compares the rate of postoperative pulmonary complications (PPCs) associated with PEEP > 5 cm H2 O and PEEP ≤ 5 cm H2 O in patients with obesity who underwent surgery under general anesthesia with mechanical ventilation. This study searched Medline, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) using the terms "PEEP," "anesthesia," and "ventilation." Cochrane ReviewManager (RevMan) version 5 was used for data analysis. The primary outcome was a composite of PPCs, including atelectasis, pneumonia, pneumothorax, and acute respiratory failure. The initial search identified 903 titles and abstracts, and 4 randomized controlled trials were included for analysis. We included a total of 2116 participants from four randomized controlled trials that compared PEEP ≤ 5 cm H2 O with PEEP > 5 cm H2 O in adult patients with obesity. There was no statistically significant difference in PPCs between the PEEP ≤ 5 cm H2 O and PEEP > 5 cm H2 O groups (risk ratio=2.21, 95% CI: 0.41-11.83; p=0.35). However, a significant heterogeneity was found within included studies (I2 = 53%). It is unclear whether PEEP > 5 cm H2 O improves the postoperative clinical outcome in patients with obesity, which is in contrast to previously established evidence that it reduces atelectasis in patients with obesity.

Comparison of Normal Saline and Alkalinized 2% Lignocaine to Reduce Emergence Phenomenon and Post-Intubation Morbidities: A Prospective, Double-Blind, Randomized Study.

Endotracheal intubation for airway management in general anesthesia is associated with post-intubation morbidities due to tracheal mucosa injury caused by endotracheal tube (ETT) cuff. Nitrous oxide (N2O) diffuses into tracheal tube cuffs filled with air. The rate of diffusion of N2O through the membrane is proportional to its concentration gradient. High-volume low-pressure cuffs expand with only a slight increase in pressure until fully inflated. At this point, owing to the inelasticity of the material, the cuff pressure rises rapidly. This increased pressure can damage the tracheal mucosa. This phenomenon can be avoided, if we inflate the cuff with either a liquid or a gas mixture identical to the inspired gas and monitor the cuff pressure and volume at regular intervals. When lignocaine is used to inflate the ETT cuff, it diffuses to the underlying tracheal mucosa. Thus reducing local irritation and inflammation of the airway through its local anesthetic action. Alkalinization of lignocaine increases its rate of diffusion across the ETT cuff. It also reduces the dose of local anesthetic required to achieve the desired result. We sought to determine the benefits of filling the ETT cuff with alkalinized lignocaine 2% over normal saline, to prevent ETT-induced emergence phenomenon and reduce the incidence of post-intubation morbidities like sore throat, hoarseness, and nausea. This prospective, randomized, double-blind, and comparative study was done at a multispecialty hospital. A total of 120 individuals ofAmerican Society of Anesthesiologists (ASA) physical status 1 and 2, posted for surgery under general anesthesia, were randomly selected and divided into two groups: alkalinized 2% lignocaine group (group L) and normal saline group (group S). After induction of general anesthesia, the airway was secured with appropriate-sized ETT. The ETT cuff was inflated with either of the study media. Continuous cuff pressure monitoring was done to keep cuff pressure below 30 centimeters of water (cm of H2O), at all times. At extubation, the response was evaluated in terms of percentage change in heart rate (HR) and blood pressure from baseline, coughing, bucking, and restlessness. All the surgeries lasted more than two hours. Post-operatively, the patients were evaluated for sore throat and hoarseness, at regular intervals of up to 24 hours. ETT cuff pressure was initially less in group S, which rose to a significantly higher level at extubation, compared to group L (p <0.001). At extubation, there was a significant increase in HR and systolic blood pressure (SBP) from baseline, in group S than in group L (p <0.001 and p=0.001, respectively).The incidence of cough and restlessness was less in group L, compared to group S (p<0.001 and p=0.002, respectively). Mean extubation time and emergence time was more in group S than in group L (p<0.001). Post-operatively, the incidence and severity of sore throat were significantly higher in group S than in group L (p<0.001). Meanwhile, the incidence of hoarseness and nausea was comparable in the two groups. Continuous ETT cuff pressure monitoring helps to keep cuff pressure below tracheal mucosa capillary occlusion pressure. Filling the ETT cuff with alkalinized lignocaine further reduces extubation response and post-intubation morbidities.

Effect on Cuff Pressure of Various Endotracheal Tube Cuff Inflation Methods

Objective: To compare mean endotracheal tube cuff pressures generated using two endotracheal tube cuff inflation methods;just-Seal versus Stethoscope-Guided in patients undergoing elective surgery under general Anaesthesia.&#x0D; Study Design: Quasi-experimental study.&#x0D; Place and Duration of Study: Anesthesia Department, Combined Military Hospital, Rawalpindi Pakistan, from Jan to Jul 2021.&#x0D; Methodology: A total of 100 patients undergoing elective surgery under general endotracheal tube anaesthesia between 18–60 years of age of either gender were included. Patients were equally allocated (n=50 each) to two Groups, A (Just Seal Group) and B (Stethoscope Guided Group). In the Group-A method, the air was injected until no air leak could be heard. The pressure was measured using a “Portex cuff pressure manometer”. In the Group-B method, a stethoscope bell was placed on the thyroid lamina, and harsh breath sounds were auscultated during ventilation. Cuff was inflated till the sounds changed to smooth sounds. The pressure was measured and then noted down. &#x0D; Results: Among 100 patients, 39 % were males, and 61 % were females. The mean endotracheal cuff pressure in Group-A was 39.90±3.19 centimetres of water and 28.42±3.52 centimetres of water, with Group-B (p-value of 0.001).&#x0D; Conclusion: Post-intubation cuff pressure measured in patients undergoing elective surgery under general anaesthesia of the just seal group is higher than that in the stethoscope-guided group.&#x0D; Keywords: Cuff pressure, Stethoscope-guided, Tracheal intubation.&#x0D;

Abstract 12990: The Association of Modifiable Mechanical Ventilation Settings, Blood Gas Changes and Survival After Extracorporeal Cardiopulmonary Resuscitation

Introduction: Gas exchange during ECMO can occur independent of the lungs through ECMO, enabling a wider range of ventilator settings and blood gas values. Yet it is not known if potentially modifiable mechanical ventilation parameters or blood gas values are associated with survival for patients who receive ECPR. Hypothesis: To determine associations between ventilation parameters, blood gas values, and survival. Methods: Cohort analysis among 7,488 ECPR patients ≥18yrs of age from the Extracorporeal Life Support Organization (ELSO) Registry from 2008 - 2019. We examined the association between mechanical ventilation parameters on-ECMO with case-mix adjusted hospital survival. We used generalized estimating equation logistic regression, accounting for center level variation. Results: Case-mix adjusted patient-level mechanical ventilation parameters and blood gas values on-ECMO varied across individual hospitals, including arterial pressure of oxygen (PaO2) and carbon dioxide (PaCO2), and changes in these values from pre-ECMO to on-ECMO. Increasing absolute on-ECMO PaO2 (OR 0.88 [95% CI 0.86, 0.9]; p&lt;0.001), and relative increases in PaO2 from pre- to on-ECMO (OR 0.91 [0.89,0.93]; p&lt;0.001) were both associated with decreased survival. Relative increases in pre- to on-ECMO PaCO2 (OR 1.31 [1.14, 1.1.54]; p&lt;0.001) were associated with improved survival. Decreasing peak inspiratory pressure (OR 0.77, per 5 centimeters of water (cmH2O) [0.72, 0.81]; p&lt;0.001) and fraction of inspired oxygen (OR 0.94, per 5% [0.92, 0.96]; p&lt;0.001) were both associated with improved survival. Conclusions: Mechanical ventilation parameters of ECPR patients varies across hospitals. Potentially modifiable parameters and blood gas values are associated with survival and should be the focus of future research.

The Study of Field Equivalence Determined by the Modeled Percentage Depth Dose in Electron Beam Radiation Therapy.

Introduction This study presents an empirical method to model the curve of electron beam percent depth dose (PDD) by using the primary-tail function in electron beam radiation therapy. The modeling parameters N and n can be used to predict the minimal side length when the field size is reduced below that required for lateral scatter equilibrium (LSE) in electron radiation therapy. Methods and Materials The electrons' PDD curves were modeled by the primary-tail function in this study. The primary function included the exponential function and the main parameters of N and μ, while the tail function was composed of a sigmoid function with the main parameter of n. The PDD of five electron energies was modeled by the primary and tail function by adjusting the parameters of N, μ, and n. The R50 and Rp can be derived from the modeled straight line of 80% to 20% region of PDD. The same electron energy with different cone sizes was also modeled by the primary-tail function. The stopping power of different electron energies in different depths can also be derived from the parameters N, μ, and n. Results The main parameters N and n increase but μ decreases in the primary-tail function for characterizing the electron beam PDD when the electron energy increased. The relationship of parameter n, N, and ln(−μ) with electron energy are n = 31.667E0 − 88, N = 0.9975E0 − 2.8535, and ln(−μ) = −0.1355E0 − 6.0986, respectively. Percent depth dose was derived from the percent reading curve by multiplying the stopping power relevant to the depth in water at a certain electron energy. The stopping power of different electron energies can be derived from n and N with the following equation: stopping power = (−0.042ln(NE0) + 1.072)e(−nE0 · 5 · 10−5 + 0.0381)·x, where x is the depth in water. The lateral scatter equivalence (LSE) of the clinical electron beam can be described by the parameters E0, n, and N in the equation of Seq = (nE0 − NE0)0.288/(E0/nE0)0.0195. The LSE was compared with the root mean square scatter angular distribution method and shows the agreement of depth dose distributions within ±2%. Conclusions The PDD of the electron beam at different energies and cone sizes can be modeled with an empirical model to deal with what is the minimal field size without changing the percent depth dose when approximate LSE is given in centimeters of water.

Intra-abdominal Pressure and Pelvic Floor Health: Should We Be Thinking About This Relationship Differently?

Intra-abdominal pressure (IAP) increases during physical activity. Activities with high IAP are often restricted for women because of potential pelvic floor overloading. Researchers categorize high IAP activities using absolute values (in centimeters of water). Although essential for descriptive purposes, absolute IAP may not be ideal for individualized exercise recommendations. For oxygen consumption, a well-established measure of fitness, exercise scientists use a percentage of the maximal value observed during exercise to create relative exercise intensity prescriptions for an individual. Relative exercise intensity correlates inversely to the maximal value observed. We explore whether this approach and response pattern extend to IAP observed during exercise. Fifty-five women completed 16 exercises while wearing a vaginal sensor to measure IAP. The highest mean IAP occurred during seated Valsalva/strain (IAPSTRAIN). We calculated relative IAP (in percent) for each participant by dividing the maximal IAP during each exercise by IAPSTRAIN. We examined relationships between relative IAP and IAPSTRAIN for each activity using Pearson r correlations. Mean age was 30.4 ± 9.4 years, and body mass index was 22.4 ± 2.6 kg/m. For most women, IAP was greater during strain than during exercises. Relative IAPs negatively correlated with IAPSTRAIN. Excluding one exercise because of small sample sizes, r for all others ranged from -0.35 to -0.80, all statistically significant. The relative IAP responses to many exercises exhibit an inverse relationship to the highest IAP values during strain, consistent with other variables measured during exercise. Relative IAP may provide an alternative to absolute IAP in understanding IAP's effect on pelvic floor health.

Efficacy of Laryngeal Tube versus Bag Mask Ventilation by Inexperienced Providers.

IntroductionBag mask ventilation (BMV) and extraglottic devices (EGDs) are two common methods of providing rescue ventilation. BMV can be difficult to perform effectively, especially for inexperienced providers and in patients with difficult airway characteristics. There is some evidence that the laryngeal tube (LT) can be successfully placed by inexperienced providers to provide effective ventilation. However, it is unclear whether ventilation provided by LT is superior to that of BMV, especially in the hands of inexperienced airway providers. Therefore, we aimed to compare ventilation efficacy of inexperienced airway providers with BMV versus LT by primarily measuring tidal volumes and secondarily measuring peak pressures on a simulated model.MethodsWe performed a crossover study first year emergency medicine residents and third and fourth year medical students. After a brief instructional video followed by hands on practice, participants performed both techniques in random order on a simulated model for two minutes each. Returned tidal volumes and peak pressures were measured.ResultsTwenty participants were enrolled and 1200 breaths were measured, 600 per technique. The median ventilation volumes were 194 milliliters (mL) for BMV, and 387 mL for the laryngeal tube, with a median absolute difference of 170 mL (95% confidence interval [CI] 157–182 mL) (mean difference 148 mL [95% CI, 138–158 mL], p<0.001). The median ventilation peak pressures were 23 centimeters of water (cm H2O) for BMV, and 30 cm H2O for the laryngeal tube, with a median absolute difference of 7 cm H2O (95% CI, 6–8 cm H2O) (mean difference 8 cm H2O [95% CI, 7–9 cm H2O], p<0.001).ConclusionInexperienced airway providers were able to provide higher ventilation volumes and peak pressures with the LT when compared to BMV in a manikin model. Inexperienced providers should consider using an LT when providing rescue ventilations in obtunded or hypoventilating patients without intact airway reflexes. Further study is required to understand whether these findings are generalizable to live patients.

Truth or Myth: Intra-abdominal Pressure Increases in the Lithotomy Position

To determine if there were differences in intra-abdominal pressure (IAP) in the supine, low lithotomy, and high lithotomy positions. Prospective cohort study. University medical center. Twenty-nine women undergoing surgery for prolapse or stress incontinence. Relevant medical history, including the pelvic organ prolapse quantification stage, body mass index, and airway grade (Mallampati score), was abstracted from patients' medical charts. IAP was measured in centimeters of water (cmH2O) on the day of their surgery before induction of general or intravenous anesthesia using a T-doc air charged urodynamic catheter (Laborie Aquarius; Ontario, Canada) placed in a patient's vagina (for patients with incontinence) or rectum (for patients with prolapse). IAP was measured in 3 positions: supine (legs at 0°), low lithotomy (legs in Yellowfin stirrups at 45°; Allen Medical, Acton, MA), and high lithotomy (legs at 90°). The means ± SDs IAP for the groups were as follows: in the supine position, 18.6 cmH2O ± 7.6; low lithotomy, 17.7 cmH2O ± 6.6; and high lithotomy, 17.1 cmH2O ± 6.3. In the same women, there was a significant decrease in IAP from the supine to high lithotomy positions, with a mean difference of 1.4 cmH2O ± 3.7, p = .05. Similarly, there was a significant, though smaller, decrease in mean IAP when moving from the supine to low lithotomy positions in these same women (mean decrease of 0.9 cmH2O ± 1.5, p = .004). Neither change is clinically significant based on previous research that suggests 5 cmH2O is a clinically significant change. Placing patients' legs in a low or high lithotomy position does not result in a clinically significant increase in IAP. Therefore, surgeons and anesthesiologists can consider positioning patients' lower extremities in stirrups while patients are awake to minimize discomfort and possibly reduce the risk of nerve injuries.

Mercury vs. Water: An Analysis of Multi-Institutional Survey Data Assessing Intracranial Pressure Unit of Measure Awareness

Intracranial pressure (ICP) reporting impacts neurosurgical care. Millimeters of mercury (mmHg) and centimeters of water (cmH2O) are both used to report ICP in clinical practice and the literature. In this study, we investigated ICP unit of measure awareness in the neurosurgical community. A survey was conducted at four US academic neurosurgery departments asking the following questions: What is your threshold for a concerning ICP? How many minutes is that ICP sustained for you to be concerned? What unit are you implying when you state that ICP? What unit of measure is an ICP reported on the monitor when transduced? When setting an external ventricular drain Becker bag level, what unit of measure do you set it to? Do you ever manually check an ICP based on a column of cerebrospinal fluid? How many cmH2O is 20mmHg? An ICP of 20 and sustained for five minutes were the two most common answers. Some 71% of residents and 34% of attendings reported using cmH2O as the unit of measure; 18% of residents and 24% of attendings implied different units when discussing ICP than the unit they thought was transduced; and 53% of residents and 34% of attendings did not know the transduced ICP unit of measure reported in their intensive care unit. Variability and discrepancies regarding the ICP unit of measure exist in academic neurosurgery departments. Clinicians should familiarize themselves with their hospital's practices. Institutions and all of medicine may consider standardizing the ICP unit of measure, using mmHg as a universal nomenclature.

Differences in Respiratory Muscle Strength Measures in Well-Nourished and Malnourished Hospitalized Patients

BackgroundObjective indicators of nutritional status are essential for accurate identification of malnutrition. Previous research has indicated an association between measures of respiratory muscle strength (RMS) and nutritional status. Measurement of RMS—including maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and sniff nasal inspiratory pressure (SNIP)—may provide evidence to support the assessment of nutritional status in hospitalized patients. ObjectiveThe purpose of this study was to determine whether there was a difference in MIP, MEP, and SNIP between well-nourished and malnourished hospitalized patients. DesignA cross-sectional study was conducted. Participants/settingPatients were screened for eligibility criteria on admission by means of electronic medical records in general medical or surgical units at a tertiary care hospital in Chicago, IL, from January 2016 to January 2017. A total of 140 patients were included for analysis. Main outcomes measuredThe primary outcome was detection of differences in measures of RMS between malnourished and well-nourished hospitalized patients. Nutritional status was assessed using subjective global assessment and Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition (Academy/ASPEN) criteria recommended to identify malnutrition. The MIP, MEP, and SNIP measures were obtained and reported as absolute values (expressed in centimeters of water) and percent of predicted values. Statistical analysisIndependent t tests or Mann-Whitney U tests were used to determine differences in RMS measures between patients assessed as well nourished and those assessed as malnourished, depending on normality. ResultsCompared with well-nourished patients, malnourished patients identified by subjective global assessment criteria had significantly lower absolute SNIP (73.7±28.7 vs 59.5±27.1 cm H2O, P=0.004) and percent of predicted SNIP (78.6%±26.3% vs 64.8%± 30.0% predicted, P=0.006). Similarly, compared with well-nourished patients when Academy/ASPEN guidelines were used, malnourished individuals had significantly lower absolute SNIP (76.5±28.6 vs 58.3±26.3 cm H2O, P<0.001), percent of predicted SNIP (81.4%±26.4% vs 63.5%±28.7% predicted, P<0.001), absolute MIP (83.5±34.6 vs 71.1±33.6 cm H2O, P=0.05), and absolute MEP (108.7±36.6 vs 94.2±39.9 cm H2O, P=0.04). ConclusionDifferences in RMS between well-nourished and malnourished patients were observed when SNIP measures were used. However, there were no differences in MIP and MEP measures. Further research is needed to build on the findings from this study.

Combined respiratory training in an individual with C9orf72 amyotrophic lateral sclerosis.

This case study examined the impact of a respiratory strength training program targeting inspiratory and expiratory musculature in an individual with C9orf72 amyotrophic lateral sclerosis (ALS). The individual tolerated 24 months of respiratory training completed at home, 50 repetitions per day, and 5 days per week. Significant increases in maximum inspiratory pressure (from 71 to 134 centimeters of water), maximum expiratory pressure (from 108 to 197 centimeters of water) and peak cough flow (from 331 to 655 Liters per minute) were noted and forced vital capacity remained unchanged. A moderate intensity respiratory strength training program applied early in the disease progression improved function in this C9orf72 ALS individual.

Prone Positioning in Moderate-Severe ARDS: Preliminary Data From a Community-Based Teaching Hospital

SESSION TITLE: ARDS and Acute Lung Injury SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, November 1, 2017 at 01:30 PM - 02:30 PM PURPOSE: In 2013, after publication of a randomized controlled trial that demonstrated a mortality benefit to ventilation in the prone versus supine position in ARDS, critical care physicians at our institution began to implement this approach. Prior to this, we rarely used prone positioning in our medical ICU and we did not know if the mortality and low complication rate observed in the trial, at centers with >5 years of experience with proning, could be replicated at our institution or what impact this intervention would have on functional outcomes. METHODS: We conducted a retrospective cohort study of all proned patients from June 2013 to November 2014 at Christiana Care Health System. Patients were identified by respiratory care data. We collected demographic data, pre- and post- proning data, respiratory mechanics, diagnoses, complications, and outcomes including mortality, length of stay, and distance walked prior to discharge. Descriptive statistics are used to describe our cohort. RESULTS: Thirty seven patients underwent ventilation in the prone position. Of these, 23 (62%) survived to hospital discharge. The mean age was 56.3 years and 60% were male. The mean sequential organ failure score was 8.6. Immediately prior to proning, the mean positive end expiratory pressure was 14, mean driving pressure was 14 centimeters of water, mean partial pressure of arterial oxygen to fraction of inspired oxygen was 100 and mean tidal volume was 5.5 ml/kg of predicted body weight. Patients were proned for a mean of 41 hours. One patient received extracorporal membrane oxygenation, 31 (84%) received neuromuscular blocking agents, 6 (16.2%) received inhaled nitric oxide, and 21(57%) received steroids. None developed ventilator associated pneumonia or had cardiac arrests while proned. In terms of complications, 6 patients had dependent edema, 7 had dislodged devices, and 2 had skin breakdown. The mean hospital and ICU length of stays were 23 and 14, respectively. A total of 23 patients were able to ambulate a mean of 138 feet prior to hospital discharge. CONCLUSIONS: Hospital mortality was higher in this cohort than the 28-day mortality reported in the trial. However, serious complications from prone positioning were uncommon. The higher mortality rate could be due to differences in clinical care including use of adjuvent therapies or differences in patient selection. Additionally, during our study period in December 2013, we implemented a protocol for ventilation in the prone position. We plan additional data collection and analysis to determine is outcomes differ before and after protocol implementation.All of the survivors were ambulatory prior to hospital discharge. CLINICAL IMPLICATIONS: It is feasible to implement a proning protocol at a community hospital with limited prior experience; however, close monitoring of outcomes is needed to determine whether expected benefits are achieved. DISCLOSURE: The following authors have nothing to disclose: Fahmida Khan, Christa Fistler, Jefferson Mixell, Patricia McGraw, Michael Vest No Product/Research Disclosure Information

SU‐F‐T‐74: Experimental Validation of Monaco Electron Monte Carlo Dose Calculation for Small Fields

Purpose:To verify experimentally the accuracy of Monaco (Elekta) electron Monte Carlo (eMC) algorithm to calculate small field size depth doses, monitor units and isodose distributions.Methods:Beam modeling of eMC algorithm was performed for electron energies of 6, 9, 12 15 and 18 Mev for a Elekta Infinity Linac and all available (6, 10, 14 20 and 25 cone) applicator sizes. Electron cutouts of incrementally smaller field sizes (20, 40, 60 and 80% blocked from open cone) were fabricated. Dose calculation was performed using a grid size smaller than one‐tenth of the R80–20 electron distal falloff distance and number of particle histories was set at 500,000 per cm2. Percent depth dose scans and beam profiles at dmax, d90 and d80 depths were measured for each cutout and energy with Wellhoffer (IBA) Blue Phantom2 scanning system and compared against eMC calculated doses.Results:The measured dose and output factors of incrementally reduced cutout sizes (to 3cm diameter) agreed with eMC calculated doses within ± 2.5%. The profile comparisons at dmax, d90 and d80 depths and percent depth doses at reduced field sizes agreed within 2.5% or 2mm.Conclusion:Our results indicate that the Monaco eMC algorithm can accurately predict depth doses, isodose distributions, and monitor units in homogeneous water phantom for field sizes as small as 3.0 cm diameter for energies in the 6 to 18 MeV range at 100 cm SSD. Consequently, the old rule of thumb to approximate limiting cutout size for an electron field determined by the lateral scatter equilibrium (E (MeV)/2.5 in centimeters of water) does not apply to Monaco eMC algorithm.

Comparação entre a pressão inspiratória máxima aferida pelo manovacuômetro digital e pelo dispositivo eletrônico de treinamento muscular inspiratório

Aims: To compare maximum inspiratory pressure (MIP) measured by a digital manometer and by an inspiratory muscle training (IMT) device and to evaluate hemodynamic changes after measurements.Methods: The sample included male and female individuals older than 18 years admitted to an intensive care unit who were hemodynamically stable, not being treated with vasoactive drugs or sedated, intubated or tracheostomized, and who were in the process of being weaned from mechanical ventilation. MIP was measured by both devices on three different occasions, with an occlusion time of 20 seconds and a 5-minute interval between measurements. The following parameters were assessed: respiratory rate, mean arterial pressure, and respiratory rate before and after each measurement by each device. The statistical analysis was made in the Statistical Analysis System and the R Project for Statistical Computing V. 3.1.2 softwares, using the ANOVA and the Wilcoxon tests.Results: Fifty-eight patients were included in the study. The mean value obtained for MIP was -46.22 centimeters of water (cmH2O) in the digital manometer and -13.15 cmH2O (p<0.001) in the IMT device. Heart rate showed a significant increase (p<0.0001) both before and after all measurements in both devices. Mean arterial pressure showed a statistically significant difference only before and after the first measurement by the digital manometer and before and after the second measurement by the IMT device (p<0.001). The respiratory rate oscillated significantly before and after the three measurements by both devices (p<0.0001). The hemodynamic parameters remained within reference values after MIP measurements.Conclusions: The digital manometer recorded a higher MIP than that measured by the IMT device. The hemodynamic parameter values oscillated in both devices, but they remained within the normal range and were not clinically significant.

Predictive Time Series Analysis Linking Bengal Cholera with Terrestrial Water Storage Measured from Gravity Recovery and Climate Experiment Sensors.

Outbreaks of diarrheal diseases, including cholera, are related to floods and droughts in regions where water and sanitation infrastructure are inadequate or insufficient. However, availability of data on water scarcity and abundance in transnational basins, are a prerequisite for developing cholera forecasting systems. With more than a decade of terrestrial water storage (TWS) data from the Gravity Recovery and Climate Experiment, conditions favorable for predicting cholera occurrence may now be determined. We explored lead-lag relationships between TWS in the Ganges-Brahmaputra-Meghna basin and endemic cholera in Bangladesh. Since bimodal seasonal peaks in cholera in Bangladesh occur during spring and autumn seasons, two separate logistical models between TWS and disease time series (2002-2010) were developed. TWS representing water availability showed an asymmetrical, strong association with cholera prevalence in the spring (τ = -0.53; P < 0.001) and autumn (τ = 0.45; P < 0.001) up to 6 months in advance. One unit (centimeter of water) decrease in water availability in the basin increased odds of above normal cholera by 24% (confidence interval [CI] = 20-31%; P < 0.05) in the spring, while an increase in regional water by 1 unit, through floods, increased odds of above average cholera in the autumn by 29% (CI = 22-33%; P < 0.05).

An estimation of mechanical stress on alveolar walls during repetitive alveolar reopening and closure

Alveolar overdistension and mechanical stresses generated by repetitive opening and closing of small airways and alveoli have been widely recognized as two primary mechanistic factors that may contribute to the development of ventilator-induced lung injury. A long-duration exposure of alveolar epithelial cells to even small, shear stresses could lead to the changes in cytoskeleton and the production of inflammatory mediators. In this paper, we have made an attempt to estimate in situ the magnitudes of mechanical stresses exerted on the alveolar walls during repetitive alveolar reopening by using a tape-peeling model of McEwan and Taylor (35). To this end, we first speculate the possible ranges of capillary number (Ca) ≡ μU/γ (a dimensionless combination of surface tension γ, fluid viscosity μ, and alveolar opening velocity U) during in vivo alveolar opening. Subsequent calculations show that increasing respiratory rate or inflation rate serves to increase the values of mechanical stresses. For a normal lung, the predicted maximum shear stresses are <15 dyn/cm(2) at all respiratory rates, whereas for a lung with elevated surface tension or viscosity, the maximum shear stress will notably increase, even at a slow respiratory rate. Similarly, the increased pressure gradients in the case of elevated surface or viscosity may lead to a pressure drop >300 dyn/cm(2) across a cell, possibly inducing epithelial hydraulic cracks. In addition, we have conceived of a geometrical model of alveolar opening to make a prediction of the positive end-expiratory pressure (PEEP) required to splint open a collapsed alveolus, which as shown by our results, covers a wide range of pressures, from several centimeters to dozens of centimeters of water, strongly depending on the underlying pulmonary conditions. The establishment of adequate regional ventilation-to-perfusion ratios may prevent recruited alveoli from reabsorption atelectasis and accordingly, reduce the required levels of PEEP. The present study and several recent animal experiments likewise suggest that a lung-protective ventilation strategy should not only include small tidal volume and plateau pressure limitations but also consider such cofactors as ventilation frequency and inflation rate.

Effects of Soil Water Content in Four Soybean Genotypes in Different Environments in the Central Area of the Argentine Pampean Region

In the Pampa Region there is limited information about the dynamics of soil water and the consumption rate of different soybean genotypes. In the Pampa Central Area, the first 15 cm of soil concentrates 80% of the soybean plant’s root weight and over 40% of root absorbent surface. Despite the importance of extracting the first centimeters of water, the water supply in deeper zones could be very important as well. Because of this fact, the evaluation of the evolution of soil moisture was proposed: in two soil types—Typic Hapludoll and Entic Hapludoll; in different climatic years; in four soybean genotypes—NA 3731RG, NA 4209RG, NA 4613RG and NA 5009RG; in their effect on crop yield. In each of these environments, soil water content measurements were made in the first 100 cm with a TDR (Total Dormain Reflectometry) drill, over varietal performance tests with three replications per genotype in each location. In all evaluated situations, a significant effect on interaction genotype x soil depth, genotype x crop emergence days and crop emergence days x soil depth was established. Also a fast development of roots was observed, having found active roots for the absorption of water within the first meter of depth 24 days after crop emergence. A difference in difference of radical elongation rate among varieties was also observed; because of the low water availability in vegetative phases with similar soil humidity distribution, the genotype NA 5009 RG had reached 20 cm more of radical activity faster than NA 4613RG. The highest crop yields were not associated to higher water content in soil during the whole cycle. Highest crop yields were associated to a combination of genotype, water availability between 50% of useful water during the whole vegetative cycle and the beginning of the flowering period, and high water availability in the first centimeters during reproductive phases. Under less water availability, the genotype with higher speed of radical deepening reached the highest yields.

Respiratory muscle training on pulmonary and swallowing function in patients with Huntington’s disease: a pilot randomised controlled trial

Objective: To examine the effects of 4-month of respiratory muscle training on pulmonary and swallowing function, exercise capacity and dyspnoea in manifest patients with Huntington’s disease. Design: A pilot randomised controlled trial. Setting: Home based training program. Participants: Eighteen manifest Huntington’s disease patients with a positive genetic test and clinically verified disease expression, were randomly assigned to control group (n=9) and training group (n=9). Intervention: Both groups received home-based inspiratory (5 sets of 5 repetitions) and expiratory (5 sets of 5 repetitions) muscle training 6 times a week for 4 months. The control group used a fixed resistance of 9 centimeters of water, and the training group used a progressively increased resistance from 30% to 75% of each patient’s maximum respiratory pressure. Main measures: Spirometric indices, maximum inspiratory pressure, maximum expiratory pressure, six minutes walk test, dyspnoea, water-swallowing test and swallow quality of life questionnaire were assessed before, at 2 and 4 months after training. Results: The magnitude of increases in maximum inspiratory (d=2.9) and expiratory pressures (d=1.5), forced vital capacity (d=0.8), forced expiratory volume in 1 second (d=0.9) and peak expiratory flow (d=0.8) was substantially greater for the training group in comparison to the control group. Changes in swallowing function, dyspnoea and exercise capacity were small (d≤0.5) for both groups without substantial differences between groups. Conclusions: A home-based respiratory muscle training program appeared to be beneficial to improve pulmonary function in manifest Huntington’s disease patients but provided small effects on swallowing function, dyspnoea and exercise capacity.

Braking formula for electrons of relativistic speed

From the theory of Moller [Moller, Chr. 1931. Uber den Stos zweier Teilchen unter Berucksichtigung der Retardation der Krafte. Zeitschrift f. Phys. 70: 786–795] the energy loss of electrons with relativistic speeds passing through matter is derived. The energy loss per centimeter of distance reaches a minimum at about 96% of the speed of light and increases again at higher speeds; for electrons of several billion Volt it is about 4 million Volt per centimeter of water. A table of the theoretical energy loss for electrons and protons of various speeds is given.