Vehicle cabin air quality: influence of air recirculation on energy use, particles, and CO2.

In this study, simulations were performed to investigate the influence of different vehicle climate ventilation strategies, mainly the air recirculation (REC) degree, on the cabin air quality and climate system power. The focus of air quality is on the cabin particle concentrations including PM2.5 (particles of aerodynamic diameter less than 2.5 µm), UFP (ultrafine particles of aerodynamic diameter less than 100 nm), and cabin CO2 concentration. Three outside climates (cold, intermediate, and warm) and three outside particle concentrations are studied. The studied vehicle originally shows possibilities to meet WHO PM2.5 guideline of 15 µg/m3 with a new filter. The aged filter have reduced performance, especially when outside concentration is high. Increased REC shows advantages in all the three climates in reducing particles and climate power for the studied vehicle. Application of 70% REC (70% of ventilation air is recirculated air) on average lowers PM2.5 by 55% and 39% for a new and aged filter, respectively. 70% REC with a new filter reduces cabin PM2.5 below guideline of 15 µg/m3 in all conditions. The reduction of UFP counts results are generally similar to that of PM2.5. Increased REC also lessens the average climate system power by up to 27% on average. When REC is increased, the cabin CO2 concentration arises accordingly, and the magnitude is relevant to the passengers. In all studied conditions with 1 passenger, 70% REC does not increase CO2 above the common guideline of 1000 ppm. 70% REC is not recommended with more than 1 passengers in cold and intermediate climate and 2 passengers in warm climate. Besides, to avoid the potential windscreen fog risk in cold climate, REC should be avoided when passengers are more than 3. Except for constant REC values, a sample study investigates a dynamic control of the REC. It shows the possibility of continuously optimizing REC to reduce the climate power and particles, while maintaining the CO2 concentration below 1000 ppm. In warm climate with 1 passenger boarded, the average optimized REC is 90%, which in comparison with base case lead to 44% PM2.5 reduction and 12% climate power reduction.

Size-resolved simulation of particulate matters and CO2 concentration in passenger vehicle cabins.

The main aim of this study is to develop a mathematical size-dependent vehicle cabin model for particulate matter concentration including PM2.5 (particles of aerodynamic diameter less than 2.5 µm) and UFPs (ultrafine particles of aerodynamic diameter less than 100 nm), as well as CO2 concentration. The ventilation airflow rate and cabin volume parameters are defined from a previously developed vehicle model for climate system design. The model simulates different filter statuses, application of pre-ionization, different airflow rates and recirculation degrees. Both particle mass and count concentration within 10-2530 nm are simulated. Parameters in the model are defined from either available component test data (for example filter efficiencies) or assumptions from corresponding studies (for example particle infiltration and deposition rates). To validate the model, road measurements of particle and CO2 concentrations outside two vehicles were used as model inputs. The simulated inside PM2.5, UFP and CO2 concentration were compared with the inside measurements. Generally, the simulation agrees well with measured data (Person's r 0.89-0.92), and the simulation of aged filter with ionization is showing higher deviation than others. The simulation using medium airflows agrees better than the simulation using other airflows, both lower and higher. The reason for this may be that the filter efficiency data used in the model were obtained at airflows close to the medium airflow. When all size bins are compared, the sizes of 100-300 nm were slightly overestimated. The results indicated that among others, expanded filter efficiency data as a function of filter ageing and airflow rate would possibly enhance the simulation accuracy. An initial application sample study on recirculation degrees presents the model's possible application in developing advanced climate control strategies.

PM2.5 and ultrafine particles in passenger car cabins in Sweden and northern China-the influence of filter age and pre-ionization.

The main aim of the study was to evaluate the influence of filter status (new and aged), pre-ionization, on the particle filtration in modern passenger cars. Measurements of in-cabin and outside PM2.5 (dp < 2.5 µm) concentration and UFP (ultrafine particle, dp < 100 nm) counts, to calculate I/O (indoor to outdoor) ratios, were performed. They were done at two locations, to study the influence of different outside conditions on the HVAC (heating, ventilation, and air-conditioning) system. The measurements were performed in two new cars, with similar HVAC systems and settings, using a new filter and an aged synthetic filter. Furthermore, an ionization unit was installed upstream of the filter in both cars. This enabled the study of filter status, with and without ionization, under common driving conditions. The results show that the HVAC system performances were very similar at the two locations, with average I/O ratios of 0.35-0.40 without ionization and 0.15-0.20 with ionization applied, although the outside conditions were considerably different. Furthermore, the aged filter clearly worsened the filtration ability. Considering the corresponding average PM2.5 I/O ratios in one location as an example, the average for the new filter was 0.20 and 0.60 for the aged filter. The corresponding UFP I/O ratios were 0.24 and 0.57. Other findings are that the aged filter with ionization reached a performance close to the new filter (without ionization), and that increased ventilation airflow and decreased recirculation degree, as expected, led to an increase in the I/O ratio for both particle sizes.

FKBP5 expression in human adipose tissue increases following dexamethasone exposure and is associated with insulin resistance.

OBJECTIVE: To study effects of dexamethasone on gene expression in human adipose tissue aiming to identify potential novel mechanisms for glucocorticoid-induced insulin resistance. MATERIALS/METHODS: Subcutaneous and omental adipose tissue, obtained from non-diabetic donors (10 M/15 F; age: 28-60 years; BMI: 20.7-30.6 kg/m²), was incubated with or without dexamethasone (0.003-3 µmol/L) for 24 h. Gene expression was assessed by microarray and real time-PCR and protein expression by immunoblotting. RESULTS: FKBP5 (FK506-binding protein 5) and CNR1 (cannabinoid receptor 1) were the most responsive genes to dexamethasone in both subcutaneous and omental adipose tissue (~7-fold). Dexamethasone increased FKBP5 gene and protein expression in a dose-dependent manner in both depots. The gene product, FKBP51 protein, was 10-fold higher in the omental than in the subcutaneous depot, whereas the mRNA levels were similar. Higher FKBP5 gene expression in omental adipose tissue was associated with reduced insulin effects on glucose uptake in both depots. Furthermore, FKBP5 gene expression in subcutaneous adipose tissue was positively correlated with serum insulin, HOMA-IR and subcutaneous adipocyte diameter and negatively with plasma HDL-cholesterol. FKBP5 SNPs were found to be associated with type 2 diabetes and diabetes-related phenotypes in large population-based samples. CONCLUSIONS: Dexamethasone exposure promotes expression of FKBP5 in adipose tissue, a gene that may be implicated in glucocorticoid-induced insulin resistance.

Feasibility of a combined percutaneous laparoscopic three-millimeter device.

BACKGROUND AND OBJECTIVES: Needlescopic 3-mm instruments induce minimal trauma and produce excellent cosmetic results. A combination of a 3-mm abdominal wall incision and a 5-mm instrument in the abdominal cavity would combine the beneficial features of these two different sizes. METHODS: The Percutaneous Surgical System (PSS) (Ethicon EndoSurgery, Galway, Ireland) is a new instrument consisting of a 3-mm shaft that is introduced percutaneously into the abdominal cavity. Through a 5-mm trocar, a loader with a 5-mm attachment such as a Maryland dissector is introduced. The attachment is connected to the shaft, and the loader is removed from the abdomen. The feasibility of this device was evaluated retrospectively in 3 Swedish hospitals between January and September 2012. RESULTS: Twenty-eight patients were laparoscopically operated on (cholecystectomy, gastric bypass, fundoplication, incisional hernias, and totally extraperitoneal repair for inguinal hernia) by use of 1 or 2 PSSs in each operation (47 in total). It was feasible to use the PSS in all procedures except during the totally extraperitoneal repair procedure because of the limited available preperitoneal space. Especially in laparoscopic cholecystectomies, the two lateral 5-mm trocars were easily replaced by two 3-mm PSS instruments. CONCLUSIONS: The use of the PSS is feasible in a number of laparoscopic procedures, where it can replace 5-mm trocars. Randomized controlled trials are needed to determine the future role of the PSS versus, for example, needlescopic laparoscopy.

Tensile strength after closure of mesenteric gaps in laparoscopic gastric bypass: three techniques tested in a porcine model.

BACKGROUND: Internal hernias occur frequently after laparoscopic gastric bypass. We have found no data on the relative strength of the various techniques available for closing these defects. The present study was performed to obtain such data to form a theoretical basis for clinical studies. METHODS: Six piglets were operated laparoscopically and four loops of small bowel created in each. These mesenteric gaps were closed over a distance of 40 mm using (1) running 2-0 Ethibond® suture, (2) Endo Hernia stapler, (3) fibrin glue (Tisseel®) and (4) controls, where the mesenteric surfaces were rubbed with a sponge and approximated without further intervention. After 6 weeks, the different segments of the mesentery were excised. The tensile strength was measured using continuously increased traction until the closure ruptured. The ordinary mesentery served as the control. The breaking tension and total amount of energy transferred to the tissue were registered. RESULTS: Control areas with rubbed areas developed no adhesions. Suture and staple lines contracted by 30 % in length, whereas the fibrin glued lines were even shorter. Median tensile strength was greatest for the sutured lines (14,293 mN) and stapled lines (10,798 mN). Fibrin glued lines were significantly weaker (6,780 mN, p = 0.013 and p = 0.026), but as strong as ordinary mesentery (4,165 mN). CONCLUSIONS: If ongoing controlled randomized trials show closure to be beneficial, further studies should include staples as one of the options for the closure of mesenteric defects. The role of fibrin glue needs to be further investigated.

More recurrences after hernia mesh fixation with short-term absorbable sutures: A registry study of 82 015 Lichtenstein repairs.

OBJECTIVE: To assess the effects of different mesh fixation suture materials on the risk of recurrence after Lichtenstein inguinal hernioplasty. DESIGN: Observational, population-based registry study. SETTING: Data from the nationwide Swedish Hernia Registry. PATIENTS: All 82 015 Lichtenstein inguinal hernioplasties with sutured mesh fixation in adolescents and adults (15 years or older) from January 1, 2002, to December 31, 2009, at surgical units enrolled in the Swedish Hernia Registry. INTERVENTIONS: Mesh fixation with nonabsorbable, long-term absorbable, or short-term absorbable sutures. Main Outcome Measure Relative risk (RR) for reoperation due to recurrence of a hernia in the same groin during the study period, based on cumulative reoperation rates adjusted for time and confounding variables. RESULTS: For each study group, RR was calculated with multiregression analysis. There was no significant difference in risk for reoperation after mesh fixation with standard nonabsorbable sutures (RR, 1) or with long-term absorbable sutures (RR, 1.12; 95% confidence interval, 0.81-1.55; P = .49). Short-term absorbable sutures, however, more than doubled that risk (RR, 2.23; 95% confidence interval, 1.67-2.99; P < .001). CONCLUSIONS: With regard to recurrence risk, long-term absorbable sutures are an excellent alternative to permanent sutures for mesh fixation in Lichtenstein inguinal hernioplasty. Short-term absorbable sutures entail an independent risk factor for recurrence and should therefore be avoided.

Improved outcome after laparoscopic cholecystectomy with ultrasonic dissection: a randomized multicenter trial.

BACKGROUND: In conventional laparoscopic cholecystectomy, dissection with electrocautery starts at the triangle of Calot. In a randomized single-center trial, the fundus-first method (dome down) using ultrasonic dissection was faster, involved less pain or nausea, and had a shorter postoperative sick leave. This may relate to the fundus-first method or to the ultrasonic dissection. METHODS: In a multicenter trial, 243 elective patients were randomized to conventional laparoscopic cholecystectomy using electrocautery (n = 85) or the fundus-first method using either electrocautery (n = 81) or ultrasonic dissection (n = 77). RESULTS: The fundus-first method had a shorter operating time with ultrasonic dissection (58 min) than with electrocautery (74 min; p = 0.002). The fundus-first method using ultrasonic dissection compared with electrocautery or the conventional method produced less blood loss (12 vs. 53 or 36 ml; p < 0.001) and fewer gallbladder perforations (26% vs. 46% or 49%; p = 0.005). Also, the pain and nausea scores at 4 and 6 h were lower, and the sick leave was shorter (6.1 vs. 9.4 and 9 days, respectively; p < 0.001). CONCLUSION: The fundus-first method using ultrasonic dissection is associated with less blood loss, fewer gallbladder perforations, less pain and nausea, and shorter sick leave than the conventional and fundus-first method using electrocautery. The difference seems related to the use of ultrasonic dissection.

Symptom-focused results after laparoscopic fundoplication for refractory gastroesophageal reflux disease--a prospective study.

BACKGROUND AND AIMS: Symptoms of gastroesophageal reflux disease (GERD) are common in the general population. Although the results of laparoscopic fundoplication are well documented, there have been no reports on the operative outcome in patients refractory to or with only partial response to medical therapy for GERD. PATIENTS-METHODS: Thirty-two patients with GERD, whose continuous high doses of medical treatment with proton-pump inhibitors produced no or only partial symptom relief, underwent laparoscopic Nissen fundoplication. Symptoms were evaluated with a standardized questionnaire preoperatively and 12 months after surgery. RESULTS: The complete follow-up evaluation was obtained in 30 out of the 32 patients. The main symptoms before surgery were regurgitation (93%), heartburn (60%), epigastric pain (47%), and globus sensation (47%). All patients were relieved from heartburn, vomiting, and globus sensation. Dysphagia was relieved in 75% of the patients and regurgitation in 86%. Dysphagia as a new symptom occurred in 9%. The overall morbidity rate was 16%. Patient satisfaction rate was 87%. CONCLUSION: Laparoscopic fundoplication seems to be an effective treatment for severe, drug-resistant GERD. The high patient satisfaction rate and the positive therapeutic response in 95% of patients justify this procedure in this strictly selected group of patients.

Mechanical consequences of short gastric vessel division at the time of laparoscopic total fundoplication.

Laparoscopic Nissen fundoplication is currently the most commonly practiced antireflux operation. Some adverse consequences of the operation remain in the form of mechanical side effects, labeled postfundoplication complaints, of which dysphagia and gas bloat seem to predominate. Measures have been suggested to counteract some of these and one frequently advocated has been division of the short gastric vessels to create a short-floppy wrap. The advantages of this are still debated, particularly in the long-term perspective. The aim of the present study was to evaluate the mechanical consequences of dividing all short gastric vessels at the time of a laparoscopic total fundoplication. Ninety-nine patients with chronic gastroesophageal reflux disease (GERD) were originally allocated on a random basis to have either all short gastric vessels divided or left intact at the time of a laparoscopic total fundoplication. A subsample of these patients, again selected at random, were recruited for a comprehensive manometric investigation 1 year after the operation. In this cohort, 12 patients had all short gastrics divided and in 12 patients, the wrap was done with intact vessels by use of the anterior portion of the fundus. Manometry was carried out by the use of a sleeve sensor to straddle the lower esophageal sphincter (LES), and gastric distension (750 ml air) was used to trigger transient LES relaxations (TLESR). The basal LES tone was similar in the two groups (14.2 +/- 2.4 and 18.8 +/- 4.3, mean +/- SE), respectively. Accordingly, all other relevant manometric variables were equal when the two groups were compared, except for the total number of TLESRs (triggered by gastric distension by air) that were significantly higher (p < 0.02) in patients having their short gastric vessels intact. Consequently, numerically more common cavities were recorded in the latter group. Very similar outcomes in terms of motor function of the LES and esophageal body were observed after a total fundoplication irrespective of whether a complete division of all gastric vessels had been carried out or not. However, after gastric distension with air, more TLESRs were recorded in the latter group suggesting a better maintained ability to vent air from the stomach.