Does depression influence the postoperative result of total hip arthroplasties?

Chronic pain and functional limitations caused by coxarthrosis are important factors in the onset of depression, as there are higher rates of depression in this group of patients than in the general population. Total hip arthroplasty (THA) has been shown to decrease pain and improve function in these patients, which may positively influence the patient's depressive symptoms. The objectives of the study are to evaluate the differences between patients with depression and patients without depression in the immediate postoperative period (pain and hospitalization time) and to evaluate functional outcomes one year after surgery. Therefore, we conducted a prospective cohort study in which all patients with indications for primary total hip arthroplasty during 2018 were included. Preoperatively, patients completed the PHQ-9 questionnaire, and were classified into patients with depression (if preoperative PHQ-9 > or = to 10) and patients without depression (pre PHQ-9 < to 10). During the hospital stay, postoperative pain was assessed by VAS, and the need for analgesic rescue with major opioids. One year after surgery, the PHQ-9 test was retaken, and functional outcomes were assessed. The results showed that both groups were comparable in terms of sex, age, BMI, and ASA. No differences were found in postoperative pain or hospitalization time. There were also no differences between the two groups of patients in functional outcomes one year after surgery. Therefore, we can conclude that patients with a diagnosis of depression do not present worse postoperative pain after THA. In addition, they show a significant improvement in their depressive symptoms one year after surgery.

Reply to "Comment on 'Validity of path thermodynamic description of reactive systems: Microscopic simulations' ".

The Comment's author argues that a correct description of reactive systems should incorporate an explicit interaction with reservoirs, leading to a unified system-reservoir entity. However, this proposition has two major flaws. First, as we will emphasize, this entity inherently follows a thermodynamic equilibrium distribution. In the Comment, no indication is provided on how to maintain such a system-reservoir entity in a nonequilibrium state. Second, contrary to the author's claim, the inclusion of a system-reservoir interaction in the traditional stochastic modeling of reactive systems does not automatically alter the limited applicability of path thermodynamics to problematic reactive systems. We will provide a simple demonstration to illustrate that certain elementary reactions may not involve any changes in reservoir components, which seem to have been overlooked by the author.

Modeling electrokinetic flows with the discrete ion stochastic continuum overdamped solvent algorithm.

In this article we develop an algorithm for the efficient simulation of electrolytes in the presence of physical boundaries. In previous work the discrete ion stochastic continuum overdamped solvent (DISCOS) algorithm was derived for triply periodic domains, and was validated through ion-ion pair correlation functions and Debye-Hückel-Onsager theory for conductivity, including the Wien effect for strong electric fields. In extending this approach to include an accurate treatment of physical boundaries we must address several important issues. First, the modifications to the spreading and interpolation operators necessary to incorporate interactions of the ions with the boundary are described. Next we discuss the modifications to the electrostatic solver to handle the influence of charges near either a fixed potential or dielectric boundary. An additional short-ranged potential is also introduced to represent interaction of the ions with a solid wall. Finally, the dry diffusion term is modified to account for the reduced mobility of ions near a boundary, which introduces an additional stochastic drift correction. Several validation tests are presented confirming the correct equilibrium distribution of ions in a channel. Additionally, the methodology is demonstrated using electro-osmosis and induced-charge electro-osmosis, with comparison made to theory and other numerical methods. Notably, the DISCOS approach achieves greater accuracy than a continuum electrostatic simulation method. We also examine the effect of under-resolving hydrodynamic effects using a "dry diffusion" approach, and find that considerable computational speedup can be achieved with a negligible impact on accuracy.

Clinical profile of patients with lupus psychosis in a Colombian cohort.

The objective of this study is to describe the frequency and the clinical, paraclinical, and treatment profile of patients with lupus psychosis in a Colombian cohort of patients with systemic lupus erythematosus (SLE). This retrospective cohort study evaluated epidemiological and clinical characteristics, results of neuroimaging, analysis of the cerebrospinal fluid, treatment, and disease evolution in patients with lupus psychosis. Among 2,479 patients with SLE, six female patients aged between 20 and 50 years with a diagnosis of lupus psychosis were identified. In two patients, psychosis was present at disease onset and in the other four, SLE was already present, although the majority of them were diagnosed less than two years prior to the onset of psychosis. The entire cohort had high disease activity as measured by SLEDAI-2K. We found concomitant cutaneous, joint, and hematological alterations. Cerebrospinal fluid data were obtained in half of the patients and were normal. We performed brain tomography on most of our patients, which was almost always described as normal. In 5 out of 6 patients, the induction therapy to treat psychosis was based on steroids, and in the majority of them, a resolution of psychiatric symptoms was observed after initiating treatment. Lupus psychosis is a rare event that usually occurs early in the course of the disease and is associated with other manifestations of SLE. This investigation mainly found concomitant cutaneous, joint, and hematological manifestations, with a favorable outcome after treatment, as described in the literature.

Using telomeric length measurements and methylation to understand the karyotype diversification of Ctenomys minutus (a small fossorial mammal).

The genus Ctenomys has been widely used in karyotype evolution studies due to the variation in their diploid numbers. Ctenomys minutus is characterized by intraspecific variation in diploid number (2n = 42, 46, 48, and 50), which makes it an interesting model to investigate genomic rearrangements mechanisms that could lead to different cytotypes in this species. Thereupon, it has been already shown that DNA methylation may participate in chromosome structure. Therefore, we aimed to investigate whether telomeres and global DNA methylation had a role in the genome rearrangements that led to this variation in C. minutus. We also realized an analysis for the presence of intrachromosomal telomeric repeats (ITRs) by fluorescence in situ hybridization. Our study demonstrated that neither telomere length nor DNA methylation had significant differences among the cytotypes. However, if only females were considered, there were significant differences for telomere length and methylation. Young individuals, regardless of their cytotypes, had the most methylated DNA. Regarding the ITRs, we found a signal on chromosome 1 in 2n = 50b. No evidence was found that telomere length or methylation could have influenced chromosomal rearrangements, although new cytotypes seem to have emerged within the distribution of parental cytotypes by the accumulation of different chromosomal rearrangements.

Adsorption kinetics and Box-Behnken design optimization for organic dyes on tungsten oxide.

Transition metal oxides have been applied to degrade organic dyes found in water bodies via photocatalysis. To do it, however, is essential that the dye molecules adsorb onto the metal oxide surface. Thus, optimizing the adsorption capacity of the adsorbent increases the probability of reaction between oxidation radicals and organic dye molecules and maximizes the effectiveness per gram of photocatalyst. With this in mind, we studied the adsorption behavior of Methylene Blue (MB) and Acid Orange 7 (AO7), two commonly found pollutants, as a function of dilution's pH, WO3 load, and initial dye concentration. We found out that WO3 adsorbs up to 80% of MB at pH = 6, and 13% of AO7 at pH = 2, although it is unable to adsorb AO7 at the natural pH of the dye dilution. Assuming a pseudo-second order kinetics model for the analysis of the MB adsorption amount, we determined a rate constant k2 = 6 × 10-2(g · mg-1)/min for the adsorption process. We put forward a molecular model for adsorption, driven by concentration gradients and electrostatic interactions. Finally, from a statistical analysis, we determined that pH is the most significant factor for the adsorption of MB and AO7 on WO3, reinforcing the notion that electrostatic interactions are the main mechanism driving the adsorption process. The Box-Behnken design optimization also evinces the key playing role of WO3 load in the adsorption percentage of AO7 and let us establish the optimal load required to maximize adsorption.

Indocyanine green fluorescence angiography in colorectal surgery. First case series in Mexico.

INTRODUCTION AND AIM: Anastomosis leak occurs in 1-19% of colorrectal surgeries. Our objective was to present the first Mexican case series on colorrectal surgery using indocyanine green fluorescence angiography to evaluate perfusion prior to carrying out the anastomosis. MATERIALS AND METHODS: A retrospective, analytic, descriptive study was conducted. We studied the case records of consecutive patients that underwent colorrectal surgery with indocyanine green angiography performed by the same group of colorrectal surgeons. RESULTS: Twenty-one case records were reviewed. Eleven (52.3%) of the patients were women, mean patient age was 57 years (38-82), and mean body mass index was 25 kg/m2 (17-34). Fifteen (71.4%) patients were diagnosed with malignant disease. Indocyanine green angiography changed our therapeutic decision in three (14.2%) patients. Two colorrectal anastomoses (14.2%) were performed at fewer than 5 cm from the anal verge and 13 (61.9%) were performed at more than 5 cm from the anal verge. Three of the anastomoses were ileocolic (14.2%), two were coloanal (9.5%), and one was ileoanal (4.7%). There were six (28.5%) complications, no cases of anastomotic leak, and no complications associated with the use of indocyanine green. The mortality rate was 0%. CONCLUSION: The present case series is the first on colorrectal surgery conducted in Mexico using indocyanine green fluorescence angiography, with excellent results.

Does the maternal-fetal transmission of SARS-CoV-2 occur during pregnancy?

BACKGROUND AND OBJETIVE: On January 7th, 2020, a new coronavirus, SARS-CoV-2, was identified, as responsible for a new human disease: COVID-19. Given its recent appearance, our current knowledge about the possible influence that this disease can exert on pregnancy is very limited. One of the unknowns to be solved is whether there is a vertical transmission of the infection during pregnancy. PATIENTS AND METHODS: Using the Real-time Polymerase Chain Reaction techniques for SARS-CoV-2 nucleic acids, the possible presence of this germ in vaginal discharge and amniotic fluid was investigated in four pregnant Caucasian patients affected by mild acute symptoms of COVID-19 during the second trimester of pregnancy. RESULTS: There is no laboratory evidence to suggest a possible passage of SARS-CoV-2 from the infected mother to the amniotic fluid. CONCLUSIONS: It is necessary to expand the investigation of COVID-19 cases diagnosed during pregnancy to clarify the real influence that SARS-CoV-2 has on pregnant women and their offspring, as well as those factors that modulate the disease.

Does the maternal-fetal transmission of SARS-CoV-2 occur during pregnancy? / ¿Existe transmisión materno-fetal del SARS-CoV-2 durante la gestación?

BACKGROUND AND OBJECTIVE: On January 7th, 2020, a new coronavirus, SARS-CoV-2, was identified, as responsible for a new human disease: COVID-19. Given its recent appearance, our current knowledge about the possible influence that this disease can exert on pregnancy is very limited. One of the unknowns to be solved is whether there is a vertical transmission of the infection during pregnancy. PATIENTS AND METHODS: Using the Real-time Polymerase Chain Reaction techniques for SARS-CoV-2 nucleic acids, the possible presence of this germ in vaginal discharge and amniotic fluid was investigated in four pregnant Caucasian patients affected by mild acute symptoms of COVID-19 during the second trimester of pregnancy. RESULTS: There is no laboratory evidence to suggest a possible passage of SARS-CoV-2 from the infected mother to the amniotic fluid. CONCLUSIONS: It is necessary to expand the investigation of COVID-19 cases diagnosed during pregnancy to clarify the real influence that SARS-CoV-2 has on pregnant women and their offspring, as well as those factors that modulate the disease.

Indocyanine green fluorescence angiography in colorrectal surgery. First case series in Mexico. / Angiografía por fluorescencia con verde de indocianina para cirugía de colon y recto. Primera serie reportada en México.

INTRODUCTION AND AIM: Anastomotic leak occurs in 1-19% of colorrectal surgeries. Our objective was to present the first Mexican case series on colorrectal surgery using indocyanine green fluorescence angiography to evaluate perfusion prior to carrying out the anastomosis. MATERIALS AND METHODS: A retrospective, analytic, descriptive study was conducted. We studied the case records of consecutive patients that underwent colorrectal surgery with indocyanine green angiography performed by the same group of colorrectal surgeons. RESULTS: Twenty-one case records were reviewed. Eleven (52.3%) of the patients were women, mean patient age was 57 years (38-82), and mean body mass index was 25 kg/m2 (17-34). Fifteen (71.4%) patients were diagnosed with malignant disease. Indocyanine green angiography changed our therapeutic decision in three (14.2%) patients. Two colorrectal anastomoses (14.2%) were performed at fewer than 5 cm from the anal verge and 13 (61.9%) were performed at more than 5 cm from the anal verge. Three of the anastomoses were ileocolic (14.2%), two were coloanal (9.5%), and one was ileoanal (4.7%). There were six (28.5%) complications, no cases of anastomotic leak, and no complications associated with the use of indocyanine green. The mortality rate was 0%. CONCLUSION: The present case series is the first on colorrectal surgery conducted in Mexico using indocyanine green fluorescence angiography, with excellent results.

The role of polymers in cross-kingdom bioadhesion.

The secretion of extracellular polymeric substances provides an evolutionary advantage found in many organisms that can adhere to surfaces and cover themselves in a protective matrix. This ability is found in prokaryotes, archaea and eukaryotes, all of which use functionally similar polysaccharides, proteins and nucleic acids to form extracellular matrices, mucus and bioadhesive substances. These macromolecules have been investigated from the perspective of polymer biophysics, and theories to help understand adhesion, viscosity and gelling have been developed. These properties can be measured experimentally using straightforward methods such as cell counting as well as more advanced techniques such as atomic force microscopy and rheometry. An integrated understanding of the properties and uses of adhesive macromolecules across kingdoms is also important and can provide the basis for a range of biotechnological and medical applications. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.

Mass transfer enhancement and improved nitrification in MABR through specific membrane configuration.

One of the main energy consumptions in wastewater treatment plants (WWTPs) is due to the oxygenation of aerobic biological processes. In order to approach to an energy self-sufficient scenario in WWTPs, Membrane Aerated Biofilm Reactors (MABRs) provide a good opportunity to reduce the impact of aeration on the global energy balance. However, mass transfer limitations derived from poor flow distribution must be tackled to take advantage of this technology. In this work, in order to improve mass transfer between biofilm and bulk water, a specific configuration was developed and studied at laboratory scale, aimed at compactness, energy efficiency and high nitrification rates. Nitrification rates were higher in the innovative configuration than in the conventional one, achieving a Volumetric Nitrification Rate (VNR) as high as 575.84 g NH4-N m-3 d-1, which is comparable with confirmed technologies. Regarding energy consumption due to aeration, a reduction of 83.7% was reached in comparison with aeration through diffusers with the same Oxygen Transfer Efficiency (OTE). These results highlight the importance of hydrodynamic conditions and the membranes configuration on treatment performance.

[«Man-in-the-barrel¼ syndrome: atypical manifestation of giant cell arteritis]. / Sindrome del hombre en el barril: manifestacion atipica de la arteritis de celulas gigantes.

INTRODUCTION: «Man-in-the-barrel¼ syndrome refers to diplegia of the upper extremities in which mobility of the head and lower limbs is preserved. Brachial plexitis that presents as «man-in-the-barrel¼ syndrome is an unusual manifestation of giant cell arteritis. We report a case of C5-C6 plexitis as part of the clinical features of a patient with giant cell arteritis. CASE REPORT: A 70-year-old male with a two-month history of weight loss, headache, facial pain and jaw claudication, associated with a persistent elevation of acute phase reactants and bilateral brachial plexopathy, with no evidence of neck or brain injuries or occult neoplasm and with negative autoimmunity tests. Results of the biopsy study of the temporal artery were compatible with giant cell arteritis, and the positron emission tomography scan revealed extensive vascular involvement of the aorta and its branches. CONCLUSIONS: Although the typical clinical manifestations of giant cell arteritis are headache, jaw claudication, loss of sight, constitutional symptoms and polymyalgia rheumatica, its presence must be suspected in patients over the age of 50 who manifest alterations affecting the peripheral nerve, including brachial diplegia with no other demonstrable cause.

TITLE: Sindrome del hombre en el barril: manifestacion atipica de la arteritis de celulas gigantes.Introduccion. El sindrome del hombre en el barril hace referencia a la diplejia de los miembros superiores con movilidad preservada de la cabeza y los miembros inferiores. La plexitis braquial que se presenta como sindrome del hombre en el barril es una manifestacion inusual de la arteritis de celulas gigantes. Se comunica un caso de plexitis C5-C6 como parte del cuadro clinico de un paciente con arteritis de celulas gigantes. Caso clinico. Varon de 70 años con dos meses de evolucion de perdida de peso, cefalea, dolor facial y claudicacion mandibular, asociados a elevacion persistente de reactantes de fase aguda y plexopatia braquial bilateral, sin evidencia de lesiones cervicales o cerebrales, neoplasia oculta y con pruebas de autoinmunidad negativas; la biopsia de la arteria temporal fue compatible con arteritis de celulas gigantes y la tomografia por emision de positrones demostro una extensa afeccion vascular de la aorta y sus ramas. Conclusiones. Si bien las manifestaciones clinicas tipicas de la arteritis de celulas gigantes son cefalea, claudicacion mandibular, perdida visual, sintomas constitucionales y polimialgia reumatica, se debe sospechar su presencia en pacientes mayores de 50 años que manifiesten alteraciones del nervio periferico, entre ellas, diplejia braquial sin otra causa demostrable.

Regression models to predict the behavior of the coefficient of friction of AISI 316L on UHMWPE under ISO 14243-3 conditions.

Friction is the natural response of all tribosystems. In a total knee replacement (TKR) prosthetic device, its measurement is hindered by the complex geometry of its integrating parts and that of the testing simulation rig operating under the ISO 14243-3:2014 standard. To develop prediction models of the coefficient of friction (COF) between AISI 316L steel and ultra-high molecular weight polyethylene (UHMWPE) lubricated with fetal bovine serum dilutions, the arthrokinematics and loading conditions prescribed by the ISO 142433: 2014 standard were translated to a simpler geometrical setup, via Hertz contact theory. Tribological testing proceeded by loading a stainless steel AISI 316L ball against the surface of a UHMWPE disk, with the test fluid at 37 °C. The method has been applied to study the behavior of the COF during a whole walking cycle. On the other hand, the role of protein aggregation phenomena as a lubrication mechanism has been extensively studied in hip joint replacements but little explored for the operating conditions of a TKR. Lubricant testing fluids were prepared with fetal bovine serum (FBS) dilutions having protein mass concentrations of 5, 10, 20 and 36 g/L. The results were contrasted against deionized, sterilized water. The results indicate that even at protein concentration as low as 5 g/L, protein aggregation phenomena play an important role in the lubrication of the metal-on-polymer tribopair. The regression models of the COF developed herein are available for numerical simulations of the tribological behavior of the aforementioned tribosystem. In this case, surface stress rather than film thickness should be considered.

Amino acid profiles of young adults differ by sex, body mass index and insulin resistance.

BACKGROUND AND AIMS: An increase in plasma branched-chain amino acids is associated with a higher risk of developing type 2 diabetes and cardiovascular diseases. However, little is known about the basal plasma amino acid concentrations in young adults. Our aim was to determine the plasma amino acid profiles of young adults and to evaluate how these profiles were modified by sex, body mass index (BMI) and insulin resistance (IR). METHODS AND RESULTS: We performed a transversal study with 608 Mexican young adults aged 19.9 ± 2.4 years who were applicants to the Universidad Autónoma de San Luis Potosí. The subjects underwent a physical examination and provided a clinical history and a blood sample for biochemical, hormonal and amino acid analyses. The women had higher levels of arginine, aspartate and serine and lower levels of α-aminoadipic acid, cysteine, isoleucine, leucine, methionine, proline, tryptophan, tyrosine, urea and valine than the men. The obese subjects had higher levels of alanine, aspartate, cysteine, ornithine, phenylalanine, proline and tyrosine and lower levels of glycine, ornithine and serine than the normal weight subjects. Subjects with IR (defined as HOMA > 2.5) had higher levels of arginine, alanine, aspartate, isoleucine, leucine, phenylalanine, proline, tyrosine, taurine and valine than the subjects without IR. Furthermore, we identified two main groups in the subjects with obesity and/or IR; one group was composed of amino acids that positively correlated with the clinical, biochemical and hormonal parameters, whereas the second group exhibited negative correlations. CONCLUSION: This study demonstrates that young adults with obesity or IR have altered amino acid profiles characterized by an increase in alanine, aspartate, proline and tyrosine and a decrease in glycine.

Serotonin inputs to the dorsal BNST modulate anxiety in a 5-HT1A receptor-dependent manner.

Serotonin (5-HT) neurons project from the raphe nuclei throughout the brain where they act to maintain homeostasis. Here, we study 5-HT inputs into the bed nucleus of the stria terminalis (BNST), a major subdivision of the extended amygdala that has been proposed to regulate responses to anxiogenic environments in humans and rodents. While the dorsal part of the BNST (dBNST) receives dense 5-HT innervation, whether and how 5-HT in the dBNST normally modulates anxiety remains unclear. Using optogenetics, we demonstrate that activation of 5-HT terminals in the dBNST reduces anxiety in a highly anxiogenic environment. Further analysis revealed that optogenetic inhibition of 5-HT inputs into the dBNST increases anxiety in a less anxiogenic environment. We found that 5-HT predominantly hyperpolarizes dBNST neurons, reducing their activity in a manner that can be blocked by a 5-HT1A antagonist. Finally, we demonstrate that activation of 5-HT1A receptors in the dBNST is necessary for the anxiolytic effect observed following optogenetic stimulation of 5-HT inputs into the dBNST. These data reveal that 5-HT release in the dBNST modulates anxiety-like behavior via 5-HT1A receptors under naturalistic conditions.

Urinary neutrophil gelatinase-associated lipocalin and monocyte chemoattractant protein 1 as biomarkers for lupus nephritis in Colombian SLE patients.

Background Information regarding urinary biomarkers in Mestizo and Afro-Latin-American patients is very limited. We investigated whether levels of urinary neutrophil gelatinase-associated lipocalin (NGAL), and monocyte chemoattractant protein 1 (MCP-1) are good biomarkers to differentiate patients with lupus nephritis among Latin-American systemic lupus erythematosus (SLE) patients. Methods SLE patients meeting the revised American College of Rheumatology classification criteria for SLE were recruited. Urinary levels of NGAL and MCP-1 were measured using a commercial ELISA kit. Serum anti-C1q antibodies were measured by ELISA. SLE activity was measured with the systemic lupus erythematosus disease activity index (SLEDAI). Mann-Whitney tests were used to compare data and Spearman's rank correlations were used to examine associations between continuous variables. In addition, receiver operating characteristic curves were performed. Results One hundred and twenty SLE patients were recruited (87% women) with a median age of 32.8 ± 12.1 years and median disease duration of 7.3 ± 6.9 years. Afro-Latin-Americans had a significantly higher prevalence of lupus nephritis and higher SLEDAI scores than Mestizos. The three biomarkers were significantly higher in patients with lupus nephritis than in patients without lupus nephritis. In addition, urinary NGAL and MCP-1 were significantly higher in patients with active lupus nephritis than in inactive lupus nephritis. Urinary NGAL levels were significantly higher in Afro-Latin-American patients. A receiver operating characteristic curve for urinary biomarkers for lupus nephritis in all SLE patients showed a good level of sensitivity and specificity. Conclusion In our cohort of SLE patients, we found that urinary NGAL and MCP-1 in addition to anti-C1q antibodies were useful biomarkers for the identification of renal involvement and discrimination of active lupus nephritis among patients with renal disease.

A comparison of two clinical scores for bronchiolitis. A multicentre and prospective study conducted in hospitalised infants.

BACKGROUND: There are a number of clinical scores for bronchiolitis but none of them are firmly recommended in the guidelines. METHOD: We designed a study to compare two scales of bronchiolitis (ESBA and Wood Downes Ferres) and determine which of them better predicts the severity. A multicentre prospective study with patients <12 months with acute bronchiolitis was conducted. Each patient was assessed with the two scales when admission was decided. We created a new variable "severe condition" to determine whether one scale afforded better discrimination of severity. A diagnostic test analysis of sensitivity and specificity was made, with a comparison of the AUC. Based on the optimum cut-off points of the ROC curves for classifying bronchiolitis as severe we calculated new Se, Sp, LR+ and LR- for each scale in our sample. RESULTS: 201 patients were included, 66.7% males and median age 2.3 months (IQR=1.3-4.4). Thirteen patients suffered bronchiolitis considered to be severe, according to the variable severe condition. ESBA showed a Se=3.6%, Sp=98.1%, and WDF showed Se=46.2% and Sp=91.5%. The difference between the two AUC for each scale was 0.02 (95%CI: 0.01-0.15), p=0.72. With new cut-off points we could increase Se and Sp for ESBA: Se=84.6%, Sp=78.7%, and WDF showed Se=92.3% and Sp=54.8%; with higher LR. CONCLUSIONS: None of the scales studied was considered optimum for assessing our patients. With new cut-off points, the scales increased the ability to classify severe infants. New validation studies are needed to prove these new cut-off points.

Periodic venting of MABR lumen allows high removal rates and high gas-transfer efficiencies.

The membrane-aerated biofilm reactor (MABR) is a novel treatment technology that employs gas-supplying membranes to deliver oxygen directly to a biofilm growing on the membrane surface. When operated with closed-end membranes, the MABR provides 100-percent oxygen transfer efficiencies (OTE), resulting in significant energy savings. However, closed-end MABRs are more sensitive to back-diffusion of inert gases, such as nitrogen. Back-diffusion reduces the average oxygen transfer rates (OTR), consequently decreasing the average contaminant removal fluxes (J). We hypothesized that venting the membrane lumen periodically would increase the OTR and J. Using an experimental flow cell and mathematical modeling, we showed that back-diffusion gas profiles developed over relatively long timescales. Thus, very short ventings could re-establish uniform gas profiles for relatively long time periods. Using modeling, we systematically explored the effect of the venting interval (time between ventings). At moderate venting intervals, opening the membrane for 20 s every 30 min, the venting significantly increased the average OTR and J without substantially impacting the OTEs. When the interval was short enough, in this case shorter than 20 min, the OTR was actually higher than for continuous open-end operation. Our results show that periodic venting is a promising strategy to combine the advantages of open-end and closed end operation, maximizing both the OTR and OTE.