Staphylococcus aureus Serine protease-like protein A (SplA) induces IL-8 by keratinocytes and synergizes with IL-17A.

BACKGROUND: Serine protease-like (Spl) proteins produced by Staphylococcus (S.) aureus have been associated with allergic inflammation. However, effects of Spls on the epidermal immune response have not been investigated. OBJECTIVES: To assess the epidermal immune response to SplA, SplD and SplE dependent on differentiation of keratinocytes and a Th2 or Th17 cytokine milieu. METHODS: Human keratinocytes of healthy controls and a STAT3-hyper-IgE syndrome (STAT3-HIES) patient were cultured in different calcium concentrations in the presence of Spls and Th2 or Th17 cytokines. Keratinocyte-specific IL-8 production and concomitant migration of neutrophils were assessed. RESULTS: SplE and more significantly SplA, induced IL-8 in keratinocytes. Suprabasal-like keratinocytes showed a higher Spl-mediated IL-8 production and neutrophil migration compared to basal-like keratinocytes. Th17 cytokines amplified Spl-mediated IL-8 production, which correlated with neutrophil recruitment. Neutrophil recruitment by keratinocytes of the STAT3-HIES patient was similar to healthy control cells. CONCLUSION: S. aureus-specific Spl proteases synergized with IL-17A on human keratinocytes with respect to IL-8 release and neutrophil migration, highlighting the importance of keratinocytes and Th17 immunity in barrier function.

First Leptophobic Dark Matter Search from the Coherent-CAPTAIN-Mills Liquid Argon Detector.

We report the first results of a search for leptophobic dark matter (DM) from the Coherent-CAPTAIN-Mills (CCM) liquid argon (LAr) detector. An engineering run with 120 photomultiplier tubes (PMTs) and 17.9×10^{20} protons on target (POT) was performed in fall 2019 to study the characteristics of the CCM detector. The operation of this 10-ton detector was strictly light based with a threshold of 50 keV and used coherent elastic scattering off argon nuclei to detect DM. Despite only 1.5 months of accumulated luminosity, contaminated LAr, and nonoptimized shielding, CCM's first engineering run has already achieved sensitivity to previously unexplored parameter space of light dark matter models with a baryonic vector portal. With an expected background of 115 005 events, we observe 115 005+16.5 events which is compatible with background expectations. For a benchmark mediator-to-DM mass ratio of m_{V_{B}}/m_{χ}=2.1, DM masses within the range 9 MeV≲m_{χ}≲50 MeV are excluded at 90% C. L. in the leptophobic model after applying the Feldman-Cousins test statistic. CCM's upgraded run with 200 PMTs, filtered LAr, improved shielding, and 10 times more POT will be able to exclude the remaining thermal relic density parameter space of this model, as well as probe new parameter space of other leptophobic DM models.

Donor BMI >30 Is Not a Contraindication for Live Liver Donation.

The increased prevalence of obesity worldwide threatens the pool of living liver donors. Although the negative effects of graft steatosis on liver donation and transplantation are well known, the impact of obesity in the absence of hepatic steatosis on outcome of living donor liver transplantation (LDLT) is unknown. Consequently, we compared the outcome of LDLT using donors with BMI <30 versus donors with BMI ≥30. Between April 2000 and May 2014, 105 patients received a right-lobe liver graft from donors with BMI ≥30, whereas 364 recipients were transplanted with grafts from donors with BMI <30. Liver steatosis >10% was excluded in all donors with BMI >30 by imaging and liver biopsies. None of the donors had any other comorbidity. Donors with BMI <30 versus ≥30 had similar postoperative complication rates (Dindo-Clavien ≥3b: 2% vs. 3%; p = 0.71) and lengths of hospital stay (6 vs. 6 days; p = 0.13). Recipient graft function, assessed by posttransplant peak serum bilirubin and international normalized ratio was identical. Furthermore, no difference was observed in recipient complication rates (Dindo-Clavien ≥3b: 25% vs. 20%; p = 0.3) or lengths of hospital stay between groups. We concluded that donors with BMI ≥30, in the absence of graft steatosis, are not contraindicated for LDLT.

First-Degree Living-Related Donor Liver Transplantation in Autoimmune Liver Diseases.

Liver transplantation (LT) is the treatment of choice for end-stage autoimmune liver diseases. However, the underlying disease may recur in the graft in some 20% of cases. The aim of this study is to determine whether LT using living donor grafts from first-degree relatives results in higher rates of recurrence than grafts from more distant/unrelated donors. Two hundred sixty-three patients, who underwent a first LT in the Toronto liver transplant program between January 2000 and March 2015 for autoimmune liver diseases, and had at least 6 months of post-LT follow-up, were included in this study. Of these, 72 (27%) received a graft from a first-degree living-related donor, 56 (21%) from a distant/unrelated living donor, and 135 (51%) from a deceased donor for primary sclerosing cholangitis (PSC) (n = 138, 52%), primary biliary cholangitis (PBC) (n = 69, 26%), autoimmune hepatitis (AIH) (n = 44, 17%), and overlap syndromes (n = 12, 5%). Recurrence occurred in 52 (20%) patients. Recurrence rates for each autoimmune liver disease were not significantly different after first-degree living-related, living-unrelated, or deceased-donor LT. Similarly, time to recurrence, recurrence-related graft failure, graft survival, and patient survival were not significantly different between groups. In conclusion, first-degree living-related donor LT for PSC, PBC, or AIH is not associated with an increased risk of disease recurrence.

Universal prophylaxis or preemptive strategy for cytomegalovirus disease after liver transplantation: a systematic review and meta-analysis.

We systematically reviewed and meta-analyze the efficacy of universal prophylaxis (UP) and preemptive (PE) strategies (using ganciclovir or valganciclovir) in preventing cytomegalovirus (CMV) disease (CMD) among liver transplant recipients (LTRs). We performed an electronic search of MEDLINE, EMBASE and the Cochrane Database till December 2013. Studies that assessed UP or PE for preventing CMD in LTRs were included. The risk of bias was assessed using the Newcastle-Ottawa scale. The primary outcome was CMD, secondary outcomes being acute cellular rejection (ACR), graft loss (GL) and mortality. Due to the heterogeneity of comparative studies, an indirect comparison was performed. Pooled incidence rates with 95% confidence interval (CI) are calculated for each outcome using a random-effects model. Thirty-two studies involving 2456 LTRs were included. The majority of the studies were of low risk of bias. Irrespective of donor/recipient CMV sero-status, CMD was 10% with UP (95% CI: 6-14; I(2) = 87%; 16 studies, n = 1581) and 7% with PE (95% CI: 3-10; I(2) = 84%; 16 studies, n = 875) (mean difference 2.6; 95% CI: -3.25 to 8.45, p = 0.34). Likewise, ACR and mortality were similar with the two strategies. However, GL was significantly lower in the UP group, regardless of donor/recipient sero-status. In indirect comparison, the incidence of CMD, ACR and mortality in LTRs were similar with two strategies. Trials comparing the two strategies directly are needed.

Live donor liver transplantation: a valid alternative for critically ill patients suffering from acute liver failure.

We report the outcome of live donor liver transplantation (LDLT) for patients suffering from acute liver failure (ALF). From 2006 to 2013, all patients with ALF who received a LDLT (n = 7) at our institution were compared to all ALF patients receiving a deceased donor liver transplantation (DDLT = 26). Groups were comparable regarding pretransplant ICU stay (DDLT: 1 [0-7] vs. LDLT: 1 days [0-10]; p = 0.38), mechanical ventilation support (DDLT: 69% vs. LDLT: 57%; p = 0.66), inotropic drug requirement (DDLT: 27% vs. LDLT: 43%; p = 0.64) and dialysis (DDLT: 2 vs. LDLT: 0 patients; p = 1). Median evaluation time for live donors was 24 h (18-72 h). LDLT versus DDLT had similar incidence of overall postoperative complications (31% vs. 43%; p = 0.66). No difference was detected between LDLT and DDLT patients regarding 1- (DDLT: 92% vs. LDLT: 86%), 3- (DDLT: 92% vs. LDLT: 86%), and 5- (DDLT: 92% vs. LDLT: 86%) year graft and patient survival (p = 0.63). No severe donor complication (Dindo-Clavien ≥3 b) occurred after live liver donation. ALF is a severe disease with high mortality on liver transplant waiting lists worldwide. Therefore, LDLT is an attractive option since live donor work-up can be expedited and liver transplantation can be performed within 24 h with excellent short- and long-term outcomes.

Living vs. deceased donor liver transplantation provides comparable recovery of renal function in patients with hepatorenal syndrome: a matched case-control study.

Outcomes of living versus deceased donor liver transplantation in patients with chronic liver disease and hepatorenal syndrome (HRS) was compared using a matched pair study design. Thirty patients with HRS receiving a live donor liver transplantation (LDLT) and 90 HRS patients receiving a full graft deceased donor liver transplantation (DDLT) were compared. LDLT versus DDLT of patients with HRS was associated with decreased peak aspartate aminotransferase levels (339 ± 214 vs. 935 ± 1253 U/L; p = 0.0001), and similar 7-day bilirubin (8.42 ± 7.89 vs. 6.95 ± 7.13 mg/dL; p = 0.35), and international normalized ratio levels (1.93 ± 0.62 vs. 1.78 ± 0.78; p = 0.314). LDLT vs. DDLT had a decreased intensive care unit (2 [1-39] vs. 4 [0-93] days; p = 0.004), and hospital stay (17 [4-313] vs. 26 [0-126] days; p = 0.016) and a similar incidence of overall postoperative complications (20% vs. 27%; p = 0.62). No difference was detected between LDLT and DDLT patients regarding graft survival at 1 (80% vs. 82%), at 3 (69% vs. 76%) and 5 years (65% vs. 76%) (p = 0.63), as well as patient survival at 1 (83% vs. 82%), 3 (72% vs. 77%) and 5 years (72% vs. 77%) (p = 0.93). The incidence of chronic kidney disease post-LT (10% vs. 6%; p = 0.4) was similar between both groups. LDLT results in identical long-term outcome when compared with DDLT in patients with HRS.

Atopic dermatitis, STAT3- and DOCK8-hyper-IgE syndromes differ in IgE-based sensitization pattern.

BACKGROUND: Increased serum IgE levels are characteristic but not specific for allergic diseases. Particularly, severe atopic dermatitis (AD) overlaps with hyper-IgE syndromes (HIES) regarding eczema, eosinophilia, and increased serum IgE levels. HIES are primary immunodeficiencies due to monogenetic defects such as in the genes DOCK8 and STAT3. As it is not known to date why allergic manifestations are not present in all HIES entities, we assessed the specificity of serum IgE of AD and HIES patients in the context of clinical and immunological findings. METHODS: Clinical data, skin prick tests, specific IgE to aero- and food allergens, and T helper (Th) subpopulations were compared in AD and molecularly defined HIES patients. RESULTS: Total serum IgE levels were similarly increased in STAT3-HIES, DOCK8-HIES, and AD patients. The ratio of aeroallergen-specific IgE to total IgE was highest in AD, whereas DOCK8-HIES patients showed the highest specific serum IgE against food allergens. Overall, clinical allergy and skin prick test results complied with the specific IgE results. Th2-cell numbers were significantly increased in DOCK8-HIES and AD patients compared to STAT3-HIES patients and controls. AD patients showed significantly higher nTreg-cell counts compared to STAT3-HIES and control individuals. High Th17-cell counts were associated with asthma. Specific IgE values, skin prick test, and T-cell subsets of STAT3-HIES patients were comparable with those of healthy individuals except decreased Th17-cell counts. CONCLUSION: Hyper-IgE syndromes and atopic dermatitis patients showed different sensitization pattern of serum IgE corresponding to the allergic disease manifestations and Th-cell subset data, suggesting a key role of DOCK8 in the development of food allergy.

A comparative study of the use of selective digestive decontamination prophylaxis in living-donor liver transplant recipients.

INTRODUCTION: Bacterial infections are major causes of early morbidity and mortality after liver transplantation. Selective digestive decontamination (SDD) can be used pre-operatively for living-donor liver transplant (LD-LT), but its role in this setting remains controversial. METHODS: To evaluate this strategy, we retrospectively analyzed a cohort of consecutive LD-LTs performed in our center from March 2007 to February 2011 and compared the incidence and nature of early infectious complications, length of intensive care unit stay and hospitalization, antibiotic use, and emergence of resistant bacteria in patients with or without SDD prophylaxis. RESULTS: Of 148 LD-LTs in the study period, 111 received SDD prophylaxis while 37 did not. In a multivariate model, the independent factors associated with an increased risk of early post-transplant infections were length of postoperative mechanical ventilation (for every additional day odds ratio [OR] = 2.37, 95% confidence interval [CI] 1.4-4.0; P = 0.002), and choledochojejunostomy (OR = 4.5, 95% CI 1.95-10.5; P < 0.001). Use of SDD did not affect the rate or distribution of infectious complications, duration of hospitalization, antibiotic use, or acquisition of resistant bacteria (OR = 3.52, 95% CI 0.43-15.17; P = 0.376). CONCLUSION: In conclusion, the use of SDD prophylaxis in LD-LT was not beneficial and should be avoided, as it offers no advantage and could potentiate the emergence of multidrug-resistant organisms.

Scintillation characteristics of the EJ-299-02H scintillator.

A study of the dead layer thickness and quenching factor of a plastic scintillator for use in ultracold neutron (UCN) experiments is described. Alpha spectroscopy was used to determine the thickness of a thin surface dead layer to be 630 ± 110 nm. The relative light outputs from the decay of 241Am and Compton scattering of electrons were used to extract Birks' law coefficient, yielding a kB value of 0.087 ± 0.003 mm/MeV, consistent with some previous reports for other polystyrene-based scintillators. The results from these measurements are incorporated into the simulation to show that an energy threshold of (∼9 keV) can be achieved for the UCNProBe experiment. This low threshold enables high beta particle detection efficiency and the indirect measurement of UCN. The ability to make the scintillator deuterated, accompanied by its relatively thin dead layer, gives rise to unique applications in a wide range of UCN experiments, where it can be used to trap UCN and detect charged particles in situ.

Hepatitis C core Ag and its clinical applicability: potential advantages and disadvantages for diagnosis and follow-up?

Chronic hepatitis C virus (HCV) infection which is often a silent disease has resulted in a global epidemic. The diagnosis of hepatitis C virus often requires confirmation with molecular techniques such as the polymerase chain reaction for detection of HCV RNA. Following laboratory confirmation of the diagnosis, molecular techniques are routinely used to monitor HCV RNA levels, particularly in those undergoing treatment. Unfortunately, molecular tests are relatively expensive and their cost may be prohibitive in the developing world. Several studies have investigated the applicability of the hepatitis C core Ag (HCVcAg), as a substitute for measuring HCV RNA levels. In this review, we provide an overview of the major findings of these studies focused on the utility of measuring HCVcAg antigen levels in the clinical setting. Overall, measuring HCVcAg levels is associated with several advantages and disadvantages. It may be useful in different clinical settings for monitoring HCV patients after obtaining an initial baseline HCV RNA result.

Daily ciprofloxacin treatment for patients with advanced liver disease awaiting liver transplantation reduces hospitalizations.

BACKGROUND: Progressive deterioration in liver function is a common cause of hepatic decompensation and indication for liver transplantation in patients with advanced liver disease. Previous studies in animal models of acute and chronic liver disease revealed that daily ciprofloxacin improves biochemical parameters of hepatic function. AIMS: The primary objective of this study was to determine whether hepatic function improves in patients with advanced liver disease after 1 month of daily ciprofloxacin therapy. A secondary objective was to determine whether ciprofloxacin treatment for 1 or 3 months results in fewer hospitalizations for decompensated liver disease. METHODS: Forty-four patients with advanced liver disease awaiting liver transplantation received oral ciprofloxacin (250 or 500 mg twice daily) or placebo for 1 (n=22/group) or 3 (n=10 ciprofloxacin, 14 placebo) months. RESULTS: Compared to placebo recipients, ciprofloxacin-treated patients had mild improvements in serum albumin levels (+1.5 versus -3.4%, p=0.026) while bilirubin and international normalized ratios (INR) of prothrombin times remained unchanged. Overall, fewer hospitalizations occurred in ciprofloxacin-treated patients (1/22, 5% versus 7/22, 32%, respectively, p=0.02) during the study period. Treatment was well tolerated and no resistant infections occurred in either cohort. CONCLUSIONS: The results of this study suggest that daily ciprofloxacin may result in fewer hospitalizations for patients with advanced liver diseases awaiting liver transplantation but not by enhancing hepatic function.

Adult living liver donors have excellent long-term medical outcomes: the University of Toronto liver transplant experience.

Right lobe living donor liver transplantation is an effective treatment for selected individuals with end-stage liver disease. Although 1 year donor morbidity and mortality have been reported, little is known about outcomes beyond 1 year. Our objective was to analyze the outcomes of the first 202 consecutive donors performed at our center with a minimum follow-up of 12 months (range 12-96 months). All physical complications were prospectively recorded and categorized according to the modified Clavien classification system. Donors were seen by a dedicated family physician at 2 weeks, 1, 3 and 12 months postoperatively and yearly thereafter. The cohort included 108 males and 94 females (mean age 37.3 +/- 11.5 years). Donor survival was 100%. A total of 39.6% of donors experienced a medical complication during the first year after surgery (21 Grade 1, 27 Grade 2, 32 Grade 3). After 1 year, three donors experienced a medical complication (1 Grade 1, 1 Grade 2, 1 Grade 3). All donors returned to predonation employment or studies although four donors (2%) experienced a psychiatric complication. This prospective study suggests that living liver donation can be performed safely without any serious late medical complications and suggests that long-term follow-up may contribute to favorable donor outcomes.

Successful long-term correction of autosomal recessive hyper-IgE syndrome due to DOCK8 deficiency by hematopoietic stem cell transplantation.

Autosomal dominant hyper-IgE syndrome (AD-HIES), characterised by eczema, increased susceptibility to skin and lung infections, elevated IgE and skeletal abnormalities is associated with heterozygous STAT3 mutations. The autosomal recessive variant (AR-HIES) has similar immunological findings but mainly lacks extraimmune manifestations. Several AR-HIES patients have recently been shown to harbour mutations in the gene for dedicator of cytokinesis 8 (DOCK8). Here, we present the long-term outcome of a girl having received a hematopoietic stem cell graft for an at that time genetically undefined combined immunodeficiency associated with severe eczema, multiple food allergies, excessively elevated serum IgE levels and eosinophilia. She was recently found to carry a homozygous nonsense mutation in the DOCK8 gene. HSCT resulted in complete immunological correction, even though mixed donor chimerism occurred. Clinically, the outcome was characterised by disappearance of skin manifestations and severe infections, improvement of pulmonary function and constant decline of IgE levels. Outcome in untransplanted DOCK8 deficient patients is poor because of frequent life-threatening infections, CNS bleeding and infarction, and increased susceptibility to malignancy. This argues for early curative therapeutic approaches, supported by this report of successful long-term outcome after HSCT.

[Vaccinations with atopic dermatitis and other chronic inflammatory skin diseases]. / Impfungen bei Neurodermitis und anderen chronisch entzündlichen Hauterkrankungen.

One of the most effective preventive measures in medicine is vaccination for avoidance of vaccination preventable diseases. If higher vaccination rates could be achieved individual pathogens could be eliminated and even made extinct. Vaccination is not obligatory in Germany. In previous decades many diseases which were preventable by vaccination have become rare. Being unaware of the course of the disease, the willingness to be vaccinated decreases and doubts about vaccination increase. If atopic dermatitis or allergy is known, the doctor performing the vaccination and also the dermatologist are often asked questions on the indications, performing standard vaccination and the vaccination schedule. This review article is intended to supply dermatologists with answers to frequently asked questions on indications and performing standard vaccinations in connection with atopic dermatitis, allergies and chronic inflammatory skin diseases. Although patients often have uncertainties and doubts, undesirable severe medicinal effects are rare even for patients with atopic dermatitis.

Adult right-lobe living liver donors: quality of life, attitudes and predictors of donor outcomes.

To refine selection criteria for adult living liver donors and improve donor quality of care, risk factors for poor postdonation health-related quality of life (HRQOL) must be identified. This cross-sectional study examined donors who underwent a right hepatectomy at the University of Toronto between 2000 and 2007 (n = 143), and investigated predictors of (1) physical and mental health postdonation, as well as (2) willingness to participate in the donor process again. Participants completed a standardized HRQOL measure (SF-36) and measures of the pre- and postdonation process. Donor scores on the SF-36 physical and mental health indices were equivalent to, or greater than, population norms. Greater predonation concerns, a psychiatric diagnosis and a graduate degree were associated with lower mental health postdonation whereas older donors reported better mental health. The majority of donors (80%) stated they would donate again but those who perceived that their recipient engaged in risky health behaviors were more hesitant. Prospective donors with risk factors for lower postdonation satisfaction and mental health may require more extensive predonation counseling and postdonation psychosocial follow-up. Risk factors identified in this study should be prospectively evaluated in future research.

Host- rather than virus-related factors reduce health-related quality of life in hepatitis C virus infection.

BACKGROUND: Hepatitis C virus (HCV) infection is associated with decreased health-related quality of life (HRQOL). Although HCV has been suggested to directly impair neuropsychiatric functions, other factors may also play a role. PATIENTS AND METHODS: In this cross-sectional study, we assessed the impact of various host-, disease- and virus-related factors on HRQOL in a large, unselected population of anti-HCV-positive subjects. All individuals (n = 1736) enrolled in the Swiss Hepatitis C Cohort Study (SCCS) were asked to complete the Short Form 36 (SF-36) and the Hospital Anxiety Depression Scale (HADS). RESULTS: 833 patients (48%) returned the questionnaires. Survey participants had significantly worse scores in both assessment instruments when compared to a general population. By multivariable analysis, reduced HRQOL (mental and physical summary scores of SF-36) was independently associated with income. In addition, a low physical summary score was associated with age and diabetes, whereas a low mental summary score was associated with intravenous drug use. HADS anxiety and depression scores were independently associated with income and intravenous drug use. In addition, HADS depression score was associated with diabetes. None of the SF-36 or HADS scores correlated with either the presence or the level of serum HCV RNA. In particular, SF-36 and HADS scores were comparable in 555 HCV RNA-positive and 262 HCV RNA-negative individuals. CONCLUSIONS: Anti-HCV-positive subjects have decreased HRQOL compared to controls. The magnitude of this decrease was clinically important for the SF-36 vitality score. Host and environmental, rather than viral factors, seem to impact on HRQOL level.

Autoimmune hepatitis in a North American Aboriginal/First Nations population.

North American Aboriginal populations are at increased risk for developing immune-mediated disorders, including autoimmune hepatitis. In the present study, the demographic, clinical, biochemical, serological, radiological and histological features of autoimmune hepatitis were compared in 33 First Nations (FN) and 150 predominantly Caucasian, non-FN patients referred to an urban tertiary care centre. FN patients were more often female (91% versus 71%; P=0.04), and more likely to have low serum albumin (69% versus 36%; P=0.0006) and elevated bilirubin (57% versus 35%; P=0.01) levels on presentation compared with non-FN patients. They also had lower hemoglobin, and complement levels, more cholestasis and higher serum immunoglobulin A levels than non-FN patients (P=0.05 respectively). Higher histological grades of inflammation and stages of fibrosis, and more clinical and radiological evidence of advanced liver disease were observed in FN patients, but the differences failed to reach statistical significance. The results of the present study suggest that in addition to being more common, autoimmune hepatitis may be more severe in FN populations, compared with predominantly Caucasian, non-FN populations.

Survival after liver transplantation for hepatitis C is unchanged over two decades in Canada.

Allograft failure secondary to recurrence of hepatitis C virus (HCV) infection is the most common cause of death and retransplantation among recipients with HCV infection. It has been suggested that patients transplanted for HCV have had worse outcomes in more recent years than in previous years (the 'era effect'). A Canadian transplantation registry database was analyzed to determine the outcomes of patients transplanted over the years for HCV. The results of the present analysis of 1002 patients show that the 'era effect' was not seen in liver transplantation recipients with HCV in Canada, because no survival difference was noted based on the year of transplantation. All groups had overall two-year and five-year survival rates of 76% to 83% and 69% to 72%, respectively. The present study's national results prove continued benefit to transplantation of HCV patients.

Validation of masks for determination of V̇O2 max in horses exercising at high intensity.

BACKGROUND: The need for a horse to be ridden while wearing a measurement device that allows unrestricted ventilation and gas exchange has hampered accurate measurement of its maximal oxygen consumption (V̇O2 max) under field conditions. OBJECTIVES: Design and validate a facemask with the potential to measure V̇O2 max accurately in the field. STUDY DESIGN: Experiment with 6 × 6 Latin square design. METHODS: Two variations of a mask and associated electronic control module (ECM) were designed to enable breath-by-breath measurement of airflows through two 7.8 cm diameter pneumotachometers located 7.5 cm in front of each narus. The ECM was comprised of an analogue-to-digital converter and a lithium-ion battery that provided power and signal filtering to the pneumotachometers and an oxygen sensing cell, and powered a pump connected to gas sampling ports between the nares and pneumotachometers. Airflow and oxygen content of inspired and expired gases were recorded through the ECM and electronically transferred to a notebook. V̇O2 was determined from these recordings using a customised software program. Mask B encased the lower jaw. Mask R left the jaw free so the horse could wear a bit if ridden. V̇O2 max and arterial blood gases were measured in 6 horses during multiple treadmill tests. Each mask was worn twice and results compared to those from an established open flow-through system (O) by ANOVA-RM (P<0.05). System utility was evaluated using the intraclass correlation coefficient of 4 independent raters. RESULTS: Blood gases and V̇O2 max (151.9±7.0 [mean±s.d.; O], 151.5±9.6 [B], 149.5±7.5 [R] ml/[kg.min]) were not different between masks. V̇O2 max measures were reproducible for each mask. Intraclass correlation coefficient between raters = 0.99. MAIN LIMITATIONS: Some rebreathing of expired air from mask dead space. CONCLUSION: Masks capable of measuring V̇O2 max during treadmill exercise were developed, tested and found to be accurate. Mask R has potential application to measurement of V̇O2 max under field conditions.