Organoselenium Polymer Inhibits Biofilm Formation in Polypropylene Contact Lens Case Material.

OBJECTIVES: Contact lens-acquired bacterial infections are a serious problem. Of the reported cases, inadequate cleaning of the lens case was the most common cause of lens contamination. Organoselenium has been shown to inhibit bacterial attachment to different polymer materials. This study evaluates the ability of an organoselenium monomer, incorporated into the polymer of a polypropylene contact lens case coupon, to block the formation of biofilms in a lens case. METHODS: The bacteria tested were Pseudomonas aeruginosa, Staphylococcus aureus, Stenotrophomonas maltophilia, and Serratia marcescens. For this study, the bacteria were allowed to grow overnight, in trypticase soy broth media, in the presence of the selenium-containing polymer or the same polymer without organoselenium. The material was studied by both colony-forming unit determination and by confocal laser scanning microscopy. RESULTS: The results showed that the organoselenium polymer versus the control polymer resulted in the following effect on biofilm formation: (1) a reduction in P. aeruginosa of 7.3 logs (100%); (2) a reduction in S. aureus of 7.3 logs (100%); (3) a reduction in S. maltophilia of 7.5 logs (100%); and (4) a reduction in S. marcescens reduction of 3.3 logs (99.9%). To test the stability of the organoselenium polypropylene contact lens coupon, the coupon was soaked in PBS for eight weeks at room temperature. It was found that when these soaked coupons were tested against S. aureus, complete inhibition (8.1 logs) was obtained. Because organoselenium cannot leach from the polymer, this would imply that the organoselenium polypropylene contact lens case coupon would be inhibitory toward bacterial biofilm for the life of the case. CONCLUSION: The organoselenium polypropylene contact lens case coupon shows the ability to inhibit biofilm formation. The use of organoselenium copolymer should play an important role in protecting against contact lens case-acquired infection.

Sonorheometry Device Thresholds in Liver Transplantation: An Observational Retrospective Study.

BACKGROUND: Liver transplantation (LT) remains a potentially haemorrhagic procedure whose perioperative bleeding and transfusion could be better monitored using point-of-care devices. Quantra® is a device based on sonorheometry to assess whole blood clot formation. Our aims were to describe Quantra® parameters during LT and to study their correlations with standard laboratory parameters, and to determine Quantra® cut-off values for thrombocytopenia, hypofibrinogenemia and coagulation factors' deficit. METHODS: In 34 patients undergoing LT, blood samples were collected before surgical incision, 15 min after the beginning of the anhepatic phase, and 15 min after arterial revascularization of the graft. RESULTS: Clotting time (CT) was well correlated with prothrombin (PT) ratio and activated partial thromboplastin time (aPTT) ratio. Platelet contribution to clot stiffness (PCS) was correlated with platelets (ρ = 0.82, p < 0.001) and fibrinogen contribution clot stiffness (FCS) with fibrinogen (Fg) (ρ = 0.74, p < 0.001). CT predicted a PT ratio < 30% with an area under the curve (AUC) of 0.93 (95% CI 0.87-0.98; p < 0.001). PCS predicted a platelet count < 50 G/L with an AUC of 0.87 (95% CI 0.76-0.98, p < 0.001). FCS predicted a Fg < 1.0, 1.2 or 1.5 g/L, with an AUC of 0.86 (95% CI 0.77-094, p < 0.001), 0.82 (95% CI 0.74-0.91, p < 0.001) and 0.88 (95% CI 0.82-0.95, p < 0.001), respectively. CONCLUSION: Quantra® provides a rapid assessment of haemostasis during LT.

A practical molecular assay to predict survival in resected non-squamous, non-small-cell lung cancer: development and international validation studies.

BACKGROUND: The frequent recurrence of early-stage non-small-cell lung cancer (NSCLC) is generally attributable to metastatic disease undetected at complete resection. Management of such patients depends on prognostic staging to identify the individuals most likely to have occult disease. We aimed to develop and validate a practical, reliable assay that improves risk stratification compared with conventional staging. METHODS: A 14-gene expression assay that uses quantitative PCR, runs on formalin-fixed paraffin-embedded tissue samples, and differentiates patients with heterogeneous statistical prognoses was developed in a cohort of 361 patients with non-squamous NSCLC resected at the University of California, San Francisco. The assay was then independently validated by the Kaiser Permanente Division of Research in a masked cohort of 433 patients with stage I non-squamous NSCLC resected at Kaiser Permanente Northern California hospitals, and on a cohort of 1006 patients with stage I-III non-squamous NSCLC resected in several leading Chinese cancer centres that are part of the China Clinical Trials Consortium (CCTC). FINDINGS: Kaplan-Meier analysis of the Kaiser validation cohort showed 5 year overall survival of 71·4% (95% CI 60·5-80·0) in low-risk, 58·3% (48·9-66·6) in intermediate-risk, and 49·2% (42·2-55·8) in high-risk patients (p(trend)=0·0003). Similar analysis of the CCTC cohort indicated 5 year overall survivals of 74·1% (66·0-80·6) in low-risk, 57·4% (48·3-65·5) in intermediate-risk, and 44·6% (40·2-48·9) in high-risk patients (p(trend)<0·0001). Multivariate analysis in both cohorts indicated that no standard clinical risk factors could account for, or provide, the prognostic information derived from tumour gene expression. The assay improved prognostic accuracy beyond National Comprehensive Cancer Network criteria for stage I high-risk tumours (p<0·0001), and differentiated low-risk, intermediate-risk, and high-risk patients within all disease stages. INTERPRETATION: Our practical, quantitative-PCR-based assay reliably identified patients with early-stage non-squamous NSCLC at high risk for mortality after surgical resection. FUNDING: UCSF Thoracic Oncology Laboratory and Pinpoint Genomics.

The role of stem cells in airway repair: implications for the origins of lung cancer.

Lung cancer is the leading cause of cancer-related deaths worldwide. Recently, advancements in our ability to identify and study stem cell populations in the lung have helped researchers to elucidate the central role that cells with stem cell-like properties may have in lung tumorigenesis. Much of this research has focused on the use of the airway repair model to study response to injury. In this review, we discuss the primary evidence of the role that cancer stem cells play in lung cancer development. The implications of a stem cell origin of lung cancer are reviewed, and the importance of ongoing research to identify novel therapeutic and prognostic targets is reiterated.

Status of ambulatory blood pressure monitoring and home blood pressure monitoring for the diagnosis and management of hypertension in the US: an up-to-date review.

The diagnosis and management of hypertension has been based on the measurement of blood pressure (BP) in the office setting. However, data have demonstrated that BP may substantially differ when measured in the office than when measured outside the office setting. Higher out-of-office BP is associated with increased cardiovascular risk independent of office BP. Ambulatory BP monitoring (ABPM) and home BP monitoring (HBPM) are validated approaches for out-of-office BP measurement. In the 2015 and 2021 United States Preventive Services Task Force (USPSTF) reports on screening for hypertension, ABPM was recommended as the reference standard for out-of-office BP monitoring and for confirming an initial diagnosis of hypertension. This recommendation was based on data from more published studies of ABPM vs. HBPM on the predictive value of out-of-office BP independent of office BP. Therefore, HBPM was recommended as an alternative approach when ABPM was not available or well tolerated. The 2017 American College of Cardiology (ACC)/American Heart Association (AHA) BP guideline recommended ABPM as the preferred initial approach for detecting white-coat hypertension and masked hypertension among adults not taking antihypertensive medication. In contrast, HBPM was recommended as the preferred initial approach for detecting the white-coat effect and masked uncontrolled hypertension among adults taking antihypertensive medication. The current review provides an overview of ABPM and HBPM in the US, including best practices, BP thresholds that should be used for the diagnosis and treatment of hypertension, barriers to widespread use of such monitoring, US guideline recommendations for ABPM and HBPM, and data supporting HBPM over ABPM.

Pain phenotyping and investigation of outcomes in physical therapy: An exploratory study in patients with low back pain.

Phenotypes have been proposed as a method of characterizing subgroups based on biopsychosocial factors to identify responders to analgesic treatments. This study aimed to, first, confirm phenotypes in patients with low back pain receiving physical therapy based on an a priori set of factors used to derive subgroups in other pain populations. Second, an exploratory analysis examined if phenotypes differentiated pain and disability outcomes at four weeks of physical therapy. Fifty-five participants completed psychological questionnaires and pressure pain threshold (PPT). Somatization, anxiety, and depression domains of the Symptom-Checklist-90-Revised, and PPT, were entered into a hierarchical agglomerative cluster analysis with Ward's method to identify phenotypes. Repeated measures ANOVAs assessed pain ratings and disability by phenotype at four weeks. Three clusters emerged: 1) high emotional distress and pain sensitivity (n = 10), 2) low emotional distress (n = 34), 3) low pain sensitivity (n = 11). As an exploratory study, clusters did not differentiate pain ratings or disability after four weeks of physical therapy (p's>0.05). However, trends were observed as magnitude of change for pain varied by phenotype. This supports the characterization of homogenous subgroups based on a protocol conducted in the clinical setting with varying effect sizes noted by phenotype for short-term changes in pain. As an exploratory study, future studies should aim to repeat this trial in a larger sample of patients.

The stress, salt excretion, and nighttime blood pressure (SABRE) study: Rationale and study design.

Background: Abnormal diurnal patterns of blood pressure (BP) on ambulatory BP monitoring (ABPM), defined by reduced BP dipping or elevated nighttime BP, are associated with increased risk for adverse cardiovascular events. Psychological stress is associated with abnormal diurnal patterns of BP. Exposure to an acute stressor (e.g., mental stress task) normally increases urinary sodium excretion. However, some individuals have sodium retention after stress provocation, revealing substantial between-person variability in the degree of stress-induced sodium excretion. Prior research suggests urinary sodium excretion that does not occur during the daytime may shift toward the nighttime, accompanied by an increase in nighttime BP. Associations between psychological stress and the diurnal patterns of sodium excretion and BP are not yet fully understood. Design: The study is conducted in both the laboratory and naturalistic environment with a multi-racial/ethnic sample of 211 healthy adults. In the laboratory, change in urinary sodium excretion in response to mental stress tasks is examined with pre-/post-stress assessments of sodium excretion. Changes in angiotensin-II, catecholamines, BP, heart rate, endothelin-1, and cortisol are also assessed. In the 24-hour naturalistic environment, the diurnal patterns of sodium excretion and systolic BP are assessed as daytime-to-nighttime ratio of sodium excretion and ABPM, respectively. Ecological momentary assessments of perceived stress are also collected. Summary: The SABRE study investigates previously unexplored associations between stress-induced urinary excretion in the laboratory, diurnal patterns of sodium excretion and BP in the naturalistic environment, and ecological stress. It has high potential to advance our understanding of the role of psychological stress in hypertension.

The association between sleep and psychological distress among New York City healthcare workers during the COVID-19 pandemic.

BACKGROUND: Healthcare workers (HCWs) treating patients with COVID-19 report psychological distress. We examined whether disturbed sleep was associated with psychological distress in New York City (NYC) HCWs during the initial peak of the COVID-19 pandemic (April-May 2020). METHODS: HCWs completed a survey screening for acute stress (4-item Primary Care PTSD screen), depressive (Patient Health Questionaire-2), and anxiety (2-item Generalized Anxiety Disorder scale) symptoms. Insomnia symptoms (modified item from the Insomnia Severity Index) and short sleep (SS, sleep duration <6 h/day) were assessed. Poisson regression analyses predicting psychological distress from SS and insomnia symptoms, adjusting for demographics, clinical role/setting, redeployment status, shifts worked, and multiple comparisons were performed. RESULTS: Among 813 HCWs (80.6% female, 59.0% white) mean sleep duration was 5.8 ± 1.2 h/night. Prevalence of SS, insomnia, acute stress, depressive, and anxiety symptoms were 38.8%, 72.8%, 57.9%, 33.8%, and 48.2%, respectively. Insomnia symptoms was associated with acute stress (adjusted prevalence ratio [PR]: 1.51, 95% CI: 1.35, 1.69), depressive (PR: 2.04, 95% CI: 1.78, 2.33), and anxiety (PR: 1.74, 95% CI: 1.55, 1.94) symptoms. SS was also associated with acute stress (PR: 1.17, 95% CI: 1.07, 1.29), depressive (PR: 1.36, 95% CI: 1.233, 1.51), and anxiety (PR: 1.38, 95% CI: 1.26, 1.50) symptoms. LIMITATIONS: Our cross-sectional analysis may preclude the identification of temporal associations and limit causal claims. CONCLUSIONS: In our study, SS and insomnia were associated with psychological distress symptoms in NYC HCWs during the COVID-19 pandemic. Sleep may be a target for interventions to decrease psychological distress among HCWs.

Psychological distress, coping behaviors, and preferences for support among New York healthcare workers during the COVID-19 pandemic.

OBJECTIVE: The mental health toll of COVID-19 on healthcare workers (HCW) is not yet fully described. We characterized distress, coping, and preferences for support among NYC HCWs during the COVID-19 pandemic. METHODS: This was a cross-sectional web survey of physicians, advanced practice providers, residents/fellows, and nurses, conducted during a peak of inpatient admissions for COVID-19 in NYC (April 9th-April 24th 2020) at a large medical center in NYC (n = 657). RESULTS: Positive screens for psychological symptoms were common; 57% for acute stress, 48% for depressive, and 33% for anxiety symptoms. For each, a higher percent of nurses/advanced practice providers screened positive vs. attending physicians, though housestaff's rates for acute stress and depression did not differ from either. Sixty-one percent of participants reported increased sense of meaning/purpose since the COVID-19 outbreak. Physical activity/exercise was the most common coping behavior (59%), and access to an individual therapist with online self-guided counseling (33%) garnered the most interest. CONCLUSIONS: NYC HCWs, especially nurses and advanced practice providers, are experiencing COVID-19-related psychological distress. Participants reported using empirically-supported coping behaviors, and endorsed indicators of resilience, but they also reported interest in additional wellness resources. Programs developed to mitigate stress among HCWs during the COVID-19 pandemic should integrate HCW preferences.

Association between MTHFR 677C-T polymorphism and alcohol dependence according to Lesch and Babor typology.

Prior studies have associated 677C-T Methylenetetrahydrofolate reductase (MTHFR) gene polymorphism with decreased enzymatic activity and modified homocysteine regulation. This study determines and compares MTHFR 677C-T distribution and examines its consequences on homocysteine metabolism and alcohol dependence in alcoholic patients classified according to the Babor and Lesch typologies. MTHFR TT genotype was more prevalent in AD patients with milder alcohol dependence (Babor type A) and with Lesch type 3, associated with depression. MTHFR TT was also associated with hyperhomocysteinemia. Determining MTHFR 677C-T genotype, folate and vitamin B12 levels could assist physicians in identifying type 3 patients and improve addictions management.

[Could the publication of new european guidelines change practices in France?] / La publication au JO de nouveaux règlements européens sur les dispositifs médicaux pourrait-elle changer la pratique du diagnostic oncogénétique en France ?

The use of predictive biomarkers in the diagnosis and prediction of the efficacy of targeted therapies for the individualized management of patients is generally based on the use of in vitro medical diagnosis devices that are now covered by the guidelines 90/385/EEC, 93/42/EEC and 98/42/EEC. On 25 May 2017, the European Parliament and Council Regulations 2017/745 and 2017/746 of 5 April 2017, related to medical devices and in vitro medical diagnosis devices, respectively, were published, disrupting years of practices based on European directives. They tend to bring the in vitro diagnosis in Europe closer to the American regulation in order to improve the use of safety diagnosis tests, while the United States have been changing their practices in the face of biomedical, technological and digital evolutions. We will describe the different regulations of diagnostic tests and discuss their applications in the field of oncology.

Several clock genes polymorphisms are meaningful risk factors in the development and severity of cannabis addiction.

Circadian rhythms have been related to psychiatric diseases and regulation of dopaminergic transmission, especially in substance abusers. The relationship between them remained enigmatic and no data on the role of clock genes on cannabis dependence have been documented. We aimed at exploring the role of clock gene genotypes as potential predisposing factor to cannabis addiction, using a high throughput mass spectrometry methodology that enables the large-scale analysis of the known relevant polymorphisms of the clock genes. We have conducted a case-control study on 177 Caucasians categorizing between cannabis-addicted subjects and casual consumers based on structured interviews recorded socio-demographic data, AUDIT, Fagerström test, MINI, and medical examinations. Alcohol, opiates, and stimulants' consumption was as exclusion criteria. We report an association between several Single Nucleotide Polymorphism (SNP)s in main circadian genes SNPs, especially the gene locus HES7/PER1 on chromosome 17 and cannabis consumption as well as the development of neuropsychiatric and social disorders. This SNP's signature that may represent a meaningful risk factor in the development of cannabis dependence and its severity requires to be deeply explored in a prospective study.

Protective effect against alcohol dependence of the thermolabile variant of MTHFR.

BACKGROUND: Hyperhomocysteinemia is frequently observed in alcohol-dependent subjects, in particularly in those with marked withdrawal symptoms. The common C677T transition on the methylenetetrahydrofolate reductase (MTHFR) gene influences homocysteinemia. Our objective was to study the prevalence of the MTHFR C677T polymorphism in alcohol-dependent subjects and the influence of this polymorphism on symptoms associated with alcoholism. METHODS: MTHFR C677T polymorphism was determined in 93 control subjects and 242 alcohol-dependent subjects. Serum homocysteine, folate and vitamin B12 levels together with hepatic biological parameters were determined in the control and alcohol-dependent subjects. RESULTS: Hyperhomocysteinemia is frequently observed in alcohol-dependent subjects, particularly in those with marked withdrawal symptoms. Alcohol-dependent subjects showed a significant decrease in MTHFR 677TT prevalence (9%, 21/242) compared to controls (18%, 17/93) (p<0.02). The relative risk estimated as an odds ratio for alcoholism in subjects with the TT genotype is 0.42 (odd ratio 95% confidence interval, 0.21-0.83). Moreover, drinkers with TT genotype presented lower values for markers of alcohol misuse (p<0.05), better liver function tests, a lower frequency of relapses and no marked withdrawal symptoms as assessed by the Lesch typology. CONCLUSION: MTHFR 677TT genotype could play a protective role against alcohol dependence. Moreover, when subjects with MTHFR 677TT genotype become dependent to alcohol, they seem to constitute a subgroup of alcoholic patients with a decreased risk for developing neurotoxic withdrawal symptoms and hepatic toxicity.

Scaling of lactate threshold by peak oxygen uptake and by fat-free mass 0 x 67.

The lactate threshold (LT) represents the onset of metabolic acidosis during cardiopulmonary exercise testing (CPET). It is measured as a O(2) in the units of ml min(-1). In order to make comparisons among subjects, LT is often scaled or normalized by O(2) peak resulting in the LT/O(2) peak ratio. Ratio variables have underlying assumptions. One assumption is that the relationship between the numerator and denominator is linear with a zero y-intercept. If the relationship has a positive y-intercept, then the ratio will decrease with increasing values of the scaling variable thereby penalizing subjects with larger values of the scaling variable. Our purpose was to examine the validity of scaling LT by O(2) peak and by fat-free mass raised to 0 x 67 power (FFM(0 x 67)) as dimensional analysis predicts that LT is proportional to FFM(0 x 67). Cycle ergometer CPET was administered to 204 healthy, sedentary subjects (103 males) to the limit of tolerance. Lactate threshold was estimated noninvasively using the V-slope technique. Fat-free mass was assessed by skinfolds. The relationship of LT versus O(2) peak was linear with a positive y-intercept for both sexes. Consequently, the LT/O(2) peak ratio decreased as O(2) peak increased for both sexes. The relationship of LT versus FFM(0 x 67)was linear with a zero y-intercept for both sexes. Consequently, the plot of the LT/FFM(0 x 67) ratio versus FFM resulted in a straight line with a slope of zero for both sexes. The results of this study support the conclusion that FFM(0 x 67), but not O(2) peak, is a valid scaling variable for LT.

Reliability and validity of the lung volume measurement made by the BOD POD body composition system.

The BOD POD Body Composition System uses air-displacement plethysmography to measure body volume. To correct the body volume measurement for the subject's lung volume, the BOD POD utilizes pulmonary plethysmography to measure functional residual capacity (FRC) at mid-exhalation as that is the subject's lung volume during the body volume measurement. Normally, FRC is measured at end-exhalation. The BOD POD FRC measurement can be corrected to an end-exhalation volume by subtracting approximately one-half of the measured tidal volume. Our purpose was to determine the reliability and validity of the BOD POD FRC measurement at end-exhalation. Ninety-two healthy adults (half female) underwent duplicate FRC measurements by the BOD POD and one FRC measurement by a traditional gas dilution technique. The latter method was used as the reference method for the validity component of the study. The order of the FRC measurements by the two methods was randomized. The test-retest correlation coefficients for the duplicate BOD POD FRC measurements for the male and female subjects were 0.966 and 0.948, respectively. The mean differences between the BOD POD FRC trial #1 measurement and gas dilution FRC measurement for the male and female subjects were -32 and -23 ml, respectively. Neither difference was statistically significant. The correlation coefficients for these two measurements in the male and female subjects were 0.925 and 0.917, respectively. Based on these results, we conclude that the BOD POD FRC measurement in healthy males and females is both reliable and valid.

Comparison of three methods for detection of the lactate threshold.

The lactate threshold (LT) represents the onset of a metabolic acidosis during graded exercise testing (GXT). It is a valuable measurement in clinical exercise testing and correlates well with endurance performance. Our purpose was to compare three LT detection methods, namely, Inspection (work rate at onset of a systematic increase in blood lactate concentration determined by inspection of blood lactate versus work rate plot), 0.5 mM (work rate which just precedes a rise in blood lactate concentration of >0.5 mM) and log-log (work rate at the intersection of two linear lines in plot of log lactate versus log work rate where the residual sum of squares for both lines added together is minimized). Fourteen subjects underwent cycle ergometer GXT with blood samples obtained at the end of each 3-min work rate increment and analysed for lactate concentration. The mean +/- 95% confidence limits of work rates at LT for the Inspection, 0.5 mM and log-log methods were 104.5 +/- 28.0, 103.2 +/- 28.1 and 105.1 +/- 27.3 W, respectively. Repeated-measures analysis of variance yielded a non-significant F ratio. The Bland-Altman bias +/- 95% limits of agreement for Inspection versus 0.5 mM, Inspection versus log-log and 0.5 mM versus log-log were 1.3 +/- 20.6, -0.6 +/- 12.5 and -1.9 +/- 20.5 W, respectively. The intraclass correlation coefficients for Inspection versus 0.5 mM, Inspection versus log-log and 0.5 mM versus log-log were 0.978, 0.992 and 0.977, respectively. The results of this study suggest that all three methods detect the LT at the same work rate.

Maximal oxygen uptake at the same fat-free mass is greater in men than women.

Maximal oxygen uptake (VO(2max)) is commonly divided by body mass or fat-free mass (body mass minus fat mass) in order to make it size independent so that comparisons among persons of different size can be made. However, numerous studies have shown that the ratio created is not size-independent. Analysis of covariance (ANCOVA) allows a dependent variable to be compared between groups at a common value of a covariate. The purpose of this study was to compare VO(2max) at the same fat-free mass (FFM) in 230 sedentary subjects (half men) who ranged in age from 20 to 70 years. The subjects underwent maximal cardiopulmonary exercise testing on a cycle ergometer as ventilation and the expired gas fractions were being measured. Two ANCOVA models were evaluated. The dependent variable, fixed factor and covariate(s) in the linear model were VO(2max), sex and FFM, respectively. The corresponding terms in the log-linear model were ln VO(2max), sex, and ln FFM and age. Sex made a significant contribution to both models. In the linear model, the mean VO(2max) at the same FFM was 27% higher in men (2,444 versus 1,929 ml min(-1); P<0.001). In the log-linear model, the corresponding value at the same FFM and age was 32% higher in men (2,368 versus 1,794 ml min(-1); P<0.001). The goodness of fit indices of squared multiple correlation coefficient and standard error of estimate were significantly better for the log-linear model. We conclude that VO(2max) at the same FFM is considerably higher in men than in women who have a sedentary lifestyle.

Is ventilatory efficiency dependent on the speed of the exercise test protocol in healthy men and women?

Indices of ventilatory efficiency have proven useful in assessing patients with heart and lung disease. One of these indices is the slope of the ventilation (V(E)) versus carbon dioxide output (VCO(2)) relationship during cardiopulmonary exercise testing (CPET) for work rates where the relationship is linear. However, this relationship is defined not only by the slope but also by the y-intercept. To examine whether this relationship is dependent on the speed of the CPET protocol, 30 healthy subjects (16 males) were administered a rapid CPET with 1-min increment duration (1-min CPET) to the limit of tolerance and a slow CPET with 4-min increment duration (4-min CPET) to the lactate threshold. Ventilation and the gas fractions for oxygen and CO(2) were measured with a Vacumed metabolic cart. The average increment size of both protocols for both sexes was not significantly different (P>0.05). For the males, the mean (SD) slope for the 1- and 4-min CPET was 20.12 (2.61) and 20.37 (2.41), respectively. The corresponding values for the y-intercept were 4..89 (2.08) and 5..10 (2.00) l min(-1). For the females, the mean (SD) slope for the 1- and 4-min CPET was 23.90 (2.38) and 24.16 (2.55), respectively. The corresponding values for the y-intercept were 3.93 (0.39) and 3.77 (0.71) l min(-1). Paired t-test analysis demonstrated for both sexes that the slopes and y-intercepts were not different for the two protocols (P>0.05). The results of this study demonstrate that the V(E) versus VCO(2) relationship is not dependent on the speed of the CPET protocol.

Test-retest reliability for two indices of ventilatory efficiency measured during cardiopulmonary exercise testing in healthy men and women.

The level of ventilation (VE)) at a given carbon dioxide output (CO2) determines ventilatory efficiency. During cardiopulmonary exercise testing (CPET), ventilatory efficiency can be measured as the slope of the (VE) versus VCO2 relationship or the lowest VE/VCO2. We evaluated the test-retest reliability of these two ventilatory efficiency indices in 29 healthy subjects (14 males). Each subject performed duplicate cycle ergometer tests on different days. Ventilation and the gas fractions for oxygen and CO2 were measured with a Vacumed metabolic cart. Linear regression analysis of the VE versus VCO2 slope for the duplicate tests in the males, females, and both sexes combined yielded correlation coefficients of 0.822, 0.942, and 0.910, respectively. The corresponding correlation coefficients for the lowest VE/VCO2 were 0.745, 0.929, and 0.884. A comparison of the test-retest correlation coefficients between the two ventilatory efficiency measures for the men, women, and both sexes combined revealed that they were not significantly different and, for a given index, there were no sex differences. The bias (mean of difference scores between tests) and 95% limits of agreement for the VE versus VCO2 slope in the males, females, and both sexes combined were -0.05 +/- 2.41, -0.57 +/- 1.92, and -0.32 +/- 2.20, respectively. The bias and 95% limits of agreement for the lowest VE/VCO2 were very similar with values of 0.06 +/- 2.45, -0.22 +/- 2.03, and -0.10 +/- 2.27. We conclude that the test-retest reliability for the VE versus VCO2 slope and the lowest VE/VCO2 is the same and that there is no sex difference in reliability for either index of ventilatory efficiency.