On C*-algebras generated by pairs of q-commuting isometries

We consider the C*-algebras O_2^q and A_2^q generated, respectively, by isometries s_1, s_2 satisfying the relation s_1^* s_2 = q s_2 s_1^* with |q| < 1 (the deformed Cuntz relation), and by isometries s_1, s_2 satisfying the relation s_2 s_1 = q s_1 s_2 with |q| = 1. We show that O_2^q is isomorphic to the Cuntz-Toeplitz C*-algebra O_2^0 for any |q| < 1. We further prove that A_2^{q_1} is isomorphic to A_2^{q_2} if and only if either q_1 = q_2 or q_1 = complex conjugate of q_2. In the second part of our paper, we discuss the complexity of the representation theory of A_2^q. We show that A_2^q is *-wild for any q in the circle |q| = 1, and hence that A_2^q is not nuclear for any q in the circle.Comment: 18 pages, LaTeX2e "article" document class; submitted. V2 clarifies the relationships between the various deformation systems treate

The prevalence of obstructive sleep apnea-hypopnea syndrome-related symptoms and their relation to airflow limitation in an elderly population receiving home care

Background: Both airflow limitation and obstructive sleep apnea-hypopnea syndrome (OSAHS)-related symptoms are most prevalent in the elderly population. Previous studies revealed significant associations between OSAHS-related symptoms and obstructive airway diseases in the general population. However, other studies showed that the frequency of OSAHS-related symptoms in patients with obstructive airway diseases decreases after the age of 60 and older. Aims: To investigate the prevalence of OSAHS-related symptoms (snoring, breathing pauses, and excessive daytime sleepiness [EDS]) and their relations to airflow limitation, for people over 65 years old. Methods: A full screening spirometry program was performed in a total of 490 aging participants (mean age 77.5 years – range 65–98) who were attending 16 home care settings in central Greece. Airflow limitation was assessed according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) spirometric criteria (FEV1/FVC ,70%). The Berlin Questionnaire and the Epworth Sleepiness Scale were used to screen individuals for OSAHS-related symptoms. Bivariate associations were described using odds ratio (OR) with 95% confidence intervals (CI). Results: Airflow limitation prevalence was 17.1% (male 24.2% and female 9.9%) and was strongly related to male gender and smoking status. The prevalence rates of frequent snoring, breathing pauses, and EDS were 28.1%, 12.9%, and 11.6%, respectively. However, participants with airflow limitation were less likely to report breathing pauses, frequent snoring, EDS, and obesity. Finally, frequent snoring was significantly more common in males than females. Conclusion: This study revealed decreased frequency of OSAHS-related symptoms in participants with airflow limitation suggesting that OSAHS-related symptoms and airflow limitation are not related in our elderly population

The use of cardiopulmonary exercise testing in identifying the presence of obstructive sleep apnea syndrome in patients with compatible symptomatology

© 2019 The aim of this study was to investigate the relationship between cardiopulmonary exercise testing (CPET) and the presence of obstructive sleep apnea syndrome (OSAS) in order to provide an innovative tool to identify patients with OSAS. A prospective nested case control design was adopted. A consecutive population of male volunteers referred to a Sleep Unit was subjected to nocturnal polysomnography, full lung function testing and maximal CPET. A stepwise linear discriminant function analysis (DFA) was applied to construct a model which could identify individuals with moderate-to-severe OSAS from healthy controls. The total of 30 volunteers formed the OSAS and 24 the non-OSAS groups. Demographic and somatometric parameters were similar between groups. Patients presented with lower Expiratory Reserve Volume (ERV: 106.7 ± 28.3 vs. 123.9 ± 22.1, p < 0.001), Leg Fatigue Borg scale (3.9 ± 1.1 vs. 6.1 ± 1.4, p < 0.001), VO 2peak (25.0 ± 5.9 vs. 32.9 ± 7.2 ml/kg −1 /min −1 , p < 0.001), peak breathing frequency (31.0 ± 5.8 vs. 35.5 ± 7.3 1/min −1 , p < 0.001) and peak heart rate (151.1 ± 17.7 vs. 171.2 ± 12.6 beats/min −1 , p < 0.001) compared to controls, but higher peak end-tidal CO 2 (P ET CO 2peak :38.6 ± 4.2 vs. 35.0 ± 4.9 mmHg, p = 0.043) and peak systolic (SBP:188.3 ± 21.9 vs. 173.1 ± 17.9 mmHg, p = 0.009) and diastolic (DBP: 91.3 ± 8.2 vs. 85.4 ± 8.2 mmHg, p = 0.011) blood pressure. Stepwise DFA indicated that ERV % of predicted (0.372), P ET CO 2peak (−0.376), SpO 2resting (0.0667), Leg Fatigue Borg scale (0.564), HR peak (0.530) and DBP peak (−0.543) could separate the two groups, with an overall predictive accuracy of 96.3%. Selected CPET parameters (ERV % of predicted , P ET CO 2peak , SpO 2resting , HR peak , DBP peak and Leg Fatigue Borg Scale ) are independently associated with OSAS presence and could discriminate patients with and without this disorder.Published versio

MRC chronic Dyspnea Scale: Relationships with cardiopulmonary exercise testing and 6-minute walk test in idiopathic pulmonary fibrosis patients: a prospective study

<p>Abstract</p> <p>Background</p> <p>Exertional dyspnea is the most prominent and disabling feature in idiopathic pulmonary fibrosis (IPF). The Medical Research Chronic (MRC) chronic dyspnea score as well as physiological measurements obtained during cardiopulmonary exercise testing (CPET) and the 6-minute walk test (6MWT) are shown to provide information on the severity and survival of disease.</p> <p>Methods</p> <p>We prospectively recruited IPF patients and examined the relationship between the MRC score and either CPET or 6MWT parameters known to reflect physiologic derangements limiting exercise capacity in IPF patients</p> <p>Results</p> <p>Twenty-five patients with IPF were included in the study. Significant correlations were found between the MRC score and the distance (r = -.781, p < 0.001), the SPO₂at the initiation and the end (r = -.542, p = 0.005 and r = -.713, p < 0.001 respectively) and the desaturation index (r = .634, p = 0.001) for the 6MWT; the MRC score and <it>V</it>O₂peak/kg (r = -.731, p < 0.001), SPO₂at peak exercise (r = -. 682, p < 0.001), VE/VCO₂slope (r = .731, p < 0.001), VE/VCO₂at AT (r = .630, p = 0.002) and the Borg scale at peak exercise (r = .50, p = 0.01) for the CPET. In multiple logistic regression analysis, the only variable independently related to the MRC is the distance walked at the 6MWT.</p> <p>Conclusion</p> <p>In this population of IPF patients a good correlation was found between the MRC chronic dyspnoea score and physiological parameters obtained during maximal and submaximal exercise testing known to reflect ventilatory impairment and exercise limitation as well as disease severity and survival. This finding is described for the first time in the literature in this group of patients as far as we know and could explain why a simple chronic dyspnea score provides reliable prognostic information on IPF.</p

Fractional exhaled nitric oxide: where there is smoke, there is fire

[No abstract available