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- Çinar, O.Y., et al.
(författare)
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Jet pipe reflections - Influence of geometrical and flow exit conditions
- 2010
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Ingår i: 16th AIAA/CEAS Aeroacoustics Conference (31st AIAA Aeroacoustics Conference). - 9781600867446 ; , s. 2010-4013-
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the influence of the exit conditions on the acoustic reflections at a jet pipe opening. For the flow exit conditions, the model of Munt assuming a vortex sheet at the exit of a semi-infinite jet pipe is improved by considering more general coupling conditions. We focus on modelling the acoustic properties at the shear layer in general and the stability properties in particular. Experimental methods are used for studying primarily the geometric exit conditions. Both theoretical and experimental results are presented and discussed. Numerical results related to the theory show that the thickness of the shear layer causes an expected increase in the magnitude of the reflection coefficient compared to the original infinitely thin shear layer in the Munt model. The experimental results, on the other hand, show that there are additional effects due to the presence of thick walls at the exit of the straight pipes used in the experiments. These effects are observed to be more dominant than the effects due to the shape of the edges. Based on the discussions, further theoretical and experimental investigations are proposed.
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- Cinar, C., et al.
(författare)
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Determinants of Severe Nocturnal Hypoxemia in Adults with Chronic Thromboembolic Pulmonary Hypertension and Sleep-Related Breathing Disorders
- 2023
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Ingår i: Journal of Clinical Medicine. - 2077-0383. ; 12:14
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: We aimed to investigate the occurrence of sleep-related breathing disorders (SRBDs) in patients with chronic thromboembolic pulmonary hypertension (CTEPH) and addressed the effect of pulmonary hemodynamics and SRBD indices on the severity of nocturnal hypoxemia (NH). Methods: An overnight polysomnography (PSG) was conducted in patients with CTEPH, who were eligible for pulmonary endarterectomy. Pulmonary hemodynamics (mean pulmonary arterial pressure (mPAP), pulmonary arterial wedge pressure (PAWP), pulmonary vascular resistance (PVR) measured with right heart catheterization (RHC)), PSG variables (apnea-hypopnea index (AHI)), lung function and carbon monoxide diffusion capacity (DLCO) values, as well as demographics and comorbidities were entered into a logistic regression model to address the determinants of severe NH (nocturnal oxyhemoglobin saturation (SpO(2)) < 90% under >20% of total sleep time (TST)). SRBDs were defined as obstructive sleep apnea (OSA; as an AHI & GE; 15 events/h), central sleep apnea with Cheyne-Stokes respiration (CSA-CSR; CSR pattern & GE; 50% of TST), obesity hypoventilation syndrome (OHS), and isolated sleep-related hypoxemia (ISRH; SpO(2) < 88% under >5 min without OSA, CSA, or OHS). Results: In all, 50 consecutive patients (34 men and 16 women; mean age 54.0 (SD 15.1) years) were included. The average mPAP was 43.8 (SD 16.8) mmHg. SRBD was observed in 40 (80%) patients, of whom 27 had OSA, 2 CSA-CSR, and 11 ISRH. None had OHS. Severe NH was observed in 31 (62%) patients. Among the variables tested, age (odds ratio (OR) 1.08, 95% confidence interval [CI] 1.01-1.15; p = 0.031), mPAP (OR 1.11 [95% CI 1.02-1.12; p = 0.012]), and AHI (OR 1.17 [95% CI 1.02-1.35; p = 0.031]) were independent determinants of severe NH. Conclusions: Severe NH is highly prevalent in patients with CTEPH. Early screening for SRBDs and intervention with nocturnal supplemental oxygen and/or positive airway pressure as well as pulmonary endarterectomy may reduce adverse outcomes in patients with CTEPH.
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