Given a passage, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Hypoxemia is a common complication of chronic obstructive pulmonary disease and a major factor in patients' prognosis and quality of life. The response to exercise has been evaluated by various means but no standardization has been accepted.", 'To suggest a simple outpatient technique for evaluating the response of arterial oxygen saturation to exercise for use as a marker of disease severity.', 'Ninety-six patients with various degrees of COPD were divided into three groups: mild (forced expiratory volume in 1 sec > 65%), moderate (FEV1 between 50 and 65%), and severe (FEV1 < 50%). Using continuous oximeter recording we measured oxygen saturation during 15 steps of climbing, and quantified oxygen desaturation by measuring the "desaturation area," defined as the area under the curve of oxygen saturation from the beginning of exercise through the lowest desaturation point and until after recovery to the baseline level of oxygen percent saturation. Desaturation was correlated to spirometry, lung gas volumes, blood gas analysis, and 6 min walking distance.', 'A good correlation was found between severity of COPD and baseline SaO2, lowest SaO2, recovery time, and desaturation area. A negative correlation was found between desaturation area and FEV1 (r = -0.65), FEV1/forced vital capacity (r = -0.58), residual volume to total lung capacity (r = 0.52), and diffusing lung capacity for carbon monoxide (r = -0.52). In stepwise multiple regression analysis only FEV1 correlated significantly to desaturation area. A good correlation was noted between 6 min walking distance and desaturation area with the 15 steps technique (r = 0.56).
Do quantitative 15 steps exercise oximetry as a marker of disease severity in patients with chronic obstructive pulmonary disease?

Bilateral lower extremity venous duplex scanning for acute deep venous thrombosis (DVT) has been advocated because of the high incidence of occult contralateral leg involvement. We investigated the clinical necessity of such a policy.', 'The results from 2996 venous duplex studies performed during the past 2 years were retrospectively reviewed. A total of 1694 of these scans were performed on patients with symptoms, of whom 248 (15%) were found to have an acute DVT. Symptoms were limited to one side in 198 patients, whereas bilateral complaints were noted in 50 patients.', 'Among the patients with symptoms of acute DVT, 72 (29%) had bilateral involvement. Bilaterality was more likely in patients with bilateral symptoms than in those with only unilateral symptoms (56% vs 22%; p < 0.005). Of the patients with unilateral symptoms and bilateral DVT, all of them had either acute (80%) or acute and chronic (20%) thrombosis in the symptomatic leg. The contralateral asymptomatic limb had fewer acute and more chronic DVT (41% and 55%, respectively). No patient from the entire group admitted with symptoms had an acute DVT in the asymptomatic limb without a concomitant acute DVT in the symptomatic leg. Unilateral scanning would decrease the examination time by 21% and potentially increase total reimbursement for symptomatic venous scans by 9% compared with routine bilateral duplex scanning.
Is contralateral duplex scanning for deep venous thrombosis unnecessary in patients with symptoms?

Elevated intraocular pressure (IOP) is the only known modifiable risk factor for primary open angle glaucoma (POAG), and it can be caused by reduced aqueous humor outflow from the anterior chamber. Outflow is predominantly regulated by the trabecular meshwork, consisting of specialized cells within a complex extracellular matrix (ECM). An imbalance between ECM-degrading matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs) within the trabecular meshwork is thought to contribute to POAG. This study aimed to quantify levels of TIMPs and MMPs in aqueous humor samples from glaucomatous and non-glaucomatous eyes, analyze MMP/TIMP ratios, and correlate results with age, IOP, and Humphrey's visual field pattern standard deviation (PSD).", "Aqueous humor samples were collected from 26 non-glaucomatous control subjects before cataract surgery and 23 POAG patients undergoing trabeculectomy or cataract surgery. Analyte concentrations were measured using multiplexed immunoassays. Statistical significance was assessed with Mann-Whitney U tests, and Spearman's method was used to assess correlations with age, IOP, and PSD.", 'Concentrations of TIMP1 (p = 0.0008), TIMP2 (p = 0.002), TIMP4 (p = 0.002), and MMP2 (p = 0.020) were significantly increased in aqueous humor samples from POAG versus cataract samples. For the majority of MMP/TIMP molar ratios calculated for the cataract group, TIMPs outweighed MMPs. In POAG, molar ratios of MMP2/TIMP1 (p = 0.007) and MMP9/TIMP1 (p = 0.005) showed a significant decrease, corresponding to an elevated excess of TIMPs over MMPs in POAG compared to cataract samples. Conversely, MMP2/TIMP3 (p = 0.045) and MMP3/TIMP3 (p = 0.032) molar ratios increased. Several MMP/TIMP molar ratios correlated with IOP (r = 0.476-0.609, p = 0.007-0.034) and PSD (r = -0.482 to -0.655, p = 0.005-0.046) in POAG samples and with age in cataract control samples.
Are tIMP1 , TIMP2 , and TIMP4 increased in aqueous humor from primary open angle glaucoma patients?