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  • An assessment of central-peripheral ventilatory chemoreflex interaction using acid and bicarbonate infusions in humans.

    3 July 2018

    1. The object of this study was to investigate the effect of central chemoreceptor stimulation on the ventilatory responses to peripheral chemoreceptor stimulation. 2. The level of central chemoreceptor stimulation was varied by performing experiments at two different levels of end-tidal CO2 pressure (PCO2). Variations in peripheral chemoreceptor stimulus were achieved by varying arterial pH (at constant end-tidal PCO2) and by varying end-tidal O2 pressure (PO2). 3. Two protocols were each performed on six human subjects. In one protocol ventilatory measurements were made during eucapnia, when the arterial pH was lowered from 7.4 to 7.3. The variation in pH was achieved by the progressive infusion of acid (0.1 M HCl). In the other protocol ventilatory measurements were made during hypercapnia, when the arterial pH was increased from 7.3 to 7.4. The variation in pH was achieved by the progressive infusion of 1.26% NaHCO3. In each protocol ventilatory responses were measured during euoxia (end-tidal PO2, 100 Torr), hypoxia (end-tidal PO2, 50 Torr) and hyperoxia (end-tidal PO2, 300 Torr), with end-tidal PCO2 held constant. 4. The increase in ventilatory sensitivity to arterial pH induced by hypoxia (50 Torr) was not significantly different between protocols (acid protocol, -104 +/- 31 l min-1 (pH unit)-1 vs. bicarbonate protocol, -60 +/- 44 l min-1 (pH unit)-1; mean +/- S.E.M.; not significant (n.s.)). The ventilatory sensitivity to hypoxia at an arterial pH of 7.35 was not significantly different between protocols (acid protocol, 14.7 +/- 3.3 l min-1 vs. bicarbonate protocol, 15.6 +/- 2.4 l min-1; mean +/- S.E.M.; n.s.). The results provide no evidence to suggest that peripheral chemoreflex ventilatory responses are modulated by central chemoreceptor stimulation.

  • Independent validation of the prolonged length of stay score.

    3 July 2018

    BACKGROUND: The prolonged length of stay (PLOS) score has recently been derived and validated in 2 independent national cohorts of acute stroke patients in Israel. The present study aimed to determine the performance of the PLOS score in an independent population-based cohort of stroke patients in a health care system considerably different from that in which the score was derived. METHODS: The study was performed on all 434 patients with ischemic stroke or intracerebral hemorrhage hospitalized during the first 5 years of the population-based Oxford Vascular Study (OXVASC) in Oxfordshire, UK. Median (interquartile range) length of stay (LOS) and rates of LOS ≥7 days and LOS ≥30 days by the PLOS score were calculated. Model discrimination was assessed by the c-statistic and goodness of fit was evaluated with the Hosmer-Lemeshow test. RESULTS: Median LOS and rates of LOS ≥7 days increased with the increase in PLOS score among all inpatients and hospital survivors. In the analysis of LOS ≥7 days, the PLOS c-statistic (95% CI) was 0.676 (0.618-0.734) for all inpatients and 0.722 (0.664-0.779) for hospital survivors. Findings were similar for LOS ≥30 days. The Hosmer-Lemeshow showed good calibration. CONCLUSIONS: The PLOS score successfully predicted PLOS in the OXVASC population of acute stroke patients. Although the score was originally derived for the prediction of prolonged acute hospitalization, it successfully predicted prolonged total LOS.

  • Effect of body size on operative risk of carotid endarterectomy.

    3 July 2018

    Many studies have found that women have a higher risk of perioperative stroke or death from carotid endarterectomy. Other vascular surgical procedures have demonstrated that body size and morphology impact on operative risk. We correlated the 30 day operative risk of stroke and death in the European Carotid Surgery Trial (ECST) with height, weight, body surface area (BSA), and body mass index using single variable analyses and multivariable logistic regression. Women were at significantly higher risk of perioperative stroke and death in the ECST. Both height and BSA confounded the effect of sex, implying that the generally smaller size of women may contribute to their increased risk. This finding should be validated in other large datasets.