Oropharyngeal Oxygen Concentration Is Dependent on the Oxygen Mask System and Sampling Location.

BACKGROUND: Numerous oxygen delivery systems are used to treat hypoxemia. It is unknown if FIO2 at the lips predicts oropharyngeal FIO2 for various oxygen mask systems. We tested whether FIO2 measurements differed between the lips and oropharynx, and whether this difference depends on the mask system. METHODS: Ten healthy volunteers had one sampling catheter positioned at the lips and another catheter in the oropharynx. FIO2 was sampled at each location while the subjects breathed normal tidal volumes with oxygen at 15 L/min via 4 delivery devices: a simple mask, a non-rebreather mask, a face mask with a diffuser that concentrates and directs O2 toward the mouth and nose (mask with diffuser), and a closed mask with a Jackson-Rees circuit. Data were analyzed by using a linear mixed model to account for subject crossover in the repeated measures design. RESULTS: FIO2 levels differed significantly for the 4 delivery mask systems (P < .001) and by sampling catheter location (P < .001). Differences in mean FIO2 between the lips and the oropharynx were observed for the mask with diffuser (difference 0.30, 95% CI 0.25-0.36; P < .001), and non-rebreather mask (difference 0.09, 95% CI 0.04-0.15; P = .001). The mean FIO2 at the oropharynx was highest for the closed mask (0.97, 95% CI 0.92-1.00), followed by the non-rebreather mask (0.76, 95% CI 0.72-0.81), simple mask (0.62, 95% CI 0.58-0.67), and the mask with diffuser (0.51, 95% CI 0.46-0.56). At the lips, the mean FIO2 was highest for the closed mask (0.97, 95% CI 0.92-1.00), followed by the non-rebreather mask (0.86, 95% CI 0.81- 0.90), OxyMask (0.81, 95% CI 0.76-0.86), and simple mask (0.67, 95% CI 0.62-0.71). CONCLUSIONS: With high oxygen flows and normal tidal volume breathing, FIO2 measurements obtained at the oropharynx or at the lips depended on the device used, with the mask with diffuser showing the most significant discrepancies. FIO2 measures at the oropharynx and the lips were only consistent for the closed mask system. (ClinicalTrials.gov registration NCT02523586.).

Blood Type O is not associated with increased blood loss in extensive spine surgery.

STUDY OBJECTIVE: To investigate whether Type O blood group status is associated with increased intraoperative blood loss and requirement of blood transfusion in extensive spine surgery. DESIGN: Retrospective comparative study. SETTING: University-affiliated, non-profit teaching hospital. MEASUREMENTS: Data from 1,050 ASA physical status 1, 2, 3, 4, and 5 patients who underwent spine surgeries involving 4 or more vertebral levels were analyzed. Patients with Type O blood were matched to similar patients with other blood types using propensity scores, which were estimated via demographic and morphometric data, medical history variables, and extent of surgery. Intraoperative estimated blood loss (EBL) was compared among matched patients using a linear regression model; intraoperative transfusion requirement in volume of red blood cells, fresh frozen plasma, platelet, cryoprecipitate, cell salvaged blood, volume of intraoperative infusion of hetastarch, 5% albumin, crystalloids, and hospital length of hospital (LOS) were compared using Wilcoxon rank-sum tests. MAIN RESULTS: Intraoperative EBL and requirement of blood product transfusion were similar in patients with Type O blood group and those with other blood groups. CONCLUSION: There was no association between Type O blood and increased intraoperative blood loss or blood transfusion requirement during extensive spine surgery, with similar hospital LOS in Type O and non-O patients.

The influence of RGD-bearing hydrogels on the re-expression of contractile vascular smooth muscle cell phenotype.

This study reports on the ability of poly(ethylene glycol) diacrylate (PEGDA) hydrogel scaffolds with pendant integrin-binding GRGDSP peptides (RGD-gels) to support the re-differentiation of cultured vascular smooth muscle cells (SMCs) toward a contractile phenotype. Human coronary artery SMCs were seeded on RGD-gels, hydrogels with other extracellular matrix derived peptides, fibronectin (FN) and laminin (LN). Differentiation was induced on RGD-gels with low serum medium containing soluble heparin, and the differentiation status was monitored by mRNA expression, protein expression, and intracellular protein organization of the contractile smooth muscle markers, smooth muscle alpha-actin, calponin, and SM-22alpha. RGD-gels supported a rapid induction (2.7- to 25-fold up-regulation) of SMC marker gene mRNA, with expression levels that were equivalent to FN and LN controls. Marker protein levels mirrored the changes in mRNA expression, with levels on RGD-gels indistinguishable from FN and LN controls. Furthermore, these markers co-localized in stress fibers within SMCs on RGD-gels suggesting the recapitulation of a contractile apparatus within the cells. These results indicate that SMCs cultured on RGD-bearing hydrogels can re-differentiate toward a contractile phenotype suggesting this material is an excellent candidate for further development as a bioactive scaffold that regulates SMC phenotype.