The Valsalva maneuver revisited by wavelets

The Valsalva maneuver is an autonomic test that evokes short sharp cardiovascular fluctuations mediated by the autonomic nervous system. Numerous spectral analysis methods have been proposed to analyze biological signals. When applied to heart rate (HR) variability, two major bands related to autonomic influence have been defined: LF (mainly sympathetic) and HF (parasympathetic). However, conventional spectral approaches are based on the assumption of stationarity, and most require at least five minutes of recording. These two requirements cannot be fulfilled when analysis of dynamic processes such as the regulatory action of the autonomic nervous system is required. Wavelet transform is a mathematical tool that, by determining the temporal localization of the changes, the frequencies involved and their contribution to the entire signal, overcomes the limitations imposed by conventional methods. In the present work, we use wavelets to evaluate autonomic influence through the LF and HF band powers on acute changes in systolic blood pressure (sBP) and RR intervals (RRI) during the Valsalva maneuver. Eighteen healthy volunteers performed the maneuver by blowing, after a deep inspiration and with a closed glottis, against a pressure of 40 mmHg for 15 seconds. Data were analyzed in three different periods: 1) the last minute just prior to the test (CTR); 2) the 15 seconds of the Valsalva maneuver (VM); 3) during the next 35 seconds after the maneuver (aVM). We observed that LF power increased in sBP and RRI in both VM and ower only increased after Valsalva. The data showed a marked increase in sympathetic activity during and after the maneuver and an increase in parasympathetic outflow after aVM. In conclusion, the ability of wavelets to analyze short non-stationary signals makes wavelet transform a promising tool to evaluate physiological and pathological autonomic conditions.     

Risk factors for surgical-site infections in head and neck cancer surgery.

OBJECTIVE: The aim of this study was to identify risk factors for surgical-site infections (SSIs) in patients with head and neck cancer submitted to major clean-contaminated surgery. STUDY DESIGN: This is a prospective study conducted in a tertiary cancer center hospital. SUBJECTS AND METHODS: This study includes 258 patients submitted to a major clean-contaminated head and neck oncologic surgery. RESULTS: The overall SSI rate was 38.8%. The univariate analysis showed the following significant risk factors: race, tobacco consumption, clinical stage, comorbidities, time duration of the surgical procedure, and flap reconstruction. The final model by logistic regression identified the following independent predictors for SSI: tobacco consumption (odds ratio [OR] = 2.96), presence of metastatic lymph nodes (OR = 2.05), flap reconstruction (OR = 2.20), and antimicrobial prophylaxis exceeding 48 hours (OR=1.89). CONCLUSION: The high-risk patients for SSI in head and neck oncologic surgery were those with cancer at advanced stages, those who were smokers, those presenting comorbidities, those who needed major reconstruction of the surgical wound, or those who were submitted to inadequate antibiotic prophylaxis.     

Focal Adhesion Kinase Is Important for Fluid Shear Stress‐Induced Mechanotransduction in Osteoblasts

Mechanical loading of bone is important for maintenance of bone mass and structural stability of the skeleton. When bone is mechanically loaded, movement of fluid within the spaces surrounding bone cells generates fluid shear stress (FSS) that stimulates osteoblasts, resulting in enhanced anabolic activity. The mechanisms by which osteoblasts convert the external stimulation of FSS into biochemical changes, a process known as mechanotransduction, remain poorly understood. Focal adhesions are prime candidates for transducing external stimuli. Focal adhesion kinase (FAK), a nonreceptor tyrosine kinase found in focal adhesions, may play a key role in mechanotransduction, although its function has not been directly examined in osteoblasts. We examined the role of FAK in osteoblast mechanotransduction using short interfering RNA (siRNA), overexpression of a dominant negative FAK, and FAK^?/? osteoblasts to disrupt FAK function in calvarial osteoblasts. Osteoblasts were subjected to varying periods oscillatory fluid flow (OFF) from 5 min to 4 h, and several physiologically important readouts of mechanotransduction were analyzed including: extracellular signal‐related kinase 1/2 phosphorylation, upregulation of c‐fos, cyclooxygenase‐2, and osteopontin, and release of prostaglandin E₂. Osteoblasts with disrupted FAK signaling exhibited severely impaired mechanical responses in all endpoints examined. These data indicate the importance of FAK for both short and long periods of FSS‐induced mechanotransduction in osteoblasts.     

Passerine Exposure to Primarily PCDFs and PCDDs in the River Floodplains Near Midland, Michigan, USA

House wren (Troglodytes aedon), tree swallow (Tachycineta bicolor), and eastern bluebird (Sialia sialis) tissues collected in study areas (SAs) downstream of Midland, Michigan (USA) contained concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) greater than in upstream reference areas (RAs) in the region. The sum of concentrations of PCDD/DFs (ΣPCDD/DFs) in eggs of house wrens and eastern bluebirds from SAs were 4- to 22-fold greater compared to those from RAs, whereas concentrations in tree swallow eggs were similar among areas. Mean concentrations of ΣPCDD/DFs and sum 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (ΣTEQs_WHO-Avian), based on 1998 WHO avian toxic equivalency factors, in house wren and eastern bluebird eggs ranged from 860 (430) to 1500 (910) ng/kg wet weight (ww) and 470 (150) to 1100 (510) ng/kg ww, respectively, at the most contaminated study areas along the Tittabawassee River, whereas mean concentrations in tree swallow eggs ranged from 280 (100) to 760 (280) ng/kg ww among all locations. Concentrations of ΣPCDD/DFs in nestlings of all studied species at SAs were 3- to 50-fold greater compared to RAs. Mean house wren, tree swallow, and eastern bluebird nestling concentrations of ΣPCDD/DFs and ΣTEQs_WHO-Avian ranged from 350 (140) to 610 (300) ng/kg ww, 360 (240) to 1100 (860) ng/kg ww, and 330 (100) to 1200 (690) ng/kg ww, respectively, at SAs along the Tittabawassee River. Concentrations of ΣTEQs_WHO-Avian were positively correlated with ΣPCDD/DF concentrations in both eggs and nestlings of all species studied. Profiles of relative concentrations of individual congeners were dominated by furan congeners (69–84%), primarily 2,3,7,8-tetrachlorodibenzofuran and 2,3,4,7,8-pentachlorodibenzofuran, for all species at SAs on the Tittabawassee and Saginaw rivers but were dominated by dioxin congeners at upstream RAs.