Identifying dominant environmental predictors of freshwater wetland methane fluxes across diurnal to seasonal time scales

While wetlands are the largest natural source of methane (CH4) to the atmosphere, they represent a large source of uncertainty in the global CH4 budget due to the complex biogeochemical controls on CH4 dynamics. Here we present, to our knowledge, the first multi-site synthesis of how predictors of CH4 fluxes (FCH4) in freshwater wetlands vary across wetland types at diel, multiday (synoptic), and seasonal time scales. We used several statistical approaches (correlation analysis, generalized additive modeling, mutual information, and random forests) in a wavelet-based multi-resolution framework to assess the importance of environmental predictors, nonlinearities and lags on FCH4 across 23 eddy covariance sites. Seasonally, soil and air temperature were dominant predictors of FCH4 at sites with smaller seasonal variation in water table depth (WTD). In contrast, WTD was the dominant predictor for wetlands with smaller variations in temperature (e.g., seasonal tropical/subtropical wetlands). Changes in seasonal FCH4 lagged fluctuations in WTD by similar to 17 +/- 11 days, and lagged air and soil temperature by median values of 8 +/- 16 and 5 +/- 15 days, respectively. Temperature and WTD were also dominant predictors at the multiday scale. Atmospheric pressure (PA) was another important multiday scale predictor for peat-dominated sites, with drops in PA coinciding with synchronous releases of CH4. At the diel scale, synchronous relationships with latent heat flux and vapor pressure deficit suggest that physical processes controlling evaporation and boundary layer mixing exert similar controls on CH4 volatilization, and suggest the influence of pressurized ventilation in aerenchymatous vegetation. In addition, 1- to 4-h lagged relationships with ecosystem photosynthesis indicate recent carbon substrates, such as root exudates, may also control FCH4. By addressing issues of scale, asynchrony, and nonlinearity, this work improves understanding of the predictors and timing of wetland FCH4 that can inform future studies and models, and help constrain wetland CH4 emissions.Peer reviewe

Gap-filling eddy covariance methane fluxes : Comparison of machine learning model predictions and uncertainties at FLUXNET-CH4 wetlands

Time series of wetland methane fluxes measured by eddy covariance require gap-filling to estimate daily, seasonal, and annual emissions. Gap-filling methane fluxes is challenging because of high variability and complex responses to multiple drivers. To date, there is no widely established gap-filling standard for wetland methane fluxes, with regards both to the best model algorithms and predictors. This study synthesizes results of different gap-filling methods systematically applied at 17 wetland sites spanning boreal to tropical regions and including all major wetland classes and two rice paddies. Procedures are proposed for: 1) creating realistic artificial gap scenarios, 2) training and evaluating gap-filling models without overstating performance, and 3) predicting halfhourly methane fluxes and annual emissions with realistic uncertainty estimates. Performance is compared between a conventional method (marginal distribution sampling) and four machine learning algorithms. The conventional method achieved similar median performance as the machine learning models but was worse than the best machine learning models and relatively insensitive to predictor choices. Of the machine learning models, decision tree algorithms performed the best in cross-validation experiments, even with a baseline predictor set, and artificial neural networks showed comparable performance when using all predictors. Soil temperature was frequently the most important predictor whilst water table depth was important at sites with substantial water table fluctuations, highlighting the value of data on wetland soil conditions. Raw gap-filling uncertainties from the machine learning models were underestimated and we propose a method to calibrate uncertainties to observations. The python code for model development, evaluation, and uncertainty estimation is publicly available. This study outlines a modular and robust machine learning workflow and makes recommendations for, and evaluates an improved baseline of, methane gap-filling models that can be implemented in multi-site syntheses or standardized products from regional and global flux networks (e.g., FLUXNET).Peer reviewe

Recovery room pth levels can facilitate safe calcium management after thyroidectomy for graves\u27 disease

The use of early postoperative parathyroid hormone (PTH) levels to help guide calcium management after thyroid surgery has been demonstrated to be an effective approach. However, no studies have investigated this method specifically for patients undergoing surgery for hyperthyroidism, who because of a greater rate of hypoparathyroidism and the potential compounding influence of hungry bone syndrome are at particular risk for significant hypocalcemia. This study examines the safety of utilizing recovery room (RR) PTH levels to stratify these patients and to dictate the post-operative calcium regimen. Patients who underwent total thyroidectomy for hyperthyroidism by a single endocrine surgeon were retrospectively examined. Patient demographics, use of intraoperative PTH postoperatively, post-operative calcium regimen, and post-operative complications, including hypoparathyroidism and emergency department (ED) visits were analyzed. During the study period 48 patients underwent total thyroidectomy for hyperthyroidism. Of these, 32 patients had a RR PTH obtained post-operatively. Due to sufficient PTH levels, 19 patients were discharged with no calcium supplementation and 13 (including 7 with undetectable PTH levels) were provided a supplementation regimen that included calcium ± calcitriol due to their low PTH. None of the 25 patients with detectable or normal PTH levels returned to the ED. Of those with undetectable PTH levels, 2/7 came to the ED with acute hypocalcemic symptoms (p \u3c 0.05). In comparison, 1/16 patients who did not have a RR PTH and who universally were managed with calcium (only) supplementation had a post-operative ED visit. Only 1 patient (2.1%) of the overall cohort experienced permanent hypoparathyroidism. Using RR PTH to determine post-operative calcium management after a total thyroidectomy for hyperthyroidism is safe and results in few returns to the ED. However, patients with undetectable PTH levels are at markedly greater risk of developing symptoms requiring an ED visit. Surgeons should consider these risks when determining ambulatory status following surgery

A faster parathyroidectomy: Techniques to shorten non-surgical operating room time

OBJECTIVE: To assess the capacity of different techniques to reduce non-operative times during parathyroid surgery. The impact of monitored anesthesia care (MAC) instead of general anesthesia, and the pre-operative placement of a second peripheral intravenous catheter (PIV) were analyzed. METHODS: A retrospective case series at an academic medical center was performed to study patients undergoing parathyroidectomy by a single surgeon between November 2013 and October 2016. Three operating room (OR) time measurements were compared: pre-incision time, post-closure time, and total OR time. RESULTS: Surgeries performed under MAC (n = 21) had statistically shorter pre-incision (33.2 min vs. 39.7 min, p \u3c .001), post-closure (10.1 min vs. 16.2 min, p = .002), and total operative times (113.0 min vs. 151.5 min, p \u3c .001) compared to those in which general anesthesia (n = 169) was used. Of the 169 patients who underwent general anesthesia, 25 had a second PIV placed preoperatively and 144 had only a single PIV. All 3 time periods were statistically shorter in patients who had a second PIV versus those who had only a single PIV (pre-incision 32.2 min vs. 41.0 min, p \u3c .001; post-closure 12.2 min vs. 16.9 min, p \u3c .001; total 117.9 min vs. 157.4 min, p \u3c .001). CONCLUSIONS: In patients undergoing parathyroid surgery in which ioPTH levels will be used, the placement of a second PIV in the pre-operative holding area and performance of surgery under MAC can significantly shorten non-operative and total OR time

Surgical impact of a dedicated endocrine surgeon on an academic otolaryngology department

OBJECTIVES: Endocrine surgery is emerging as a dedicated subspecialty in otolaryngology. We assess the impact of an endocrine surgeon on an academic otolaryngology department\u27s thyroid and parathyroid surgery volume. METHODS: A retrospective study of overall endocrine caseloads and resident case logs at a single academic center in the Midwest was performed. All thyroid and parathyroid cases performed by the otolaryngology department at an academic center from 2011 to 2017 were reviewed. In September 2012, an otolaryngologist who had completed an American Head and Neck Society endocrine surgery fellowship joined the faculty. The volume of endocrine surgery performed by the residents was also analyzed. Comparison of means and linear regression models were performed. RESULTS: From 2011 to 2012, the department performed a mean of 77 thyroid and 11.5 parathyroid surgeries annually. After the endocrine surgeon joined the department, this increased to an average of 212.8 thyroidectomies (P \u3c 0.01) and 72.4 parathyroidectomies (P \u3c 0.01) a year. The head and neck surgeons and generalists still performed an average of 42.4 thyroidectomies and 2.6 parathyroidectomies a year. For graduating residents, the average number of thyroid/parathyroid cases increased from 42.5 in 2012 to 151 in 2016. CONCLUSION: The addition of a fellowship-trained endocrine surgeon substantially increased the thyroid and parathyroid surgical volume of the otolaryngology department. Importantly, generalists and head and neck surgeons in the department continued to perform a significant number of these cases. Departments seeking similar surgical growth and expanded resident experience may consider the value of engaging a dedicated endocrine surgeon. LEVEL OF EVIDENCE: 4 Laryngoscope, 2019

Socioeconomic disparities and comorbidities, not race, affect salivary gland malignancy survival outcomes

OBJECTIVES/HYPOTHESIS: This study sought to determine whether comorbidities, race, and socioeconomic factors affect 5- and 10-year survival outcomes for patients with salivary gland malignancies treated at a single large academic institution with a large African American population. STUDY DESIGN: A retrospective cohort study was performed of all patients with salivary gland malignancies, from 1990 to 2015, at a large academic medical center. METHODS: Standard statistical analysis was performed using Kaplan-Meier survival curve analysis and Cox proportional hazard models. RESULTS: The overall 5- and 10-year survival rates decreased with age ≥ 60 years (P \u3c .001), stage 3 or 4 (P \u3c .001), clinical T stage 3 or 4 (P \u3c .001), and clinical N stage 1, 2, or 3 (P \u3c .001). Living in a ZIP code with an increasing proportion of residents with a high school degree or less (P \u3c .05), being male (P \u3c .05), increasing age at the time of diagnosis (P \u3c .001), and increasing Charlson comorbidity index (P \u3c .05) detrimentally impacted survival at 5 and 10 years. Race was associated with socioeconomic variables, but race was not a prognostic indicator of survival. CONCLUSIONS: Socioeconomic factors and comorbidities, not race, were negative prognostic indicators of survival of patients with salivary gland malignancies. Using race as a marker for socioeconomic status should be used with caution. LEVEL OF EVIDENCE: 4. Laryngoscope, 127:2545-2550, 2017

Bony cochlear nerve canal stenosis and speech discrimination in pediatric unilateral hearing loss

OBJECTIVES/HYPOTHESIS: To examine the relationship between bony cochlear nerve canal (BCNC) width, degree of hearing loss, and speech discrimination in children with unilateral sensorineural hearing loss (USNHL). STUDY DESIGN: Retrospective chart review (case-control study). METHODS: Audiometric database was cross-referenced with radiologic database at pediatric tertiary care facility to identify children with USNHL and temporal bone computed tomography. BCNC widths were measured independently by two radiologists blinded to affected ear. Regression analyses investigated associations among variables. RESULTS: One hundred and sixty children with USNHL had temporal bone imaging. Mean BCNC width was significantly smaller in affected ears, P = 0.0001. Narrower width was associated with more severe hearing loss, P = 0.01. Among children who had narrower cochlear nerve canals in affected ears compared to unaffected ears, smaller width was associated with lower speech discrimination score, P = 0.03. Increasing asymmetry in BCNC width between affected and unaffected ears was associated with poorer discrimination scores, P = 0.02. Among ears with asymmetrically smaller cochlear nerve canals, a 1-mm reduction in cochlear canal width between the normal and affected ear was associated with 30.4% lower word recognition score percentage in the affected ear, P = \u3c 0.001. CONCLUSION: There is a significant association between BCNC stenosis and impaired speech discrimination, independent of degree of hearing loss. Further investigation is needed to determine whether BCNC stenosis is a poor prognostic factor for auditory rehabilitation