Showing papers by "Christopher J. Russell published in 2017"

Comparison of pulsar positions from timing and very long baseline astrometry

Abstract: Pulsar positions can be measured with high precision using both pulsar timing methods and very long baseline interferometry (VLBI). Pulsar timing positions are referenced to a solar-system ephemeris, whereas VLBI positions are referenced to distant quasars. Here, we compare pulsar positions from published VLBI measurements with those obtained from pulsar timing data from the Nanshan and Parkes radio telescopes in order to relate the two reference frames. We find that the timing positions differ significantly from the VLBI positions (and also differ between different ephemerides). A statistically significant change in the obliquity of the ecliptic of 2.16 ± 0.33 mas is found for the JPL ephemeris DE405, but no significant rotation is found in subsequent JPL ephemerides. The accuracy with which we can relate the two frames is limited by the current uncertainties in the VLBI reference source positions and in matching the pulsars to their reference source. Not only do the timing positions depend on the ephemeris used in computing them, but also different segments of the timing data lead to varying position estimates. These variations are mostly common to all ephemerides, but slight changes are seen at the 10 μas level between ephemerides.

Pseudomonas aeruginosa and post-tracheotomy bacterial respiratory tract infection readmissions

Abstract: Objective Identify risk factors for readmission due to a bacterial tracheostomy-associated respiratory tract infection (bTARTI) within 12 months of discharge after tracheotomy. Design/Methods We performed a retrospective cohort study of 240 children who underwent tracheotomy and were discharged with tracheotsomy in place between January 1, 2005 and June 30, 2013. Children with prolonged total or post-tracheotomy length of stay (LOS), less than 12 months of follow-up, or who died during the index hospitalization were excluded. Readmission for a bTARTI (eg, pneumonia, tracheitis) treated with antibiotics, as ascertained by manual chart review, was the outcome variable. We used multivariate logistic regression to identify the independent association between risk factors and hospital readmission for bTARTI within 12 months. Results At index hospitalizations for tracheotomy, the median admission age was 5 months (interquartile range [IQR] 2-43 months) and median LOS was 73 days (IQR 43-121 days). Most patients were of Hispanic ethnicity (n = 162, 68%) and were publicly insured (n = 213, 89%). Nearly half (n = 112, 47%) were discharged on positive pressure mechanical ventilation. Many (n = 103, 43%) were admitted for bTARTI within 12 months of discharge. Only Hispanic ethnicity (adjusted odds ratio [AOR] 2.0; 95% confidence interval [CI]: 1.1-3.9; P = 0.03) and acquisition of Pseudomonas aeruginosa between tracheotomy and discharge from index hospitalization (AOR 3.2; 95%CI: 1.2-8.3; P = 0.02) were independently associated with increased odds of bTARTI readmission, while discharge on gastrointestinal pro-motility agents was associated with decreased risk (AOR = 0.4; 95%CI: 0.2-0.8; P = 0.01). Conclusions Hispanic ethnicity and post-tracheotomy acquisition of P. aeruginosa during initial hospitalization are associated with bTARTI readmission.

Care Variations and Outcomes for Children Hospitalized With Bacterial Tracheostomy-Associated Respiratory Infections

Abstract: OBJECTIVES: Identify hospital-level care variations and association with length of stay (LOS) and hospital revisit in children with tracheostomies hospitalized for bacterial respiratory tract infections (bRTIs). METHODS: A multicenter, retrospective cohort study that used the Pediatric Health Information System database between 2007 and 2014 of patients with tracheostomies aged ≤18 years with a primary diagnosis of bRTI (eg, tracheitis) or a primary diagnosis of a bRTI symptom (eg, cough) and a secondary diagnosis of bRTI. Primary outcomes were LOS and 30-day all-cause revisit rates. Secondary outcomes included hospital-level diagnostic testing and anti- Pseudomonas antibiotic use. We used mixed-effects negative binomial (for LOS) and logistic (for revisit) regression to explore the relationship between hospital-level diagnostic test utilization and the outcomes. RESULTS: Data representing 4137 unique patients with a median age of 3 years (interquartile range: 1–9 years) were included. Median LOS was 4 days (interquartile range: 3–8 days), and the 30-day revisit rate was 24.9%. Use of diagnostic testing and empirical anti- Pseudomonas antibiotics varied significantly among hospitals (all P values CONCLUSIONS: Given that care variations were not associated with outcomes, future research should focus on standardizing diagnosis and treatment of bRTIs and readmission prevention in this population.

Risk factors for overnight respiratory events following sedation for magnetic resonance imaging in children with sleep apnea

Abstract: Children with sleep apnea may be at increased risk for overnight respiratory events (ORE) following anesthesia. We sought to identify ORE risk factors in sleep apnea patients sedated for magnetic resonance imaging (MRI). One thousand four hundred seven hospitalizations for children with sleep apnea (by ICD-9 code) occurred at our institution from 5/1/2011 to 2/1/2015. One hundred twenty-seven (9 %) encounters were solely for post-MRI observation representing 96 unique patients. The first post-MRI admission for each patient underwent chart review. ORE was defined as sustained oxygen saturation <90 % with need for increased oxygen or adjustment of respiratory support after release from recovery. Characteristics of patients with and without ORE were compared by chi-squared analysis or independent samples t test. Logistic regression identified associations with ORE. Ten out of 96 (10.4 %) patients had ORE. The average time following sedation to ORE was 10.25 h. ORE patients were hospitalized longer (median 2 vs. 1 day, p < 0.001). Overall, patients were 55 % male, 60 % Hispanic, with median age of 5 years [IQR 2–10] and median body mass index (BMI) of 17.9 [IQR 15.2–24]. On logistic regression, apnea-hypopnea index (AHI; OR 1.007 [95 % CI 1.002–1.011]), anesthesia complication (OR 1.13 [95 % CI 1.01–1.28]), and home non-invasive positive pressure ventilation (NIV; OR 6.08 [95 % CI 1.57–26.17]) were associated with ORE. Ninety percent of children with sleep apnea admitted for overnight observation following sedated MRI did not have an ORE. AHI, anesthesia complications, and NIV use may help target higher-risk patients and avoid unnecessary hospitalizations.