Correction: A novel scaling methodology to reduce the biases associated with missing data from commercial activity monitors.

[This corrects the article DOI: 10.1371/journal.pone.0235144.].

A novel scaling methodology to reduce the biases associated with missing data from commercial activity monitors.

BACKGROUND: Commercial physical activity monitors have wide utility in the assessment of physical activity in research and clinical settings, however, the removal of devices results in missing data and has the potential to bias study conclusions. This study aimed to evaluate methods to address missingness in data collected from commercial activity monitors. METHODS: This study utilised 1526 days of near complete data from 109 adults participating in a European weight loss maintenance study (NoHoW). We conducted simulation experiments to test a novel scaling methodology (NoHoW method) and alternative imputation strategies (overall/individual mean imputation, overall/individual multiple imputation, Kalman imputation and random forest imputation). Methods were compared for hourly, daily and 14-day physical activity estimates for steps, total daily energy expenditure (TDEE) and time in physical activity categories. In a second simulation study, individual multiple imputation, Kalman imputation and the NoHoW method were tested at different positions and quantities of missingness. Equivalence testing and root mean squared error (RMSE) were used to evaluate the ability of each of the strategies relative to the true data. RESULTS: The NoHoW method, Kalman imputation and multiple imputation methods remained statistically equivalent (p<0.05) for all physical activity metrics at the 14-day level. In the second simulation study, RMSE tended to increase with increased missingness. Multiple imputation showed the smallest RMSE for Steps and TDEE at lower levels of missingness (<19%) and the Kalman and NoHoW methods were generally superior for imputing time in physical activity categories. CONCLUSION: Individual centred imputation approaches (NoHoW method, Kalman imputation and individual Multiple imputation) offer an effective means to reduce the biases associated with missing data from activity monitors and maximise data retention.

The characteristics of krill swarms in relation to aggregating Antarctic blue whales.

We model the presence of rare Antarctic blue whales (Balaenoptera musculus intermedia) in relation to the swarm characteristics of their main prey species, Antarctic krill (Euphausia superba). A combination of visual observations and recent advances in passive acoustic technology were used to locate Antarctic blue whales, whilst simultaneously using active underwater acoustics to characterise the distribution, size, depth, composition and density of krill swarms. Krill swarm characteristics and blue whale presence were examined at a range of spatiotemporal scales to investigate sub meso-scale (i.e., <100 km) foraging behaviour. Results suggest that at all scales, Antarctic blue whales are more likely to be detected within the vicinity of krill swarms with a higher density of krill, those found shallower in the water column, and those of greater vertical height. These findings support hypotheses that as lunge-feeders of extreme size, Antarctic blue whales target shallow, dense krill swarms to maximise their energy intake. As both Antarctic krill and blue whales play a key role in the Southern Ocean ecosystem, the nature of their predator-prey dynamics is an important consideration, not only for the recovery of this endangered species in a changing environment, but for the future management of Antarctic krill fisheries.

Diet and trophic niche of Antarctic silverfish Pleuragramma antarcticum in the Ross Sea, Antarctica.

The diet of Antarctic silverfish Pleuragramma antarcticum was evaluated by examining stomach contents of specimens collected in the Ross Sea (71°-77° S; 165°-180° E) in January to March 2008. Pleuragramma antarcticum (50-236 mm standard length, L(S)) and prey items were analysed for stable-isotopic composition of carbon and nitrogen. According to index of relative importance (I(RI) ), which incorporates frequency of occurrence, mass and number of prey items, the most important prey items were copepods (81%I(RI) over all specimens), predominantly Metridia gerlachei and Paraeuchaeta sp., with krill and fishes having low I(RI) (2·2 and 5·6%I(RI) overall). According to mass of prey (M) in stomachs, however, fishes (P. antarcticum and myctophids) and krill dominated overall diet (48 and 22%M, respectively), with copepods being a relatively minor constituent of overall diet by mass (9·9%M). Piscivory by P. antarcticum occurred mainly in the extreme south-west of the region and near the continental slope. Krill identified to species level in P. antarcticum stomachs were predominantly Euphausia superba (14·1%M) with some Euphausia crystallophorias (4·8%M). Both DistLM modelling (PRIMER-permanova+) on stomach contents (by I(RI)) and stepwise generalized linear modelling on stable isotopes showed that L(S) and location were significant predictors of P. antarcticum diet. Postlarval P. antarcticum (50-89 mm L(S)) consumed exclusively copepods. Juvenile P. antarcticum (90-151 mm L(S)) consumed predominantly krill and copepods by mass (46 and 30%M, respectively). Small adult P. antarcticum (152-178 mm L(S)) consumed krill, fishes and copepods (37, 36 and 15%M, respectively). Large adult P. antarcticum (179-236 mm L(S)) consumed predominantly fishes and krill (55 and 17%M, respectively), especially in the north (near the Ross Sea slope) and in the SW Ross Sea. Amphipods were occasionally important prey items for P. antarcticum (western Ross Sea, 39%M). General concordance between stomach contents and trophic level of P. antarcticum and prey based on δ(15) N was demonstrated. Pleuragramma antarcticum trophic level was estimated as 3·7 (postlarval fish) and 4·1 (fish aged 3+ years).

A rare complication of pneumonectomy: diagnosis made by a literature search.

This case describes platypnoea-orthodeoxia syndrome in a patient 2 months after a right pneumonectomy for adenocarcinoma of the lung. The patient complained of platypnoea (breathlessness in the upright position) and was noted to have orthodeoxia (arterial desaturation on standing) on clinical examination. This was due to anatomical changes after the pneumonectomy that resulted in direct blood flow from the inferior vena cava through a previously unrecognised atrial septal defect into the left atrium. The closure of this right to left shunt with an Amplatzer occluder produced immediate and striking symptomatic relief in the patient. The authors had no previous experience of this very rare complication of pneumonectomy. The diagnosis was made after a literature search using PubMed/Medline, underlining the direct clinical benefit provided by these databases.

Do all patients require supplemental oxygen during flexible bronchoscopy?

STUDY OBJECTIVES: Some respiratory units routinely administer supplemental oxygen to all patients during flexible bronchoscopy, but other units give oxygen only to those who desaturate (arterial oxygen saturation [SaO(2)], < 90%). We performed a study to examine both the requirement for supplemental oxygen and the effect of IV midazolam therapy on oxygenation during flexible bronchoscopy for patients with a known FEV(1). DESIGN: Data on the SaO(2) of patients during flexible bronchoscopy were collected prospectively for all procedures performed in our respiratory unit for the period 1992 to 1997. RESULTS: There were 1,051 flexible bronchoscopy procedures performed in which the patient had a known FEV(1) and was not receiving supplemental oxygen before the procedure. Supplemental oxygen was commenced during or immediately after the procedure in 151 cases (14.4%), while a further 101 cases (9.6%) had momentary desaturation (ie, < 20 s) not requiring oxygen therapy. The lower the FEV(1), the greater the risk of significant desaturation and the need for supplemental oxygen (p < 0.0001) [supplemental O(2) therapy was administered in 35% of cases if FEV(1) < 1.0 L, in 14% of cases if FEV(1) was 1.0 to 1.5 L, and in 7% of cases if FEV(1) > 1.5 L]. The use of low-to-moderate doses of midazolam as sedation did not affect the probability of the occurrence of significant desaturation (p = 0.204). CONCLUSIONS: This study supports guidelines that suggest that all patients should be monitored by pulse oximetry during flexible bronchoscopy. Desaturation may occur at any FEV(1) level even without sedation. The majority of our patients did not require routine oxygen supplementation, especially the group with an FEV(1) above 1 L.

Thyroid autoimmune disease in a large Newfoundland family: the influence of HLA.

Ninety-eight members of a large Newfoundland family, seven of whose members over three generations suffered from Graves' disease, were studied with respect to the mode of transmission of the disease and its association with HLA. Compared to Newfoundland communities of similar size and geographical location, very little consanguinity was documented in this family. The susceptibility to Graves' disease appeared to be inherited as a dominant with a variable degree of expressivity; the degree of expressivity being determined by the female sex. In part of the pedigree, the susceptibility to Graves' disease entered the family with a wife. Three of her offspring who subsequently developed Graves' disease shared with her the haplotype A9, Bw16. Of the three remaining affected family members, two shared the haplotype A1, B8, whereas the third carried the haplotypes Aw32,b8; a9,bw16. Graves' disease could be associated with either of these two haplotypes in the last individual. This study shows that the susceptibility to Graves' disease is inherited associated with HLA and that whereas the disease susceptibility gene for Graves' disease is in linkage disequilibrium with HLA-B8 in Caucasians, it can be randomly associated with other HLA-B antigens.