Fractional Exhaled Nitric Oxide in the Interpretation of Specific Inhalational Challenge Tests for Occupational Asthma

Purpose

Fractional exhaled nitric oxide (FE_NO) measurements are recommended for the assessment of eosinophilic airway inflammation in asthma. Clinically relevant increases in FE_NO have been reported 24 h after positive specific inhalational challenge (SIC) tests in occupational asthma. We aimed to determine whether positive SICs could be discriminated from control tests, on the basis of change in FE_NO.

Methods

We reviewed all positive SICs to a variety of agents performed at our institution 2008–2012 and gathered data on age, sex, asthmatic response (immediate/dual/late), smoking status, inhaled corticosteroid usage, and FE_NO pre- and 24-h postcontrol and positive SIC from each worker. Changes in FE_NO after positive SICs were compared with control SICs from each worker, by using paired Student’s t tests.

Results

In 16 workers, negative control challenges were associated with mean changes in FE_NO of 9 % (95 % CI ?1.14 to 19.01) or 1.1 ppb (95 % CI ?3.59 to 5.84); 2 of 16 (13 %) workers tested showed increases in FE_NO that were clinically relevant based on recent guidelines. Subsequent positive SICs were associated with mean changes in FE_NO of 7 % (95 % CI ?15.73 to 29.6) or 2.1 ppb (95 % CI ?6.07 to 10.19), which were not significantly different to controls; only 2 of 16 (13 %) workers had FE_NO changes that were clinically relevant.

Conclusions

FE_NO changes above the upper confidence limits of ≥20 % or ≥6 ppb may be considered to be outside the range of normality. However, the majority of workers who had clearly positive SICs to common low molecular weight agents also had no statistically or clinically relevant increase in FE_NO. Therefore, change in FE_NO does not predict a positive SIC in this group.     

The prevalence of fibromyalgia in axial spondyloarthritis

Rheumatology International - Comorbid fibromyalgia, in axial spondyloarthritis (axSpA) has been shown to influence disease activity and function, and quality of life. Although several papers exist,...     

Modulation of alpha and gamma oscillations related to retrospectively orienting attention within working memory

Selective attention mechanisms allow us to focus on information that is relevant to the current behavior and, equally important, ignore irrelevant information. An influential model proposes that oscillatory neural activity in the alpha band serves as an active functional inhibitory mechanism. Recent studies have shown that, in the same way that attention can be selectively oriented to bias sensory processing in favor of relevant stimuli in perceptual tasks, it is also possible to retrospectively orient attention to internal representations held in working memory. However, these studies have not explored the associated oscillatory phenomena. In the current study, we analysed the patterns of neural oscillatory activity recorded with magnetoencephalography while participants performed a change detection task, in which a spatial retro‐cue was presented during the maintenance period, indicating which item or items were relevant for subsequent retrieval. Participants benefited from retro‐cues in terms of accuracy and reaction time. Retro‐cues also modulated oscillatory activity in the alpha and gamma frequency bands. We observed greater alpha activity in a ventral visual region ipsilateral to the attended hemifield, thus supporting its suppressive role, i.e. a functional disengagement of task‐irrelevant regions. Accompanying this modulation, we found an increase in gamma activity contralateral to the attended hemifield, which could reflect attentional orienting and selective processing. These findings suggest that the oscillatory mechanisms underlying attentional orienting to representations held in working memory are similar to those engaged when attention is oriented in the perceptual space.     

Medial prefrontal theta phase coupling during spatial memory retrieval

Memory retrieval is believed to involve a disparate network of areas, including medial prefrontal and medial temporal cortices, but the mechanisms underlying their coordination remain elusive. One suggestion is that oscillatory coherence mediates inter‐regional communication, implicating theta phase and theta‐gamma phase‐amplitude coupling in mnemonic function across species. To examine this hypothesis, we used non‐invasive whole‐head magnetoencephalography (MEG) as participants retrieved the location of objects encountered within a virtual environment. We demonstrate that, when participants are cued with the image of an object whose location they must subsequently navigate to, there is a significant increase in 4–8 Hz theta power in medial prefrontal cortex (mPFC), and the phase of this oscillation is coupled both with ongoing theta phase in the medial temporal lobe (MTL) and perceptually induced 65–85 Hz gamma amplitude in medial parietal cortex. These results suggest that theta phase coupling between mPFC and MTL and theta‐gamma phase‐amplitude coupling between mPFC and neocortical regions may play a role in human spatial memory retrieval. © 2014 The Authors. Hippocampus Published by Wiley Periodicals, Inc.     

Optimisation of Cu+ impregnation of MOF-74 to improve CO/N2 and CO/CO2 separations

Carbon monoxide (CO) purification from syngas impurities is a highly energy and cost intensive process. Adsorption separation using metal–organic frameworks (MOFs) is being explored as an alternative technology for CO/nitrogen (N₂) and CO/carbon dioxide (CO₂) separation. Currently, MOFs'' uptake and selectivity levels do not justify displacement of the current commercially available technologies. Herein, we have impregnated a leading MOF candidate for CO purification, i.e. M-MOF-74 (M = Co or Ni), with Cu⁺ sites. Cu⁺ allows strong π-complexation from the 3d electrons with CO, potentially enhancing the separation performance. We have optimised the Cu loading procedure and confirmed the presence of the Cu⁺ sites using X-ray absorption fine structure analysis (XAFS). In situ XAFS and diffuse reflectance infrared Fourier Transform spectroscopy analyses have demonstrated Cu⁺–CO binding. The dynamic breakthrough measurements showed an improvement in CO/N₂ and CO/CO₂ separations upon Cu impregnation. This is because Cu sites do not block the MOF metal sites but rather increase the number of sites available for interactions with CO, and decrease the surface area/porosity available for adsorption of the lighter component.

We present an in situ study of CO adsorption on Cu impregnated MOF-74 and study the competitive adsorption of CO vs. CO₂ and N₂.     

AAEM case report #30: Multifocal motor neuropathy

A 73-year-old man with a 16-year history of fasciculations and 15 years of weakness in his right arm was diagnosed with focal motor neuron disease. After 10 years of purely motor symptoms, he developed mild parasthesias although his sensory examination remained normal. Reflexes were reduced or absent in the weak muscles but were normal elsewhere. Nerve conduction was studied in nerves innervating weak muscles and showed severe motor conduction block. Sensory nerve conduction studies were minimally abnormal, showing reduced amplitudes with normal velocities. Based on the clinical picture and the presence of severe motor conduction block, the patient was diagnosed with multifocal motor neuropathy. Treatment with high-dose intravenous immunoglobulin was given with significant improvement in strength and partial resolution of the conduction block. As this case demonstrates, this treatable disorder may occasionally be mistaken for motor neuron disease although the resemblance is only superficial, and it should never be mistaken for amyotrophic lateral sclerosis. Multifocal motor neuropathy is an inflammatory, demyelinating neuropathy which, like chronic inflammatory demyelinating polyneuropathy (CIDP), is probably immune-mediated. It differs from typical CIDP by virtue of a marked predilection for motor axons, a strikingly restricted distribution, and a protracted course. Treatment with high-dose intravenous immunoglobulin is frequently helpful, but other forms of immune manipulation are less effective. © 1996 Gareth J. Parry, MD, FRACP. Published by John Wiley & Sons, Inc.     

Apparent diffusion coefficients in benign and secondary progressive multiple sclerosis by nuclear magnetic resonance

The diffusion characteristics of water in brain white matter were studied in patients with benign and secondary progressive multiple sclerosis (MS), and also in normal controls. In the MS patients, both lesions and normal-appearing white matter (NAWM) were examined to assess whether pathological differences might be evident from the diffusion behavior. A volume-selective technique was used to reduce data acquisition time and improve the reliability and precision of the measurements. This also allowed the time-dependence of apparent diffusion coefficients to be assessed. While lesions from both patient groups showed an elevated diffusion coefficient, no differences between the two groups were found. In addition, NAWM was elevated for both patient groups compared with the control group, although this was only statistically significant for patients with a benign disease course. The degree of elevation of the diffusion coefficient within the individual lesions measured was not related to the disability of the patient. Pathological differences between lesions in patients with different disease courses, if they exist, have not been detected in this study of brain water diffusion.