In the context of covid-19, aerosol generating procedures have been highlighted as requiring a higher grade of personal protective equipment. We investigated how official guidance documents and academic publications have classified procedures in terms of whether or not they are aerosol-generating. We performed a rapid systematic review using preferred reporting items for systematic reviews and meta-analyses standards. Guidelines, policy documents and academic papers published in english or french offering guidance on aerosol-generating procedures were eligible. We systematically searched two medical databases (medline, cochrane central) and one public search engine (google) in march and april 2020. Data on how each procedure was classified by each source were extracted. We determined the level of agreement across different guidelines for each procedure group, in terms of its classification as aerosol generating, possibly aerosol-generating, or nonaerosol-generating. 128 documents met our inclusion criteria; they contained 1248 mentions of procedures that we categorised into 39 procedure groups. Procedures classified as aerosol-generating or possibly aerosol-generating by ≥90% of documents included autopsy, surgery/postmortem procedures with high-speed devices, intubation and extubation procedures, bronchoscopy, sputum induction, manual ventilation, airway suctioning, cardiopulmonary resuscitation, tracheostomy and tracheostomy procedures, non-invasive ventilation, high-flow oxygen therapy, breaking closed ventilation systems, nebulised or aerosol therapy, and high frequency oscillatory ventilation. Disagreements existed between sources on some procedure groups, including oral and dental procedures, upper gastrointestinal endoscopy, thoracic surgery and procedures, and nasopharyngeal and oropharyngeal swabbing. There is sufficient evidence of agreement across different international guidelines to classify certain procedure groups as aerosol generating. However, some clinically relevant procedures received surprisingly little mention in our source documents. To reduce dissent on the remainder, we recommend that (a) clinicians define procedures more clearly and specifically, breaking them down into their constituent components where possible; (b) researchers undertake further studies of aerosolisation during these procedures; and (c) guideline-making and policy-making bodies address a wider range of procedures.

The purpose of the study was to determine if exhaled nitric oxide levels in children varied according to their asthmatic and atopic status. Exhaled nitric oxide was measured in a sample of 93 children attending the North West Lung Centre, Manchester, United Kingdom, for the clinical evaluation of a respiratory questionnaire being developed as a screening tool in general practice. The clinical assessment included full lung function, skin prick testing, and exercise challenge. Children were said to be asthmatic either by consensus decision of three independent consultant pediatricians, who reviewed all the clinical results except the nitric oxide measurements, or by positive exercise test. Atopic asthmatic children had higher geometric mean exhaled nitric oxide levels (consensus decision, 12.5 ppb [parts per billion] 95% CI, 8.3 to 18.8; positive exercise test, 12.2 ppb 95% CI, 7.6 to 19.7) than did nonatopic asthmatic children (3.2 ppb 95% CI, 2.3 to 4.6; 3.2 ppb 95% CI, 2.0 to 5.0), atopic nonasthmatic children (3.8 ppb 95% CI, 2.7 to 5.5; 5.7 ppb 95% CI, 4.1 to 8.0), or nonatopic nonasthmatic children (3.4 ppb 95% CI, 2.8 to 4.1; 3.5 ppb 95% CI, 3.0 to 4.1). Thus, exhaled nitric oxide was raised in atopic asthmatics but not in nonatopic asthmatics, and these nonatopic asthmatics had levels of exhaled nitric oxide similar to those of the nonasthmatics whether atopic or not.

The level of exhaled nitric oxide (eNO) is elevated in patients with asthma and eNO may be involved in airway inflammation. Exposure to allergen in sensitized individuals may contribute to airway inflammation. Our aim was to investigate the relationship between eNO, sensitization, and exposure to indoor allergen in nonsmoking adults with asthma who are not taking inhaled steroids. In subjects with a positive methacholine challenge (PD20 < 4 mg) we measured eNO (LR 2000 chemiluminesence analyzer); serum total and specific IgE; skin test to mite, cat, and dog; and allergen levels in domestic dust (Der p 1, Fel d 1, and Can f 1). Subjects were classified as exposed or not exposed to allergen according to previously proposed significant levels ( > 2 μ g/g Der p 1, > 8 μ g/g Fel d 1, and > 10 μ g/g Can f 1). Of the 43 subjects ( > 95% atopic) complete data were available for 38, of whom 26 were both sensitized and exposed to one or more allergen and 12 were sensitized but not exposed to any allergens. eNO was significantly higher in those subjects who were both sensitized and exposed to indoor allergen than in those who were sensitized but not exposed (GM and 95% CI: 17.69 [14.1– 22.15] versus 9.09 [6.5–12.7], p = 0.001). Levels of eNO are significantly higher in patients with asthma who are both sensitized and exposed to relevant allergen than in those who were sensitized but not exposed. eNO may be a marker of the airway inflammation induced by domestic exposure to allergen in sensitized patients with asthma.