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A large variety of disposable face masks have been produced since the onset of the COVID-19 pandemic. Decreased resistance to inspiration improves adherence to the use of the mask; the so called breathability is usually estimated by the measurement of air flow across a section of the tissue under a given pressure difference. We hypothesized that the mask pressure-flow relationship studied in conditions that mimic tidal breathing could allow a more comprehensive characterization of airflow resistance, a major determinant of mask comfort. A physical analog was made of a plaster cast dummy head connected through a pneumotachograph to a series of bellows inflated/deflated by a respirator. Pressure was measured at the mock airway opening over which the mask was carefully secured. The precision of the measurement equipment was quantified using two estimates of measurement error: repeatability coefficient (RC) and within-mask coefficient of variation (CV wm ). The airflow resistance of 10 surgical masks was tested on 4 different days. Resistance means did not differ significantly among four repeated measures (0.34 hPa.s.L -1 ; 0.37 hPa.s.L -1 ; 0.37 hPa.s.L -1 ; and 0.37 hPa.s.L -1 ; p  = 0.08), the estimated RC was 0.08 hPa.s.L -1 [95%CI: 0.06-0.10 hPa.s.L -1 ], and CV wm was 8.7% [95%CI: 1.5-12.2%]. Multiple comparisons suggest the presence of a learning effect by which the operator reduced the error over the course of repetitive resistance measurements. Measurement precision improved considerably when the first set of measures was not taken into account [RC ~ 0.05 hPa.s.L -1 (95%CI: 0.03-0.06 hPa.s.L -1 ); CV wm ~4.5% (95%CI: 1.9-6.1%)]. The testing of the face mask resistance (R) appears simple and highly repeatable in conditions that resemble tidal breathing, once operator training was assured. The procedure adds further to the current standard assessment of breathability and allows estimating the maximal added respiratory load, about 10-20% of the respiratory resistance reported in heathy adult subjects., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Demoulin, Duvivier, Marchal and Demoulin-Alexikova.)

Introduction: Cough is a major lower airway defense mechanism that can be triggered by exercise in asthma patients. Studies on cough reflex in experimental animal models revealed a decrease of cough reflex sensitivity during exercise in healthy animals, but a lack of desensitization in ovalbumin-sensitized rabbits. The aim of our study is to evaluate the impact of inhaled corticosteroids on cough reflex during artificial limb exercise in an animal model of eosinophilic airway inflammation., Materials and Methods: Sixteen adult ovalbumin-sensitized rabbits were randomly divided into two groups. The "OVA-Corticoid" group ( n = 8) received inhaled corticosteroids (budesonide; 1 mg/day during 2 consecutive days) while the "OVA-Control" ( n = 8) group was exposed to saline nebulization. The sensitivity of defensive reflexes induced by direct mechanical stimulation of the trachea was studied in anesthetized animals, at rest and during artificial limb exercise. Cell count was performed on bronchoalveolar lavage fluid and middle lobe tissue sections to assess the level of eosinophilic inflammation., Results: All rabbits were significantly sensitized but there was no difference in eosinophilic inflammation on bronchoalveolar lavage or tissue sections between the two groups. Artificial limb exercise resulted in a significant ( p = 0.002) increase in minute ventilation by 30% (+ 209 mL.min -1 , ± 102 mL/min -1 ), with no difference between the two groups. 322 mechanical tracheal stimulations were performed, 131 during exercise (40.7%) and 191 at rest (59.3%). Cough reflex was the main response encountered (46.9%), with a significant increase in cough reflex threshold during artificial limb exercise in the "OVA-Corticoid" group ( p = 0.039). Cough reflex threshold remained unchanged in the "OVA-Control" group ( p = 0.109)., Conclusion: Inhaled corticosteroids are able to restore desensitization of the cough reflex during artificial limb exercise in an animal model of airway eosinophilic inflammation. Airway inflammation thus appears to be involved in the physiopathology of exercise-induced cough in this ovalbumin sensitized rabbit model. Inhaled anti-inflammatory treatments could have potential benefit for the management of exercise-induced cough in asthma patients., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Basin, Valentin, Demoulin-Alexikova, Demoulin, Foucaud, Gérard, Pouget, Allado, Chenuel and Poussel.)

Introduction: Cough is a major symptom frequently experienced during exercise, mainly in asthmatic patients. Inhaled glucocorticoids represent the keystone treatment in the management of asthma, but little is known about interactions between cough and exercise, especially in controlled patients. During exercise, cough reflex (CR) appears downregulated in healthy animal models whereas a lack of desensitization of CR has been shown in ovalbumin-sensitized animal models, mimicking asthmatic disease., Aims and Objectives: The goal of our study was to clarify the potential modulation of the CR induced by inhaled corticosteroids (CS) in ovalbumin (OVA) sensitized rabbits during artificial limb exercise., Materials and Methods: Seventeen OVA sensitized rabbits were studied. Among them, 9 were treated with CS delivered intravenously (OVA-Corticoids). The ventilatory response to direct tracheal stimulation, performed at rest and during exercise, was determined to assess the incidence and the sensitivity of the CR. Broncho-alveolar lavage (BAL) and cell counts were performed to determine the level of airway inflammation. Exercise was mimicked by electrically induced hindlimb muscular contractions (EMC)., Results: Compared to rest values, EMC increased minute ventilation by 28% without any decrease in respiratory resistance (Rsr). Among 322 tracheal stimulations, 172 (53%) were performed at rest and 150 (47%) during exercise. The sensitivity of CR decreased during artificial limb exercise compared to baseline in OVA-Corticoids rabbits ( p = 0.0313) while it remained unchanged in OVA rabbits ( p = NS)., Conclusion: Corticosteroids appear to restore the desensitization of the CR in OVA sensitized rabbits during artificial limb exercise, suggesting the potential role of airway inflammation in the pathophysiology of cough during exercise in asthmatics., (Copyright © 2020 Valentin, Chenuel, Demoulin-Alexikova, Demoulin, Gérard, Foucaud and Poussel.)

Multi-center studies in specific airway resistance have shown significant inter laboratory variability. Comparison of plethysmographic equipment using a lung model easily transportable from one site to another should be of help to international normative studies. A resistor made of parallel capillary tubes - insuring adequate linearity within 1 L/sec - was connected to a glass bottle. Thermal time constants were measured while the bottle was empty and while stuffed with steel wool. In the latter, isothermal condition was estimated to occur only at very low frequency (around 0.01 Hz) and gas compression was polytropic up to 0.6 Hz. With the empty analog, adiabatic gas compression was estimated to occur at frequencies ≥0.2 Hz, and more accurate volume estimation was obtained. The empty analog volume and specific resistance measured in a body plethysmograph on different days indicated within 5% accuracy as well as intersession repeatability. It is concluded that a physical analog built out of simple material provides accurate measurements of specific resistance. The apparatus should be of help to compare plethysmographic equipments from different laboratories.

Cough is typically associated with physical activity in children with asthma, but the characteristics of the relationship between cough and exercise has not been established under physiological conditions. The aim of the study was to describe the effect of exercise on the reflex cough response elicited by a single breath of capsaicin in non-asthmatic children. A group of non-asthmatic adults was studied as reference. Thirty children and 29 adults were recruited. The cough reflex sensitivity to capsaicin was first determined to establish the dose that provokes 5 cough efforts (C5). The number of coughs elicited by C5 (NC5) was then compared at baseline and during a standardized submaximal treadmill exercise. Data are expressed as median (interquartile range). Children and adults showed a significant decrease in NC5 (respectively from 5.0 (4.0-6.0) to 2.5 (2.0-4.0), p < 0.0005 and from 6.0 (5.0-7.0) to 2.0 (0.0-3.0, p < 0.0005). During exercise, NC5 was observed to decrease in all adult subjects, but in only 24/30 children (80%, p = 0.02). A trend for a higher incidence of personal and familial atopy was observed in children that lacked cough down-regulation during exercise compared with other children. It is concluded that the cough reflex response to capsaicin is down regulated by exercise in both children and adults. The effect however is less consistently observed in the former. The difference may reflect maturation of descending inhibitory pathways of the cough reflex, but may also be associated to atopy. The data stress the importance of assessing the time relationship of cough and exercise in questionnaire studies of asthma.

Introduction: Cough and expiration reflex are major lower airway defense mechanisms that have not been studied throughout development in relation with the feeding behavior. Aim: To describe airway defense reflexes evoked by mechanical stimulation of the trachea in developing rabbit pups. Material and Methods: Sixty one pups were allocated to 3 groups according to their feeding behavior: suckling ( n = 22), weanling ( n = 21) and weaning ( n = 18) group. The incidence and sensitivity of defense reflexes triggered by mechanical tracheal stimulation were studied in anesthetized and tracheotomized animals. Data are expressed as median (25th to 75th percentile). Results: The overall incidence of defensive responses (cough and/or expiration reflex) was found to be significantly higher in suckling [100% (50-100%); p = 0.01] and weanling [75% (40-100%); p = 0.05] animals when compared to weaning ones [37.5% (0-75%)]. However, cough motor pattern accounted for only 29% (0-62%) of all defensive responses in suckling rabbits and its frequency was significantly lower in this group when compared with weanling [100%(50-100%); p = 0.006] or weaning group [62%(50-100%), p = 0.05]. In other word the expiration reflex was the dominant response in suckling animals. Conclusion: Incidence and motor pattern of defensive responses were found to be linked to the pup feeding behavior and the expiration reflex was the major response triggered in suckling pups. The results suggest that this reflex is especially fitted to occur during the coordinated swallowing - breathing fast activities of sucking.