Effects of ventilation, humidity and temperature on airway responsiveness to methacholine in rats

Abstract

Exercise-induced bronchoconstriction is associated with heat and water loss from the airways. It is not known whether these conditions can influence the response to bronchoactive agonists. The effects of different degrees of alveolar ventilation on the pulmonary response to methacholine and the role of humidity and temperature in this response were evaluated.Wistar rats were anaesthetized, tracheostomized and mechanically ventilated. Increasing doses of methacholine were infused intravenously and respiratory system resistance (Rrs) and elastance (Ers) were measured. The rats were ventilated with dry air at 13uC, dry air at 37uC, humid air at 13uC and humid air at 37uC. These four groups were further divided into three subgroups with a respiratory frequency adjusted to reach a carbon dioxide tension in arterial blood of 30, 40 and 50 mmHg.Temperature, humidity and level of alveolar ventilation did not influence the position of the dose/response curve to methacholine. However, the maximal changes in Ers were significantly lower in the rats ventilated with humid air. In addition, maximal changes in Ers were significantly higher in the rats with lower alveolar ventilation. These differences were not observed for maximal values of Rrs.The pulmonary response to methacholine in normal rats is significantly affected by the humidity of inspired air and the level of alveolar ventilation. This influence is more intense in the small airways and/or distal airspaces. This suggests that exercise or hyperventilation can change the behaviour of airway smooth muscle.

Indoor air quality, ventilation and respiratory health in elderly residents living in nursing homes in Europe

“…Countries with lower socio-environmental conditions where extreme temperature conditions can be observed showed greater adverse health impacts [34]. Relative humidity was inversely associated with wheeze in the past year and usual cough in our study, which is not consistent with previous literature showing that humidity is a well-known risk factor for asthma, wheezing and asthma-like symptoms in the long term [35,36]; however, in an animal model humidity did not influence the position of the dose-response curve to methacholine in the short term [37].…”

The Effect of Serine Protease Inhibitors on Airway Inflammation in a Chronic Allergen-Induced Asthma Mouse Model

“…The Rrs and Ers are two important coefficients for tracheal pressure (Ptr) according to an equation of respiratory system motion: Ptr = Ers × V ( t ) + Rrs × V ′( t ), where t is time, V is lung volume change, and V ′ is airflow. When allergen enter the airway can induce airway obstruction, it increases Rrs and Ers levels for airway resistance in asthma [20, 21]. In this study, treatment with the three serine protease inhibitors suppressed Rrs and Ers values and airway inflammation and remodeling.…”

Climate change, extreme weather events, air pollution and respiratory health in Europe

“…Some studies showed that in both healthy and asthmatic subjects humidity may decrease lung capacity and increase airways resistance [117,118], while in others humidity did not influence non-specific airway Evidence of greater risk for asthma admission in ,15 year-olds and all ages during the dust days compared with non-dust days (lag 0); not significant for older age groups Effect on respiratory admissions in ,15 years, 15-64 years, all ages No effect on .65 years old PM: particulate matter; PM10: particulate matter with a diameter ,10 mm; PM2.5-10: particulate matter with a diameter o2.5 mm and ,10 mm; PM2.5: particulate matter with a diameter ,2.5 mm. hyperresponsiveness [119]. Humidity may also indirectly affect respiratory allergic diseases by influencing atmospheric levels of aeroallergens, with low humidity favouring release, dispersion and transport of pollen [120,121].…”