Breathing pattern during induced bronchoconstriction

Abstract

The breathing patterns of normal subjects monitored with respiratory inductive plethysmography were investigated after mild increases in respiratory resistance provoked by aerosolized methacholine during natural breathing and while breathing on a mouthpiece to a pneumotachograph. First, during natural breathing, comparisons of inspiratory ventilation (VI), tidal volume (VT), frequency (f), inspiratory time (TI), fractional inspiratory time (TI/TT), and mean inspiratory flow (VT/TI) were made before and after aerosolized buffered saline and methacholine in a dose that reduced specific airway conductance (sGaw) by 35% (PD35). There was a significant increase in VT/TI and VI after methacholine, whereas VT, f, TI, and TI/TT were not consistently modified by saline or methacholine. Pretreatment with bronchodilators prevented changes in respiratory resistance (Rrs) as well as in breathing pattern after PD35 methacholine. On another day, Rrs, end-expiratory lung volume level, and breathing pattern during natural breathing were monitored after administration of predetermined doses of methacholine that reduced sGaw by 25% (PD25), PD35, and 55% (PD55). Increases in VT/TI and end-expiratory lung volume level paralleled the increases in Rrs after each dose of methacholine but not with saline control. VI increased along with Rrs at the PD25 and PD35 doses but plateaued at the PD55 dose while Rrs continued to rise. There were no changes in breathing pattern in subjects who breathed on a mouthpiece to a pneumotachograph after PD55 methacholine. Thus alterations of the breathing pattern due to mild-to-moderate degrees of bronchoconstriction are characterized by progressive rises of mean inspiratory flow (an index of respiratory center drive) and end-expiratory lung volume level (a measure of pulmonary hyperinflation), but VI plateaus at the more severe degree of bronchoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Dioxide Accumulation during Small Animal, Whole Body Plethysmography: Effects on Ventilation, Indices of Airway Function, and Aerosol Deposition

“…Whereas penh and FDP have been applied to examination of bronchoconstricting aerosol dose response characteristics 58 and correlate well with more traditional measures of AR, 15,28,30,3 2 both may be influenced by CO 2 -induced elevation of ventilation in a manner that could be confused with an aerosol effect. Changes in ventilation, breathing pattern, and passive mechanics (Te and Tt) 59 and respiratory drive (Ti/Tt) 60 thought to be characteristic of AR can occur in the absence of bronchoconstriction, 8,26,61,62 and it is possible that the same is true of these nondimensional parameters.…”

Airway reactivity response to aged carbon–graphite/epoxy composite material smoke

“…Respiratory duty cycle elevation also has been attributed to neuromuscular fatigue 41 but not to administration of methacholine. 36 Hamelmann and colleagues 28 demonstrated P enh to be an indicator of bronchoconstriction induced by methacholine in mice, which correlated well with more direct measures of AR, intrapleural pressure and pulmonary resistance. Although P enh was shown to be independent of changes in f, a limited proportional dependence of P enh upon V t was demonstrated.…”

“…36 Carbondioxide in the exposure atmosphere may have elicited specific changes in the ventilation and breathing pattern, which could either augment or suppress the actions of other smoke constituents. We have found that CO 2 in the plethysmographs reaches ca.…”

Continuous electronic data capture of physiology, behavior and experience in real life: towards ecological momentary assessment of emotion

“…Similar to mean inspiratory flow, but less dependent on accurate estimation of the onset and end of inspiration Ventilation/peak inspiratory flow Measure of appropriateness of ventilation to respiratory drive. Helps distinguish organic from psychogenic breathlessness (Chadha et al, 1984) Fractional inspiratory time 'Duty cycle' (Ti/Tt, ratio of inspiratory to total breath time). Low values may reflect severe airways obstruction since expiratory time is prolonged.…”