External mechanical loading in conscious humans: role of upper airway mechanoreceptors

Abstract

To determine whether upper airway mechanoreceptors partly subserve the ventilatory response to external mechanical loading in conscious humans, we studied 11 laryngectomized subjects. The oropharynx (OP) or tracheostomy was selectively loaded (in random order) by attaching the mouth or tracheal tube to a special pressure-generating apparatus, and steady-state ventilatory responses were recorded. Phasic negative pressure changes generated at the OP to simulate inspiratory resistive loading, expiratory resistive unloading, and elastic loading resulted in trivial prolongation of inspiratory duration by 12, 9, and 4%, respectively; other ventilatory variables were not significantly altered. Phasic positive pressure changes at the OP that simulated inspiratory resistive unloading and expiratory resistive loading had little effect on breathing pattern. When the above loads were applied via the tracheostomy, using pressures of similar magnitude, ventilatory responses were qualitatively similar and quantitatively not significantly different from those of normal healthy controls. The results suggest that the OP does not make an important contribution to ventilatory responses during external mechanical loading in conscious humans. Loading responses to conventional mechanical loads are preserved in the absence of afferent information from the upper airways.

Functional magnetic resonance imaging reveals brain regions mediating the response to resistive expiratory loads in humans.

“…In contrast, upper airway mechanoreceptors and corresponding afferent projections are not important contributors to the ventilatory response (36). It should also be emphasized that marked differences in ribcage coordination and ventilatory strategy are observed when expiratory loads are applied to conscious versus anesthetized humans, suggesting that cortical or more rostral mechanisms are operative, and greatly modify respiratory compensation to obstructive loads (37).…”

Mechanical loading promotes mast cell degranulation via RGD-integrin dependent pathways

“…collagen, fibronectin). Mast cells are increasingly associated with pathophysiological conditions, such as cardiovascular (Kelley et al, 2000; Brower and Janicki, 2005; Levick et al, 2009) and pulmonary diseases (O’Donnell et al, 1988; Duranti et al, 1995); therefore identifying and understanding alternative pathways involved in their activation may further define the role of mast cells in disease.…”

“…The mechanical loads applied to extracellular matrices (ECM) are essential in maintaining tissue homeostasis (Riser et al, 1992; Wang et al, 1993; Gupta and Grande-Allen, 2006); however deviations in matrix mechanics can activate pathological signaling pathways and/or induce cellular stress responses (O’Donnell et al, 1988; Duranti et al, 1995; Gupta and Grande-Allen, 2006). Numerous pathways have been identified through which mechanical forces are transduced into biological signals (Hamill and Martinac, 2001).…”

Role of hyperinflation vs. deflation on dyspnoea in severely to extremely obese subjects

“…In the first case obese subjects have to increase EEV L to escape from flow limitation and are probably unable to do that without increasing EIV L (Babb 1999, Babb et al 2002, DeLorey et al 2005. In the second case, with expiration becoming active, a progressive reduction in EEV L below the resting functional residual capacity would result in dynamic airway compression and collapse, and breathlessness (O'Donnell et al 1987(O'Donnell et al , 1988. In the second case, with expiration becoming active, a progressive reduction in EEV L below the resting functional residual capacity would result in dynamic airway compression and collapse, and breathlessness (O'Donnell et al 1987(O'Donnell et al , 1988.…”