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Anatomy of the Respiratory Neural Network
Published in Susmita Chowdhuri, M Safwan Badr, James A Rowley, Control of Breathing during Sleep, 2022
Christopher A Del Negro, Christopher G Wilson
Post-inspiration immediately follows inspiration. It is generally present—and beneficial—during eupnea but not obligatory. Post-inspiration is generally lost in vitro because brainstem-spinal cord preparations retain inspiratory rhythmogenic (preBötC) and expiratory rhythmogenic (pFL) sites. Slice preparations retain only the preBötC. Nevertheless, preparations that include the pons can generate postinspiratory activity measurable via CN IX and CN X (162, 163).
Gasping
Published in Alan D. Miller, Armand L. Bianchi, Beverly P. Bishop, Neural Control of the Respiratory Muscles, 2019
In many of the studies considered above, gasping has been reversibly produced by exposing animals to anoxia. Once gasping commences, reintroduction of normoxia or hyper-oxia results in a reestablishment of eupnea. To emphasize the clinical importance of gasping, a corollary must be stated: gasping can serve to provide a reoxygenation of the animal and reverse a life-threatening episode. Indeed, “it is thus quite plausible to hypothesize that a failure of autoresuscitation is the final and most devastating physiologic failure in SIDS victims (sudden infant death syndrome).”9
Spinal cord injury and diaphragm neuromotor control
Published in Expert Review of Respiratory Medicine, 2020
Matthew J. Fogarty, Gary C. Sieck
To accommodate the diverse pressure generation requirements of these motor behaviors, the diaphragm muscle comprises different motor unit types: slow (type S), fast fatigue resistant (type FR), fast fatigue intermediate (FInt) and fast fatiguable [1,2,5,10,23–26] (Figure 1). These mixed motor unit types furnish two broad groups of motor units whose properties denote their behavioral functions: a first set of lower force but highly fatigue-resistant motor units (type S and FR) that efficiently generate adequate Pdi to sustain breathing even under more extreme conditions [10,27], and a second set of higher force but more fatigable motor units (type FInt and FF) that are optimally primed for short-duration bursts of force generation approaching Pdimax [1]. The first set of inspiratory-related motor units is best considered as ‘the tidal pool’, responsible for generating the tidal volume during eupnea. The FInt and FF diaphragm motor units are not required for ventilation, despite their motor neurons residing in the phrenic pool and their constituent muscle fibers being distributed throughout the diaphragm muscle [28].
Obstructive sleep apnea: personalizing CPAP alternative therapies to individual physiology
Published in Expert Review of Respiratory Medicine, 2022
Brandon Nokes, Jessica Cooper, Michelle Cao
There are several additional metrics traditionally obtained from CPAP dial down techniques which are now routinely modeled from clinical polysomnography in specialized research labs [29,30]. As noted, the ‘passive’ upper airway refers to the behavior of the upper airway in the absence of muscular activity. During CPAP dial down studies, ‘optimum CPAP’ is first obtained and refers to the CPAP level at which the upper airway is unobstructed and ventilatory demands are being adequately met during non-rapid eye movement (NREM) sleep [29]. Over the course of several minutes of unobstructed breathing in NREM sleep, ventilation at eupnea (Veupnea) is established. The CPAP can then be dropped to 0 cmH2O for 3–5 seconds and ventilation through the passive airway (Vpassive) can be obtained [29]. It should be noted that CPAP quiets upper airway dilator activity, and during the first 1–2 breaths of the Vpassive CPAP drop, there is insufficient time for upper airway dilators to activate, thus providing insight into the ‘passive’ behaviors of the upper airway [29]. Notably, while the above techniques are helpful in separating the relative contribution of passive anatomy versus airway dilator activity in airway collapse, accounting for the overlapping role in neural drive perturbations has proven more difficult. For example, recent work from Gell et al., as well as Messineo et al., suggests that many obstructive events, including those in rapid eye movement (REM) sleep, are preceded by a common loss of ventilatory drive (both at the level of genioglossus and the diaphragm) [31,32]. Thus, truly separating the role of the mechanical upper airway from ventilatory drive has proven be quite difficult.