Regular ArticleEntrainment of the Respiratory Rhythm: A New Approach
Abstract
When we periodically perturbed the central respiratory oscillator with a controlled periodic stimulation provided by a mechanical ventilator, an entrainment phenomenon occurred: the actual rhythm of the respiratory centres was phase locked to the periodic stimulation. In some experiments, we observed an intermittence phenomenon: the respiratory rhythm successively seemed entrained, departed from this mode for few cycles, returned to the previous pseudo entrainment and so on. From intermittence data, we were able to plot a phase response curve. From literature data on the effects of a single stimulation applied at various moments in the respiratory cycle, we built up a mathematical model designed to simulate entrainment experiments. This model simulated entrainment phenomenon, but did not satisfactorily accommodate the experimental phase response curve. The section of the simulated phase response curve responsible for discrepancies was the result of the combination of an inspiratory shortening owing to a stimulation occurring during inspiration, and a positive relationship between inspiratory duration TI and expiratory duration TE. We changed the TE —TI relationship, assuming that the expiratory duration is determined not by the inspiratory duration but rather by the lung volume at the end of inspiration. The revised model was then able to exhibit almost all the qualitative properties previously noted in experiments. The significance in biological terms of the new TE —TI relationship, which is apparently incompatible with almost all previous experimental data, is discussed.
References (0)
Cited by (15)
Prevalence of Reverse Triggering in Early ARDS: Results From a Multicenter Observational Study
2021, ChestThe prevalence of reverse triggering (RT) in the early phase of ARDS is unknown.
During early ARDS, what is the proportion of patients affected by RT, what are its potential predictors, and what is its association with clinical outcomes?
This was prospective, multicenter, and observational study. Patients who met the Berlin definition of ARDS with less than 72 h of mechanical ventilation and had not been paralyzed with neuromuscular blockers were screened. A 30-min recording of respiratory signals was obtained from the patients as soon as they were enrolled, and the number of breaths with RT were counted.
One hundred patients were included. ARDS was mild to moderate in 92% of them. The recordings were obtained after a median of 1 day (interquartile range, 1-2 days) of ventilation. Fifty patients had RT, and most of these events (97%) were not associated with breath stacking. Detecting RT was associated with lower tidal volume (Vt) and less opiate infusion. The presence of RT was not associated with time to discontinuation of mechanical ventilation (subdistribution hazard ratio, 1.03; 95% CI, 0.6-1.77), but it possibly was associated with a reduced hospital mortality (hazard ratio, 0.65; 95% CI, 0.57-0.73).
Fifty percent of patients receiving assist-control ventilation for mild or moderate ARDS, sedated and nonparalyzed, demonstrate RT without breath stacking on the first day of mechanical ventilation. RT may be associated with low VTS and opiate doses.
ClinicalTrials.gov; No.: NCT02732041; URL: www.clinicaltrials.gov.
Diaphragmatic muscle contractions triggered by ventilator insufflations constitute a form of patient-ventilator interaction referred to as “entrainment,” which is usually unrecognized in critically ill patients. Our objective was to review tracings, which also included muscular activity, obtained in sedated patients who were mechanically ventilated to describe the entrainment events and their characteristics. The term “reverse triggering” was adopted to describe the ventilator-triggered muscular efforts.
Over a 3-month period, recordings containing flow, airway pressure, and esophageal pressure or electrical activity of the diaphragm were reviewed. Recordings were obtained from a series of consecutive heavily sedated patients ventilated with an assist-control mode of ventilation for ARDS. The duration of entrainment, the entrainment ratio, and the phase difference elapsing between the commencement of the ventilator and neural breaths were evaluated.
The tracings of eight consecutive patients with ARDS were reviewed; they all showed different forms of entrainment. Reverse triggering occurred over a portion varying from 12% to 100% of the total recording period. Seven patients had a 1:1 mechanical insufflation to diaphragmatic contractions ratio; this coexisted with a 1:2 ratio in one patient and 1:2 and 1:3 ratios in another. One patient exhibited only a 1:2 ratio. The frequency of reverse-triggered breaths had a mean coefficient of variability of < 5%, very close to the variability of mechanical breaths.
To our knowledge, this is the first time that the presence of respiratory entrainment in sedated, critically ill adult patients who are mechanically ventilated has been documented. The “reverse-triggered” breaths illustrate a new form of neuromechanical coupling with potentially important clinical consequences.
Central pattern generation and the motor infrastructure for suck, respiration, and speech
2006, Journal of Communication DisordersThe objective of the current report is to review experimental findings on centrally patterned movements and sensory and descending modulation of central pattern generators (CPGs) in a variety of animal and human models. Special emphasis is directed toward speech production muscle systems, including the chest wall and orofacial complex during patterned motor output. Experimental results indicate that CPGs subserving orofacial motor behavior can be modulated via descending and sensory inputs. This feature of control may also operate in the control of other centrally patterned motor behaviors including speech breathing, suck, mastication, and the recombination of CPG processes for the development and production of speech.
Learning outcomes: Readers will be able to: (1) define the salient characteristics of CPGs, (2) list five factors which influence the development and operation of a CPG over the lifespan, (3) define sensorimotor entrainment of CPGs, and (4) describe one new application for therapeutic training of the non-nutritive suck in premature infants.
Adjustment of the human respiratory system to increased upper airway resistance during sleep
2002, Bulletin of Mathematical BiologyA cardiorespiratory model incorporating control of the human upper airway during sleep is described. Most previous models have not considered the possibility that the upper airway could be a limiting factor for gas exchange. Our model was developed to also predict certain pathophysiological phenomena in the cardiorespiratory system that characterize heavy snoring or sleep apnea. We started by adapting our collapsible upper airway model to include the impact of nasal passage and larynx, and extended the model with equations for gas exchange in the lungs. A feedback loop both to the respiratory pump and the upper airway dilator muscles was included. The model enabled successful breath-by-breath simulations of obstructive events of the upper airway. Although the model incorporates several physiologically relevant components of the system, the simulation results suggest that only few parameters suffice to predict the key adjustments that the cardiorespiratory system is known to make in patients with heavy snoring.
Compact set valued flows II: Applications in biological modelling
1997, Comptes Rendus de l'Academie de Sciences - Serie IIb: Mecanique, Physique, Chimie, AstronomieCompact set valued iterations generalize classical point iterations by replacing the function ƒ with a tube ƒ expressing the uncertainty about experimental data and allowing the study of the structural stability of Poincaré maps or phase response curves: logistic (Section 2) and respiratory (Section 3) examples show that bifurcation schemes are roughly respected. Finally, the problem of robustness of Poincaré maps or phase response curves used in physiology or embryology is discussed in Section 4.
Les itérations à valeurs compactes généralisent les itérations ponctuelles classiques, dans lesquelles on remplace la fonction f à itérer par un tube fonctionnel f, exprimant l'incertitude des donnéees expérimentales et permettant l'étude de la stabilité structurelle des applications de Poincaré ou des courbes de réponse de phase. Les exemples des itérations logistiques (§ 2) et celles de l'entraînement du rythme respiratoire (§ 3), montrent que les schémas de bifurcation des itérations ponctuelles sont grossièrement respectés. Enfin, dans la section 4, nous discutons la robustesse des applications de premier retour et des courbes de réponse de phase en physiologie et en embryologie.
Reverse Trigger in Ventilated Non-ARDS Patients: A Phenomenon Can Not Be Ignored!
2021, Frontiers in Physiology