Banca de DEFESA: FELIPE XAVIER DE MELO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : FELIPE XAVIER DE MELO
DATE: 16/12/2022
TIME: 08:30
LOCAL: Plataforma Teams
TITLE:

Analysis of extrathoracic airway dynamics against cough assistant maneuvers in a Starling resistor analog model.

KEY WORDS:

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PAGES: 70
BIG AREA: Ciências da Saúde
AREA: Medicina
SUMMARY:

Introduction: Neuromuscular diseases represent a heterogeneous group of diseases with diverse phenotypes that share common pathophysiological pathways and generate various respiratory manifestations, such as reduced lung volumes, greater collapse in extrathoracic airways, impaired ability to cough, reduced clearance of airway secretions and recurrent infections. In order to reduce morbidity and mortality, the use of cough assistants can optimize the clearing of secretions and reduce the incidence of recurrent infections in these patients. Recently, optimized assistant maneuvers have been described which, in an experimental setting, were able to displace more secretion through a rigid tube. However, the influence of the complex dynamics of the extrathoracic airway on the effectiveness of the maneuvers has not been considered. In individuals affected by these diseases, the upper airways may be pathologically compromised by a combination of hypotonia of the pharyngeal dilator muscles and reduced longitudinal tissue tension resulting from the caudal traction exerted by the thoracic structures. Both changes culminate in reduced airway diameter and a tendency to collapse, which severely limits the application of this technique. Objectives: To analyze the influence of chamber pressure and longitudinal strain in determining flows and pressures during traditional and optimized mechanical insufflationexsufflation maneuvers in an experimental analog Starling resistor model. Methodology: An experimental study was conducted in the Respiratory Physiology Laboratory of the University of Brasilia with a Starling resistor coupled to a cough assistant and fixed compliance test lung. Combinations of chamber pressure (Pchamber), 0 cmH2O, -3 cmH2O and -5 cmH2O, and longitudinal strain (strain), 0%, 12.5%, 25%, 37.5% and 50%, were applied to standard and optimized maneuvers with pressures of +30/-30 and +40/-40 cmH2O configured in the cough assistant. Pressure and flow curves generated by the maneuvers were recorded, from which we extracted the data of interest: peak inspiratory flow (PFI), proximal pressure at peak inspiratory flow (Pupstream Insp), chamber pressure at peak inspiratory flow (Pcamber Insp), distal pressure at peak inspiratory flow (Pdownstream Insp), proximal pressure at zero flow (Pupstream V0); chamber pressure at zero flow (Pchamber V0); distal pressure at zero flow (Pdownstream V0), peak expiratory flow (PEF); proximal pressure at peak expiratory flow (Pupstream Exp); distal pressure at peak expiratory flow (Pdownstream Exp). Subsequently, bias flow was calculated, through the PEF/PFI difference PEF-PFI ratio. For statistical analysis, Split-plot design was used to evaluate the effect of Pcamber, strain and Pcamber*strain interaction in determining the flows and pressures studied. Results: During insufflation, there was a statistical difference between the peak flows obtained and between the peak pressures recorded, and this difference was due in most maneuvers and combinations to the interaction between Pcamber and strain. For all maneuvers performed, the mean peak flow was higher around the 12.5% and 25% strain and Pcamber between 0 and -3 cmH2O, representing better coupling for adequate insufflation with these combinations. In the zero flow phase, between inspiration and expiration, the interaction between Pcamber and strain was also a determinant of the equilibrium pressures achieved. However, the effective values reached were close to the pressures configured in the cough assistant, exerting little influence on airway patency in this phase. Finally, in the exsufflation phase there was no statistical difference between the peak flow obtained and between most of the peak pressures recorded. Conclusions: During the insufflation phase, the competence of the airway dilator mechanisms is able to significantly influence the effectiveness of the cough assistant in promoting adequate inspiration. The combinations between Pcamber and strain that generate higher PFI are in agreement with previously described literature data, which found an ideal strain around 25%, where there was no airflow limitation. In the exhaled phase, the absence of statistical significance in relation to the manipulations of Pcamber and strain suggest that regardless of the adjustment made, the system is more susceptible to flow limitation and collapse due to the high negative pressures usually applied by the cough assistant in this phase. This inability of the compensatory adjustments of the airway to withstand high negative pressures may represent a greater limitation of the application of the cough assistant in the expiratory phase. Our study therefore suggests the need to evaluate in further studies strategies to optimize the expiratory phase of the cough assistant maneuvers, such as the effect of lower exsufflation pressures on flow limitation and airway collapse, and the effectiveness of clearing secretions.

BANKING MEMBERS:
Externo à Instituição - BRUNO DO VALLE PINHEIRO - UFJF
Externo à Instituição - DANTE BRASIL SANTOS - HUB
Externo à Instituição - SERGIO LEITE RODRIGUES - HUB
Presidente - 1189371 - VERONICA MOREIRA AMADO