Characterization of expiratory flow limitation by de signals of the nasal pressure cannula

• Grant number: 22/14295-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: December 01, 2022
• End date: November 30, 2024
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal Investigator: Pedro Rodrigues Genta
• Grantee: Daniela Ohlweiler Brescovit
• Host Institution: Instituto do Coração Professor Euryclides de Jesus Zerbini (INCOR). Hospital das Clínicas da Faculdade de Medicina da USP (HCFMUSP). Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil
• Associated research grant: 18/20612-4 - Pathophysiology of Obstructive Sleep Apnea applied to therapeutic improvement, AP.JP

Abstract

Nasal breathing can happen during inspiration and expiration, or even as an isolated event during expiration[1]. The morphological analysis of the nasal airflow curve can be used to identify the oral pattern of expiration[2]. This condition is called Expiratory Flow Limitation (EFL) and can be identified in the airflow signal by the cut of the expiratory curve[2][3]. An event of expiratory flow limitation occurs due to the prolapse of the velopharynx during expiration, which causes nasopharynx obstruction and in consequence the airflow outlet through the oral cavity[2]. Despite being apparently common, no study has sistematically mesured the EFL frequency. Many evidences are suggestive that EFL has clinical relevance, but it is still unknown if EFL protects or worsen OSA. During EFL the nasopharynx is obstructed by the palatal prolapse. EFL can reduce the tidal volume because of the inefficient inspiratory effort, which has to overtake the positive pressure in the end of expiration in order to open the palate. On this hand, LFE can worsen the OSA. On the other hand, EFL can promote a positive pressure at the end of the expiration that causes air escape through mouth with semienclosed lips[2,4]. There is a consequent increase in pulmonar volume on sequential breathings under EFL. The increased pulmonar volume can improve pharyngeal patency by the traction of the trachea. The increased pulmonar volume pull the trachea, which tenses mediastinal structures and, finally, the pharyngeal walls, making them less prone to collapse. Therefore, EFL could protect against the OSA[2, 4].In this project, we are going to evaluate the pattern of EFL detected by the signal of the nasal pressure cannula. It is going to be determined the frequency of EFL in pacients referred to polysomnography under suspect of OSA. It is also going to be evaluated if EFL protects or worsen OSA. Our hypothesis is that sequential breathings under EFL end more frequently with arousals than spontaneously, which shows the deleterious effect of the EFL.