Mechanical ventilation saves lives, but it is an intervention fraught with the potential for serious complications. Prevention of these complications has become the focus of research and critical care in the last twenty years. This thesis presents the first use, or the application under new conditions, of three technologies that could contribute to optimization of mechanical ventilation. Optoelectronic plethysmography was used in Papers I and II for continuous assessment of changes in chest wall volume, configuration, and motion in the perioperative period. A forced oscillation technique (FOT) was used in Paper III to evaluate a novel positive end-expiratory pressure (PEEP) optimization strategy. Finally, in Paper IV, FOT in conjunction with an optical sensor based on a self-mixing laser interferometer (LIR) was used to study the oscillatory mechanics of the respiratory system and to measure the chest wall displacement. In Paper I, propofol anesthesia decreased end-expiratory chest wall volume (VeeCW) during induction, with a more pronounced effect on the abdominal compartment than on the rib cage. The main novel findings were an increased relative contribution of the rib cage to ventilation after induction of anesthesia, and the fact that the rib cage initiates post-apneic ventilation. In Paper II, a combination of recruitment maneuvers, PEEP, and reduced fraction of inspired oxygen, was found to preserve lung volume during and after anesthesia. Furthermore, the decrease in VeeCW during emergence from anesthesia, associated with activation of the expiratory muscles, suggested that active expiration may contribute to decreased functional residual capacity, during emergence from anesthesia. In the lavage model of lung injury studied in Paper III, a PEEP optimization strategy based on maximizing oscillatory reactance measured by FOT resulted in improved lung mechanics, increased oxygenation, and reduced histopathologic evidence of ventilator-induced lung injury. Paper IV showed that it is possible to apply both FOT and LIR simultaneously in various conditions ranging from awake quiet breathing to general anesthesia with controlled mechanical ventilation. In the case of LIR, an impedance map representing different regions of the chest wall showed reproducible changes during the different stages that suggested a high sensitivity of the LIR-based measurements.

Made available in DSpace on 2014-12-17T15:16:19Z (GMT). No. of bitstreams: 1 MurilloFLC_DISSERT.pdf: 1116563 bytes, checksum: 0ce3679bea0b52e58c079903ac1afc85 (MD5) Previous issue date: 2013-03-28 / Objetivo: Determinar os efeitos agudos de diferentes intensidades de press?o expirat?ria positiva sobre o padr?o respirat?rio e volumes operacionais de pacientes com doen?a de Parkinson. M?todos: Foram eleitos para o estudo 23 pacientes em est?gios II ou III da doen?a, estando na condi??o ON , sendo 8 exclu?dos, e 15 controles saud?veis. Os indiv?duos foram submetidos a uma avalia??o inicial, constando de dados gerais, avalia??o antropom?trica, fun??o pulmonar e for?a muscular respirat?ria. Ap?s esta etapa inicial, realizou-se a avalia??o dos volumes pulmonares com pletismografia optoeletr?nica associado a utiliza??o de press?o expirat?ria positiva (PEP) em tr?s intensidades de press?o positiva, 10 cmH2O, 15 cmH2O e 20 cmH2O em ordem aleat?ria. Resultados: O grupo Parkinson apresentou valores espirom?tricos e de for?a muscular respirat?ria significativamente menores que o grupo controle (p<0.01). Houve diferen?a nos valores de volume corrente (Vt) do grupo Parkinson em rela??o ao grupo controle na respira??o tranq?ila (p<0.001) e aumento no Vt do grupo Parkinson com uso das tr?s intensidades de PEP (p<0.001), sem diferen?as estatisticamente significativas entre as intensidades e com diferen?a na distribui??o compartimental do Vt entre os grupos (p<0.001). O fluxo inspirat?rio m?dio e o volume minuto do grupo Parkinson foram menores em rela??o ao grupo controle na respira??o tranq?ila (p<0.001) e aumentaram com o uso das tr?s intensidades de PEP (p<0.001), sem diferen?as estatisticamente significativas entre as intensidades. Houve diferen?a na varia??o dos volumes operacionais entre os grupos em todas as intensidades de PEP (p < 0.001). O volume pulmonar expirat?rio final n?o aumentou no grupo Parkinson com uso de PEP. O volume pulmonar inspirat?rio final aumentou no grupo Parkinson em todas intensidades de PEP (p < 0.001), n?o havendo diferen?as entre as intensidades. Conclus?o: Os pacientes com doen?a de Parkinson apresentam altera??es em diferentes componentes do padr?o respirat?rio e a terapia com PEP determina modifica??es clinicamente importantes nos volumes pulmonares, considerando a intensidade de 10 cmH2O suficientes para este objetivo terap?utico