Influência da ventilação assistida e dos ajustes do ventilador mecânico sobre o volume corrente e as pressões alveolares na síndrome do desconforto respiratório agudo: um estudo de bancada / Influences of assisted breathing and mechanical ventilator settings on tidal volume and alveolar pressures in acute respiratory distress syndrome: a bench study

RESUMO Objetivo: Avaliar a influência dos esforços musculares respiratórios e do ajuste da frequência respiratória no ventilador sobre o volume corrente e as pressões de distensão alveolar ao final da inspiração e expiração com ventilação sob os modos controle por volume e controle por pressão na síndrome do desconforto respiratório agudo. Métodos: Utilizou-se um simulador mecânico de pulmão (ASL 5000™) conectado a cinco tipos de ventiladores utilizados em unidade de terapia intensiva, em um modelo de síndrome do desconforto respiratório agudo. Os esforços musculares respiratórios (pressão muscular) foram configurados de três formas distintas: sem esforço (pressão muscular: 0cmH2O), apenas esforços inspiratórios (pressão muscular: - 5cmH2O, tempo inspiratório neural de 0,6 segundos) e esforços musculares inspiratórios e expiratórios (pressão muscular:-5/+5cmH2O). Foram configuradas ventilação sob os modos controle por volume e ventilação com controle por pressão para oferecer um volume corrente de 420mL e pressão positiva expiratória final de 10cmH2O. Avaliaram-se o volume corrente fornecido aos pulmões, as pressões alveolares no final da inspiração e as pressões alveolares no final da expiração. Resultados: Quando disparado pelo paciente simulado, o volume corrente mediano foi 27mL menor do que o volume corrente ajustado (variação-63 a +79mL), e ocorreu uma variação nas pressões alveolares com mediana de 25,4cmH2O (faixa de 20,5 a 30cmH2O). Nos cenários simulados com esforço muscular tanto inspiratório quanto expiratório e com frequência respiratória mandatória inferior à dos esforços do paciente simulado, o volume corrente mediano foi maior com ventilação controlada. Conclusão: O ajuste do esforço muscular respiratório e da frequência respiratória no ventilador em um valor acima da frequência respiratória do paciente nos modos de ventilação assistida/controlada gerou maiores variações no volume corrente e nas pressões pulmonares, enquanto o modo controlado não mostrou variações nesses desfechos.

ABSTRACT Objective: To evaluate the influences of respiratory muscle efforts and respiratory rate setting in the ventilator on tidal volume and alveolar distending pressures at end inspiration and expiration in volume-controlled ventilation and pressure-controlled ventilation modes in acute respiratory distress syndrome. Methods: An active test lung (ASL 5000™) connected to five intensive care unit ventilators was used in a model of acute respiratory distress syndrome. Respiratory muscle efforts (muscle pressure) were configured in three different ways: no effort (muscle pressure: 0cmH2O); inspiratory efforts only (muscle pressure:-5cmH2O, neural inspiratory time of 0.6s); and both inspiratory and expiratory muscle efforts (muscle pressure:-5/+5cmH2O). Volume-controlled and pressure-controlled ventilation modes were set to deliver a target tidal volume of 420mL and positive end-expiratory pressure of 10cmH2O. The tidal volume delivered to the lungs, alveolar pressures at the end of inspiration, and alveolar pressures at end expiration were evaluated. Results: When triggered by the simulated patient, the median tidal volume was 27mL lower than the set tidal volume (range-63 to +79mL), and there was variation in alveolar pressures with a median of 25.4cmH2O (range 20.5 to 30cmH2O). In the simulated scenarios with both spontaneous inspiratory and expiratory muscle efforts and with a mandatory respiratory rate lower than the simulated patient's efforts, the median tidal volume was higher than controlled breathing. Conclusion: Adjusting respiratory muscle effort and pulmonary ventilator respiratory rate to a value above the patient's respiratory rate in assisted/controlled modes generated large variations in tidal volume and pulmonary pressures, while the controlled mode showed no variations in these outcomes.

Assessment of ability of medical and obstetric students to achieve adequate positive pressure ventilation using basic neonatal resuscitation manikins / Evaluación de la habilidad de los estudiantes de medicina y obstetricia para lograr una ventilación con presión positiva adecuada utilizando maniquíes básicos de reanimación neonatal

ABSTRACT Introduction. The ability to perform adequate positive pressure ventilation is necessary for neonatal clinical practice. However, there are few studies on the achievements of undergraduate students on this task. It is necessary to assess health science students' adequate positive pressure ventilation because it is vital at the beginning of their clinical activity. Objective. To evaluate the cognitive and procedural ability related to adequate positive pressure ventilation performed by 6th year medicine students and 4th year obstetrics students at a public university in Lima, Peru. Methods. We surveyed 78 medical and obstetric students in their last years of studies within six months of taking a course on neonatal resuscitation that included positive pressure ventilation theory and practice. Participants voluntarily agreed to participate in this study. Previously, we validated the survey by asking three experienced neonatologists for their expert judgments on improving the survey. The survey consists of three theoretical questions as a cognitive assessment and three practice assessment criteria qualified by observing performance using neonatal manikins. Results. Medicine students had a better practical ability (p <0.001) than obstetrics students, and obstetrics students presented better theoretical knowledge (p = 0.019). However, both groups achieved limited performance within six months of taking the neonatal clinical practice course as 21.8% of all students passed both the theoretical and practical parts of this study. Conclusion. Participants from both schools require further training alternatives to achieve adequate positive pressure ventilation performance.

RESUMEN Introducción. Una adecuada ventilación con presión positiva es necesaria para la práctica clínica neonatal. Sin embargo, pocos estudios describen los logros de estudiantes de pregrado en esta tarea. Es necesario evaluar la adecuada ventilación con presión positiva en los estudiantes de ciencias de la salud porque es una tarea vital al inicio de su actividad clínica. Objetivo. Evaluar habilidades cognitivas y procedimentales relacionadas con la adecuada ventilación con presión positiva de estudiantes del 6º año de medicina y 4º de obstetricia de una universidad pública de Lima, Perú. Métodos. Encuestamos a 78 estudiantes de medicina y obstetricia dentro de los seis meses posteriores a su curso sobre reanimación neonatal que incluía la teoría y la práctica de la ventilación con presión positiva. Los alumnos participaron voluntariamente en este estudio. Previamente, validamos la encuesta con la opinión de tres neonatólogos sobre cómo mejorarla. La encuesta consta de tres preguntas teóricas de evaluación cognitiva y tres criterios de evaluación práctica calificados mediante observación del desempeño en maniquíes. Resultados. Los estudiantes de medicina tuvieron mejor habilidad práctica (p <0.001) y los estudiantes de obstetricia presentaron mejores conocimientos teóricos (p = 0.019). Sin embargo, ambos grupos lograron un rendimiento global limitado debido a que solamente el 21,8% de todos los estudiantes aprobaron simultáneamente las evaluaciones teórica y práctica de este estudio. Conclusión. Los participantes de ambas escuelas requieren más alternativas de entrenamiento para alcanzar un rendimiento adecuado en la realización de la ventilación con presión positiva en maniquíes neonatales.

Efeitos de técnicas respiratórias no clearance mucociliar, força e fluxo expiratório no pós-operatório de revascularização do miocárdio / Effects of respiratory techniques in the mucociliary clearance, strength and expiratory flow in the post-operative myocardial revascularization

Introdução: Técnicas respiratórias são fundamentais no pós-operatório de cirurgia cardíaca a fim de reduzir complicações pós-operatórias. Objetivos: Comparar duas técnicas de fisioterapia respiratória no clearance mucociliar, força muscular respiratória e obstrução de vias aéreas após cirurgia cardíaca. Métodos: Foram avaliados 32 pacientes submetidos à cirurgia de revascularização do miocárdio, alocados para o grupo respiração por pressão positiva intermitente ou para o grupo exercício de respiração profunda. As avaliações foram compostas de: força muscular respiratória (pressão expiratória máxima e da pressão inspiratória máxima), pico de fluxo respiratório e clearance mucociliar (através do teste do tempo de transito da sacarina, expresso em minutos); e realizadas em três momentos: pré-operatório e pós-operatório antes e após a aplicação das técnicas. Resultados: Na análise do transporte mucociliar, força muscular respiratória e pico de fluxo expiratório, a comparação entre os momentos antes e após a aplicação das técnicas não apresentaram diferenças significativas (transporte mucociliar: p = 0,3844, Pimáx p = 0,2244; Pemáx p = 0,4968; Peak flow p = 0,8383). Nas análises individuais de cada grupo, puderam ser observadas diferenças significativas nas variáveis de força muscular respiratória e pico de fluxo expiratório (p<0.0001). Conclusão: Não foram observadas diferenças significativas entre as técnicas, porém foram eficientes no clearance mucociliar, força muscular e pico de fluxo expiratório quando avaliadas separadamente.

Introduction: Respiratory techniques are fundamental in the postoperative period of cardiac surgery in order to reduce postoperative complications. Objectives: The aim of this study was to compare two techniques of respiratory physiotherapy in mucociliary clearance, respiratory muscle strength and airway obstruction after cardiac surgery. Methods: Thirty-two patients undergoing coronary artery bypass grafting were assigned to the intermittent positive pressure group or to the deep breathing exercise group. The evaluations were composed of: respiratory muscle strength (maximal expiratory pressure and maximal inspiratory pressure), peak respiratory flow and mucociliary clearance (through the saccharine transit time test, expressed in minutes); And performed in three moments: preoperative and postoperative before and after the application of the techniques. Results: In the analysis of mucociliary transport, respiratory muscle strength and peak expiratory flow, the comparison between the moments before and after the application of the techniques did not present significant differences (mucociliary transport: p = 0.3844, Pimax p = 0.2244; = 0.4968; Peak flow p = 0.8383). In the individual analyzes of each group, significant differences were observed in the variables of respiratory muscle strength and peak expiratory flow (p <0.0001). Conclusion: There were no significant differences between the techniques, but were efficient in mucociliary clearance, muscle strength and peak expiratory flow when evaluated separately.

Effects of Various F1O2 on Central and Mixed Venous Oxygen Saturation during Mechanical Ventilation / 대한마취과학회지

BACKGROUND: It is invasive and accompanies various risks to insert pulmonary artery catheter in order to measure mixed venous oxygen saturation (SvO2) that is associated with patients clinical course and prognosis. If there is relationship between central venous oxygen saturation (ScvO2) and mixed venous oxygen saturation, we can use the central venous oxygen saturation instead of mixed venous oxygen saturation to monitor and treat patients. METHODS: We inserted the Swan-Ganz catheter in 20 patients (male 8, female l2) scheduled for undergoing open heart surgery and accomplished the blood gas analysis of the radial arterial blood, central venous blood and mixed venous blood during postoperative respiratory care in intensive care unit at F1O2 1.0, 0.6 and 0.4 in order. RESULTS: There was no significant difference between central venous blood and mixed venous blood in respect to pH, PCO2, PO2. except the mixed venous blood pH at F1O2 0.6 that is greater than the central venous blood pH at F1O2 0.6. Central venous oxygen saturation and mixed venous saturation were not significantly different and showed the following close relationship: SvO2(%)=15.41+0.80XScvO2 (R=0.88, p<0.05). In respect to the difference according to the variation of F1O2, the SO2 and PO2 at F1O2. 1.0 were higher than the SO2 and PO2 at F1O2 0.6 and 0.4, but the differnce between F1O2 0.6 and 0.4 was not significant. CONCLUSIONS: We might conclude that central venous oxygen saturation might be replaced for the mixed venous oxygen saturation in respiratory care after open heart surgery in adults.