Evidencia que tres ciclos de prono aumentan la PaO2/FiO2 en el enfermo de neumonía por COVID-19 / Evidence that three prone cycles increase PaO2/FiO2 in patients with COVID-19 pneumonia

Introducción: Es posible deducir la mejoría o empeoramiento del intercambio gaseoso en el paciente con COVID-19 en ventilación mecánica invasiva mediante el índice PaO2/FiO2 tras el uso de la posición prono. Objetivos: Identificar los cambios en el índice PaO2/FiO2 tras el uso de tres ciclos de prono, y detallar las características sociodemográficas de los pacientes. Material y métodos: En este estudio descriptivo y retrospectivo se analizaron los expedientes clínicos de 60 pacientes con COVID-19, se tomaron en cuenta valores de PaO2/FiO2, saturación de oxígeno y datos sociodemográficos. Resultados: Con el uso de tres ciclos de posición prono de 24 horas cada uno, en promedio la PaO2/FiO2 aumentó 26.38 mmHg (20%) y la saturación de oxígeno aumentó un 6.3%. 66.7% de la población eran hombres, y el promedio de edad fue de 67.10 años. Limitación: Hubo limitaciones de carácter retrospectivo debido al contexto de la pandemia de COVID-19 y la alta carga de trabajo que imposibilitó la adecuada recolección de información relevante, como los tipos de tratamiento farmacológico y de soporte vital empleados. Conclusiones: El uso de la posición prono en el paciente orointubado con COVID-19 constituye una estrategia de primera línea, pues ha demostrado un aumento en la PaO2/FiO2, que resulta en una mejoría en la oxigenación/perfusión.

Introduction: The improvement or worsening of gas exchange in patients with COVID-19 on invasive mechanical ventilation can be determined through the PaO2/FiO2 index after using the prone position. Objectives: To identify changes in the PaO2/FiO2 index after three prone cycles, and to describe the sociodemographic characteristics of the patients. Material and methods: In this descriptive and retrospective study, the clinical records of 60 patients with COVID-19 were analyzed, PaO2/FiO2 oxygen saturation values and sociodemographic data were considered. Results: With the use of three prone position cycles of 24 hours each, on average, the PaO2/FiO2increased by 26.38 mmHg (20.09%) and oxygen saturation increased by 6.3%. Male population represented 66.7%, and the average age was 67.10 years. Limitation: There was retrospective limitations due to the COVID-19 pandemic context and high workload, which made difficult to adequately record relevant information, including types of pharmacological and life support treatments used. Conclusions: The prone position used on orointubated patient with COVID-19 constitutes a first-line strategy; it has shown an increase in PaO2/FiO2 values, which leads to an improvement in oxygenation/perfusion.

Falla respiratoria aguda: Hace 50 años, Hoy y Dentro de 50 años. Una revisión narrativa / Acute respiratory failure: 50 years ago, today and 50 years from now. A narrative review

The management of acute respiratory failure may require, among other measures, airway control, mechanical ventilation, and hemodynamic stabilization. About 60% of critically ill patients will require some type of respiratory support. For these reasons, an understanding of respiratory pathophysiology is important. The aim of this review is to establish an up-to-date of the concepts and fundamentals for acute respiratory failure.

El manejo de la falla respiratoria aguda puede requerir, entre otras medidas, control de la vía aérea, ventilación mecánica y estabilización hemodinámica. Alrededor del 60% de los pacientes graves requerirán de algún tipo de soporte respiratorio. Por estas razones es importante el entendimiento de la fisiopatología respiratoria. El objetivo de esta revisión es establecer conceptos y fundamentos actualizados sobre la falla respiratoria aguda.

Exercise Training Improved Pulmonary Gas Exchange Abnormalities in Pulmonary Hypertension due to Heart Failure: A Case Report

Abstract Heart failure (HF) is the most common cause of pulmonary hypertension (PH), and reduced exercise capacity and exertional dyspnea are the most frequent concerns in patients with PH-HF. Indeed, carbon dioxide end-tidal partial pressure (PETCO 2 ) during exercise is a well-established noninvasive marker of ventilation/perfusion ratio in PH. We aimed to evaluate the effect of aerobic exercise training on PETCO 2 response during exercise in a 59-year-old woman with PH secondary to idiopathic dilated cardiomyopathy. The patient with chronic fatigue and dyspnea at mild-to-moderate efforts was admitted to a cardiorespiratory rehabilitation program and had her cardiorespiratory response to exercise assessed during a cardiopulmonary exercise testing performed before and after three months of a thrice-weekly aerobic exercise training program. Improvements in aerobic capacity (23.9%) and endurance time (37.5%) and reduction in ventilatory inefficiency (-20.2%) was found after intervention. Post-intervention improvements in PETCO 2 at ventilatory anaerobic threshold (23.3%) and change in PETCO 2 kinetics pattern, with progressive increases from rest to peak of exercise, were also found. Patient also improved breathing pattern and timing of ventilation. This case report demonstrated for the first time that aerobic exercise training might be able to improve PETCO 2 response during exercise in a patient with PH-HF.

Deterioro del intercambio gaseoso en sujetos con incremento del índice de masa corporal a una altitud de 2, 240 metros sobre el nivel del mar / Deterioration of gas exchange in subjects with an increase in body mass index at an altitude of 2, 240 meters above sea level

Resumen Introducción: Las alteraciones del intercambio gaseoso se han reconocido en la obesidad mórbida; sin embargo, no se conoce su comportamiento conforme se incrementa el índice de masa corporal. Objetivo: Conocer el comportamiento del intercambio gaseoso a la altura de la Ciudad de México en el desarrollo de obesidad mórbida. Métodos: Mediante un diseño transversal analítico se estudió a sujetos pareados por género y edad de cuatro grupos diferentes de índice de masa corporal (kg/m2): normal (18.5-24.9), sobrepeso (25-29.9), obesidad (30-39.9) y obesidad mórbida (≥ 40). Se obtuvieron sus antecedentes patológicos y demográficos, variables de gasometría arterial y espirometría simple. Las variables se determinaron de acuerdo con las características de la muestra; las diferencias entre grupos se realizaron mediante Anova de una vía con ajuste de Bonferroni, así como la correlación de Pearson para las variables relacionadas. Una p < 0.05 se consideró con significación estadística. Resultados: Se estudió a 560 pacientes en cuatro grupos. La edad promedio fue de 49 ± 11 años. La mayor frecuencia de diabetes mellitus (34.29%), hipertensión arterial (50%) e hiperlipidemia (36.43%) se registró en el grupo de obesidad, y la de roncador (73.57%) en la obesidad mórbida. Se identificaron diferencias desde el grupo normal respecto de la obesidad mórbida: PaCO2 31.37 ± 2.08 vs. 38.14 ± 5.10 mmHg; PaO2 68.28 ± 6.06 vs. 59.86 ± 9.28 mmHg y SaO2 93.51 ± 1.93 vs. 89.71 ± 5.37%, todas con p = 0.0001. Correlación IMC-PaCO2: 0.497, e IMC-PaO2: -0.365, p = 0.0001, respectivamente. Conclusiones: A la altitud de la Ciudad de México y con índice de masa corporal > 30 kg/m2, las variables relacionadas con el intercambio gaseoso y espirometría simple comienzan a deteriorarse; son evidentes con IMC > 40 kg/m2.

Abstract Introduction: Alterations of gas exchange have been recognized in morbid obesity, however, it is not known how their behavior would be as the body mass index increases. Objective: To know the behavior of gas exchange at the level of Mexico City in the development of morbid obesity. Methods: Through analytical design, subjects matched by gender and age were studied from four different groups of body mass index (kg/m2), normal (18.5-24.9), overweight (25-29.9), obesity (30-39.9) and morbid obesity (≥ 40). Their pathological and demographic antecedents, arterial blood gas and simple spirometry variables were obtained. The variables were shown according to their sample characteristic. The differences between groups were made using one way Anova with Bonferroni adjustment, as well as Pearson’s correlation for the related variables. Statistical significance was considered with p < 0.05. Results: 560 subjects were studied in 4 groups. The average age 49 ± 11 years old. The highest frequency of diabetes mellitus (34.29%), arterial hypertension (50%) and hiperlipidemia (36.43%) was in the obesity group, and being snoring (73.57%) in morbid obesity. There were differences from the normal group versus. morbid obesity: PaCO2 31.37 ± 2.08 versus. 38.14 ± 5.10 mmHg; PaO2 68.28 ± 6.06 versus. 59.86 ± 9.28 mmHg and SaO2 93.51 ± 1.93 versus. 89.71 ± 5.37%, all with p = 0.0001. The IMC-PaCO2 correlation: 0.497, and IMC-PaO2: −0.365, p = 0.0001 respectively. Conclusions: At the altitude of Mexico City and body mass index > 30 kg/m2 the variables related to gas exchange and simple spirometry begin to deteriorate; are evident with BMI > 40 kg/m2.

Content analysis of clinical indicators for Impaired gas exchange / Análisis de contenido de indicadores clínicos para Deterioro del intercambio gaseoso / Análise de conteúdo dos indicadores clínicos para Troca de gases prejudicada

ABSTRACT Objective To analyze the relevance of clinical indicators and the clarity and precision of conceptual and operational definitions of the diagnosis Impaired gas exchange. Methods Content analysis, by 39 nurse judges, divided into the phases of conceptual definition of the phenomenon of interest, construction of the structure of the phenomenon of interest and analysis of the judges on the built structure. Results From the 22 indicators, 21 were considered relevant Impaired gas exchange. The indicators that obtained absolute relevance were Cyanosis, Hypercapnia, Hypoxemia and Tachycardia. The indicator Headache upon waking did not show any statistically significant relevance for the diagnosis. All conceptual and operational definitions were clear and precise. Conclusion The indicators listed for Impaired gas exchange were relevant to the phenomenon, except Headache upon waking because it does not correspond to a safe manifestation to identify the diagnosis, according to the analysis of the judges. Each conceptual and operational definition was adequate for its indicator.

RESUMEN Objetivo Analizar la relevancia de los indicadores clínicos y la claridad y precisión de las definiciones conceptuales y operativas del diagnóstico Deterioro del intercambio gaseoso. Métodos Análisis de contenido, realizado por 39 jueces enfermeros, dividido en las fases de definición conceptual del fenómeno de interés, construcción de la estructura del fenómeno de interés y análisis de los jueces sobre la estructura construida. Resultados De los 22 indicadores, 21 fueron considerados relevantes Deterioro del intercambio gaseoso. Los indicadores que obtuvieron relevancia absoluta fueron Cianosis, Hipercapnia, Hipoxemia y Taquicardia. El indicador Cefalea al despertar no mostró relevancia estadísticamente significativa para el diagnóstico. Todas las definiciones conceptuales y operativas fueron claras y precisas. Conclusión Los indicadores enumerados para Deterioro del intercambio gaseoso fueron relevantes para el fenómeno, excepto Cefalea al despertar porque no corresponde a una manifestación segura para identificar el diagnóstico, según el análisis de los jueces. Cada definición conceptual y operativa fue adecuada para su indicador.

RESUMO Objetivo Analisar a relevância dos indicadores clínicos e a clareza e precisão das definições conceituais e operacionais do diagnóstico Troca de gases prejudicada. Métodos Análise de conteúdo, por 39 juízes enfermeiros, dividida nas fases de definição conceitual do fenômeno de interesse, construção da estrutura do fenômeno de interesse e análise dos juízes sobre a estrutura construída. Resultados Dos 22 indicadores, 21 foram considerados relevantes Troca de gases prejudicada. Os indicadores que obtiveram relevância absoluta foram Cianose, Hipercapnia, Hipoxemia e Taquicardia. O indicador Cefaleia ao acordar não apresentou relevância estatisticamente significante para o diagnóstico. Todas as definições conceituais e operacionais foram claras e precisas. Conclusão Os indicadores elencados para Troca de gases prejudicada foram relevantes ao fenômeno, exceto Cefaleia ao acordar pois não corresponde a uma manifestação segura para identificar o diagnóstico, conforme a análise dos juízes. Cada definição conceitual e operacional foi adequada para seu referido indicador.

Fisiología respiratoria: contribución de la estructura de la vía aérea y el pulmón a la función del aparato respiratorio / Contribution of the airways and lung structure to the respiratory system function

Conocer la estructura del sistema respiratorio es fundamental para comprender cómo realiza sus funciones, desde la principal, el intercambio gaseoso, hasta otras funciones no respiratorias tales como el equilibrio ácido-base, fonación, defensa pulmonar, metabolismo pulmonar y procesamiento de materiales bioactivos. El objetivo de esta revisión es describir los conocimientos actuales de la anatomía del aparato respiratorio y mencionar sus funciones tanto respiratorias como no respiratorias.

Knowing the structure of the respiratory system is essential to understand how it performs its various functions, from the main, gas exchange, to its non-respiratory functions such as acid-base balance, phonation, lung defense, pulmonary metabolism, and the handling of bioactive materials. The main objective of this review is to describe the updated knowledge of the respiratory system's anatomy and to mention its various respiratory and non-respiratory functions.

Cuidados de Enfermería al inicio de Ventilación Mecánica Invasiva en la Unidad de Cuidados Intensivos / Nursing Care at the beginning of Invasive Mechanical Ventilation in the Intensive Care Unit

La ventilación mecánica es la alternativa terapéutica que sustituye la función ven-tilatoria total o parcial mientras se man-tienen niveles apropiados de PO2 y PCO2 en sangre arterial, con el fin de disminuir el trabajo respiratorio en los pacientes crí-ticos; principalmente los que presentan insuficiencia respiratoria aguda, por lo que se debe conocer cuándo está indicado este medio de soporte vital avanzado; así como los diferentes modos disponibles, los parámetros y alarmas ventilatorios ge-nerales acoplados a una estrategia de ven-tilación protectora para reducir las com-plicaciones que se puedan producir. De esta manera favorecemos la recuperación del paciente. La Gestión de Enfermería es la disciplina de la ciencia del cuidado que aplica el juicio profesional, la planificación, orga-nización, motivación y control de la pro-visión de procesos oportunos, seguros, humanos e integrales que aseguran la continuidad de la atención. El cuidado enfermero en la UAACI, se realiza de manera autónoma y en colaboración con el equipo de salud, se ajusta a las necesi-dades del paciente crítico, brindando ca-lidad y seguridad, en base a instrumentos que nos permiten monitorizar y evaluar la atención.Según la base de datos de la Unidad de Adultos Área de Cuidados Intensivos año 2018 el 51,4% de los pacientes in-gresados necesitaron apoyo ventilatorio invasivo, de los cuales el 72,0% co-rresponden a insuficiencia respiratoria aguda, el porcentaje restante a procedi-mientos programados. El objetivo de esta ruta es la estandari-zación de los Cuidados de Enfermería al inicio de la ventilación mecánica así como describir las fases de interven-ción de la enfermera y las actividades que debe cumplir en cada una de ellas, estableciendo un plan de cuidados para constatar que los objetivos planteados se consigan.

Mechanical ventilation is the thera-peutic alternative that replaces total or partial ventilatory function while maintaining appropriate levels of PO2 and PCO2 in arterial blood, in order to reduce respiratory work in critical pa-tients; mainly those with acute respi-ratory failure, so it should be known when this means of advanced life su-pport is indicated; as well as the diffe-rent modes available, general venti-lation parameters and alarms coupled to a protective ventilation strategy to reduce the complications that may occur. In this way we favor patient re-covery. Nursing Management is the disci-pline of care science that applies pro-fessional judgment, planning, organi-zation, motivation and control of the provision of timely, safe, human and comprehensive processes that ensure continuity of care. The nursing care in the UAACI is carried out autono-mously and in collaboration with the health team, adjusts to the needs of the critical patient, providing quality and safety, based on instruments that allow us to monitor and evaluate the care.According to the database of the Adult Unit Intensive Care Area year 2018, 51.4% of the admitted patients needed invasive ventilatory support, of which 72.0% correspond to acute respiratory failure, the remaining percentage to scheduled procedures.The objective of this route is the stan-dardization of Nursing Care at the be-ginning of mechanical ventilation as well as describing the phases of in-tervention of the nurse and the acti-vities that must be carried out in each of them, establishing a plan of care to verify that the set goals are achieved.

Impact of lung expansion therapy using positive end-expiratory pressure in mechanically ventilated patients submitted to coronary artery bypass grafting

Abstract Objective: To evaluate the impact of different levels of positive end-expiratory pressure (PEEP) on gas exchange in patients undergoing coronary artery bypass grafting (CABG). Methods: A randomized clinical trial was conducted with patients undergoing CABG surgery. Patients were randomized into three groups: Group 10, PEEP of 10 cmH2O; Group 12, PEEP of 12 cmH2O; and Group 15, PEEP of 15 cmH2O. After the randomization, all patients underwent gas analysis at three moments: (1) before lung expansion therapy (LET); (2) 30 minutes after LET; and (3) one hour after extubation. Results: Sixty-six patients were studied, of which 61.7% were men, with mean age of 64 ± 8.9 years. Patients allocated to Group 15 showed a significant improvement in gas exchange comparing pre- and post-expansion values (239±21 vs. 301±19, P<0,001) and the increase was maintained after extubation (278±26). Despite the use of high levels of PEEP, no significant hemodynamic change was evidenced. Conclusion: It is concluded that high levels of PEEP (15 cmH2O) are beneficial for the improvement of gas exchange in patients undergoing CABG.

Oferta de oxigênio, remoção de dióxido de carbono, transferência de energia aos pulmões e comportamento da hipertensão pulmonar durante o suporte com oxigenação por membrana extracorpórea: um modelo matemático / Oxygen delivery, carbon dioxide removal, energy transfer to lungs and pulmonary hypertension behavior during venous-venous extracorporeal membrane oxygenation support: a mathematical modeling approach

RESUMO Objetivo: Descrever a transferência de energia do ventilador mecânico para os pulmões; o acoplamento entre a transferência de oxigênio por oxigenação por membrana extracorpórea venovenosa (ECMO-VV) e o consumo de oxigênio do paciente; a remoção de dióxido de carbono com ECMO; e o efeito potencial da oxigenação venosa sistêmica na pressão arterial pulmonar. Métodos: Modelo matemático com cenários hipotéticos e utilização de simulações matemáticas por computador. Resultados: A transição de ventilação protetora para ventilação ultraprotetora em um paciente com síndrome da angústia respiratória aguda grave e complacência respiratória estática de 20mL/cmH2O reduziu a transferência de energia do ventilador para os pulmões de 35,3 para 2,6 joules por minuto. Em um paciente hipotético, hiperdinâmico e ligeiramente anêmico com consumo de oxigênio de 200mL/minuto, é possível atingir saturação arterial de oxigênio de 80%, ao mesmo tempo em que se mantém o equilíbrio entre a transferência de oxigênio pela ECMO e o consumo de oxigênio do paciente. O dióxido de carbono é facilmente removido e a pressão parcial de dióxido de carbono normal é facilmente obtida. A oxigenação do sangue venoso, por meio do circuito da ECMO, pode direcionar o estímulo da pressão parcial de oxigênio na vasoconstrição pulmonar por hipóxia para valores normais. Conclusão: A ventilação ultraprotetora reduz amplamente a transferência de energia do ventilador para os pulmões. A hipoxemia grave no suporte com ECMO-VV pode ocorrer, a despeito do acoplamento entre a transferência de oxigênio, por meio da ECMO, e o consumo de oxigênio do paciente. A faixa normal de pressão parcial de dióxido de carbono é fácil de atingir. O suporte com ECMO-VV potencialmente alivia a vasoconstrição pulmonar hipóxica.

ABSTRACT Objective: To describe (1) the energy transfer from the ventilator to the lungs, (2) the match between venous-venous extracorporeal membrane oxygenation (ECMO) oxygen transfer and patient oxygen consumption (VO2), (3) carbon dioxide removal with ECMO, and (4) the potential effect of systemic venous oxygenation on pulmonary artery pressure. Methods: Mathematical modeling approach with hypothetical scenarios using computer simulation. Results: The transition from protective ventilation to ultraprotective ventilation in a patient with severe acute respiratory distress syndrome and a static respiratory compliance of 20mL/cm H2O reduced the energy transfer from the ventilator to the lungs from 35.3 to 2.6 joules/minute. A hypothetical patient, hyperdynamic and slightly anemic with VO2 = 200mL/minute, can reach an arterial oxygen saturation of 80%, while maintaining the match between the oxygen transfer by ECMO and the VO2 of the patient. Carbon dioxide is easily removed, and normal PaCO2 is easily reached. Venous blood oxygenation through the ECMO circuit may drive the PO2 stimulus of pulmonary hypoxic vasoconstriction to normal values. Conclusion: Ultraprotective ventilation largely reduces the energy transfer from the ventilator to the lungs. Severe hypoxemia on venous-venous-ECMO support may occur despite the matching between the oxygen transfer by ECMO and the VO2 of the patient. The normal range of PaCO2 is easy to reach. Venous-venous-ECMO support potentially relieves hypoxic pulmonary vasoconstriction.

Eficácia e segurança da oxigenoterapia com cânula nasal de alto fluxo na insuficiência respiratória hipercápnica moderada aguda / Efficacy and safety of high-flow nasal cannula oxygen therapy in moderate acute hypercapnic respiratory failure

RESUMO Objetivo: Avaliar a eficácia e a segurança da oxigenoterapia com uso de cânula nasal de alto fluxo no tratamento da insuficiência respiratória hipercápnica moderada em pacientes que não conseguem tolerar ou têm contraindicações para ventilação mecânica não invasiva. Métodos: Estudo prospectivo observacional de 13 meses envolvendo participantes admitidos a uma unidade de terapia intensiva com insuficiência respiratória hipercápnica ou durante o processo de seu desenvolvimento. Os parâmetros clínicos e de troca gasosa foram registrados em intervalos regulares durante as primeiras 24 horas. Os parâmetros finais foram saturação de oxigênio entre 88 e 92%, juntamente da redução do esforço respiratório (frequência respiratória) e da normalização do pH (≥ 7,35). Os participantes foram considerados não responsivos em caso de necessidade de utilização de suporte ventilatório. Resultados: Trinta participantes foram tratados utilizando oxigenoterapia com cânula nasal de alto fluxo. Esta foi uma população mista com exacerbação de doença pulmonar obstrutiva crônica, edema pulmonar cardiogênico agudo, e insuficiência respiratória aguda pós-operatória e pós-extubação. Observou-se melhora não significante na frequência respiratória (28,0 ± 0,9 versus 24,3 ± 1,5; p = 0,22), que foi aparente nas primeiras 4 horas do tratamento. Ocorreu melhora do pH, embora só se tenham obtido níveis normais após 24 horas de tratamento com cânula nasal de alto fluxo (7,28 ± 0,02 versus 7,37 ± 0,01; p = 0,02). A proporção de não responsivos foi de 13,3% (quatro participantes), dos quais um necessitou e aceitou ventilação mecânica não invasiva, e três necessitaram de intubação. A mortalidade na unidade de terapia intensiva foi de 3,3% (um participante), e um paciente morreu após a alta para a enfermaria (mortalidade hospitalar de 6,6%). Conclusão: O oxigenoterapia com cânula nasal de alto fluxo é eficaz para a insuficiência respiratória hipercápnica moderada e ajuda a normalizar os parâmetros clínicos e de troca gasosa, com taxa aceitável de não responsivos que necessitaram de suporte ventilatório.

ABSTRACT Objective: To assess the efficacy and safety of high-flow nasal cannula oxygen therapy in treating moderate hypercapnic respiratory failure in patients who cannot tolerate or have contraindications to noninvasive mechanical ventilation. Methods: A prospective observational 13-month study involving subjects admitted to an intensive care unit with or developing moderate hypercapnic respiratory failure. Clinical and gas exchange parameters were recorded at regular intervals during the first 24 hours. The endpoints were a oxygen saturation between 88 and 92% along with a reduction in breathing effort (respiratory rate) and pH normalization (≥ 7.35). Subjects were considered nonresponders if they required ventilatory support. Results: Thirty subjects were treated with high-flow nasal cannula oxygen therapy. They consisted of a mixed population with chronic obstructive pulmonary disease exacerbation, acute cardiogenic pulmonary edema, and postoperative and postextubation respiratory failure. A nonsignificant improvement was observed in respiratory rate (28.0 ± 0.9 versus 24.3 ± 1.5, p = 0.22), which was apparent in the first four hours of treatment. The pH improved, although normal levels were only reached after 24 hours on high-flow nasal cannula therapy (7.28 ± 0.02 versus 7.37 ± 0.01, p = 0.02). The rate of nonresponders was 13.3% (4 subjects), of whom one needed and accepted noninvasive mechanical ventilation and three required intubation. Intensive care unit mortality was 3.3% (1 subject), and a patient died after discharge to the ward (hospital mortality of 6.6%). Conclusion: High-flow nasal cannula oxygen therapy is effective for moderate hypercapnic respiratory failure as it helps normalize clinical and gas exchange levels with an acceptable rate of nonresponders who require ventilatory support.

Investigating the mechanism of the high frequency ventilation for the oscillation airflow between left and right lungs / 生物医学工程学杂志

Traditionally, adequate tidal volume is considered to be a necessary condition to support respiratory patient breathing. But the high frequency ventilation (HFV) with a small tidal volume can still support the respiratory patient breathing well. In order to further explore the mechanisms of HFV, the pendelluft ventilation between left and right lungs was proposed in this paper. And a test platform by using two fresh sheep lungs was developed for investigating the pendelluft ventilation between the left and right lungs. Furthermore, considering the viscous resistance ( ), inertance ( ) and lung compliance ( ) in the lung, a second-order lung ventilation model was designed to inspect and evaluate the pendelluft ventilation between left lung and right lungs. On referring to both results of experiments in practice and simulation in MATLAB Simulink, between the left and right lungs, the phase difference in their airflow happens during HFV at some frequencies. And the pendelluft ventilation between the left and right lungs is resulted by the phase difference, even if the total airflow entering a whole lung is 0. Under HFV, the pendelluft ventilation between left and right lungs will benefit the lungs being more adequately ventilated, and will be improve the utilization rate of oxygen in the lungs.

Effect of intraoperative lung-protective mechanical ventilation on pulmonary oxygenation function and postoperative pulmonary complications after laparoscopic radical gastrectomy

This study aimed to observe the effects of lung-protective ventilation (LPV) on oxygenation index (OI) and postoperative pulmonary complications (PPCs) after laparoscopic radical gastrectomy in middle-aged and elderly patients. A total of 120 patients who were scheduled to undergo laparoscopic radical gastrectomy with an expected time of >3 h were randomly divided into conventional ventilation (CV group) with tidal volume (TV) of 10 mL/kg without positive end-expiratory pressure (PEEP), and lung-protective ventilation (PV group) with 7 mL/kg TV and personal level of PEEP with regular recruitment maneuver every 30 min. Measurements of OI, modified clinical pulmonary infection score (mCPIS), and PPCs were assessed during the perioperative period. Fifty-seven patients in the CV group and 58 in the PV group participated in the data analysis. Patients in the PV group showed better pulmonary dynamic compliance, OI, and peripheral capillary oxygen saturation during and after surgery. The mCPIS was significantly lower in the PV group than in the CV group after surgery. The incidence rate of PPCs was lower in the PV group than in the CV group and the difference was significant in patients whose ventilation time was longer than 6 h in both groups. LPV during laparoscopic radical gastrectomy significantly improved pulmonary oxygenation function and reduced postoperative mCPIS and the incidence of PPCs during the early period after surgery of middle-aged and elderly patients, especially patients whose mechanical ventilation time was longer than 6 h.

Analysis of different levels of positive end-expiratory pressure during lung retrieval for transplantation: an experimental study

Atelectasis and inadequate oxygenation in lung donors is a common problem during the retrieval of these organs. Nevertheless, the use of high positive end-expiratory pressure (PEEP) is not habitual during procedures of lung retrieval. Twenty-one Sprague-Dawley male consanguineous rats were used in the study. The animals were divided into 3 groups according to the level of PEEP used: low (2 cmH2O), moderate (5 cmH2O), and high (10 cmH2O). Animals were ventilated with a tidal volume of 6 mL/kg. Before lung removal, the lungs were inspected for the presence of atelectasis. When atelectasis was detected, alveolar recruitment maneuvers were performed. Blood gasometric analysis was performed immediately. Finally, the lungs were retrieved, weighed, and submitted to histological analysis. The animals submitted to higher PEEP showed higher levels of oxygenation with the same tidal volumes PO2=262.14 (PEEP 2), 382.4 (PEEP 5), and 477.0 (PEEP 10). The occurrence of atelectasis was rare in animals with a PEEP of 10 cmH2O, which therefore required less frequent recruitment maneuvers (need for recruitment: PEEP 2=100%, PEEP 5 =100%, and PEEP 10=14.3%). There was no change in hemodynamic stability, occurrence of pulmonary edema, or other histological injuries with the use of high PEEP. The use of high PEEP (10 cmH2O) was feasible and probably a beneficial strategy for the prevention of atelectasis and the optimization of oxygenation during lung retrieval. Clinical studies should be performed to confirm this hypothesis.

Avaliação do tamanho do pulmão em cães: a capacidade inspiratória define o volume corrente / Sizing the lung in dogs: the inspiratory capacity defines the tidal volume

RESUMO Objetivo: Avaliar uma nova abordagem fisiológica para a determinação do volume corrente em ventilação mecânica, de acordo com a capacidade inspiratória, e determinar se isso resulta em medidas mecânicas e de troca gasosa adequadas em cães saudáveis e em estado crítico. Métodos: Incluíram-se, neste estudo, 24 animais para avaliar o volume corrente expresso como porcentagem da capacidade inspiratória. Para mensuração da capacidade inspiratória, o ventilador mecânico foi regulado como segue: modo controle de pressão, com 35cmH2O de pressão de inspiração e pressão expiratória final de zero, por 5 segundos. Subsequentemente, estudaram-se dez cães em condições clínicas críticas. Resultados: Cães saudáveis ventilados com volume corrente que correspondia a 17% da capacidade inspiratória demonstraram mecânica respiratória normal e apresentaram os valores previstos de PaCO2 mais frequentemente do que os animais nos demais grupos. A pressão no sistema respiratório e a pressão transpulmonar foram significantemente mais elevadas nos cães em condição crítica, porém em todos os casos, estiveram abaixo de 15cmH2O. Conclusões: O volume corrente calculado com base na capacidade inspiratória de cada animal comprovou ser uma ferramenta útil e simples para o estabelecimento dos parâmetros do ventilador. Convém também realizar abordagem semelhante em outras espécies, inclusive no ser humano, quando se consideram as potenciais limitações da titulação do volume corrente, com base no peso corpóreo ideal calculado.

ABSTRACT Objective: To evaluate a novel physiological approach for setting the tidal volume in mechanical ventilation according to inspiratory capacity, and to determine if it results in an appropriate mechanical and gas exchange measurements in healthy and critically ill dogs. Methods: Twenty healthy animals were included in the study to assess the tidal volume expressed as a percentage of inspiratory capacity. For inspiratory capacity measurement, the mechanical ventilator was set as follows: pressure control mode with 35cmH2O of inspired pressure and zero end-expiratory pressure for 5 seconds. Subsequently, the animals were randomized into four groups and ventilated with a tidal volume corresponding to the different percentages of inspiratory capacity. Subsequently, ten critically ill dogs were studied. Results: Healthy dogs ventilated with a tidal volume of 17% of the inspiratory capacity showed normal respiratory mechanics and presented expected PaCO2 values more frequently than the other groups. The respiratory system and transpulmonary driving pressure were significantly higher among the critically ill dogs but below 15 cmH2O in all cases. Conclusions: The tidal volume based on the inspiratory capacity of each animal has proven to be a useful and simple tool when setting ventilator parameters. A similar approach should also be evaluated in other species, including human beings, if we consider the potential limitations of tidal volume titration based on the calculated ideal body weight.

Cardiorespiratory and metabolic determinants during moderate and high resistance exercise intensities until exhaustion using dynamic leg press: comparison with critical load

The objective of this study was to assess cardiovascular, respiratory, and metabolic responses during a commonly used dynamic leg press resistance exercise until exhaustion (TEx) at different intensities and compare with critical load (CL). This was a prospective, cross-sectional, controlled, and crossover study. Twelve healthy young men (23±2.5 years old) participated. The subjects carried out three bouts of resistance exercise in different percentages of 1 repetition maximum (60, 75, and 90% 1RM) until TEx. CL was obtained by means of hyperbolic model and linearization of the load-duration function. During all bout intensities, oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (VE), and respiratory exchange ratio (RER) were obtained. Variations (peak-rest=Δ) were corrected by TEx. In addition, systolic and diastolic blood pressure (SBP and DBP), blood lactate concentration [La-] and Borg scores were obtained at the peak and corrected to TEx. CL induced greater TEx as well as number of repetitions when compared to all intensities (P<0.001). During CL, Borg/TEx, ΔSBP/TEx, ΔDBP/TEx, and [La-] were significantly lower compared with 90% load (P<0.0001). In addition, VO2, VCO2, VE, and RER were higher during CL when compared to 90 or 75%. TEx was significantly correlated with VO2 on CL (r=0.73, P<0.05). These findings support the theory that CL constitutes the intensity that can be maintained for a very long time, provoking greater metabolic and ventilatory demand and lower cardiovascular and fatigue symptoms during resistance exercise.

Use of cardiopulmonary exercise testing to assess early ventilatory changes related to occupational particulate matter

Spirometry has been used as the main strategy for assessing ventilatory changes related to occupational exposure to particulate matter (OEPM). However, in some cases, as one of its limitations, it may not be sensitive enough to show abnormalities before extensive damage, as seen in restrictive lung diseases. Therefore, we hypothesized that cardiopulmonary exercise testing (CPET) may be better than spirometry to detect early ventilatory impairment caused by OEPM. We selected 135 male workers with at least one year of exposure. After collection of self-reported socioeconomic status, educational level, and cardiovascular risk data, participants underwent spirometry, CPET, body composition assessment (bioelectrical impedance), and triaxial accelerometry (for level of physical activity in daily life). CPET was performed using a ramp protocol on a treadmill. Metabolic, cardiovascular, ventilatory, and submaximal relationships were measured. We compared 52 exposed to 83 non-exposed workers. Multiple linear regressions were developed using spirometry and CPET variables as outcomes and OEPM as the main predictor, and adjusted by the main covariates. Our results showed that OEPM was associated with significant reductions in peak minute ventilation, peak tidal volume, and breathing reserve index. Exposed participants presented shallower slope of ΔVT/ΔlnV̇E (breathing pattern), i.e., increased tachypneic breathing pattern. The OEPM explained 7.4% of the ΔVT/ΔlnV̇E variability. We found no significant influence of spirometric indices after multiple linear regressions. We conclude that CPET might be a more sensitive feature of assessing early pulmonary impairment related to OEPM. Our cross-sectional results suggested that CPET is a promising tool for the screening of asymptomatic male workers.