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.

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.

Effect of different levels of peep on oxygenation during non-invasive ventilation in patients submitted to cabg surgery: randomized clinical trial

Abstract Introduction: During and after coronary artery bypass grafting, a decline in multifactor lung function is observed. Due to this fact, some patients may benefit from non-invasive ventilation after extubation targeting lung expansion and consequently improved oxygenation. Objective: To test the hypothesis that higher levels of positive end expiration pressure during non-invasive ventilation improves oxygenation in patients undergoing coronary artery bypass grafting. Methods: A randomized clinical trial was conducted at Instituto Nobre de Cardiologia in Feira de Santana. On the first day after surgery, the patients were randomized: Group PEEP 10, Group PEEP 12 and Group PEEP 15 who underwent non-invasive ventilation with positive end expiration pressure level. All patients were submitted to analysis blood pressure oxygen (PaO2), arterial oxygen saturation (SaO2) and oxygenation index (PaO2/FiO2). Results: Thirty patients were analyzed, 10 in each group, with 63.3% men with a mean age of 61.1±12.2 years. Mean pulmonary expansion pre-therapy PaO2 was generally 121.9±21.6 to 136.1±17.6 without statistical significance in the evaluation among the groups. This was also present in PaO2/FiO2 and SaO2. Statistical significance was only present in pre and post PEEP 15 when assessing the PaO2 and SaO2 (P=0.02). Conclusion: Based on the findings of this study, non-invasive ventilation with PEEP 15 represented an improvement in oxygenation levels of patients undergoing coronary artery bypass grafting.

Pendelluft diagnosed from ventilator weaning indexes obtained through bioelectrical impedance tomography: a case report / Pendelluft diagnosticado através de índices de desmame ventilatório obtidos pela tomografia de bioimpedância elétrica: um relato de caso

ABSTRACT CONTEXT: Today, through major technological advances in diagnostic resources within medicine, evaluation and monitoring of clinical parameters at the patient's bedside in intensive care units (ICUs) has become possible. CASE REPORT: This case report presents results and interpretations from predictive mechanical ventilation weaning indexes obtained through monitoring using chest electrical bioimpedance tomography. These indexes included maximum inspiratory pressure, maximum expiratory pressure, shallow breathing index and spontaneous breathing test. These were correlated with variations in tidal volume variables, respiratory rate, mean arterial pressure and peripheral oxygen saturation. Regarding the air distribution behavior in the pulmonary parenchyma, the patient showed the pendelluft phenomenon. Pendelluft occurs due to the time constant (product of the airways resistance and compliance) asymmetry between adjacent lung. CONCLUSION: Bioelectrical impedance tomography can help in weaning from mechanical ventilation, as in the case presented here. Pendelluft was defined as a limitation during the weaning tests.

RESUMO CONTEXTO: Atualmente, com o grande avanço tecnológico em recursos para diagnósticos em medicina, a avaliação e a monitorização de parâmetros clínicos à beira leito de paciente em unidade de terapia intensiva (UTI) se tornou possível. RELATO DE CASO: Neste relato de caso, apresentam-se os resultados e a interpretação de índices preditivos de desmame da ventilação mecânica obtidos pela tomografia de bioimpedância elétrica torácica. Esses índices incluíram a pressão inspiratória máxima, pressão expiratória máxima, índice de respiração superficial e teste de respiração espontânea. Estes estavam correlacionados com as variações de volume corrente, frequência respiratória, pressão arterial média e saturação periférica de oxigênio. Quanto ao comportamento da distribuição de ar no parênquima pulmonar, o paciente apresentou o fenômeno pendelluft. O pendelluft ocorre dado pela constante de tempo (produto da resistência e complacência das vias aéreas) de forma assimétrica entre as unidades pulmonares adjacentes. CONCLUSÃO: A tomografia de bioimpedância pode auxiliar no desmame da ventilação mecânica, como no caso apresentado. Pendelluft foi definido como limitação durante a execução dos testes para desmame.

Effect of exercise training on ventilatory efficiency in patients with heart disease: a review

The analysis of ventilatory efficiency in cardiopulmonary exercise testing has proven useful for assessing the presence and severity of cardiorespiratory diseases. During exercise, efficient pulmonary gas exchange is characterized by uniform matching of lung ventilation with perfusion. By contrast, mismatching is marked by inefficient pulmonary gas exchange, requiring increased ventilation for a given CO2 production. The etiology of increased and inefficient ventilatory response to exercise in heart disease is multifactorial, involving both peripheral and central mechanisms. Exercise training has been recommended as non-pharmacological treatment for patients with different chronic cardiopulmonary diseases. In this respect, previous studies have reported improvements in ventilatory efficiency after aerobic exercise training in patients with heart disease. Against this background, the primary objective of the present review was to discuss the pathophysiological mechanisms involved in abnormal ventilatory response to exercise, with an emphasis on both patients with heart failure syndrome and coronary artery disease. Secondly, special focus was dedicated to the role of aerobic exercise training in improving indices of ventilatory efficiency among these patients, as well as to the underlying mechanisms involved.

Evaluation of the Efficiency of the Atraumatic Endotracheal Tube in the Pulmonary-Gas Exchange: an Experimental Study

ABSTRACT OBJECTIVE: Mechanical ventilation is frequently necessary, in which case the use of an endotracheal tube is mandatory. The tube has an inflatable balloon in its distal extremity, whose aim is, among other functions, an efficient arterialization. However, serious injuries in the place of contact of the balloon with the trachea can be frequent. Some studies point out that balloons with permanent pressure may reduce this complication. Nevertheless, air scape, expressed by the inspiratory (IV) and expiratory volume (EV) variation (Δ IV-EV), may occur, possibly leading to hypoxemia. Thus, the goal of this study was to verify the efficiency of a modified endotracheal tube on arterializations compared to the traditional endotracheal tube. METHODS: The modified endotracheal tube presents intermittent insufflation, with three drillings in the internal region of the cuff, allowing for insufflation in the inspiratory phase of the mechanical ventilation. Three animals were used for the control group, with a cuff pressure of 30 cmH2O, and seven pigs had the modified endotracheal tube. Each animal was kept under mechanical ventilation (FIO2=0.21) for 6 hours. Arterial and venous gases were measured every three hours (T0; T3; T6). RESULTS: The gases confirmed the lack of hypoxia between the Groups, with a difference in the ΔIV-EV at T0 (P=0.0486). CONCLUSIONS: In this study, the lack of hypoxia showed the efficiency of the modified endotracheal tube. However, new studies are necessary, particularly in diseased lungs, in order to evaluate the real efficiency of the mentioned device on the pulmonary gas exchange.

Prevalence of lung structure abnormalities in patients with acromegaly and their relationship with gas exchange: cross-sectional analytical study with a control group / Prevalência de alterações na estrutura pulmonar em pacientes com acromegalia e sua relação com a troca gasosa: estudo transversal analítico com grupo controle

CONTEXT AND OBJECTIVE: Different functional respiratory alterations have been described in acromegaly, but their relationship with pulmonary tissue abnormalities is unknown. The objective of this study was to observe possible changes in lung structure and explain their relationship with gas exchange abnormalities. DESIGN AND SETTING: Cross-sectional analytical study with a control group, conducted at a university hospital. METHODS: The study included 36 patients with acromegaly and 24 controls who were all assessed through high-resolution computed tomography of the thorax (CT). Arterial blood gas, effort oximetry and serum growth hormone (GH) and insulin-like growth factor I (IGF-1) were also assessed in the patients with acromegaly. RESULTS: The abnormalities found in the CT scan were not statistically different between the acromegaly and control groups: mild cylindrical bronchiectasis (P = 0.59), linear opacity (P = 0.29), nodular opacity (P = 0.28), increased attenuation (frosted glass; P = 0.48) and decreased attenuation (emphysema; P = 0.32). Radiographic abnormalities were not associated with serum GH and IGF-1. Hypoxemia was present in seven patients; however, in six of them, the hypoxemia could be explained by underlying clinical conditions other than acromegaly: chronic obstructive pulmonary disease in two, obesity in two, bronchial infection in one and asthma in one. CONCLUSION: No changes in lung structure were detected through thorax tomography in comparison with the control subjects. The functional respiratory alterations found were largely explained by alternative diagnoses or had subclinical manifestations, without any plausible relationship with lung structural factors.

CONTEXTO E OBJETIVO: Diferentes alterações funcionais respiratórias são descritas na acromegalia. Sua relação com anormalidades do tecido pulmonar é desconhecida. O objetivo foi observar possíveis alterações da estrutura pulmonar e explicar sua relação com anormalidades da troca gasosa. TIPO DE ESTUDO E LOCAL: Estudo transversal, analítico, com grupo de controle, realizado em um hospital universitário. MÉTODOS: Incluíram-se 36 pacientes com acromegalia e 24 controles que foram avaliados com tomografia computadorizada de alta resolução de tórax (TC); os acromegálicos também foram avaliados com gasometria arterial, oximetria de esforço e dosagens de hormônio de crescimento (GH) e fator de crescimento semelhante à insulina (IGF-1). RESULTADOS: As alterações encontradas na TC não foram estatisticamente diferentes entre os grupos acromegálico e de controle: bronquiectasia cilíndrica leve (P = 0,59), opacidades lineares (P = 0,29), opacidades nodulares (P = 0,28), aumento da atenuação (vidro fosco) (P = 0,48) e redução da atenuação (enfisema; P = 0,32). As alterações radiológicas não se relacionaram com as dosagens de GH e IGF-1. Hipoxemia estava presente em sete pacientes; contudo, em seis deles a hipoxemia poderia ser explicada por condição clínica subjacente diversa da acromegalia: doença pulmonar obstrutiva crônica em dois, obesidade em dois, infecção brônquica em um e asma em um. CONCLUSÕES: Não foram observadas alterações da estrutura pulmonar por tomografia de tórax, quando comparadas ao grupo de controle; as alterações funcionais respiratórias encontradas são explicáveis em grande parte por diagnósticos alternativos, ou se manifestam de forma subclínica, não apresentando relação plausível com o aspecto da estrutura pulmonar.

Alterações da mecânica ventilatória durante a fisioterapia respiratória em pacientes ventilados mecanicamente / Changes in respiratory mechanics during respiratory physiotherapy in mechanically ventilated patients

RESUMO Objetivo: Avaliar as alterações da mecânica ventilatória e da hemodinâmica que ocorrem em pacientes dependentes de ventilação mecânica submetidos a um protocolo padrão de fisioterapia respiratória. Métodos: Estudo experimental e prospectivo realizado em duas unidades de tratamento intensivo, nas quais pacientes dependentes de ventilação mecânica por mais de 48 horas foram alocados, de forma consecutiva, e submetidos a um protocolo estabelecido de manobras de fisioterapia respiratória. Variáveis ventilatórias (complacência pulmonar dinâmica, resistência do sistema respiratório, volume corrente, pressão de pico inspiratório, frequência respiratória e saturação periférica de oxigênio) e hemodinâmicas (frequência cardíaca) foram mensuradas 1 hora antes (T-1), imediatamente (T0) e após 1 hora (T+1) da realização do protocolo de manobras de fisioterapia respiratória. Resultados: Durante o período de coleta dos dados, 104 pacientes foram incluídos no estudo. Quanto às variáveis ventilatórias, houve aumento da complacência pulmonar dinâmica (T-1 = 52,3 ± 16,1mL/cmH2O versus T0 = 65,1 ± 19,1mL/cmH2O; p < 0,001), do volume corrente (T-1 = 550 ± 134mL versus T0 = 698 ± 155mL; p < 0,001) e da saturação periférica de oxigênio (T-1 = 96,5 ± 2,29% versus T0 = 98,2 ± 1,62%; p < 0,001), além de redução da resistência do sistema respiratório (T-1 = 14,2 ± 4,63cmH2O/L/s versus T0 = 11,0 ± 3,43cmH2O/L/s; p < 0,001) logo após a realização das manobras de fisioterapia respiratória. Todas as alterações se mantiveram na avaliação realizada 1 hora (T+1) após as manobras de fisioterapia respiratória. Já com relação às variáveis hemodinâmicas, houve elevação imediata, porém não sustentada da frequência cardíaca (T-1 = 88,9 ± 18,7bpm versus T0 = 93,7 ± 19,2bpm versus T+1 = 88,5 ± 17,1bpm; p < 0,001). Conclusão: Manobras de fisioterapia respiratória geram mudanças imediatas na mecânica pulmonar e na hemodinâmica dos pacientes dependentes da ...

ABSTRACT Objective: To evaluate the changes in ventilatory mechanics and hemodynamics that occur in patients dependent on mechanical ventilation who are subjected to a standard respiratory therapy protocol. Methods: This experimental and prospective study was performed in two intensive care units, in which patients dependent on mechanical ventilation for more than 48 hours were consecutively enrolled and subjected to an established respiratory physiotherapy protocol. Ventilatory variables (dynamic lung compliance, respiratory system resistance, tidal volume, peak inspiratory pressure, respiratory rate, and oxygen saturation) and hemodynamic variables (heart rate) were measured one hour before (T-1), immediately after (T0) and one hour after (T+1) applying the respiratory physiotherapy protocol. Results: During the period of data collection, 104 patients were included in the study. Regarding the ventilatory variables, an increase in dynamic lung compliance (T-1 = 52.3 ± 16.1mL/cmH2O versus T0 = 65.1 ± 19.1mL/cmH2O; p < 0.001), tidal volume (T-1 = 550 ± 134mL versus T0 = 698 ± 155mL; p < 0.001), and peripheral oxygen saturation (T-1 = 96.5 ± 2.29% versus T0 = 98.2 ± 1.62%; p < 0.001) were observed, in addition to a reduction of respiratory system resistance (T-1 = 14.2 ± 4.63cmH2O/L/s versus T0 = 11.0 ± 3.43cmH2O/L/s; p < 0.001), after applying the respiratory physiotherapy protocol. All changes were present in the assessment performed one hour (T+1) after the application of the respiratory physiotherapy protocol. Regarding the hemodynamic variables, an immediate increase in the heart rate after application of the protocol was observed, but that increase was not maintained (T-1 = 88.9 ± 18.7 bpm versus T0 = 93.7 ± 19.2bpm versus T+1 = 88.5 ± 17.1bpm; p < 0.001). Conclusion: Respiratory therapy leads to immediate changes in the lung mechanics and hemodynamics of mechanical ventilation-dependent patients, and ventilatory changes ...

Estratégias de circulação extracorpórea na Síndrome do Desconforto Respiratório Agudo: uma realidade? / Strategies for extracorporeal gas exchange support in the Acute Respiratory Distress Syndrome: a reality?

A síndrome do desconforto respiratório agudo (SDRA) resulta em grande área de colapso pulmonar, e apresenta-se morfologicamente como um pulmão de bebê ou baby lung. Apesar da utilização de estratégias ventilatórias consideradas protetoras, essas não são suficientes para proporcionar proteção em alguns pacientes mais graves, que têm indicação de se implementar outras técnicas alternativas ou de resgate para que se preserve a estrutura morfofuncional pulmonar. As técnicas de assistência pulmonar extracorpórea (APE) sustentam a troca gasosa adequada, seja através de oxigenação e controle da hipercapnia (oxigenação por membrana extracorpórea - ECMO), ou apenas pelo controle da hipercapnia (remoção de dióxido de carbono extracórporeo em circuito modificado de hemodiálise - ECCO2 R, ou através da assistência pulmonar intervencionista – iLA), o que auxilia no ajuste ventilatório para promoção da proteção pulmonar adequada. Entretanto, são técnicas invasivas que podem impor considerável risco ao paciente, e por isso, deverão ser usadas em centros com experiência em sua utilização. Nessa revisão, serão discutidos os princípios fisiológicos da troca e transporte de gases, assim como as principais técnicas de APE: ECMO, ECCO2R e iLA, onde serão descritas suas indicações, características funcionais, contraindicações e resultados experimentais e clínicos mais relevantes...

The acute respiratory distress syndrome (ARDS) results in considerable area of pulmonary colapse and may be morphologically considered as a baby lung. Despite of the use of protective ventilatory strategies, in some very critically ill patients those strategies are not enough to protect the lungs. At this point alternative or rescue therapies are indicated to preserve the morphofunctional structure of the lungs.The extracorporeal pulmonary assistance (APE) techniques support adequate gas exchange by oxigenation and hypercapnia control (extracorporeal membrane oxygenation – ECMO), or just by hypercapnia control (extracorporeal carbon dioxide removal using a modified hemodyalisis circuit - ECCO2R, or by interventional lung assist - iLA) which allow to set ventilatory parameters to adequately protect the lungs. However these techniques are invasive and may impose considerable risks to the patient and that is why it must be used in refferal hospital centers. In this review will be discussed physiological principles of gas exchange and transport, as well as the main EPA techniques: ECMO, ECCO2R and iLA. Indications, functional characteristics, contraindications and relevant experimental and clinical results...

Entendendo melhor a insuficiência respiratória aguda / A better understanding of acute respiratory failure

A insuficiência respiratória aguda (IRpA) é uma síndrome potencialmente grave, constituindo uma das principais indicações de internação em unidades de terapia intensiva. Embora diferentes condições clínicas possam evoluir com IRpA, todas apresentarão comprometimento nas trocas gasosas que caracterizarão a síndrome.O conhecimento da fisiologia das trocas gasosas e os mecanismos pelos quais elas podem ser alteradas permite compreender a fisiopatologia da IRpA e as repercussões dos diferentes distúrbios sobre os gases arteriais. Este conhecimento permite a interpretação adequada da gasometria arterial e de indicadores derivados da mesma, facilitando a condução dos pacientes com IRpA, tanto em relação ao diagnóstico etiológico, quanto ao tratamento de suporte.Estes conceitos da fisiologia das troas gasosas e da fisiopatologia da IRpA e suas aplicações clínicas serão revisados neste artigo...

Acute respiratory failure (ARF) is a potentially severe syndrome, which is a common indication for admission to an intensive care unit. Although the ARF can be caused by different clinical conditions, all of them will present gas exchange impairments that will characterize the syndrome.By knowing the gas exchanges physiology and the mechanisms by which they can be impaired, one can understand the physiopathology of the ARF and how it can compromise the arterial gases. This knowledge allows the correct interpretation of arterial blood gases and other useful indicators, such as the alveolar-arterial oxygen gradient, which help us to manage patients with ARF, both in their diagnosis, and in their supportive treatment.These concepts about the gas exchange physiology and the ARF physiopathology, and their clinical relevance, will be discussed in this article...

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve ( % V ˙ O 2  R ) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and V ˙ O 2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg-1·min-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and % V ˙ O 2  R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and % V ˙ O 2  R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise.

Experiencia clínica con el bloqueador bronquial de ARNDT en pacientes pediátricos / Clinical experience with Arndt bronchial blocker in pediatric patients

Describir la experiencia con el bloqueador bronquial de Arndt (BBA) y determinar los efectos de la ventilación monopulmonar (VMP) en el intercambio gaseoso en pacientes pediátricos. Método: El BBA se utilizó en 11 pacientes que requirieron VMP. Cuando el diámetro del tubo traqueal impedía el uso del BBA como originalmente estaba descrito, éste fue colocado en la tráquea previo a la intubación traqueal quedando por fuera del tubo traqueal. El BBA fue posicionado con ayuda de un fibrobroncoscopio introducido a través del adaptador del bloqueador. Se estandarizaron la modalidad deventilación y las maniobras destinadas a restablecer la oxigenación en caso de desaturación. Se controlaron gases arteriales, presión de vía aérea y CO2 de fin de espiración (EtCO2) ventilando ambos pulmones y en VMP. Resultados: El BBA fue correctamente posicionado en todos los pacientes, obteniéndose un pulmón desinflado en todos ellos. La relación pO2 /FiO2 promedio en decúbito lateral ventilando ambos pulmones y en VMP fue 287 (rango 100-424) y 199 (rango 62-332), p = 0,0108. La diferencia pCO2-EtCO2 mostró un comportamiento variable, aumentando en algunos e incluso haciéndose negativa en otros. Conclusión: El BBA permitió realizar VMP en todos los pacientes. La relación paO2/FiO2 disminuyó en todos los pacientes pero la saturación arterial de oxígeno pudo ser mantenida en niveles seguros. La capnografía mostró ser un indicador poco confiable de la efectividad de la ventilación durante VMP...

Single lung ventilation (SLV) and knowledge of its effects in pediatric patients has been limited by the lack of suitable double lumen tubes (DLT). The bronchial blocker (BB) described by Arndt allows SLV without a DLT, even in small children. Objective: Describe the experience with the Arndt’s BB, and the effects of SLV on gas exchange in children. Design: Observational study. Setting and patients: Eleven children requiring SLV using a BB were studied at a University Hospital. Interventions: A BB was used for SLV. When the internal diameter of the ET didn’t allow the use of the BB as originally described, it was inserted into the trachea before tracheal intubation, leaving the BB next to the ET. A FOB inserted through the multi-portal adapter of the BB guided it to the desired position. Ventilatory pattern and maneuvers to restore arterial oxygen saturation (SatO2) were standardized. Main outcome measures: Arterial blood gases, airway pressure, and EtCO2 were obtained in lateral decubitus position while both lungs were ventilated and during SLV. Results: Ages were between seven months and four years. In 10 patients, the BB was inserted alongside the tracheal tube. In all cases the lung was quiet and deflated. In 2 patients, surgical manipulation dislodged the BB. In one it could not be replaced and thoracotomy was required. Arterial pO2decreased in all patients, but SatO2was maintained above 90%. No significant changes in pCO2 and airway pressure were observed, and pCO2 -EtCO2 relationship was unpredictable. Conclusion: Arndt’s BB allowed SLV in all patients. Even though arterial pO2 decreased in all children, SatO2 could be maintained at an acceptable level...

Análise comparativa entre a manobra de recrutamento alveolar e a técnica de breath stacking em pacientes com lesão pulmonar aguda / Comparative analysis between the alveolar recruitment maneuver and breath stacking technique in patients with acute lung injury

Objetivo: Comparar a eficácia da manobra de recrutamento alveolar e a técnica de breath stacking, na mecânica pulmonar e na troca gasosa, em pacientes com lesão pulmonar aguda. Métodos: Trinta pacientes foram distribuídos em dois grupos: Grupo 1 - breath stacking e Grupo 2 - manobra de recrutamento alveolar. Após receberem atendimento de fisioterapia convencional, todos os pacientes receberam ambos os tratamentos, com intervalo de 1 dia entre eles. No primeiro grupo foi aplicada primeiramente a técnica de breath stacking e, posteriormente, a manobra de recrutamento alveolar. Já os pacientes do segundo Grupo 2 foram submetidos inicialmente ao recrutamento alveolar e, após, a técnica de breath stacking. Foram avaliadas as medidas de complacência pulmonar e de resistência de vias aéreas antes e após a aplicação de ambas as técnicas. Foram coletadas gasometrias arteriais pré e pós-técnicas para avaliar a oxigenação e a troca gasosa. Resultados: Ambos os grupos apresentaram aumento significativo da complacência estática após breath stacking (p=0,021) e recrutamento alveolar (p=0,03), mas não houve diferença entre eles (p=0,95). A complacência dinâmica não aumentou para os grupos breath stacking (p=0,22) e recrutamento alveolar (p=0,074), sem diferença entre os grupos (p=0,11). A resistência de vias aéreas não diminuiu para ambos os grupos: breath stacking (p=0,91) e recrutamento alveolar (0,82), sem diferença entre os grupos p=0,39. A pressão parcial de oxigênio aumentou significantemente após breath stacking (p=0,013) e recrutamento alveolar (p=0,04); mas entre os grupos não houve diferença (p=0,073). A diferença alvéolo arterial de O2 diminuiu para ambos os grupos após intervenções breath stacking (p=0,025) ...

Objective: To compare the effectiveness of the alveolar recruitment maneuver and the breath stacking technique with respect to lung mechanics and gas exchange in patients with acute lung injury. Methods: Thirty patients were distributed into two groups: Group 1 - breath stacking; and Group 2 - alveolar recruitment maneuver. After undergoing conventional physical therapy, all patients received both treatments with an interval of 1 day between them. In the first group, the breath stacking technique was used initially, and subsequently, the alveolar recruitment maneuver was applied. Group 2 patients were initially subjected to alveolar recruitment, followed by the breath stacking technique. Measurements of lung compliance and airway resistance were evaluated before and after the use of both techniques. Gas analyses were collected before and after the techniques were used to evaluate oxygenation and gas exchange. Results: Both groups had a significant increase in static compliance after breath stacking (p=0.021) and alveolar recruitment (p=0.03), but with no significant differences between the groups (p=0.95). The dynamic compliance did not increase for the breath stacking (p=0.22) and alveolar recruitment (p=0.074) groups, with no significant difference between the groups (p=0.11). The airway resistance did not decrease for either groups, i.e., breath stacking (p=0.91) and alveolar recruitment (p=0.82), with no significant difference between the groups (p=0.39). The partial pressure of oxygen increased significantly after breath stacking (p=0.013) and alveolar recruitment (p=0.04), but there was no significant difference between the groups (p=0.073). The alveolar-arterial O2 difference decreased for both groups after the breath stacking (p=0.025) and alveolar recruitment (p=0.03) interventions, and there was no significant difference between the groups (p=0.81). Conclusion: Our data suggest that the breath stacking and alveolar ...

Efeitos da ventilação mecânica não invasiva sobre a modulação autonômica cardíaca / Effects of noninvasive ventilation on cardiac autonomic modulation

Esta revisão tem por objetivo reunir estudos atuais que abordaram os efeitos da aplicação de diferentes modalidades de ventilação não invasiva (VNI) sobre o sistema nervoso autônomo, avaliados por meio da variabilidade da frequência cardíaca (VFC). A busca dos artigos foi realizada nas bases de dados PubMed, PEDro, SciELO e Lilacs, por meio dos descritores: noninvasive ventilation, CPAP ventilation, intermittent positive pressure breathing em cruzamento com o descritor autonomic nervous system, no período de 2008 a 2012. Após a eliminação dos artigos que não versavam sobre o tema, foram selecionados seis estudos, dos quais, cinco aplicaram VNI pela modalidade de CPAP e um a modalidade de pressão positiva em dois níveis nas vias aéreas. Os achados sugerem que a VNI promove modificações na modulação autonômica que são dependentes das condições dos sujeitos analisados e do momento de avaliação desses índices, ou seja, efeito agudo ou em longo prazo.

This review is intended to gather together recent studies that explore the effects of different types of noninvasive ventilation (NIV) on the autonomic nervous system, assessed through heart rate variability (HRV). A search for papers was conducted in the PubMed, PEDro, SciELO and Lilacs databases with the following descriptors: noninvasive ventilation, CPAP ventilation, intermittent positive pressure breathing and autonomic nervous system, for the period between 2008 and 2012. After eliminating papers not addressing the topic, we selected six studies, of which five applied NIV in CPAP mode and one used biphasic positive airway pressure. In general, the findings suggest that NIV promotes changes in autonomic modulation that are dependent on the conditions of the subjects analyzed and the time when these rates are assessed, meaning acute or long-term effects.

Ventilação não invasiva após cirurgia cardiovascular: um ensaio clínico randomizado / Non-invasive ventilation after cardiovascular surgery: a randomized clinical trial

Fundamentos: A hipoxemia é a complicação mais comum no pós-operatório (PO) de cirurgia cardíaca, sendo consequência principalmente da formação de atelectasias, edema intersticial alveolar e acúmulo de secreção pulmonar. Essas alterações aumentam a incidência de infecções pulmonares, tempo de internação na UTI e custos hospitalares. Objetivo: Avaliar as trocas gasosas e alterações hemodinâmicas de pacientes hipoxêmicos submetidos à ventilação não invasiva (VNI) no PO imediato de cirurgia cardiovascular. Métodos: Ensaio clínico randomizado conduzido na UTI cirúrgica de um hospital cardiológico. Foram incluídos pacientes com hipoxemia (300>PaO2/FiO2>150) uma hora após extubação orotraqueal, no PO imediato de cirurgia cardiovascular eletiva e que foram submetidos à cateterização da artéria pulmonar no bloco cirúrgico (BC). O grupo-controle recebeu oxigenoterapia e o grupo-intervenção, VNI e oxigênio durante três horas consecutivas. Na análise estatística foram utilizados os testes t de Student, Mann-Whitney, exato de Fisher, ANOVA e generalized estimating equation (GEE). Resultados: Estudados 42 pacientes. Os pacientes do grupo-intervenção (n=21) apresentaram melhora significativa da relação PaO2/FiO2 (p=0,007). Houve discreta diferença entre os grupos na pressão capilar pulmonar (p=0,012), no índice cardíaco (p=0,006) e na pressão venosa central (p=0,022).

Background: Hypoxemia is the most common complication during the post-operative stage of cardiovascular surgery, due mainly to atelectasis, alveolar interstitial edema and accumulations of pulmonary secretions. These changes may increase the incidence of lung infections with longer ICU stays and consequently higher hospital costs. Objective: To evaluate gas exchanges and hemodynamic alterations in hypoxemic patients under non-invasive ventilation (NIV) during the immediate post-operative period subsequent to cardiovascular surgery. Methods: A randomized clinical trial conducted in the surgical ICU of a cardiology hospital of patients with hypoxemia (300>PaO2/FiO2>150) one hour after orotracheal extubation during the post-operative period immediately after elective cardiovascular surgery who underwent pulmonary artery catheterization in the surgical ward. The control group received oxygen therapy, while the intervention group received NIV plus oxygen for three consecutive hours. For the statistical analysis, we used the Student t, Mann-Whitney, Fisher’s exact tests, as well as ANOVA and generalized estimating equations (GEE). Results: Among the 42 patients studied, the intervention group (n=21) presented significant improvements in the PaO2/FiO2 ratio (p=0.007), with little difference between the groups for pulmonary capillary pressure (p=0.012), cardiac index (p=0.006) and central venous pressure (p=0.022).

Comparison of Celsior and Perfadex lung preservation solutions in rat lungs subjected to 6 and 12 hours of ischemia using an ex-vivo lung perfusion system

OBJECTIVE: This study evaluated the performance of lungs that were preserved with different solutions (Celsior, Perfadex or saline) in an ex vivo rat lung perfusion system. METHODS: Sixty Wistar rats were anesthetized, anticoagulated and randomized into three groups (n = 20). The rats were subjected to antegrade perfusion via the pulmonary artery with Perfadex, Celsior, or saline, followed by 6 or 12 hours of ischemia (4ºC, n = 10 in each group). Respiratory mechanics, gas exchange and hemodynamics were measured at 10-minute intervals during the reperfusion of heart-lung blocks in an ex vivo system (IL2-Isolated Perfused Rat or Guinea Pig Lung System, Harvard Apparatus, Holliston, Massachusetts, USA; Hugo Sachs Elektronik, Germany) for 60 minutes. The lungs were prepared for histopathology and evaluated for edema following reperfusion. Group comparisons were performed using ANOVA and the Kruskal-Wallis test with a 5% level of significance. RESULTS: Gas exchange was not significantly different between lungs perfused with either Perfadex or Celsior at the same ischemic times, but it was very low in lungs that were preserved with saline. Airway resistance was greater in the lungs that were preserved for 12 hours. Celsior lungs that were preserved for 6 and 12 hours exhibited lower airway resistance (p = 0.01) compared to Perfadex lungs. Pulmonary artery pressure was not different between the groups, and no significant differences in histopathology and apoptosis were observed between the groups. CONCLUSIONS: Lungs that were preserved with Celsior or Perfadex exhibited similar gas exchange and histopathological findings. Airway resistance was slightly lower in the Celsior-preserved lungs compared with the Perfadex-preserved lungs.