Effects of Alveolar Recruitment and Positive End-Expiratory Pressure on Oxygenation during One-Lung Ventilation in the Supine Position

PURPOSE: Hypoxemia during one-lung ventilation (OLV) remains a serious problem, particularly in the supine position. We investigated the effects of alveolar recruitment (AR) and positive end-expiratory pressure (PEEP) on oxygenation during OLV in the supine position. MATERIALS AND METHODS: Ninety-nine patients were randomly allocated to one of the following three groups: a control group (ventilation with a tidal volume of 8 mL/kg), a PEEP group (the same ventilatory pattern with a PEEP of 8 cm H2O), or an AR group (an AR maneuver immediately before OLV followed by a PEEP of 8 cm H2O). The tidal volume was reduced to 6 mL/kg during OLV in all groups. Blood gas analyses, respiratory variables, and hemodynamic variables were recorded 15 min into TLV (TLVbaseline), 15 and 30 min after OLV (OLV15 and OLV30), and 10 min after re-establishing TLV (TLVend). RESULTS: Ultimately, 92 patients were analyzed. In the AR group, the arterial oxygen tension was higher at TLVend, and the physiologic dead space was lower at OLV15 and TLVend than in the control group. The mean airway pressure and dynamic lung compliance were higher in the PEEP and AR groups than in the control group at OLV15, OLV30, and TLVend. No significant differences in hemodynamic variables were found among the three groups throughout the study period. CONCLUSION: Recruitment of both lungs with subsequent PEEP before OLV improved arterial oxygenation and ventilatory efficiency during video-assisted thoracic surgery requiring OLV in the supine position.

Importancia de la corrección de la KCO informada computarizada en pacientes con volumen alveolar disminuído / Importance to adjust computerized informed KCO in patients with low alveolar volume

La disminución del factor de transferencia de monóxido de carbono (TLCO) y del Volumen Alveolar (VA) no es uniforme. Los informes de los equipos computadorizados entregan un valor de KCO que no toma en cuenta este detalle.Objetivo: Realizar el cálculo de KCO a través de la corrección de Stam (J Apply Physiol 1994) y compararlas con las informadas por el software de un equipo de laboratorio pulmonar computadorizado reconocido (Collins).Material y Método: Fueron incluídos pacientes consecutivos derivados al Laboratorio Pulmonar de la Unidad para realizar una prueba de TLCO por enfermedad intersticial pulmonar entre Enero y Junio de 2008. Se realizaron las pruebas según recomendacionesATS/ERS por el método de respiración única y con el método de toma de muestra de Ogilvie. Se analizó la KCO según lo informa el software del equipo Collins Plus/SQL System (1995Warren Collins), y luego se lo recalculó corregida según el cálculo de Stam (J Apply Physiol 1994). Se incluyó en este análisis si tenían <80% del volumen alveolar predicho. Resultados: Fueron evaluados 15 pacientes (media edad: 57.5 ± 12.9 años, sexo femenino 66.7%) con enfermedad intersticial.La media de VA fue 3.5±0.8 L(64.3±11.6%). La media de KCO informada a través del software fue 4.2± 1.3ml/min/mmHg/L. La media de KCO corregida fue 3.7 ± 1.2ml/min/mmHg/L (Δ 11.8±3.8, rango: 6.8%-21.1%). Se observó una relación lineal y negativa entre el %VA y el delta de KCO corregida/informada (r2= -0.99). La elección de diferentes tablas de valores normales de VA altera hasta 12% el valor de la misma, pero la KCO corregida se altera en grado mínimo (3%). Conclusiones: Cuando el VA está disminuído, se debe realizar la corrección del informe computadorizado de la KCO, porque se observa una diferencia promedio del 12%, sobreestimando la real KCO del paciente. Otros factores, como la tabla de valores predictivos de VA, influencia muy poco la corrección de KCO.

The decrease of the Transfer Factor of the Lung for Carbon Monoxide (TLCO) and the Alveolar Volume (VA) is not uniform. Software of lung computed machine informs the carbon monoxide transfer coefficient TLCO/VA (KCO) by calculating the ratio without adjusting for that assumption. Objectives: To calculate KCO using a correction by the Stam´s equation (J Apply Physiol1994), to compare the corrected KCO with the result informed by the software of Collins lung laboratory equipment, and to evaluate the impact of using different predictive tables of VA in the estimates of KCO. Materials: Consecutive patients with intersticial lung disease who attended the LungLaboratory to perform the TLCO between January and June 2008 were included in the study. TLCO was performed according to ATS/ERS recommendations by the single-breathand Ogilvie methods. KCO was calculated by the software of Collins Plus/SQL System (1995 Warren Collins), and then recalculated by Stam´s equation. Only patients withless than 80% of VA predictive value were included. Results: 15 patients with interstitial lung disease were evaluated (age: 57.53 ± 12.93 years old, female: 66.66%). The mean VA was 3.55 ±0.83 L (64.33 ±11.56%) and the mean KCO informed by software was 4.17 ±1.31 ml/min/mmHg/L. The corrected KCO was 3.76 ±1.33 ml/min/mmHg/L(Δ 11.84 ±3.84, range: 6.82%-21.1%). It was observed a negative and lineal relation between %VA and Δ KCO corrected/informed (R2= -0.99). The election of different tables of VA normal values distorts up to12% the individualvalues, but the corrected KCO is little modified (3%). Conclusion: When the VA is reduced, the correction of the KCO must be performed, to avoid on average a 12% overestimate. Other factors such as the election of VA predictive tables have little influence on the KCO correction.

The effects of positive end-expiratory pressure in alveolar recruitment during mechanical ventilation in pigs / Os efeitos da pressão positiva expiratória final no recrutamento alveolar durante a ventilação mecânica em porcos

PURPOSE: To evaluate the effects of alveolar recruitment based on mean airway pressure (MAP) on pig lungs submitted to thoracotomy through blood gas exchange and hemodynamic parameters. METHODS: Twelve pigs weighting approximately 25Kg were intubated and ventilated on volume controlled ventilation (tidal volume 10ml/Kg, respiratory rate 16min, FiO2 1.0, inspiratory:expiratory ratio 1:2, PEEP 5cmH2O). The animals were then randomized into two groups: control and left lateral thoracotomy. The PEEP was increased at each 15-minute intervals to reach a MAP of 15, 20 and 25cmH2O, respectively. Hemodynamic, gas exchange and respiratory mechanic data were measured immediately before each PEEP change. RESULTS: There were no significant differences between both groups in all parameters analyzed (P=1.0). The PaO2, PaCO2, MAP, PAP and plateau pressure were significantly worse at MAP of 25cmH2O, when compared with the other values of MAP (P=0.001, P=0.039, P=0.001, P=0.016 e P=0.027, respectively). The best pulmonary performance according to the analyzed parameters was observed at MAP of 20cmH2O. CONCLUSION: PEEP adjusted to MAP of 20cmH2O resulted in best arterial oxygenation, without compromising the venous return, as opposed to MAP of 25cmH2O, which caused deterioration of gas exchange, hemodynamics and respiratory mechanic.

OBJETIVO: Avaliar os efeitos do recrutamento alveolar baseado na pressão média das vias aéreas (Pmédia) sobre os pulmões de porcos submetidos a toracotomia, através de dados gasométricos e hemodinâmicos. MÉTODOS: Doze porcos machos pesando em média 25Kg receberam indução anestésica, sendo intubados e ventilados a volume (FiO2=1.0, volume corrente=10 ml/kg/min, FR=16 cpm, relação I:E=1:2 e PEEP 5 mmHg). Os animais foram randomizados em dois grupos: controle e toracotomia lateral esquerda. Os valores de PEEP em cada grupo foram aumentados a cada 15 minutos para atingir valores de Pmédia de 15, 20 e 25cmH2O, sendo coletados dados hemodinâmicos, gasometria arterial e mecânica respiratória imediatamente antes de cada acréscimo do PEEP. RESULTADOS: Não houve diferença estatisticamente significativa entre os 2 grupos em todos os parâmetros analisados (P=1,0). Ocorreu piora significativa da PaO2, PaCO2, pressão arterial média, pressão da artéria pulmonar e pressão de platô com Pmédia de 25cmH2O comparado com os demais valores de Pmédia (P=0.001, P=0.039, P=0.001, P=0.016 e P=0.027, respectivamente). O melhor desempenho pulmonar pelos parâmetros analisados ocorreu com a Pmédia de 20cmH2O. CONCLUSÃO: As manobras de recrutamento alveolar alteram o desempenho pulmonar e função hemodinâmica independemente da cavidade torácica estar aberta ou fechada. O PEEP ideal para o recrutamento alveolar independente dos grupos estudados foi obtido a uma Pmédia de 20cmH2O em relação a todos os parâmetros analisados.

Asociación molecular y función del agente tensioactivo pulmonar de ternera / Molecular association and function of calf lung surfactant

El agente tensioactivo pulmonar es un material compuesto de fosfolípidos, lípidos neutros y proteínas que se encuentra en la superficie alveolar de los pulmones y facilita la ventilación alveolar. La organización molecular de los componentes del agente tensioactivo aislado de pulmones de ternera fue analizada por calorimetría diferencial de barrido y por dispersión dinámica de luz y posteriormente comparada con los componentes organizados en liposomas uni y multilamelares; además, se probó la actividad de superficie al desarrollar en cobayos el síndrome de dificultad respiratoria. Los estudios de calorimetría mostraron que las interacciones lípido-proteína fueron considerablemente abatidas en el agente tensioactivo nativo, en comparación con las del agente tensioactivo en forma de liposomas uni o multilamelares. Los experimentos de dispersión dinámica de luz indicaron que el agente tensioactivo nativo tiene forma fibrilar con interacciones limitadas entre lípidos y proteínas, lo que sugiere que se encuentra organizado en una estructura en forma de reja formando una película de estructura estable. Los resultados obtenidos resaltan la importancia de la organización molecular del agente tensioactivo. Cuando éste fue usado para tratar a los animales con síndrome de dificultad respiratoria, los valores del pH arterial y de PaCO2 mejoraron casi hasta alcanzar los valores normales; cuando se utilizó el agente tensioactivo reconstituído como liposomas uni o multilamelares, los animales no se recuperaron. Es importante enfatizar que el método seguido en el protocolo de aislamiento del agente tensioactivo pulmonar de ternera permitió obtenerlo en una forma fisiológicamente activa.

Surfactant, a highly surface-active material composed of phospholipids, neutral lipids and proteins, lines the lungs' alveolar surface facilitating alveolar ventilation. The molecular organization of surfactant components isolated from calf-lungs was analyzed by differential-scanning calorimetry and dynamic light-scattering, and subsequently compared to surfactant components organized in uni and multilamellar liposomes. The respiratory distress syndrome developed in adult guinea pigs was used for assessing surfactant activity. Calorimetry studies showed that lipid-protein interactions were considerably abated in native surfactant as compared to those of surfactant in uni or multi-lamellar liposomes. Light-scattering experiments indicated that native surfactant has a fibrillar shape with limited lipid-protein interactions, suggesting that it is organized in a lattice-like structure forming a stable film. These findings underscore the importance of the native molecular organization of surfactant. When surfactant reconstituted as uni- or multilamellar liposomes was administred to animals under respiratory distress, they did not recover. In contrast, when native surfactant was used to treat sick animals, arterial pH and PaCO2 values improved, almost reaching normal values. It is important to emphasize that fewer steps in the protocol for isolation of calf lung surfactant made it possible to obtain it in a physiologically active molecular form.

Interdependencia pulmonar I: fisiología del llene alveolar / Pulmonary interdependence I: physiology of the alveolar filling

En el presente trabajo se analizan factores que definen la distribución de los flujos aéreos inspiratorios. Se examinan las variables más significativas que condicionan la fase de llene alveolar durante la respiración en sujetos sanos y enfermos. De ellas, la fuerza de gravedad y el patrón de contracción de la musculatura respiratoria son considerados de mayor relevancia. De acuerdo a la literatura se repara en la existencia del patrón inverso entre adultos y niños para el comportamiento V/Q en posición decúbito lateral. Se profundiza sobre la existencia de zonas con diferentes secuencias de llene a través de la teoría de la constante de tiempo. Se realiza un análisis para proyectar estas bases fisiológicas a las acciones de la kinesiología respiratoria que actúan sobre la mecánica de la respiración

Proteínas pulmonares asociadas a sustancias con actividad surfactante7 / Pulmonary proteins associated to substances with surfactant activity

La ausencia de surfactantes pulmonares trae como consecuencia el incremento de la tensión superficial a lo largo del epitelio alveolar, provocando un colapso alveolar y la lisis de las células epiteliales. Este proceso culmina con la aparición de un síndrome de insuficiencia respiratoria, que es la causa principal de morbimortalidad en niños prematuros. Recientemente, la aplicación de mezclas de agentes surfactantes con fines terapéuticos ha constituido un gran apoyo para la terapia respiratoria, ya que permite una evolución más rápida de los niños que padecen este síndrome. Por todo esto, resulta de gran importancia el conocimiento más detallado de la función, el metabolismo y la regulación de la expresión genética de las proteíinas surfactantes, para el diseño de nuevas y mejores estrategias terapéuticas para combatir este síndrome

Efeitos da poluiçäo, tabagismo e poeiras minerais sobre o aparelho respiratório / Effects of pollution, smoking and mineral dusts on respiratory system

Doenças pulmonares intersticiais difusas e doenças crônicas das vias aéreas podem ser causadas por poeiras minerais, poluiçäo e fumo e säo discutidas neste trabalho. Doenças pulmonares ocupacionais e ambientais constituem assunto amplo e complexo, impossível de ser abordado em sua íntegra em um simples trabalho, de modo que daremos destaque a conceitos básicos envolvendo mecanismos de defesa pulmonar e um pouco da experiência prática na rotina diagnóstica. Nos pulmöes, doenças intersticiais ocupacionais säo o resultado final da composiçäo de lesöes focais. Esses sítios de lesöes focais traduzem a resposta do tecido pulmonar alveolado e condutor ao fumo, particulas ou minerais. Com a injúria pulmonar crescente e repetitiva, inflamaçäo e fibrose determinam distorçäo e remodelaçäo pulmonar, finalmente conduzindo a alteraçöes da fisiologia respiratória. Nos alvéolos, o macrófago pulmonar parece ter um papel central no desenrolar desses eventos, agindo tanto como fagócito incorporador de particulas quanto como mediador liberador de poderosas substâncias biológicas modificadoras da funçäo de outras células, como neutrófilos e fibroblastos

Efeito da hiperdistensäo alveolar no surfactante pulmonar de ratos submetidos a restriçäo alimentar / Effect of alveolar hyperdistension on lung surfactant of starved rats

O objetivo deste trabalho é observar se as alteraçöes dos parâmetros de ventilaçäo, basicamente volume corrente, contribuem para a modificaçäo do surfactante pulmonar em situaçöes de restriçäo alimentar. Para tanto, foram utilizados ratos adultos Wistar, submetidos a quantidades diferentes da mesma dieta alimentar e a dois padröes de ventilaçäo mecânic, de forma que se trabalhou com quatro grupos experimentais: grupo NN (n=26) - ratos recebendo dieta total e submetidos a ventilaçäo mecânica convencional, intercalada por duas fases de hiperdistensäo alveolar, em que o volume foi duplicado e a frequência respiratória reduzida à metade; grupo RN (n=24) - ratos em restriçäo alimentar, durante sete dias, e submetidos a ventilaçäo mecânica convencional; grupo RH (n=21) - ratos em restriçäo alimentar e submetidos a ventilaçäo mecânica com hiperdistensäo alveolar. Procurou-se detectar alteraçöes na quantidade e qualidade do surfactante pulmonar, observando-se as trocas gasosas pulmonares, a curva pressäo-volume com insuflaçäo de ar e líquido, a quantidade de fosfolipídios totais recuperados na lavagem pulmonar e o estudo anatomapatológico dos pulmöes. Como näo foi evidenciada nenhuma alteraçäo significante ao se compararem os quatro grupos de animais em relaçäo aos diversos parâmetros coletados e analisados, concluiu-se que a hiperdistensäo alveolar pelo período de tempo instituído e a restriçäo alimentar nos moldes estabelecidos näo levaram a alteraçäo, nem na quantidade nem na qualidade, do surfactante pulmonar

On the contribution of height to predict lung volumes, capacities and diffusion in healthy school children of 10-17 years.

Lung volumes, capacities, diffusion and alveolar volumes with physical characteristics (age, height and weight) were recorded for 186 healthy school children (96 boys and 90 girls) of 10-17 years age group. The objective was to study the relative importance of physical characteristics as regressor variables in regression models to estimate lung functions. We observed that height is best correlated with all the lung functions. Inclusion of all physical characteristics in the models have little gain compared to the ones having just height as regressor variable. We also find that exponential models were not only statistically valid but fared better compared to the linear ones. We conclude that lung functions covary with height and other physical characteristics but do not depend upon them. The rate of increase in the functions depend upon initial lung functions. Further, we propose models and provide ready reckoners to give estimates of lung functions with 95 per cent confidence limits based on heights from 125 to 170 cm for the age group of 10 to 17 years.

Effect of routine fiberoptic bronchoscopy and bronchoalveolar lavage on arterial blood gases.

Effect of conventional fiberoptic bronchoscopy (FOB) procedure (Group A, n = 10) and bronchoalveolar lavage (BAL) (Group B, n = 11) on arterial blood gases was studied in 21 patients. A significant fall in arterial oxygen tension (PaO2) with widening of alveolar arterial oxygen gradient D(A-a)O2 was observed during FOB (p < 0.001) and 30 minutes following the procedure (p < 0.001). Bronchoalveolar lavage was also associated with significant fall (p < 0.001) in PaO2 with increased D(A-a)O2 and this fall in PaO2 persisted for 30 minutes after the procedure (p < 0.01). None of the patients received oxygen during the procedures. None of the patients in either group developed bronchospasm. No change in arterial carbon dioxide (PaCO2) was observed in either group. Hypoxaemic encephalopathy developed in one patient in group A, hypotension and cyanosis developed in one patient each in group B. No mortality was encountered in the study. All the three patients with complications were excluded from final analysis. It was concluded from this study that both conventional bronchoscopy and BAL procedures were associated with significant hypoxaemia and supplemental oxygen should be given to all patients during the procedure and should be continued for at least 30 min. afterwards.

Applied aspects of theoretical analysis of pulmonary gas exchange.

This paper gives a summary of the theoretical analysis of the processes of gas exchange in the lungs. It brings out the effect of changes in the rate of equilibration of gases across the membrane due to a variety of factors. It brings out that the length of the capillary over which complete equilibration occurs is infinitesimally small, hence a diffusion defect is seldom a cause of hypoxaemia in disease unless the character of membrane changes like in interstitial fibrosis or pneumoconiosis. The increase in length of capillary for complete equilibrium is significant in hypoxia of high altitude and left ventricular failure causing dilatation of pulmonary capillaries.

Alveolar stability of altitude raised rats.

On the lining of alveolar membrane of the lung presence of surfactant, a surface tension lowering agent which is a phospholipid in nature, is well established. A good correlation exists between pulmonary lecithin, the principle constituent of surfactant system and alveolar stability. The production of surface active material in the type II cells is oxygen dependent and is affected by hypoxia. The chemical and physical nature of the surfactant in the lungs of the rats raised at high altitude has been studied in comparison with that of sea level control. Eighteen male adult rats raised at high altitude (3520 m) were used. Phospholipids (Phosphatidyl Choline, Phosphatidyl ethanolamine, Lysophosphatidyl choline, Lysophosphatidyl ethanolamine and Sphingomyelin) were estimated by thin layer chromatography, stability index by Pattle's bubble technique and dynamic surface tension have also been studied to assess the surfactant activity of the lung. The results indicate that there was a decrease in lung surfactant as measured by chemical analysis. However, stability ratio measurements showed that there was very little change in the stability ratio (Sr) as the value of both groups lay in the normal range namely 0.6 to 0.9 hence the lungs of high altitude raised rats had normal alveolar stability. Surface tension values of alveolar lavage in altitude raised animals were also similar to those of normal rats. It is concluded that the rats raised at altitude show a lowering of surfactant as estimated chemically but the stability ratio is not significantly altered to indicate alveolar instability. In the altitude rats lesser quantum of surfactant is adequate to maintain alveolar stability.