Funciones ejecutivas en pacientes con apnea obstructiva del sueño: explorando el modelo prefrontal / Executive functions in patients with obstructive sleep apnea: exploring the prefrontal model

Introducción El modelo prefrontal propone que los individuos con apnea obstructiva del sueño (AOS) manifiestan conductas similares a un síndrome disejecutivo como resultado de las alteraciones de gases en la sangre y la fragmentación del sueño. Objetivo Comparar las funciones ejecutivas en pacientes con AOS con valores normativos y explorar su relación con las alteraciones de gases en la sangre y la fragmentación del sueño. Pacientes y métodos Se reclutó a pacientes de la comunidad general y de un hospital de tercer nivel. La puntuación obtenida en la evaluación neuropsicológica se contrastó con la t de Student para una muestra. Posteriormente, se estimó un análisis de regresión lineal múltiple mediante parámetros polisomnográficos de hipercapnia, hipoxemia y fragmentación del sueño como variables predictoras, y la puntuación de funciones ejecutivas como variable que se debe predecir. Resultados Pese a que el desempeño en la evaluación neuropsicológica del 26% de esta muestra se clasificó como alteración ejecutiva, los indicadores de fragmentación del sueño y alteraciones de gases no predijeron el desempeño ejecutivo. Conclusión Una fracción de los pacientes con AOS mostró un desempeño similar a un síndrome disejecutivo; no obstante, permanecen indefinidos los factores que subyacen y favorecen este tipo de manifestaciones cognitivas. La atención temprana de este problema de salud pública podría ser la mejor herramienta disponible en aras de mejorar la calidad de vida y prevenir riesgos a la salud. (AU)

INTRODUCTION According to the prefrontal model, individuals with obstructive sleep apnea (OSA) manifest behaviours mimicking dysexecutive syndrome as a result of blood gas abnormalities and sleep fragmentation. OBJECTIVE. To compare executive functions in OSA patients with normative values and explore their relationship with blood gas abnormalities and sleep fragmentation. PATIENTS AND METHODS Patients were recruited from the wider community and from a tertiary care hospital. The score obtained in the neuropsychological assessment was compared with Student’s t-test for a sample. A multiple linear regression analysis was subsequently estimated, using polysomnographic parameters of hypercapnia, hypoxemia and sleep fragmentation as the predictor variables, and the executive function score as the variable to be predicted. RESULTS Although the neuropsychological assessment performance of 26% of this sample was classified as executive impairment, indicators of sleep fragmentation and gas abnormalities failed to predict the performance of executive functions. CONCLUSION. A proportion of the patients with OSA presented performance similar to a dysexecutive syndrome; however, the factors underlying and fostering this type of cognitive manifestation remain unclear. Early treatment for this public health problem could be the best tool available for improving quality of life and preventing health risks. (AU)

Investigação da associação de dois oxigenadores em paralelo ou em série durante o suporte respiratório com oxigenação por membrana extracorpórea / Exploring the association of two oxygenators in parallel or in series during respiratory support using extracorporeal membrane oxygenation

RESUMO Objetivo: Caracterizar as pressões, as resistências, a oxigenação e a eficácia da descarboxilação de dois oxigenadores associados em série ou em paralelo durante o suporte com oxigenação veno-venosa por membrana extracorpórea. Métodos: Usando os resultados de insuficiência respiratória grave em suínos associada à disfunção de múltiplos órgãos, ao modelo de suporte com oxigenação por membrana extracorpórea veno-venosa e à modelagem matemática, exploramos os efeitos na oxigenação, descarboxilação e pressões do circuito de associações de oxigenadores em paralelo e em série. Resultados: Testaram-se cinco animais com peso mediano de 80kg. Ambas as configurações aumentaram a pressão parcial de oxigênio após os oxigenadores. O teor de oxigênio da cânula de retorno também foi ligeiramente maior, mas o efeito na oxigenação sistêmica foi mínimo, usando oxigenadores com alto fluxo nominal (~ 7L/minuto). Ambas as configurações reduziram significativamente a pressão parcial de dióxido de carbono sistêmico. Como o fluxo sanguíneo na oxigenação por membrana extracorpórea aumentou, a resistência do oxigenador diminuiu inicialmente, com aumento posterior, com fluxos sanguíneos mais altos, mas pouco efeito clínico. Conclusão: A associação de oxigenadores em paralelo ou em série durante o suporte com oxigenação veno-venosa por membrana extracorpórea proporciona um modesto aumento na depuração da pressão parcial de dióxido de carbono, com leve melhora na oxigenação. O efeito das associações de oxigenadores nas pressões de circuitos extracorpóreos é mínimo.

ABSTRACT Objective: To characterize the pressures, resistances, oxygenation, and decarboxylation efficacy of two oxygenators associated in series or in parallel during venous-venous extracorporeal membrane oxygenation support. Methods: Using the results of a swine severe respiratory failure associated with multiple organ dysfunction venous-venous extracorporeal membrane oxygenation support model and mathematical modeling, we explored the effects on oxygenation, decarboxylation and circuit pressures of in-parallel and in-series associations of oxygenators. Results: Five animals with a median weight of 80kg were tested. Both configurations increased the oxygen partial pressure after the oxygenators. The return cannula oxygen content was also slightly higher, but the impact on systemic oxygenation was minimal using oxygenators with a high rated flow (~ 7L/minute). Both configurations significantly reduced the systemic carbon dioxide partial pressure. As the extracorporeal membrane oxygenation blood flow increased, the oxygenator resistance decreased initially with a further increase with higher blood flows but with a small clinical impact. Conclusion: Association of oxygenators in parallel or in series during venous-venous extracorporeal membrane oxygenation support provides a modest increase in carbon dioxide partial pressure removal with a slight improvement in oxygenation. The effect of oxygenator associations on extracorporeal circuit pressures is minimal.

Estrategia ventilatoria para el aclaramiento de dióxido de carbono en un lactante con hipercapnia incontrolable / Ventilatory strategy for carbon dioxide clearance in an infant with persistent hypercapnia / Estratégia ventilatória para depuração de dióxido de carbono em uma criança com hipercapnia incontrolável

Resumen Se presenta la experiencia de combinar la ventilación convencional y una técnica modificada de insuflación de gas paratraqueal para evitar complicaciones de la insuflación traqueal directa en un lactante con hipercapnia refractaria, quien ingresó con falla respiratoria aguda secundaria a neumonía multilobar. Al iniciar la ventilación mecánica presentó neumotórax, fístulas broncopleurales y acidemia hipercápnica refractaria a tratamiento convencional. Se inició insuflación de gas paratraqueal en ventilación convencional en modo de presión control, con 10 L/min de aire humidificado con una presión control máxima sostenida de 20 cmH2O. Tres horas después se observó una mejoría de la gasometría arterial y pasadas 72 horas se logró retirar el dispositivo paratraqueal sin complicaciones, con adecuada evolución clínica. Al no incluir un catéter intratraqueal se evitaron complicaciones conservando los mecanismos que mejoran la oxigenación e hipercapnia. La técnica presentada es prometedora; sin embargo, se deben realizar estudios con un mayor número de individuos.

Abstract The experience of combining conventional ventilation and a modified paratracheal gas insufflation technique to avoid complications is presented. An infant with acute respiratory failure secondary to multilobar pneumonia who after start off mechanical ventilation developed pneumothorax, bronchopleural fistulas, and persistent hypercapnic acidemia refractory to conventional ventilatory strategies. It was decided to initiate paratracheal gas insufflation in conventional ventilation in pressure control mode, with 10 L/min of humidified air with a maximum sustained control pressure of 20 cmH2O. Three hours after an improvement in arterial blood gas was recorded and after 72 hours the paratracheal device was removed without complications, with adequate clinical evolution. By not incorporate an intratracheal catheter some complications are avoided, preserving the mechanisms that improve oxygenation and CO2 elimination. Paratracheal gas insufflation is a promising technique, although more studies are required with a greater number of individuals.

Resumo Apresenta-se a experiência de combinar ventilação convencional e técnica modificada de insuflação de gás paratraqueal para evitar complicações da insuflação traqueal direta em uma criança com hipercapnia refratária que foi admitido com insuficiência respiratória aguda secundária a pneumonia multilobar. Ao iniciar ventilação mecânica, apresentou pneumotórax, fístulas broncopleurais e acidemia hipercápnica refratária ao tratamento convencional. A insuflação de gás paratraqueal foi iniciada em ventilação convencional no modo de controle de pressão, com 10 L/min de ar umidificado com pressão de controle máxima sustentada de 20 cmH2O. Três horas após, observou-se melhora da gasometria arterial e após 72 horas o dispositivo paratraqueal foi retirado sem intercorrências, com evolução clínica adequada. Ao não incluir um cateter intratraqueal, as complicações foram evitadas, preservando os mecanismos que melhoram a oxigenação e a hipercapnia. A técnica apresentada é promissora, porém, estudos com um número maior de indivíduos devem ser realizados.

¿Cuándo debería y cuándo no debería utilizarse oxígeno en las enfermedades neuromusculares? / When should and when should not use oxygen in neuromuscular diseases?

Resumen A pesar de las referencias que advierten sobre los efectos adversos de la utilización de O2 suplementario sin asistencia ventilatoria en pacientes con enfermedades neuromusculares (ENM), aún hoy continúan ingresando pacientes en unidades de cuidados intensivos con hipercapnia grave y narcosis por CO2. Parecería que el problema es redescubierto según pasan los años y las generaciones. Muchos pacientes y su red de cuidadores formales e informales no son conscientes de este riesgo que puede llevar a un empeoramiento significativo de los síntomas, eventos agudos, ingresos hospitalarios y, en algunos casos, causar la muerte. Este artículo está centrado en los riesgos de la administración de O2, así como en sus indicaciones puntuales en personas con ENM. El problema central es que la administración de O2 puede quitar el impulso hipóxico para ventilar, aunque otros mecanismos podrían estar involucrados. El retiro completo de la oxigenoterapia sin apoyo de asistencia ventilatoria, es un error aún mayor. Es posible administrar O2 y controlar el CO2 de forma segura. Nunca se debe administrar O2 sin monitorear constantemente el nivel de CO2. La ventilación no invasiva binivelada (BiPAP) mediante interfaz nasal, bucal o boquilla, es la principal medida para revertir la hipoventilación y lograr el descenso de la PaCO2. Las indicaciones de oxigenoterapia en personas con ENM han sido consensuadas y están reservadas a situaciones específicas. Para mejorar la atención de aquellos enfermos con ENM y evitar intervenciones iatrogénicas, se requiere educación al equipo de salud y contención en el entorno del paciente.

Abstract Although the references warn about the adverse effects of adding O2 without ventilatory assistance in patients with neuromuscular diseases (NMD), patients are still to be admitted to intensive care units with severe hypercapnia and CO2 narcosis. It seems that the problem is rediscovered as the years and generations go by. Unfortunately, many patients and their network of formal and informal caregivers are unaware of this risk, leading to significant worsening of symptoms, acute events, hospital admissions, and, in some cases, cause death. This article focuses on the dangers of O2 administration as well as its precise indications in people with NMD. The central problem is that the administration of O2 can remove the hypoxic impulse to ventilate, however, other mechanisms could be involved, but. The complete withdrawal of oxygen therapy is an even greater mistake if it is not supported by ventilatory assistance. It is possible to supply O2 and control CO2 safely. Oxygen should never be administered without constantly monitoring the CO2 level. Bi-level non-invasive ventilation (BiPAP) through a buccal, nasal interface or mouthpiece is the primary measure to reverse hypoventilation and achieve a decrease in PaCO2. The indications for oxygen therapy in people with NMD have been agreed upon and are reserved for specific situations. To improve the care of those with NMD and avoid iatrogenic interventions, education of the health team and support in the patient's environment is required.

Fibrosis quística y alto flujo termo humidificado, una nueva estrategia en el tratamiento / High-flow nasal cannula therapy in cystic fibrosis, a New Treatment Strategy

Se presenta el caso de un paciente con fibrosis quística, insuficiencia respiratoria crónica tipo II, en tratamiento con solución hipertónica, DNAsa, salbutamol, VNI nocturna y oxigenoterapia 24 horas, quien consulta por presentar desaturación y cefalea en el contexto de cambio de equipo de VNI. Se inicia tratamiento con HFNC y AVAPS presentando mejoría clínica, disminución de los requerimientos de oxígeno, descenso de la PaCO2 , disminución de los tapones mucosos en la tomografía y fluidificación de las secreciones respiratorias. Se plantea al HFNC como posible estrategia de tratamiento en los pacientes con FQ. Al prevenir el daño de la mucosa, disminuir la inflamación y las infecciones podría enlentecer el deterioro de la función pulmonar.

We present the case of a patient with cystic fibrosis and type II chronic respiratory failure under treatment with hypertonic solution, DNAse, salbutamol, night NIV and 24-hour oxygen therapy. The patient consults for desaturation and cephalea in the context of changing NIV equipment. The patient begins treatment with HHHF and AVAPS and shows clinical improvement, decrease in oxygen requirements, decrease in PaCO2 , less mucous plugging on the tomography and fluidifying of respiratory secretions. The HHHF is proposed as possible treatment strategy for patients with CF. By preventing damage to the mucosa and reducing inflammation and infections it could slow down impairment of the lung function.

Seizures in patients with respiratory disease - a retrospective single center study / Convulsões em pacientes com doença respiratória - estudo retrospectivo de centro único

ABSTRACT Objective: Seizures are a neurological condition commonly experienced during the follow-up period after systemic or metabolic disorders. The aim of the present study was to determine the etiological factors of seizures in patients at a tertiary care chest clinic. Methods: We reviewed all neurology consultations that were requested due to seizures in inpatient clinics in a tertiary care hospital specializing in respiratory disorders between January 2011 and January 2018 were retrospectively reviewed. Results: The present study included 705 of 2793 (25.2%) patients who requested consultations for seizures during the study period. The mean age of the sample was 64.05±17.19 years. Of the 705 patients, 307 (43.5%) had a previous history of epilepsy (Group I) and 398 (56.5%) had a first-time seizure and were considered to have symptomatic seizures (Group II). Multiple factors played roles in the development of seizures in 54.8% of the patients. In most patients, metabolic causes, systemic infections, and drug use were identified and an intracranial metastatic mass lesion was the major cause in patients with lung cancer. Rates of hypoxemia and respiratory acidosis were significantly higher in patients with symptomatic seizures (Group II) than in patients with primary epilepsy (Group I). Conclusions: Blood gas changes such as hypoxemia and respiratory acidosis were among the factors statistically associated with the development of symptomatic seizures in patients with respiratory diseases. Additionally, hypoxemia, hypercapnia, and respiratory acidosis were correlated with mortality in patients hospitalized for respiratory system diseases who requested consultations for seizures.

RESUMO Objetivo: Convulsões são uma condição neurológica comumente vivenciada durante o período de acompanhamento após distúrbios sistêmicos ou metabólicos. O objetivo do presente estudo foi determinar os fatores etiológicos das convulsões em pacientes de uma clínica torácica de atendimento terciário. Métodos: Foram revisadas retrospectivamente todas as consultas neurológicas solicitadas devido a convulsões em clínicas de internação em um hospital terciário especializado em distúrbios respiratórios entre janeiro de 2011 e janeiro de 2018. Resultados: O presente estudo incluiu 705 dos 2.793 (25,2%) pacientes que solicitaram consultas para convulsões durante o período do estudo. A idade média da amostra foi de 64,05±17,19 anos. Dos 705 pacientes, 307 (43,5%) tinham história prévia de epilepsia (Grupo I) e 398 (56,5%) tiveram uma convulsão inicial e foram considerados como tendo crises sintomáticas (Grupo II). Vários fatores desempenharam papel no desenvolvimento de convulsões em 54,8% dos pacientes. Na maioria dos pacientes, causas metabólicas, infecções sistêmicas e uso de drogas foram identificadas e uma lesão em massa metastática intracraniana foi a principal causa em pacientes com câncer de pulmão. As taxas de hipoxemia e acidose respiratória foram significativamente maiores em pacientes com crises sintomáticas (Grupo II) do que em pacientes com epilepsia primária (Grupo I). Conclusões: Alterações dos gases sanguíneos, como hipoxemia e acidose respiratória, foram alguns dos fatores estatisticamente associados ao desenvolvimento de convulsões sintomáticas em pacientes com doenças respiratórias. Além disso, hipoxemia, hipercapnia e acidose respiratória foram correlacionadas com a mortalidade em pacientes hospitalizados por doenças do sistema respiratório que solicitaram consultas para convulsões.

Insuficiencia de la bomba ventilatoria: una perspectiva histórica / Ventilatory pump failure: historical perspective

En humanos, PaCO2 es controlada muy estrictamente. A diferencia de PaO2 y todas las pruebas funcionales respiratorias que cambian con la edad, PaCO2 permanece constante durante toda la vida. Por lo tanto, su desviación sostenida representa una alteración significativa de la homeostasis. La estructura responsable de mantener la PaCO2 dentro de límites muy estrechos es la bomba ventilatoria. Se compone de varias unidades anatómicas y funcionales que van desde la corteza cerebral hasta los músculos respiratorios. Varias condiciones clínicas que involucran estas estructuras pueden conducir a la insuficiencia de la bomba respiratoria, cuyo sello distintivo es la hipercapnia. La relevancia del concepto de bomba respiratoria ha sido reconocida a lo largo de las décadas. Unos pocos trabajos germinales abrieron la puerta a un notable número de proyectos básicos, aplicados y clínicos en torno a la insuficiencia de la bomba respiratoria y su relevancia clínica. Este artículo revisará algunos de estos estudios y narrará el camino hacia nuestro estado actual de conocimiento sobre el tema.

IIn humans, PaCO2 is very strictly controlled. Unlike PaO2 and all respiratory functional tests that change with age, PaCO2 remains constant throughout life. Therefore, its sustained deviation represents a significant alteration of homeostasis. The structure responsible for keeping PaCO2 within very narrow limits is the ventilatory pump. It consists of several anatomical and functional units that go from the cerebral cortex to the respiratory muscles. Several clinical conditions involving these structures can lead to failure of the respiratory pump, whose hallmark is hypercapnia. The relevance of the respiratory pump concept has been acknowledged for decades. A few initial works allowed for a remarkable number of basic, applied and clinical projects regarding the respiratory pump failure and its clinical relevance. This article reviews some of these studies and describes the process that lead to our current state of knowledge on the subject

Active expiratory oscillator regulates nasofacial and oral motor activities in rats.

NEW FINDINGS: What is the central question of this study? Does the parafacial respiratory group (pFRG), which mediates active expiration, recruit nasofacial and oral motoneurons to coordinate motor activities that engage muscles controlling airways in rats during active expiration. What is the main finding and its importance? Hypercapnia/acidosis or pFRG activation evoked active expiration and stimulated the motoneurons and nerves responsible for the control of nasofacial and oral airways patency simultaneously. Bilateral pFRG inhibition abolished active expiration and the simultaneous nasofacial and oral motor activities induced by hypercapnia/acidosis. The pFRG is more than a rhythmic oscillator for expiratory pump muscles: it also coordinates nasofacial and oral motor commands that engage muscles controlling airways. ABSTRACT: Active expiration is mediated by an expiratory oscillator located in the parafacial respiratory group (pFRG). Active expiration requires more than contracting expiratory muscles as multiple cranial nerves are recruited to stabilize the naso- and oropharyngeal airways. We tested the hypothesis that activation of the pFRG recruits facial and trigeminal motoneurons to coordinate nasofacial and oral motor activities that engage muscles controlling airways in rats during active expiration. Using a combination of electrophysiological and pharmacological approaches, we identified brainstem circuits that phase-lock active expiration, nasofacial and oral motor outputs in an in situ preparation of rat. We found that either high chemical drive (hypercapnia/acidosis) or unilateral excitation (glutamate microinjection) of the pFRG evoked active expiration and stimulated motoneurons (facial and trigeminal) and motor nerves responsible for the control of nasofacial (buccal and zygomatic branches of the facial nerve) and oral (mylohyoid nerve) motor outputs simultaneously. Bilateral pharmacological inhibition (GABAergic and glycinergic receptor activation) of the pFRG abolished active expiration and the simultaneous nasofacial and oral motor activities induced by hypercapnia/acidosis. We conclude that the pFRG provides the excitatory drive to phase-lock rhythmic nasofacial and oral motor circuits during active expiration in rats. Therefore, the pFRG is more than a rhythmic oscillator for expiratory pump muscles: it also coordinates nasofacial and oral motor commands that engage muscles controlling airways in rats during active expiration.

Consideraciones anestésicas en hipercapnia intraoperatoria, a propósito de un caso / Case report: Anesthetic considerations in intraoperative hipercapnia

Hypercapnia during the intraoperative period is one of the relevant conditions for the anesthesiologist, which can even condition the anesthetic technique, in case of an eventual complication. Where ventilatory monitoring and the interpretation of said disorder allows to diagnose, plan and treat the physiological consequences in the patient. We present the case of a 20 year old patient, scheduled for orthognathic surgery for diagnosis of mandibular body fracture, without added pathologies, no chest trauma, no ventilation disorders. It is presented with the objective of discussing the different considerations to be taken before the progressive establishment of hypercapnia, its causes, consequences and its management.

La hipercapnia durante el intraoperatorio es una de las condiciones relevantes para el anestesiólogo, la cual puede incluso condicionar la técnica anestésica ante una eventual complicación. Donde la monitorización ventilatoria y la interpretación de dicho trastorno permite diagnosticar, planificar y tratar las consecuencias fisiológicas en el paciente. Presentamos el caso de una paciente de 20 años programada para cirugía ortognática por diagnóstico de fractura de cuerpo mandibular, sin patologías añadidas no traumas torácicos, no trastornos de ventilación. Se presenta con el objetivo de discutir las diferentes consideraciones a tomar ante la instauración progresiva de hipercapnia sus causas, consecuencias así como su manejo.

Hypercapnia Response in Patients with Obesity-Hypoventilation Syndrome Treated with Non-Invasive Ventilation at Home. / Respuesta a la hipercapnia en pacientes con síndrome obesidad-hipoventilación en tratamiento con ventilación no invasiva en domicilio.

INTRODUCTION: Respiratory center (RC) dysfunction has been implicated in the pathogenesis of obesity-hypoventilation syndrome (OHS), and often requires treatment with home non-invasive ventilation (NIV). Our objective was to measure the effect of NIV on RC function in patients with OHS, and the factors that determine such an effect. METHODS: We performed a prospective, repeated measures study to evaluate hypercapnia response (HR) by determining the p01/pEtCO2 ratio slope at baseline and after 6months of treatment with NIV in a group of OHS patients. A threshold of 0.22cmH2O/mmHg had previously been established in a control group, in order to differentiate optimal RC response from suboptimal RC response. RESULTS: A total of 36 cases were included, 19 men (52%) aged 65 (SD 9) years, 63% of whom had p01/pEtCO2 below the reference value. Baseline p01/pEtCO2 was 0.17 (SD: 0.14) cmH2O/mmHg and, after 6 months of NIV, 0.30 (SD: 0.22) cmH2O/mmHg (p=0.011). After 6months of treatment with NIV, depressed RC function persisted in 12 cases (33%). CONCLUSION: In total, 63% of OHS patients had RC dysfunction. The application of NIV improves RC function but not in all cases.

Nuevo dispositivo de micronebulización con control continuo de la fracción inspirada de oxígeno ("CONTROLizer") / New micronebulizer device with continuous control of the inspired oxygen fraction ("CONTROLizer")

Resumen Una de las técnicas más comunes de tratamiento respiratorio es la nebulización de medicamentos para administrarlos por vía inhalada utilizando oxígeno como propelente, el cual a su vez es considerado un fármaco que puede generar efectos adversos relacionados con la dosificación. El objetivo de esta investigación fue diseñar, desarrollar y analizar un sistema dual de micronebulización con control preciso de la FIO2. Métodos: se diseñó, construyó y evaluó un modelo virtual y un prototipo funcional siguiendo la metodología de bioingeniería de un nuevo dispositivo de micronebulización con control de FIO2. Se evaluó el funcionamiento del dispositivo y su impacto en voluntarios sanos y pacientes hospitalizados mediante escalas psicométricas específicas. Resultados: se conceptualizó, diseñó y construyó un dispositivo que integra un micronebulizador (recipiente), que permite nebulizar suero fisiológico o soluciones de diversos fármacos basado en la presurización de un gas propelente (aire u oxígeno) junto a un mecanismo de ajuste de la fracción inspirada de O2 (mínimo 21%; máximo 99%). Los límites (máximo y mínimo) de flujo recomendado para generar el aerosol son 6-8 l/min. En ningún caso de uso se presentaron complicaciones. Conclusiones: CONTROLizer es un dispositivo integrado dual y no-invasivo para la micronebulización de soluciones respiratorias y control continuo de la fracción inspirada de oxígeno. Por sus cualidades y funcionamiento, el dispositivo fue percibido como adecuado y seguro para aplicarse en individuos sanos y pacientes ingresados tanto en salas de cuidados intensivos como de hospitalización convencional. (Acta Med Colomb 2018; 43: 90-99).

Abstract One of the most common techniques of respiratory treatment is the nebulization of medications to be administered by inhalation using oxygen as a propellant, which in turn is considered a drug that can generate adverse effects related to the dosage. The objective of this research was to design, develop and analyze a dual micronebulization system with precise control of FIO2. Methods: a virtual model and a functional prototype were designed, constructed and evaluated following the bioengineering methodology of a new micronebulizer device with FIO2 control. The functioning of the device and its impact on healthy volunteers and hospitalized patients were evaluated through specific psychometric scales. Results: a device that integrates a micronebulizer (container), which allows to nebulize physiological saline or solutions of diverse drugs based on the pressurization of a propellant gas (air or oxygen) along with a mechanism of adjustment of the fraction of inspired oxygen (minimum 21%, maximum 99%), was conceptualized, designed and constructed. The limits (maximum and minimum) of recommended flow to generate the aerosol are 6-8 l / min. In no case of use complications occurred. Conclusions: CONTROLizer is a dual and non-invasive integrated device for the micronebulization of respiratory solutions and continuous control of the fraction of inspired oxygen. Due to its qualities and functioning, the device was perceived as adequate and safe to be applied in healthy individuals and patients admitted in both intensive care and conventional hospitalization rooms. (Acta Med Colomb 2018; 43: 90-99).

Obesity-hypoventilation syndrome and associated factors. / Síndrome de obesidad-hipoventilación y factores asociados.

BACKGROUND AND OBJECTIVES: Obesity causes important alterations in the respiratory physiology like sleep obstructive apnoea (SOA) and obesity-hypoventilation syndrome (OHS), both associated with high morbidity and mortality. Also, these entities are clearly infradiagnosed and in the case of OHS the prevalence is unknown in the general obese population. To determine the prevalence of OHS in the population of patients with morbid obesity and to know the comorbidity related with OHS, the associated respiratory symptoms and the pulse oximetry alterations. PATIENTS AND METHOD: Descriptive study. Selection of 136 adult patients with morbid obesity (BMI >40). Collected were, anthropometric data, toxic habits, concomitant disease, symptom data, analytic data, dyspnoea grade, sleepiness scale (Epworth Test), electrocardiogram, chest X-ray, spirometry, nocturne ambulatory pulse oximetry and arterial gasometry. RESULTS: 136 were studied, mean age 60 years old (SD 12.9 years), 73% (98) were women; 6.6% of patients presented diurnal hypercapnia indicative of OHS; 72% presented high blood pressure, 44% dyslipidaemia, 18% presented cardiovascular disease, 83% snored and 46% had apnoea; 30% presented stageII dyspnoea and 10% stageIII. The desaturation/hour index was above 3% ≥30 of occasions in 28.6% of patients and the percentage of patients with saturations <90% more than 30% of the time was 23.5%. The results were worse in patients with OHS. CONCLUSIONS: The prevalence of OHS was lower than expected. Noteworthy was the high comorbidity of cardiovascular disease and the high frequency of respiratory symptoms associated with important alterations of pulse oximetry.

Insuflação de gás traqueal como recurso terapêutico em ventilação mecânica invasiva: revisão sistemática / Tracheal gas insufflation as a therapeutic resource in invasive mechanical ventilation: a systematic review

Introdução: A unidade de terapia intensiva, pacientes que apresentam um grave comprometimento pulmonar, com alterações nos valores fisiológicos de complacência pulmonar, acabam desenvolvendo uma limitação relacionada a volumes pulmonares. Um dos problemas resultantes é a hipercapnia. Para ajudar a reduzir essas alterações, pode-se usar técnicas como a insuflação de gás traqueal (TGI), que atua minimizando o estresse pulmonar, melhorando as trocas gasosas e reduzindo o volume minuto ventilatório e a pressão. Assim, o objetivo deste estudo foi analisar e descrever o uso de TGI e a sua eficácia na redução da hipercapnia e nos parâmetros da ventilação mecânica invasiva de pacientes críticos. Métodos: Foi realizada uma revisão sistemática da literatura com busca nas bases de dados do SciELO, LILACS, PubMed e MEDLINE, com publicações de 2005 a 2016. Foram identificados um total de 1.437 artigos. Os critérios de elegibilidade foram a utilização do método de TGI isolado ou combinado a outros recursos e a inclusão de desfechos da sua efetividade em amostras experimentais ou humanas que mostravam lesão pulmonar e/ou outras alterações pulmonares, entre elas a hipercapnia. Resultados: Após a leitura e análise criteriosa dos artigos, 10 estudos foram incluídos nesta revisão. Eles abordavam a eficácia dos métodos de TGI na redução dos níveis de CO2 e as condições para a diminuição dos parâmetros da ventilação mecânica e melhora da mecânica ventilatória. Conclusão: Os estudos incluídos na presente revisão sugerem que a TGI pode ser uma técnica eficaz quando realizada em complicações pulmonares nos pacientes hipercápnicos com lesão pulmonar. Entretanto, são estudos distintos e controversos, o que compromete a análise dos resultados obtidos para total eficácia do recurso terapêutico. (AU)

Introduction: At intensive care units, patients presenting with severe pulmonary involvement, with changes in the physiological values of pulmonary compliance, develop a limitation related to pulmonary volumes, resulting in some cases in hypercapnia. In order to help decreasing these alterations, some techniques may be used such as tracheal gas insufflation (TGI), which acts minimizing pulmonary stress, improving gas exchanges and decreasing respiratory minute volume and pressure. Thus, this study aimed to analyze and to describe TGI use and efficacy in reducing hypercapnia and parameters of invasive mechanical ventilation of critically ill patients. Methods: For this systematic review, we searched SciELO, LILACS, PubMed and MEDLINE databases for articles published from 2005 to 2016. A total of 1,437 articles were found. The eligibility criteria were the use of TGI alone or together with other resources and the evaluation of its effectiveness in experimental or human samples that showed lung injury and/or other pulmonary abnormalities, including hypercapnia. Results: After careful reading and analysis of the articles, 10 studies were included in this review. They addressed the effectiveness of TGI methods in reducing levels of CO2 levels and conditions to decrease parameters of mechanical ventilation and to improve ventilation mechanics. Conclusion: The studies included in the present review suggest that TGI may be an efficient technique when applied to pulmonary complications of patients suffering from hypercapnia with pulmonary lesions. However, the studies are different and controversial, which compromises the analysis of the results obtained for total efficacy of the therapeutic resource. (AU)

Changes in arterial partial pressure and end-expired pressure of carbon dioxide in prepubescent and adult bitches undergoing ovariohysterectomy by videolaparoscopy or conventional laparotomy / Variações nas pressões parciais arteriais e expiradas de dióxido de carbono em cadelas pré-púberes e adultas submetidasà ovário histerectomiavídeo laparoscópica ou convencional

ABSTRACT: This paper aimed to determine arterial partial pressure of carbon dioxide (PaCO2), end-expired CO2 pressure (ETCO2), and the difference between arterial and end-expired CO2 pressure (Pa - ETCO2) in prepubescent and adult bitches undergoing videolaparoscopic or conventional ovariohyterectomy (OH). Forty bitches were randomly assigned to four groups: Conventional Adult (CA), Conventional Pediatric (CP), Videolaparoscopic Adult (VA) and Videolaparoscopic Pediatric (VP). Pulse rate (PR), respiratory rate (RR), systolic, mean, and diastolic arterial pressures (SAP, MAP, DAP), ETCO2, peak inspiratory pressure (PIP), pH, arterial partial pressure of oxygen (PaO2), PaCO2, base excess (BE) and HCO3 - were measured. Based on the PaCO2 and ETCO2 values, Pa-ETCO2 was determined. There was no significant difference in PaCO2 between the VA (42.5±5.2 to 53.7±5.2) and VP (48.4±5.4 to55.4±5.7) groups. During the postoperative period, all groups presented with hypertension. However, mild hypertension (SAP 150 to 159mmHg) was observed in the VP group as compared to severe hypertension (SAP>180mmHg) in the CA group, suggesting that both the age range and videolaparoscopic OH are associated with lower levels of hypertension during the postoperative period in dogs.

RESUMO: O objetivo deste estudo foi determinar a pressão parcial de dióxido de carbono (PaCO2), pressão ao final da expiração de CO2 (ETCO2) e diferença artério-alveolar de CO2 (Pa-ETCO2) em cadelas pré-púberes e adultas submetidas à ovário-histerectomia (OH) videolaparoscópica ou convencional. Foram distribuídas 40 cadelas em quatro grupos: Convencional Adulto (CA), Convencional Pediátrico (CP), Videolaparoscópico Adulto (VA) e Videolaparoscópico Pediátrico (VP). Foram mensurados frequência de pulso (FP), frequência respiratória (FR), pressões arteriais sistólica (PAS), média (PAM) e diastólica (PAD), ETCO2, pressão de pico inspiratória (PIP), pH, pressão parcial arterial de oxigênio (PaO2), PaCO2, excesso de bases (EB) e HCO3 -. Com base nos valores de PaCO2 e ETCO2 encontrados, foi determinada a Pa-ETCO2. Não foram encontradas diferenças significativas nos valores de PaCO2 entre os grupos VA (42.5±5.2-53,7±5,2) e VP (48.4±5.4 - 55,4±5,7). Todos os grupos apresentaram hipertensão arterial no período pós-operatório. Entretanto, o grupo VP apresentou hipertensão moderada (PAS 150-159mmHg) em comparação ao grupo CA, que apresentou hipertensão severa (PAS>180 mmHg), sugerindo que tanto a faixa etária, quanto a execução de OH por videolaparoscopia, estão associadas a menores taxas de hipertensão pós-operatória em cadelas.

Fisiopatología del síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) / Pathophysiology of obstructive sleep apnea-hypopnea syndrome (OSAHS)

Resumen El síndrome de apnea-hipopnea obstructiva del sueño (SAHOS) es una enfermedad caracterizada por la obstrucción recurrente de la vía aérea superior (VAS), con disminución en el flujo de aire, hipoxemia intermitente y despertares durante el sueño. En la fisiopatología del SAHOS se presentan dos factores esenciales: las alteraciones anatómicas y la disminución o ausencia del control neural. Durante el estudio del SAHOS se debe identificar el sitio o sitios de obstrucción de la VAS, que pueden ir desde las alas nasales hasta la hipofaringe. Otro factor importante en este síndrome es el influjo nervioso en el tono muscular de la hipofaringe, así como los cambios en el pH sanguíneo y secundarios a los microdespertares. La posición corporal y el estadio de sueño son factores determinantes de la severidad. La fisiopatología del SAHOS debe ser entendida para poder estudiar de forma adecuada a un paciente y darle la mejor opción de tratamiento.

Abstract Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a disease characterized by recurrent upper airway obstruction (UAO), with decreased airflow, intermittent hypoxemia, and awakening during sleep. Two essential factors are related to the pathophysiology of OSAHS: anatomical alterations and reduction or absence of neural control. While studying OSAHS, the site or sites of obstruction of the UA should be identified; they may extend from the nasal wings to the hypopharynx. Another important factor in this syndrome is the nervous influence on muscle tone of the hypopharynx, as well as the changes in blood pH, which are secondary to micro-arousals. Body position and sleep stage determine the severity. The pathophysiology of OSAHS should be understood to properly study a patient and provide the best treatment option.

Pre-emptive methadone or tramadol analgesia for mastectomy and ovariohysterectomy in bitches / Analgesia preventiva con tramadol o metadona para mastectomia y ovario histerectomía en perras / Analgesia preventiva com tramadol ou metadona para mastectomia e ováriohisterectomia em cadelas

Summary Background: mastectomy in bitches is a critical surgery and pain control can be challenging. Objective: to evaluate the efficacy of pre-emptive analgesia with methadone (MET) or tramadol (TRA) in postoperative pain management, cardiorespiratory effects, and anaesthetic/analgesic consumption in female dogs undergoing ovariohysterectomy (OVH) and mastectomy. Methods: a prospective randomized blind clinical trial was used to evaluate 48 bitches of various breeds, aged 10±3.7 years, weighing 16±12 kg, and with multiple mammary tumours. The animals were distributed in two groups: TRA group received 5 mg/kg tramadol and MET group 0.5 mg/kg methadone intramuscularly, 10 minutes prior to anaesthesia induction with propofol followed by maintenance with isoflurane. Heart (HR) and respiratory (RR) rates, mean arterial pressure (MAP), propofol induction dose (PID), oxyhemoglobin saturation (SpO2), end-tidal isoflurane concentration (EtISO), and carbon dioxide pressure (EtCO2) were measured during the intra-operative period. Post-operative pain was evaluated for 12 hours and rated according to the Melbourne pain scale. Rescue analgesia (0.5 mg/kg methadone, 2 mg/kg lidocaine, or 0.01 mg/kg/min ketamine IV) was given when necessary and post-operative analgesic consumption recorded. Statistical tests were used to compare treatments. Results: rescue analgesia requirements, pain score, PID and analgesic consumption were significantly lower (p<0.05) in MET group. The HR was higher in TRA group, while EtCO2 and MAP were higher in MET group (p<0.05). Conclusions: methadone was more effective than tramadol in pre-emptive analgesia but not completely adequate on controlling pain in bitches subjected to unilateral mastectomy and OVH. MET led to lower cardiovascular depression and lower propofol dose required for anesthesia induction. However, methadone increased EtCO2 and thus special care with patient ventilation is advised.

Resumen Fundamento: la mastectomia en perras es un procedimiento severamente álgido y el control del dolor es un desafío. Objetivo: evaluar la eficacia del tratamiento analgésico preventivo con metadona (MET) o tramadol (TRA) sobre el dolor postoperatorio, parámetros cardiorrespiratorios y consumo de anestésicos en perras sometidas a ovariohisterectomía (OVH) y mastectomía. Métodos: ensayo clínico prospectivo aleatorizado ciego en 48 perras de diversas razas, edad 10±3,7, peso corporal 16±12 kg y con múltiples tumores mamarios. Los animales fueron distribuidos en dos grupos: el grupo TRA recibió 5 mg/kg de tramadol y el grupo MET 0,5 mg/kg de metadona por vía intramuscular 10 minutos antes de inducir anestesia con propofol seguido de mantenimiento con isofluorano. Las variables evaluadas fueron: frecuencia cardíaca (HR), respiratoria (RR), presión arterial media (MAP), dosis de inducción con propofol (PID), saturación de oxihemoglobina (SpO2), concentración de isofluorano (EtISO) y presión de dióxido de carbono (EtCO2) medidos durante el proceso intra-operativo. El dolor postoperatorio fue evaluado de acuerdo con la escala Melbourne durante 12 horas. Analgesia de rescate (metadona 0.5 mg/kg, lidocaína 2 mg/kg, o ketamina 0.01 mg/kg/min IV) se suministró cuando se consideró necesario, y se registró el consumo de analgésico posterior a la cirugia. Se aplicaron pruebas estadísticas para comparar los tratamientos. Resultados: los requerimientos de rescate analgésico, intensidad del dolor, PID y consumo analgésico fueron significativamente menores (p<0,05) en el grupo MET. La HR fue mayor en el grupo TRA, mientras que EtCO2 y MAP fueron mayores en el grupo MET (p<0,05). Conclusiones: la administración preventiva de MET es más eficaz que el tramadol, pero no completamente adecuada para el control del dolor posoperatorio en perras sometidas a mastectomia unilateral y OVH. MET promueve menor depresión cardiovascular y requerimiento de propofol para inducción anestésica. Sin embargo, dado que MET incrementa la EtCO2, se recomienda cuidado especial con la ventilación de estos pacientes.

Resumo Introdução: a mastectomia em cadelas é um procedimento severamente álgido e o controle da dor é um desafio. Objetivo: avaliar a eficácia da analgesia preventiva com metadona ou tramadol sob dor pós-operatória, parâmetros cardiorrespiratórios e consumo anestésico em cadelas submetidas à ovariohisterectomia e mastectomia. Métodos: ensaio clínico prospectivo cego randomizado em 48 cadelas, de diferentes raças, idade 10 ± 3,7 anos, peso 16 ± 12 kg com tumores mamários múltiplos. Os animais foram distribuídos em dois grupos: grupo TRA, tramadol 5 mg/kg e grupo MET, metadona 0,5 mg/kg por via intramuscular, administrados 10 minutos antes da indução anestésica com propofol e manutenção com isofluorano. As variáveis mensuradas foram: frequência cardíaca (FC), respiratória (fR), pressão arterial média (PAM), dose de indução propofol (PID), saturação da oxihemoglobina (SpO2), concentração de isofluorano (EtISO) e pressão de dióxido de carbono (EtCO2) ao final da expiração. A dor pós-operatória foi avaliada durante 12 horas (Escala Melbourne). A necessidade de resgate (metadona 0.5 mg/kg, lidocaína 2 mg/kg, ou cetamina 0.01 mg/kg/min IV) analgésico e o consumo pós-operatório de analgésicos foram registrados. Testes estatísticos foram utilizados para comparar os tratamentos. Resultados: a necessidade de resgate analgésico, escore de dor, PID e o consumo de analgésicos foram menores (p<0,05) no grupo MET. A FC maior no grupo TRA, enquanto EtCO2 e PAM maiores no grupo MET (p<0,05). Conclusões: a administração preventiva de metadona foi mais eficaz, mas não totalmente adequada para o controle da dor pós-operatória do que o tramadol, promovendo redução na depressão cardiovascular e o requerimento de propofol para indução da anestesia. No entanto, a metadona aumentou a EtCO2, recomendando cuidado especial com a ventilação dos pacientes.

Extracorporeal respiratory support in adult patients / Suporte respiratório extracorpóreo em pacientes adultos

ABSTRACT In patients with severe respiratory failure, either hypoxemic or hypercapnic, life support with mechanical ventilation alone can be insufficient to meet their needs, especially if one tries to avoid ventilator settings that can cause injury to the lungs. In those patients, extracorporeal membrane oxygenation (ECMO), which is also very effective in removing carbon dioxide from the blood, can provide life support, allowing the application of protective lung ventilation. In this review article, we aim to explore some of the most relevant aspects of using ECMO for respiratory support. We discuss the history of respiratory support using ECMO in adults, as well as the clinical evidence; costs; indications; installation of the equipment; ventilator settings; daily care of the patient and the system; common troubleshooting; weaning; and discontinuation.

RESUMO Em pacientes com insuficiência respiratória grave (hipoxêmica ou hipercápnica), o suporte somente com ventilação mecânica pode ser insuficiente para suas necessidades, especialmente quando se tenta evitar o uso de parâmetros ventilatórios que possam causar danos aos pulmões. Nesses pacientes, extracorporeal membrane oxygenation (ECMO, oxigenação extracorpórea por membrana), que também é muito eficaz na remoção de dióxido de carbono do sangue, pode manter a vida, permitindo o uso de ventilação pulmonar protetora. No presente artigo de revisão, objetivamos explorar alguns dos aspectos mais relevantes do suporte respiratório por ECMO. Discutimos a história do suporte respiratório por ECMO em adultos; evidências clínicas; custos; indicações; instalação do equipamento; parâmetros ventilatórios; cuidado diário do paciente e do sistema; solução de problemas comuns; desmame e descontinuação.

[Relation between ultrasound-measured diaphragm movement and partial pressure of carbon dioxide in blood from patients with acute hypercapnic respiratory failure after the start of noninvasive ventilation in an emergency department]. / Relación entre la movilidad diafragmática medida por ecografía y la presión parcial arterial de CO2 en pacientes con insuficiencia respiratoria aguda hipercápnica tras el inicio de la ventilación mecánica no invasiva en urgencias.

OBJECTIVES: To evaluate the correlation between variations in ultrasound-measured diaphragm movement and changes in the arterial partial pressure of carbon dioxide (PCO2) after the start of noninvasive ventilation (NIV). MATERIAL AND METHODS: RDescriptive study of a prospective case series comprised of nonconsecutive patients aged 18 years or older with hypercapnic respiratory failure who were placed on NIV in an emergency department. We recorded clinical data, blood gas measurements, and ultrasound measurements of diaphragm movement. RESULTS: Twenty-one patients with a mean (SD) age of 83 (13) years were studied; 11 (52.4%) were women. The mean (SD) range of diaphragm movement and PCO2 values at 4 moments were as follows: 1) at baseline: diaphragm movement, 13.90 (7.7) mm and PCO2, 71.75 (11.4) mm Hg; 2) after 15 minutes on NIV: diaphragm movement, 17.10 (9.1) mm; 3) at 1 hour: diaphragm movement, 22.40 (10.4) mm and PCO2, 63.45 (16.0) mm Hg; and 4) at 3 hours: diaphragm movement, 26.60 (19.5) mm and PCO2, 61.85 (13.0) mm Hg. We detected a statistically significant correlation between the difference in range of diaphragm movement at baseline and at 15 minutes and the decrease in PCO2 after 1 hour of NIV (r=-0.489, P=.035). CONCLUSION: In patients with hypercapnic respiratory failure, the increase in range of diaphragm movement 15 minutes after starting NIV is associated with a decrease in PCO2 after 1 hour.

OBJETIVO: Correlacionar la variación de la movilidad diafragmática (MD), medida a través de ecografía, con el cambio en la presión parcial arterial de CO2 de (pCO2) tras el inicio de la ventilación mecánica no invasiva (VMNI). METODO: Estudio descriptivo de una serie de casos prospectivo que incluyó por oportunidad a los pacientes de 18 o más años con insuficiencia respiratoria hipercápnica en los que se inició la VMNI en urgencias. Se recogieron variables clínicas, gasométricas y mediciones ecográficas de la MD directa (MDD) y MD portal (MDP). RESULTADOS: Se incluyeron 21 pacientes, con una edad media de 83 (DE 13) años, de ellos 11 mujeres (52,4%). Los valores de MDD y pCO2 fueron: 1) basal: MDD 13,9 (DE 7,7) mm y pCO2 71,7 (DE: 11,4) mmHg; 2) 15 minutos: MDD 17,1 (DE 9,1) mm; 3) 1 hora: MDD 22,4 (DE 10,4) y pCO2 63,4 (DE: 16,0) mmHg; 4) 3 horas: MDD 26,6 (DE: 19,5) mm y pCO2 61,8 (DE :13,0) mmHg. Hubo correlación estadísticamente significativa entre la diferencia a los 15 minutos y basal de MDD y el descenso a la hora de pCO2 (r = ­0,489; p = 0,035). CONCLUSIONES: El aumento de la MDD a los 15 minutos del inicio de la VMNI se relaciona con una disminución de la pCO2 a la hora en los pacientes con insuficiencia respiratoria hipercápnica.

Ventilação mecânica não invasiva na crise de asma aguda grave em crianças: níveis de evidências / Noninvasive ventilation in status asthmaticus in children: levels of evidence

RESUMO Objetivo: Avaliar a qualidade das evidências existentes para embasar diretrizes do emprego da ventilação mecânica não invasiva no manejo da crise de asma aguda grave em crianças não responsivas ao tratamento padrão. Métodos: Busca, seleção e análise de todos os artigos originais sobre asma e ventilação mecânica não invasiva em crianças, publicados até 1º de setembro de 2014, em todos os idiomas, nas bases de dados eletrônicas PubMed, Web of Science, Cochrane Library, Scopus e SciELO, encontrados por meio de busca pelos descritores "asthma", "status asthmaticus", "noninvasive ventilation", "bronchospasm", "continuous positive airway pressure", "child", "infant", "pediatrics", "hypercapnia", "respiratory failure", e das palavras-chave "BIPAP", "CPAP", "bilevel", "acute asthma" e "near fatal asthma". Os artigos foram qualificados segundo os graus de evidências do Sistema GRADE. Resultados: Foram obtidos apenas nove artigos originais. Destes, dois (22%) apresentaram nível de evidência A, um (11%) apresentou nível de evidência B e seis (67%) apresentaram nível de evidência C. Conclusão: Sugere-se que o emprego da ventilação mecânica não invasiva na crise de asma aguda grave em crianças não responsivas ao tratamento padrão é aplicável à maioria desses pacientes, mas as evidências não podem ser consideradas conclusivas, uma vez que pesquisa adicional de alta qualidade provavelmente tenha um impacto modificador na estimativa de efeito.

ABSTRACT Objective: To evaluate the quality of available evidence to establish guidelines for the use of noninvasive ventilation for the management of status asthmaticus in children unresponsive to standard treatment. Methods: Search, selection and analysis of all original articles on asthma and noninvasive ventilation in children, published until September 1, 2014 in all languages in the electronic databases PubMed, Web of Science, Cochrane Library, Scopus and SciELO, located using the search terms: "asthma", "status asthmaticus", "noninvasive ventilation", "Bronchospasm", "continuous positive airway pressure", "child", "infant", "pediatrics", "hypercapnia", "respiratory failure" and the keywords "BIPAP", "CPAP", "Bilevel", "acute asthma" and "near fatal asthma". The articles were assessed based on the levels of evidence of the GRADE system. Results: Only nine original articles were located; two (22%) articles had level of evidence A, one (11%) had level of evidence B and six (67%) had level of evidence C. Conclusion: The results suggest that noninvasive ventilation is applicable for the treatment of status asthmaticus in most pediatric patients unresponsive to standard treatment. However, the available evidence cannot be considered as conclusive, as further high-quality research is likely to have an impact on and change the estimate of the effect.

Respiratory CO2 response depends on plasma bicarbonate concentration in mechanically ventilated patients.

OBJECTIVE: There is controversy about the effects of high plasma bicarbonate concentration ([HCO3(-)]) and the CO2 response test. We analyzed the relationship between [HCO3(-)] and the variation in hydrogen ion concentration (pH) for a given change in PaCO2, and its effects upon CO2 response. DESIGN: A retrospective study was carried out. SETTING: Two intensive care units. PATIENTS: Subjects with and without chronic obstructive pulmonary disease (COPD), at the beginning of weaning from mechanical ventilation. INTERVENTIONS: The CO2 response was evaluated by the re-inhalation of expired air method, measuring the hypercapnic ventilatory response (ΔVE/ΔPaCO2) and hypercapnic drive response (ΔP01/ΔPaCO2), where VE is minute volume and P0.1 is airway occlusion pressure 0.1s after the initiation of inspiration. MAIN OUTCOME MEASURES: [HCO3(-)] and CO2 response. RESULTS: A total of 120 patients in the non-COPD group and 48 in the COPD group were studied. COPD patients had higher mean [HCO3(-)] than non-COPD patients (33.2 ± 5.4 vs. 25.7 ± 3.7 mmol/l, p<0.001). In both non-COPD and COPD patients we observed a significant inverse linear relationship between [HCO3(-)] and pH change per mmHg of PaCO2 (p<0.001), ΔVE/ΔPaCO2 (p<0.001) and ΔP0.1/ΔPaCO2 (p<0.001). CONCLUSIONS: There is an inverse linear relationship between [HCO3(-)] and the variation of pH for a given change in PaCO2 and the CO2 response.