Papel del Delta de PCO2 en la evaluación pronóstica de morbimortalidad en una cohorte de pacientes de un hospital latinoamericano / Role of PCO2 Delta in the Prognostic Evaluation of Morbidity and Mortality in a Cohort of Patients from a Latin American Hospital

Introducción. El shock séptico es la manifestación más grave de sepsis con tasas de letalidad que pueden llegar hasta el 80%. En los últimos años, ha cobrado relevancia la diferencia arteriovenosa de dióxido de carbono, por su implicación teórica en el metabolismo anaerobio y su significado respecto del normal funcionamiento celular. Por lo antes mencionado, creemos necesario realizar un estudio que nos permita establecer la utilidad de la diferencia arteriovenosa de dióxido de carbono en el paciente con shock séptico de la unidad de cuidados intensivos, como medida indirecta de la perfusión tisular y de la utilización de oxígeno por los tejidos, que nos permita establecer un diagnóstico precoz y el pronóstico de los pacientes críticamente enfermos. Métodos. Estudio observacional, descriptivo y transversal. Muestra de veintiocho pacientes adultos. Resultados. Como se ha registrado en otras series, la mayor parte de los pacientes afectados por shock séptico, en nuestro estudio, fueron hombres mayores de 65 años, con al menos una comorbilidad, siendo el principal sitio de infección el respiratorio (67,9%), asociado a una alta tasa de mortalidad (67%). Conclusiones. Los pacientes con diferencia arteriovenosa de PCO2 mayor a 6 mmHg tienen un riesgo aumentado de muerte de 3,2 veces. (AU)

Introduction. Septic shock is the most serious manifestation of sepsis with mortality rates that can reach up to 80%. In recent years, the arteriovenous carbon dioxide difference has gained relevance, due to its theoretical implication in anaerobic metabolism and its significance with respect to normal cell function. Due to the aforementioned, we believe it is necessary to carry out a study that allows us to establish the usefulness of the arteriovenous carbon dioxide difference in the patient with septic shock in the intensive care unit as an indirect measure of tissue perfusion and utilization. of oxygen through the tissues, which allows us to establish an early diagnosis and prognosis of critically ill patients. Methods. Observational, descriptive and cross-sectional study. Sample of 28 adult patients. Results. As has been reported in other series, most of the patients affected by septic shock in our study were men over 65 years of age, with at least one comorbidity, the main site of infection being respiratory (67.9%), associated with a high mortality rate (67%) Conclusions. Patients with an arteriovenous PCO2 difference greater than 6 mmHg have a 3.2-fold increased risk of death. (AU)

Fisiología respiratoria: transporte de gases en sangre / Respiratory physiology: transport of oxygen and carbon dioxide in the blood

La sangre normalmente transporta pequeñas cantidades de oxígeno (O2) disuelto en el plasma y altas cantidades combinadas en forma química con la hemoglobina. La presión parcial depende solo del oxígeno disuelto físicamente, lo que determina cuánto oxígeno se combinará con hemoglobina. La curva de disociación de la hemoglobina describe la reversibilidad de la reacción entre oxígeno y hemoglobina. Los factores habituales que aumentan o disminuyen la afinidad de la hemoglobina por el oxígeno son el pH, presión parcial de CO2, temperatura y 2,3 difosfoglicerato. La sangre también transporta grandes cantidades en forma de bicarbonato y bajas cantidades de CO2 disuelto en plasma y combinado con proteínas como compuestos carbamino. La desoxihemoglobina favorece la formación de compuestos carbamínicos y promueve el transporte del CO2 como bicarbonato uniéndose al hidrógeno proveniente de la disociación del ácido carbónico. A continuación se describe en forma detallada los mecanismos fisiológicos del transporte de gases en sangre.

Blood normally carries small amounts of oxygen dissolved in plasma and large amounts chemically combined with hemoglobin. Partial pressure of oxygen depends only on physically dissolved oxygen which determines how much oxygen will combine with hemoglobin. The oxygen-hemoglobin dissociation curve (or oxyhemoglobin dissociation curve) describes the reversibility of the reaction between oxygen and hemoglobin. The usual factors that increase or decrease the affinity of hemoglobin for oxygen are pH, CO2 partial pressure, temperature, and 2,3 diphosphoglycerate. Blood also carries large amounts of CO2 as bicarbonate and low amounts dissolved in plasma and combined with proteins as carbamino compounds. Deoxyhemoglobin favors the formation of carbamino compounds and promotes the transport of CO2 as bicarbonate by joining the hydrogen from the dissociation of carbonic acid. The physiological mechanisms of gas transport in blood are described in detail below.

Panic disorder respiratory subtype: psychopathology and challenge tests - an update

Panic disorder (PD) pathophysiology is very heterogeneous, and the discrimination of distinct subtypes could be very useful. A subtype based on respiratory symptoms is known to constitute a specific subgroup. However, evidence to support the respiratory subtype (RS) as a distinct subgroup of PD with a well-defined phenotype remains controversial. Studies have focused on characterization of the RS based on symptoms and response to CO2. In this line, we described clinical and biological aspects focused on symptomatology and CO2 challenge tests in PD RS. The main symptoms that characterize RS are dyspnea (shortness of breath) and a choking sensation. Moreover, patients with the RS tended to be more responsive to CO2 challenge tests, which triggered more panic attacks in this subgroup. Future studies should focus on discriminating respiratory-related clusters and exploring psychophysiological and neuroimaging outcomes in order to provide robust evidence to confirm RS as a distinct subtype of PD.

Uso da CPAP como alternativa para realização do teste de apneia durante determinação da morte encefálica em pacientes hipoxêmicos. Relato de dois casos / Use of CPAP as an alternative to the apnea test during the determination of brain death in hypoxemic patients. Report of two cases

RESUMO O teste de apneia com desconexão do ventilador mecânico representa riscos durante a determinação da morte encefálica, especialmente em pacientes hipoxêmicos. Descrevemos a realização do teste de apneia sem desconexão do ventilador mecânico em dois pacientes. O primeiro caso é o de um menino de 8 anos, admitido com hipoxemia grave por pneumonia. Apresentou parada cardiorrespiratória, seguida de coma não responsivo por encefalopatia hipóxico-isquêmica. Dois exames clínicos constataram ausência de reflexos de tronco, e o Doppler transcraniano revelou parada circulatória encefálica. Realizaram-se três tentativas de teste de apneia, que foram interrompidas por hipoxemia, sendo então realizado teste de apneia sem desconexão do ventilador mecânico, ajustando a pressão contínua nas vias aéreas em 10cmH2O e fração inspirada de oxigênio em 100%. A saturação de oxigênio manteve-se em 100% por 10 minutos. A gasometria pós-teste foi a seguinte: pH de 6,90, pressão parcial de oxigênio em 284,0mmHg, pressão parcial de dióxido de carbono em 94,0mmHg e saturação de oxigênio em 100%. O segundo caso é de uma mulher de 43 anos, admitida com hemorragia subaracnóidea (Hunt-Hess V e Fisher IV). Dois exames clínicos constataram coma não responsivo e ausência de todos os reflexos de tronco. A cintilografia cerebral evidenciou ausência de captação de radioisótopos no parênquima cerebral. A primeira tentativa do teste de apneia foi interrompida após 5 minutos por hipotermia (34,9oC). Após reaquecimento, o teste de apneia foi repetido sem desconexão do ventilador mecânico, evidenciando-se manutenção do volume residual funcional com tomografia de bioimpedância elétrica. Gasometria pós-teste de apneia apresentava pH em 7,01, pressão parcial de oxigênio em 232,0mmHg, pressão parcial de dióxido de carbono 66,9mmHg e saturação de oxigênio em 99,0%. O teste de apneia sem desconexão do ventilador mecânico permitiu a preservação da oxigenação em ambos os casos. O uso de pressão contínua nas vias aéreas durante o teste de apneia parece ser uma alternativa segura para manter o recrutamento alveolar e a oxigenação durante determinação da morte encefálica.

ABSTRACT The apnea test, which involves disconnection from the mechanical ventilator, presents risks during the determination of brain death, especially in hypoxemic patients. We describe the performance of the apnea test without disconnection from the mechanical ventilator in two patients. The first case involved an 8-year-old boy admitted with severe hypoxemia due to pneumonia. He presented with cardiorespiratory arrest, followed by unresponsive coma due to hypoxic-ischemic encephalopathy. Two clinical exams revealed the absence of brainstem reflexes, and transcranial Doppler ultrasound revealed brain circulatory arrest. Three attempts were made to perform the apnea test, which were interrupted by hypoxemia; therefore, the apnea test was performed without disconnection from the mechanical ventilator, adjusting the continuous airway pressure to 10cmH2O and the inspired fraction of oxygen to 100%. The oxygen saturation was maintained at 100% for 10 minutes. Posttest blood gas analysis results were as follows: pH, 6.90; partial pressure of oxygen, 284.0mmHg; partial pressure of carbon dioxide, 94.0mmHg; and oxygen saturation, 100%. The second case involved a 43-year-old woman admitted with subarachnoid hemorrhage (Hunt-Hess V and Fisher IV). Two clinical exams revealed unresponsive coma and absence of all brainstem reflexes. Brain scintigraphy showed no radioisotope uptake into the brain parenchyma. The first attempt at the apnea test was stopped after 5 minutes due to hypothermia (34.9°C). After rewarming, the apnea test was repeated without disconnection from the mechanical ventilator, showing maintenance of the functional residual volume with electrical bioimpedance. Posttest blood gas analysis results were as follows: pH, 7.01; partial pressure of oxygen, 232.0mmHg; partial pressure of carbon dioxide, 66.9mmHg; and oxygen saturation, 99.0%. The apnea test without disconnection from the mechanical ventilator allowed the preservation of oxygenation in both cases. The use of continuous airway pressure during the apnea test seems to be a safe alternative in order to maintain alveolar recruitment and oxygenation during brain death determination.

Proporção entre pressão venosa central menos arterial de dióxido de carbono e conteúdo arterial menos venoso central de oxigênio como indicador de oxigenação tissular: uma revisão narrativa / Central venous minus arterial carbon dioxide pressure to arterial minus central venous oxygen content ratio as an indicator of tissue oxygenation: a narrative review

RESUMO A proporção entre pressão venosa central menos arterial de dióxido de carbono e conteúdo de oxigênio arterial menos venoso central (Pcv-aCO2/Ca-cvO2) foi proposta como marcador substituto para quociente respiratório e indicador de oxigenação tissular. Alguns pequenos estudos observacionais identificaram que Pcv-aCO2/Ca-cvO2 acima de 1,4 se associa com hiperlactatemia, dependência de suprimento de oxigênio e maior mortalidade. Mais ainda, a Pcv-aCO2/Ca-cvO2 foi incorporada a algoritmos para avaliação da oxigenação tissular e ressuscitação. Contudo, a evidência para estas recomendações é bastante limitada e de baixa qualidade. O objetivo desta revisão narrativa foi analisar as bases metodológicas, os fundamentos fisiopatológicos e a evidência experimental e clínica para dar suporte à utilização da Pcv-aCO2/Ca-cvO2 como marcador substituto para quociente respiratório. De um ponto de vista fisiopatológico, o aumento do quociente respiratório secundariamente a reduções críticas no transporte de oxigênio é um evento dramático e com risco à vida. Entretanto, este evento é facilmente observável e provavelmente não demandaria maiores monitoramentos. Visto que o início do metabolismo anaeróbico é indicado pelo aumento súbito do quociente respiratório e que a faixa normal do quociente respiratório é ampla, o uso do ponto de corte definido como 1,4 para Pcv-aCO2/Ca-cvO2 não faz sentido. Estudos experimentais demonstraram que a Pcv-aCO2/Ca-cvO2 é mais dependente de fatores que modificam a dissociação do dióxido de carbono da hemoglobina do que do quociente respiratório, e o quociente respiratório e Pcv-aCO2/Ca-cvO2 podem ter comportamentos distintos. Estudos conduzidos em pacientes críticos demonstraram resultados controvertidos com relação à capacidade da Pcv-aCO2/Ca-cvO2 para predizer o desfecho, hiperlactatemia, anomalias microvasculares e dependência de suprimento de oxigênio. Um estudo randomizado controlado também demonstrou que a Pcv-aCO2/Ca-cvO2 é inútil como alvo para ressuscitação. A Pcv-aCO2/Ca-cvO2 deve ser interpretada com cautela em pacientes críticos.

ABSTRACT The central venous minus arterial carbon dioxide pressure to arterial minus central venous oxygen content ratio (Pcv-aCO2/Ca-cvO2) has been proposed as a surrogate for respiratory quotient and an indicator of tissue oxygenation. Some small observational studies have found that a Pcv-aCO2/Ca-cvO2 > 1.4 was associated with hyperlactatemia, oxygen supply dependency, and increased mortality. Moreover, Pcv-aCO2/Ca-cvO2 has been incorporated into algorithms for tissue oxygenation evaluation and resuscitation. However, the evidence for these recommendations is quite limited and of low quality. The goal of this narrative review was to analyze the methodological bases, the pathophysiologic foundations, and the experimental and clinical evidence supporting the use of Pcv-aCO2/Ca-cvO2 as a surrogate for respiratory quotient. Physiologically, the increase in respiratory quotient secondary to critical reductions in oxygen transport is a life-threatening and dramatic event. Nevertheless, this event is easily noticeable and probably does not require further monitoring. Since the beginning of anaerobic metabolism is indicated by the sudden increase in respiratory quotient and the normal range of respiratory quotient is wide, the use of a defined cutoff of 1.4 for Pcv-aCO2/Ca-cvO2 is meaningless. Experimental studies have shown that Pcv-aCO2/Ca-cvO2 is more dependent on factors that modify the dissociation of carbon dioxide from hemoglobin than on respiratory quotient and that respiratory quotient and Pcv-aCO2/Ca-cvO2 may have distinct behaviors. Studies performed in critically ill patients have shown controversial results regarding the ability of Pcv-aCO2/Ca-cvO2 to predict outcome, hyperlactatemia, microvascular abnormalities, and oxygen supply dependency. A randomized controlled trial also showed that Pcv-aCO2/Ca-cvO2 is useless as a goal of resuscitation. Pcv-aCO2/Ca-cvO2 should be carefully interpreted in critically ill patients.

Cánula nasal de alto flujo en lactantes: experiencia en una unidad de paciente crítico / High flow nasal cannula in infants: Experience in a critical patient unit

Introducción: La cánula nasal de alto flujo (CNAF) es un método de soporte respiratorio cada vez más utilizado en pediatría por sus resultados y seguridad. Objetivo: Determinar la efectividad de la CNAF, evaluar factores asociados a fracaso y complicaciones relacionadas con su uso en lactantes. Pacientes y método: Se analizaron los datos demográficos, clínicos, gasométricos, radiológicos y complicaciones de los pacientes conectados a CNAF en una unidad crítica entre junio de 2012 y septiembre de 2014. Se compararon los pacientes que fracasaron con los respondedores a CNAF, considerándose fracaso la necesidad de un mayor soporte respiratorio durante las primeras 48 h de conexión. Se utilizó test de Kolmogorov Smirnov, U de Mann-Whitney, Chi cuadrado, test exacto de Fisher, correlaciones y Modelo de regresión logística binaria para p ≤ 0,05. Resultados: Un total de 109 pacientes. Mediana de edad y peso: 1 mes (0,2-20 meses) y 3,7 kg (2-10 kg); percentil 95: 3,7 meses y 5,7 kg respectivamente. El diagnóstico y patrón radiológico más frecuente fue bronquiolitis (53,2%) e infiltrado intersticial (56%). Un 70,6% respondió. Hubo diferencia significativa entre fracaso y respuesta en el diagnóstico (p = 0,013), radiografía (p = 0,018), contexto de conexión (p < 0,0001), pCO2 (mediana 40,7 mm Hg [15,4-67 mm Hg] versus 47,3 mm Hg [28,6-71,3 mm Hg], p = 0,004) y horas de CNAF (mediana 60,75 h [5-621,5 h] versus 10,5 h [1-29 h], p < 0,0001). El OR de PCO2 ≥ 55 mm Hg para fracaso fue 2,97 (IC 95%: 1,08-8,17; p = 0,035). Ningún paciente falleció ni registró complicaciones. Conclusión: El porcentaje de éxito observado fue similar a lo publicado. En esta muestra el fracaso de CNAF solo se asoció a una pCO2 inicial ≥ 55 mm Hg. Su uso se consideró seguro al no reportarse complicaciones relacionadas a su utilización. Se requiere de un estudio multicéntrico, aleatorizado y controlado para contrastar estos resultados.

Introduction: The high flow nasal cannula (HFNC) is a method of respiratory support that is increasingly being used in paediatrics due to its results and safety. Objective: To determine the efficacy of HFNC, as well as to evaluate the factors related to its failure and complications associated with its use in infants. Patients and method: An analysis was performed on the demographic, clinical, blood gas, and radiological data, as well as the complications of patients connected to a HFNC in a critical care unit between June 2012 and September 2014. A comparison was made between the patients who failed and those who responded to HFNC. A failure was considered as the need for further respiratory support during the first 48 hours of connection. The Kolmogorov Smirnov, Mann-Whitney U, chi squared and the Exact Fisher test were used, as well as correlations and a binary logistic regression model for P ≤ .05. Results: The study included 109 patients, with a median age and weight: 1 month (0.2-20 months) and 3.7 kg (2-10 kg); 95 percentile: 3.7 months and 5.7 kg, respectively. The most frequent diagnosis and radiological pattern was bronchiolitis (53.2%) and interstitial infiltration (56%). Around 70.6% responded. There was a significant difference between failure and response in the diagnosis (P = .013), radiography (P = 018), connection context (P < .0001), pCO2 (median 40.7 mmHg [15.4-67 mmHg] versus 47.3 mmHg [28.6-71.3 mmHg], P = .004) and hours on HFNC (median 60.75 hrs [5-621.5 hrs] versus 10.5 hrs [1-29 hrs], P < .0001). The OR of the PCO2 ≥ 55 mmHg for failure was 2.97 (95% CI; 1.08-8.17; P = .035). No patient died and no complications were recorded. Conclusion: The percentage success observed was similar to that published. In this sample, the failure of HFNC was only associated with an initial pCO2 ≥ 55 mmHg. On there being no complications reported as regards it use, it is considered safe, although a randomised, controlled, multicentre study is required to compare and contrast these results.

Analysis of mean transcutaneous capnography in consecutive patients undergoing polysomnography / Análise da capnografia transcutânea média em indivíduos consecutivamente submetidos à polissonografia

Transcutaneous capnography is a noninvasive method useful for analysis of the behavioral tendency of transcutaneous CO2 pressure (PtcCO2) in patients undergoing polysomnography, to evaluate respiratory sleep disorders. Objective Determine normative PtcCO2 values in normal patients undergoing polysomnography. Method One hundred seventy-nine patients who underwent polysomnography with simultaneous PtcCO2 measurement were assessed by means of a transcutaneous capnograph (TCM4 series from Radiomiter). Results The group classified as normal (N=53) presented a apnea/hypopnea index (AHI) <5 events/per hour of sleep and their age groups varied between 7 and 76 years of age. Conclusion Global mean values of PtcCO2 in the normal group had a Gaussian distribution that varied between 33.1 and 50.0 mmHg (SD 4,363). Such findings allowed the establishment of normative PtcCO2 values for normal individuals. .

A capnografia transcutânea é um método não invasivo útil para análise da tendência comportamental da pressão de CO2 transcutânea (PtcCO2)1,2,3 em pacientes submetidos à polissonografia para análise de transtornos respiratórios do sono. Objetivo Determinar valores normativos da PtcCO2 em pacientes normais submetidos à polissonografia. Método Foram analisados 179 pacientes submetidos à polissonografia com medida concomitante da PtcCO2 através de um capnógrafo transcutâneo. Resultados O grupo classificado como normal (N=53) apresentou índice de apnéia/hipopnéia (AIH) <5 eventos/hora de sono e faixa etária variando de 7 a 76 anos. Conclusão Os valores da média global da PtcCO2 no grupo normal apresentaram distribuição gaussiana variando de 33,1 a 50,0 mmHg (DP 4.363). Tais achados permitiram a criação de valores normativos da PtcCO2 para indivíduos normais. .

Análisis de factores relacionados con hipercapnia crónica en la distrofia miotónica / Analysis of factors associated with chronic hypercapnia in patients with myotonic dystrophy

La distrofia miotónica (DM) es la distrofia muscular más común en adultos. Diversos factores pueden explicar la retención crónica de CO2. La selección de pacientes, diferentes estadios evolutivos y formas de evaluación, pueden explicar los resultados disímiles al respecto. Nuestros objetivos fueron caracterizar la función respiratoria y analizar los factores relacionados con la retención crónica de CO2 en la DM. Se incluyeron 27 pacientes ambulatorios consecutivos, estables clínicamente y se los agrupó como normocápnicos e hipercápnicos (PaCO2 ≥ 43 mm Hg). Se determinaron capacidad vital forzada (FVC), presiones estáticas máximas, tiempo de apnea voluntaria, escala de Epworth y gases arteriales. La quimiosensibilidad al CO2 se evaluó mediante la reinhalación de CO2 (método de Read). La pendiente ∆P0.1/∆PCO2 expresa la quimiosensibilidad al CO2. El 59.3% tenían hipercapnia. La FVC y la fuerza muscular respiratoria fueron normales o mostraron disminución leve a moderada, sin diferencias significativas en ambos grupos. La inadecuada respuesta al CO2 (pendientes ∆P0.1/∆PCO2 bajas (< 0.1 cmH2O/mm Hg) o planas) se asoció con hipercapnia (p < 0.005) y ésta significó un riesgo 11.6 veces mayor de inadecuada respuesta al CO2. El grupo con pendiente ∆P0.1/∆PCO2 baja-plana mostró mayor PaCO2 (p = 0.0017) y tiempo de apnea voluntaria más prolongado (p = 0.002). Concluimos que, en nuestros pacientes con DM, la hipercapnia crónica se asoció a la presencia de anomalías del control central de la respiración. Estos resultados permiten explicar los informes previos que describen la llamativa ocurrencia de insuficiencia respiratoria postoperatoria y las dificultades en el proceso de desvinculación de asistencia ventilatoria mecánica en estos pacientes.

Myotonic dystrophy (DM) is the most common dystrophy in adults. Several factors may explain the chronic CO2 retention. The selection of patients, different clinical stages and evaluation forms may explain the differing results obtained. Our objectives were to characterize respiratory function and to evaluate factors associated with chronic retention of CO2 in DM. We included 27 consecutive ambulatory and stable patients who were allocated into normocapnic and hypercapnic groups (PaCO2 ≥ 43 mmHg). Forced vital capacity (FVC), maximum static pressure, voluntary apnea time, Epworth scale and arterial blood gases were measured. The CO2 chemosensitivity was assessed using CO2 rebreathing (Read method). The slope ΔP0.1/ΔPCO2 expressed the CO2 chemosensitivity. A 59.3% (16/27) presented hypercapnia. FVC and respiratory muscle strength were normal or showed mild to moderate decrease. No significant differences in these variables were found in both groups. Inadequate response to CO2 (slope ΔP0.1/ΔPCO2 low (< 0.1 cm H2O/mmHg) or flat) was associated with hypercapnia (p < 0.005). Chronic retention of CO2 represented 11.56 times higher risk of inadequate response to CO2. The group with low-flat slope ΔP0.1/ΔPCO2 showed higher PaCO2 (p = 0.0017) and more prolonged voluntary apnea time (p = 0.002). We conclude that in our patients with DM, chronic CO2 retention was associated with the presence of abnormalities of the central control of breathing. Our results allow explaining previous reports describing the striking frequency of postoperative respiratory failure and difficulties in the process of weaning from mechanical ventilation.

Diferencia veno-arterial de dióxido de carbono como predictor de gasto cardiaco disminuido en modelo pediátrico experimental / Veno-arterial difference of carbondioxide as a predictor of low cardiac output in an experimental pediatric model

Background: Cardiac output (CO) measurement is not a standard of care for critically ill children, but it can be estimated by indirect methods such as veno-arterial pCO2 difference (ΔVACO2). Aim: To determine the correlation between CO and ΔVACO2 and evaluate the usefulness of ΔVACO2 in the diagnosis of low CO in an experimental pediatric model. Materials and Methods: Thirty piglets weighing 4.8 ± 0.35 kg were anesthetized and monitored with transpulmonary thermodilution. Lung injury was induced with tracheal instillation of Tween 20®. Serial measurements of central venous and arterial blood gases, as well as CO, were obtained at baseline, 1, 2 and 4 h after lung injury induction. Low cardiac output (LCO) was defined as CO lower than 2.5 Llminlm². Results: There was an inverse correlation between CO and ΔVACO2 (r = -0.36, p < 0.01). ΔVACO2 was 14 ± 8 mmHg in LCO state and 8 ± 6 mmHg when this condition was not present (p < 0.01). Area under the receiver operating characteristic (ROC) curves of ΔVACO2 and LCO state was 0.78 (0.68-0.86). The best cut-point was 8.9 mmHg to determine LCO with a sensibility 0.78, specificity 0.7, positive predictive value 0.27 and negative predictive value 0.96. Conclusions: In this model there was an inverse correlation between ΔVACO2 and CO. The best cutoff value to discard LCO was ΔVACO2 of 8.9 mmHg, indicating that under this value the presence of LCO is very unlikely.

Sudden decrease in end-tidal carbon-dioxide in a neonate undergoing surgery for type B interrupted aortic arch.

Interruption of the aortic arch is a rare anomaly affecting 1% of children with congenital heart disease. The systemic circulation is ductal dependent and is determined principally by the ratio of the resistances in the systemic and the pulmonary vascular bed. Any increase in the pulmonary vascular resistance may increase the dead space ventilation due to acute pulmonary hypoperfusion. We report a case where sudden decreases in the end-tidal carbon-dioxide due to pulmonary hypoperfusion mimicked accidental endotracheal tube extubation in an infant undergoing repair of interrupted aortic arch.

Near-fatal pulmonary embolism in an experimental model: hemodynamic, gasometric and capnographic variables / Embolia pulmonar quase fatal, um modelo experimental: variáveis hemodinâmicas, gasométricas e capnográficas

INTRODUCTION: Experimental studies on pulmonary embolism (PE) are usually performed under mechanical ventilation. Most patients with suspicion of PE enter the Emergency Services in spontaneous breathing and environmental air. Thus, under these conditions, measurements of hemodynamic, gasometric and capnographic variables contribute largely to a more specific comprehension of cardiopulmonary and gasometric alterations in the acute phase of the disease. Studies which evaluated animals under conditions are lacking. OBJECTIVE: This study aimed to submit animals under spontaneous ventilation and without supplemental oxygen to PE. METHODS: PE was induced in six pigs using autologous blood clots, and cardiorespiratory and gasometric records were performed before and after PE. The values of "near fatal" mean pulmonary arterial pressure (MPAP) were previously determined. RESULTS: The presence of obstructive shock could be evidenced by increased MPAP (from 17.8±3.5 to 41.7±3.3 mmHg) (P<0.0001) and decreased cardiac output (from 4.9±1.0 to 2.7±1.0 L/min) (P<0.003). Consequently, metabolic acidosis occurred (Lac art) (from 2.4±0.6 to 5.7±1.8 mmol/L)(P<0.0001). It was observed hypoxemia (from 73.5±12.7 to 40.3±4.6 mmHg) (P<0.0001); however, PaCO2 did not vary (from 44.9±4.4 to 48.2±6.0 mmHg) (NS). There were significant increases in both P(a-et)CO2 (from 4.8±2.8 to 37.2±5.8 mmHg) and P(A-a)O2 (from 8.2±8.9 to 37.2±10.3 mmHg) (both P<0.0001). There was also a significant increase in the total alveolar minute volume (from 4.0±0.9 to 10.6±2.9 L/min) (P<0.0001). CONCLUSIONS: In this model, the near fatal MPAP was from 2 to 2.5 times the basal MPAP; and the capnographic variables, associated with arterial and venous gasometry, showed effective in discriminating an acute obstructive profile.

INTRODUÇÃO: Estudos experimentais de embolia pulmonar (EP) são habitualmente realizados sob ventilação mecânica. A maioria dos pacientes com suspeita de EP adentra os Serviços de Emergência em respiração espontânea e em ar ambiente. Assim, medidas das variáveis hemodinâmicas, gasométricas e capnográficas, nessas condições, em muito contribuiriam para compreensão mais específica das alterações cardiopulmonares e gasométricas na fase aguda da doença. Dessa forma, faltam estudos experimentais que avaliem animais em tais condições. OBJETIVO: O objetivo do presente estudo foi submeter à EP animais sob ventilação espontânea e sem oxigênio suplementar. MÉTODOS: A EP por coágulos autólogos foi induzida em seis porcos e os registros cardiorrespiratórios e gasométricos foram realizados no pré e pós-EP. O valor da pressão média de artéria pulmonar (PMAP) "quase fatal" foi previamente determinada. RESULTADOS: A presença de choque obstrutivo agudo pôde ser evidenciada pelo aumento da PMAP (de 17.8±3.5 para 41.7±3.3 mmHg) (P<0.0001) e pela queda do débito cardíaco (de 4.9±1.0 para 2.7±1.0 L/min) (P<0.003). Consequentemente, a presença de acidose metabólica pode ser constatada (de 2.4±0.6 para 5.7±1.8 mmol/L) (P<0.0001). Observou-se, ainda, hipoxemia (de 73.5±12.7 para 40.3±4.6 mmHg) (P<0.0001), porém, a PaCO2 não variou (de 44.9±4.4 para 48.2±6.0 mmHg) (NS). Houve expressivos aumentos, tanto para P(a-et)CO2 (de 4.8±2.8 para 37.2±5.8 mmHg) quanto para a P(A-a)O2 (de 8.2±8.9 para 37.2±10.3 mmHg) (P<0.0001). Ocorreu, também, significativo aumento do volume minuto alveolar total (de 4.0±0.9 para 10.6±2.9 L/min) (P<0.0001). CONCLUSÕES: Nesse modelo, a PMAP quase fatal foi de 2 a 2,5 vezes a PMAP basal e as variáveis capnográficas, associadas a gasometria arterial e venosa, mostraram-se eficazes em discriminar um quadro obstrutivo agudo.

Influence of Diaphragmatic Mobility on Hypercapnia in Patients with Chronic Obstructive Pulmonary Disease

A reduction in diaphragm mobility has been identified in patients with chronic obstructive pulmonary disease (COPD) and has been associated with a decline in pulmonary function parameters. However, little information exists regarding the potential role of diaphragm mobility on hypercapnia in COPD. A new method of assessing the mobility of the diaphragm, using ultrasound, has recently been validated. The purpose of the present study was to investigate the relationship between diaphragm mobility and pulmonary function parameters, as well as that between arterial blood gas values and diaphragm mobility, in COPD patients. Thirty seven COPD patients were recruited for pulmonary function test, arterial blood gas analysis and diaphragm mobility using ultrasound to measure the craniocaudal displacement of the left branch of the portal vein. There were significant negative correlations between diaphragmatic mobility and PaCO2 (r = -0.373, P = 0.030). Diaphragmatic mobility correlated with airway obstruction (FEV1, r = 0.415, P = 0.011) and with ventilatory capacity (FVC, r = 0.302, P = 0.029; MVV, r = 0.481, P = 0.003). Diaphragmatic mobility also correlated significantly with pulmonary hyperinflation. No relationship was observed between diaphragm mobility and PaO2 (r = -0.028, P = 0.873). These findings support a possibility that the reduction in diaphragm mobility relates to hypercapnia in COPD patients.

Comparison and agreement between venous and arterial gas analysis in cardiopulmonary patients in Kashmir valley of the Indian subcontinent

Arterial blood gas [ABG] analysis is routinely performed for sick patients but is fraught with complications, is painful, and is technically demanding. To ascertain agreement between the arterial and peripheral venous measurement of pH, pCO[2], pO[2], and bicarbonate levels in sick patients with cardiopulmonary disorders in the valley of Kashmir in the Indian subcontinent, so as to use venous gas analysis instead of arterial for assessment of patients. Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Kashmir, a 650-bedded tertiary care hospital in North India located at an altitude of 1584 m. One hundred patients who required ABG analysis were admitted. Peripheral venous blood was drawn within 5 min of an ABG measurement, and the samples analyzed immediately on a point of care automated ABG analyzer. Finger pulse oximetry was used to obtain oxygen [SpO[2]] saturation. Data were analyzed using Pearson correlation and bias [Bland Altman] methods. The venous measurements of pH, pCO[2], pO[2] and bicarbonate, and the digital oxygen saturation were highly correlated with their corresponding arterial measurements. Bland Altman plots demonstrated a high degree of agreement between the two corresponding sets of measurements with clinically acceptable differences. The difference in pO[2] measurements was, however, higher [-22.34 +/- 15.23] although the arterial saturation and finger oximetry revealed a good degree of agreement with clinically acceptable bias. Peripheral venous blood gas assessment in conjunction with finger pulse oximetry can obviate the routine use of arterial puncture in patients requiring ABG analysis

Analysis of sleep characteristics in post-polio syndrome patients / Análise das características do sono em pacientes com síndrome pós-poliomielite

The main post-polio syndrome (PPS) symptoms are new weakness, new atrophy, fatigue, pain and sleep disturbances. Polysomnography is the gold standard for sleep analysis. OBJECTIVE: To analyze sleep patterns in PPS patients. METHOD: Sixty patients (mean age 46.8±11.3 years) at the Federal University of São Paulo (UNIFESP/EPM) complaining of sleep disturbances were evaluated by means of polysomnography, performed at the Sleep Institute. RESULTS: Sleep efficiency was lower due to high sleep latency and arousal index. The apnea and hypopnea index (AHI) and the periodic limb movements (PLM) index were higher. Sleep architecture was also impaired. There were no abnormalities of oxygen saturation, carbon dioxide levels, respiratory rate or heart rate. CONCLUSION: New post-polio sleep disturbances were isolated symptoms. It appears that these symptoms were not due to post-polio features, but rather, that they were due to dysfunction of the surviving motor neurons in the brainstem. Abnormal dopamine production, which is responsible for many sleep-related breathing disorders and abnormal movements, may also have been implicated in the present findings.

Dentre as manifestações clínicas da síndrome pós poliomielite (SPP) destacam-se nova fraqueza, fadiga, dor, nova atrofia e transtornos do sono. A polissonografia de noite inteira permanece sendo padrão ouro para análise do sono e diagnóstico de transtornos do sono. OBJETIVO: Verificar os transtornos de sono nos pacientes com SPP. MÉTODO: 60 pacientes com SPP (media de idade 46,8±11,3 anos), da UNIFESP/EPM,que apresentavam queixas sobre sono realizaram uma noite de polissonografia no Instituto do Sono. RESULTADOS: A eficiência do sono é diminuída em decorrência do aumento da latência do sono e do índice de despertar. O índice de apnéia e hipopnéia (IAH) e o índice de movimentos periódicos dos membros (iPLM) estão aumentados. A arquitetura do sono é prejudicada por essas alterações. Não há alterações da saturação da oxi-hemoglobina, do gás carbônico exalado, da freqüência respiratória e cardíaca. CONCLUSÃO: Novas alterações do sono são sintomas isolados desta população. Parece que esses sintomas não ocorrem devido a outras características da SPP, mas decorrem de disfunções nos neurônios do tronco encefálico e alterações da produção de dopamina que provocam os distúrbios respiratórios do sono e os movimentos periódicos dos membros.

Clinical Meaning of Early Oxygenation Improvement in Severe Acute Respiratory Distress Syndrome under Prolonged Prone Positioning

BACKGROUND/AIMS: Ventilating patients with acute respiratory distress syndrome (ARDS) in the prone position has been shown to improve arterial oxygenation, but prolonged prone positioning frequently requires continuous deep sedation, which may be harmful to patients. We evaluated the meaning of early gas exchange in patients with severe ARDS under prolonged (> or = 12 hours) prone positioning. METHODS: We retrospectively studied 96 patients (mean age, 60.1 +/- 15.6 years; 75% men) with severe ARDS (PaO2/FiO2 or = 20 mmHg and decreases in PaCO2 of > or = 1 mmHg, respectively, 8 to 12 hours after first placement in the prone position. RESULTS: The mean duration of prone positioning was 78.5 +/- 61.2 hours, and the 28-day mortality rate after MICU admission was 56.3%. No significant difference in clinical characteristics was observed between PaO2 and PaCO2 responders and non-responders. The PaO2 responders after prone positioning showed an improved 28-day outcome, compared with non-responders by Kaplan-Meier survival estimates (p < 0.05 by the log-rank test), but the PaCO2 responders did not. CONCLUSIONS: Our results suggest that the early oxygenation improvement after prone positioning might be associated with an improved 28-day outcome and may be an indicator to maintain prolonged prone positioning in patients with severe ARDS.

Alteraciones del intercambio gaseoso durantre la ventilación mecánica en neurología prolongada / Gas exchange alterations during mechanical ventilation in prolonged neurosurgery

El objetivo de este estudio fue determinar si los suspiros manuales o automáticos de la máquina de anestesia reducen las alteraciones del intercambio gaseoso durante la anestesia para neurocirugía prolongada. Metodología: Se realizó un estudio prospectivo, randomizado, de 27 pacientes neuroquirúrgicos, operados con anestesia general y ventilación controlada, con fracción inspirada de oxígeno (FIO2) de 1, sin presiónpositiva de final de espiración (PEEP). Los pacientes fueron aleatoriamente asignados a 3 grupos: Grupo control (C): volumen corriente (VC) 10 ml/kg y frecuencia respiratoria (FR) 10/min; Grupo SM: VC y FR igual, más 3 insufl aciones manuales horarias, y Grupo SA: igual VC y FR, con suspiro automático de la máquina de anestesia. Se realizaron gasometrías arteriales basales, a los 30, 120, 240 y 360 minutos de la intubación traqueal, y a las 2 horas del ingreso a Sala de Recuperación Postanestésica (SRPA). Resultados: Se calcularon los siguientes índices: presión arterial de oxígeno/fracción inspirada de oxígeno (PaFIO2), presión arterial/presión alveolar de oxígeno (PaO2/PAO2), y diferencia alvéolo – arterial de oxígeno(DA-a O2). El PaFIO2 no tuvo modificaciones significativas, mientras que el índice PaO2/PAO2 tuvo un descenso y la DA-a O2 un aumento significativo (p < 0,05) con respecto a los valores basales durante la anestesia, con recuperación parcial en SRPA. No se encontraron diferencias significativas entre los 3 grupos estudiados. Conclusiones: Durante la anestesia prolongada con ventilación mecánica controlada con FIO2 1 se produjeron alteraciones del intercambio gaseoso que no disminuyeron mediante la administración de suspiros manuales ni automáticos de la máquina de anestesia.

The objective of this study was to determine if manual or automatic anesthesia machine sights can reduce gas exchange alterations during prolonged neurosurgery under general anesthesia. Methodology: We made a prospective, randomized, controlled research on 27 neurosurgical patients, who had been operated under general anesthesia, and controlled mechanical ventilation with fraction of inspired oxygen of 1 (FIO2), without positive end expiratory pressure (PEEP). Patients were randomized into 3 groups; Group C: tidal volume (VT) 10 ml/kg, and respiratory frequency (RF) of 10/min; Group SM: same VT and RF, plus 3 manual inflations per hour; and Group SA: same VT and RF, with automatic sigh of anesthesia machine. Basal arterial blood gases were determined; 30, 120, 240 and 360 minutes after tracheal intubation, and 2hours after arriving to the Post Anesthesia Care Unit (PACU). Results: The following ratios were calculated: arterial oxygen pressure/fraction of inspired oxygen (PaFIO2), arterial oxygen pressure/alveolar oxygen pressure (PaO2/PAO2), and the difference between alveolar oxygen pressure - arterial oxygen pressure (DAaO2). The PaFIO2 did not have significant modifications, while the PaO2/PAO2 index had a reduction and the DA-aO2 had a significant increase (p < 0,05) with respect to the basal values during anesthesia, with partial recovery in PACU. We didn’t found differences between the three groups studied. Conclusions: During prolonged anesthesia with controlled mechanical ventilation with FIO2 1 gas exchange alterations took place, and they were not modified by the administration of manual inflations or automatic sighs of the anesthesia machine.

Performance Evaluation of the Piccolo xpress Point-of-care Chemistry Analyzer / 대한진단검사의학회지

BACKGROUND: Point-of-care (POC) tests are used increasingly due to fast results and simple test procedures, which enables rapid diagnosis and therapeutic monitoring. We evaluated the performance of the Piccolo xpress Chemistry Analyzer (Abaxis, USA) a POC chemistry analyzer. METHODS: Fourteen analytes, Na+, K+, Cl-, Ca2+, total carbon dioxide, AST, ALT, total bilirubin, alkaline phosphatase, blood urea nitrogen, creatinine, albumin, total protein, and glucose; were measured simultaneously with a 100 microliter of whole blood sample using a Comprehensive Metabolic Reagent disk. Within-run and total precision and linearity were evaluated according to CLSI EP15-A and EP6-A guidelines, respectively. Comparison with a central laboratory chemistry analyzer was performed using 144 patient samples. RESULTS: The coefficients of variations of within-run and total precision were all within 5% for three levels except for total carbon dioxide, ALT, alkaline phosphatase, total bilirubin, and creatinine in low level, and creatinine in middle level. The results of 14 analytes were linear within a commonly encountered range in clinical samples (r2> or =0.98). More than 10% of samples in Na+, AST, ALT, glucose, BUN did not satisfy CLIA analytical quality requirement. CONCLUSIONS: The Piccolo xpress Chemistry Analyzer can analyze multiple analytes with a minimal amount of whole blood in a short time. It showed an acceptable performance for precision, linearity and comparison with central laboratory analyzer. It can be useful as a screening tests modality in mobile clinics, ambulances, and field clinics for military use, and for pediatric patients from whom enough sample volume is difficult to obtain.

Avaliação de oxigenador de membrana infantil em ovinos / Evaluation of infant membrane oxygenator in sheep

OBJETIVO: Analisar a segurança e a eficácia de um novo oxigenador de membrana denominado OXM -1500. MÉTODOS: No período de maio de 2005 a setembro de 2006, foram estudados seis ovinos da raça Santa Inês, sendo cinco machos e uma fêmea, com peso corpóreo médio de 14,1 (±5) kg, superfície corpórea de 0,6 (±0,2) m² e idade média de 3,8 (±1,5) meses. Todos foram submetidos a circulação extracorpórea (CEC) com avaliação nos tempos 10, 30, 60, 120, 180 e 240 minutos, obtendo-se os valores de taxa de transferência de oxigênio (TTO2) e de taxa de transferência de gás carbônico (TTCO2), hemoglobina sérica (HBS) e livre (HBL), plaquetometria, leucometria e taxa de transferência de calor. RESULTADOS: Houve adequadas TTO2 e TTCO2. A lesão da maioria dos elementos figurados do sangue foi insignificante, sem alterações dos níveis de HBS, HBL, plaquetas e o número de leucócitos diminuíram com o tempo. A troca de calor foi efetiva (p < 0,05). CONCLUSÃO: O oxigenador de membrana infantil OXM1500, testado em ovinos, mostrou-se com capacidade adequada de oxigenação, remoção de gás carbônico e pequena alteração da hemoglobina e plaquetas, com diminuição do número de leucócitos de forma esperada. O trocador de calor acoplado ao oxigenador foi eficaz nas variações de temperatura.

OBJECTIVE: To analyze the security and efficacy of a new membrane oxygenator, the so-called OXM - 1500. METHODS: From May 2005 to September 2006, six sheep of Santa Inês breed (five male and one female, respectively) were studied. The average body weight was 14.1 (±5) kg, body surface 0.6 (±0.2) m² and a mean age 3.8 (±1.5) months. All of them were submitted to extracorporeal circulation (CEC) with evaluation at 10, 30, 60, 120, 180 and 240 minutes. The following values were obtained: values of oxygen transference (TTO2) and carbon dioxide transference (TTCO2), haemoglobin (HBS) and free haemoglobin (HBL), the score of platelets and of leucocytes, and heat transference rate. RESULTS: TTO2 and TTCO2 were adequate. Lesion of the majority formed blood elements was insignificant; there no modifications in HBS, HBL levels; platelets and leucocytes decreased over time. Heat exchange was effective (p < 0.05). CONCLUSIONS: The membrane OXM - 1500 infant oxygenator, tested in sheep, showed adequate oxygenation capacity, CO2 removal capacity, and small alteration of haemoglobin and platelets without significant decrease of leucocytes, as expected. Heat exchanger connected to the oxygenator was efficient in temperature changes.