Sevoflurane anesthesia deteriorates pulmonary surfactant promoting alveolar collapse in male Sprague-Dawley rats.

General anesthesia is frequently associated to transient hypoxemia and lung atelectasis. Although volatile anesthetics are safe and widely used, their potential role on anesthesia-induced pulmonary impairment has not been fully explored. In this study, we investigated the effect of volatile anesthetic sevoflurane on pulmonary surfactant composition and structure that could contribute to atelectasis. After 30 min of sevoflurane anesthesia, Sprague-Dawley rats showed increased levels of lyso-phosphatidylcholine and decreased levels of phosphatidylcholine associated with significant impairment in lung mechanics and alveolar collapse, but showed no deterioration of alveolar fluid reabsorption when compared to control group of rats anesthetized with pentobarbital. Exposure to sevoflurane altered the thermotropic profile of surfactant model membranes, as detected by fluorescence anisotropy. In this sense, sevoflurane-promoted fluidification of condensed phases could potentially impair the ability of surfactant films to sustain the lowest surface tensions. In conclusion, the observed changes in surfactant composition and viscosity properties suggest a direct effect of sevoflurane on surfactant function, a factor potentially involved in anesthetic-induced alterations in lung mechanics.

Adenosine triphosphate-dependent calcium signaling during ventilator-induced lung injury is amplified by hypercapnia.

Adenosine triphosphate (ATP) is released by alveolar epithelial cells during ventilator-induced lung injury (VILI) and regulates fluid transport across epithelia. High CO(2) levels are observed in patients with "permissive hypercapnia," which inhibits alveolar fluid reabsorption (AFR) in alveolar epithelial cells. The authors set out to determine whether VILI affects AFR and whether the purinergic pathway is modulated in cells exposed to hypercapnia. Control group was compared against VILI (tidal volume [Vt] = 35 mL/kg, zero positive end-expiratory pressure [PEEP]) and protective ventilation (Vt = 6 mL/kg, PEEP = 10 cm H(2)O) groups. Lung mechanics, histology, and AFR were evaluated. Alveolar epithelial cells (AECs) were loaded with Fura 2-AM to measure intracellular calcium in the presence ATP (10 µM) at 5% or 10% CO(2) as compared with baseline. High tidal volume ventilation impairs lung mechanics and AFR. Hypercapnia (HC) increases intracellular calcium levels in response to ATP stimulation. HC + ATP is the most detrimental combination decreasing AFR. Purinergic signaling in AECs is modulated by high CO(2) levels via increased cytosolic calcium. The authors reason that this modulation may play a role in the impairment of alveolar epithelial functions induced by hypercapnia.

[Salbutamol improves diaphragmatic contractility in chronic airway obstruction]. / El salbutamol mejora la contractilidad diafragmática en la obstrucción crónica de la vía aérea.

INTRODUCTION: Chronic airflow obstruction in conditions such as chronic obstructive pulmonary disease is associated with respiratory muscle dysfunction. Our aim was to study the effects of salbutamol-a beta-adrenergic agonist known to improve muscle strength in physiologic and pathologic conditions-on diaphragm contractility in an animal model of chronic airway obstruction achieved by tracheal banding. MATERIALS AND METHODS: Twenty-four Sprague-Dawley rats were randomized into a control group and 3 tracheal banding groups, 1 that received acute salbutamol treatment, 1 that received chronic salbutamol treatment, and 1 that received nothing. Arterial blood gases, acid-base balance, and in vitro diaphragmatic contractility were evaluated by measuring peak twitch tension, contraction time, contraction velocity, half-relaxation time, relaxation velocity, and force-frequency curves. RESULTS: The 3 study groups had significantly reduced arterial pH and increased PaCO2 and bicarbonate levels compared to the control group (P<.05). The untreated tracheal banding group had significantly reduced peak twitch tension and contraction velocity, and a significantly lower force-frequency curve in comparison with the other groups (P<.05). The chronic treatment group had a higher relaxation velocity than the untreated study group (P<.05). The mean (SE) peak twitch tension values were 6.46 (0.90)N/cm(2) for the control group, 3.28 (0.55)N/cm(2) for the untreated tracheal banding group, 6.18 (0.71)N/cm(2) for the acute treatment group, and 7.09 (0.59)N/cm(2) for the chronic treatment group. CONCLUSIONS: Diaphragmatic dysfunction associated with chronic airflow obstruction improves with both the acute and chronic administration of salbutamol. The mechanisms involved in respiratory muscle dysfunction warrant further study.

[Salbutamol improves diaphragm force generation in experimental sepsis]. / El salbutamol mejora la fuerza diafragmática en la sepsis experimental.

OBJECTIVE: In a high percentage of cases, severe sepsis is accompanied by acute respiratory failure, in which weakness of the respiratory muscles plays an important role. Weakened respiratory muscles that are subjected to an increased mechanical load may develop muscle fatigue, with exacerbation of the respiratory failure. Because beta2-adrenergic drugs increase muscle contraction force, they may play a role in preventing and managing respiratory failure in septic patients. Our aim was to study the effects of salbutamol on diaphragm function in an animal model of peritoneal sepsis. MATERIAL AND METHODS: The study included 3 groups of animals: a) a control group (n=7), in which the animals underwent a median laparotomy without visceral manipulation; b) a septic group (n=10), in which peritoneal sepsis was induced by cecal ligation and puncture (CLP); and c) a salbutamol group (n=7), in which peritoneal sepsis (CLP) was treated with salbutamol. Hemodynamic parameters and blood gases were measured in vivo. Diaphragm function was evaluated in vitro. RESULTS: Salbutamol increased aortic blood flow and heart rate while it reduced mean arterial pressure in the animals with peritoneal sepsis (P< .05). Sepsis produced a significant drop in diaphragmatic force both before and after the application of a muscle-fatigue protocol. Treatment with salbutamol improved muscle contraction force before and after application of the protocol (P< .05). CONCLUSIONS: The use of beta2-adrenergic drugs such as salbutamol improves diaphragm function in experimental sepsis. The mechanisms that produce this improvement require further study.

[Physiologic effects of noninvasive ventilation in patients with chronic obstructive pulmonary disease]. / Efectos fisiológicos de la ventilación no invasiva en pacientes con EPOC.

OBJECTIVE: Noninvasive mechanical ventilation has been of use in the treatment of some forms of chronic and acute respiratory failure. However, the benefits of its use in patients in the stable phase of severe chronic obstructive pulmonary disease (COPD) remain unclear. A combination of continuous positive airway pressure (CPAP) and pressure support ventilation (PSV) may improve respiratory mechanics and alveolar ventilation, and reduce inspiratory muscle effort. In this study, we analyzed the physiologic effects of differing levels of CPAP and CPAP plus PSV in patients with stable severe COPD. PATIENTS AND METHODS: Work of breathing, breathing pattern, oxygen saturation measured by pulse oximetry, PaO2, and PaCO2 were analyzed in a group of 18 patients under the following conditions: a) baseline; b) CPAP, 3 cm H20; c) CPAP, 6 cm H20; d) CPAP 3 cm H20 plus PSV 8 cm H20; and e) CPAP 3 cm H20 plus PSV 12 cm H20. RESULTS: CPAP at pressures of 3 and 6 cm H20 was associated with an increase in tidal volume (VT) from a mean (SD) baseline value of 0.52 (0.04) L to 0.62 (0.04) and 0.61 (0.03) L, respectively. Minute ventilation increased from 8.6 (0.5) L/min to 10.8 (0.6) and 10.9 (0.5) L/min, respectively. Mean inspiratory flow (VT/Ti) increased from 0.35 (0.02) L/s to 0.44 (0.02) and 0.41 (0.02) L/s, respectively, and dynamic intrinsic positive end-expiratory pressure (PEEPi,dyn) was reduced from 1.63 (0.7) cm H20 to 1.1 (0.06) and 0.37 (0.4) cm H20, respectively. CPAP did not reduce the work of breathing. Association of CPAP at 3 cm H20 with PSV of 8 or 12 cm H20 increased VT to 0.72 (0.07) and 0.87 (0.08) L, respectively, while minute ventilation increased to 12.9 (0.8) and 14.9 (1.1) L/s, respectively. Mean inspiratory flow also increased to 0.50 (0.03) and 0.57 (0.03) L/s, respectively. Work of breathing was reduced from 0.90 (0.01) J/L to 0.48 (0.06) and 0.30 (0.06) J/L, respectively, while PEEPi,dyn increased to 1.30 (0.02) and 2.42 (0.08) cm H20, respectively. With combined CPAP of 3 cm H20 and PSV of 12 cm H20, PaCO2 was reduced from a baseline value of 41.2 (1.5) mm Hg to 38.7 (1.9) mm Hg. All of the changes were statistically significant (P< .05). CONCLUSIONS: CPAP of 3 cm H20 in combination with PSV improved breathing pattern, increased alveolar ventilation, and reduced work of breathing. These results offer a rational basis for the use of noninvasive mechanical ventilation in the treatment of patients with stable severe COPD.

Ventilación con presión positiva no invasiva en la insuficiencia respiratoria aguda / Non invasive positive pressure ventilation in acute respiratory failure

Trabajos recientes sugieren que la ventilación con presión positiva no invasiva (VPPNI) puede ser útil en el tratamiento de la insuficiencia respiratoria aguda (IRA). Sin embargo, no está definida su eficacia ni qué parámetros son útiles para predecir su éxito-fracaso. Con estos objetivos se estudiaron 14 pacientes con IRA (PaO2 61,2 ñ 3,2 con MFL) de causa diversa, tratados con VPPNI (equipo BIPAP-Respironics) (IPAP:9,9 ñ 0,6 cmH20, EPAP: 5 cmH20) Se midió frecuencia respiratoria (FR), frecuencia cardíaca y gases respiratorios en: 1) situación basal (BL); 2) a la hora de VPPNI (T1) y 3) a las 20 horas de VPPNI (T2). Durante la VPPNI se observó incremento de la Pa02 (BL, 61,2ñ 3,2 mmHg; T1, 87ñ 8 mmHg [p<0,05] ; y T2 104 ñ 11 mmHg [p

Ventilación con presión positiva no invasiva en la insuficiencia respiratoria aguda / Non invasive positive pressure ventilation in acute respiratory failure

Trabajos recientes sugieren que la ventilación con presión positiva no invasiva (VPPNI) puede ser útil en el tratamiento de la insuficiencia respiratoria aguda (IRA). Sin embargo, no está definida su eficacia ni qué parámetros son útiles para predecir su éxito-fracaso. Con estos objetivos se estudiaron 14 pacientes con IRA (PaO2 61,2 ñ 3,2 con MFL) de causa diversa, tratados con VPPNI (equipo BIPAP-Respironics) (IPAP:9,9 ñ 0,6 cmH20, EPAP: 5 cmH20) Se midió frecuencia respiratoria (FR), frecuencia cardíaca y gases respiratorios en: 1) situación basal (BL); 2) a la hora de VPPNI (T1) y 3) a las 20 horas de VPPNI (T2). Durante la VPPNI se observó incremento de la Pa02 (BL, 61,2ñ 3,2 mmHg; T1, 87ñ 8 mmHg [p<0,05] ; y T2 104 ñ 11 mmHg [p

Nuevos aspectos del estudio del control de la respiración / New aspects of the study of respiration control

La introducción de nuevos métodos no invasivos de estudio del sistema de control de la respiración, ha permitido una mejor comprensión de distintos estados fisiopatológicos. Se describen las bases teóricas y la aplicación prática de dos ellos: la presión de oclusión bucal (P0.1) y el análisis del ciclo respiratorio. Se muestran resultados preliminares de pacientes asmáticos y obesos con apnea del sueño

Anestesia con ventilación unilateral selectiva: efecto de la insuflación de oxigenio con presion positiva continua en el pulmon no ventilado / Selective unilateral ventilation anesthesia: effect of the continous positive pressure oxigen insufflation

Se estudió el intercambio gaseoso y el equilibrio ácido-base de 15 pacientes, en los que se realizó ventilación unilateral selectiva (VUP) e insuflación de oxígeno con presión positiva continua de cinco (PPCVA5) y diez centímetros de agua (PPCVA10). En ocho casos se aplicó PPCVA5 y en 12 caso PPCVA10 (seis de ellos después de 20 minutos de PPCVA5). Durante la VUP los valores promedio de pa02, Dif. A-a02 y shunt, fueron 218 + ou - 72 mmHg, 458 + ou - 71 mmHg y 18 + ou - 2.1% respectivamente. Con PPCVA, pasaron a 251 + ou - 54 mmHg, 420 + ou - 50 mmHg; y 17 + ou - 1.6%, variaciones éstas no significativas. Los valores individuales no aumentaron en tres casos (37.5%). En cambio con PPCVA10 la pa02 promedio aumentó significativamente (p < 0.001) a 279 + ou - 70 mmHg, y la Dif.A.-a02 y el shunt disminuyeron significativamente (p < 0.001) a 379 + ou - 68 mmHg y 15 + ou - 2.6%. Los valores individuales no se modificaron en dos casos (16%). La paC02 y el equilibrio ácido-base se mantuvieron dentro del rango normal. La distensión pulmonar fue mayor con PPCVA10 que con PPCVA5, pero la interferencia en el campo quirúrgico provocada por un pulmón parcialmente distendido e inmóvil, es menor que la generada por la ventilación del mismo. Se destaca la eficacia de la insuflación de oxígeno con PPCVA10 en el pulmón colapsado, como método de mejorar la oxigenación arterial durante la anestesia en un pulmón

Estudio de la mecánica ventilatoria en pacientes con enfermedad pulmonar obstructiva crónica / Study of ventilatory mechanics in patients with chronic obstructive pulmonary disease

Se estudiaron 27 pacientes con Enfermedad Pulmonar Obstructiva Crónica (EPOC) con diagnóstico clínico-radiológico y espirométrico. Durante la respiración tranquila se midieron: la complacencia pulmonar estática (CE), la complacencia pulmonar dinámica (CD) y la resistencia pulmonar total (RPT). Se compararon los resultados con los de una población normal. La CE del grupo de pacientes con EPOC fue de 0.515ñ0.385 L/cm H²O y la del grupo control 0.192ñ0.039 L/cm H²O (p<0.05). La RPT de los pacientes con EPOC fue de 5.6ñ4.3 cm H²O/L/s, significativamente mayor que la del grupo control: 2.64ñ1.07 cm H²O/L/s (p<0.05). No existió diferencia significativa en los valores de la CD entre ambos grupos. No se encontró correlación entre la complacencia estática y la capacidad vital. Tampoco existió correlación de la CD o la RPT con los parámetros espirométricos indicadores de limitación del flujo espiratorio (CVF, VEF1s, VEF1s/CVF Y FEF 25-75 por ciento ). Se concluye que el estudio de la mecánica ventilatoria durante la respiración tranquila en el EPOC, aporta información sobre la distensibilidad pulmonar y el estado de la vía aérea que es complementaria de la obtenida mediante la espirometría forzada

Síndrome de apnea del sueño obstructiva: primer registro de tratamiento con presión positiva continua nasal (CPAPn) en nuestro país / Obstructive sleep apnea syndrome: first case of treatment with nasal continuous positive airway pressure in our country

Se presenta un caso del síndrome de apnea del sueño obstructiva en un hombre de 58 años con el cuadro clínico de hipoventilación-obesidad. Es el primer caso en nuestro medio en que fue posible documentar la corrección de las apneas con el uso de presión aérea positiva continua (CPAP) nasal. Se trata de un disturbio respiratorio del sueño, caracterizado por la obstrucción de la vía aérea orofaríngea, que induce despertar, fragmentando el sueño y provocando somnolencia excesiva diurna. Se presentan los datos clínicos, la función respiratoria basal en vigilia y el diagnóstico polisomnográfico nocturno de apneas obstructivas. Se describe su corrección con CPAP nasal, uno de los métodos de tratamiento de esta afección