Effects of lung protective mechanical ventilation associated with permissive respiratory acidosis on regional extra-pulmonary blood flow in experimental ARDS

Abstract

BackgroundLung protective mechanical ventilation with limited peak inspiratory pressure has been shown to affect cardiac output in patients with ARDS. However, little is known about the impact of lung protective mechanical ventilation on regional perfusion, especially when associated with moderate permissive respiratory acidosis. We hypothesized that lung protective mechanical ventilation with limited peak inspiratory pressure and moderate respiratory acidosis results in an increased cardiac output but unequal distribution of blood flow to the different organs of pigs with oleic-acid induced ARDS.MethodsTwelve pigs were enrolled, 3 died during instrumentation and induction of lung injury. Thus, 9 animals received pressure controlled mechanical ventilation with a PEEP of 5 cmH2O and limited peak inspiratory pressure (17 ± 4 cmH2O) versus increased peak inspiratory pressure (23 ± 6 cmH2O) in a crossover-randomized design and were analyzed. The sequence of limited versus increased peak inspiratory pressure was randomized using sealed envelopes. Systemic and regional hemodynamics were determined by double indicator dilution technique and colored microspheres, respectively. The paired student t–test and the Wilcoxon test were used to compare normally and not normally distributed data, respectively.ResultsMechanical ventilation with limited inspiratory pressure resulted in moderate hypercapnia and respiratory acidosis (PaCO2 71 ± 12 vs. 46 ± 9 mmHg, and pH 7.27 ± 0.05 vs. 7.38 ± 0.04, p < 0.001, respectively), increased cardiac output (140 ± 32 vs. 110 ± 22 ml/min/kg, p<0.05) and regional blood flow in the myocardium, brain and spinal cord, adrenal and thyroid glands, the mucosal layers of the esophagus and jejunum, the muscularis layers of the esophagus and duodenum, and the gall and urinary bladders. Perfusion of kidneys, pancreas, spleen, hepatic arterial bed, and the mucosal and muscularis blood flow to the other evaluated intestinal regions remained unchanged.ConclusionsIn this porcine model of ARDS mechanical ventilation with limited peak inspiratory pressure resulting in moderate respiratory acidosis was associated with an increase in cardiac output. However, the better systemic blood flow was not uniformly directed to the different organs. This observation may be of clinical interest in patients, e.g. with cardiac, renal and cerebral pathologies.Electronic supplementary materialThe online version of this article (10.1186/s12871-017-0439-7) contains supplementary material, which is available to authorized users.

The risk factors for acute respiratory distress syndrome in patients with severe acute pancreatitis

“…Previous studies [ 27 – 29 ] have shown that related risk factors such as smoking, alcohol abuse, hypoproteinemia, and diabetes can effectively predict the occurrence of ARDS. In addition, research results [ 24 , 30 ] indicate that alcoholism, hypoalbuminemia, APACHE lI score, gender, SCr, etc.…”

Changes of blood gas analysis in moderate-to-severe acute respiratory distress syndrome patients during long-term prone position ventilation: a retrospective cohort study

“…During PPV, the anterior chest wall and abdomen were restricted, with elastic resistance increasing and minute volume decreasing. PaCO 2 inevitably rose further when lung homogeneity had not yet been optimally achieved after a change in the body position ( 9 ). Severe hypercapnia or a rapid rise in PaCO 2 could cause myocardial depression, leading to an increase in pulmonary vascular resistance (PVR), aggravating right heart insufficiency, thereby increasing the risk of inpatient death in patients with cerebral injury ( 28 ), and exacerbating concomitant symptoms such as renal injury, pulmonary injury, and so on ( 29 , 30 ).…”

“…Owing to the impact of hypercapnia on all visceral organs, PPV may match ventilation/blood perfusion and improve the right heart function later than the improvement of oxygenation—thus, the effect of early PPV on carbon dioxide partial pressure (PaCO 2 ) is poorly understood. Given low tidal volume LPVS, it is worthwhile to evaluate the effect of prolonged PPV on permissive hypercapnia ( 9 , 10 ); at present, there is no study on the dynamic changes of hyperoxia and permissive hypercapnia during prolonged PPV. In this study, all blood gas indexes were collected before and after each application of PPV in patients to investigate their dynamic change rule in order to offer better guidance on clinical adjustment.…”

Prueba de concepto de la eficacia del equipo prototipo “Ciclador Automático para Resucitador” en un cerdo adulto

“…Durante la VMC mediante el prototipo CAR, los patrones de ventilación de un volumen minuto de 7 ml/kg y 9.7 ml/kg con PEEP de 5, 10, 15 cmH2O, permitieron mantener al animal dentro de rangos de valores cardiorespiratorios y metabólicos fisiológicos (Hannon et al, 1990). Estos patrones de ventilación ofrecieron una respiración adecuada para el animal y coinciden con los utilizados en otros ensayos de características similares a este, donde los cerdos fueron mantenidos adecuadamente con un volumen corriente de 6-7 ml/kg, una FR of 27-40 ciclos respiratorios por minuto y una PEEP de 9-10 cmH2O (Hering et al, 2017, Nay et al, 2017. En estos reportes los investigadores utilizaron un equipo de VMC comercial probado y necesitaron sólo 1 patrón de ventilación durante todo o buena parte del ensayo.…”

“…Durante nuestro estudio, se probaron distintos patrones de ventilación para evaluar las capacidades del prototipo CAR para adaptarse a distintas condiciones de trabajo, como las que se pueden presentar en un paciente con la capacidad pulmonar reducida por COVID-19 (Hua et al, 2020;Wiersinga et al, 2020) o cuando se necesita cambiar de un patrón de ventilación a otro porque el primero no es adecuado para el sostén respiratorio. Todos los parámetros analizados durante el periodo de estudios para los patrones de ventilación de 7 ml/kg y 9.7 ml/kg Prueba de respirador en cerdo con PEEP de 5, 10, 15 cmH2O, coinciden con los reportados en otros estudios realizados en cerdos y mantenidos a través de equipos de VMC de alta complejidad en unidades de cuidados intensivos (Hanneman et al, 2004;Hering et al, 2017).…”