RESUMO
INTRODUCTION: Transmembrane pressure drop reflects the resistance of an artificial lung system to blood transit. Decreased resistance (low transmembrane pressure drop) enhances blood flow through the oxygenator, thereby, enhancing gas exchange efficiency. This study is part of a previous one where we observed the behaviour and the modulation of blood pressure drop during the passage of blood through artificial lung membranes. METHODS: Before and after the induction of multi-organ dysfunction, the animals were instrumented and analysed for venous-venous extracorporeal membrane oxygenation, using a pre-defined sequence of blood flows. RESULTS: Blood flow and revolutions per minute (RPM) of the centrifugal pump varied in a linear fashion. At a blood flow of 5.5 L/min, pre- and post-pump blood pressures reached -120 and 450 mmHg, respectively. Transmembrane pressures showed a significant spread, particularly at blood flows above 2 L/min; over the entire range of blood flow rates, there was a positive association of pressure drop with blood flow (0.005 mmHg/mL/minute of blood flow) and a negative association of pressure drop with temperature (-4.828 mmHg/(°Celsius). These associations were similar when blood flows of below and above 2000 mL/minute were examined. CONCLUSIONS: During its passage through the extracorporeal system, blood is exposed to pressure variations from -120 to 450 mmHg. At high blood flows (above 2 L/min), the drop in transmembrane pressure becomes unpredictable and highly variable. Over the entire range of blood flows investigated (0-5500 mL/min), the drop in transmembrane pressure was positively associated with blood flow and negatively associated with body temperature.
Assuntos
Pressão Sanguínea , Temperatura Corporal , Oxigenação por Membrana Extracorpórea , Insuficiência de Múltiplos Órgãos/fisiopatologia , Insuficiência de Múltiplos Órgãos/cirurgia , Animais , Velocidade do Fluxo Sanguíneo , Feminino , SuínosRESUMO
Schistosomiasis is a very important infectious disease, and pulmonary involvement is not very rare. There may be two forms of pulmonary involvement, acute and chronic. The acute form usually occurs about 6 weeks after the infection (Katayama syndrome) and seems to be due to an allergic manifestation to the presence of Schistosoma spp. worm or eggs. The chronic form is more commonly seen in endemic areas and may cause pulmonary hypertension and cor pulmonale, pulmonary granulomatous schistosomiasis, and pulmonary arteriovenous fistulas. Recurrence of pulmonary infiltrations may appear after treatment. The globalization of the world with international travel makes it necessary for clinicians around the world to be aware of some "old" diseases from endemic areas of the globe.
Assuntos
Pneumopatias Parasitárias/parasitologia , Esquistossomose mansoni , Doença Aguda , Doença Crônica , Humanos , Pneumopatias Parasitárias/tratamento farmacológico , Pneumopatias Parasitárias/epidemiologia , Esquistossomose mansoni/tratamento farmacológico , Esquistossomose mansoni/epidemiologiaRESUMO
Alveolar overdistention and cyclic reopening of collapsed alveoli have been implicated in the lung damage found in animals submitted to artificial ventilation. To test whether these phenomena are impairing the recovery of patients with acute respiratory distress syndrome (ARDS) submitted to conventional mechanical ventilation (MV), we evaluated the impact of a new ventilatory strategy directed at minimizing "cyclic parenchymal stretch." After receiving pre-established levels of hemodynamic, infectious, and general care, 28 patients with early ARDS were randomly assigned to receive either MV based on a new approach (NA, consisting of maintenance of end-expiratory pressures above the lower inflection point of the P x V curve, VT < 6 ml/kg, peak pressures < 40 cm H2O, permissive hypercapnia, and stepwise utilization of pressure-limited modes) or a conventional approach (C = conventional volume-cycled ventilation, VT = 12 ml/kg, minimum PEEP guided by FIO2 and hemodynamics and normal PaCO2 levels). Fifteen patients were selected to receive NA, exhibiting a better evolution of the PaO2/FIO2 ratio (p < 0.0001) and of compliance (p = 0.0018), requiring shorter periods under FIO2 > 50% (p = 0.001) and a lower FIO2 at the day of death (p = 0.0002). After correcting for baseline imbalances in APACHE II, we observed a higher weaning rate in NA (p = 0.014) but not a significantly improved survival (overall mortality: 5/15 in NA versus 7/13 in C, p = 0.45). We concluded that the NA ventilatory strategy can markedly improve the lung function in patients with ARDS, increasing the chances of early weaning and lung recovery during mechanical ventilation.