Proposta de um adaptador para pressão positiva em cânula metálica conectada à válvula exalatória

Abstract

Tracheostomy is an artificial airway which can be made by plastic or metal cannula. For applying treatment with positive pressure it needs an adapter connector. Objective: to create a connector to be attached between the metal cannula and the exhalation valve. Method: for the connector device, three models have been developed, from the dimensions of a metal cannula number 5 and two exhalation valves. The first two models were machined with polyamide material, having the first one funnel-shaped with an angle of 140° closed to the end connectable to the cannula; the second having predominantly conical shape and angular opening of 2°. The third prototype was built similarly to the second model. However, it is made by resin and produced on a 3D printer. Connectors were tested with two exhalation valves, made of acrylic and identified as I and II. Valve I is a tube with an exhalation hole and an inlet for oxygen therapy. Valve II contains two dockable continuous drain pipes. The evaluation tests involved: leakage analysis using positive pressure generator set at 7.5, 13 and 20 cmH2O for 1-2 h, in an analog lung model; input and output pressure measurements; destructive mechanical testing; computer-based flow simulation and reaction to sterilization. Results: it was obtained a higher flow velocity along the upper airway path till the left bronchus and distal to the air. Destructive testing reached maximum stresses of 71.43 and 75.44 MPa for the samples 1 and 2, respectively. Flow leaks' measurements had shown lower average for the combination of resin with exhalation valve I (18.8 (± 10.78) l/m). For the measures of input pressure and output of the generator, the error was found to be 4.48 % on the values of the three applied pressures. Regarding sterilization, the procedure with ethylene oxide has affected the dimensions and functionality of the resin-based device, but the machined prototypes remained unchanged. Concerning the hydrogen peroxide and autoclaving procedures, there was no change on the resin model ́s functionality. Conclusions: with relation to the flow leaks, the combination where occurred the least leaks was the resin based device with valve I. The machined connector, which was sterilized only with ethylene oxide, remained unchanged after the procedure. The prototype which was submitted to ethylene oxide, hydrogen peroxide and autoclave, had introduced dimensional and functional changes with the ethylene oxide. As for the flow leak, the best solution is the combination of the resin-based connector with valve I, demanding less of the compensation system. For conclusive results, in vivo essays are expected.