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[Analysis of the reliability of 4 ventilators used in critically ill patients]
A C Nebra Puertas1, J Cuen Mermejo, B Virgós Señor
1Servicio de Medicina Intensiva, Hospital Clínico Universitario Lozano Blesa, Zaragoza. Beaagus@wanadoo.es
Objectives:
Mechanical ventilators are often used in critically-ill patients with acute respiratory insufficiency. We aimed to assess the reliability of four commonly used ventilators.
Methods:
This experimental study assessed four Bio-Tek VT-2 ventilators set for different levels of impedance and compliance in comparison with a tester. We gathered data on differences between the ventilators and the tester for volumes supplied and end-expiratory pressures. Statistical significance was determined using a Student-t test (95% confidence interval) and a coefficient of variation was calculated to study variation over time in parameters programmed. Error margins were calculated and applied for each ventilator.
Results:
For situations in which compliance and impedance are similar to those of patients with chronic obstructive pulmonary disease and acute respiratory distress syndrome, there were differences in tidal volumes measured by the ventilators monitors and those actually supplied at the end of the breathing circuits, although the differences are only slightly greater than the error margins. The coefficients of variation were not significant at any of the compliance and impedance levels studied.
Conclusions:
In situations of low compliance and/or high impedance, tidal volumes supplied by ventilators and volumes shown on the monitors are different, although the differences are small and hardly exceed the ventilators acceptable error margins. The coefficient of variation indicated that the parameters set remain highly stable over time.