Calibration of Seven ICU Ventilators for Mechanical Ventilation with Helium–Oxygen Mixtures

Abstract

The study evaluated seven intensive care unit (ICU) ventilators (Veolar FT, Galileo, Evita 2, Evita 4, Servo 900C, Servo 300, Nellcor Puritan Bennett 7200 Series) with helium-oxygen (HeO 2 ), using a lung model, to develop correction factors for the safe use of HeO 2 . A 70:28 helium-O 2 mixture (heliox) replaced air and combined with O 2 (HeO 2 ). Theoretical impact of HeO 2 on inspiratory valves and gas mixing was computed. True fraction of inspired oxygen (F I O2 del) was compared with fraction of inspired oxygen (F I O2 ) set on the ventilator (F I O2 set). True tidal volume (V T del) was compared with V T set on the ventilator (V T set) in volume control and with control V T del at F I O2 1.0 in pressure control. F I O2 del minimally exceeded F I O2 set ( р 5%) except with the 7200 Series (F I O2 del Ͼ F I O2 set by 125%). In volume control, with the Veolar FT, Galileo, Evita 2, and Servo 900C, V T del Ͼ V T set, with the 7200 Series V T del Ͻ V T set (linear relationship, magnitude of discrepancy inversely related to F I O2 set). With the Evita 4, V T del Ͼ V T set (nonlinear relationship), whereas with the Servo 300 V T del ϭ V T set. In pressure control, V T del was identical to control measurements, except with the 7200 Series (ventilator malfunction). Correction factors were developed that can be applied to most ventilators. Tassaux D, Jolliet P, Thouret J-M, Roeseler J, Dorne R, Chevrolet J-C. Calibration of seven ICU ventilators for mechanical ventilation with helium-oxygen mixtures. AM J RESPIR CRIT CARE MED 1999;160:22-32.Reducing the density of inspired gas by using a mixture of helium and O 2 (HeO 2 ) instead of air and O 2 (airO 2 ) can be beneficial in spontaneously breathing patients with upper or lower airway obstructive disease (1, 2). In acute severe asthma, breathing HeO 2 increases peak expiratory flow and Pa O2 , and decreases pulsus paradoxus, Pa CO 2 , and dyspnea (3-5). In patients with COPD, breathing HeO 2 increases expiratory flow and decreases airway resistance (6, 7). Moreover, evidence suggests that these favorable effects can also be obtained during mechanical ventilation in status asthmaticus (8) and in patients with COPD (9, 10), even though the data are still preliminary in the latter patient population, and await confirmation by prospective studies. However, the physical properties of helium could interfere with several key ventilator functions such as gas mixing, inspiratory and expiratory valve accuracy, flow measurement, triggering, positive end-expiratory pressure (PEEP), and automatic leakage compensation, thus raising issues regarding the accuracy of ventilator performance (11) and patient safety.The present study was designed to test the performances of seven standard intensive care unit (ICU) ventilators available in Europe during HeO 2 utilization, compared with theoretical predictions based on the physical properties of helium, and to develop correction factors (12) to ensure the safe use of HeO 2 during mechanical ventilation.

Use of Heliox in the Management of Neonates with Meconium Aspiration Syndrome

“…Heliox use with standard ventilators may result in considerable differences between set and delivered FiO 2 and V T [13,17] . The Avea ventilator which was used in the study is designed to automatically compensate for the gas mixture and allows reliable delivery of heliox.…”

Inhalation Therapy in Patients Receiving Mechanical Ventilation: An Update

“…(39,41) A preferred strategy in maximizing aerosol deposition with a nebulizer is to power it with 6 to 8 L/min of oxygen and entrain the aerosol into a ventilator circuit that contains heliox. (39,40) Tassaux et al (42) showed that aerosol deposition to the lower airways is increased by 50% with that method compared to using oxygen alone in the ventilator circuit. Heliox may adversely affect the function of some ventilators, so the ventilator must be tested with heliox to detect any malfunction before use in patients.…”

“…Heliox may adversely affect the function of some ventilators, so the ventilator must be tested with heliox to detect any malfunction before use in patients. (42) As a practical consideration, the available drug options available in pMDIs are limited. Relative cost effectiveness of the pMDI has shifted as the costs of HFA-pMDIs have risen, sometimes dramatically, over their CFC-propelled…”

Lack of Benefit of Heliox During Mechanical Ventilation of Subjects With Severe Air-Flow Obstruction

“…It is well known that there is considerable variability among ventilators with regard to their operation during ventilation with heliox. 19 The Avea ventilator (Care Fusion) that was used in our study is an FDAcleared commercial ventilator that has been specifically designed to operate with heliox without need for adjustments in settings, giving us confidence that there were no technical factors that would account for our findings. However, the ventilator (Servo, Maquet, Wayne, New Jersey) used in the earlier studies is also believed to be appropriate for use with heliox without need for manual adjustment in volume or flow.…”