Comparison of two flow generators with a noninvasive ventilator to deliver continuous positive airway pressure: a test lung study

Objective To compare the performance of two continuous flow generators with a ventilator designed for noninvasive positive pressure ventilation (NPPV) to deliver continuous positive airway pressure (CPAP). The performance of flow generators using different oxygen pressure supplies was also compared.Design and setting Experimental study using a mechanical lung model in a university research laboratory.Measurements Two flow generators supplied at 100, 200, and 300 kPa and an NPPV ventilator were compared at CPAP of 5, 10, and 15 cmH₂O in: (a) area under the adjusted CPAP level during inspiration, (b) capacity to attain the preset CPAP, and (c) tidal volume.Results The NPPV ventilator attained the preset CPAP better than flow generators, but its area under adjusted CPAP was similar to or higher than that of flow generators when these were adjusted to their better pressure supply. Both flow generators had better performance with an output flow around 100 l/min, which was achieved at 100 kPa with one flow generator and 300 with the other. Flow generators and the NPPV ventilator generated similar tidal volumes.Conclusions Flow generators performance showed large variations among different devices and oxygen pressure supplies. Adjusted to their better pressure supply, flow generators had a similar or better capacity to maintain the CPAP level, but the NPPV ventilator was more reliable to attain the preset CPAP. Flow generators could be an alternative to provide CPAP in low-income areas, usually with scarce medical equipment availability.