Low-cost, easy-to-build noninvasive pressure support ventilator for under-resourced regions: open source hardware description, performance and feasibility testing

Abstract

Aim: Current pricing of commercial mechanical ventilators in low-/middle-income countries (LMICs) markedly restricts their availability, and consequently a considerable number of patients with acute/chronic respiratory failure cannot be adequately treated. Our aim was to design and test an affordable and easy-to-build noninvasive bilevel pressure ventilator to allow a reduction in the serious shortage of ventilators in LMICs.

Methods: The ventilator was built using off-the-shelf materials available via e-commerce and was based on a high-pressure blower, two pressure transducers and an Arduino Nano controller with a digital display (total retail cost <75 USD), with construction details provided open source for free replication. The ventilator was evaluated, and compared with a commercially available device (Lumis 150 ventilator; Resmed, San Diego, CA, USA): 1) in the bench setting using an actively breathing patient simulator mimicking a range of obstructive/restrictive diseases; and b) in 12 healthy volunteers wearing high airway resistance and thoracic/abdominal bands to mimic obstructive/restrictive patients.

Results: The designed ventilator provided inspiratory/expiratory pressures up to 20/10 cmH₂O, respectively, with no faulty triggering or cycling; both in the bench test and in volunteers. The breathing difficulty score rated (1-10 scale) by the loaded breathing subjects was significantly (p<0.005) decreased from 5.45±1.68 without support to 2.83±1.66 when using the prototype ventilator, which showed no difference with the commercial device (2.80±1.48; p=1.000).

Conclusion: The low-cost, easy-to-build noninvasive ventilator performs similarly to a high-quality commercial device, with its open-source hardware description, which will allow for free replication and use in LMICs, facilitating application of this life-saving therapy to patients who otherwise could not be treated.

FIGURE 1

Low-cost ventilator prototype. a) Front view and b) internal view showing the main modules.

FIGURE 2

An active patient simulator to test the mechanical ventilator prototype. Passive respiratory mechanics was mimicked by a resistance–compliance (R and C, respectively) passive model enclosed in a box. The active component inducing breathing in the model consisted of a blower connected to the box wall. As blower flow increased, the pressure in the box (simulated pleural pressure (Ppl)) progressively decreased to negative values, inducing inspiration in the R–C lung model. The active breathing model was connected to the ventilator under test by a conventional tube and a conventional intended leak to avoid rebreathing. An unintended leak allowed simulation of air leak caused by the lack of a perfect seal between the nasal mask and the patient's face. Pressure (P) and flow (V′) were measured at the level of the nasal mask by means of transducers.

FIGURE 3

Examples of simulated pleural pressures in the bench test. a) Conditions 1 to 4 (mild), b) conditions 5 to 8 (obstructive), and c) conditions 9 to 16 (restrictive and obstructive restrictive). See table 1 for definition of conditions.

FIGURE 4

Example of the nasal pressure and breathing flow signals recorded in one of the bench tests simulating a patient with mild disease (condition 4). a, c) Prototype ventilator and b, d) Lumis 150 ventilator (ResMed, San Diego, CA. USA). See table 1 for definition of conditions.

FIGURE 5

a) Pressure difference between (positive peak) inspiratory and (negative peak) expiratory pressures actually delivered by the ventilator and set at the ventilator control panel for both the prototype and Lumis 150 ventilators. b) Inspiratory time delay and c) tidal volume in the prototype and Lumis 150 ventilators. ns: nonsignificant.

FIGURE 6

Discomfort scoring (Visual Analog Scale) in healthy volunteers subjected to obstructive-restrictive loaded breathing when unsupported and when supported by the prototype and Lumis 150 ventilators.

FIGURE 7

Example of a) pressure and b) flow signals recorded when a resistive-restrictive loaded breathing volunteer's breathing was supported by the prototype ventilator. These are unfiltered raw data from the sensors within the ventilator. The flow signal is uncalibrated in both amplitude and zero. A.U: arbitrary units.