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. 2022 Nov 4;34(3):351-359.
doi: 10.5935/0103-507X.20220383-pt. eCollection 2022.

Robust, maintainable, emergency invasive mechanical ventilator

[Article in Portuguese, English]
Paulo J R Fonte  1   2   3 , Alberto Martinho  4 , Américo Pereira  3 , Andreia Gomes  5   6   7 , Ângela Neves  1 , Antero Abrunhosa  1   5 , António Bugalho  8   9 , António Gabriel-Santos  4 , António Grilo  4 , Carlos Carmo  10 , Elsa Maltez  1 , João Agostinho do Nascimento  11 , João Goes  12 , João Martins  12 , João Pedro Oliveira  12 , Jorge Pimenta  13   14 , José Paulo Santos  15 , Luís C Gil  4 , Luís Lopes  3 , Mário Pimenta  3 , Olga Moreira  13   14 , Orlando Cunha  3 , Pedro Pinheiro de Sousa  16 , Pedro Póvoa  8   17 , Sandra Cavaco-Gonçalves  13 , Susana Barroso  1 , Telmo G Santos  4
Affiliations

Robust, maintainable, emergency invasive mechanical ventilator

[Article in Portuguese, English]
Paulo J R Fonte et al. Rev Bras Ter Intensiva. .

Abstract
in English, Portuguese

Objective: To develop a simple, robust, safe and efficient invasive mechanical ventilator that can be used in remote areas of the world or war zones where the practical utility of more sophisticated equipment is limited by considerations of maintainability, availability of parts, transportation and/or cost.

Methods: The device implements the pressure-controlled continuous mandatory ventilation mode, complemented by a simple assist-control mode. Continuous positive airway pressure is also possible. The consumption of compressed gases is minimized by avoiding a continuous flow of oxygen or air. Respiratory rates and inspiration/expiration time ratios are electronically determined, and an apnea/power loss alarm is provided.

Results: The pressure profiles were measured for a range of conditions and found to be adjustable within a ± 2.5cmH2O error margin and stable well within this range over a 41-hour period. Respiratory cycle timing parameters were precise within a few percentage points over the same period. The device was tested for durability for an equivalent period of four months. Chemical and biological tests failed to identify any contamination of the gas by volatile organic compounds or microorganisms. A ventilation test on a large animal, in comparison with a well established ventilator, showed that the animal could be adequately ventilated over a period of 60 minutes, without any noticeable negative aftereffects during the subsequent 24-hour period.

Conclusion: This ventilator design may be viable, after further animal tests and formal approval by the competent authorities, for clinical application in the abovementioned atypical circumstances.

Objetivo: Desenvolver um ventilador mecânico invasivo simples, resistente, seguro e eficiente que possa ser utilizado em áreas remotas do mundo ou zonas de guerra, em que a utilidade prática de equipamentos mais sofisticados é limitada por questões de manutenção, disponibilidade de peças, transporte e/ou custo.

Métodos: O dispositivo implementa o modo de ventilação mandatória contínua com pressão controlada, complementado por um simples modo assisto-controlado. Pode-se também utilizar a pressão positiva contínua nas vias aéreas. Ao se evitar o fluxo contínuo de oxigênio ou ar, minimiza-se o consumo de gases comprimidos. As taxas respiratórias e as relações de tempo de inspiração e expiração são determinadas eletronicamente. Além disso, conta com um alarme de apneia/falta de energia.

Resultados: Os perfis de pressão foram medidos para uma série de condições, sendo considerados ajustáveis dentro de uma margem de erro de ± 2,5cmH2O, e foram considerados bem estáveis dentro dessa variação durante um período de 41 horas. Os parâmetros de tempo do ciclo respiratório foram precisos dentro de alguns pontos percentuais durante o mesmo período. O dispositivo foi testado quanto à durabilidade por um período equivalente a 4 meses. Os testes químicos e biológicos não conseguiram identificar qualquer contaminação do gás por compostos orgânicos voláteis ou micro-organismos. Em comparação com um ventilador bem estabelecido, o teste de ventilação em um animal de grande porte mostrou que este poderia ser ventilado adequadamente durante um período de 60 minutos, sem quaisquer efeitos negativos perceptíveis durante o período subsequente de 24 horas.

Conclusão: Este projeto de ventilador pode ser viável após novos testes em animais e aprovação formal pelas autoridades competentes, para aplicação clínica nas circunstâncias atípicas anteriormente mencionadas.

PubMed Disclaimer

Conflict of interest statement

Conflicts of interest: None.

Figures

Figure 1
Figure 1
Practical implementation of the ventilator. (A) Internal view showing the command panel and the main components. (B) External view with the attached standard double-limb respiratory circuit and, on top, the exhaust outlet and air and oxygen intakes (blue connectors).
Figure 2
Figure 2
Instantaneous pressure at the Y junction, represented as a function of time after the beginning of the inspiratory cycle, for respiratory rates of 12, 18 and 25 bpm, 50% ± 5% oxygen concentration (red curves) or 100% oxygen (blue curves) and I/E ratio of 1/2 (darker curves) or 1/3 (lighter curves). (A) PIP = 30cmH2O, PEEP = 30cmH2O; (B) PIP = 30cmH2O, PEEP = 0cmH2O; (C) PIP = 10cmH2O, PEEP = 0cmH2O. The regions between the green horizontal lines define the acceptable accuracy range (see text) for PIP (upper, darker green lines) and PEEP (lower, lighter green lines).
Figure 3
Figure 3
Action of the safety valve. Pressure in the Y-junction as a function of time, obtained in CPAP mode while repeatedly completely emptying the test lung by applying an external weight, followed by release and repressurization at PIP = 30cmH2O, evidencing the effective operation of the safety valve in maintaining a maximum PIP of 45cmH2O.
Figure 4
Figure 4
Demonstration of the assisted ventilation mode. Superimposed on a default respiration rate of 10 bpm, any inspiration effort that brings the airway pressure lower than -2cmH2O triggers a new cycle. Three such events are visible between 20s and 30s.
Figure 5
Figure 5
Stability test. Pressure curves recorded for 15s every 10 minutes over a period of 41 h. Upper panel - cumulative data, highlighting the maximum (PIP - red curve) and minimum (PEEP - pink curve) pressure values in each of the 15s recording periods. The acceptable PIP and PEEP accuracy ranges as defined in figure 2 are also displayed. Lower panel - the respiratory rate measured in each of the 15s recording periods.
Figure 6
Figure 6
Volatile organic compounds. GC-MS spectrum from the gas mixture fed to the device (black curve) and the gas mixture that passed through (pink curve). Horizontal scale: retention time (minutes). Vertical scale: total ion current (arbitrary units).
Figure 7
Figure 7
Main quantities of interest as a function of the time elapsed from the start of ventilation. The upper panel corresponds to the physiological parameters of the animal, and the lower panel corresponds to the physical parameters of the ventilators. See the text for the abbreviations. The lines are meant only to guide the eye. HR - heart rate; PaCO2 - partial pressure of carbon dioxide; PaO2 - partial pressure of oxygen; HCO3 - bicarbonate; SpO2 - peripheral oxygen saturation; SatO2 - oxygen saturation; FiO2 - fraction of inspired oxygen; PIP - peak inspiratory pressure; PEEP - positive end-expiratory pressure; VT - tidal volume.
Figure 8
Figure 8
Example inspiratory pressure and flow curves. Upper panel: Ventilator 1 at minute 140. Lower panel: Ventilator 2 at minute 190. Note the markedly different curve shapes, indicative of the different controlled variables in each ventilator (volume versus pressure).
See this image and copyright information in PMC

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