How it works

Published September 30, 2020 © CC BY

Emergency DIY Ventilator

ReaMima, is the open and free hardware design so that anyone can help by building respirators with easily available materials.

AdvancedWork in progress10 hours1,365

Things used in this project

Hardware components

M5Stack ESP32 Basic Core IoT Development Kit

SparkFun Atmospheric Sensor Breakout - BME280

Pimoroni BME680 Breakout

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Scissor, Electrician

Story

I have assembled my prototype with empty bottles, a plastic container, two aquarium water pumps and electronics that you can buy at Amazon or electronics stores.

The basic design of the respirator is based on the use of water columns to produce the gas exchange in the lung in a simple way using materials that can be found in any store.

The idea is to be able to go to a DIY store and have the material needed to make a respirator.

In case of emergency, as we currently have with the Coronavirus, it is necessary to be able to quickly build equipment that is sufficiently reliable, with materials that are easy to locate and assemble, without having to develop new material that needs many hours to check its durability and operation.

For people of my age, this is the respirator that McGyver would build.

Breathing basically consists of introducing a certain volume of air into the lungs at a certain pressure, which causes the exchange of oxygen in the alveoli for carbon dioxide and the subsequent expulsion of this air.

There are many electro-mechanical or simply mechanical breathing aids. In all of them it is very important to regulate both the volume introduced and the pressure at which the air is introduced.

A common problem is how to carry out the control so that no more air is introduced than necessary or at more pressure than necessary. In mechanical or electromechanical systems it is necessary to have electrical locks, torque control, safety valves that guarantee this control, etc...

If a hydraulic system is used, we have many advantages since in any hardware store we find a lot of material dedicated to the subject, more than for air control, so in case of emergency, we will have a lot of material, spare parts, etc.

Most importantly, with very little knowledge we will be able to make a small respirator.

How it works

The operation of the respirator is based on using a column of water to move the volume of air at a controlled pressure and a controlled volume.

This is the simplest and most basic model of a ReaMima system, a small pump and three containers. If you want more details go to simple model

Taking into account that the volume of air we have to introduce in the lung (tidal volume) is 7ml/kg of body weight, we have to design the system according to that calculation. To avoid complications, it is best to indicate on the respirator that it should not be used with people weighing more than 100 kg and define our maximum air volume as 700 ml.

In the following image, you can see that the volume of 700 ml is our working volume, so the area striped in green is our safety margin. We must leave at least half or equal to the volume we are going to use as our safety margin.

In the initial tests, I used an empty plastic bottle to which I cut off the bottom cap.

With access to more materials, you can use plastic or metal.

It is important to mention that the container used must be clean, must not release gases, particles or elements harmful to health and must be able to be disinfected with alcohol, bleach or similar.

Likewise, it must not be able to deform under pressure, as it can deceive us with the volume insufflated.

The size of the compression tank must be large enough to store a minimum volume of water and a maximum volume that will allow us to work correctly.

you have all the rest of the project on the web :

www.reamima.com

Code

Reamima Code

/*******************************************************************
Prueba Miguel para ReaMima
                Marzo 2020
 V 0.6
*******************************************************************/

#include <M5Stack.h>
#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>

/***************************************************************************
 This is a library for the BME280 humidity, temperature & pressure sensor
 Designed specifically to work with the Adafruit BME280 Breakout
 ----> http://www.adafruit.com/products/2650
 These sensors use I2C or SPI to communicate, 2 or 4 pins are required
 to interface. The device's I2C address is either 0x76 or 0x77.
 Adafruit invests time and resources providing this open source code,
 please support Adafruit andopen-source hardware by purchasing products
 from Adafruit!
 Written by Limor Fried & Kevin Townsend for Adafruit Industries.
 BSD license, all text above must be included in any redistribution
 See the LICENSE file for details.
***************************************************************************/

#define BME_SCK 22 //SCL 22 el conector Grove Integrado
#define BME_MOSI 21 //SDA 21 el connector Grove Integrado
#define SEALEVELPRESSURE_HPA (1013.25)

Adafruit_BME280 bme; // I2C

float k = 2 * 3.1416 /360 ;

unsigned long delayTime,prevMillis,interval,tacu;
int temp;float presion;float humedad;
int fase=1; // fase =1, inspiracion, 2 pausa, 3 expiracion.
long resp=0; // contador de respiraciones
int alarma=0; // Codigo de alarma

float frecuencia = 1.5;
int ciclo,volumenCorriente=500,ti,tp,te,tv,tc,tiempocambio,cambiando=0; // VolumenCorriente, 6-10 ml/kg de peso ideal
int IE1=1,IE2=1;// IE, relacion inspiracion/expiracion, 1:3, epoc 1:4 IE1=1;IE2=3
float presionInicio,presionPico,presionMeseta,PEEP = 2.0;
float presionResistida,difPresion,alarmaMaxima=6.0,alarmaBanda=2.0,sensibilidad,IPAP,EPAP;
float preInst [330],preMedia [330]; 
float preAlarma;

int bomba1 = 2 ;int bomba2 = 5; // Salidas digitales reles inspiracion

// PresionPico, máximo inicial, Presion resistida = pico - meseta, 
// Velocidad flujo respiratorio, de 60 a 120 l/min
// Peep aprox. 5cm+, presion base para mantener abiertos alveolos
// Sensibilidad, si detecta -2cm aire ayuda a respirar
// IPAP presion positiva inspiracion, 10-15 cm H2O , EPAP , presion de expiracion, 5-8 cm H2O
// Para SDRA, 6ml/kg, F=25/min, Vflujo=60 L/min, Peep 15 cm H2O
// ti,tp,te,tv,tc,tacu; tiempo de inspiracion,pausa,expiracion,visualización, ciclo=ti+tp+te, tacu tiempo acumulado


//__________________________ SET UP __________________________________________________________
void setup() {
   M5.begin();
  Serial.begin(115200);
  Serial.println(F("Mig Mad "));
  
  pinMode(bomba1,OUTPUT);
  pinMode(bomba2, OUTPUT); 
  
  bool status;

  status = bme.begin(0x76);  
  if (!status) {
    Serial.println("No se puede encontrar un sensor de presion valido, comprueba el cableado!");
    while (1);
  }

  delayTime = 10;

  Serial.println();
  M5.Lcd.fillScreen(TFT_BLACK);
   M5.Lcd.setTextColor(TFT_RED, TFT_BLACK);
  M5.Lcd.drawString(" Espera inicio", 80, 160, 4);

   M5.Lcd.setTextColor(TFT_BLACK,TFT_YELLOW ); M5.Lcd.fillTriangle(180, 120,250,0, 320, 120, TFT_YELLOW); 
   M5.Lcd.drawString("ESPERA", 200, 90, 4);  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK);

   
   M5.update();
}


//______________________________________________ Loop _________________________________________________
void loop() { 
  calculos();
  tiempos();
  sensor();
  dibuja();
  cambia();
  switch (fase){
    case 1: //Inspiracion
     inspiracion();
    break;
    case 3:  // Expiración
     expiracion();
    break;
    default: 
    break;
  }
  
  alarmas();
 M5.update();
}
//____________________________________________________________________________________________________

void inspiracion(){
   digitalWrite(bomba1, HIGH);digitalWrite(bomba2, LOW); 
if (preInst[ciclo]>=presionPico){presionPico=preInst[ciclo];}
if (ciclo==1 && resp>=1){presionPico=0.0;}
if (resp>=1){
 if (resp>=1){
M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK); 
   M5.Lcd.drawFloat(presionPico,2, 10, 190, 2);  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK);  
Serial.print(" fase ");Serial.println(fase );

}}}

void pausa(){
  
}
void expiracion(){
   digitalWrite(bomba1, LOW);digitalWrite(bomba2, HIGH); 
}
void cambia(){
 
if (M5.BtnA.wasReleased()) {cambiando+=1;Serial.print(" Cambiando = ++++++1 ");}
if (cambiando>10){cambiando=0;}

 Serial.print(" Cambiando ");Serial.println(cambiando); 
switch (cambiando){
    case 1: //Frecuencia
    M5.Lcd.setTextColor(TFT_BLACK,TFT_WHITE);
    M5.Lcd.drawFloat(frecuencia,0, 60, 190, 2);
if (M5.BtnB.wasReleased()) {frecuencia+=1;}
if (M5.BtnC.wasReleased()) {frecuencia-=1;}
if (frecuencia>9){frecuencia=9;}if (frecuencia<1){frecuencia=0;} // Limites
    break;
    case 2: //PEEP
   M5.Lcd.setTextColor(TFT_WHITE,TFT_BLACK);
   M5.Lcd.drawFloat(frecuencia,0, 60, 190, 2);
   M5.Lcd.setTextColor(TFT_BLACK,TFT_WHITE);
   M5.Lcd.drawFloat(PEEP,1, 98, 190, 2);
if (M5.BtnB.wasReleased()) {PEEP+=0.2;}
if (M5.BtnC.wasReleased()) {PEEP-=0.2;}
if (PEEP>20.0){PEEP=20.0;}if (PEEP<0.2){PEEP=0.0;} // Limites
    break;
    case 3:  // Volumen medio
   M5.Lcd.setTextColor(TFT_WHITE,TFT_BLACK);
   M5.Lcd.drawFloat(PEEP,1, 98, 190, 2);
   M5.Lcd.setTextColor(TFT_BLACK,TFT_WHITE);
     M5.Lcd.drawFloat(volumenCorriente,0, 138, 190, 2);
if (M5.BtnB.wasReleased()) {volumenCorriente+=50.0;}
if (M5.BtnC.wasReleased()) {volumenCorriente-=50.0;}
if (volumenCorriente>900.0){volumenCorriente=900.0;}if (volumenCorriente<100.0){volumenCorriente=100.0;} // Limites

    break;
     case 4:  // IE1
   M5.Lcd.setTextColor(TFT_WHITE,TFT_BLACK);
    M5.Lcd.drawFloat(volumenCorriente,0, 138, 190, 2);
   M5.Lcd.setTextColor(TFT_BLACK,TFT_WHITE);
     M5.Lcd.drawFloat(IE1,0, 185, 190, 2);
if (M5.BtnB.wasReleased()) {IE1+=1;}
if (M5.BtnC.wasReleased()) {IE1-=1;}
if (IE1>10){IE1=10;}if (IE1<1){IE1=1;} // Limites

    break;
     case 5:  // IE1
   M5.Lcd.setTextColor(TFT_WHITE,TFT_BLACK);
     M5.Lcd.drawFloat(IE1,0, 185, 190, 2); 
   M5.Lcd.setTextColor(TFT_BLACK,TFT_WHITE);
     M5.Lcd.drawFloat(IE2,0, 220, 190, 2); 
if (M5.BtnB.wasReleased()) {IE2+=1;}
if (M5.BtnC.wasReleased()) {IE2-=1;}
if (IE2>10){IE2=10;}if (IE2<1){IE2=1;} // Limites

    break;
        case 6:  // IE1
   M5.Lcd.setTextColor(TFT_WHITE,TFT_BLACK);
     M5.Lcd.drawFloat(IE2,0, 220, 190, 2); 
   M5.Lcd.setTextColor(TFT_BLACK,TFT_WHITE);
     M5.Lcd.drawFloat(alarmaBanda,0, 270, 190, 2); 
if (M5.BtnB.wasReleased()) {alarmaBanda+=0.5;}
if (M5.BtnC.wasReleased()) {alarmaBanda-=0.5;}
if (alarmaBanda>10.0){alarmaBanda=10.0;}if (alarmaBanda<0.5){alarmaBanda=0.5;} // Limites

    break;
    default:
          case 7:  // IE1
   M5.Lcd.setTextColor(TFT_WHITE,TFT_BLACK);
     M5.Lcd.drawFloat(alarmaBanda,0, 270, 190, 2); 
  cambiando=0;

    break;
  
  
   M5.Lcd.drawFloat(alarmaBanda,0, 270, 190, 2); 
    break;
  }
   } 

void calculos()
{
  tc=60000/frecuencia;  ti=(tc/(IE1+IE2))*IE1;  te=tc-ti; tv=tc/320;
  alarmaMaxima= alarmaBanda + 2.0;
  }   

void tiempos(){
// Va calculando el tiempo en milisegundos
// Calculo de intervalo con proteccion de desborde
if (millis() - prevMillis <= 0) {
  interval = prevMillis - millis();
}
else
 {
  interval = millis()-prevMillis;
  } 
prevMillis = millis();

tacu += interval; 
if (tacu>= tc){tacu=0;resp=resp+1;}
if (tacu<=ti){fase=1;}else{fase=3;}
ciclo = tacu/tv;
if (ciclo<=1){presionInicio=presion;}
if (presion-presionInicio>0){
preInst[ciclo]=presion-presionInicio;}
else
{preInst[ciclo]=0;
  }
if (resp>1){preMedia[ciclo]=((preMedia[ciclo]*5.0)+preInst[ciclo])/6.0;}else{preMedia[ciclo]=preInst[ciclo];}

 Serial.print(" tiempo ciclo ");Serial.print(interval); Serial.print(" tacu ");Serial.print(tacu);
  //Serial.print(" P inst");Serial.print(preInst[ciclo]); Serial.print(" P media");Serial.print(preMedia[ciclo]); 
  
  Serial.print(" Respiraciones : ");Serial.print(resp);
 Serial.print(" ciclo ");Serial.println(ciclo);
}
void dibuja() {
// Dibuja solo la primera vez
if (ciclo==1){M5.Lcd.fillScreen(BLACK);  M5.Lcd.drawLine( 0,120,320,120,0x7bef);
   M5.Lcd.drawLine( 0,165,320,165,WHITE);M5.Lcd.drawLine( 0,210,320,210,WHITE);M5.Lcd.drawLine( 319,165,319,210,WHITE);
   M5.Lcd.drawLine( 0,165,0,210,WHITE);M5.Lcd.drawLine( 55,165,55,210,WHITE); // Frec
   M5.Lcd.drawLine( 95,165,95,210,WHITE);M5.Lcd.drawLine( 135,165,135,210,WHITE);
   M5.Lcd.drawLine( 178,165,178,210,WHITE);  M5.Lcd.drawLine( 255,165,255,210,WHITE);
   M5.Lcd.drawLine( 0,0,0,120,0x7BEF);  M5.Lcd.setTextColor(TFT_RED, TFT_BLACK);
   
   M5.Lcd.drawString("P. Pico",5,170,2); M5.Lcd.drawString("Frec",60,170,2); M5.Lcd.drawString("PEEP",98,170,2);
   M5.Lcd.drawString("Vm",148 ,170,2);
   M5.Lcd.drawString("I E",205 ,170,2);
   M5.Lcd.drawString("P .Desvio",260 ,170,2);
   M5.Lcd.setTextColor(TFT_ORANGE, TFT_BLACK);
   M5.Lcd.drawString("Temp C : ",5 ,140,2);
   M5.Lcd.drawString("Hum % :",98 ,140,2);
    M5.Lcd.setTextColor(TFT_YELLOW, TFT_BLACK);
   M5.Lcd.drawFloat(temp,1, 60, 140, 2);
   M5.Lcd.drawFloat(humedad,1,160 , 140, 2); 
        
 // Valores
   M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK); 
   M5.Lcd.drawFloat(frecuencia,0, 60, 190, 2);
   M5.Lcd.drawFloat(PEEP,1, 98, 190, 2);
   M5.Lcd.drawFloat(volumenCorriente,0, 138, 190, 2);
   M5.Lcd.drawFloat(IE1,0, 185, 190, 2);  M5.Lcd.drawString(":",210 ,190,2);
   M5.Lcd.drawFloat(IE2,0, 220, 190, 2); 
   M5.Lcd.drawFloat(alarmaBanda,0, 270, 190, 2); 
    
  // Cursores
   M5.Lcd.fillTriangle(55, 215, 55, 235, 65, 225, WHITE); 
   M5.Lcd.fillTriangle(145, 239, 160, 215, 175, 239, WHITE); 
   M5.Lcd.fillTriangle(250, 215, 265, 239, 280, 215, WHITE); 


   ///// Grafica en tiempo real 
  if (resp>1){
  for ( int  i = 1 ; i<320 ; i++)
    {    float a2 = i , a1= i-1  ;
         float b2= 100 -( preMedia[i]*50) , b1= 100 - (preMedia[(i-1)]*50) ;  
          M5.Lcd.drawLine(a1, b1, a2, b2,0xFF80 ); 
    }  
  }
}
 ///// Grafica en tiempo real y valores en tiempo real 
  else{
  

      float x2 = ciclo, x1 = x2-1  ;        
      float y2= 120 - (preInst[ciclo]   * 50), y1= 120 - (preInst[(ciclo-1)]   * 50) ; 
      M5.Lcd.drawLine(x1, y1, x2, y2,RED );   
  }
  }


void sensor()
{
    temp = bme.readTemperature();
  presion = bme.readPressure() / 100.0F;
  humedad = bme.readHumidity();
  
  Serial.print("Temperatura = ");  Serial.print(temp);  Serial.println(" *C");
  
  Serial.print("Presion = ");  Serial.print(presion);  Serial.println(" hPa");
  
  Serial.print("Presion = ");  Serial.print(presion / 98.0665F);  Serial.println(" cm H2O");
 
  Serial.print("Humedad = ");  Serial.print(humedad);  Serial.println(" %");

  Serial.println();
}
void alarmas()
{
  
if(preInst[ciclo]>=preMedia[ciclo]+alarmaBanda && alarma==0){alarma=2;}  // Aviso presion superior a la tendencia 5 ultimas respiraciones  
if(preInst[ciclo]> alarmaMaxima && resp>=1){alarma=1;preAlarma=preInst[ciclo];}  // Aviso presion > presion pico alarma


if(alarma==1){   
   M5.Speaker.tone(461, 50); //frequency 461, with a duration of 200ms
   M5.Speaker.tone(661, 50); //frequency 661, with a duration of 200ms
   M5.Lcd.setTextColor(TFT_BLACK,TFT_YELLOW ); M5.Lcd.fillRect(180, 0,320,40, TFT_YELLOW); 
   M5.Lcd.drawString("ALARMA", 200, 10, 4);  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK);
 Serial.print("*****************ALARMA 1 Sobrepresion= ");  Serial.println(preAlarma);
 
if ((ciclo/25)*25==(ciclo/50)*50){M5.Lcd.setTextColor(TFT_BLACK,TFT_YELLOW);M5.Lcd.drawString("P.Pico Alta", 230, 210, 2);}
else{M5.Lcd.setTextColor(TFT_YELLOW,TFT_BLACK);M5.Lcd.drawString("P.Pico Alta", 230, 210, 2);}

if (M5.BtnC.wasReleased()) {
    alarma=0;}
}
if(alarma==2){   
   M5.Speaker.tone(461, 10); //frequency 461, with a duration of 200ms
   M5.Speaker.tone(661, 50); //frequency 661, with a duration of 200ms
   M5.Lcd.setTextColor(TFT_BLACK,TFT_ORANGE ); M5.Lcd.fillRect(220, 0 , 320, 40, TFT_ORANGE); 
   M5.Lcd.drawString("AVISO", 230, 10, 4);  M5.Lcd.setTextColor(TFT_WHITE, TFT_BLACK);

if ((ciclo/25)*25==(ciclo/50)*50){M5.Lcd.setTextColor(TFT_BLACK,TFT_ORANGE);M5.Lcd.drawString("Tendencia", 230, 210, 2);}
else{M5.Lcd.setTextColor(TFT_ORANGE,TFT_BLACK);M5.Lcd.drawString("Tendencia", 230, 210, 2);}

if (M5.BtnC.wasReleased()) {
    alarma=0;}
}


}

Credits

Mig Mad

1 project • 2 followers

Engineer

Thanks to Miguel Madrid .

Emergency DIY Ventilator

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

How it works

Schematics

basic scheme of operation

Code

Reamima Code

Credits

Mig Mad

Comments

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Emergency DIY Ventilator

Emergency DIY Ventilator

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

How it works

Schematics

basic scheme of operation

Code

Reamima Code

Credits

Mig Mad

Comments

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