Patient Vital Signs Remote Monitoring System

6. Firmware Development

// Low-power BLE implementation
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>

#define SERVICE_UUID "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"

BLEServer *pServer = NULL;
BLECharacteristic *pCharacteristic = NULL;

void sendVitalData(float hr, float spo2, float temp) {
  StaticJsonDocument<128> doc;
  doc["hr"] = hr;
  doc["spo2"] = spo2;
  doc["temp"] = temp;
  doc["ts"] = millis();
  
  char jsonBuffer[256];
  serializeJson(doc, jsonBuffer);
  
  pCharacteristic->setValue(jsonBuffer);
  pCharacteristic->notify();
  
  // Deep sleep between readings
  enterDeepSleep(60000); // 1 minute interval
}

void enterDeepSleep(uint64_t time_ms) {
  esp_sleep_enable_timer_wakeup(time_ms * 1000);
  esp_deep_sleep_start();
}

7. Data Security & Encryption

// End-to-end encryption
#include <mbedtls/aes.h>
#include <mbedtls/entropy.h>
#include <mbedtls/ctr_drbg.h>

// AES-256 encryption for PHI
void encryptPHI(uint8_t* data, size_t len, uint8_t* key) {
  mbedtls_aes_context aes;
  mbedtls_aes_init(&aes);
  mbedtls_aes_setkey_enc(&aes, key, 256);
  
  uint8_t iv[16] = {0}; // Use random IV in production
  mbedtls_aes_crypt_cbc(&aes, MBEDTLS_AES_ENCRYPT, len, iv, data, data);
  
  mbedtls_aes_free(&aes);
}

// TLS 1.3 for transmission
WiFiClientSecure client;
client.setCACert(rootCACertificate);
client.setCertificate(clientCertificate);
client.setPrivateKey(clientPrivateKey);

8. Cloud Infrastructure

AWS HIPAA-eligible services:

# AWS Architecture
┌─────────────┐      ┌──────────────┐      ┌─────────────┐
│ IoT Core    │─────▶│ Lambda       │─────▶│ DynamoDB    │
│ (Device     │      │ (Processing) │      │ (Encrypted) │
│  Gateway)   │      │              │      │             │
└─────────────┘      └──────────────┘      └─────────────┘
                            │
                            ▼
                     ┌──────────────┐
                     │ SNS/SQS      │
                     │ (Alerts)     │
                     └──────────────┘

# CloudFormation (HIPAA-compliant)
Resources:
  VitalSignsTable:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: PatientVitalSigns
      SSESpecification:
        SSEEnabled: true
        SSEType: KMS
      PointInTimeRecoverySpecification:
        PointInTimeRecoveryEnabled: true

9. Healthcare Dashboard

• Real-time vital signs display
• Historical trend charts (24h, 7d, 30d)
• Patient list with status indicators
• Alert history and acknowledgments
• Care team communication tools

10. Emergency Alert System

// Clinical alert rules
const ALERT_RULES = {
  BRADYCARDIA: { hr: { min: 40 }, priority: "HIGH" },
  TACHYCARDIA: { hr: { max: 120 }, priority: "HIGH" },
  HYPOXIA: { spo2: { min: 90 }, priority: "CRITICAL" },
  FEVER: { temp: { max: 38.5 }, priority: "MEDIUM" },
  HYPOTHERMIA: { temp: { min: 35.5 }, priority: "HIGH" }
};

function evaluateAlerts(vitals) {
  const alerts = [];
  
  if (vitals.hr < 40 || vitals.hr > 120) {
    alerts.push({
      type: "HEART_RATE_ABNORMAL",
      priority: "HIGH",
      message: `HR: ${vitals.hr} bpm`,
      action: "Notify nurse station"
    });
  }
  
  if (vitals.spo2 < 90) {
    alerts.push({
      type: "HYPOXIA",
      priority: "CRITICAL",
      message: `SpO2: ${vitals.spo2}%`,
      action: "Immediate intervention required"
    });
    sendPagerDutyAlert();
  }
  
  return alerts;
}

11. Mobile App Integration

// React Native patient app
import PushNotification from 'react-native-push-notification';

function VitalMonitor({ patientId }) {
  const [vitals, setVitals] = useState(null);
  
  useEffect(() => {
    const subscription = mqtt.subscribe(
      `patients/${patientId}/vitals`,
      (message) => {
        const data = JSON.parse(message);
        setVitals(data);
        
        // Local alert
        if (data.spo2 < 90) {
          PushNotification.localNotification({
            title: 'Low Oxygen Alert',
            message: `SpO2: ${data.spo2}%`,
            priority: 'high'
          });
        }
      }
    );
    
    return () => subscription.unsubscribe();
  }, []);
  
  return (
    <View>
      <Text>HR: {vitals?.hr} bpm</Text>
      <Text>SpO2: {vitals?.spo2}%</Text>
      <Text>Temp: {vitals?.temp}°C</Text>
    </View>
  );
}

12. Clinical Testing