← Executive Summary • Pillar 01: First-Principles Transduction & Biophysics
FDA 510(k)-Cleared Bio-Signal Algorithms & Biophysics

FDA Bio-Signal Processing, Optical Biophysics &
Calibration-Free Blood Pressure Estimation

Architecting clinical machine learning & bio-signal processing algorithms for medical wearables: 510(k) FDA-cleared medical device algorithms (FDA K240236 & FDA K242224 for Heart Rate, SpO2, Total Sleep Time, Apnea-Hypopnea Index), calibration-free Blood Pressure (FDA pending), optical spectroscopy, Mie scattering, and multi-isobestic tissue models (HPYTissueProperties).

Optical signals passing through layered tissue and resolving into a physiological pulse waveform
PHOTON → TISSUE → SIGNAL Multi-Wavelength Optical Biophysics, Mie Scattering Inversion & Pulse Waveform Resolution
Executive TL;DR

Biomedical Algorithms & Signal Processing

View 5 Pillars →
🎯 Business Context

Clinical signal processing pipeline transforming raw multi-wavelength optical signals into FDA-grade diagnostic biometrics.

⚡ Technical Hurdle

Dynamic AC/DC baseline drift compensation, non-linear arterial compliance, and multi-layer skin pigmentation attenuation.

🏆 Deliverable & Impact

Dual FDA 510(k) clearances (K240236, K242224), 22 MedTech patents, and 8-bit quantized CNN running in 360 KB RAM.

Clinical Grade Outputs

Clinical Grade Algorithms

Comprehensive suite of medical-grade bio-signal processing and physiological estimation algorithms designed for continuous wearable health monitoring.

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FDA Pending
SBP
Systolic Blood Pressure

Peak arterial pressure during ventricular contraction, estimated calibration-free via multi-wavelength optical PPG & biophysical pulse wave analysis.

mmHg happyml.bp
compress
FDA Pending
DBP
Diastolic Blood Pressure

Minimum baseline arterial pressure during cardiac filling phase, utilizing isobestic absorption physics and elastic vascular impedance modeling.

mmHg happyml.bp
monitor_heart
FDA
HR
Heart Rate

Continuous beat-by-beat cardiac pulse frequency with advanced motion artifact rejection (FDA 510(k) K240236) across diverse activity and perfusion states.

BPM FDA K240236
query_stats
Clinical Grade
HRV
Heart Rate Variability

Time-domain (RMSSD, SDNN, pNN50) and frequency-domain (LF/HF ratio) autonomic nervous system sympathetic vs. parasympathetic tone extraction.

ms • Ratio Autonomic Tone
bloodtype
FDA
SpO2
Blood Oxygen Saturation

Continuous arterial functional blood oxygenation via dual-wavelength (Red/IR) ratio-of-ratios photoplethysmography (FDA 510(k) K240236).

% Oxygen FDA K240236
bedtime
FDA
AHI
Apnea-Hypopnea Index

Clinical diagnostic index quantifying obstructive and central sleep apnea severity per sleep hour (FDA 510(k) K242224 Home Sleep Test clearance).

events / hr FDA K242224
trending_down
Clinical Grade
ODI
Oxygen Desaturation Index

Quantifies the hourly rate of significant arterial oxygen desaturation events (≥3% and ≥4% drops) correlating with nocturnal hypoxemic burden.

events / hr Hypoxemia
waves
Clinical Grade
RDI
Respiratory Disturbance Index

Comprehensive respiratory disturbance evaluation aggregating apneas, hypopneas, and Respiratory Effort-Related Arousals (RERAs).

events / hr Sleep Architecture
timelapse
FDA
TST
Total Sleep Time

Medical-grade total objective sleep duration distinguishing wakefulness, light sleep, deep sleep, and REM phases (FDA 510(k) K242224).

hrs : mins FDA K242224
air
FDA
RR
Respiration Rate

Continuous breathing rate derived from respiratory-induced amplitude variations (RIAV) and frequency modulations in peripheral PPG waveforms.

breaths / min FDA K240236
timer
Clinical Grade
MSLT
Multiple Sleep Latency

Diagnostic assessment of sleep onset propensity, daytime hypersomnolence, and objective sleepiness latency modeling.

minutes Diagnostic Latency
directions_run
Clinical Grade
Actigraphy
Kinematic Motion & Rest

3-axis MEMS accelerometer motion integration, Cole-Kripke sleep/wake classification, step cadence, and active energy expenditure.

Counts • Epochs MEMS Dynamics
psychology
Clinical Grade
Stress
Autonomic Stress Index

Continuous psychophysiological stress tracking fusing autonomic HRV spectral balance with electrodermal and skin temperature fluctuations.

0 – 100 Index Psychophysiology
palette
Biophysics Model
Skin Tone
Melanin & Phototype

Fitzpatrick skin phototype classification (Types I–VI) & real-time epidermal melanin absorption compensation via Mie scattering biophysics.

Fitzpatrick I–VI HPYTissueProperties
🏛️ Official FDA 510(k) Medical Device Clearances
FDA K240236 Record ↗ FDA K242224 Record ↗

Happy Health Medical Device 510(k) Clearances (Class II Medical Device)

FDA 510(k) K240236: Happy Ring Health Monitoring System — Cleared for continuous biometric monitoring including Heart Rate (HR), Pulse Oximetry (SpO2), and respiration.
FDA 510(k) K242224: Happy Health Home Sleep Test — Cleared for Total Sleep Time (TST), Apnea-Hypopnea Index (AHI), and medical-grade Obstructive Sleep Apnea (OSA) diagnosis.

🧠 Single-Handed Human Architecture Coded Prior to AI Coding Agents
The happyml framework packages (happyml.bp, happyml.baseline, happyml.features, and happyml.model) were fully designed and coded from scratch before AI coding agents existed. They demonstrate deep first-principles knowledge of optical biophysics, tissue scattering, spectral absorption, and statistical signal processing.
2 FDA Clearances
FDA K240236 & K242224
HR, SpO2, TST & AHI Medical Clearances
1 FDA Pending
Blood Pressure Algorithm (happyml.bp)
Calibration-Free Multi-Spectral PPG
100%
Optical Biophysics & Mie Scattering
HPYTissueProperties Tissue Bed Models
9 ML Packages
happyml.baseline / features / model
End-to-End Signal Pipeline Architecture
Algorithms Table of Contents

Clinical Algorithms & Signal Processing Frameworks

Select any project card below to view its technical sub-page.

PROJECT 01 FDA Approved

FDA-Cleared Bio-Signal Algorithms (FDA K240236 & K242224)

FDA 510(k)-cleared medical device algorithms for Heart Rate (HR), Oxygen Saturation (SpO2), Total Sleep Time (TST), and Apnea-Hypopnea Index (AHI), plus pending Blood Pressure (BP).

ml-py / happyml Private Repository
PROJECT 02 Biophysics / Optical

HPYTissueProperties & Optical Spectroscopy (`happyml.bp`)

Calibration-free BP algorithm using multi-spectral LED absorption, Mie scattering, tissue vascular bed volume expansion, and multi-isobestic point fitting without arm cuff calibration.

HPYTissueProperties Private Repository
PROJECT 03 Baseline Analysis

Baseline Analysis System (`happyml.baseline`)

Advanced baseline conditioning system featuring baseline wander removal, fitting optimizers (`fits.py`), curve combiners (`combiners.py`), and step/rise detection (`steps.py`).

happyml.baseline Private Repository
PROJECT 04 Feature Extraction

Feature Extraction Pipeline (`happyml.features`)

High-dimensional bio-signal feature extraction framework supporting cardiopulmonary coupling (CPC), PPG pulse morphology, accelerometry, and tissue metrics.

happyml.features Private Repository
PROJECT 05 Automated ML

Automated ML Architecture (`happyml.model`)

Machine learning model engine featuring automated estimator selection (`automation.py`), custom scalers (`scalers.py`), and signal resampling (`signal.py`).

happyml.model Private Repository
FDA 510(k) Clearances & Medical Devices

FDA-Cleared Bio-Signal Algorithms (K240236 & K242224)

Architecting clinical-grade medical device software algorithms validated for official 510(k) FDA clearances across physiological monitoring metrics.

FDA Physiological Pipeline Architecture
Inspect High-Resolution Diagram
Clinical Signal Processing Pipeline

From 256 Hz DMA Ingestion to FDA 510(k) Clearances

Real-time DMA sampling, wavelet denoising, GMM pulse morphology, and clinical vital sign estimation.

FDA 510(k)-Cleared Medical Algorithms

  • ✓
    FDA K240236 (Heart Rate / HR): Beat-by-beat peak detection & noise suppression (happyml.hr).
  • ✓
    FDA K240236 (SpO2): Multi-wavelength ratio-of-ratios PPG calibration (happyml.spo2).
  • ✓
    FDA K242224 (Total Sleep Time / TST): Sleep-wake classification & circadian actigraphy (happyml.sleep_fda).
  • ✓
    FDA K242224 (Apnea-Hypopnea Index / AHI): Sleep apnea & desaturation event detection (happyml.ahi).

FDA Calibration-Free Blood Pressure

Calibration-free continuous Blood Pressure (BP) monitoring algorithm using multi-spectral optical PPG waveforms and biophysical tissue models (happyml.bp).

Optical Biophysics & Mie Scattering

HPYTissueProperties & Optical Spectroscopy (happyml.bp)

Calibration-free arterial blood pressure derivation based on multi-spectral LED absorption, Mie scattering, tissue vascular bed volume expansion, and multi-isobestic point fitting.

Biophysical Optical Model Architecture
Inspect High-Resolution Diagram
Biophysical Optical Spectroscopy

Tissue Vascular Bed Absorption & Isobestic Point Fitting

Multi-wavelength optical transduction isolating arterial pulse waves from venous baseline wander and tissue scattering.

HPYTissueProperties Biophysical Container

HPYTissueProperties models light propagation through biological tissue beds without requiring inflatable cuff calibration. By combining Mie scattering equations, multi-wavelength LED absorption spectra, and tissue depth attenuation factors, blood pressure is derived directly as the time derivative of blood volume (dP/dt ∝ dV/dt).

happyml/bp/core.py (HPYTissueProperties Structure)
class HPYTissueProperties:
    """Container for multi-spectral tissue properties extractable from BP algorithms."""
    scattering: HPYBPScatteringInternals   # Mie scattering & anisotropy factors
    perfusion: HPYBPPerfusionCorrection     # Arterial & microvascular blood perfusion
    absorption: Mapping[LED, HPYVariableAbsorption]  # Multi-wavelength absorption
    volume: HPYBPVolumeEstimates           # Multi-isobestic blood volume fitting
    depths: HPYBPTissueDepths              # Optical dermal penetration depth
    gbspo2: HPYGBIntegratedSpO2            # Integrated oxygen saturation
    beats: HPYBPBeatFeatures               # Beat-by-beat arterial waveforms
Signal Processing System

Baseline Analysis System (`happyml.baseline`)

Modular baseline analysis system for conditioning raw optical bio-signals, removing motion artifacts and baseline wander, and detecting transient step/rise events.

Baseline Conditioning Plot
Inspect Plot
Signal Conditioning

Baseline Wander Removal & Step Detection

Conditioning raw optical bio-signals prior to feature extraction.

Feature Engineering & Normalization

Feature Extraction Pipeline (happyml.features)

High-dimensional bio-signal feature extraction framework featuring specialized biophysical extractors (cpc.py, tissue.py, hr.py), deterministic on-disk caching, anchor array synchronization, whole-day diurnal aggregators, and dynamic algebraic feature aliases.

Bio-Signal Feature Extraction & Composition Architecture
Inspect Architecture Diagram
Biophysics • Caching • Dynamic Aliases

Biophysical Extractors, Caching, Anchor Slicing & Dynamic Aliases

Engineering deterministic, cached, and algebraically composable feature spaces for clinical physiological estimation.

  • ✓
    Cardiopulmonary Coupling (cpc.py): Cross-spectral coherence and phase-locking algorithms tracking synchronization between cardiac pulses, PPG pulse waves, and respiration to classify high/low frequency sleep depth.
  • ✓
    Optical Tissue Biophysics (tissue.py): Integrated HPYTissueProperties modeling multi-wavelength optical absorption, epidermal melanin attenuation, and Mie/Rayleigh skin scattering for skin-tone independent calibration.
  • ✓
    Deterministic Content-Hashed Caching (files.py): Fast on-disk caching leveraging SHA-256 signature hashing (get_str_hash), epoch timestamp boundaries, and versioned invalidation (DEFAULT_VERSION) to eliminate redundant computation across multi-day patient bio-recordings.
  • ✓
    Anchor Arrays & Multi-Sensor Alignment (base.py): Built master temporal anchor arrays (start, stop, dt) and time_align_vectors interpolation to synchronize asynchronous sensor streams (PPG, ACC, Temp, EDA) into a unified time grid.
  • ✓
    Temporal Slicing & SQI Exclusion Masks (base.py): Time-region slicing, fuzzy interval intersections, and automatic filtering of invalid NaN epochs or low signal quality regions via FeatureMatrixMeta.
  • ✓
    Whole-Day Diurnal Aggregations (HPYWholeDayAggregator): Computed 24-hour diurnal baseline shifts, circadian amplitude rhythms, daytime resting medians, and nocturnal nadir metrics into standardized longitudinal feature sets.
  • ✓
    Dynamic Feature Alias Composition (aliases.py): Developed HPYFeatureAlias and HPYExpressionFeatureAlias enabling strongly typed, dynamic on-the-fly algebraic expressions and thresholded region merging across feature collections.
Automated Machine Learning

Automated ML Pipeline Architecture (`happyml.model`)

Automated machine learning model engine supporting estimator selection (`automation.py`), custom signal scalers (`scalers.py`), and signal resampling (`signal.py`).

Model Residual Analysis
Inspect Plot
Statistical Modeling

Model Residual Analysis & Normalization

Evaluating prediction residuals and distribution fitting.