Neck-worn physiological monitor

A sensor for measuring from a patient a systolic blood pressure (SYS), a diastolic blood pressure (DIA), and a pulse oximetry (SpO2), the sensor configured to be located on the patient's chest and comprising:

• a sensing portion having a flexible housing configured to be located on the patient's chest and enclosing a battery, wireless transmitter, and all of the sensor's sensing and electronic components, including:
• at least two pairs of electrode contact points disposed on a bottom surface of the flexible housing, with each pair of electrode contact points comprising a current-injecting electrode contact point and a voltage-sensing electrode contact point;
• an analog electrocardiogram (ECG) circuit contained entirely within the flexible housing and in electrical contact with a first voltage-sensing electrode contact point from a first pair of electrode contact points and a second voltage-sensing electrode contact point from a second pair of electrode contact points, the analog ECG circuit configured to generate an analog ECG waveform based on sensed voltage;
• an analog impedance circuit contained entirely within the flexible housing and in electrical contact with current-injecting and voltage-sensing electrode contact points in both the first and second pair of electrode contact points, the analog impedance circuit being configured to generate an analog impedance waveform based on sensed voltage;
• an optical system located on a bottom surface of the flexible housing, the optical system comprising a light source configured to generate radiation in both the red and infrared spectral ranges that separately irradiates a portion of the patient's chest disposed underneath the flexible housing, and a photodetector configured to detect radiation in the red spectral range that reflects off the portion of the patient's chest to generate a first analog photoplethysmogram waveform (red-PPG), and to detect radiation in the infrared spectral range that reflects off the portion of the patient's chest to generate a second analog photoplethysmogram waveform (infrared-PPG), with the optical system located between a first electrode contact point and a second electrode contact point of one of the two pairs of electrode contact points and configured to be releasably connected to the patient's chest by the electrode contact points, such that the optical system irradiates the portion of the patient's chest between the first electrode contact point and the second electrode contact point of one of the two pairs of electrode contact points;
• a digital processing system contained entirely within the housing and comprising a microprocessor and an analog-to-digital converter, the digital processing system being configured to:
• 1) digitize the analog ECG waveform to generate a digital ECG waveform, 2) digitize the analog impedance waveform to generate a digital impedance waveform, 3) digitize the analog red-PPG waveform to generate a digital red-PPG waveform, and 4) digitize the analog infrared-PPG waveform to generate a digital infrared-PPG waveform;
• a first sensor for measuring stroke volume (SV) disposed within the flexible housing, the first sensor comprising a first processor configured to determine SV from a maximum value of a mathematical derivative of the digital impedance waveform and a baseline value of the digital impedance waveform;
• a second sensor for measuring blood pressure contained entirely within the flexible housing, the second sensor comprising a second processor configured to collectively process the digital impedance waveform and one of the digital red-PPG and infrared-PPG waveforms to determine:
• 1) a first time point from one of the digital red-PPG and digital infrared-PPG waveforms, 2) a second time point from the digital impedance waveform, 3) a vascular transit time (VTT) from the temporal difference between the first and second time points, 4) a value of SYS from a linear equation that includes an inverse value of VTT, 5) a value of pulse pressure (PP) from the product of SV and a calibration parameter relating this to PP, and 6) a value of DIA from the mathematical difference between SYS and PP;
• and
• a third sensor for measuring SpO2 contained entirely within the flexible housing, the third sensor comprising a third processor configured to determine a value of SpO2 from alternating and static components of both the digital red-PPG waveform and digital infrared-PPG waveform.