Engineers and physicians at the Johns Hopkins University School of Medicine have designed a hand-held, battery-powered, 3D-printed device that quickly picks up vital signs from a patient’s lips and fingertip. The human "check-engine light," called MouthLab, could replace the bulky monitors now used in hospitals.

The device may be able to detect early signs of medical emergencies, such as heart attacks, or prevent unnecessary ambulance trips and emergency room visits when a patient’s vital signs are good. The researchers hope that future versions of the device will watch for blood glucose levels, kidney failure, and oral, lung, and breast cancers.

The MouthLab prototype consists of a small, flexible mouthpiece like those that scuba divers use, connected to a hand-held unit about the size of a telephone receiver. The mouthpiece holds a temperature sensor and a blood volume sensor. The thumb pad on the hand-held unit has a miniaturized pulse oximeter — a smaller version of the finger-gripping device used in hospitals, which employs beams of light to measure blood oxygen levels. Other sensors measure breathing from the nose and mouth.

MouthLab also has three electrodes for electrocardiograms (ECGs) — one on the thumb pad, one on the upper lip of the mouthpiece, and one on the lower lip — that work about as well as the chest and ankle electrodes used on basic ECG equipment in many ambulances or clinics. The ECG signal is the basis for MouthLab’s way of recording blood pressure.

When the signal shows the heart is contracting, the device optically measures changes in the volume of blood reaching the thumb and upper lip. Unique software converts the blood flow data into systolic and diastolic pressure readings. A study found that MouthLab blood pressure readings effectively match those taken with standard, arm-squeezing cuffs.

The hand unit relays data by Wi-Fi to a nearby laptop or smart device, where graphs display real-time results. According to the Johns Hopkins team, patients will ultimately be able to send results to their doctors via cellphone.