A Low-Cost, Ear-Contactless Electronic Stethoscope Powered by Raspberry Pi for Auscultation of Patients With COVID-19: Prototype Development and Feasibility Study

Abstract

Background: Chest examination by auscultation is essential in patients with COVID-19, especially those with poor respiratory conditions, such as severe pneumonia and respiratory dysfunction, and intensive cases who are intubated and whose breathing is assisted with a ventilator. However, proper auscultation of these patients is difficult when medical workers wear personal protective equipment and when it is necessary to minimize contact with patients.

Objective: The objective of our study was to design and develop a low-cost electronic stethoscope enabling ear-contactless auscultation and digital storage of data for further analysis. The clinical feasibility of our device was assessed in comparison to a standard electronic stethoscope.

Methods: We developed a prototype of the ear-contactless electronic stethoscope, called Auscul Pi, powered by Raspberry Pi and Python. Our device enables real-time capture of auscultation sounds with a microspeaker instead of an earpiece, and it can store data files for later analysis. We assessed the feasibility of using this stethoscope by detecting abnormal heart and respiratory sounds from 8 patients with heart failure or structural heart diseases and from 2 healthy volunteers and by comparing the results with those from a 3M Littmann electronic stethoscope.

Results: We were able to conveniently operate Auscul Pi and precisely record the patients' auscultation sounds. Auscul Pi showed similar real-time recording and playback performance to the Littmann stethoscope. The phonocardiograms of data obtained with the two stethoscopes were consistent and could be aligned with the cardiac cycles of the corresponding electrocardiograms. Pearson correlation analysis of amplitude data from the two types of phonocardiograms showed that Auscul Pi was correlated with the Littmann stethoscope with coefficients of 0.3245-0.5570 for healthy participants (P<.001) and of 0.3449-0.5138 among 4 patients (P<.001).

Conclusions: Auscul Pi can be used for auscultation in clinical practice by applying real-time ear-contactless playback followed by quantitative analysis. Auscul Pi may allow accurate auscultation when medical workers are wearing protective suits and have difficulties in examining patients with COVID-19.

Trial registration: ChiCTR.org.cn ChiCTR2000033830; http://www.chictr.org.cn/showproj.aspx?proj=54971.

Keywords: COVID-19; Python; Raspberry Pi; auscultation; digital health; ear-contactless; low-cost; phonocardiogram; stethoscope.

Figure 1

A medical staff member nursing a patient with COVID-19 in Wuhan, China. The staff member’s protective clothing prevents the use of a conventional stethoscope.

Figure 2

Flowchart of Auscul Pi design based on the evaluation of 7 dimensions in comparison with a conventional stethoscope and 3M Littmann digital stethoscope. Thick solid arrows indicate that the stethoscope performed satisfactorily on the indicated dimension; dashed arrows indicate that it did not.

Figure 3

Schematic of the connections within the Auscul Pi system. (A) Raspberry Pi 3 Model B+. (B) Microspeaker. (C) USB collar microphone. (D) Uninterruptible power supply battery expansion board with two rechargeable batteries (18650). (E) 3.5-inch touch screen. (F) Chest piece from a conventional stethoscope. CPU: central processing unit.

Figure 4

The Auscul Pi prototype. (A) The uninterruptible power supply. (B) The Raspberry Pi system (left) and uninterruptible power supply (right). (C) Combination of the Raspberry Pi and the power supply. (D) A microphone connected to the chest piece from a conventional stethoscope, 3.5-inch touch screen, Raspberry Pi with power supply, and microspeaker. (E) Fully assembled device containing the components in D.

Figure 5

(A) Digital NumPy files (.npy) and (B) Waveform Audio File Format files (.wav) generated by Auscul Pi. The file names indicate the date and time of each measurement.

Figure 6

The graphical user interface on the touch screen of Auscul Pi. (A) The desktop display. The user can double-tap the Auscul Pi icon to run the program. The recorded data are stored in the AudioData folder. (B) The manipulation interface of the Auscul Pi Console after double-tapping the Auscul Pi Console icon. The user can control the auscultation and replay by tapping the “Auscultate” and “Replay” buttons, respectively.

Figure 7

Electrocardiogram and phonocardiograms of healthy volunteer 9 generated by the 3M Littmann stethoscope and Auscul Pi, showing normal sinus rhythms and normal heart sounds. ECG, electrocardiogram: S1: first heart sound; S2: second heart sound.

Figure 8

Electrocardiograms and phonocardiograms of patient 8, showing systolic murmurs before cardiac surgery to treat a ventricular septal defect but no murmurs after surgery. ECG: electrocardiogram; m: murmur; S1: first heart sound; S2: second heart sound.