In order to diagnose respiratory diseases, clinicians typically examine the thorax by feeling and listening to the patient. However, this examination can be subjective, depending on the clinician’s experience level and their own sensory perceptions.

To make diagnosis more effective, an airborne ultrasound surface motion camera (AUSMC) has been designed to map sound vibrations associated with respiratory conditions, according to a new pilot study published in AIP Advances.

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

As the authors note, clinicians have used various methods to detect respiratory disease in patients. These include palpation, which evaluates the transmission of high-frequency vibrations produced by vocalizations, and auscultation, which evaluates the transmission of sound vibrations produced by the lungs during inspiration and expiration. For example, a patient may have localized pneumonia if a tubal murmur is detected through auscultation.

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

 

In the new approach described by the study, however, researchers turned to the AUSMC to map vibrations produced by vocalizations, bringing specificity, rather than subjectivity, to the examination. The AUSMC’s goal is to ensure that the findings are “quantifiable, reproducible, and archivable,” the authors say. 

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

The study included 77 healthy volunteers—37 men, 37 women, and three unspecified—whose thoracic vibrations were successfully mapped using AUSMC. The subjects had no history of chronic disease and no acute disease at the time of the study; they were also non-smokers or smokers with less than two pack years.

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

During the study, the authors say, “The participants were first trained to reproducibly inhale up to their total lung capacity (TLC) with the help of spirometry-based feedback. During the ultrasound acquisitions, they stood about 70 cm away from the ultrasonic array, turning their back on it."

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

"They were asked to inflate their lungs to TLC, from which they had to produce a steady vocalization for a few seconds (/a/, /o/, or /z sound). Meanwhile, the AUSMC system was set to record the surface motion for about 3 s[econds]. No specific instruction was given regarding voice pitch, assuming the participants would vocalize at their ‘natural’ pitch. Most acquisitions were performed with arms crossed for scapula to be located on the sides of the back," continue the authors.

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

The findings showed that the contactless mapping device could detect, map, and record vocalization-driven vibrations over the entire surface of the participants’ thoraxes.

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

 

Further, the authors note that some vibrations differed by gender. They note that the vibration barycenter cluster (referring to the center of mass) “below 200 Hz…mostly corresponds to male subjects, whereas the barycenter cluster beyond 200 Hz…mostly corresponds to female subjects.” This is visualized in a diagram included in the study. 

Airborne ultrasound for the contactless mapping of surface thoracic vibrations during human vocalizations: A pilot study. AIP Publishing.

 

“We believe that the data that we present are sufficient to pursue the evaluation of the AUSMC as a putative future diagnostic tool,” the authors write. Clinical trials involving the AUSMC are ongoing. 

Mathieu Couade, study author and Chief Scientific Officer of AUSTRAL Diagnostics, says that this sort of technology can help clinicians act fast in a real-world setting. He says, for example, that clinicians are using the technology to develop a device that can help emergency room physicians detect acute dyspnea in patients. 

“As the machine can image both the lungs and the heart, we think the device will be able to determine the root cause of dyspnea, which can be cardiac or pulmonary,” Couade says. “Getting this information faster is critical, as the emergency departments are nowadays often saturated. We think we could shorten this time drastically by avoiding unnecessary exams. [There’s] no need to image both lungs [and] heart if you already know if it is cardiac- or lung-related.” He says that the goal is to clinically validate the efficacy of this sort of device—and to develop the scanner for use in the emergency room.