In a situation of respiratory failure (RF), patients show signs of increased work of breathing leading to the involvement of accessory respiratory muscles and a desynchronization between rib cage and abdomen known as thoraco-abdominal asynchrony (TAA). Proper assessment of these signs requires sufficiently skilled and trained medical staff. However, human assessment is subjective and is practically impossible to audit. A new non-contact method is proposed for TAA visualization and quantification, in children with RF. The surface variations are analyzed by calculating the 3-dimensional motion of the thorax and abdomen regions during the breathing process. A high-fidelity mannequin was used to simulate thoraco-abdominal asynchrony. The proposed system uses depth information recorded by an RGB-D (Red Green Blue-Depth) camera. Furthermore, surface displacement was calculated in four simulated modes from the normal to the severe TAA mode. Respiratory rates were also calculated based on the analysis of the surface movements. The proposed method was compared to a highly precise laser-ranging system with 1 mm resolution. The resulting root mean square deviation (RMSD) showed an error of 1.78 ml in normal mode, 2.83 mm in mild mode, 2.23 mm in severe mode and 2.34 mm in irregular mode. The results showed a high correlation between the two methods in estimating the retraction distance and respiratory rate (ρ >0.985).

Introduction

In a clinical environment, breathing monitoring is an important vital task that is done on a daily basis for patients of all ages. Breathing monitoring mainly comprises an assessment of the chest wall motion and the measurement of physiological signs such as respiratory rate and tidal volume. While many methods have been developed for physiological parameters assessment, there is still a lack of methods to better assess the chest wall spatial motion in spontaneous breathing patients. Chest wall motion assessment, in clinical practice, is currently based on intermittent human observation of the rib cage and abdominal compartments and is done through physical examinations. In fact, visual inspection is the first tool in physical examinations. This initial assessment allows the early detection of a potential respiratory failure in order to provide the appropriate medical treatment to the patient. In case of respiratory failure, determining the severity is a key factor to help the clinician to make the right decision, whether by providing an immediate oxygen support and possibly bagand-mask ventilation or even patient intubation and mechanical ventilation to provide full or partial breathing support. Chest wall distortion, known as thoraco-abdominal asynchrony or paradoxical motion, is one of the most important clinical symptoms of respiratory failure [1]–[۳]. This clinical sign is visually inspected by the physician. However, the accuracy of this inspection is highly correlated to the clinician’s expertise. The interpretations of a patient’s results are thus, limited by high inter-observer variation.