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performing chest physiotherapy act on newborn babies. First a chest physiotherapy technique is presented. Then, we explain the need of practitioners regarding ...
Proceedings of the 29th Annual International Conference of the IEEE EMBS Cité Internationale, Lyon, France August 23-26, 2007.

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Measurement System for Gesture Characterization During Chest Physiotherapy Act on Newborn Babies Suffering from Bronchiolitis L. Maréchal, C. Barthod, J. Lottin, G. Gautier and J. C. Jeulin

Abstract—Despite the lack of studies, chest physiotherapy (CPT) is widely used for newborn babies suffering from bronchiolitis. The limited data regarding this technique is mainly due to the difficulties making in situ measurements during the act. In the presented study, original instrumented gloves were designed and realized to perform measurements on babies during the CPT act. Custom-designed associated electronics and software were specially developed to monitor and record the forces applied by the physiotherapist's hands on the infant's chest and their trajectories. A prospective study, with babies in real situation, validates the principle measurement. Measurements with the system was led on babies in a referent physiotherapist consulting room between January and March 2007. The results are being analyzed and typical phases of the CPT act are highlighted.

I. INTRODUCTION

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O date, hardly any study concerning the characterization of infant chest physiotherapy has been achieved. The need of standard quantitative definition of CPT gesture expressed by physiotherapists is at the beginning of our study. This paper presents the method and the system for the characterization of the physiotherapist gesture when performing chest physiotherapy act on newborn babies. First a chest physiotherapy technique is presented. Then, we explain the need of practitioners regarding the definition and characterization of their gesture. In a third part, we describe the design of instrumented gloves that have been created. The system enables the measurement of the force applied by the physiotherapist on the infant and can also record the motion of the hands. Finally, we explain the methods chosen for the interpretation of this information, that will give a scientific definition of the gesture. II. CHEST PHYSIOTHERAPY A. Bronchiolitis management Bronchiolitis is an acute disease of the respiratory tract that affects young babies. This contagious illness occurs in epidemic periods from November to March. Health-care for such young patients is delicate. Drugs are advised against prescribing in the management of a first episode of bronchiolitis. In French-speaking European countries, the two consensus conferences, held in 1994 and 2000, concerning the management of bronchiolitis in infants have widely recommended the use of chest physiotherapy in order to provide care [1]. These techniques aim at generating forced respiration in order to improve bronchial pulmonary

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exchanges. More particularly in France, the forced expiration maneuver used is the Increase of Expiratory Flow technique (IEF). B. The IEF technique [2] IEF technique is a thoracic-abdominal movement generated by the hands of the physiotherapist on the infant's chest which must be synchronized at the beginning of his expiration. The infant being lain on a couch, the physiotherapist places one hand on the thorax close to the neck and the other hand on the abdomen. The “thoracic hand” presses with its cubital part whereas the “abdominal hand” has a global support. According to expert physiotherapists, the distribution of the force applied by the practitioner with his “thoracic hand” has to be uniform from the fingers to the hypothenar eminence. The hands must never leave the contact with the skin and also not slip or stretch it. The directions of the resulting forces have to be parallel to the arms and perpendicular one to each other; they cross between the 7th and the 8th dorsal vertebra (Fig. 1). The applied pressure sequences must be synchronized with the infant respiratory cycle.

Fig. 1. Increase of Expiratory Flow technique : IEF [3].

The mechanical deformation of the lungs produces an increase of the pressure inside the alveoli. Fausser and Postiaux suggest that the gradient of the pressure between the alveoli and the mouth (Patm) generates a circulation of the air with a turbulent flow. This flow would be able to mobilize the mucus secretions and participate to the airway clearance [3] ,[4]. Besides, the sound of the airflow produced inside the airways is slightly linked to the nature and the location of the secretions [4]. Thus, the physiotherapist relies his practicing on his own perception. He adapts and controls the magnitude and the frequency of the gesture versus the sound and the sense of touch to change the increase of the produced flow. Furthermore, he must prevent from collapsing the bronchi and bronchioles. The major indicator of success is the remove of the

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secretions up to the trachea and the expectoration of them. III. ASSESSMENT OF NEEDS A. An empiric technique These last years, due to management with the IEF technique, results have shown an improvement of the clinical evolution of babies' health preventing many of them from reaching the critical state of the hospitalization [5]. Consequently, the CPT act is more and more used and the efficiency of this physiotherapy technique is now currently admitted in France. However, it has never been the subject of any scientific assessment. Although the IEF technique requires a good know-how. Expert physiotherapists, who are skilled in doing the IEF technique, have learnt the gesture from experience for many years. They had an empiric approach. As described by Fausser [2], a qualitative protocol for the IEF technique as been defined but no quantitative definition has been made to prove the efficiency or to characterize the gesture. B. Needs to quantify IEF technique Therefore, scientific measurement resources to define the technique appear essential for several reasons: Firstly, the IEF act is impressive for the parents, at a glance, since the gesture is dynamic and also appears different when performed by different physiotherapists. So, the harmonization of this technique has all the more become a real need as it contributes to put the parents' mind at rest. Secondly, if not well performed, this technique may be dangerous for the baby [6]. Indeed, if the physiotherapist applies a too important force, the thorax strain can induce the closing of the small respiratory tract, or worse he may hurt the infant. At the opposite, if too little pressure is applied, the gesture then is inefficient. Finally, the IEF technique is not recognized apart from French-speaking countries because of the lack of scientific evidences regarding its efficiency. Even among French expert physiotherapists, different perceptions and feelings when performing CPT can be discussed. Yet, if for newborn babies and for infants, mechanical characteristics of rib-cage (including lungs and ribs) are well-known [7], the values of pressure that the practitioner applies on the thorax to obtain a better expectoration of the secretions are still unknown. It is thus compulsory to quantify the limits of the applied forces, the frequency and the length for applying the gesture to obtain the expected effect. The formalization of the gesture, thanks to the measurement, will afford the physiotherapy community to have new elements in order to discuss further about the management of infants suffering from bronchiolitis. This might also bring a legitimacy to the IEF technique if the results show a link a between better respiration and efficient gesture. C. Education in physiotherapy For the time being, training courses are academic and then

the technique is practiced on baby dolls. So, when expert physiotherapists have to practically teach the gesture to inexperienced practitioners or students, they often have to face hardships. In order to have a didactic approach when learning the IEF maneuver to physiotherapist students, the need of a realistic tool for learning seems to be essential so that they may train. Health-professionals are also convinced that adhering to such a paradigm is much better than either an academic course in class or learning the gesture directly on babies in real situation. In the first situation, the student is too far from reality. In the second one, new practitioners must psychologically handle their emotions instead of concentrating themselves on the gesture and can't discern all the details. They usually don't apply enough force being afraid of injuring the baby. D. Expectations Thus, with the growth in demand for training from the physiotherapy's community, it was decided to quantitatively define the gesture in order to enhance learning. The basic gesture of the IEF technique will be analyzed. Useful parameters to be measured will also be defined and discussed. The measurement could set up a scientific base on which the teacher might rely on for education. In this study, JC Jeulin is the expert physiotherapist involved in our tests. His gesture is said to be “the good gesture”. It is efficient since he has a long experience in CPT and in the IEF technique and obtains convincing results with his young patients. IV. DEVICES AND METHODS As far as the measurement of the force applied by the physiotherapy practitioner is concerned, it has been decided to instrument the physiotherapist's hands and not the infant's thorax because of two reasons: first in order to realize measurements independently of the infant's morphology; secondly, in order to avoid making coercive measurements on newborn babies who may be dithered and then grip the system. Thus, the measurement system must be thin, flexible and painless for the baby. It should neither modify the physiotherapist’s gesture nor being cumbersome or disturbing for the infant. So, instrumented gloves were designed to measure two relevant physical parameters [8]: the space displacement of the hands and the distribution of the force applied by the hands on the infant’s chest. A. Force measurement Since the force applied by the practitioner is as well quasistatic as dynamic, Force Sensing Resistor sensors (FSR) were chosen. FSR are polymer thick film (PTF) devices which exhibit a decrease in resistance with an increase in the force applied to the active surface [10]. These piezoresistive sensors were provided by Interlink Electronics among manufacturers. After an exhaustive study of different sensors [9], we have chosen the most appropriate one as far as their

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size and cost are the lowest, for equivalent technical properties. Such sensors have already been used to measure forces developed by the human hand when gripping objects [11], [12], [13]. The sensors are glued on a cotton glove by an adhesive band (supplied by 3M). The relevance of the measurements lies in the sensors positions. They have been determined after several tests according to the referent physiotherapist, so that the most interesting pressures applied during the IEF act can be seen and measured. Hence the positions of the sensors are different for both instrumented gloves. Concerning the “thoracic glove”, nine FSR are placed on the edge of the hand and six on the palm for the “abdominal glove”. Regarding hygiene and medical environment, a thin medical latex glove is worn over the instrumented glove so that the sensors are not directly in contact with the skin of the toddler.

B. Hand trajectories measurement The measurement of the position of the hands of the physiotherapist is performed thanks to a six-degree of freedom electromagnetic tracking device, the Flock of Birds (FOB, from Ascension Technology). The device is composed of one transmitter and two receivers. Each receiver is placed on the cotton gloves on the upper side of the back of each hand (Fig. 4). The origin of the coordinates is the local coordinate centered inside the transmitter. The relative linear and angular positions of the receivers are computed simultaneously. The measurement is performed at 103 Hz which is the default sampling rate recommended by the manufacturer. Signal conditioning and processing are done by a unit dedicated to the sensor, connected to a computer by a RS-232 interface. Measurements are acquired by the specific software “Winbird”.

Fig. 4. System components. Fig. 2. Instrumented gloves; left: thoracic, right: abdominal.

Each sensor is inserted in an inverted amplifier in order to obtain an output voltage signal which varies with applied forces. The sensors' signals are digitalized with an analog to digital converter (ADC). This is processed with a 16 channels DAQ card (from National Instrument) inserted in a laptop. The signal conditioning unit is compact and easily wearable on the pants of the user. A static calibration was done with dead loads in range of 0.1 kg to 1 kg. For each sensor, a regression curve was calculated to fit the calibration data (Fig. 3). The calibration gives the part-to-part repeatability but is not able to provide the absolute force magnitude during the measurement on newborn babies because in vivo calibration can not be correctly implemented.

C. Data processing We have specifically designed a software in G language (LabVIEW) that samples the signals at 200 Hz. This frequency is well-adapted for real time visualization and motion analysis (Fig. 5). The software allows to see the pressure distribution on the two gloves via colour scales corresponding to the relative magnitude of the applied force. Moreover, the practitioner may have a real-timed feedback on the screen, more precisely concerning the balance of the forces he applies during his gesture. The data is also recorded for retrospective analysis.

Fig. 5. Gloves visualization software.

V. FIRST RESULTS

Fig. 3. Example: FSR1 calibration curves.

The measurement with the whole system was performed in a physiotherapist consulting room from January to March 2007. The study was managed taking into account a

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population of 25 infants aged from 5 to 7 months suffering from bronchiolitis. This random trial was performed by the same expert physiotherapist, J.C. Jeulin. A. Force measurement results During infants management, the physiotherapist can perform three different sequences: “slow IEF”, “fast IEF” and “fast double IEF” depending on the clinical state. For each, Fig. 6 shows the sensors responses acquired on the thoracic hand glove during two compressions on the chest of a 5-month-old infant. The nine FSR responses evolve synchronously. For “slow IEF”, the magnitudes of the forces increase linearly until reaching a maximum value and then decrease. “Fast IEF” and “fast double IEF” present a plateau at the maximum value. Both are repeatable since the rising time of the applied pressure and the magnitude of the forces remain constant for each compression. On Fig. 6(c), the twotime compression phase performed by the practitioner is clearly seen. (a)

(b)

as the referent one by the practitioner.

Fig. 7. Trajectory of the FOB receiver placed on the thoracic hand.

VI. CONCLUSION The IEF referent gesture has been described according to expert physiotherapists. The measurement system, designed and realized to record applied pressure and hands displacement during the act, has been validated. The first results obtained are reproducible and enable a discrimination of the different gesture sequences. Besides, the recordings agree with the physiotherapist feelings. The analyze of the measurement will bring out characteristic parameters. The analyze of the data concerning simultaneously the applied forces and the thorax displacement will afford a quantitative definition of the IEF gesture. We prospect for doing further measurements with a microphone to record the sounds of the lungs in order to discuss about the IEF efficiency. REFERENCES [1] [2] [3] [4]

(c) [5]

[6]

[7] [8] Fig. 6. FSR response. (a) “slow IEF”; (b) “fast IEF”; (c) “fast double IEF”.

B. Position measurement results Simultaneously to force measurements, the trajectories of the hands are recorded with the FOB sensors located on the gloves (Fig. 5). The displacement of the thoracic hand in the X-Z plane – defined in Fig. 1 – during one compression of a “fast IEF” is reported on Fig. 7. The displacement of the hand is almost the same in the two directions. These first results are consistent with the gesture qualitatively described

[9] [10] [11]

[12]

[13]

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ANAES, “Consensus conference of Management of bronchiolitis in infants,” Arch.Ped2001, September 2000. C. Fausser, V. Breheret and D. Lopes, “Augmentation du flux expiratoire (AFE) et tolérance,” KS, no. 428, p. 21, December 2002. C. Vinçon, C. Fausser, “Kinésithérapie respiratoire en pédiatrie. Du prématuré au petit enfant,” Elsevier Masson, 1993. G. Postiaux, “Kinésithérapie respiratoire de l’enfant,” Ed.DeboeckUniversité, 1998. G. Postiaux, R. Dubois, E. Marchand, M. Demay, J. Jacquy, AM Mangiaracina, “Effets de la kinésithérapie respiratoire associant Expiration Lente Prolongée et Toux Provoquée dans la bronchiolite du nourrisson,” Kinesither. Rev. 2006;(55):35-41. M. Chalumeau, L. Foix-L'Helias, P. Scheinmann, “Rib fractures after chest physiotherapy for bronchiolitis or pneumonia in infants,” Pediatr Radiol, 32(9): 644-7, September 2002 J. Stocks, P. Sly, R. Tepper, W. Morgan, “Infant respiratory function testing,” Weiley-Liss, 1996. C. Barthod, G. Gautier, L. Goujon, J. C. Jeulin, “L'apport de l'instrumentation dans la formation et la pratique de la kinésithérapie respiratoire du nourrisson,” ReK, n°4, pp. 49-56, June 2006. L. Maréchal, “MIKROB,” engineer report, Savoie University, 2005. Interlink, “Force Sensing Resistor Integration Guide,” 2004. F. Vecchi, C. Freschi, S. Micera, A. M. Sabatini, P. Dario, “Experimental evaluation of two commercial force sensors for applications in biomechanics and motor control,” Proc IFESS Conf, Aalborg (DK), June 17--23, 2000. M. C. F Castro and A. Cliquet, Jr, “A low-cost instrumented glove for monitoring forces during object manipulation,” IEEE Trans. Rehab. Eng., vol. 5, no. 2, June 1997. Nikonovas, A. J. Harrison, S. Hoult and D. Sammut, “The application of force-sensing resistor sensors for measuring forces developed by the human hand,” Proc. I. Mech. E., Part H Vol. H pp 121-126