Multidimensional Characterization of Dyspnea in Children

Introduction Breathing is most of the time an activity realized ion an automated way. In various situations however, it can be "felt", for example when people are producing an effort. To term used to refer to these situation is "breathlessness". When breathing is perceived as an unpleasant sensation, causing suffering, especially in the context of diseases that are often of cardiac or respiratory origin, the appropriate term is "dyspnea".

In 1999, a consensus conference defined dyspnea as a subjective experience of respiratory discomfort consisting in sensations of distinct quality and varying intensity.

Sensory and emotional aspects associated to dyspnea have been compared to those observed in pain. Pain is often defined according to its intensity, quality and temporal evolution of its sensory dimension, but also according to the emotional response it induces. There are similarities between pain and dyspnea, two unpleasant sensations sharing common physiological substrates. Two studies have previously demonstrated that there is an overlap between cerebral regions activated during pain and those activated when dyspnea occurs. This is in favor of analyzing dyspnea according to the same sensory and emotional dimensions as pain.

To those intrinsic sensory characteristics are added psychological, social and economic factors that may have an influence, positively or negatively, on the sensation of dyspnea.

Scientific background Dyspnea is multifactorial and multidimensional. Its multidimensional nature can be apprehended using specific tools and questionnaires designed to this effect. Among them, the Dyspnoea-12, the Multidimensional Dyspnea Profile (MDP) ans the Respiratory Distress Observation Scale (RDOS). These scales take into account not only the intensity of dyspnea, but also its sensory qualities and affective dimension, which can vary independently from one another. All these scales have already been validated in French language.

The RDOS The RDOS is an hetero-questionnaire divided in 8 items: respiratory rate, heart rate, restlessness (non-purposeful movements), accessory muscle use (rise in clavicule during inspiration), grunting at end-expiration (guttural sound), Nasal flaring (involuntary movement of nares) and look of fear. Each item is scored between 0 (absence) and 2 (presence) points.

The MDP The MDP, which has already been validated in French speaking language, is a self report questionnaire including 11 items, each one evaluated by a scale ranging from 0 to 10, describing the intensity, sensory and emotional characteristics of dyspnea. The MDP score can be analyzed in terms of immediate perceptual response, emotional response or affective dimension, similarly to models applied to pain.

The MDP isn't defendant on physiological variables changing with age that is why the scale validated in adults will be used for children aged between 12-18 years. A simplified MDP will be used for children aged between 6-12 years.

RDOS and MDP in the clinical set-up In adults, the MDP has previously been used to evaluate dyspnea in patients with chronic bronchopulmonary dysplasia (COPD) or Amyotrophic lateral sclerosis (ALS). Is has allowed a better comprehension of the impact of dyspnea on patients' quality of life. It has also been used to evaluate the efficacy of various therapeutic interventions, such as respiratory rehabilitation in COPD patients.

However, the MDP requests adequate communication skills and mastering the vocabulary. This is an obstacle in younger children and, more broadly, in non-communicative patients. The RDOS has been develop to allow an hetero-evaluation of dyspnea in palliative care patients unable to communicate and describe their symptoms. This scale has also demonstrated A good correlation to the visual analogue scale-dyspnea and with the clinical evolution of patients in palliative care.

This scale has latter been adapted to patients un intensive care (IC-RDOS) and mechanically ventilated patients (MV-RDOS). It could easily be used in children; however, physiological variables used in the RDOS would need to be adapted to different age groups. A RDOS-infant score has recently been developed for newborns, including the observation of inter-costal and supra-sternal retractions, cyanosis and capillary perfusion. Once more, this score has been developed for newborns only. Moreover, it does not take into account the observation of fearful expressions which could be an important parameter in the evaluation of dyspnea in older children.

Dyspnea in children Various diseases can be responsible for chronic respiratory insufficiency and cause chronic dyspnea, among them cystic fibrosis, primary ciliary dyskinesia, interstitial lung diseases and neuromuscular diseases.

Acute dyspnea is also a frequent cause of hospitalizations, especially when secondary to acute respiratory infections, asthma attacks or acute decompensation of a chronic respiratory disease. Dyspnea can be evaluation by the VAS-dyspnea. In asthmatic patients, it has been shown that this scale allows a good evaluation of bronchial constriction and a good sensitivity to therapeutic interventions. The childhood asthma score (CAS) and preschool respiratory assessment measure (PRAM) score are also commonly used to evaluate the severity of asthma attacks. However, they are unidimensional scales only validated for asthmatic children.

There is no existing scale validated in children providing a multidimensional evaluation of dyspnea, whether it be acute or chronic.

Dyspnea-VAS can be used, but it is a unidimensional scale which does not allow the evaluation of dyspnea's sensory and affective dimensions.

Hypothesis is that using multidimensional evaluation scales for dyspnea, such as the MDP, simplified MDP and RDOS could allow for a reliable evaluation of dyspnea in children aged between 6-18 years.