Résumé
La PAV+ (proportional assist ventilation with load-adjustable gain factors) et la NAVA (neurally adjusted ventilatory assist) sont deux nouveaux modes de ventilation qui délivrent une assistance proportionnelle à l’effort instantané du patient et à un facteur de proportionnalité réglé par le clinicien. Les signaux physiologiques utilisés afin de détecter l’effort du patient sont cependant très différents: la PAV+délivre une pression proportionnelle aux volume et débit instantanés et à la charge imposée au système respiratoire; en NAVA, la pression délivrée est proportionnelle à l’activité électrique du diaphragme recueillie au moyen d’un cathéter oesophagien muni d’électrodes. Dans les deux cas, le caractère proportionnel de l’assistance entraîne une amélioration des interactions patient-ventilateur par différents mécanismes: le ventilateur s’adapte mieux à la demande instantanée du patient, le patient modifie très rapidement son effort en fonction du niveau d’assistance afin de maintenir un volume courant désiré, la variabilité naturelle cycle à cycle est respectée, enfin le cyclage expiratoire est proche du temps inspiratoire neural du patient. Le risque d’hyperinflation dynamique est alors limité et les asynchronies sont rares. De plus, chaque mode permet des interactions et des modalités de monitorage du couplage neuroventilatoire supplémentaires propres à son fonctionnement. Cependant, bien que ces modes soient prometteurs et suscitent un intérêt croissant, la manière de les régler reste encore un sujet d’investigation. Ils devront, par ailleurs, montrer leur bénéfice en clinique au cours d’essais randomisés avant d’envisager leur diffusion.
Abstract
Proportional assist ventilation with load-adjustable gain factors (PAV+) and neurally adjusted ventilatory assist (NAVA) are new ventilatory modes where assistance is delivered in proportion to the instantaneous respiratory effort and to a proportionality factor set by the clinician. However, the physiological signal used by the ventilator to detect the patient’s effort is different between these two modes. PAV+ delivers assistance in proportion to instantaneous flow as well as volume and respiratory load. In NAVA, the airway pressure is provided in proportion to diaphragm electrical activity, recorded using an esophageal catheter with an electrode array. The proportionality of the assistance allows an improvement in patient-ventilator interactions with both modes, due to several mechanisms: the ventilator adapts the amount of pressure delivered according to the instantaneous patient’s demand, the patient rapidly adjusts his own effort to receive a target tidal volume, the natural respiratory variability is respected, and the cycling off is closed to the neural inspiratory time. In these conditions, dynamic hyperinflation cannot occur and there are few patient-ventilator asynchronies. Furthermore, according to their properties of functioning, each mode allows additional interactions and neuro-ventilator coupling monitoring. However, although these modes are promising, how to adjust the proportionality factor is still a matter of research. These ventilatory modes must also demonstrate their benefit in clinical randomized trials before being considered for a widespread clinical use.
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Carteaux, G., Brochard, L. Nouveaux modes ventilatoires: PAV+ et NAVA. Réanimation 20, 41–48 (2011). https://doi.org/10.1007/s13546-010-0003-7
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DOI: https://doi.org/10.1007/s13546-010-0003-7
Keywords
- Proportional assist ventilation with loadadjustable gain factors
- Neurally adjusted ventilator assist
- Assisted mechanical ventilation