Physiological response to increasing levels of neurally adjusted ventilatory assist (NAVA).
This study evaluated the response to increasing levels of neurally adjusted ventilatory assist (NAVA), a mode converting electrical activity of the diaphragm (EAdi) into pressure, regulated by a proportionality constant called the NAVA level. Fourteen rabbits were studied during baseline, resistive loading and ramp increases of the NAVA level. EAdi, airway (Paw) and esophageal pressure (Pes), Pes pressure time product (PTPes), breathing pattern, and blood gases were measured. Resistive loading increased PTPes and EAdi. P(a)(CO)(2) increased with high load but not during low load. Increasing NAVA levels increased Paw until a breakpoint where the Paw increase was reduced despite increasing NAVA level. At this breakpoint, Pes, PTPes, EAdi, and P(a)(CO)(2) were similar to baseline. Further increase of the NAVA level reduced Pes, PTPes and EAdi without changes in ventilation. In conclusion, observing the trend in Paw during a ramp increase of the NAVA level allows determination of a level where the inspiratory effort matches unloaded conditions.
Service d'Accueil et de Traitement des Urgences, Hôpital Cochin, APHP, 75679 Paris, France. francois.lecomte@cch.aphp.fr
François
F
Lecomte
Lukas
L
Brander
Fredrick
F
Jalde
Jennifer
J
Beck
Haibo
H
Qui
Caroline
C
Elie
Arthur S
AS
Slutsky
Fabrice
F
Brunet
Christer
C
Sinderby
D000403:Airway Resistance; D000704:Analysis of Variance; D000818:Animals; D001784:Blood Gas Analysis / Q000379:methods; D003964:Diaphragm / Q000502:physiology*; D004947:Esophagus / Q000294:innervation / Q000502:physiology; D011817:Rabbits; D012121:Respiration, Artificial / Q000379:methods; D015656:Respiratory Mechanics / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013997:Time Factors; D014628:Vagotomy / Q000379:methods