PHYSIOLOGICAL-EFFECTS AND OPTIMIZATION OF NASAL ASSIST-CONTROL VENTILATION FOR PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE IN RESPIRATORY-FAILURE
C. Girault et al., PHYSIOLOGICAL-EFFECTS AND OPTIMIZATION OF NASAL ASSIST-CONTROL VENTILATION FOR PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE IN RESPIRATORY-FAILURE, Thorax, 52(8), 1997, pp. 690-696
Background - A study was undertaken to investigate the effects of non-
invasive assist-control ventilation (ACV) by nasal mask on respiratory
physiological parameters and comfort in acute on chronic respiratory
failure (ACRF). Methods - Fifteen patients with chronic obstructive pu
lmonary disease (COPD) were prospectively and randomly assigned to two
non-invasive ventilation (NIV) sequences in spontaneous breathing (SB
) and ACV mode. ACV settings were always optimised and therefore subse
quently adjusted according to patient's tolerance and air leaks. Resul
ts - ACV significantly decreased all the total inspiratory work of bre
athing (WOBinsp) parameters, pressure time product, and oesophageal pr
essure variation in comparison with SB mode. The ACV mode also resulte
d in a significant reduction in surface diaphragmatic electromyographi
c activity to 36% of the control values and significantly improved the
breathing pattern. SB did not change the arterial blood gas tensions
from baseline values whereas ACV significantly improved both the Pao(2
) from a mean (SD) of 8.45 (2.95) kPa to 13.31 (2.15) kPa, Paco(2) fro
m 9.52 (1.61) kPa to 7.39 (1.39) kPa, and the pH from 7.32 (0.03) to 7
.40 (0.07). The respiratory comfort was significantly lower with ACV t
han with SB. Conclusions - This study shows that the clinical benefit
of non-invasive ACV in the management of ACRF in patients with COPD re
sults in a reduced inspiratory muscle activity providing an improvemen
t in breathing pattern and gas exchange. Despite respiratory discomfor
t, the muscle rest provided appears sufficient when ACV settings are o
ptimised.