A ventilator requirement index.
OBJECTIVE
To determine the efficacy of vital capacity (VC) and a proposed ventilator requirement index (VRI) for justifying ventilator prescription and use for patients with neuromuscular/chest wall diseases (NMD).


METHODS
Prospective observational study in which 319 patients with NMD, including 187 ventilator users, were separated into four groups: (1) asymptomatic, (2) abnormal specific screening factors and/or symptomatic, (3) ventilator use 8-20 hrs/day, and (4) >20 hrs/day of ventilator use. The VRI was defined as 60 x Ti/(Ttot)2 x (Vt/VC) x RR, where Ti = inspiratory time of one breath (secs), Ttot = total time of one breath (secs), Vt = tidal volume (ml) at rest, VC = vital capacity (ml), and RR = respiratory rate.


RESULTS
The overall analysis of variance F-tests and post hoc pairwise contrasts were significant (P < 0.001) for differences in the VC and VRI across groups. Thus, VC and VRI are independent predictors of group membership. Satisfying VC or VRI criteria signaled the highest number of patients benefiting from ventilator use.


CONCLUSIONS
The prescription of one or two ventilators can be justified by both VC and VRI, with the combination being most sensitive.
Bach
John R
JR
Department of Physical Medicine and Rehabilitation, UMDNJ-New Jersey Medical School, Newark, New Jersey, USA.
Goncalves
Miguel
M
Eisenberg
Michal
M
Ishikawa
Yuka
Y
Altschuler
Eric
E
Winck
João Carlos
JC
Komaroff
Eugene
E
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009468:Neuromuscular Diseases / Q000150:complications*; D018579:Patient Selection; D011446:Prospective Studies; D012120:Respiration Disorders / Q000175:diagnosis*; D012121:Respiration, Artificial / Q000379:methods; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D035441:Thoracic Wall / Q000503:physiopathology; D014797:Vital Capacity