Automatic selection of tidal volume, respiratory frequency and minute ventilation in intubated ICU patients as start up procedure for closed-loop controlled ventilation.
OBJECTIVE
Before a patient can be connected to a mechanical ventilator, the controls of the apparatus need to be set up appropriately. Today, this is done by the intensive care professional. With the advent of closed loop controlled mechanical ventilation, methods will be needed to select appropriate start up settings automatically. The objective of our study was to test such a computerized method which could eventually be used as a start-up procedure (first 5-10 minutes of ventilation) for closed-loop controlled ventilation.


METHODS
Prospective Study.


METHODS
ICU's in two adult and one children's hospital.


METHODS
25 critically ill adult patients (age > or = 15 y) and 17 critically ill children selected at random were studied.


METHODS
To stimulate 'initial connection', the patients were disconnected from their ventilator and transiently connected to a modified Hamilton AMADEUS ventilator for maximally one minute. During that time they were ventilated with a fixed and standardized breath pattern (Test Breaths) based on pressure controlled synchronized intermittent mandatory ventilation (PCSIMV).


RESULTS
Measurements of airway flow, airway pressure and instantaneous CO2 concentration using a mainstream CO2 analyzer were made at the mouth during application of the Test-Breaths. Test-Breaths were analyzed in terms of tidal volume, expiratory time constant and series dead space. Using this data an initial ventilation pattern consisting of respiratory frequency and tidal volume was calculated. This ventilation pattern was compared to the one measured prior to the onset of the study using a two-tailed paired t-test. Additionally, it was compared to a conventional method for setting up ventilators. The computer-proposed ventilation pattern did not differ significantly from the actual pattern (p > 0.05), while the conventional method did. However the scatter was large and in 6 cases deviations in the minute ventilation of more than 50% were observed.


CONCLUSIONS
The analysis of standardized Test Breaths allows automatic determination of an initial ventilation pattern for intubated ICU patients. While this pattern does not seem to be superior to the one chosen by the conventional method, it is derived fully automatically and without need for manual patient data entry such as weight or height. This makes the method potentially useful as a start up procedure for closed-loop controlled ventilation.
Laubscher
T P
TP
Hamilton Bonaduz AG, Switzerland.
Frutiger
A
A
Fanconi
S
S
Jutzi
H
H
Brunner
J X
JX
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002245:Carbon Dioxide / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D003199:Computer Systems; D003422:Critical Care; D006801:Humans; D007223:Infant; D007362:Intensive Care Units; D015278:Intensive Care Units, Pediatric; D007385:Intermittent Positive-Pressure Ventilation; D007442:Intubation, Intratracheal; D008875:Middle Aged; D010865:Pilot Projects; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012123:Pulmonary Ventilation / Q000502:physiology; D012119:Respiration / Q000502:physiology; D012121:Respiration, Artificial; D013990:Tidal Volume / Q000502:physiology
D002245:Carbon Dioxide