Chest
Volume 106, Issue 4, October 1994, Pages 1188-1193
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Clinical Investigations in Critical Care
Modes of Mechanical Ventilation and Weaning: A National Survey of Spanish Hospitals

https://doi.org/10.1378/chest.106.4.1188Get rights and content

Little information exists regarding the proportion of patients treated with mechanical ventilation in intensive care units (ICUs), their underlying disease states, the modes of ventilation used, duration of ventilator support, methods and time required for weaning, and mortality in these patients. We carried out a cross-sectional multicenter study in 47 medical-surgical ICUs in Spain to investigate these issues in 290 patients who required mechanical ventilation for at least 24 hs. Relative frequency of different modes was as follows: assist-control ventilation (AC), 55%; synchronized intermittent mandatory ventilation (SIMV), 26%; pressure support ventilation (PSV), 8%; SIMV plus PSV, 8%; pressure-controlled ventilation (PCV), 1%; and continuous positive airway pressure (CPAP), 2%. Overall duration of mechanical ventilation was 27.1±1.1 (SE). A variety of techniques were used for weaning: T-tube trials, 24%; SIMV, 18%; PSV, 15%; SIMV plus PSV, 9%; and some combination of two or more methods in succession in 33% of the patients. Time required for weaning using a combination of SIMV and PSV was longer (17.8 days) than with other techniques (about 5 days, p<0.01). Time between initiation of weaning and removal of mechanical ventilation accounted for 41% of total ventilator time and was particularly high (59%) in patients with chronic obstructive pulmonary disease. Overall mortality rate was 34%, and it was higher in patients who were ventilated for 1 to 10 days than in those ventilated for a longer time. Despite the availability of several new modes of ventilator support, older modes such as AC and SIMV were more commonly used. Weaning constitutes a large portion of total ventilator time, and thus, measures that expedite the weaning process should markedly decrease the duration of mechanical ventilation.

Section snippets

METHODS

The study was performed in 47 ICUs in 47 teaching hospitals in Spain. All Spanish hospitals with more than 300 beds have an ICU, and 87% of the ICUs are multidisciplinary (medical-surgical) in nature, and their staff usually includes physicians who have specialized in critical care medicine. The technology available in Spanish ICUs is similar to that found in other European countries and the United States.

The survey was conducted on January 20, 1992, at 10 am. The characteristics of the survey

RESULTS

Six hundred thirty patients were in the ICUs when the survey was performed, and of these, 290 (46%) were receiving mechanical ventilation for at least 24 hs. Their age was 54.8±1.1 (SE) years, 66% were men, and 34% were women. The APACHE II severity score at the time of admission to the ICU was 17.9±0.4 (Table 1). Seventeen percent of the patients were admitted to hospitals containing less than 400 beds, 74% to hospitals with 400 to 1,000 beds, and 9% to hospitals with more than 1,000 beds. No

DISCUSSION

We surveyed all patients residing in 47 multidisciplinary ICUs in Spain on a single day. Of the 630 patients in an ICU at the time, 46% were receiving mechanical ventilation for at least 24 h. This substantiates the idea that one of the major functions of an ICU is to provide a location for the delivery of mechanical ventilation. The frequency of mechanical ventilation in our ICU population is very similar to that reported by Knaus7 in the only other multi-centered study of which we are aware.

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The Spanish Lung Failure Collaborative Group is composed of the following members: Drs. B. Alvarez; L. Blanch; J.L. Blanco; A. Bonet; L. Cabré; M.A. de la Cal; J. Cambronero; A. Diaz-Prieto; F. Fonseca; D. Fontaneda; M. Frutos; A. García; J. Gener; R. Ginestal; G. González; J. Gudin; J.E. Guerrero; M. Guirado; I. Honrubia; J.R. Iruretagoyena; F. Iturbe; A. Jareño; J. Jimenez; M. Lacort; F. Latorre; J.B. López-Messa; T.C. Martín; J.R. Martinez; P. Monedero; T. Muñoz; F. del Nogal; J. Nolla; E. Palazón; J.L. Pérez-Arancón; A. Pons; A. Reyes; M. Roig; M.A. Romera; J. Rubio; J.M. Serrano; J.F. Solsona; R. Suarez; F. Taboada; F. de la Torre; I. Vallverdú.

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