A Prospective Comparison of IMV and T-Piece Weaning from Mechanical Ventilation

doi:10.1378/chest.96.2.348

Chest

Volume 96, Issue 2, August 1989, Pages 348-352

https://doi.org/10.1378/chest.96.2.348 Get rights and content

Two hundred (200) consecutive medical and surgical patients requiring mechanical ventilation were entered into a prospective randomized trial of weaning by either intermittent mandatory ventilation (IMV) or T-piece. Patients in these groups were of similar age and sex and had the same total ventilation time (TVT). The study design provided equal time for each weaning mode after specific criteria for oxygenation and ventilation were satisfied (PaO₂ >55 mm Hg on FIo₂ <0.5; VE <12 L/min and two of the following four parameters: MVV >2 VE, VT >5 ml/kg, FVC >10 ml/ kg, NIF ≤ – 20 cm H₂O). Of the original 200 patients 165 were entered into the weaning phase; 35 patients were withdrawn prior to weaning due to the discretion of the attending physician or protocol error. Weaning time was not different between the IMV (5.3 ± 1.2 h, mean ± SEM) and T-piece groups (5.9 ± 1.4 h, p = NS). Of the 165 patients, 155 (93 percent) were weaned successfully by protocol, 79 in the IMV and 76 in the T-piece group. Of 155 patients, 136 (88 percent) were weaned on the first attempt by protocol. Of the 19 who were not weaned, 11 were weaned successfully on the second and five on the third trial; three patients required three-day weans. We conclude that clinically stable patients who require short-term mechanical ventilation and meet standard bedside weaning criteria can be weaned efficiently by protocol using either IMV or T-piece techniques. (Chest 1989; 96:348–52)

IMV = intermittent mandatory ventilation; TVT = total ventilation time; MW = maximum voluntary ventilation; NIF = negative inspiratory force; AMV = assisted mandatory ventilation; WT = weaning time

Section snippets

Patient Population

Over a 16-month period all adult patients requiring mechanical ventilation at the three hospitals in the Medical University of South Carolina system (Medical University Hospital, Charleston Veterans Administration Medical Center, and Charleston Memorial Hospital) were randomized into two groups following informed consent. All patients were ventilated with the same ventilator, a Bennett MA-1 (Puritan-Bennett Corp). IMV was administered with an H valve replacing the 9200 demand valve for the IMV

RESULTS

Two hundred (200) patients were initially enrolled in the study. The mean age was 53 years (range, 18 to 87) with 134 males and 66 females. Of the 200 patients, 133 were ventilated following surgery or trauma and 67 patients were ventilated for medical diseases (Table 2). There was no difference in age between patients in the IMV and T-piece groups.

One hundred sixty-five (165) (82 percent) of the patients were maintained in the study until the weaning phase was initiated, and 155 of the 165 (93

DISCUSSION

This study showed that both medical and surgical patients assigned randomly to either an IMV or T-piece mode could be weaned from mechanical ventilation over the same period. Two-thirds of the patients who were weaned in 2 h were postsurgical patients who were ventilated for <72 h. The majority of these patients had undergone uncomplicated coronary artery bypass grafting (CABG) and usually were weaned as soon as they awoke from anesthesia. This represents a group of patients that usually

ACKNOWLEDGMENT

The authors wish to thank the faculty and housestaff of the Medical University of South Carolina and the Department of Respiratory Therapy for their support, Dr. Boyd Loadholt for assistance in statistical analysis, and Louisa Freeman and Jeanne Jaeger for secretarial support.

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Cited by (52)

Weaning from mechanical ventilation: Why are we still looking for alternative methods?
2013, Medicina Intensiva
La mayoría de los pacientes que requieren ventilación mecánica durante más de 24 h y que mejoran de la causa que motivó el soporte ventilatorio pueden ser extubados tras una primera prueba de respiración espontánea. El reto es cómo mejorar la desconexión de los pacientes que fracasan en esa prueba. Hasta el momento disponíamos de los métodos, que podemos denominar tradicionales, como son el tubo en T, la presión de soporte o la ventilación mandatoria intermitente sincronizada (SIMV). En los últimos años se han descrito nuevas aplicaciones de técnicas habituales como la ventilación no invasiva, nuevos métodos de ventilación como la compensación automática del tubo (ATC), la ventilación minuto mandatoria (MMV), la ventilación adaptativa de soporte (ASV) o estrategias automáticas de desconexión de la ventilación mecánica basadas en la presión de soporte. Queda por definir su posible papel en la desconexión de la ventilación mecánica en los enfermos con desconexión difícil o prolongada.
Most patients who require mechanical ventilation for longer than 24 hours, and who improve the condition leading to the indication of ventilatory support, can be weaned after passing a first spontaneous breathing test. The challenge is to improve the weaning of patients who fail that first test. We have methods that can be referred to as traditional, such as the T-tube, pressure support or synchronized intermittent mandatory ventilation (SIMV). In recent years, however, new applications of usual techniques as noninvasive ventilation, new ventilation methods such as automatic tube compensation (ATC), mandatory minute ventilation (MMV), adaptive support ventilation or automatic weaning systems based on pressure support have been described. Their possible role in weaning from mechanical ventilation among patients with difficult or prolonged weaning remains to be established.
Outcomes of patients ventilated with synchronized intermittent mandatory ventilation with pressure support: A comparative propensity score study
2010, Chest
Citation Excerpt :
However, in practice this difference did not translate into any significant differences in outcomes (duration of mechanical ventilation, weaning, stay in the ICU). The efficacy of IMV as a weaning technique was initially evaluated in three small studies18–20 with methodological limitations. In the mid-1990s two large randomized controlled trials8,9 compared the most popular methods of weaning and found that the use of SIMV prolonged the time of weaning vs pressure support8 or vs trials with T-piece.9
Few data are available regarding the benefits of one mode over another for ventilatory support. We set out to compare clinical outcomes of patients receiving synchronized intermittent mandatory ventilation with pressure support (SIMV-PS) compared with assist-control (A/C) ventilation as their primary mode of ventilatory support.
This was a secondary analysis of an observational study conducted in 349 ICUs from 23 countries. A propensity score stratified analysis was used to compare 350 patients ventilated with SIMV-PS with 1,228 patients ventilated with A/C ventilation. The primary outcome was in-hospital mortality.
In a logistic regression model, patients were more likely to receive SIMV-PS if they were from North America, had lower severity of illness, or were ventilated postoperatively or for trauma. SIMV-PS was less likely to be selected if patients were ventilated because of asthma or coma, or if they developed complications such as sepsis or cardiovascular failure during mechanical ventilation. In the stratified analysis according to propensity score, we did not find significant differences in the in-hospital mortality. After adjustment for propensity score, overall effect of SIMV-PS on in-hospital mortality was not significant (odds ratio, 1.04; 95% CI, 0.77–1.42; P = .78).
In our cohort of ventilated patients, ventilation with SIMV-PS compared with A/C did not offer any advantage in terms of clinical outcomes, despite treatment-allocation bias that would have favored SIMV-PS.
Airway management for prevention of ventilator-associated pneumonia
2005, Medicina Intensiva
La neumonía asociada a la ventilación mecánica (NVM) sigue siendo una importante causa de morbilidad y mortalidad en los pacientes críticos a pesar del uso de medidas preventivas.
Esta revisión se centra en las medidas relacionadas con la vía aérea para la prevención de la NVM y se basa en una exposición de la literature más relevante, en el European Task Force de 2001 y en las recomendaciones de los Centers for Disease Control and Prevention (CDC) de 2003.
Las medidas de probada eficacia son: el uso de la intubación orotraqueal mejor que la nasotraqueal; mantener una presión óptima en el balón de neumotaponamiento del tubo endotraqueal; retirar el tubo endotraqueal lo antes posible, evitando retrasos innecesarios; evitar la reintubación cuando sea posible; no cambiar rutinariamente las tubuladuras, sólo cuando estén visiblemente contaminadas o malfuncionantes; esterilizar o desinfectar entre diferentes pacientes los equipos y dispositivos respiratorios reutilizables; no esterilizar o desinfectar rutinariamente la maquinaria interna del respirador y de la máquina de anestesia; lavado de manos y guantes cuando se realice el contacto con las secreciones y equipos respiratorios.
Las medidas de eficacia no probada son: el uso de un tubo endotraqueal con una luz para la aspiración continua de secreciones subglóticas; el uso de la ventilación mecánica no-invasiva para reducir la necesidad y la duración de la intubación endotraqueal; el uso de un intercambiador de calor y humedad o un humidificador de agua caliente; el uso de un sistema cerrado multiusos o de un sistema abierto de un solo uso para la aspiración de secreciones respiratorias.
Ventilator-associated pneumonia continues to be an important cause of morbidity and mortality in critical patients despite the use of preventive measures. This review deals mainly with measures relating to the airway in prevention of ventilator-associated pneumonia. It is based on an exhibition of the most pertinent literature, on the European Task Force of 2001 and on CDC recommendations of 2003.
Most proven effective measures are: use of orotracheal intubation rather than nasotracheal; maintenance of an optimal pressure in the pilot balloon of the endotracheal tube; avoiding unnecessary delay as assurance that the tube is removed as quickly as possible; avoiding reintubation whenever possible; replacing manifolds not routinely, but only when they are visibly contaminated or malfunctioning; sterilizing or disinfecting re-usable equipment and respiratory devices between patients; not routinely sterilizing or disinfecting the internal workings of the respiratorand anesthesia machine; washing hands and gloves when making contact with secretions and respiratory equipment. Measures of no proven effectiveness are: use of lighted endotracheal tubes for continuous subglottal suctioning of secretions; use of non-invasive mechanical ventilation to reduce the need for and duration of endotracheal intubation; use of heat moisture exchangers or hot water humidifiers; use of closed multi-use systems, or open single-use systems for aspiration of respiratory secretions.
Utilization of mechanical ventilation in 72 Spanish intensive care units
2003, Medicina Intensiva
La ventilación mecánica es una técnica fundamental en las unidades de cuidados intensivos (UCI). El objetivo es conocer su utilización y las diferencias en su aplicación en 72 UCI españolas
Estudio de cohortes de los pacientes ventilados durante más de 12 h. Se registraron datos demográficos, indicación de la ventilación mecánica, parámetros ventilatorios, modos de ventilación y desconexión, y días de soporte ventilatorio, días de estancia y situación al alta
Se incluyó a 1.103 pacientes (29%) de los ingresados, un 66% de varones, con una mediana de edad de 65 años y del SAPS II de 43. No se observaron diferencias geográficas en la aplicación de la ventilación mecánica ni en los desenlaces principales. En el 64% la indicación de ventilación fue insuficiencia respiratoria. Al inicio, la modalidad asistida-controlada fue la más utilizada (90%), con un volumen tidal medio (desviación estándar [DE]) 8,9 (2,0) ml/kg y PEEP 5,5 (2,2) cmH2O. El 4% recibió ventilación no invasora, el 68% de los enfermos no precisó intubación. La duración de la ventilación fue 7 (8) días. El método de desconexión más utilizado fue una prueba única diaria de respiración espontánea (58%). La duración fue de 3 (5) días. La incidencia de traqueostomía fue 15% y se realizó a los 14 (8) días. La mortalidad en la UCI fue del 32,8% y en el hospital del 42,8%
La comparación de la utilización de la ventilación mecánica en 72 UCI españolas evidencia una práctica similar, con mínimas diferencias en el uso de los modos de ventilación y desconexión y una similar mortalidad y días de estancia
Utilization of mechanical ventilation in 72 spanish intensive care units. Mechanical ventilation is a fundamental technique in the intensive care unit (ICU). The objective of this study was to determine the utilization of this technique and whether there are differences in its application in 72 ICUs in Spain
A cohort study of patients who underwent mechanical ventilation for more than 12 hours was performed. We collected demographic data, indication for mechanical ventilation, ventilatory parameters, modes of ventilation and weaning, days of ventilatory support, hospital stay, and status at discharge
A total of 1,103 inpatients (29%) required mechanical ventilation. Sixty-six percent were men. The median age was 65 years. The median Simplified Acute Physiology Score (SAPS) II was 43. No geographical differences were observed regarding the implementation of mechanical ventilation or regarding the main outcomes. In 64% of patients the indication was acute respiratory failure. Initially, the assisted-controlled mode was the most frequently used (90%), with a tidal volume of 8.9 (2.0) ml/kg and a PEEP of 5.5 (2.2) cmH2O. Four percent of patients underwent non-invasive ventilation, and 68% did not require intubation. Duration of ventilation was 7 (8) days. The most commonly used weaning method was a once daily test of spontaneous breathing (58%). Duration of weaning was 3 (5) days. Tracheostomy was performed in 15% of patients and was carried out at 14 (8) days. Mortality in the ICU was 32.8% and inpatient mortality was 42.8%
Comparison of the utilization of mechanical ventilation in 72 Spanish ICUs showed similar practices. Differences in the use of modes of ventilation and weaning were minimal and mortality and length of stay were similar
Chronic obstructive pulmonary disease and weaning
2001, Reanimation
Trials comparing alternative weaning modes and discontinuation assessments
2001, Chest
Citation Excerpt :
The study by Esen et al30 showed trends in favor of PS over IMV in both the duration of ventilation and the success of extubation in 48 h (Table 9). Two non-RCTs3334 also examined alternative weaning modes for patients who were expected to be weaned very quickly from mechanical ventilation, with similar findings to those of the RCTs. Tomlinson et al33 found no difference in the duration of mechanical ventilation or the duration of weaning in medical-surgical ICU patients who were weaned from ventilatory support over a period of 2 h to (rarely) 3 days using IMV (without CPAP) vs multiple daily T-piece breathing trials.
We identified 16 randomized controlled trials (RCTs) of methods for weaning patients from mechanical ventilation, 8 of which were trials of discontinuation assessment strategies, 5 of which were trials of stepwise reduction in mechanical ventilatory support, and 3 of which were trials comparing alternative ventilation modes for weaning periods lasting < 48 h. We found that different thresholds for deciding when a patient is ready for a trial of spontaneous breathing, different criteria for a successful trial, and different thresholds for extubation may overwhelm the impact of alternative ventilation strategies. Nevertheless, the results of these studies suggest the possibility that multiple daily T-piece weaning or pressure support may be superior to synchronized intermittent mandatory ventilation. Other RCTs suggest that early extubation with the back-up institution of noninvasive positive-pressure ventilation as needed may be a useful strategy in selected patients.

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: Presented in part at the 51st Annual Scientific Assembly, American College of Chest Physicians, New Orleans, October 28-November 1, 1985.

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