Conservative Oxygen Therapy during Mechanical Ventilation in the ICU

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Abstract

Patients who are undergoing mechanical ventilation in the intensive care unit (ICU) often receive a high fraction of inspired oxygen (Fio2) and have a high arterial oxygen tension. The conservative use of oxygen may reduce oxygen exposure, diminish lung and systemic oxidative injury, and thereby increase the number of ventilator-free days (days alive and free from mechanical ventilation).

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Most cited references 11

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Association between arterial hyperoxia following resuscitation from cardiac arrest and in-hospital mortality.

J Hope Kilgannon, Alan Jones, Nathan I. Shapiro … (2010)

Laboratory investigations suggest that exposure to hyperoxia after resuscitation from cardiac arrest may worsen anoxic brain injury; however, clinical data are lacking. To test the hypothesis that postresuscitation hyperoxia is associated with increased mortality. Multicenter cohort study using the Project IMPACT critical care database of intensive care units (ICUs) at 120 US hospitals between 2001 and 2005. Patient inclusion criteria were age older than 17 years, nontraumatic cardiac arrest, cardiopulmonary resuscitation within 24 hours prior to ICU arrival, and arterial blood gas analysis performed within 24 hours following ICU arrival. Patients were divided into 3 groups defined a priori based on PaO(2) on the first arterial blood gas values obtained in the ICU. Hyperoxia was defined as PaO(2) of 300 mm Hg or greater; hypoxia, PaO(2) of less than 60 mm Hg (or ratio of PaO(2) to fraction of inspired oxygen <300); and normoxia, not classified as hyperoxia or hypoxia. In-hospital mortality. Of 6326 patients, 1156 had hyperoxia (18%), 3999 had hypoxia (63%), and 1171 had normoxia (19%). The hyperoxia group had significantly higher in-hospital mortality (732/1156 [63%; 95% confidence interval {CI}, 60%-66%]) compared with the normoxia group (532/1171 [45%; 95% CI, 43%-48%]; proportion difference, 18% [95% CI, 14%-22%]) and the hypoxia group (2297/3999 [57%; 95% CI, 56%-59%]; proportion difference, 6% [95% CI, 3%-9%]). In a model controlling for potential confounders (eg, age, preadmission functional status, comorbid conditions, vital signs, and other physiological indices), hyperoxia exposure had an odds ratio for death of 1.8 (95% CI, 1.5-2.2). Among patients admitted to the ICU following resuscitation from cardiac arrest, arterial hyperoxia was independently associated with increased in-hospital mortality compared with either hypoxia or normoxia.

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Statistical evaluation of ventilator-free days as an efficacy measure in clinical trials of treatments for acute respiratory distress syndrome.

David A Schoenfeld, Gordon R Bernard (2002)

Trials of potential new therapies in acute lung injury are difficult and expensive to conduct. This article is designed to determine the utility, behavior, and statistical properties of a new primary end point for such trials, ventilator-free days, defined as days alive and free from mechanical ventilation. Describing the nuances of this outcome measure is particularly important because using it, while ignoring mortality, could result in misleading conclusions. To develop a model for the duration of ventilation and mortality and fit the model by using data from a recently completed clinical trial. To determine the appropriate test statistic for the new measure and derive a formula for power. To determine a formula for the probability that the test statistic will reject the null hypothesis and mortality will simultaneously show improvement. To plot power curves for the test statistic and determine sample sizes for reasonable alternative hypotheses. Intensive care units. Patients with acute respiratory distress syndrome or acute lung injury as defined by the American-European Consensus Conference. The proposed model fit the clinical data. Ventilator-free days were improved by lower tidal volume ventilation, but the improvement was mostly caused by the improved mortality rate, so trials that expected similar effects would only have modest increase in power if they used ventilator-free days as their primary end point rather than 28-day mortality. Similar results were obtained using the model in two groups segregated by low or high Acute Physiology and Chronic Health Evaluation score. On the other hand, if patients are divided into two groups on the basis of the lung injury score, both the duration of ventilation and mortality are lower in the low lung injury score group. A trial of a treatment that had a similar clinical effect would have a large increase in power, allowing for a reduction in the required sample size. Use of ventilator-free days as a trial end point allows smaller sample sizes if it is assumed that the treatment being tested simultaneously reduces the duration of ventilation and improves mortality. It is unlikely that a treatment that led to higher mortality could lead to a statistically significant improvement in ventilator-free days. This would be especially true if the treatment were also required to produce a nominal improvement in mortality.

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A Binational Multicenter Pilot Feasibility Randomized Controlled Trial of Early Goal-Directed Mobilization in the ICU.

Carol L Hodgson, Michael Bailey, Rinaldo Bellomo … (2016)

To determine if the early goal-directed mobilization intervention could be delivered to patients receiving mechanical ventilation with increased maximal levels of activity compared with standard care.