Mechanical VentilationAtelectasis and mechanical ventilation mode during conservative oxygen therapy: A before-and-after study
Introduction
Supplemental oxygen is a universal therapy in mechanically ventilated patients and can be lifesaving [1]. However, supplemental oxygen therapy may also cause adverse physiological effects and deleterious clinical outcomes [1], [2], [3], [4], [5], [6]. Such reports suggest that oxygen therapy can be a 2-edged sword and that attempts should be made to optimize its use and avoid both inadequate and excessive oxygen administrations. Despite these concerns, current oxygen therapy in mechanically ventilated patients remains biased toward liberal administration. Thus, much excess oxygen is delivered without evidence of benefit and sometimes outside of published guidelines [7], [8], [9], [10].
Recently, we reported the first pilot before-and-after trial of oxygen therapy in mechanically ventilated patients targeting a SpO2 of 90% to 92% (conservative oxygen therapy [COT]). We found that such therapy could be safely implemented in the intensive care unit (ICU) [11]. Concerns, however, were raised on the impact of COT on mechanical ventilation (MV) management and the development of pulmonary atelectasis [12] because no information was provided on such outcomes in the primary analysis of the study.
To respond to such concerns, we conducted a secondary analysis of our before-and-after trial and focused on the relationship between COT, MV management, and radiological evidence of atelectasis.
Section snippets
Methods
The study design was previously described [11] and is reported in the electronic supplement. It was approved by the institutional human research ethics committee with waiver for informed consent (approval no. H2011/04252) and registered at ClinicalTrial.gov (NCT01684124). In brief, we studied patients older than 18 years and expected to require MV for more than 48 hours. Exclusion criteria were imminent death or extracorporeal membrane oxygenation. During the standard oxygen therapy period,
Treatment effect
We studied 51 patients with 1043 data points on 271 MV days in the conventional therapy group and 54 patients with 1135 data points on 297 MV days in the COT group. The baseline characteristics of the 2 treatment groups for total study population were similar (Table 1).
During the conservative treatment period, patients had a significantly lower time-weighted average SpO2 (median, 95.5% [interquartile range, 94.0-97.3] vs 98.4% [97.3-99.1]) and Pao2 (83 mm Hg [71-94] vs 107 mm Hg [94-131]) with
Key findings
We conducted a study of the impact of COT on the severity of atelectasis and the management of MV in a before-and-after trial of conservative vs liberal oxygen therapy. We found that there was a significant subsequent difference in overall AS between groups. In addition, patients in the COT group had significantly lower “best” AS and greater improvement in AS in the first 7 days. Moreover, COT was associated with significantly earlier successful weaning from a mandatory ventilation mode and
Conclusions
In a before-and-after study, a more conservative SpO2 target might be associated with less radiological evidence of atelectasis formation in the first 7 days, earlier successful weaning from mandatory ventilation mode, and earlier attempts at spontaneous ventilation. These findings justify the design and conduct of further controlled studies of COT.
Author contributions
Conception and design: SS, GME, and RB; acquisition of data: SS, GME, NG, and AGS; analysis of chest x-rays: MDG, GDN, and PES; analysis and interpretation: SS, and RB; drafting the manuscript: SS, GME, and RB. All authors made contributed to critical revision of the manuscript for important intellectual content and approved the final version submitted.
Acknowledgments
This study was supported by the Austin Hospital Intensive Care Trust Fund.
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