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Recruitment Maneuvers Still Controversial in ALI/ARDS
Abstract & Commentary
Synopsis: In patients with ALI/ARDS from pulmonary and extrapulmonary causes, receiving mechanical ventilation with low tidal volumes and high PEEP, short-term effects of recruitment maneuvers as conducted in this study are variable.
Source: ARDS Clinical Trials Network. Crit Care Med. 2003;31: 2592-2597.
One of the most controversial issues in managing patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is whether (or how) special maneuvers to fully inflate the lung and open atelectatic areas (recruitment) should be used. The objectives of this study were to assess a) the magnitude of the immediate effects of recruitment on arterial oxygenation; b) the duration of the effects of recruitment maneuvers on requirements for FIO2 and positive end-expiratory pressure (PEEP); and c) the immediate effects of recruitment maneuvers on hemodynamics and barotrauma. The study was conducted in ALI or ARDS patients who were enrolled in a multicenter clinical trial designed to compare outcomes with 2 approaches to managing PEEP: a traditional PEEP strategy vs a strategy using higher PEEP levels. All patients received mechanical ventilation with small tidal volumes (6 mL/kg predicted body weight). This ancillary study of recruitment maneuvers was conducted only in patients randomized to the higher PEEP arm of the main trial.
This was a crossover study in which patients were randomized to receive single recruitment maneuvers on either the first and third or the second and fourth mornings after enrollment in the main ARDSnet trial. Recruitment maneuvers and sham recruitment maneuvers were not conducted if patients were in the process of being weaned from ventilatory support, if systolic blood pressure was < 100 mm Hg or > 200 mm Hg, or if heart rate was < 70/min or > 140/min. No additional sedatives or neuromuscular blocking agents were required. All patients were supported with volume-controlled ventilation.
Recruitment maneuvers were conducted by changing the ventilator mode to continuous positive airway pressure (CPAP) and gradually raising the CPAP level over 5-10 seconds to 35 cm H2O (40 cm H2O if measured weight exceeded 150% predicted body weight). This level of CPAP was maintained for 30 seconds unless systolic blood pressure decreased to < 90 mm Hg or by > 30 mm Hg, heart rate increased to > 140/min or by > 20/min, SpO2 was < 90% and had decreased by > 5%, or a cardiac dysrhythmia occurred. The CPAP level then was decreased over 5-10 seconds to the previous ventilator settings. Sham recruitment maneuvers were conducted by assigning an initial time in the morning and then recording respiratory, hemodynamic, and radiographic data while patients continued on mechanical ventilation without conducting a recruitment maneuver.
To assess immediate effects of recruitment maneuvers, the greatest increments in SpO2 during the first 10 minutes after initiating recruitment maneuvers or sham recruitment maneuvers were compared. After the first 10 minutes, FIO2 and PEEP were adjusted in discrete steps according to an explicit protocol (FIO2/PEEP-step) to maintain SpO2 of 88-95%. To assess duration of recruitment maneuver effects, changes in FIO2/PEEP-step were recorded at 30 minutes and 1, 2, 4, and 8 hours after recruitment maneuvers or sham recruitment maneuvers (a decrease in FIO2/PEEP-step is a favorable change).
There were 66 recruitment maneuvers and 70 sham recruitment maneuvers in 43 patients in whom at least 1 recruitment maneuver and 1 sham recruitment maneuver were conducted. Increments from baseline SpO2 were greater within 10 minutes after recruitment maneuvers than after sham recruitment maneuvers (1.7 ± 0.2% vs 0.6 ± 0.3%; P < 0.01). The responses to recruitment maneuvers were highly variable. In 10 instances, SpO2 increased by 5-9% during the first 10 min. However, in 14 instances, SpO2 decreased by 1-4% after initiating the recruitment maneuvers and did not return to baseline SpO2 levels within 10 minutes. None of the differences between the changes in adjusted FIO2/PEEP-step after recruitment maneuvers and sham recruitment maneuvers were significant. The mean decrease in adjusted FIO2/PEEP-step 2 hours after recruitment maneuvers was 0.19 ± 0.14 steps greater than the mean decrease in adjusted FIO2/PEEP-step 2 hours after sham recruitment maneuvers (P = 0.18). This is equivalent to a difference in PEEP of 0.36 cm H2O or a difference in FIO2 of 0.018.
Decreases in systolic blood pressure were significantly greater after recruitment maneuvers than after sham recruitment maneuvers. Decreases in SpO2 during the first 10 minutes were also significantly greater after recruitment maneuvers than after sham recruitment maneuvers. Recruitment maneuvers were terminated early in 3 instances because of hypotension or low SpO2. There were no apparent sequelae from these events, which were transient and self-limited. New barotrauma was evident on the first chest radiographs after 1 recruitment maneuver and after 1 sham recruitment maneuver.
Comment by Dean Hess, PhD, RRT
When Amato and colleagues1 published their paper on lung-protective ventilation for ALI/ARDS in 1998, it became clear that how the ventilator is set can affect patient-important outcomes like mortality. As part of their protective ventilation approach, Amato et al used pressure-controlled ventilation, limited the inspiratory pressure and tidal volume, used higher than conventional levels of PEEP, and applied recruitment maneuvers. Because so many interventions were applied simultaneously, it is not possible to know which of these was most important or if all are necessary to achieve the desired outcome. The use of recruitment maneuvers in the Amato study was initially overlooked by many. However, in his travels around the world promoting his approach, Amato championed the role of recruitment maneuvers. During a trip to Boston, my colleagues and I heard Amato describe his enthusiasm for recruitment maneuvers. Within hours after hearing this, we applied recruitment maneuvers to a patient with ARDS. The results were positive, and we quickly submitted a case report.2
After my initial enthusiasm for recruitment maneuvers, I have become less and less excited about their use. Despite the occasional dramatic responder (in terms of improved oxygenation), I have observed many times when the recruitment maneuver produced no effect on oxygenation and a few cases in which bad outcomes have resulted (eg, barotrauma or hemodynamic compromise). I guess it’s a matter of human nature that I was anxious to publish our first positive experience with the use of recruitment maneuvers but have not published subsequent bad outcomes associated with recruitment maneuvers.
The accumulating evidence is marginally supportive of recruitment maneuvers. Villagra and associates3 reported that recruitment maneuvers have no short-term benefit on oxygenation. Grasso and colleagues4 reported that recruitment maneuvers were only useful to improve oxygenation in patients with early ARDS and those without an impairment in chest wall mechanics. Moreover, the benefit was short-lived in that study. In patients with brain injury, Bein and associates5 reported that recruitment maneuvers marginally improved arterial oxygenation and adversely affected cerebral hemodynamics. Johannigman et al6 reported that recruitment maneuvers only transiently improved gas exchange during low tidal volume ventilation. To date, there have been no studies of the effect of recruitment maneuvers on patient-important outcomes.
In this multi-center, randomized, crossover study to assess effects of recruitment maneuvers in patients with ALI/ARDS receiving a lung protective mechanical ventilation strategy, systolic blood pressure and SpO2 decreased significantly after recruitment maneuvers. However, these effects were self-limited and without apparent long-term sequelae. SpO2 increased significantly more within 10 minutes after recruitment maneuvers than after sham recruitment maneuvers. The initial SpO2 responses were highly variable. There were small increases in mean SpO2 at 1 hour after recruitment maneuvers but not at other time points. Effects of recruitment maneuvers on requirements for FIO2/PEEP-step were not significant at any time point, and respiratory system compliance did not increase more after recruitment maneuvers than after sham recruitment maneuvers. These data are consistent with other studies suggesting that any physiologic benefit from recruitment maneuvers is short lived.
I’m certain that these data will be controversial. Proponents of recruitment maneuvers will argue that the study did not apply the recruitment maneuvers correctly or that a protocol allowing a PEEP decrease after the recruitment maneuver may have obviated any benefit from the recruitment maneuver. Nonetheless, the accumulating evidence from this and others studies suggests that recruitment maneuvers may not be all that we had hoped for. Unfortunately, the lungs of patients with ALI/ARDS do not appear to be as recruitable as the lungs of animals with experimentally induced lung injury. At this time, recruitment maneuvers cannot be considered a standard of care in patients with ALI/ARDS. We await further clinical study to establish the role for recruitment maneuvers.
1. Amato MB, et al. N
Engl J Med. 1998;338:347-354.
2. Medoff BD, et al. Crti Care Med. 2000;28:1210-1216.
3. Villagra A, et al. Am J Respir Crit Care Med. 2002;165:165-170.
4. Grasso S, et al. Anesthesiology. 2002;96:795-802.
5. Bein T, et al. Intensive Care Med. 2002;28:554-558.
6. Johannigman JA, et al. J Trauma. 2003;54:320-325.
Dean R. Hess, PhD, RRT, Respiratory Care, Massachusetts General Hospital, Department of Anesthesiology, Harvard Medical School, is Associate Editor of Critical Care Alert.