The effects of recruitment maneuver on oxygenation in primary and secondary adult respiratory distress syndrome

Introduction

Recruitment maneuvers (RM), as an adjunt to mechanical ventilation, have been shown to be capable of reopening collapsed alveolar units in ARDS, providing better ventilatory parameters and improvement in oxygenation. The aim of our study is to investigate and to compare the response of patients with pulmonary and extrapulmonary ARDS to recruitment maneuver.

Methods

We studied 18 patients with severe ARDS of varying etiology admitted to the intensive care unit of Istanbul University, Istanbul Medical Faculty. The diagnosis of ARDS was based on the criteria proposed by the American–European Consensus Conference on ARDS. The patients who demonstrated impaired oxygenation, during pressure regulated volume-controlled ventilation with 10 ml/kg tidal volume and 12/min frequency comprised our study population. The patients were presented to four members of the ICU team individually and assigned to primary (ARDS_P) and secondary (ARDS_S) ARDS groups according to the patient's history and clinical presentation, along with the results of microbiological tests. During the recruitment maneuver, we applied sustained inflation (SI), which consisted of 40 cmH₂O CPAP. After 30 s we returned to the previous tidal volume with 20 cmH₂O PEEP levels. Keeping peak airway pressure below 45 cmH₂O, we adjusted the optimal PEEP level, between 10–20 cmH₂O, by matching the saturation on pulse oximeter with the lowest PEEP. Following the setting of PEEP level, we recorded arterial blood gas values, ventilatory parameters and hemodynamic measurements at 15 min, 1st, 4th and 6th hours of post-RM period.

Results

The clinical defining scores of patients are summarized in Table 1. Over 6-hour period of time following RM, there was no statistically significant change in both hemodynamic and ventilatory measurements, except PaO₂/FiO₂ ratios (Table 2). Mean values of PEEP before and after RM were 10 ± 3.4 cmH₂O and 14.6 ± 2.8 cmH₂O in ARDS_P (P = 0.04), 12 ± 5 and 17 ± 2.8 in ARDS_S (P = 0.01). The mean values of PaO₂/FiO₂ ratio difference between the baseline and the value at the end of the study were 41 ± 30 % in ARDS_P, and 89 ± 111% in ARDS_S (P = 0.6). PaO₂/FiO₂ ratios started to increase significantly mainly 15 min following RM in ARDS_S, and 4 hours after RM in ARDS_P.

Table 1

Table 2

Conclusion

The response of patients with secondary ARDS to RM was observed earlier than the response of patients with primary ARDS.