SIGH IN ACUTE RESPIRATORY DISTRESS SYNDROME: EFFECTS IN SUPINE AND IN PRONE POSITION

INTRODUCTION. It has been established that sighs (1) may be useful to improve respiratory function, compared to the “lung protective strategies” –VT <8 mL/kg, plateau pressure (Pplat) <35 cmH2O, PEEP > lower Pflex of the VP curve–. Aim of this study was to assess the effects of sighs in supine (SU) and prone (PR) position. METHODS. We studied 10 consecutive (mean age 63 ±9.7 yrs, 7 male) sedated and paralyzed ARDS patients (PaO2/FiO2 122 ±44). The entire study lasted 6 hours, divided in 6 periods –1h for each period–: SU basal, SU sigh, SU return, PR basal, PR sigh, PR return. The ventilatory setting was kept constant during the entire protocol: 32 ±4.1 cmH2O of Pplat, 590 ±137 ml of VT, 8.5 ±1.7 L of minute ventilation (VE), a respiratory rate of 15 ±2.4 br/min and a PEEP level of 14 ±3 cmH2O. Sigh was provided by 3 br/min to reach a 45 ±2.4 cmH2O of Pplat, keeping VE and mean airway pressure constant. We measured gas-exchange, end-expiratory lung volume (EELV, helium dilution), hemodynamics and respiratory mechanics (end-inspiratory occlusion). The comparison between different ventilatory periods was performed by paired t-test; statistical significance was accepted as p < 0.05. RESULTS. Results are shown in the table, expressed as mean ± standard deviation. Both in supine and in prone position, the change in PaO2 during sigh periods was associated with the change in EELV: ΔPaO2 = 9.3 mmHg + 0.1 x ΔEELV (r = 0.71, p < 0.05), ΔPaO2 = 19.5 mmHg + 0.06 x ΔEELV (r = 0.74, p < 0.05), respectively. CONCLUSION. 1) Sigh ventilation resulted to be more effective in prone than in supine position. 2) Lung volumes and gas-exchange improvements induced by sigh were more retained during post-sigh period in prone than in supine position. REFERENCES. 1. Pelosi P, et al. Am J Respir Crit Care Med 1999;159:872-880.