• Adriana M Güntzel Chiappa, Gaspar R Chiappa, Gerson Cipriano, Ruy S Moraes, Elton L Ferlin, Audrey Borghi-Silva, and Silvia R Vieira.
• Intensive Medicine Service, Hospital de Clinicas de Porto Alegre, Brazil.
• Clin Respir J. 2017 Jul 1; 11 (4): 489-495.

IntroductionSpontaneous breathing with a conventional T-piece (TT) connected to the tracheal tube orotraqueal has been frequently used in clinical setting to weaning of mechanical ventilation (MV), when compared with pressure support ventilation (PSV). However, the acute effects of spontaneous breathing with TT versus PSV on autonomic function assessed through heart rate variability (HRV) have not been fully elucidated.ObjectiveThe purpose of this study was to examine the acute effects of spontaneous breathing in TT vs PSV in critically ill patients.MethodTwenty-one patients who had received MV for ≥ 48 h and who met the study inclusion criteria for weaning were assessed. Eligible patients were randomized to TT and PSV. Cardiorespiratory responses (respiratory rate -ƒ, tidal volume-VT , mean blood pressure (MBP) and diastolic blood pressure (DBP), end tidal dioxide carbone (PET CO2 ), peripheral oxygen saturation (SpO2 ) and HRV indices in frequency domain (low-LF, high frequency (HF) and LF/HF ratio were evaluated.ResultsTT increased ƒ (20 ± 5 vs 25 ± 4 breaths/min, P<0.05), MBP (90 ± 14 vs 94 ± 18 mmHg, P<0.05), HR (90 ± 17 vs 96 ± 12 beats/min, P<0.05), PET CO2 (33 ± 8 vs 48 ± 10 mmHg, P<0.05) and reduced SpO2 (98 ± 1.6 vs 96 ± 1.6%, P<0.05). In addition, LF increased (47 ± 18 vs 38 ± 12 nu, P<0.05) and HF reduced (29 ± 13 vs 32 ± 16 nu, P<0.05), resulting in higher LF/HF ratio (1.62 ± 2 vs 1.18 ± 1, P<0.05) during TT. Conversely, VT increased with PSV (0.58 ± 0.16 vs 0.50 ± 0.15 L, P<0.05) compared with TT.ConclusionAcute effects of TT mode may be closely linked to cardiorespiratory mismatches and cardiac autonomic imbalance in critically ill patients.© 2015 John Wiley & Sons Ltd.

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