How Mechanical Ventilation Measurement, Cutoff and Duration Affect Rapid Shallow Breathing Index Accuracy: A Randomized Trial.

BACKGROUND: Decreased accuracy of the rapid shallow breathing index (RSBI) can stem from 1) the method used to obtain this index, 2) duration of mechanical ventilation (MV), and 3) the established cutoff point. The objective was to evaluate the values of RSBI determined by three different methods, using distinct MV times and cutoff points. METHODS: This prospective study included 40 subjects. Before extubation, three different methods were employed to measure RSBI: pressure support ventilator (PSV) (PSV = 5 - 8 cm H2O; positive end-expiratory pressure (PEEP) = 5 cm H2O) (RSBI_MIN), automatic tube compensation (ATC) (PSV = 0, PEEP = 5 cm H2O, and 100% tube compensation) (RSBI_ATC), and disconnected MV (RSBI_SP). The results were analyzed according to the MV period (less than or over 72 h) and to the outcome of extubation (< 72 h, successful and failed; > 72 h successful and failed). The accuracy of each method was determined at different cutoff points (105, 78, and 50 cycles/min/L). RESULTS: The RSBI_MIN, RSBI_ATC, and RSBI_SP values in the group < 72 h were 38 ± 18, 45 ± 26 and 55 ± 22; in the group > 72 h, RSBI_SP value was higher than those of RSBI_ATC and RSBI_MIN (78 ± 29, 51 ± 19 and 39 ± 14) (P < 0.001). For patients with MV > 72 h who failed in removing MV, the RSBI_SP was higher (93 ± 28, 58 ± 18 and 41 ± 10) (P < 0.000), with greater accuracy at cutoff of 78. CONCLUSION: RSBI_SP associated with cutoff point < 78 cycles/min/L seems to be the best strategy to identify failed extubation in subjects with MV for over 72 h.

Comparison of Energy Expenditure and Oxygen Consumption of Spontaneous Breathing Trial Conducted With and Without Automatic Tube Compensation.

BACKGROUND: Weaning from mechanical ventilation is defined as the process of release of ventilatory support and how the evaluation of this phase is conducted in the spontaneous breathing trial (SBT). One of the most used modes of SBT is the continuous positive airway pressure (CPAP), which applies a continuous positive pressure in both inspiration and expiration. However, together with the mechanical ventilation modes, the automatic tube compensation (ATC) can be used, which compensates the resistance imposed by the endotracheal tube. The objective of this study was to compare oxygen consumption (VO2) and energy expenditure (EE) during SBT conducted with and without ATC. METHODS: The study was prospective, randomized and crossover. Forty mechanically ventilated patients were admitted to an intensive care unit of a university tertiary hospital. The participants were randomly allocated in group 1, in which SBT was initiated with CPAP and ATC, followed by CPAP without ATC or in group 2, in which SBT was initiated with CPAP without ATC, followed by CPAP with ATC. Indirect calorimetry helped to measure VO2 and EE during SBT. RESULTS: The differences between VO2 and EE obtained during SBT with ATC and without ATC were -1.6 mL/kg/min (95% CI: -4.36 - 1.07) and 5.4 kcal/day (95% CI: -21.67 - 10.79), respectively. CONCLUSIONS: We concluded that VO2 and EE obtained during SBT with and without ATC were not different.

Efeitos da administração sistêmica de corticosteróides sobre propriedades mecânicas do diafragma de coelhos / Effects of corticosteroid systemic administration on mechanical properties of rabbits diaphragm muscle

Corticosteróides sistêmicos em altas doses podem causar miopatia metabólica. O objetivo deste estudo foi avaliar, por meio de ensaios de tração, os efeitos da miopatia induzida por corticosteróides nas propriedades mecânicas do músculo diafragma de coelhos...

High doses of systemic corticosteroids might promote metabolic myopathy. The aim of this study was to assess, by means of traction assays, the effects of myopathy induced by systemic corticosteroids on mechanical features of the diaphragm muscle of rabbits...