PT - JOURNAL ARTICLE AU - Ilaria Valentini AU - Eva Tonveronachi AU - Cesare Gregoretti AU - Chiara Mega AU - Luca Fasano AU - Lara Pisani AU - Stefano Nava TI - Different Tracheotomy Tube Diameters Influence Diaphragmatic Effort and Indices of Weanability in Difficult to Wean Patients AID - 10.4187/respcare.01747 DP - 2012 Dec 01 TA - Respiratory Care PG - 2012--2018 VI - 57 IP - 12 4099 - http://rc.rcjournal.com/content/57/12/2012.short 4100 - http://rc.rcjournal.com/content/57/12/2012.full AB - OBJECTIVE: To determine the effects of different tracheotomy tube sizes on diaphragm effort and weanability indices. METHODS: Ten tracheotomized and difficult to wean subjects were randomized to 2 T-piece trials, with different tracheotomy tube diameters: inner diameters 8 mm and 6.5 mm. Diaphragm pressure-time product per min. (PTPdi/min), lung compliance and resistance (CL and RL), breathing pattern, tension-time index of the diaphragm (TTdi), and the ratio of breathing frequency to tidal volume (f/VT) were recorded. In an in vitro model, the flow-pressure relationship was measured using the 2 tracheotomy tubes and 2 endotracheal tubes of the same diameter. RESULTS: The use of a smaller diameter resulted in an increase of PTPdi (337.63 ± 194.35 cm H2O · s/min vs 263.28 ± 156.23 cm H2O · s/min for 6.5 mm and 8 mm, respectively, P = .004) and RL (16.74 ± 8.10 cm H2O · s/min vs 11.72 ± 7.88 cm H2O · s/min, respectively, P = .008). Both weanability indices were also significantly higher using the smaller tube: f/VT 93.32 ± 20.91 vs 77.06 ± 19.26 for 6.5 mm and 8 mm, respectively, P < .02; TTdi 0.09 ± 0.052 vs 0.08 ± 0.04, respectively, P < .02. In vitro measurements confirmed that the resistances were higher with the smaller diameter and similar between the tracheotomy tubes and the endotracheal tubes of the same diameters. CONCLUSIONS: In tracheotomized difficult to wean subjects the decrease of the tracheotomy tube size was associated with an increased PTPdi, f/VT, and TTdi, that were otherwise normal, using a higher diameter. The in vitro study showed that the resistances increased similarly for tracheotomy tube and endotracheal tube, decreasing the diameter and increasing the flows.