The resistance of the breathing circuit with the consequence of increased
The resistance of the breathing circuit with the consequence of increased WOB during PSV. Methods Four different types of CT+S (R ch, Medisil, Medisize, Mallinckrodt) were ventilated using a sinusoidal flow pattern, and the flow-dependent pressure drop across the CT+S was recorded. Flow dependency of the pressure drop was determined by fitting Rohrer’s equation (P = K1*V + K2*V2). The resulting coefficients K1 and K2 were used in a mathematical simulation of PSV ventilation to calculate the influence of CT+S on breathing pattern, minute ventilation (VE) and WOB in simulated normal, obstructive and restrictive patients. Results The resistance of the different models of CT+S widely varied. The CT+S type used in our ICU had a resistance of 3.mbar/l/s (at 1 l/s), comparable with a #9 ETT. Dependent on the patient’s disease and muscle strength (Pmus) and on the ventilatory demand, the use of CT+S reduced minute ventilation by up to 13 (Fig. 1). If the additional WOB is accomplished by the patient, he/she has to increase the Pmus by up to 45 (Fig. 2). If the pressure support is increased instead, an additional pressure of up to 37 has to be applied (Fig. 3). In some simulated patients with pulmonary obstructive disease, this additional pressure support caused missed efforts and additional dynamic hyperinflation. Interestingly, in simulated pulmonary restriction, a paradox effect of the additional resistance on tidal volume during PSV was observed: the reduction of peak inspiratory flow led to a delayed cycling of inspiration. As the cycling criterion during PSV (flow drop to 25 of peak inspiratory flow) results in a very short inspiratory time in these patients, a delayed cycling led to an increased inspiratory time and hence to an increased tidal volume. Conclusions The resistance PubMed ID: of CT+S adds significant load to the respiratory system. CT+S consisting of low resistive parts should therefore be preferred. In restrictive patients, PSV without TSA biological activity variable cycling may be an inappropriate mode.P37 The intensive care requirements and need for early ventilatory support in patients undergoing emergency and elective spinal surgeryJ Butler, C McMahon, B Marsh, A Poynton Mater PubMed ID: Misericordiae University Hospital, Dublin, Ireland Critical Care 2006, 10(Suppl 1):P37 (doi:10.1186/cc4384) Background Patients undergoing emergency or elective spinal surgery often require mechanical ventilation for prolonged periods because of their inability to protect their airways, persistence of excessive secretions, and inadequacy of spontaneous ventilation. Tracheostomy plays an integral role in the airway management of such patients; however, its timing still remains subject to considerable practice variation Study design A retrospective review of all spinal surgery admissions to the ICU and high dependency unit (HDU) from the National Spinal Injuries Unit (NSIU) at the Mater Misericordiae University Hospital over a 4-year period (n = 152). Objective To assess the intensive care requirements of a tertiary referral centre specializing in acute spinal cord injury and diseases of the spine, and to identify risk factors associated with respiratory compromise in the spinal surgery patient. Methods A retrospective review of all spinal surgery admissions from the NSIU to the ICU and HDU at the Mater Misericordiae University Hospital between 1 January 2002 and 30 SeptemberFigure 1 (abstract P36)Figure 2 (abstract P36)Figure 3 (abstract P36)SAvailable online

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