Anaesthesia and intensive care
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Anaesth Intensive Care · May 2011
Intrabronchial airway pressures in intubated patients during bronchoscopy under volume controlled and pressure controlled ventilation.
Bronchoscope insertion through an endotracheal tube increases airflow resistance. Constant tidal volume (T(v)) ventilation can be maintained by augmenting the inspiratory pressure, but increased outflow resistance cannot be compensated for. Air trapping distal to the tube may lead to higher airway pressures in volume controlled (VC) mode and reduced T(v) in pressure controlled (PC) mode. ⋯ In PC mode, peak airway pressure was unchanged and end-expiratory airway pressure increased from 9.5 cmH2O (7 to 10) to 10.5 cmH2O (9 to 18) (P = 0.017). Median T(v) was reduced from 673 ml (585 to 800) to 450 ml (408 to 560) (P = 0.012); median P(a)CO2 increased from 5.7 kPa to 6.5 kPa (P = 0.012). Using distal measurement, positive end-expiratory airway pressure increased markedly in VC mode but only marginally in PC mode after bronchoscope insertion.
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Anaesth Intensive Care · May 2011
Rohrer's constant, K2, as a factor of determining inspiratory resistance of common adult endotracheal tubes.
The aim of the study was to calculate the in vitro inspiratory resistance (R(ETT)) of adult endotracheal tubes (ETT), via the end-inspiratory occlusion method, and to apply this method in vivo in order to estimate R(ETT) value in real time. By plotting R(ETT) over inspiratory flow (V) and calculating Rohrer's coefficients of linear and nonlinear resistance, K1 and K2 respectively, we determined the resistive behaviour of each ETT. Peak and plateau pressures were recorded at both proximal and distal sites of the ETT after applying a three-second occlusion under constant flow. ⋯ The intraluminal catheter increased R(ETT) No.7.0 by an average of 49%. Finally, ten patients with partially obstructed ETTs were tested and K2 in vivo constants found to be higher than their corresponding in vitro values (P value 0.00012). Therefore, knowing the performing size of an ETT may help the clinicians identify ETT obstruction and deal with weaning problems.
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Anaesth Intensive Care · May 2011
Editorial CommentDaily sedation interruption; a glass half empty?