Articles: intubation.
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Critical care medicine · Jul 1989
Comparative StudyAdditional work of breathing imposed by endotracheal tubes, breathing circuits, and intensive care ventilators.
A disadvantage of spontaneous breathing through an endotracheal tube (ETT) and connector attached to a breathing circuit and/or ventilator (breathing device) is an increase in the work of breathing. The work of breathing associated with ETT of 6 to 9-mm diameter and eight breathing devices was determined, using a lung simulator to mimic spontaneous inspiration at flow rates of 20 to 100 L/min and a tidal volume of 500 ml, at both zero end-expiratory pressure (ZEEP) and 10 cm H2O continuous positive airway pressure (CPAP). Work associated with the breathing devices alone (WCIR) ranged from -0.002 kg.m/L (Servo 900-C ventilator, 7-mm ETT, 20 L/min, ZEEP) to 0.1 kg.m/L (continuous flow circuit, 7-mm ETT, 100 L/min, CPAP), the latter representing 196% of the work of normal breathing. ⋯ This additional work imposed by the ETT varied considerably among devices. Spontaneous breathing through modern ventilators, circuits and ETT imposes a burden of increased work, most of which is associated with the presence of the ETT and connector. Whether this burden represents an impediment to the weaning patient, or has training value for the ultimate resumption of unassisted spontaneous ventilation, remains to be determined.
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Critical care medicine · Jul 1989
Case ReportsEndotracheal tube rupture, accidental extubation, and tracheal avulsion: three airway catastrophes associated with significant decrease in leak pressure.
We report three unusual, catastrophic cases in which a significant decrease in leak pressure around a tracheal tube was noted before the discovery of the ultimate airway problem. A brief review of potential causes of a decrease in leak pressure is included and management of these difficult cases is discussed.
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Am. Rev. Respir. Dis. · Jul 1989
Comparative StudyIn vitro versus in vivo comparison of endotracheal tube airflow resistance.
The mechanics of gas flow in endotracheal (ET) tubes have been evaluated extensively in vitro under static and dynamic conditions. Previous bedside determinations of respiratory system mechanics in patients with acute respiratory failure have been based on assumptions derived from in vitro measurements without direct measurement of in vivo ET tube resistance (RET). We hypothesized that the RET measured in vivo would be greater than those values obtained in vitro when peak flow rates and ET tube size were held constant. ⋯ Although there was considerable individual variation, values of RET measured in vivo were generally higher than those derived from in vitro measurements at both peak flow rates tested, perhaps because of secretions, head or neck position, tube deformation, or increased turbulence. We conclude that ET tubes contribute significantly to total airflow resistance and that RET is often significantly greater than indicated by in vitro studies. Estimates of work of breathing in critically ill patients must take into consideration the contribution of in vivo RET on total pulmonary system resistance.
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Comparative Study
The pressor response and laryngeal mask insertion. A comparison with tracheal intubation.
The pressor response associated with laryngoscopy and tracheal intubation may be harmful to certain patients. The laryngeal mask airway avoids the need for laryngoscopy and allows positive pressure ventilation of the lungs in appropriate patients. ⋯ We have shown a similar, but attenuated pattern of response associated with mask insertion in comparison with laryngoscopy and intubation; significant differences between the groups were evident in arterial diastolic blood pressure immediately after insertion and again 2 minutes later. Use of the laryngeal mask may therefore offer some limited advantages over tracheal intubation in the anaesthetic management of patients where the avoidance of the pressor response is of particular concern.
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The decision for timing of tracheostomy remains controversial. The relative complication rates in two retrospective series, in which 79 and 150 critically ill patients were examined, respectively, showed increased incidence of late complications with tracheostomy and led Petty's group to conclude "The value of tracheotomy when an artificial airway is required for periods as long as 3 weeks is not supported by data obtained in this study."