Resp Care
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Patient-ventilator synchrony is a common problem with all patients actively triggering the mechanical ventilator. In many cases synchrony can be improved by vigilant adjustments by the managing clinician. ⋯ Proportional assist ventilation (PAV) and neurally adjusted ventilatory assist (NAVA) were both developed to improve patient-ventilator synchrony by proportionally unloading ventilatory effort and turning control of the ventilatory pattern over to the patient. This paper discusses PAV's and NAVA's theory of operation, general process of application, and the supporting literature.
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Airway pressure release ventilation (APRV) and bi-level positive airway pressure (BIPAP) are proposed to reduce patient work of breathing (WOB) sufficiently and to obviate issues related to patient-ventilator synchrony, so that spontaneous breathing can be maintained throughout the course of acute lung injury (ALI). Thus, APRV/BIPAP should reduce requirements for sedation and muscle paralysis, and thereby reduce the duration of mechanical ventilation. Only 17 human, animal, or lung-model studies have examined these claims, either directly or indirectly. ⋯ Furthermore, the theoretical benefits of APRV, in terms of controlling patient WOB, appear particularly limited when lung-protective ventilation is used for ALI patients with high minute ventilation demand. Future research should focus on issues of WOB and synchrony, so that reasonable ventilation protocols can be devised to test clinical outcomes against traditional modes. To date, low-level evidence suggests that promoting spontaneous breathing with APRV/BIPAP may not be appropriate in patients with relatively severe ALI/ARDS.
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Patient-ventilator interaction has been the focus of increasing attention from both manufacturers and researchers during the last 25 years. There is now compelling evidence that passive (controlled) mechanical ventilation leads to respiratory muscle dysfunction and atrophy, prolonging the need for ventilatory support and predisposing to a number of adverse patient outcomes. Although there is consensus that the respiratory muscles should retain some activity during acute respiratory failure, patient-ventilator asynchrony is now recognized as a cause of ineffective ventilation, impaired gas exchange, lung overdistention, increased work of breathing, and patient discomfort. ⋯ The respected authorities on mechanical ventilation who participated in this conference differed in the modes they preferred but agreed that proper understanding and use according to the individual patient's needs are more important than which mode is chosen. Conference participants discussed the determinants, manifestations, and epidemiology of patient-ventilator asynchrony, and described and compared several ventilation modes aimed specifically at preventing and ameliorating it. The papers arising from these discussions represent the most thorough examination of this important aspect of respiratory care yet published.