Noninvasive positive pressure ventilation in the management of patients with acute respiratory failure in the emergency department
(2003)
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- Because respiratory failure is the final common pathway for many types of critical illness, ventilatory management with mechanical ventilation often determines the likelihood of recovery or death. Instituted when the medical treatment fails, mechanical ventilation aims to correct the consequences of acute respiratory failure and respiratory acidosis. ln practice, an endotracheal tube is usually inserted into the upper airway to deliver positive pressure ventilation. This is an invasive procedure associated with complications, discomfort, morbidity and mortality. Over the past decade, several studies have shown that non invasive ventilation (positive-pressure ventilation through a nasal or face mask) is at least as effective as invasive ventilation in several conditions of acute respiratory insufficiency, with less complications and better outcomes. At the lime when we initiated this work, there were very few data on the use of the two-Ievel Noninvasive Positive Pressure Ventilation (NPPV) in emergency departments despite the fact that this therapeutic technique appeared as particularly weil suited for such a setting. The goal of this thesis was to define the real contribution of two-Ievel NPPV to the management of patients with acute respiratory failure in this setting. After a brief introduction, the history of the mechanical ventilation is reviewed. The aim of this first chapter is to explain the context of the genesis of this work ln the second chapter, we present choice and performance of ventilators used in this work. ln the third chapter of this thesis, we try to determine if NPPV Gan be applied in a busy emergency room and with which benefit for the patient. After a prospective, non-randomized, pilot study, we conclude that NPPV Gan be used in an emergency department for the initial management of patients in severe acute respiratory failure of various aetiologies with the usual dut Y staff and that NPPV seems to add a significant therapeutic value to previously administered pharmacological treatment without deleterious effects. We present also some specifie emergency indications of management in patients with acute respiratory failure. ln the fourth chapter, we try to determine the parameters that influence the Fi02 when NPPV is used with added oxygen in acute respiratory failure. After a iwo-part study ( clinical and experimental) we demonstrate that Fi02 depends on three major factors: the point where O2 is added into the circuit, the level of inspiratory pressure, and the oxygen flow rate. The respiratory rate and the tidal volume did not influence the delivered oxygen concentration. We demonstrated also that for IPAP levels beyond 12 cm H2O, Fi02 flows should be at least 4L/min. Moreover, an Fi02 superior or equal to 0.5 requires a very high level of oxygen flow. ln the fifth chapter, we try to answer the following question: does early NPPV have a real, rather than a placebo, value, both on objectively measured parameters and on patient's clinical condition? ln this context, we have performed a prospective, randomised placebo controlled study . This study is the first to compare, beyond standard medical therapy, NPPV with a similar placebo device. We conclude that early application of two-Ievel NPPV to patients with acute respiratory failure due to acute exacerbation of c_po or APO leads to a rapid improvement in clinical status and blood gases, that differs substantially from the evolution of similar patients treated with conventional medical therapy and a placebo NPPV device. ln the two final chapters, we discuss our results in the particular setting of emergency medicine and we present our point of view on what one should and should not do when NPPV is applied.
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Thys, F. (2003). Noninvasive positive pressure ventilation in the management of patients with acute respiratory failure in the emergency department. https://hdl.handle.net/2078.5/110823