Airway Pressure Release Ventilation: What Do We Know?

Respiratory Institute, The Cleveland Clinic, Cleveland, OH, USA.
Respiratory care (Impact Factor: 1.84). 07/2011; 57(2):282-92. DOI: 10.4187/respcare.01238
Source: PubMed


Airway pressure release ventilation (APRV) is inverse ratio, pressure controlled, intermittent mandatory ventilation with unrestricted spontaneous breathing. It is based on the principle of open lung approach. It has many purported advantages over conventional ventilation, including alveolar recruitment, improved oxygenation, preservation of spontaneous breathing, improved hemodynamics, and potential lung-protective effects. It has many claimed disadvantages related to risks of volutrauma, increased work of breathing, and increased energy expenditure related to spontaneous breathing. APRV is used mainly as a rescue therapy for the difficult to oxygenate patients with acute respiratory distress syndrome (ARDS). There is confusion regarding this mode of ventilation, due to the different terminology used in the literature. APRV settings include the "P high," "T high," "P low," and "T low". Physicians and respiratory therapists should be aware of the different ways and the rationales for setting these variables on the ventilators. Also, they should be familiar with the differences between APRV, biphasic positive airway pressure (BIPAP), and other conventional and nonconventional modes of ventilation. There is no solid proof that APRV improves mortality; however, there are ongoing studies that may reveal further information about this mode of ventilation. This paper reviews the different methods proposed for APRV settings, and summarizes the different studies comparing APRV and BIPAP, and the potential benefits and pitfalls for APRV.

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Available from: Robert L Chatburn
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    • "2.1. APRV settings (Fig. 1A) We used 10 releases per min (6 s in each cycle), a P high of 25 cmH 2 O, a P low of 0 cmH 2 O, a T low of 0.3 s, which corresponds to 1 time constant (1τ) to obtain an estimated auto-PEEP of 9.25 cmH 2 O (36.8% of 25 cmH 2 O) [5] [10], and a T high of 5.7 s, resulting in a mandatory breath I:E ratio of 19:1. "
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    ABSTRACT: Background No objective data directly comparing the 2 modes are available. Based on a simple mathematical model, APRV and BIPAP can presumably be set to achieve the same mean airway pressure (mPaw), end expiratory pressure, and tidal volume (VT). Herein, we tested this hypothesis when using a real ventilator and clinically relevant settings based on expiratory time constants. Methods A spontaneously breathing acute respiratory distress syndrome patient was modeled with a lung simulator. Mode settings: P high and the number of releases were the same in both modes; T low=1 time constant in APRV (expected auto-positive end-expiratory pressure [PEEP], ≈9 cmH2O) and 5 time constants in BIPAP; P low, 0 cmH2O in APRV and 9 cmH2O in BIPAP (equal to the expected auto-PEEP in APRV). The mean mandatory release volumes, minute ventilation [V̇E], mPaw, and total PEEP were compared with t-tests using a P value of 0.05 to reject the null hypothesis. Results APRV yielded significantly higher mPaw than did BIPAP. Minute ventilation was significantly higher in BIPAP. The total PEEP was significantly higher in APRV; the total PEEP was significantly higher than expected. Conclusion We found that neither mode was superior to the other, and that a real ventilator does not behave like a mathematical model. Extreme prolongation of T high generated a higher mPaw at the expense of V̇E, and vice versa. The lower VT with APRV was due to the higher total PEEP, which was higher than expected. Setting the T low according to the respiratory system time constant for either mode resulted in an unpredictable total PEEP.
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    ABSTRACT: Airway pressure release ventilation (APRV) is a mode of ventilation that has been around since the 1980s and was originally viewed as a type of continuous positive pressure mode of ventilation. Conceptually, APRV can be thought of as a type of inverse-ratio, pressure-controlled, intermittent mandatory ventilation during which the maintenance of spontaneous breathing and prolonged application of high mean airway pressure contribute to the clinical benefits. The aim of this review article was to familiarize the bedside clinician working in the intensive care unit with the theory and rationale behind this mode of ventilation. The potential advantages and disadvantages of APRV will also be discussed to empower the advance practice clinician and bedside nurse to advocate for their patient diagnosed with the often-high mortality disease of acute respiratory distress syndrome.
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    ABSTRACT: As technology continues to develop, a wide range of novel and nontraditional modes of mechanical ventilation have become available for the management of critically ill patients. Proportional assist ventilation, neurally adjusted ventilatory assist and adaptive support ventilation are three novel modes of ventilation, which attempt to optimize patient-ventilator synchrony. Improved interactions between patient and ventilator may be important in improving clinical outcomes. Another important priority for mechanically ventilated patients is lung protection, and nontraditional modes of ventilation that may be implemented to minimize ventilator-associated lung injury include airway pressure release ventilation and high-frequency ventilation. Novel and nontraditional modes of ventilation may represent important tools in the critical care environment; however, continued investigation is needed to determine the overall impact of these various approaches on outcomes for mechanically ventilated patients.
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