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

ABSTRACT 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.

  • Pediatric Critical Care Medicine 05/2014; 15(4):379-80. DOI:10.1097/PCC.0000000000000084 · 2.33 Impact Factor
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    ABSTRACT: Assisted mechanical ventilation (MV) may be a favorable alternative to controlled MV at the early phase of acute respiratory distress syndrome (ARDS), since it requires less sedation, no paralysis and is associated with less hemodynamic deterioration, better distal organ perfusion, and lung protection, thus reducing the risk of ventilator-associated lung injury (VALI). In the present review, we discuss VALI in relation to assisted MV strategies, such as volume assist-control ventilation, pressure assist-control ventilation, pressure support ventilation (PSV), airway pressure release ventilation (APRV), APRV with PSV, proportional assist ventilation (PAV), noisy ventilation, and neurally adjusted ventilatory assistance (NAVA). In summary, we suggest that assisted MV can be used in ARDS patients in the following situations: (1) Pao 2/Fio 2 >150 mm Hg and positive end-expiratory pressure ≥ 5 cm H2O and (2) with modalities of pressure-targeted and time-cycled breaths including more or less spontaneous or supported breaths (A-PCV [assisted pressure-controlled ventilation] or APRV). Furthermore, during assisted MV, the following parameters should be monitored: inspiratory drive, transpulmonary pressure, and tidal volume (6 mL/kg). Further studies are required to determine the impact of novel modalities of assisted ventilation such as PAV, noisy pressure support, and NAVA on VALI.
    Seminars in Respiratory and Critical Care Medicine 08/2014; 35(4):409-417. DOI:10.1055/s-0034-1382153 · 2.75 Impact Factor
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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.
    07/2014; DOI:10.1016/j.resinv.2014.03.002


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Jun 1, 2014