Airway pressure release ventilation

Airway pressure release ventilation (APRV) — is a relatively new strategy of ventilation that became commercially available in the United States in the mid-1990s. APRV differs fundamentally from that of conventional positive-pressure ventilation. Whereas conventional modes of mechanical ventilation begin the breathing cycle at a baseline pressure and elevate airway pressure (P_IP) to accomplish tidal ventilation (V_T), APRV begins at a pressure higher than the baseline pressure and follows with a deflation to accomplish tidal ventilation^[1]. Fundamentally APRV is a time-cycled alternant between two levels of positive airway pressure, with the main time on the high level and a brief expiratory release to facilitate ventilation.^[2]

This is a type of inverse ratio ventilation. The exhalation time (T_low) is shortened to usually less than one second to maintain alveoli inflation. Fundamentally this is a continuous pressure with a brief release. APRV currently the most efficient conventional mode for lung protective ventilation.^[3]

Settings and measurements

Settings are sometimes brand specific and the term for the individual settings may differ, however generally the settings listed here are a fundamental explanation of the purpose of the settings within the APRV mode.

• P_high — This is the inspiratory pressure (just like in pressure control).
• T_high — This value is the number of seconds during the inhalation phase.
• T_peep — Also known as the T_low, this is the time allotted for expiration.
• FiO₂ — The fractional O2 percentage that is being added to the delivered air.

Perceptions and Receptions

Different perceptions of this mode may exist around the globe. While 'APRV' is common to users in North America, a very similar mode, biphasic positive airway pressure (BIPAP), was introduced in Europe.^[4] The term APRV has also been used in American journals where, from the ventilation characteristics, BIPAP would have been the appropriate terminology^[5]. To further confusion, BiPAP© is a registered trade-mark for a noninvasive ventilation mode in a specific ventilator (Respironics Inc.). Other names (BILEVEL, DUOPAP, BIVENT) have been created for legal reasons. Although similar in modality, these terms describe how a mode is intended to inflate the lung, rather than defining the characteristics of synchronization or the way spontaneous breathing efforts are supported.

Other terms

APRV is used by many brands and models of mechanical ventilators under different names. Most names are copyrighted as trademarks and do not represent nomenclature of mechanical ventilation but may be referred to clinically by the brand name.

Some of these names include:

• BiVent - (Servo-i ventilator by Maquet)
• BiLevel
• DuoPAP

Further reading

1. Kaplan LJ. Bailey H. Formosa V. “Airway pressure release ventilation increases cardiac performance in patients with acute lung injury/adult respiratory distress syndrome” Critical Care (London). 5(4):221-6, 2001 Aug.
2. Wrigge H. Zinserling J. Hering R. Schwalfenberg N. Stuber F. von Spiegel T. Schroeder S. Hedenstierna G. Putensen C. “Cardiorespiratory effects of automatic tube compensation during airway pressure release ventilation in patients with acute lung injury.” Anesthesiology. 95(2):382-9, 2001 Aug
3. Räsänen J, Cane RD, Downs JB, Hurst JM, Jousela IT, Kirby RR, Rogove HJ “Airway pressure release ventilation during acute lung injury: A prospective multicenter trial” Crit Care Med 1991; 19: 1234–41
4. Putensen C. Mutz NJ. Putensen-Himmer G. Zinserling J. “Spontaneous breathing during ventilatory support improves ventilation-perfusion distributions in patients with acute respiratory distress syndrome.” American Journal of Respiratory & Critical Care Medicine. 159(4 Pt 1):1241-8, 1999 Apr.
5. Sydow M. Burchardi H. Ephraim E. Zielmann S. Crozier TA. “Long-term effects of two different ventilatory modes on oxygenation in acute lung injury. Comparison of airway pressure release ventilation and volume-controlled inverse ratio ventilation.” American Journal of Respiratory & Critical Care Medicine. 149(6):1550-6, 1994 Ju

References

1. ^ Frawley PM, Habashi NM (2001) Airway pressure release ventilation: theory and practice. AACN Clin Issues 12:234-246
2. ^ Dietrich Henzler (2011). "What on earth is APRV?". Critical care (London, England) 15 (1): 115. doi:10.1186/cc9419. PMID 21345265. 
3. ^ Adrian A. Maung & Lewis J. Kaplan (July 2011). "Airway pressure release ventilation in acute respiratory distress syndrome". Critical care clinics 27 (3): 501–509. doi:10.1016/j.ccc.2011.05.003. PMID 21742214. 
4. ^ M. Baum, H. Benzer, C. Putensen, W. Koller & G. Putz (September 1989). "[Biphasic positive airway pressure (BIPAP)--a new form of augmented ventilation]". Der Anaesthesist 38 (9): 452–458. PMID 2686487. 
5. ^ C. Putensen, S. Zech, H. Wrigge, J. Zinserling, F. Stuber, T. Von Spiegel & N. Mutz (July 2001). "Long-term effects of spontaneous breathing during ventilatory support in patients with acute lung injury". American journal of respiratory and critical care medicine 164 (1): 43–49. PMID 11435237.