Topological excitations

2012-11-30T22:20:57Z

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[[File:Airway pressure release ventilation graph.png|thumb|right|A pressure-time graphic]][[File:Airway pressure release ventilation static pressure-volume figure 2007.jpg|thumb|Static pressure-volume curve during volume-controlled mechanical ventilation. High pressure ('P high') is set below the high inflection point (HIP) and low pressure is set above the low inflection point (LIP).<ref name="pmid19727373">{{cite journal| author=Daoud EG| title=Airway pressure release ventilation. | journal=Ann Thorac Med | year= 2007 | volume= 2 | issue= 4 | pages= 176–9 | pmid=19727373 | doi=10.4103/1817-1737.36556 | pmc=2732103 | url= }}</ref>]][[File:Airway pressure release ventilation additional figure 2007.jpg|thumb|Corresponding pressure and flow curves during one cycle of inflationdeflation. Notice the flow curve goes back to zero at the end of inflation, indicating full lung inflation; and also goes back to zero during the release period before inflation starts, indicating complete gas exhalation with no intrinsic PEEP.<ref name="pmid19727373"/>]]

'''Airway pressure release ventilation''' ('''APRV''') is a [[pressure control]] [[mode of mechanical ventilation]] that utilizes an [[inverse ratio ventilation]] strategy. APRV is an applied [[continuous positive airway pressure]] (CPAP) that at a set timed interval releases the applied pressure. Depending on the ventilator manufacturer, it may be referred to as BiVent. This is just as appropriate to use, since the only difference is that the term APRV is copyrighted. The Servo i ventilator does not have "APRV", it has the same thing, "BiVent".

== History ==
Airway pressure release ventilation was described initially by Stock and Downs in 1987<ref name="pmid3568710">{{cite journal| author=Downs JB, Stock MC| title=Airway pressure release ventilation: a new concept in ventilatory support. | journal=Crit Care Med | year= 1987 | volume= 15 | issue= 5 | pages= 459–61 | pmid=3568710 | doi= | pmc= | url= }}</ref><ref name="pmid3552443">{{cite journal| author=Stock MC, Downs JB, Frolicher DA| title=Airway pressure release ventilation. | journal=Crit Care Med | year= 1987 | volume= 15 | issue= 5 | pages= 462–6 | pmid=3552443 | doi= | pmc= | url= }}</ref> as a [[continuous positive airway pressure]] (CPAP) with an intermittent release phase. APRV begins at a pressure higher than the baseline pressure and follows with a deflation to accomplish tidal ventilation.<ref>Frawley PM, Habashi NM (2001) Airway pressure release ventilation: theory and practice. AACN Clin Issues 12:234-246</ref> 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.<ref>{{Cite journal | author = [[Dietrich Henzler]] | title = What on earth is APRV? | journal = [[Critical care (London, England)]] | volume = 15 | issue = 1 | pages = 115 | year = 2011 | month = | doi = 10.1186/cc9419 | pmid = 21345265 | pmc=3222047}}</ref>

== Indications ==
Based on clinical and experimental data, airway pressure release ventilation is indicated in patients with [[acute lung injury]],<ref name="pmid16236977">{{cite journal| author=Hering R, Zinserling J, Wrigge H, Varelmann D, Berg A, Kreyer S et al.| title=Effects of spontaneous breathing during airway pressure release ventilation on respiratory work and muscle blood flow in experimental lung injury. | journal=Chest | year= 2005 | volume= 128 | issue= 4 | pages= 2991–8 | pmid=16236977 | doi=10.1378/chest.128.4.2991 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16236977 }}</ref><ref name="pmid12883410">{{cite journal| author=Wrigge H, Zinserling J, Neumann P, Defosse J, Magnusson A, Putensen C et al.| title=Spontaneous breathing improves lung aeration in oleic acid-induced lung injury. | journal=Anesthesiology | year= 2003 | volume= 99 | issue= 2 | pages= 376–84 | pmid=12883410 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12883410 }}</ref> [[acute respiratory distress syndrome]]<ref name="pmid10194172">{{cite journal| author=Putensen C, Mutz NJ, Putensen-Himmer G, Zinserling J| title=Spontaneous breathing during ventilatory support improves ventilation-perfusion distributions in patients with acute respiratory distress syndrome. | journal=Am J Respir Crit Care Med | year= 1999 | volume= 159 | issue= 4 Pt 1 | pages= 1241–8 | pmid=10194172 | doi= | pmc= | url= }}</ref><ref name="pmid11511336">{{cite journal| author=Kaplan LJ, Bailey H, Formosa V| title=Airway pressure release ventilation increases cardiac performance in patients with acute lung injury/adult respiratory distress syndrome. | journal=Crit Care | year= 2001 | volume= 5 | issue= 4 | pages= 221–6 | pmid=11511336 | doi= | pmc=37408 | url= }}</ref> and [[atelectasis]]<ref name="pmid19727373"/> after major surgery

==Inverse ratio ventilation==
This is a type of [[inverse ratio ventilation]].<ref>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.</ref> The exhalation time (Tlow) 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.<ref>{{Cite journal | author = [[Adrian A. Maung]] & [[Lewis J. Kaplan]] | title = Airway pressure release ventilation in acute respiratory distress syndrome | journal = [[Critical care clinics]] | volume = 27 | issue = 3 | pages = 501–509 |date=July 2011 | doi = 10.1016/j.ccc.2011.05.003 | pmid = 21742214}}</ref><ref name="pmid8004312">{{cite journal| author=Sydow M, Burchardi H, Ephraim E, Zielmann S, Crozier TA| title=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. | journal=Am J Respir Crit Care Med | year= 1994 | volume= 149 | issue= 6 | pages= 1550–6 | pmid=8004312 | doi= | pmc= | url= }}</ref><ref name="pmid1914479">{{cite journal| author=Räsänen J, Cane RD, Downs JB, Hurst JM, Jousela IT, Kirby RR et al.| title=Airway pressure release ventilation during acute lung injury: a prospective multicenter trial. | journal=Crit Care Med | year= 1991 | volume= 19 | issue= 10 | pages= 1234–41 | pmid=1914479 | doi= | pmc= | url= }}</ref>

==Settings and measurements==
[[File:Airway pressure release ventilation figure 2007.jpg|thumb|Pressure-time curve for APRV. 'P high' is the high CPAP, 'P low' is the low CPAP, 'T high' is the duration of 'P high,' and 'T low' is the release period or the duration of 'P low.' Spontaneous breathing appears on the top of 'P high.'<ref name="pmid19727373"/>]]
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.
*'''Phigh''' — This is the inspiratory pressure (just like in pressure control).
*'''Thigh''' — This value is the number of seconds during the inhalation phase.
*'''Tpeep''' — Also known as the Tlow, this is the time allotted for expiration.
*'''FiO2''' — The fractional O2 percentage that is being added to the delivered air.

=== Mean airway pressure ===
[[Mean airway pressure]] on APRV is calculated by this formula:<ref name="pmid19727373"/>
:::<math>\frac{(P_{high} * T_{high})\, + (P_{low} * T_{low})} {T_{high} + T_{low}}</math>

==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.<ref>{{Cite journal | author = [[M. Baum]], [[H. Benzer]], [[C. Putensen]], [[W. Koller]] & [[G. Putz]] | title = [Biphasic positive airway pressure (BIPAP)--a new form of augmented ventilation] | journal = [[Der Anaesthesist]] | volume = 38 | issue = 9 | pages = 452–458 |date=September 1989 | pmid = 2686487 }}</ref> The term APRV has also been used in American journals where, from the ventilation characteristics, BIPAP would have been the appropriate terminology.<ref>{{Cite journal | author = [[C. Putensen]], [[S. Zech]], [[H. Wrigge]], [[J. Zinserling]], [[F. Stuber]], [[T. Von Spiegel]] & [[N. Mutz]]
| title = Long-term effects of spontaneous breathing during ventilatory support in patients with acute lung injury | journal = [[American journal of respiratory and critical care medicine]] | volume = 164 | issue = 1 | pages = 43–49 |date=July 2001 | pmid = 11435237 }}</ref> 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.<ref name="pmid10194172"/><ref name="pmid11506110">{{cite journal| author=Wrigge H, Zinserling J, Hering R, Schwalfenberg N, Stüber F, von Spiegel T et al.| title=Cardiorespiratory effects of automatic tube compensation during airway pressure release ventilation in patients with acute lung injury. | journal=Anesthesiology | year= 2001 | volume= 95 | issue= 2 | pages= 382–9 | pmid=11506110 | doi= | pmc= | url= }}</ref>

== 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 - ( C-1 ventilator by Hamilton)

==References==
<references/>
{{cite journal| author=Daoud EG, Farag HL, Chatburn RL| title=Airway pressure release ventilation: what do we know? | journal=Respir Care | year= 2012 | volume= 57 | issue= 2 | pages= 282–92 | pmid=21762559 | doi=10.4187/respcare.01238 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21762559 }}
{{Mechanical ventilation}}

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