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A case of adjustable pressure-limiting (APL) valve failure
Journal of Clinical Anesthesia (2011) 23, 58–60
Case report
A case of adjustable pressure-limiting (APL) valve failure Adriana Dana Oprea MD (Resident in Anesthesiology)⁎, Jan Ehrenwerth MD (Professor of Anesthesiology), Paul G Barash MD (Professor of Anesthesiology) Department of Anesthesiology, Yale University, 333 Cedar St., TMP 3, P.O. Box 208051, New Haven, CT 06520-8051 Received 20 June 2009; revised 9 October 2009; accepted 11 October 2009
Keywords: Adjustable pressure-limiting valve: complications; Anesthesia equipment failure; Manual ventilation
Abstract The adjustable pressure-limiting (APL) valve controls airway pressure during manual ventilation. Failure of the APL valve during induction of anesthesia may occur, and the anesthesiologist must be aware of solutions for this occurrence. © 2011 Elsevier Inc. All rights reserved.
1. Introduction Anesthesia equipment failure may result in morbidity and mortality. The frequency of anesthetic equipment failure is estimated to be between 0.04k and 0.23k, with one to two thirds of events directly related to malfunction of the anesthesia machine and one third due to human-related errors [1,2]. A case of an adjustable pressure-limiting (APL) valve knob dislodgement during induction of general anesthesia is presented, and its influence on subsequent anesthetic management is discussed.
2. Case report A 46 year-old woman was scheduled to have a laparoscopic left salpingectomy. Prior to induction of general anesthesia, the anesthesia machine, a Datex-Ohmeda GE Aestiva 5 (Datex-Ohmeda, Inc., Madison, WI, USA) ⁎ Corresponding author. Tel.: +1 203 785-2802; fax: +1 203 785 6664. E-mail address: [email protected] (A.D. Oprea). 0952-8180/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jclinane.2009.10.020
was thoroughly checked, according to the 2008 Recommendations for Pre-Anesthesia Checkout Procedures of the ASA, and no malfunction was found1. Following intravenous induction of anesthesia with propofol, bag-mask ventilation was attempted prior to administration of a muscle relaxant (succinylcholine 100 mg). Upon attempting to close the APL valve, the knob was found to be dislodged. Despite several attempts to reseat the valve in its proper location, it could not be reconnected to the anesthesia machine (Figs. 1 and 2). We noticed that underneath the knob, the APL valve has a bhold-down baseQ (ie, the ring that locks the valve to the control panel). Visual examination found that the molded APL valve actuator (knob assembly) had become separated at the base where it was retained by a mechanical snap fitting (Fig. 3). To provide positive pressure ventilation, an assistant had to manually hold the APL in place.
1 2008 Recommendations for Pre-Anesthesia Checkout Procedures. American Society of Anesthesiologists: http://www.asahq.org/clinical/ FINALCheckoutDesignguidelines02-08-2008.pdf. (last accessed June 8, 2009).
Adjustable pressure limiting valve failure
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Fig. 3 The components of the adjustable pressure-limiting (APL) valve. Left to right: molded APL valve actuator, spring, spiral ring (used as spacer with older control panels), hold-down base, APL diaphragm (with poppet and cage). (Figure reproduced with permission from Datex-Ohmeda, Inc., Madison, WI, USA).
Fig. 1 View of the separation of the adjustable pressure-limiting (APL) valve knob from the valve mechanism in the present case.
After successful mask ventilation and testing of the backup ventilation equipment, the muscle relaxant was administered, the trachea was intubated, and mechanical ventilation was initiated, thus bypassing the valve. During mechanical ventilation, the other components of the anesthesia machine functioned properly. The biomedical engineering service was able temporarily to reposition the APL valve's knob. The surgical procedure was completed without any adverse effects.
3. Discussion The anesthesia machine is equipped with a user APL valve, which controls the pressure in the breathing system during spontaneous or manual ventilation. The APL valve is
Fig. 2 View of the adjustable pressure-limiting (APL) valve base as it separated from the knob assembly.
comprised of a sealing diaphragm held in place by a spring. Most APL valves have a rotary knob designed so that a clockwise motion controls the spring tension and ultimately closes the valve (Fig. 3). The degree of spring tension and the bag compression dictate the pressure in the breathing system and the pressure at which gases are vented to the scavenging system2. Malfunctioning of the APL valve has been described in the anesthesia literature. Shortly after the introduction of the APL valves, Nelson and Snowdon reported failure of these valves, while apparently shut, by the plastic disc being tilted on its spindle and keeping the valve open [3]. Ortega and Zambricki described a warped decoupling valve, which led to ineffective tidal volumes during mechanical ventilation [4]. More recently, leakage in the anesthesia circuit during manual ventilation due to a gas sensing line that caused a malfunction of the APL valve, was reported [5]. There are other case reports of increases in airway pressure due to a faulty valve [6-8]. However, a literature search combined with an interrogation of the FDA MAUDE (Manufacturer and User Facility Device Experience) database in June 2009 did not yield any reports of APL knob dislodgement on the DatexOhmeda anesthesia machines3. However, The MAUDE database did report several cases of APL valve detachment with Draeger Fabius anesthesia machines. As a result, in September 2004, there was a recall of APL valves used on Fabius GS, Fabius Tiro, and Narcomed 6000 because qthe rotating knob of the rotary style APL valve can become separated from the assemblyq. In this case, the malfunctioning APL valve was examined and the cause of the knob dislodgement ultimately was found. Despite a prior thorough machine check, the anesthesia machine may have been moved moved in the
2 Datex-Ohmeda: installation instructions for field use. Installing a molded APL Valve actuator, Kit 1406-8202-000 in an Aestiva 3000 Anesthesia Machine. Madison, WI: Datex-Ohmeda, Inc; 1999. p.1-5. 3 MAUDE (Manufacturer and User Facility Device Experience). U.S. Food and Drug Administration: http://www.accessdata.fda.gov/scripts/ cdrh/cfdocs/cfMAUDE/search.CFM (last accessed June 8, 2009).
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A.D. Oprea et al. logistically difficult and manual ventilation was achieved, the case proceeded. In conclusion, when an APL valve malfunctions, several options exist. The anesthesia machine may be exchanged for a functioning workstation. The other option involves holding the APL in place, or using the anesthesia ventilator, thus bypassing the APL valve. In an emergency, another option is to disconnect the anesthesia machine altogether and to use the self-inflating bag to ensure adequate ventilation.
References
Fig. 4 View of the bag-handle bar motion towards the adjustable pressure-limiting (APL) valve, with the potential for damaging the valve mechanism.
room by using and forcing the bag-handle bar over the APL knob, causing it to become dislodged (Fig. 4). The APL dislodgement probably occurred after machine checkout but before the start of the case, prior to induction. This dislodgement was not apparent at the beginning of the case. By placing the APL valve into position over the spring and applying pressure, the knob was held in place and the spring mechanism adjusted. Since exchange of the anesthesia machine at this point in the anesthetic was
[1] Fasting S, Gisvold SE. Equipment problems during anaesthesia–are they a quality problem? Br J Anaesth 2002;89:825-31. [2] Klanarong S, Chau-in W, Pulnitiporn A, Pengpol W. The Thai Anesthesia Incidents Study (THAI Study) of anesthetic equipment failure/malfunction: a qualitative analysis for risk factors. J Med Assoc Thai 2005;88(Suppl 7):S134-S140. [3] Nelson RA, Snowdon SL. Failure of an adjustable pressure limiting valve. Anaesthesia 1989;44:788-9. [4] Ortega RA, Zambricki ER. Fresh gas decoupling valve failure precludes mechanical ventilation in a Draeger Fabius GS anesthesia machine. Anesth Analg 2007;104:1000-1. [5] Eggemann I, Böttiger BW, Spöhr F. Accidentally opened adjustable pressure-limiting valve. Failure of manual ventilation. Anaesthesist 2009;58:301-2. [6] Souvatzis X, Askitopoulou H. Malfunction of an adjustable pressure limit valve. Eur J Anaesthesiol 2007;24:978-80. [7] Sanders R. A new APL valve hazard. Anaesthesia 2001;56:1119-20. [8] Primiano FP Jr. Open adjustable pressure limiter valve. Anesthesiology 1998;88:552.
Case report
A case of adjustable pressure-limiting (APL) valve failure Adriana Dana Oprea MD (Resident in Anesthesiology)⁎, Jan Ehrenwerth MD (Professor of Anesthesiology), Paul G Barash MD (Professor of Anesthesiology) Department of Anesthesiology, Yale University, 333 Cedar St., TMP 3, P.O. Box 208051, New Haven, CT 06520-8051 Received 20 June 2009; revised 9 October 2009; accepted 11 October 2009
Keywords: Adjustable pressure-limiting valve: complications; Anesthesia equipment failure; Manual ventilation
Abstract The adjustable pressure-limiting (APL) valve controls airway pressure during manual ventilation. Failure of the APL valve during induction of anesthesia may occur, and the anesthesiologist must be aware of solutions for this occurrence. © 2011 Elsevier Inc. All rights reserved.
1. Introduction Anesthesia equipment failure may result in morbidity and mortality. The frequency of anesthetic equipment failure is estimated to be between 0.04k and 0.23k, with one to two thirds of events directly related to malfunction of the anesthesia machine and one third due to human-related errors [1,2]. A case of an adjustable pressure-limiting (APL) valve knob dislodgement during induction of general anesthesia is presented, and its influence on subsequent anesthetic management is discussed.
2. Case report A 46 year-old woman was scheduled to have a laparoscopic left salpingectomy. Prior to induction of general anesthesia, the anesthesia machine, a Datex-Ohmeda GE Aestiva 5 (Datex-Ohmeda, Inc., Madison, WI, USA) ⁎ Corresponding author. Tel.: +1 203 785-2802; fax: +1 203 785 6664. E-mail address: [email protected] (A.D. Oprea). 0952-8180/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jclinane.2009.10.020
was thoroughly checked, according to the 2008 Recommendations for Pre-Anesthesia Checkout Procedures of the ASA, and no malfunction was found1. Following intravenous induction of anesthesia with propofol, bag-mask ventilation was attempted prior to administration of a muscle relaxant (succinylcholine 100 mg). Upon attempting to close the APL valve, the knob was found to be dislodged. Despite several attempts to reseat the valve in its proper location, it could not be reconnected to the anesthesia machine (Figs. 1 and 2). We noticed that underneath the knob, the APL valve has a bhold-down baseQ (ie, the ring that locks the valve to the control panel). Visual examination found that the molded APL valve actuator (knob assembly) had become separated at the base where it was retained by a mechanical snap fitting (Fig. 3). To provide positive pressure ventilation, an assistant had to manually hold the APL in place.
1 2008 Recommendations for Pre-Anesthesia Checkout Procedures. American Society of Anesthesiologists: http://www.asahq.org/clinical/ FINALCheckoutDesignguidelines02-08-2008.pdf. (last accessed June 8, 2009).
Adjustable pressure limiting valve failure
59
Fig. 3 The components of the adjustable pressure-limiting (APL) valve. Left to right: molded APL valve actuator, spring, spiral ring (used as spacer with older control panels), hold-down base, APL diaphragm (with poppet and cage). (Figure reproduced with permission from Datex-Ohmeda, Inc., Madison, WI, USA).
Fig. 1 View of the separation of the adjustable pressure-limiting (APL) valve knob from the valve mechanism in the present case.
After successful mask ventilation and testing of the backup ventilation equipment, the muscle relaxant was administered, the trachea was intubated, and mechanical ventilation was initiated, thus bypassing the valve. During mechanical ventilation, the other components of the anesthesia machine functioned properly. The biomedical engineering service was able temporarily to reposition the APL valve's knob. The surgical procedure was completed without any adverse effects.
3. Discussion The anesthesia machine is equipped with a user APL valve, which controls the pressure in the breathing system during spontaneous or manual ventilation. The APL valve is
Fig. 2 View of the adjustable pressure-limiting (APL) valve base as it separated from the knob assembly.
comprised of a sealing diaphragm held in place by a spring. Most APL valves have a rotary knob designed so that a clockwise motion controls the spring tension and ultimately closes the valve (Fig. 3). The degree of spring tension and the bag compression dictate the pressure in the breathing system and the pressure at which gases are vented to the scavenging system2. Malfunctioning of the APL valve has been described in the anesthesia literature. Shortly after the introduction of the APL valves, Nelson and Snowdon reported failure of these valves, while apparently shut, by the plastic disc being tilted on its spindle and keeping the valve open [3]. Ortega and Zambricki described a warped decoupling valve, which led to ineffective tidal volumes during mechanical ventilation [4]. More recently, leakage in the anesthesia circuit during manual ventilation due to a gas sensing line that caused a malfunction of the APL valve, was reported [5]. There are other case reports of increases in airway pressure due to a faulty valve [6-8]. However, a literature search combined with an interrogation of the FDA MAUDE (Manufacturer and User Facility Device Experience) database in June 2009 did not yield any reports of APL knob dislodgement on the DatexOhmeda anesthesia machines3. However, The MAUDE database did report several cases of APL valve detachment with Draeger Fabius anesthesia machines. As a result, in September 2004, there was a recall of APL valves used on Fabius GS, Fabius Tiro, and Narcomed 6000 because qthe rotating knob of the rotary style APL valve can become separated from the assemblyq. In this case, the malfunctioning APL valve was examined and the cause of the knob dislodgement ultimately was found. Despite a prior thorough machine check, the anesthesia machine may have been moved moved in the
2 Datex-Ohmeda: installation instructions for field use. Installing a molded APL Valve actuator, Kit 1406-8202-000 in an Aestiva 3000 Anesthesia Machine. Madison, WI: Datex-Ohmeda, Inc; 1999. p.1-5. 3 MAUDE (Manufacturer and User Facility Device Experience). U.S. Food and Drug Administration: http://www.accessdata.fda.gov/scripts/ cdrh/cfdocs/cfMAUDE/search.CFM (last accessed June 8, 2009).
60
A.D. Oprea et al. logistically difficult and manual ventilation was achieved, the case proceeded. In conclusion, when an APL valve malfunctions, several options exist. The anesthesia machine may be exchanged for a functioning workstation. The other option involves holding the APL in place, or using the anesthesia ventilator, thus bypassing the APL valve. In an emergency, another option is to disconnect the anesthesia machine altogether and to use the self-inflating bag to ensure adequate ventilation.
References
Fig. 4 View of the bag-handle bar motion towards the adjustable pressure-limiting (APL) valve, with the potential for damaging the valve mechanism.
room by using and forcing the bag-handle bar over the APL knob, causing it to become dislodged (Fig. 4). The APL dislodgement probably occurred after machine checkout but before the start of the case, prior to induction. This dislodgement was not apparent at the beginning of the case. By placing the APL valve into position over the spring and applying pressure, the knob was held in place and the spring mechanism adjusted. Since exchange of the anesthesia machine at this point in the anesthetic was
[1] Fasting S, Gisvold SE. Equipment problems during anaesthesia–are they a quality problem? Br J Anaesth 2002;89:825-31. [2] Klanarong S, Chau-in W, Pulnitiporn A, Pengpol W. The Thai Anesthesia Incidents Study (THAI Study) of anesthetic equipment failure/malfunction: a qualitative analysis for risk factors. J Med Assoc Thai 2005;88(Suppl 7):S134-S140. [3] Nelson RA, Snowdon SL. Failure of an adjustable pressure limiting valve. Anaesthesia 1989;44:788-9. [4] Ortega RA, Zambricki ER. Fresh gas decoupling valve failure precludes mechanical ventilation in a Draeger Fabius GS anesthesia machine. Anesth Analg 2007;104:1000-1. [5] Eggemann I, Böttiger BW, Spöhr F. Accidentally opened adjustable pressure-limiting valve. Failure of manual ventilation. Anaesthesist 2009;58:301-2. [6] Souvatzis X, Askitopoulou H. Malfunction of an adjustable pressure limit valve. Eur J Anaesthesiol 2007;24:978-80. [7] Sanders R. A new APL valve hazard. Anaesthesia 2001;56:1119-20. [8] Primiano FP Jr. Open adjustable pressure limiter valve. Anesthesiology 1998;88:552.