What is an APL valve?

The pressure limitation valve, known by its acronym (APL), is a device that controls the distribution in the release of anesthetic gases, establishes pressure limits for manual ventilation in the breathing circuit by means of a diaphragm. The gases flow from the patient to the scanning system via the APL valve, where pressure fluctuates regularly.

Likewise, it allows to vary the pressure inside the anesthetic system, using a unidirectional valve with spring, controls the gas leak and allows the control of the aerial pressure of the patient’s life. The minimum pressure required to open the valve is 1cm H2O used as a safety mechanism to prevent the pressure from exceeding 60cm H2O, therefore it should be taken into account that pressures below this value can lead to low trauma.

Functions of the APL Valve within the Respiratory Systems of Anesthesia

The Respiration System is connected to the patient and the anesthesia machine, which allows the leakage of anesthetic gas controlled through various methods, such as:ย 

  • Mapleson A System: It develops through the connection of a bag from the anesthesia machine and the APL valve, to the patient, when subjected to non-spontaneous ventilation and passes through the valve before reaching the cavities, Therefore, causes a high fresh gas flow in order to avoid reinhalation.
  • Mapleson B & C Systems: this acts as a reservoir and the APL valve is between the flow of fresh gas and the patient, which comes out fresh gas that has not been involved in the exchange of gases during expiration along with the expired gases in spontaneous ventilation.
  • Mapleson D System: the reservoir bag and the APL valve are installed at the end of the anesthetic machine and are separated from the patient by 180cm of pipe so as not to be an obstacle of entry of the fresh gas that filters the valve.
  • Mapleson E & F Systems: by means of the APL valve, offers fresh flow ventilation that is deposited in the reservoir bag in pediatric patients up to 30kg, A gas flow rate of 2 to 3 times the minute volume is needed to avoid reinhalation.

Advantages and Disadvantages of the APL Valve

The APL valve is responsible for releasing fresh gases that enter the circle connected to the anesthesia machine outlet, in an inspiratory and expiratory way, incorporated into the system to ensure unidirectional flow in the connections.ย 

Advantages include relative constancy of inspired concentration, conservation of humidity and temperature in the respiratory system and reduction in operating room contamination. It can be used, for the administration of anesthesia with a closed system and for the use of low flows. Other benefits include:

  • High tear resistance and temperature resistance.
  • High stiffness and hardness.
  • High Crystalline.
  • Fully healed and durable.
  • Low friction coefficient.
  • High flexibility and tensile strength.
  • Water-resistant and non-toxic.
  • Excellent dimensional stability.

Its biggest disadvantage is the complexity of its design, because it has several connections that are not viable in places to leak, causing serious problems. Reinhalation, can occur if the valves stay stuck at the top of the dome. A complete occlusion, it is possible to stay stuck at its base. Unidirectional valves can get stuck by water vapor inside the system leading to increased dead space.

Anesthesia Machine in Kalstein

At Kalstein, we provide the anesthesia solution, with equipment that meets all international standards, meeting the needs and demands that the media require. They are YR-series equipment, with expansion of the modern anesthesia workstation, is also feasible to greatly improve workflow and reduce operating costs. In addition, it offers the electronic PEEP function. It has automatic current volume compensation, provides a high precision output of only 20 ml. It uses latex-free and autoclavable components. It can be easily maintained and cleaned without specialized tools. It is CE certified, giving users peace of mind.ย 

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