Bag valve mask
A bag valve mask (BVM), sometimes known by the proprietary name Ambu bag or generically as a manual resuscitator or "self-inflating bag", is a hand-held device commonly used to provide positive pressure ventilation to patients who are not breathing or not breathing adequately. The device is a required part of resuscitation kits for trained professionals in out-of-hospital settings (such as ambulance crews) and is also frequently used in hospitals as part of standard equipment found on a crash cart, in emergency rooms or other critical care settings. Underscoring the frequency and prominence of BVM use in the United States, the American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care recommend that "all healthcare providers should be familiar with the use of the bag-mask device."[1] Manual resuscitators are also used within the hospital for temporary ventilation of patients dependent on mechanical ventilators when the mechanical ventilator needs to be examined for possible malfunction or when ventilator-dependent patients are transported within the hospital. Two principal types of manual resuscitators exist; one version is self-filling with air, although additional oxygen (O2) can be added but is not necessary for the device to function. The other principal type of manual resuscitator (flow-inflation) is heavily used in non-emergency applications in the operating room to ventilate patients during anesthesia induction and recovery.
Bag valve mask
Use of manual resuscitators to ventilate a patient is frequently called "bagging" the patient[2] and is regularly necessary in medical emergencies when the patient's breathing is insufficient (respiratory failure) or has ceased completely (respiratory arrest). Use of the manual resuscitator force-feeds air or oxygen into the lungs in order to inflate them under pressure, thus constituting a means to manually provide positive-pressure ventilation. It is used by professional rescuers in preference to mouth-to-mouth ventilation, either directly or through an adjunct such as a pocket mask.
History[edit]
The bag valve mask concept was developed in 1956 by the German engineer Holger Hesse and his partner, Danish anaesthetist Henning Ruben, following their initial work on a suction pump.[3] Hesse's company was later renamed Ambu A/S, which has manufactured and marketed the device since 1956. An Ambu bag is a self-inflating bag resuscitator from Ambu A/S, which still manufactures and markets self-inflating bag resuscitators.
Today there are several manufacturers of self-inflating bag resuscitators. Some, like the original Ambu bag, are durable and intended for reuse after thorough cleaning. Others are inexpensive and intended for single patient use.
Initially produced in one size, BVMs are now available in sizes for use with infants, children or adults.
Bag valve masks used in combat[edit]
Airway obstruction is a leading cause of death in battlefield trauma.[7] Airway management in combat is very different from its civilian equivalent. In combat, maxillofacial trauma is the primary cause of airway obstruction. The injury is frequently complicated by a struggling patient, distorted anatomy, and blood,[8] and these injuries often have significant associated hemorrhage from accompanying vascular injuries.[9]
Military paramedics face extreme challenges, including "darkness, hostile fire, resource limitations, prolonged evacuation times, unique casualty transportation issues, command and tactical decisions affecting health care, hostile environments and provider experience levels".[10] They often have to treat multiple casualties using only the equipment they are carrying on their backs. Therefore, space is of primary importance and compact bag valve masks, such as a Pocket BVM, have been created to save valuable space in the emergency kit.
Additional components and features[edit]
Filters[edit]
A filter is sometimes placed between the mask and the bag (before or after the valve) to prevent contamination of the bag.
Positive end-expiratory pressure[edit]
Some devices have PEEP valve connectors, for better positive airway pressure maintenance.
Medication delivery[edit]
A covered port may be incorporated into the valve assembly to allow inhalatory medicines to be injected into the airflow, which may be particularly effective in treating patients in respiratory arrest from severe asthma.
Airway pressure port[edit]
A separate covered port may be included into the valve assembly to enable a pressure-monitoring device to be attached, enabling rescuers to continuously monitor the amount of positive-pressure being generated during forced lung inflation.
Pressure relief valves[edit]
A pressure relief valve (often known as a "pop-up valve") is typically included in pediatric versions and some adult versions, the purpose of which is to prevent accidental over-pressurization of the lungs. A bypass clip is usually incorporated into this valve assembly in case medical needs call for inflation at a pressure beyond the normal cutoff of the pop-up valve.
Device storage features[edit]
Some bags are designed to collapse for storage. A bag not designed to store collapsed may lose elasticity when stored compressed for long periods, reducing its effectiveness. The collapsible design has longitudinal scoring so that the bag collapses on the scoring "pivot point," opposite to the direction of normal bag compression.
Manual resuscitator alternatives[edit]
In a hospital, long-term mechanical ventilation is provided by using a more complex, automated ventilator. However, a frequent use of a manual resuscitator is to temporarily provide manual ventilation whenever troubleshooting of the mechanical ventilator is needed, if the ventilator circuit needs to be changed, or if there is a loss of electrical power or source of compressed air or oxygen. A rudimentary type of mechanical ventilator device that has the advantage of not needing electricity is a flow-restricted, oxygen-powered ventilation device (FROPVD). These are similar to manual resuscitators in that oxygen is pushed through a mask to force-inflate the patient's lungs, but unlike a manual resuscitator where the pressure used to force-inflate the patient's lungs comes from a person manually squeezing a bag, with the FROPVD the pressure needed to force-inflate the lungs comes directly from a pressurized oxygen cylinder. These devices will stop functioning when the compressed oxygen tank becomes depleted.