A Bag-Valve-Mask (BVM), also known as a manual resuscitator, is a handheld device used to deliver positive pressure ventilation to individuals with inadequate or absent breathing. It provides essential respiratory support in emergency medical care. Understanding how to effectively use a BVM allows for rapid delivery of breaths and maintenance of oxygenation. This device is a standard component in resuscitation kits found in various settings, including ambulances and hospitals.
Components and Sizes
A BVM device consists of several key components that work together to facilitate ventilation: a self-inflating bag, a one-way valve, and a face mask. The self-inflating bag allows for manual compression to force air into the patient’s lungs. The one-way valve ensures that exhaled air does not re-enter the bag and directs fresh oxygen to the patient. The face mask is designed to fit securely over the patient’s nose and mouth, creating a seal necessary for effective ventilation.
Many BVMs also feature an oxygen inlet nipple, an oxygen reservoir, and an air intake valve. Connecting the BVM to an oxygen source, typically at 15 liters per minute, allows for the delivery of nearly 100% oxygen to the patient. Selecting the appropriate mask size is important for effective ventilation, as masks are available in adult, pediatric, and infant sizes. A properly sized mask covers the nose and mouth without extending over the chin or eyes, ensuring a tight seal and preventing air leakage.
When to Use a BVM
BVM ventilation is used in medical emergencies where breathing is insufficient or has ceased. This includes respiratory arrest, severe respiratory distress, hypercapnic or hypoxic respiratory failure, and apnea. It is also commonly employed when a patient has an altered mental status and cannot protect their airway.
The BVM is a temporary measure, often used until more definitive airway management, such as endotracheal intubation, can be established. It is also used during cardiopulmonary resuscitation (CPR) to deliver breaths. While there are no absolute medical contraindications to BVM ventilation, situations like complete upper airway obstruction or severe facial trauma may prevent an adequate mask seal, limiting its effectiveness.
Step-by-Step BVM Operation
Effective BVM operation begins with proper preparation and patient positioning. First, ensure the BVM is fully assembled and connected to an oxygen source if available. Position the patient supine on a firm surface.
Establishing a patent airway is essential, which can be achieved through maneuvers like the head-tilt/chin-lift or jaw-thrust. The head-tilt/chin-lift involves tilting the head back by pushing on the forehead and lifting the chin forward to move the tongue away from the throat. If a cervical spine injury is suspected, the jaw-thrust maneuver is preferred, which involves lifting the jaw forward without tilting the head to maintain spinal stability.
Once the airway is open, focus on achieving a tight mask seal. The pointed end of the mask should be placed over the nose, with the curved end just below the lower lip. The “C-E clamp” technique is commonly used for a one-person BVM, where the thumb and index finger form a “C” over the mask to press it onto the face, while the remaining three fingers form an “E” under the jaw to lift it and maintain the seal. For optimal sealing and to reduce fatigue, a two-person technique is often recommended, where one rescuer uses both hands to maintain the mask seal, and the second rescuer squeezes the bag. An alternative one-person, two-handed method involves placing the thenar eminences (base of the thumbs) along the mask’s lateral edges and lifting the mandible with the fingers.
When ventilating, steadily and smoothly squeeze the bag to deliver a breath over approximately one second. The appropriate rate of ventilation varies by age: for adults, one breath every 5 to 6 seconds (10-12 breaths per minute) is typical, while for infants and children, one breath every 3 to 5 seconds is recommended. The goal is to deliver a tidal volume just large enough to cause visible chest rise, typically 6 to 8 mL/kg for an average adult.
Avoid excessive squeezing, as the average adult BVM can hold around 1600 milliliters, and often only about one-third of the bag needs to be compressed to achieve adequate chest rise. After each breath, allow the chest to fall completely before delivering the next ventilation. Observing for visible chest rise and fall is a reliable indicator of effective ventilation.
Maximizing Ventilation Effectiveness
Maintaining a proper mask seal is a common challenge in BVM ventilation. Several techniques can enhance its effectiveness. The two-person BVM technique is generally more effective than the one-person method, as it allows for a more consistent seal and can reduce air leaks. One rescuer can dedicate both hands to securing the mask to the face, while the second rescuer focuses on squeezing the bag. If facial hair makes sealing difficult, a water-soluble lubricant can be applied to improve contact, and leaving dentures in place, if possible, can also help.
Observing adequate chest rise with each breath confirms that air is entering the lungs effectively. If chest rise is absent or minimal, reassessment of mask seal and airway patency is necessary. Care must be taken to avoid gastric insufflation, which occurs when air enters the stomach instead of the lungs. This can be minimized by delivering breaths slowly and with just enough volume to achieve chest rise, rather than forcefully squeezing the entire bag. Excessive pressure during ventilation can lead to air being pushed into the stomach, increasing the risk of regurgitation. The two-person technique also aids in minimizing gastric inflation by allowing for more controlled pressure and preventing over-ventilation.