The Bag-Valve-Mask (BVM), often called an Ambu bag, is a handheld device that provides positive pressure ventilation to patients experiencing respiratory arrest or inadequate breathing. This manual resuscitator forces air or oxygen into the lungs when the patient cannot breathe effectively. Proper operation is fundamental in emergency situations, as the correct duration and frequency of squeezing the bag directly impacts a patient’s oxygenation and chance of survival. The intervention’s success depends on the rescuer synchronizing the bag squeeze with established physiological guidelines.
Understanding the Bag-Valve-Mask Device
The Bag-Valve-Mask is a three-part system: a flexible, self-inflating bag, a one-way valve, and a face mask. The rescuer manually compresses the bag to deliver a breath, and it automatically reinflates using ambient air or supplemental oxygen. The one-way valve directs the flow of gas toward the patient, preventing the patient’s exhaled breath from returning into the bag. A tight-fitting face mask is placed over the patient’s nose and mouth to create a sealed circuit for the delivered air.
The BVM manually delivers positive pressure ventilation, inflating the patient’s lungs by pushing air in under pressure. This intervention is used in both pre-hospital and hospital settings for patients in respiratory failure or during cardiopulmonary resuscitation (CPR). Delivering breaths helps maintain adequate oxygen levels until a more definitive airway management technique can be established. In a clinical setting, the BVM is connected to an oxygen source flowing at 10 to 15 liters per minute to maximize the oxygen concentration delivered.
Proper Ventilation Timing for Adults
Proper BVM timing for adults depends on whether the patient has a pulse (rescue breathing) or is in cardiac arrest receiving chest compressions (CPR). For a patient who is not breathing but has a pulse, the recommended rate is one breath every five to six seconds. This translates to a ventilation rate of 10 to 12 breaths per minute, which helps prevent hyperventilation. Each individual squeeze of the bag should be a smooth, gentle compression lasting approximately one second.
During active CPR on an adult, the ventilation rate is adjusted to minimize interruptions to chest compressions. If an advanced airway, such as an endotracheal tube, is not in place, the standard compression-to-ventilation ratio is 30 compressions followed by two breaths. If a definitive advanced airway is secured, chest compressions become continuous. In this case, the rescuer must deliver one breath every six seconds, maintaining a steady rate of ten breaths per minute, regardless of the compression cycle. Adhering to the one-second squeeze duration ensures proper gas exchange without causing excessive pressure.
Specific Timing Guidelines for Infants and Children
Ventilation timing for pediatric patients requires a faster rate than for adults due to their higher metabolic demands. For a child who is not breathing but has a pulse, the appropriate rate is one breath every three to five seconds. This results in a ventilation rate of 12 to 20 breaths per minute. As with adults, each breath should be delivered over approximately one second with a gentle, controlled squeeze.
When performing CPR on a child, the compression-to-ventilation ratio differs based on the number of rescuers present. In a single-rescuer scenario, the ratio is 30 compressions to two breaths, similar to the adult standard. When two or more rescuers are present, the recommended ratio changes to 15 compressions to two breaths. This adjustment prioritizes ventilation because respiratory issues are often the primary cause of cardiac arrest in children. Regardless of the ratio, the individual squeeze duration for each delivered breath should remain around one second.
Technique: Ensuring Effective and Safe Breaths
The physical act of squeezing the BVM must be executed with precision and control, regardless of the patient’s age or required rate. The squeeze should last for about one second, allowing air to enter the lungs gradually and reducing the risk of forcing air into the stomach. The measure of an effective squeeze is the visible rise of the patient’s chest, not the amount of bag compressed. Only a modest chest rise is necessary, indicating that adequate tidal volume (typically 500 to 600 milliliters for an adult) has been delivered.
A proper mask seal is paramount for effective ventilation, often achieved using the E-C clamp technique. In this technique, the thumb and index finger form a “C” around the mask to press it onto the face, while the remaining three fingers form an “E” to lift the jaw and maintain an open airway. Rescuers must avoid over-ventilation, which involves delivering breaths too fast or with too much volume. Excessive force or speed can raise pressure in the chest, potentially causing gastric inflation, vomiting, aspiration, and decreased blood return to the heart.