Manual ventilation is a technique where a rescuer physically squeezes a bag to push air into the lungs of someone who isn’t breathing adequately on their own. It delivers positive pressure ventilation, meaning air is forced into the lungs rather than drawn in by the body’s natural breathing muscles. This is one of the most fundamental lifesaving skills in emergency medicine, used everywhere from ambulances to operating rooms.
How Manual Ventilation Works
The core device is called a bag-valve-mask, or BVM. It consists of three connected parts: a self-inflating bag, a one-way valve, and a face mask. When a rescuer squeezes the bag, the valve directs air through the mask and into the patient’s airway. When the bag is released, the valve closes so exhaled air escapes into the atmosphere rather than back into the bag, and the bag automatically reinflates with fresh air. Connected to an oxygen source, the device can deliver high-concentration oxygen with each squeeze.
The basic equipment setup includes the BVM device itself, an oxygen source with tubing, a pressure valve that maintains a small amount of air pressure in the lungs between breaths, and airway adjuncts (small plastic devices inserted into the nose or mouth to keep the tongue and soft tissue from blocking the airway).
When Manual Ventilation Is Used
Manual ventilation serves two main roles. The first is emergency ventilation when a mechanical ventilator isn’t available. This includes cardiac arrest situations both inside and outside the hospital, where someone has stopped breathing and needs immediate air delivery. The second role is short-term breathing support during transitions: the minutes before a patient is connected to a mechanical ventilator, during the process of placing a breathing tube, or while transporting a patient between hospital units or between facilities.
In both scenarios, the goal is the same. The patient either cannot breathe at all or is breathing too weakly to get enough oxygen into their blood and carbon dioxide out.
What Happens Inside the Lungs
Normal breathing works by negative pressure. Your diaphragm contracts, your chest expands, and air gets pulled in. Manual ventilation reverses that process entirely, using positive pressure to push air into the lungs from outside.
This forced air opens up tiny air sacs in the lungs that may have collapsed, a process called alveolar recruitment. As more air sacs open, the total surface area available for gas exchange increases, which means oxygen transfers into the blood more efficiently and carbon dioxide is removed more effectively. Maintaining a small amount of pressure between breaths (through a pressure valve on the device) keeps those air sacs from collapsing again during exhalation, further improving how well the lungs work.
Proper Technique and Positioning
Getting the mask to seal tightly against the face is the single biggest challenge. A poor seal means air leaks out around the edges instead of entering the lungs. Two-person ventilation is preferred whenever possible: one person uses both hands to hold the mask against the face while the second person squeezes the bag. This approach delivers more consistent and adequate air volumes than one person trying to do both jobs at once.
The patient is positioned on their back in what’s called the “sniffing position,” with the head tilted slightly back and the chin lifted forward. The goal is to align the ear canal with the notch at the top of the breastbone, which opens the upper airway as wide as possible. If the patient starts making snoring sounds during ventilation, that typically means the tongue has fallen back and is partially blocking the airway, signaling a need to reposition the head and jaw. In cases of suspected neck injury, the head stays in a neutral position and a jaw-thrust maneuver is used instead to avoid moving the spine.
How Much Air and How Often
The target for each breath is 5 to 8 milliliters of air per kilogram of the patient’s ideal body weight. For an average adult male of about 70 kilograms, that translates to roughly 350 to 560 milliliters per breath. That’s noticeably less than the full volume of most adult BVM bags, which hold over a liter. Squeezing the bag all the way is a common mistake that delivers too much air.
Breathing rates depend on age. For infants and children, the 2025 American Heart Association guidelines recommend 20 to 30 breaths per minute, or roughly one breath every 2 to 3 seconds. Adults receiving rescue breaths with a pulse generally receive about 10 to 12 breaths per minute, or one breath every 5 to 6 seconds.
Types of Manual Ventilation Bags
Two main types of bags exist: self-inflating and flow-inflating. Self-inflating bags refill on their own after each squeeze, making them simpler to use and the standard choice in most emergency settings. Flow-inflating bags require a continuous gas source to fill and demand more skill, but they offer finer control over pressure and can maintain steady pressure between breaths more reliably.
In a comparison of neonatal resuscitation devices, flow-inflating bags maintained sustained inflation pressure for 3.7 seconds compared to just 2.2 seconds for self-inflating bags. Flow-inflating bags also delivered more consistent pressure between breaths (4.4 cmH₂O vs. 3.6 cmH₂O with the self-inflating bag’s pressure valve attached). Self-inflating bags, on the other hand, allowed faster pressure changes, reaching target pressures in about 2.2 seconds. In neonatal care, a third option called a T-piece resuscitator provides the most precise and consistent pressures but responds more slowly to adjustments.
Risks of Manual Ventilation
The biggest risks come from delivering too much air, too fast, or at too high a pressure. Squeezing the bag too aggressively can force air into the stomach instead of the lungs, a problem called gastric insufflation. A stomach full of air raises the risk of vomiting, which can then be inhaled into the lungs. It also pushes the diaphragm upward, making it harder for the lungs to expand.
Excessive pressure can also injure lung tissue directly. The delicate air sacs can overstretch or rupture when exposed to pressures or volumes beyond what they’re designed to handle. This is why lung-protective volumes of 5 to 8 mL/kg are emphasized, and why pressure-release valves on BVM devices exist as a safety mechanism to vent excess pressure before it reaches dangerous levels.
Maintaining a good mask seal, using the correct bag size for the patient’s age and body size, and squeezing the bag slowly and steadily rather than forcefully are the primary ways to reduce these risks. Airway adjuncts help keep the airway open and reduce the effort needed to deliver each breath, which in turn lowers the pressure required.