How to Perform Bag-Valve-Mask (BVM) Ventilation

Bag-valve-mask ventilation is a manual method of pushing air into a patient’s lungs using a self-inflating bag, a one-way valve, and a face mask pressed over the nose and mouth. It remains one of the most widely used emergency ventilation techniques in medicine, from hospital codes to roadside resuscitations, because it requires no power source, works in virtually any environment, and can be set up in seconds. Despite its apparent simplicity, performing it well is surprisingly difficult, and the difference between good and poor BVM technique can determine whether a patient lives, dies, or suffers brain damage.

How the Device Works

A BVM consists of three parts connected in series. The self-inflating bag is a compressible reservoir, typically holding about 1,600 mL for an adult device and smaller volumes for pediatric sizes. When you squeeze the bag, air travels through a one-way valve that prevents exhaled gas from flowing back into the bag, and then through a face mask that seals over the patient’s nose and mouth. When you release your grip, the bag re-expands on its own, drawing in fresh air or supplemental oxygen through an inlet at the rear. The Danish anesthesiologist Henning Ruben designed the first commercially successful version in 1957, and a similar device was soon developed by Asmund Laerdal of Norway in collaboration with American anesthesiologists.

The device can be connected to an oxygen source. Without a reservoir attachment, a self-inflating bag connected to oxygen at flow rates above 7 liters per minute delivers a fraction of inspired oxygen (FiO2) of roughly 0.5 to 0.6.¹ Adding an oxygen reservoir tail and running the flow at 10 to 12 liters per minute brings that above 0.8, and some devices reach close to 1.0 (pure oxygen) at those rates.² Not all bags perform identically, though. Testing of different brands has shown that the position of the oxygen inlet and the internal geometry of the bag affect how quickly oxygen concentration rises. During simulated CPR, both major brands tested achieved FiO2 values above 0.85 within about a minute at 10 liters per minute of flow.³

One-Person Versus Two-Person Technique

The hardest part of BVM ventilation is not squeezing the bag. It is sealing the mask. One person has to hold the mask against the face with one hand while squeezing the bag with the other, and it is extremely common for air to leak around the edges. The standard solo technique uses a “C-E” grip: the thumb and index finger press the mask down in a C shape, while the remaining three fingers hook under the jaw in an E shape to lift it forward and maintain an open airway. In practice, this is a juggling act, and performance suffers.

When a second rescuer is available, one person uses both hands to hold the mask and lift the jaw while the other squeezes the bag. Studies consistently show that the two-person method delivers more air. In manikin testing with infants and children, the two-person technique produced higher tidal volumes per kilogram of body weight than the one-person technique in both infant and child models.⁴ A randomized trial in preterm newborns found that mask leak was significantly higher with the one-person method, averaging about 26% compared with roughly 18% with two people.⁵ When you are alone, the two-person method is obviously impossible, but whenever a second pair of hands is present, switching to it is one of the simplest ways to improve ventilation quality.

Predicting Who Will Be Hard to Ventilate

Some patients are straightforward to mask-ventilate; others are a nightmare. Anesthesiologists have studied this extensively because they mask-ventilate nearly every patient they put to sleep, and occasionally encounter someone whose anatomy defeats the technique. The risk factors that show up again and again across multiple large studies include obesity (especially a body mass index above 26 to 35, depending on the study), a history of snoring or obstructive sleep apnea, presence of a beard, age over 55, lack of teeth, a thick or short neck, and a high Mallampati score, which reflects how much of the throat is visible when a person opens their mouth wide.⁶

A landmark study of over a thousand surgical patients found that when two or more of those independent risk factors were present, the likelihood of difficult mask ventilation jumped substantially.⁷ Later work added neck circumference of 40 cm or greater and a history of difficult intubation to the list.⁸ A prospective study in high-risk surgical patients confirmed that snoring history, BMI above 35, beard, and high Mallampati score each independently raised the odds of difficult ventilation by roughly two to three times.⁹

A beard deserves special mention because it is the one risk factor that a patient or provider can actually do something about. Facial hair breaks the seal between the mask’s cushion and the skin. In an emergency, there is no time to shave anyone, but in planned situations like preoxygenation before intubation, clinicians sometimes apply a water-soluble lubricant or place a transparent film dressing over the beard to improve the seal. Edentulous patients (those without teeth) pose a different sealing challenge: the cheeks collapse inward, making it hard to maintain mask contact. Leaving dentures in during mask ventilation, if safe to do so, helps preserve facial structure.

The Role of PEEP in Preoxygenation

Before intubation or during resuscitation, BVM ventilation is often used to load the lungs with oxygen, a process called preoxygenation. A 2025 randomized trial compared three preoxygenation methods in healthy volunteers and children: a non-rebreather mask alone, a BVM without positive end-expiratory pressure (PEEP), and a BVM with PEEP. Adding PEEP to BVM ventilation consistently improved exhaled oxygen fractions. In normal-weight adults, adding PEEP raised the end-preoxygenation oxygen fraction from about 72% to about 76%. The benefit was even more pronounced in overweight and obese adults, where PEEP boosted the fraction from about 66% to 73%.¹⁰

PEEP works by keeping the small airways and alveoli open at the end of each breath, preventing them from collapsing. This is especially valuable in people with extra weight compressing their chest and abdomen. The same trial showed that PEEP increased ventilation in the dependent (lower) lung regions, where gravity tends to cause the most collapse, compared with BVM alone.¹¹ Many modern BVM setups include an adjustable PEEP valve that attaches between the bag and the mask. It is a small addition that meaningfully improves oxygenation, particularly for patients who are already at a disadvantage.

Airway Adjuncts and Why They Matter

A BVM on its own delivers air to the face. Getting that air into the lungs requires an open airway, and in an unconscious patient the tongue tends to fall backward and obstruct the throat. Jaw thrust and head tilt help, but simple plastic devices called airway adjuncts make a real difference. Oropharyngeal airways (rigid curved tubes inserted over the tongue) and nasopharyngeal airways (soft flexible tubes inserted through the nostril) physically hold the airway open.

A study of in-hospital cardiac arrests found that BVM ventilation combined with these airway adjuncts improved neurological outcomes, with an odds ratio of about 3.5 compared with BVM alone.¹² That is a large effect, and it underscores a point many providers underappreciate: the mask seal and bag squeeze are only part of the equation. If the airway is not patent, nothing else matters. Tactical combat casualty care guidelines now explicitly recommend considering a nasopharyngeal airway when performing BVM ventilations on casualties with impaired ventilation and oxygen saturations below 90%.¹³

Pediatric BVM Ventilation

Children are not small adults when it comes to BVM ventilation. Their airways are narrower, their lung volumes are tiny relative to adult bags, and the margin for error is slim. Overventilation in a small child can cause serious lung injury, because the pressures and volumes that are safe for an adult will overdistend a child’s lungs. Even among trained providers, excessive ventilation volumes and rates are common during pediatric BVM use.¹⁴

Most pediatric resuscitation bags come equipped with a pop-off valve, a pressure-relief mechanism designed to vent excess pressure and prevent barotrauma. This sounds like a safety feature, and in routine ventilation it is. But in emergencies, when airway resistance is high or lung compliance is poor (as in bronchospasm, near-drowning, or severe pneumonia), the pop-off valve can vent the very pressure needed to ventilate the child, leading to insufficient oxygenation. Emergency airway experts recommend deactivating or bypassing the pop-off valve during resuscitation, though that advice has not been widely disseminated outside specialist circles.¹⁵

Gastric insufflation, where air goes into the stomach instead of the lungs, is another pediatric concern. A study comparing two inspiratory pressure levels in children found that higher pressures (16 cmH2O vs. 12 cmH2O) during face-mask ventilation led to significantly more gastric air, as measured by ultrasound of the stomach.¹⁶ Gastric distention is not just uncomfortable. It pushes the diaphragm upward, reduces lung capacity, and increases the risk of vomiting and aspiration. Keeping pressures as low as possible while still achieving chest rise is the standard approach.

BVM Versus Advanced Airways in Cardiac Arrest

For years there has been debate about whether patients in cardiac arrest do better with BVM ventilation alone or with an advanced airway device like an endotracheal tube or supraglottic airway. The Pragmatic Airway Resuscitation Trial, a large study of out-of-hospital cardiac arrest, provided striking data. Patients managed with BVM alone had survival-to-discharge odds more than four times higher than those receiving an advanced airway, and neurologically intact survival odds were about seven times higher.¹⁷

These numbers need careful interpretation. The study was not a clean head-to-head comparison. Patients who received advanced airways were generally sicker or harder to ventilate, which is often why the advanced airway was placed in the first place. The “BVM-rescue” subgroup, patients who started on BVM and then required an advanced airway, had more modest advantages. Still, the data reinforce that BVM ventilation done well is not a lesser intervention. It is a fully adequate ventilation strategy for many cardiac arrest patients, and rushing to intubate during CPR carries its own risks, including prolonged pauses in chest compressions. Aspiration rates, for what it is worth, were similar between BVM and advanced airway groups in that trial.¹⁸

Monitoring BVM Ventilation with Capnography

One of the biggest problems with BVM ventilation is that you often have no idea how well it is actually working. The bag squeezes, you hope air is getting in, but leak around the mask is invisible and silent. Capnography, which measures carbon dioxide in exhaled breath, offers a real-time window into ventilation effectiveness. If CO2 appears on the waveform, air is reaching the lungs and coming back out. If the waveform is flat, something is wrong: a bad seal, an obstructed airway, or no pulmonary blood flow.

A systematic review found that capnography during mask ventilation is feasible and shows potential to guide rescuers during cardiac arrest. In neonates, the technique helped detect changes in heart rate sometimes more than 10 seconds before those changes were visible on a pulse monitor, and it helped maintain airway patency and lung aeration.¹⁹ A study using a portable capnography device during BVM ventilation found that the readings tracked closely with venous blood gas measurements, with differences averaging only about 1.4 to 1.6 mmHg.²⁰ The technology is available and accurate. The barrier is that many prehospital and ward-based teams simply do not think to attach a capnography adapter to a BVM circuit, even when the equipment is within arm’s reach.

Operator Fatigue and Automated Alternatives

Squeezing a bag every five to six seconds does not sound physically demanding, but over the course of a prolonged resuscitation it wears people out. A simulation study using a novel automatic BVM device found that fatigue scores among manual ventilators climbed steadily over time, rising from about 1.8 to 5.1 on a ten-point visual fatigue scale during the test period.²¹ Fatigue does not just make the operator uncomfortable. It degrades performance. Tired hands squeeze less consistently, and mask seals slip.

The same study showed that the automated device delivered far more consistent tidal volumes and pressures than manual squeezing. The coefficient of variation for tidal volume was about 2% with the machine, compared with 14% to 26% with human operators.²² Automated BVM devices are still relatively new and not widely deployed, but the consistency advantage is hard to argue with. In a resource-constrained setting where a single provider is managing multiple tasks, having a mechanical device handle the squeezing while the provider focuses on the mask seal and overall patient management could be a meaningful improvement.

An ergonomically redesigned face mask has also been studied as a way to reduce the physical burden. Novice users in a simulation study achieved better mask seals and reported less fatigue with the redesigned mask compared with a standard round mask, suggesting that better hand positioning accounts for at least some of the performance improvement.²³

Real-Time Feedback Devices and Training

Knowing how to ventilate in theory and doing it well in practice are different things. Even trained paramedics struggle to meet guideline targets for rate and volume. A study measuring ventilation compliance found that only about 1% of ventilations by experienced paramedics met European Resuscitation Council guidelines. When a visual feedback device was added, that number rose, but only to about 3%.²⁴ Those numbers are sobering. They suggest that even with technological help, BVM ventilation accuracy remains poor, and that the device itself has inherent limitations in how precisely a human can control it.

The picture is more encouraging in neonatal ventilation training. A study of birth attendants in a simulation environment found that real-time digital feedback roughly doubled the speed at which they achieved effective ventilation (about 14 seconds versus 28 seconds) and increased the duration of sustained effective ventilation from about 48 seconds to 72 seconds over a two-minute period. Feedback also dramatically improved accuracy in assessing airway integrity, with about 61% of feedback users correctly identifying all three airway conditions by two minutes, compared with about 25% without feedback.²⁵ The difference between the paramedic and neonatal studies likely reflects the different tasks involved. Neonatal ventilation has tighter parameters and more opportunity for immediate correction, while adult ventilation during CPR is chaotic and the feedback may simply get lost in the noise of a full resuscitation.

Infection Control During BVM Ventilation

Every squeeze of a BVM can disperse exhaled air from the patient into the surrounding environment. This became a front-of-mind concern during respiratory disease outbreaks, but it applies anytime a patient has a transmissible airway infection. A study measuring exhaled air dispersion during bag-mask ventilation found that the extent of air leak varied both by device brand and by operator experience. Nurses using one brand of silicone resuscitator had the largest average dispersion distance, roughly 267 mm. Switching to a different brand reduced dispersion significantly, and adding a breathing filter between the mask and the valve reduced leak for most provider groups.²⁶

The practical takeaway is that a viral filter, a small in-line attachment that costs very little, meaningfully reduces aerosolized particle spread during BVM ventilation. In settings where airborne infection is a concern, it should be considered standard. The interaction between operator experience and dispersion distance is also worth noting: a tighter mask seal means less sideways leak. The two-person technique, beyond its ventilation advantages, likely reduces environmental contamination as well, though that has not been directly measured in controlled studies.

BVM Ventilation in Tactical and Austere Environments

Outside the hospital, BVM ventilation takes on a different character. In combat settings, field medicine, or disaster response, the device may be the only ventilation tool available. Updated tactical combat casualty care guidelines now recommend a 1,000 mL resuscitator bag for casualties with impaired ventilation and oxygen saturation below 90%, paired with a nasopharyngeal airway.²⁷ The 1,000 mL size is a deliberate choice: smaller than the standard adult 1,600 mL bag, it reduces the risk of overventilation by limiting the maximum volume a single squeeze can deliver. In a high-stress, low-light, one-provider scenario, that built-in safety margin matters. The self-inflating design means no electricity, no compressed-gas cylinder (beyond supplemental oxygen if available), and no moving parts to fail. A BVM stashed in a med bag will work after being frozen, soaked, dropped, or ignored for years, which is why it remains a cornerstone device for any setting where technology cannot be guaranteed.