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Patients with marked respiratory failure may need more intensive ventilatory support than NIPPV. This is true for patients with inadequate ventilatory effort and those with depressed mental status who cannot protect their airways. Immediate assistance should be provided for these patients using a bag‐valve‐mask device to either assist spontaneous ventilations or provide full mechanical ventilation. Proper positioning (head and neck tilt, sniffing position), mechanical airway opening (jaw thrust or modified jaw thrust), and placement of a nasal or oral airway can markedly improve airflow. High‐flow oxygen should fill the bag device, preferably with a reservoir bag. Using this device can be difficult for a single clinician, using one hand to seal the mask and the other to squeeze the bag. Whenever possible, a two‐person technique should be used, with one person using both hands and a jaw thrust maneuver to make a firm seal around the mask and open the airway, while the other person squeezes the bag.

EMS clinicians must be cognizant of volume and rate when assisting ventilation. Patients who are severely hypoxic or hypercarbic may initially require hyperventilation, as do those with severe metabolic acidosis, such as from diabetic ketoacidosis or sepsis. However, absent such conditions, unnecessary hyperventilation will have detrimental effects, including decreased cerebral perfusion, venous return, and cardiac output, and metabolic impairment from respiratory alkalosis. Standard adult bags are typically 1,500–1,600 ml, so a full squeeze will provide excessive tidal volume and likely high peak airway pressure, and facilitate inadvertent hyperventilation. One study found that most adults could be ventilated with a pediatric bag, but a small adult size with 1,000 ml is available [10]. Some devices can be equipped with high inspiratory pressure pop‐off valves and positive end‐expiratory pressure (PEEP) valves (Figure 6.3). These adjuncts improve proper ventilation and oxygenation.