Critical Incidents with Nonrebreathing Valves

Abstract

Nonrebreathing valves have become widely used in conjunction with self-inflating bags and portable ventilators. The ease of use of these devices compared with Mapleson systems and more complex ventilators has led to their use by a wide range of medical, nursing and paramedical staff. There may be an erroneous tendency to regard these systems as foolproof. Four different critical events arising from IPPV with three different models of nonrebreathing valves are described. Casel A 67-year-old male who had remained unconscious since a cerebrovascular accident two weeks before, was discovered in cardiorespiratory arrest. Cardiopulmonary resuscitation was commenced. Ventilation was with an Ambu Mk I resuscitation bag with Ruben nonrebreathing valve, initially by mask, then endotracheal tube. His pupils remained fixed and dilated despite CPR. ECG showed slow idioventricular rhythm refractory to adrenaline. At this point, additional staff arrived and reassessment revealed inadequate ventilation. Investigations disclosed that the Ambu resuscitator was misassembled. The bag was attached to the patient connection and vice versa. Each delivered breath thereby passed out the expiratory port (Figure I). The system was immediately reassembled correctly, but the patient's heart rhythm and pupils remained unchanged and resuscitation was later discontinued.

From Mouth-to-Mouth to Bag-Valve-Mask Ventilation: Evolution and Characteristics of Actual Devices—A Review of the Literature

“…These valves are composed of an inspiratory and an expiratory port and permit either spontaneous or controlled respiration. Patient valves are used for positive pressure ventilation with a BVM or a mechanical ventilator [12]. In most cases, in order to minimize dead space, the valves are situated close to the patient's airway [13, 14].…”

“…Critical incidents have been documented and a large variety of causes have been identified. Several studies showed some accidents due to faulty one-way valves in BVM and mechanical ventilation [12, 20]. A recent study described a pulmonary barotrauma case due to the “locking” of the Ambu valve in the inspiratory position [20].…”

“…Another case study reported a faulty inspiratory diaphragm of the Laerdal NRV connected to a Dräger Oxylog ventilator which induced 79% SaO 2 (down from 97%) in a patient. Indeed, they revealed that the “duckbill” valve was not moving totally into the inspiratory position at lower inspiratory flow rates and this caused major leaks and, thereby, much of the insufflated volume bypassed the patient and led to desaturation [12]. …”

“…Many BVM misassembly problems have also been reported in the literature inducing inadequate tidal volumes, barotrauma, and potentially dangerous issues [12, 16, 21, 22]. Ho et al described two exhalation obstruction cases due to the Laerdal valve misassembly, when two “fish-mouth” lips or “duckbill” valves were inserted instead of one [22].…”

“…This was due to the “duckbill” valve missing in the patient's valve assembly [21]. Munford and Wishaw described, after an inadequate ventilation during a resuscitation attempt, another case of misassembly with an NRV used mainly in anesthesia (Ruben valve) [12]. Indeed, the Ambu bag was connected to the patient's port of a Ruben valve and not to the bag inlet, and thus each delivered insufflation passed out of the expiratory port [12].…”