Maximum minute ventilation test for the ProSeal™ laryngeal mask airway

One of the distinguishing features of the ProSeal(TM) laryngeal mask airway (PLMA) is that it can cause upper airway obstruction, even when it is correctly inserted behind the cricoid cartilage. We used a hyperventilation test, the maximum minute ventilation test (MMV test), to aid in the diagnosis of upper airway obstruction after PLMA insertion. The patient was briefly hyperventilated for 15 s yielding a MMV value equal to 4 X (breaths/15 s) X (exhaled tidal volume). MMV values were collected in 317 adult women and men over 6 mo. Critical MMV values were obtained in 17 of 317 patients, 15 of 317 (4.7%) of which were due to insertion of the PLMA. The PLMA was removed in seven of 317 (2.2%) patients. The most common cause of upper airway obstruction due to the PLMA was laryngeal obstruction. This refers to compression of supraglottic and glottic structures with resulting narrowing and compromise of the airway. A second, much less common, form of airway obstruction was bilateral cuff infolding with or without downfolding of the epiglottis. Finally, we discuss the margin of safety for minute ventilation, defined as the excess of the MMV over and above basal minute ventilation requirements for the patient. With critical MMV, the margin of safety is drastically reduced or nonexistent.