The effect of nitrous oxide on laryngeal mask cuff pressure

Abstract

In v i m and in vivo studies A. B. LUMB AND M.W. WRIGLEY SummaryWe have studied the effect of nitrous oxide on the cufpressure o f a laryngeal mask both in vitro and in vivo. In laboratory tests. we showed that nitrous oxide and carbon dioxide diffuse across the cuff wall much more rapidly than nitrogen and oxygen. Diflkring partial pressures of these gases across the cuff wall therefore give rise to changes in volume and pressure within the cuff. We then studied 18 patients undergoing general anaesthesia with nitrous oxide, and found a consistent and linear increase in cufl pressure in all patients. After 30 min. the mean pressure had increased by 30 mmHg, and there was approximately 10% nitrous oxide in the cuff: It is dificult to relate these findings to pressure on pharyngeal structures, but methods of limiting the rise in intracufl pressure are discussed.

Hypoglossal Nerve Palsy After Airway Management for General Anesthesia

“…Lumb and Wrigley demonstrated that LMA cuff pressures can increase by as much as 50% during brief periods of N 2 O anesthesia. 75 Similarly, Trumpelmann and Cook reported on an overdistended LMA cuff after removal in a patient who had received N 2 O during anesthesia. 32 Although the cuff insufflation volume varies considerably by LMA size and type, these unanticipated increases in cuff volume during longer cases can compress the hypoglossal nerve against the hyoid bone and cause HNP symptoms.…”

“…78 Similarly, Ratnaraj et al showed that maintaining ETT cuff pressure < 20 cmH 2 O in patients undergoing cervical spine surgery significantly decreased the incidence of sore throat 24 hours after extubation. 79 Intermittent pressure cuff lowering during long operations or pressure-relief valves can decrease the risk of nerve compression, 29,75,80 and it follows that LMA or ETT cuff deflation during surgical positioning could also prevent iatrogenic injury to the hypoglossal and recurrent laryngeal nerves, respectively. Bohner et al described the first use of a nerve stimulator for the successful identification and continuous monitoring of the hypoglossal nerve during an anatomically challenging carotid endarterectomy under general anesthesia.…”

Unilateral Vocal Cord Paralysis following Insertion of a Supreme Laryngeal Mask in a Patient withSjögren’sSyndrome

“…Measurement of intracuff pressure in any LMA should be done with a standard of care as it reduces postoperative laryngopharyngeal adverse events [2]. Furthermore it is known that nitrous oxide can increase intracuff volume up to 50% by way of diffusion [22]. …”

Unilateral Hypoglossal Nerve Palsy after Use of the Laryngeal Mask Airway Supreme

“…Among the risk factors, only the use of nitrous oxide applied to our case. It is well known that nitrous oxide will diffuse into the LMA cuff and increase the cuff pressure with time during anesthesia [14]. The cuff pressure of LMA Classic and LMA ProSeal has been shown to increase from 60 cmH 2 O to over 100 cmH 2 O following 30 min of nitrous oxide exposure [14].…”

“…It is well known that nitrous oxide will diffuse into the LMA cuff and increase the cuff pressure with time during anesthesia [14]. The cuff pressure of LMA Classic and LMA ProSeal has been shown to increase from 60 cmH 2 O to over 100 cmH 2 O following 30 min of nitrous oxide exposure [14]. However, there are reports that LMAs with PVC cuff are less susceptible to hyperinflation caused by nitrous oxide compared to the ones with silicone cuff [15–17].…”