with the advent of minimally invasive surgical techniques , ambulatory surgeries are on the rise , leading to an increased demand for fast tracking . this necessitates early recovery in the form of clear - headedness , control of protective airway reflexes and satisfactory relief from pain and emesis . as a result , there is a need for the use of short - acting anaesthetic drugs for a better quality of recovery . sevoflurane and desflurane have been in use for ambulatory anaesthesia as they both have properties of an ideal agent . desflurane has lower blood gas solubility than sevoflurane resulting in rapid induction and emergence from anaesthesia . however , desflurane is pungent and can be irritant to the airway leading to coughing , breathholding , laryngospasm and copious secretions . we decided to compare the efficacy of desflurane and sevoflurane for maintenance and recovery of anaesthesia and to evaluate airway responses in spontaneously breathing patients using the proseal laryngeal mask airway ( lma ) during ambulatory surgeries . we hypothesise that desflurane has a faster recovery profile but may cause increased airway events during spontaneous ventilation when compared to sevoflurane . institutional ethics committee approval and written informed consent from the participating patients was obtained for this study . a total of 94 female patients between 18 and 65 years belonging to the american society of anesthesiologists ' physical status i and ii undergoing hysteroscopic gynaecological surgery under general anaesthesia were randomly allocated into two groups using computer - generated codes kept in sealed opaque envelopes . group s patients who received sevoflurane for maintenance of anaesthesia , while group d patients received desflurane for maintenance of anaesthesia . patients who were morbidly obese , with distorted airway anatomy or at risk of gastric aspiration were excluded from the study . after securing an intravenous ( iv ) line , ringer 's lactate infusion was started . non invasive blood pressure , electrocardiogram and pulse oximeter ( spo2 ) were attached , followed by pre - medication with iv midazolam 0.03 mg / kg and fentanyl 1g / kg . after abolition of the eye lash reflex and adequate jaw relaxation , an appropriate size proseal lma according to weight of the patient was inserted with the digital technique . if the lma could not be satisfactorily placed at the first attempt , additional bolus doses of propofol ( 2040 mg ) after confirming the placement of proseal lma , anaesthesia was maintained with 50% oxygen and 50% nitrous oxide and either sevoflurane or desflurane ( according to random allocation ) on a closed circuit ( north american drager primus , draeger medical gmbh , germany ) . total fresh gas flow during first 6 min was standardised and kept at 6 l / min with vaporiser dial concentration of 6% for desflurane and 2% for sevoflurane . initially , patients were given intermittent positive pressure ventilation . at the end of 6 min , total fresh gas flow was reduced to 1 l / min , and the dial concentration was reduced to 3% for desflurane and 1% for sevoflurane , and patients were allowed to breathe spontaneously . all patients received ondansetron 0.1 mg / kg iv . at the end of the procedure , the volatile anaesthetic and nitrous oxide were turned off , and 100% oxygen was given . after confirming nitrous oxide removal from circuit with respiratory gas monitoring , the proseal lma was removed . intraoperative haemodynamic variables , namely , heart rate , systolic blood pressure , diastolic blood pressure , spo2 , respiratory gas monitoring , end - tidal carbon dioxide , respiratory rate , minimum alveolar concentration ( mac ) and end - tidal concentration of volatile agent were monitored every 5 min throughout the surgery . we studied the occurrence of cough , hiccups , breathholding ( > 10 s ) and laryngospasm during maintenance of anaesthesia and in the post - operative period . another qualified anaesthetist unaware of the inhalational agent used , assessed the time taken from switching off of the vaporiser to eye opening , time to obey verbal commands ( tongue protrusion ) , time to sit with support , time to shift out of the recovery room and orientation in time , place and person . coughing was graded as mild for 13 coughs , moderate for 47 coughs and severe for 8 or more cough . breathholding was graded as 1 for 1020 s , 2 for 2030 sand 3 for > 30 s. laryngospasm was graded as 1 for phonation and stridor < 15s , 2 for phonation and stridor > 15s and 3 for duration > 15s requiring iv medication to treat . patients were shifted to the recovery room in propped up position . humidified oxygen was administered through a face mask , and recovery characteristics were recorded every 5 min with the help of modified aldrete scoring system . a score of 8 was considered suitable for discharging the patient from the post - anaesthesia care unit to the ward . sample size was calculated considering typei error with alpha = 0.05 and power of 0.80 . assuming a 35% occurence in airway events with desflurane based on a previous study and 10% in sevoflurane group based on a pilot study we did with sevoflurane , a minimum of 43 patients were required in each group . expecting a few drop outs ( requiring endotracheal intubation and protocol deviation ) , a total of 94 patients were included in the study . armonk , ny . quantitative data were presented with the help of mean and standard deviation . comparison between study groups was done with the help of unpaired t - test or mann  whitney test . ninety - four patients were randomised , out of which 92 patients completed the study . two patients in the desflurane group were excluded because intraoperatively they required intubation due to improper seal of lma [ figure 1 ] . the demographic details of patients such as age , weight , height were comparable in both the groups [ table 1 ] . also average mac value in group s 1.09  0.07 and group d 1.10  0.08 , total duration of surgery ( in min ) in group s 22.13  4.97 and group d 21.89  4.97 were comparable . adverse airway events such as cough , hiccups , breathholding and laryngospasm were found in 6.4% of patients in group s and 13.3% of patients in group d ( p = 0.148 ) . thus , the difference in the incidence of adverse airway events was not significant [ figure 2 ] . comparison of airway responses amongst the study groups the mean time to eye opening ( in min ) was10.75  7.54 in group s , and 4.94  1.74 in groupd ( p < 0.001 ) . both time ( in min ) to obey verbal commands ( 13.13  8.75 in group s and 6.55  1.75 in group d ) and mean time to be oriented in time place and person ( 15.42  8.46 in group s and 6.23  2.4 in group d ) occurred earlier in desflurane group as compared to sevoflurane group ( p < 0.001 ) . the mean time ( in min ) to sit with support was 36.09  12.68 in group s compared to 14.35  3.75 in group d ( p < 0.001 ) [ table 2 ] . the mean total time ( in min ) to recovery was greater with sevoflurane ( 46  12.86 ) compared to desflurane ( 26.44  5.33 ) , p < 0.001 [ table 2 ] . the result of our study shows that there is no difference in the occurrence of airway responses such as coughing , hiccups , breath holding and laryngospasm between desflurane and sevoflurane when used during spontaneous breathing with the proseal lma for short gynaecological surgeries . we also found that desflurane group showed faster recovery in terms of lesser time to opening eyes , response to simple verbal commands such as protruding tongue , orientation in time , place and person and clear - headed recovery with the ability to communicate freely as compared to those belonging to sevoflurane group . when compared to an endotracheal tube , use of the laryngeal mask in general anaesthesia , especially in day care , reduces the incidence of post - operative airway complications . however , studies on airway events with desflurane and lma during spontaneous breathing are limited . sevoflurane is sweet - smelling and non - irritant to the airway and is considered to be most suitable for inhalational induction as well as maintenance of anaesthesia . desflurane has lower blood gas solubility than sevoflurane and is considered to have a faster recovery profile . it is well documented that desflurane can cause airway irritation as it is the most pungent of all volatile anaesthetics . when given in high concentrations above threshold for respiratory irritation ( 11.5 mac in 100% 02 ) however , irritation of the airway may not occur till end - tidal concentration of 5.4% ( upto 1 mac in 100% 02 ) . we found that the adverse airway events occurred in 13.3% in desflurane group and 6.4% in sevoflurane group , but this difference was statistically insignificant . we attribute our findings to our standardised protocol of pre - treatment with fentanyl 1g / kg in both the groups that may have abolished the airway responses . similar findings were seen in a study where exceeding more than 1 mac did not have an increased incidence of breathholding or coughing . administration of fentanyl as pre - medication by them may have decreased the incidence of coughing or breathholding with desflurane . another study had used 50 mcg fentanyl and found similar incidence of airway events in the two groups , despite the reputed greater airway irritability of desflurane . similar findings were seen in a study where on giving fentanyl 1g / kg as pre - medication , there was a decreased incidence of coughing on induction of anaesthesia with desflurane by 80%.a recent study used 1 mac desflurane with fentanyl and observed no difference in the frequency and severity of upper airway events . however , even after administration of fentanyl 1m / kg , there were significantly more adverse responses with desflurane at 12% concentration in 100% oxygen . no significant difference in airway irritation between desflurane and sevoflurane was found when used in smokers , even at higher concentrations of the agents ( > 1mac ) , making desflurane suitable even in patients with reactive airways . due to its pungency , desflurane is not preferred for induction in children , but due to early emergence properties , it may be a preferred agent in neurosurgical patients and ambulatory surgeries . a meta - analysis on recovery with desflurane found three trials with short procedure times . in one trial , they failed to show an advantage of desflurane for early recovery which they attributed to the short duration , while in the other two trials , they were unable to determine the effect of anaesthesia duration on outcome . in our study , the average duration of surgery was 20 min . we found significantly faster awakening of patients who received desflurane than in those with sevoflurane . early recovery in terms of eye opening , response to verbal commands , time to be oriented and sitting with support was all faster with desflurane as compared to sevoflurane . awakening times in our study were similar to the another study where fentanyl was not a part of anaesthesia maintenance showing that addition of fentanyl did not affect the recovery profile . our findings of early recovery with desflurane are similar to various studies where in they found that time to eye opening and obeying commands was earlier in desflurane than sevoflurane . a similar analysis documented the differences in anaesthetic kinetics of 2 and 4h of 1.25 mac of desflurane ( 9.0% ) versus sevoflurane ( 3.0% ) . they concluded that regardless of the duration of anaesthesia , elimination is faster and recovery is quicker for desflurane than for sevoflurane . another study also found similar results that recovery profile ( psychomotor , time to sit in the bed ) is faster with desflurane compared to sevoflurane . we found that the mean total time in recovery room was significantly less in desflurane group compared to sevoflurane group . the above findings of early recovery indicate that desflurane due to its low blood gas solubility ( blood : gas partition coefficient is lowest for desflurane [ 0.45 ] , followed by sevoflurane [ 0.65 ] ) , and rapid elimination with little or no residual metabolites causes a clear - headed recovery , combined with stable haemodynamics , helped to achieve aldrete score > 8 faster than sevoflurane . our findings corroborate with recent study which found similar changes in the immediate and intermediate recovery which was significantly faster after desflurane than sevoflurane anaesthesia , thus contributing to fast tracking and early discharge of patients . due to the higher cost of desflurane however , when used with low flows , desflurane has been found to be less expensive than sevoflurane . desflurane has an overall better quality of early recovery in patients as compared to sevoflurane . the fear of potential adverse airway events may restrict the usage of desflurane , especially with spontaneously breathing patients with lma . however , our study did not show any increase in airway events even at mac>1 which may be attributed to pre - treatment with fentanyl . systematic review could be conducted to evaluate whether the use of fentanyl decreases the incidence of airway events . furthermore , further studies will be required on smokers , patients with reactive airway and obese patients to evaluate the incidence of adverse airway events , especially at higher mac . as the incidence of airway events that we got with desflurane ( 13.3% ) is lower than that assumed for sample size calculations , we have only evaluated female subjects undergoing hysteroscopic gynaecological surgery which limits the generalisation of our results . furthermore , we were unable to eliminate any bias that the administrator might have had to either agents as blinding was impractical .
background and aims : desflurane and sevoflurane have low blood gas solubility co - efficients , allowing a rapid awakening from anaesthesia . however , desfluraneis pungent and may cause airway irritability . we compared desflurane and sevoflurane with respect to recovery and occurrence of adverse airway responses in spontaneously breathing patients while using the proseal laryngeal mask airway ( lma).methods : ninety - four adult patients undergoing hysteroscopic procedures were divided into sevoflurane ( s ) group or desflurane ( d ) group . 
 patients were premedicated with midazolam 0.03 mg / kg and fentanyl 1g / kg . 
 anaesthesia was induced with propofol 2.02.5 mg / kg , followed by insertion of a proseal lma . 
 adverse airway responses such as cough , hiccups , laryngospasm and breathholding were recorded . in the post - operative period : time to awakening , response to verbal commands , orientation , ability to sit with support and the recovery room aldrete score were recorded.results:three patients in group s ( 6.4% ) and six patients ( 13.3% ) in group d had adverse airway events . 
 the mean time to eye opening ( group s-10.75  7.54 min , group d-4.94  1.74 min ) , obeying verbal commands ( group s-13.13  8.75 min , group d-6.55  1.75 min ) , orientation ( group s-15.42  8.46 min , group d-6.23  2.4 min ) and to sit with support ( group s-36.09  12.68 min , group d-14.35  3.75 min ) were found to be lesser with desflurane than with sevoflurane ( p < 0.001 ) . 
 the mean time to recovery was delayed in group s-46.00  12.86 min compared to group d-26.44  5.33 min ( p < 0.001).conclusion : desflurane has faster awakening properties than sevoflurane without an increase in adverse airway events when used during spontaneous ventilation through a proseal lma along with propofol and fentanyl .