***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE To describe the prehospital use of a continuous positive airway pressure ( CPAP ) system for the treatment of acute respiratory failure presumed to be due to cardiogenic pulmonary edema . METHODS Prospect i ve case-series analysis . Paramedics administered CPAP via face mask at 10 cm H2O to patients believed to be in cardiogenic pulmonary edema and in imminent need of endotracheal intubation ( ETI ) . Data from run sheets and hospital records were analyzed for treatment intervals , vital signs , complications , admitting diagnoses , need for ETI , and mortality . RESULTS Nineteen patients received prehospital CPAP therapy .  Mean duration of therapy was 15.5 minutes . Pre- and post-therapy pulse oximetry  was available for 15 patients and demonstrated an increase from a mean of 83.3 % to a mean of 95.4 % . None of the patients were intubated in the field . Two patients who did not tolerate the CPAP mask required ETI upon arrival in the emergency department ( ED ) ; an additional five patients required ETI within 24 hours . There was one death in the series and two additional adverse events ( one aspiration pneumonia , one pneumothorax ) ; none of these were attributable to the use of CPAP . The diagnosis of cardiogenic pulmonary edema was corroborated by the ED or in-hospital physician in 13 patients ( 68 % ) . Paramedics reported no technical difficulties with the CPAP system . CONCLUSION For patients with acute respiratory failure and presumed pulmonary edema , the prehospital use of CPAP is feasible and may avert the need for ETI . Future controlled studies are needed to assess the utility and cost-effectiveness of prehospital CPAP systems The possible benefits of premedication with the antispasmodic hyoscine n-butyl bromide ( hyoscine ) and analgesia with inhaled nitrous oxide/oxygen mixture ( nitrous oxide ) were assessed in a double-blinded , placebo-controlled trial . Consecutive patients at normal risk for cancer undergoing screening flexible sigmoidoscopy were r and omly allocated to receive either ( 1 ) intravenous hyoscine 20 mg plus inhaled oxygen on dem and ( n = 40 ) , ( 2 ) sterile water injection plus inhaled nitrous oxide on dem and ( n = 48 ) , or ( 3 ) sterile water injection plus inhaled oxygen on dem and ( n = 43 ) . One recently trained primary care physician performed all procedures . Duration of the procedure , endoscopic findings , and depth of insertion were recorded . After the examination , screenees rated their degree of pain during the procedure using a visual analogue scale . Depth of insertion did not differ between the three study groups , but the duration of the procedure was significantly less in the hyoscine group ( median , 12.5 minutes ) as compared with placebo ( median , 18 minutes ; p = .0008 ) . Fifty-four percent of screenees chose to use the on-dem and gas . Pain scores were significantly lower in those individuals who inhaled nitrous oxide as compared with placebo ( p = .045 ) . Premedication with antispasmodic shortens total procedure time for flexible sigmoidoscopy by a moderately experienced endoscopist as compared with placebo . In this study , a significant number of screenees experienced discomfort during flexible sigmoidoscopy , which appeared to be reduced by offering nitrous oxide inhalation The analgesic effect of self-administered nitrous oxide 50%/oxygen 50 % ( ' Entonox " analgesic apparatus ) was compared with air given by the same method in a double-blind trial in 81 patients with myocardial infa rct ion .  Self-administered nitrous oxide/oxygen , which was associated with a low frequency of side-effects , proved significantly more effective than air in the early relief of severe cardiac pain , but not in the relief of moderate or slight pain or when administration was continued after ten minutes Background Intermittent self-administered nitrous oxide has long had widespread use as an analgesic in labor , but its efficacy has not been adequately established . Questions about its effect on maternal oxygenation between labor contractions also have been raised . Methods Twenty-six women were recrulted to participate in a r and omized , double-blind , cross-over , placebo-controlled study to assess the effect of intermittent nitrous oxide inhalation on labor pain and maternal hemoglobin oxygen saturation ( SpO2 ) during the first stage of labor . Visual analog scale pain scores for each of five consecutive labor contractions were measured after administration of either nitrous oxide or compressed air . Results Mean visual analog scale pain scores for five contractions were 5.1 , 5.2 , 5.7 , 5.2 , and 5.6 ( nitrous oxide ) and 4.9 , 5.2 , 6.1 , 5.6 , and 5.7 ( compressed air ) . There were no statistically significant differences in pain when nitrous oxide as compared with compressed air was administered . Pain scores did not differ significantly over time as a function of inhaled substance ( F = 0.41 , P = 0.53 ) . The mean lowest SpO2 observed between these contractions after self-administration of nitrous oxide and air were 97 , 97 , 97 , 97 , and 97 % ( nitrous oxide ) and 97 , 96 , 96 , 96 , and 96 % ( compressed air ) . SpO2 was significantly higher after nitrous oxide administration ( F = 8.8 , P = 0.007 ) . Conclusions While intermittent self-administered 50 % nitrous oxide in oxygen does not appear to predispose parturient women to hemoglobin oxygen desaturation , its analgesic effect has yet to be clearly demonstrated OBJECTIVE : Although percutaneous liver biopsy ( PLB ) can be a painful procedure , common practice has not included intravenous sedation or analgesia Patient-administered nitrous oxide/oxygen ( N2O/O2 ) inhalation has demonstrated analgesic efficacy in various procedures associated with mild to moderate pain The aim of this study was to investigate the safety and efficacy of analgesia with N2O/O2 inhalation for PLB METHODS : One hundred consecutive patients undergoing a first PLB ( for chronic hepatitis C : 56 , for alcoholic liver disease : 23 , for miscellaneous reasons : 21 ) Patients were r and omly assigned to self-administrate from a facial mask with a dem and valve , for 5 min before and during biopsy , either a breathing mixture of 50 % N2O/O2 ( N2O group , n = 51 ) , or a breathing oxygen placebo ( P group , n = 49 ) Liver biopsy was performed at bedside after adequate local anesthesia with xylocaine At the end of the procedure , patients were asked to self-evaluate pain experienced using a visual analogue scale ( VAS ) with scoring from 0 to 100 mm . RESULTS : N2O/O2 administration result ed in the absence of pain in a significantly higher number of patients treated than in patients of the P group : 19 versus 2 , respectively ( p = 0.0001 ) . Patients receiving N2O/O2 had significantly lower pain scores than those of the P group : 12 ± 12 versus 28 ± 19 mm ( p < 0.0001 ) . No serious complication was observed . Side effects of N2O/O2 were minor and reversible . The average cost per biopsy was 4 US dollars . CONCLUSIONS : Patient-administered N2O/O2 inhalation provides safe and effective analgesia , at a reasonable cost , for PLB . Its routine use could be useful for the management of patients with chronic liver disease undergoing PLB as it may enhance patients compliance with future biopsies BACKGROUND AND STUDY AIMS Patient-administered nitrous oxide in 50 % oxygen has lately come into use as an alternative to combined opioid and benzodiazepine medication for colonoscopic procedures . A r and omized study was carried out comparing intramuscular pethidine hydrochloride 1 mg/kg with inhalation of Medimix ( a mixture of nitrous oxide in oxygen 50 % ) for relief of pain and anxiety during colonoscopy . PATIENTS AND METHODS Thirty-eight patients ( 19 in the pethidine group and 19 in the nitrous oxide group ) were studied . The following parameters were measured : blood pressure , pulse rate , and arterial oxygen saturation . At the end of the colonoscopy and before the patients left the ward , pain , nausea , and general well-being were evaluated by the patients using a visual analogue scale . The colonoscopy time , investigation conditions and the total length of hospital stay were registered . RESULTS Colonoscopy time and the colonoscopists ' opinions concerning the investigation conditions did not differ between the groups . Pain relief and patient evaluation of the total procedure were also equal between the patient groups . However , there was less nausea among the Medimix patients . Three patients in the pethidine group had oxygen saturations below 92 % . There was no desaturation during and five minutes after colonoscopy in the Medimix group . Patients in the Medimix group left the hospital on average 34 minutes earlier than patients in the pethidine group . CONCLUSIONS We conclude that the use of nitrous oxide ( Medimix ) as an analgesic is as good as pethidine for colonoscopy . Medimix has clear advantages compared to pethidine in terms of reducing nausea and shortening the hospital stay Hypoxaemia may occur after hyperventilation with nitrous oxide during labour . The purpose of this study was to assess whether diffusion hypoxia is a contributory factor . Twenty‐four parturients were r and omly allocated to receive 50 or 70 % nitrous oxide in oxygen . The median nitrous oxide inhalation time per contraction was 58 s and 33 s , respectively . The end‐tidal carbon dioxide and the minute ventilation remained unchanged . The end‐tidal oxygen concentration was lowest at 120s , reaching 15.4 % in both groups . The oxygen saturation did not differ between the groups with a lowest median value of 96 % before the start of nitrous oxide inhalation . Two parturients had episodes ofdesaturation . Both had low end‐tidal oxygen concentrations in association with the desaturation but , as the end‐tidal nitrous oxide concentrations were low , the desaturations could not be attributed to diffusion hypoxia In a r and omized trial nitrous oxide 50 % in oxygen ( Entonox ) or oxygen 100 % was given during chest physiotherapy on 23 occasions to three mechanically ventilated patients with severe head injuries .  Intracranial pressure ( i.c.p . ) increased by 22.7 mm Hg ( SD 10.62 ) during chest physiotherapy with Entonox , compared with 10.5 mm Hg ( SD 10.4 ) with oxygen 100 % ( P greater than 0.02 ) . A further nine mechanically ventilated patients with severe head injuries were given Entonox without chest physiotherapy . There was a mean increase in i.c.p . of 3.8 mm Hg ( SD 2.4 ) ( P less than 0.001 ) when Entonox was given , and a mean decrease of 4.6 mm Hg ( SD 2.8 ) when the nitrous oxide was withdrawn . End-tidal carbon dioxide concentration showed almost no change during nitrous oxide administration ( decrease of 0 - -0.1 % ) . We conclude that nitrous oxide causes an increase in i.c.p . in patients with severe head injuries and exacerbates the increases in i.c.p . occurring during chest physiotherapy Summary A prospect i ve , r and omized study was undertaken to compare the effectiveness of nitrous oxide with intramuscular sedation ( meperidine and promethazine ) in providing analgesia and amnesia during the reduction and treatment of children 's fractures in an outpatient clinic setting . Fifteen patients received a 50:50 mixture of nitrous oxide and oxygen , and 15 received intramuscular injection .  The two groups were similar in regard to gender distribution , age , and fracture types . Pain response was recorded using the Children 's Hospital of Eastern Ontario ( Canada ) Pain Scale ( CHEOPS ) at the time of fracture reduction and 30 min postreduction . At the first follow-up visit a question naire regarding the patient 's memory and subjective experience of the fracture reduction was answered . Data between the two groups were compared using the Mann-Whitney test . The CHEOPS scores , and the memory and subjective experience of the fracture reduction were similar between the two groups . Time in the outpatient department averaged 83 min for the intramuscular group and 30 min for the nitrous oxide group ( p < 0.01 ) . All of the nitrous oxide patients stated they would use nitrous oxide again , whereas only eight of 15 intramuscular patients stated they would try intramuscular sedation again . Nitrous oxide is as effective as intramuscular sedation in providing analgesia and amnesia in the treatment of children 's fractures while having a more rapid onset and a shorter recovery period with greater patient acceptance In this five-period r and omised double-blind crossover study , 12 healthy volunteers inhaled  mixtures of nitrous oxide at concentrations of 0 % ( placebo ) ; 5 % , 10 % ; 20 % and 40 % in oxygen . Each concentration was inhaled for about 1 h , each period being on a separate day . The effects of nitrous oxide were 
    Output:
    
Adverse effects were rare and significant adverse outcomes such as hypotension and oxygen desaturation could not be attributed to nitrous oxide .
Compared with patients receiving conventional analgesia , those receiving 50 % nitrous oxide did not require additional medication any more frequently and had a faster recovery from sedative effects .
The low incidence of significant adverse events from 50 % nitrous oxide suggests that this agent could be used safely by lay responders