***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: Background Rhodiola crenulata ( R. crenulata ) is widely used to prevent acute mountain sickness in the Himalayan areas and in Tibet , but no scientific studies have previously examined its effectiveness . We conducted a r and omized , double-blind , placebo-controlled crossover study to investigate its efficacy in acute mountain sickness prevention . Methods Healthy adult volunteers were r and omized to 2 treatment sequences , receiving either 800 mg R. crenulata extract or placebo daily for 7 days before ascent and 2 days during mountaineering , before crossing over to the alternate treatment after a 3-month wash-out period . Participants ascended rapidly from 250 m to 3421 m on two separate occasions : December 2010 and April 2011 . The primary outcome measure was the incidence of acute mountain sickness , as defined by a Lake Louise score ≥ 3 , with headache and at least one of the symptoms of nausea or vomiting , fatigue , dizziness , or difficulty sleeping . Results One hundred and two participants completed the trial . There were no demographic differences between individuals taking Rhodiola-placebo and those taking placebo-Rhodiola .  No significant differences in the incidence of acute mountain sickness were found between R. crenulata extract and placebo groups ( all 60.8 % ; adjusted odds ratio ( AOR ) = 1.02 , 95 % confidence interval ( CI ) = 0.69–1.52 ) . The incidence of severe acute mountain sickness in Rhodiola extract vs. placebo groups was 35.3 % vs. 29.4 % ( AOR = 1.42 , 95 % CI = 0.90–2.25 ) . Conclusions R. crenulata extract was not effective in reducing the incidence or severity of acute mountain sickness as compared to placebo . Trial registration Clinical Trials.govNCT01536288 The mechanism of high altitude headache ( HAH ) remains unknown . The aim of this study was to determine experimentally whether optic nerve sheath diameter ( ONSD ) , as an indicator of intracranial pressure , is related to HAH . Following sea level measurements at 3 and 12 hours ( SL ) , 23 subjects were passively transported to high altitude ( 3777 m , HA ) via cable car .  HAH , ONSD , arterial oxygen saturation ( Spo(2 ) ) , and fluid balance were determined at 3 , 12 , 24 , and 36 hours . After 12 hours exposure to HA , subjects were classified by visual analogue scale ( VAS ) as either HAH positive ( HAH+ ) or HAH negative ( HAH- ) . Acetazolamide ( 250 mg ) or placebo was then r and omly prescribed at 15 , 20 , and 28 hours . Outcome means were compared via analysis of variance , and relationships between variables were analyzed by longitudinal regression . Acetazolamide had no statistically significant effect on HAH ( p=0.63 ) or ONSD ( p=0.98 ) , but produced a negative fluid balance ( p<0.01 ) ( and also increased Spo(2 ) in exploratory analyses ) . Spo(2 ) was lower in HAH+ than HAH- [ 85 (3)% versus 88 (2)% , p=0.03 ) . Nevertheless , ONSD increased similarly in HAH+ and HAH- ( interaction p=0.90 ) . ONSD also remained significantly elevated above SL values for the entire HA period [ SL , 5.2 ( 0.5 ) versus HA , 5.6 ( 0.5 ) mm , p<0.01 ] , despite headache resolving with acclimatization [ VAS : SL , 1/100 ( 3 ) mm versus HA 3 h , 9/100 ( 13 ) ; 12 h , 10/100 ( 14 ) ; 24 h , 8/100 ( 12 ) ; 36 h , 1/100 ( 4 ) mm , p<0.01 ] . Furthermore , HAH was significantly correlated with Spo(2 ) ( β=-1.39 , p<0.01 ) but not with ONSD ( β=0.59 , p=0.57 ) . These data do not support that intracranial pressure is associated with the development or amelioration of mild HAH . Clinical trial registration NCT01288781 Background The aim of this study was to assess the role of intravenous iron supplementation in the prevention of AMS . Material / Methods This was a r and omized , double-blinded , placebo-controlled study . Forty-one ( n=41 ) healthy Chinese low-altitude inhabitants living in Beijing , China ( altitude of about 50 meters ) were r and omly assigned into  intravenous iron supplementation ( ISS group ; n=21 ) and placebo ( CON group ; n=20 ) groups . Participants in the ISS group received iron sucrose supplement ( 200 mg ) before flying to Lhasa , China ( altitude of 4300 meters ) . Acute mountain sickness ( AMS ) severity was assessed with the Lake Louise scoring ( LLS ) system within 5 days after l and ing on the plateau ( at high altitude ) . Routine check-ups , clinical biochemistry , and blood tests were performed before departure and 24 h after arrival . Results A total of 38 participants completed the study ( ISS group : n=19 ; CON group : n=19 ) . The rate of subjects with AMS ( LLS>3 ) was lower in the ISS group compared with the CON group , but no significant differences were obtained ( P>0.05 ) . There were no differences in patients ’ baseline characteristics . The physiological indices were similar in both groups except for serum iron concentrations ( 19.44±10.02 vs. 85.10±26.78 μmol/L ) and transferrin saturation rates ( 28.20±12.14 vs. 68.34±33.12 % ) , which were significantly higher in the ISS group ( P<0.05 ) . Finally , heart rate was identified as a contributing factor of LLS . Conclusions These preliminary findings suggest that intravenous iron supplementation has no significant protective effect on AMS in healthy Chinese low-altitude inhabitants A double-blind r and omized study of 45 climbers on Mt. Rainier was conducted to test the effectiveness of antacids in preventing  acute mountain sickness .  All 45 climbed to 3353 m , and 31 continued to the summit . Ten climbers listed  acute mountain sickness as the reason for not attaining the summit . Of symptoms monitored throughout the climb , neither headache , nausea , dizziness , pounding heart , nor shortness of breath differed in severity between antacid-treated and placebo-treated groups . In both groups vital capacity decreased significantly with ascent ( p less than 0.05 ) , while peak flow ( p less than 0.005 ) and minute ventilation ( p less than 0.001 ) increased significantly . The 7 climbers with the most severe AMS symptom scores above 4000 m had significantly lower peak flow at sea level prior to ascent compared with the other 25 climbers who completed sea level tests ( p less than 0.005 ) . The results of this study fail to document efficacy for antacid use for the prevention of acute mountain sickness Acute mountain sickness ( AMS ) is a common and disabling condition that occurs in healthy individuals ascending to high altitude . Based on the ability of iron to influence cellular oxygen sensing pathways , we hypothesized that iron supplementation would protect against AMS . To examine this hypothesis , 24 healthy sea-level residents were r and omized to receive either intravenous iron(III)-hydroxide sucrose ( 200 mg ) or saline placebo , before ascending rapidly to Cerro de Pasco , Peru ( 4340 m ) . The Lake Louise scoring system was used to assess incidence and severity of AMS at sea level and on the first full day at altitude . No significant difference in absolute AMS score was detected between the two groups either at baseline or at high altitude . However , the mean increase in AMS score was 65 % smaller in the iron group than in the saline group ( p<0.05 ) , and the change in AMS score correlated negatively with the change in ferritin ( R=-0.43 ; p<0.05 ) . Hematocrit and arterial oxygen saturation were unaffected by iron . In conclusion , this preliminary r and omized , double-blinded , placebo-controlled trial suggests that intravenous iron supplementation may protect against the symptoms of AMS in healthy volunteers OBJECTIVE To investigate the therapeutic effect of low-concentration of nitroic oxide ( NO ) inhalation in high-altitude pulmonary edema . METHOD Sixty-five male patients with high-altitude pulmonary edema were r and omized into three groups . Patients in the conventional therapy group received oxygen , intravenous furosemide , aminophylline and dexamethasone ; patients in the nifedipine group received oral nifedipine ( 10 mg , tid ) in addition to conventional therapy ; and patients in the NO group received NO ( 10 ppm ) inhalation for 30 min , in addition to oral nifedipine . The time for which pulmonary rales on auscultation and shadows on chest radiograph lasted , and the course of disease , were compared . RESULT In the NO group , pulmonary rales disappeared in 0.4 + /- 0.3 d , shadows on chest radiograph disappeared in 0.6 + /- 0.2 d , and the course of disease was 1.8 + /- 0.7 d , all of which were significantly different from those of the nifedipine group ( 2.4 + /- 1.4 d , 4.1 + /- 1.7 d , 6.8 + /- 1.8 d , respectively ) and the conventional therapy group ( 3.7 + /- 1.2 d , 5.5 + /- 1.8 d , 9.6 + /- 3.1 d , respectively ) . CONCLUSION Low-concentration NO inhalation on the basis of conventional and nifedipine therapies was very effective in the treatment of high-altitude pulmonary edema , which deserves further and larger scale investigation “ Live High-Train Low ” ( LHTL ) training can alter oxidative status of athletes . This study compared prooxidant/antioxidant balance responses following two LHTL protocol s of the same duration and at the same living altitude of 2250 m in either normobaric ( NH ) or hypobaric ( HH ) hypoxia .  Twenty-four well-trained triathletes underwent the following two 18-day LHTL protocol s in a cross-over and r and omized manner : Living altitude ( PIO2 = 111.9 ± 0.6 vs. 111.6 ± 0.6 mmHg in NH and HH , respectively ) ; training “ natural ” altitude ( ~1000–1100 m ) and training loads were precisely matched between both LHTL protocol s. Plasma levels of oxidative stress [ advanced oxidation protein products ( AOPP ) and nitrotyrosine ] and antioxidant markers [ ferric-reducing antioxidant power ( FRAP ) , superoxide dismutase ( SOD ) and catalase ] , NO metabolism end-products ( NOx ) and uric acid ( UA ) were determined before ( Pre ) and after ( Post ) the LHTL . Cumulative hypoxic exposure was lower during the NH ( 229 ± 6 hrs . ) compared to the HH ( 310 ± 4 hrs . ; P<0.01 ) protocol . Following the LHTL , the concentration of AOPP decreased ( -27 % ; P<0.01 ) and nitrotyrosine increased ( + 67 % ; P<0.05 ) in HH only . FRAP was decreased ( -27 % ; P<0.05 ) after the NH while was SOD and UA were only increased following the HH ( SOD : + 54 % ; P<0.01 and UA : + 15 % ; P<0.01 ) . Catalase activity was increased in the NH only ( + 20 % ; P<0.05 ) . These data suggest that 18-days of LHTL performed in either NH or HH differentially affect oxidative status of athletes . Higher oxidative stress levels following the HH LHTL might be explained by the higher overall hypoxic dose and different physiological responses between the NH and HH OBJECTIVE Recent trials have demonstrated the usefulness of ibuprofen in the prevention of  acute mountain sickness ( AMS )  , yet the proposed anti-inflammatory mechanism remains unconfirmed . Acetaminophen and ibuprofen were tested for AMS prevention . We hypothesized that a greater clinical effect would be seen from ibuprofen due to its anti-inflammatory effects compared with acetaminophen 's mechanism of possible symptom reduction by predominantly mediating nociception in the brain . METHODS A double-blind , r and omized trial was conducted testing acetaminophen vs ibuprofen for the prevention of AMS .  A total of 332 non-Nepali participants were recruited at Pheriche ( 4371 m ) and Dingboche ( 4410 m ) on the Everest Base Camp trek . The participants were r and omized to either acetaminophen 1000 mg or ibuprofen 600 mg 3 times a day until they reached Lobuche ( 4940 m ) , where they were reass 
    Output:
    
We found scarcity of evidence about the risk of adverse events for these interventions .
The assessment of non-pharmacological and miscellaneous interventions suggests that there is heterogeneous and even contradictory evidence related to the effectiveness of these prophylactic strategies .