although it is difficult to define a high altitude , it is generally accepted as being over 
 3,000  m above sea level where clinical , physiological , anatomical , and biochemical changes 
 can be substantial1 . at high altitude , the 
 human body experiences various physiological responses , such as an increase in breathing 
 capacity , an increase in cardiac output during submaximal exercises , and an increase in 
 maximum aerobic power2 .
in addition , it is 
 well known that decreases in atmospheric pressure at high altitude result in pulmonary 
 function efficiently carrying oxygen due to a decrease in the partial pressure of oxygen in 
 alveolar and arterial blood3 . these 
 characteristics of high altitude can be utilized to strengthen physiological function in 
 relation to pulmonary function4 . to 
 breathe ,
oxygen is inhaled and transferred to the bloodstream and carbon dioxide is expelled 
 by exhalation after the oxygen has been used by the body .
although korea has many mountains , the number of 
 mountains exceeding 1,500  m is relatively few so hardly any koreans live at high altitude . 
 due to this environment in korea
, many athletes spend much money to participate in 
 high - altitude training overseas . despite equivocal findings about the benefits at 
 high - altitude training
, current theory dictates that the best approach is to spend several 
 weeks living at 2,500  m and train near sea level5 . for these reasons ,
various methods have recently been attempted to 
 gain the advantages of high altitude while overcoming its disadvantages .
for example , a 
 training program called living high - training low ( lhtl ) uses low - oxygen tents , intermittent 
 exposure to low oxygen , and low - oxygen sleep to gain the advantages of high - altitude 
 training6 .
in addition , recent studies 
 have reported that improvement in pulmonary function can be achieved by living alternately 
 at 850  m above sea level , and at low altitude .
daily living at high altitude can improve the 
 pulmonary function while alternate daily living between high - altitude and low - altitude 
 places can elicit similar effects7 . 

according to roh s study7 , which argues 
 that pulmonary function can be improved by alternate high and low - altitude living , it is 
 appropriate to find a method for strengthening pulmonary function using the environment at 
 high - altitude location .
if daily living at high altitude could improve the pulmonary 
 function , the high costs of training overseas could be reduced , and a new method for 
 improving the skills of athletes whose pulmonary function is important to their athletic 
 performance could be established . in addition ,
not only athletes but also the public would 
 benefit from advancements in methods for improving pulmonary function or respiratory - related 
 difficulties through environmental conditions . accordingly , the present study conducted a comparison of respiratory function and oxygen 
 saturation levels between female students living at high altitude and low altitudes .
the present study investigated the differences in pulmonary function of university students 
 living at high and low altitudes . to achieve this objective ,
the pulmonary function of 
 female university students attending k university , located approximately 850  m above sea 
 level , and y university , located at low altitude , were determined . the study s objective and 
 procedure
the ethical committee of kangwon national university hospital s institutional 
 review board approved the study .
students of k university , which is located 850  m above sea level , take 
 classes for approximately 20 hours every week for 15 weeks in a single semester , commuting 
 to and from a dormitory located at 200  m above sea level . during school holidays ,
they 
 return to their homes located in metropolitan cities , which are at low altitudes .
thus , k 
 university students experience daily living at both high and low altitudes . on the other 
 hand , y university
y university and 
 its dormitory are both located at a low altitude . in this study , students of k university 
 are henceforth referred to as high altitude living students while students of y university 
 are referred to as low - altitude living students .
the oxygen saturation levels , hr , and 
 pulmonary function of the female students of k and y universities were measured at a 
 dormitory located at a low altitude at the same time between 5 pm and 6 pm . the experiment 
 was conducted on october 225 , 2013 . in order to eliminate measurement errors between the 
 two universities , we had two measurers from both universities to ensure the same measurement 
 method was used .
after training , three measurers performed the test measurements and the 
 intra - class correlation coefficient of inter - tester reliability was found to be 0.93 .
the study subjects were chosen based on a history of no respiratory - related diseases , 
 autonomic nervous system disability or symptoms , as well as no smoking history .
in addition , 
 for the two months prior to the measurements , they did not exercise for more than 20 minutes 
 a day , which can affect cardiovascular function . the subjects attending k university 
 included 25 first - year students ( average age : 18.920.57  years , average height : 
 163.044.25  cm ) , 25 second - year students ( average age : 19.960.54  years , average height : 
 161.525.45  cm ) , 25 third - year students ( average age : 21.040.35  years , average height : 
 159.844.40  cm ) , and 25 fourth - year students ( average age : 22.120.67  years , average height : 
 160.804.17  cm ) totaling 100 students .
the average age and height of the study subjects from 
 k university were 20.51  years and 161.30  cm .
subjects attending y university included 28 
 first - year students ( average age : 18.140.36  years , average height : 161.865.27  cm ) , 25 
 second - year students ( average age : 19.120.44  years , average height : 162.564.27  cm ) , 25 
 third - year students ( average age : 20.040.46  years , average height : 159.885.04  cm ) , and 26 
 fourth - year students ( average age : 21.120.59  years , average height : 162.005.08  cm ) a total 
 of 104 students .
the average age and height of the study subjects from y university were 
 20.66  years and 161.59  cm .
oxygen saturation and hr ( beats per minute : bpm ) levels were measured using an instrument 
 that calculates heart rate and arterial blood oxygen saturation levels ( pulse oximeter , 
 mp110p , mek - ics co. , korea ) .
the pulse oximeter was attached to the subject s middle fingers 
 and the levels were measured in a stable state 68 times within five minutes .
pulse oximetry is a non - invasive method that 
 uses an instrument to monitor oxygen saturation levels easily and quickly , and displays the 
 measured levels as spo2 . in this study ,
forced vital capacity ( fvc ) , forced 
 expiration volume of 1 second ( fev1 ) , peak forced expiratory flow ( pef ) , and forced vital 
 capacity of 1 second were measured using cardiopulmonary measuring instruments ( microplus 
 spirometer , carefusion co. , uk ) .
when subjects arrived at 
 the measurement location , they were instructed to rest for more than five minutes to ensure 
 that their condition was normal .
then , oxygen saturation and hr levels were measured using 
 the right index finger .
demonstrations and explanations about the required posture were 
 provided before measuring cardiopulmonary function , which was done three times .
vital capacity was measured using the method 
 recommended for chronic obstructive pulmonary disease patients by referring to the standard 
 guidelines8 for the implementation and 
 reading of pulmonary function tests published by the american thoracic society and the 
 european respiratory society .
when pulmonary function was measured , the subjects were 
 instructed to look forward , while standing in an upright position .
the subjects were 
 instructed to maximally inhale and then exhale quickly and strongly for the longest time 
 possible , while firmly holding the nose and properly biting the mouthpiece . to obtain better 
 measurement results ,
the subjects were encouraged by a researcher saying , more , more , more , 
 hoo .
the subject was instructed to rest for approximately two minutes after each measurement 
 so as not to record rebound measurements . when measured levels could not be properly 
 obtained because the subject coughed or otherwise , the subject was instructed to rest , after 
 which the measurement was repeated .
the data were analyzed using spss 12.0 for windows and the paired t - test to determine 
 respiratory function and oxygen saturation levels according to grade .
this study was conducted to compare the cardiopulmonary functions of female university 
 students living at high altitude and low altitudes .
oxygen saturation and cardiopulmonary 
 function levels of the students attending the college located at low altitude and those 
 attending the college at high altitude were determined .
hr , pef , and fev1/fvc levels of the 
 students living at high altitude were lower while their oxygen saturation , fev1 , and fvc 
 levels were higher than the levels of the students living at low altitude .
there were 
 significant differences between the two groups of students in all the measured item 
 ( p<0.01 ) ( table 1table 1.comparison of pulmonary functions of female university students at low and high 
 altitudehr * * ( bpm)oxygen saturation * * ( % ) fev * * ( ml)fvc * * ( ml)pef * * ( ml)fev1/fv**high altitude77.7310.3498.261.022.650.382.870.46318.1071.780.930.77low altitude82.159.0997.681.502.390.462.450.49363.2074.630.980.04**p<0.01 , hr : heart rate , fev1 : forced expiratory volume of one sec , fvc : 
 expiratory flow rate obtained by fastest expiration after maximal inhalation , pef : 
 peak expiratory flow , fev1/fvc : the ratio of forced expiration volume for 1 sec to 
 forced vital capacity . ) .
that is , the hr of students living at high altitude was slower while their 
 oxygen saturation , lung capacity , and inspiratory capacity levels were higher than the 
 levels of students living at low altitude . * * p<0.01 , hr : heart rate , fev1 : forced expiratory volume of one sec , fvc : 
 expiratory flow rate obtained by fastest expiration after maximal inhalation , pef : 
 peak expiratory flow , fev1/fvc : the ratio of forced expiration volume for 1 sec to 
 forced vital capacity .
differences in oxygen saturation , bpm , and respiratory function levels of students living 
 at low and high altitudes were determined according to grade .
first - year students showed 
 statistically significant differences in all items , except for bpm and fev , between students 
 living at low and high altitudes ( p<0.01 ) .
second - year students showed statistically 
 significant differences in all items , except for oxygen saturation levels , between students 
 living at low and high altitudes ( p<0.05 , p<0.01 ) .
fourth - year students showed a significant difference 
 only in fvc ( p<0.05 ) .
hr and pef levels of students living at high altitude were lower 
 while their oxygen saturation , fev1 , and fvc levels were higher than the levels of students 
 living in a low - altitude place .
however , first- and second - year students living at high 
 altitude had lower fev1/fvc levels than students living at low altitude .
therefore , it can 
 be said that living daily at high altitude affects respiratory function ( table 2table 2.comparison of pulmonary function of female university students by grade 
 levelhr(bpm)oxygensaturation ( % ) fev1(ml)fvc(ml)pef(ml)fev1/fvc(%)freshmenh78.0410.2398.440.77**2.620.462.960.47**279.8482.26**0.880.02l82.768.8897.321.952.380.462.410.47374.2472.290.990.02sophomoresh76.8411.85 * 98.320.802.690.40**2.980.53**307.0462.84**0.910.08**l83.649.5697.961.022.280.322.310.32371.8176.020.990.02juniorsh75.927.6398.321.182.570.352.660.39326.2762.730.970.54l78.969.9797.601.662.450.352.540.3432571.770.970.06seniorsh80.1211.3197.961.242.700.302.860.38**356.1557.560.950.06l83.327.5097.881.202.460.632.530.71378.7265.170.970.05*p < 0.05 , * * p < 0.01 , h : high altitude , l : low altitude , hr : heart rate , fev1 : 
 forced expiratory volume of one sec , fvc : expiratory flow rate obtained by fastest 
 expiration after maximal inhalation , pef : peak expiratory flow , fev1/fvc : the ratio of 
 forced expiration volume for 1 sec to forced vital capacity . ) .
* p < 0.05 , * * p < 0.01 , h : high altitude , l : low altitude , hr : heart rate , fev1 : 
 forced expiratory volume of one sec , fvc : expiratory flow rate obtained by fastest 
 expiration after maximal inhalation , pef : peak expiratory flow , fev1/fvc : the ratio of 
 forced expiration volume for 1 sec to forced vital capacity .
this study aimed to determine whether living at high altitude place can change pulmonary 
 function by comparing the pulmonary functions of female university students living at high 
 and low altitudes .
it is generally accepted that hrs at high altitude are higher while 
 oxygen saturation levels are lower than at low altitude .
in contrast , maximum oxygen uptake 
 and endurance levels are lower at high altitude than at low altitude9 . in this study , students living at high altitude had lower 
 hr and higher oxygen saturation levels than students living at low altitude .
the reason for 
 this is that the students living at high altitude had adapted to the high - altitude 
 environment and their hr and oxygen saturation levels were similar to those seen in 
 individuals living in a high - altitude environment .
therefore , their hr levels were lower 
 while their oxygen saturation levels were higher than the levels of students living at low 
 altitude when the measurement was done at low altitude .
changes in the respiratory system at high altitude are related to lung capacity , diffusion 
 capacity , the perfusion and ventilation relationship , and changes in lung ventilation 
 capacity10 . in order to reduce the 
 excessive ventilation of the lungs ,
indigenous people at high altitude have a larger lung 
 capacity and 2128% lower residual capacity than those living at low altitude11 . in this study , students living at high 
 altitude had higher fev1 and fvc and lower pef levels than those of the students living at 
 low altitude a result , which is consistent with previous studies1 , 10 , 11 .
therefore , it can be said that living daily at high 
 altitude affects pulmonary function .
hr and pef levels of students living at high altitude were lower while oxygen saturation , 
 fev1 , and fvc levels were higher than those of students living at low altitude .
first - year 
 students showed statistically significant differences in all items , except for bpm and fev , 
 between living at low and high altitudes and second - year students showed differences in all 
 items , except for oxygen saturation levels .
the main items showing physiological changes at 
 high altitude are cardiac output , hr , and pulmonary artery pressure10 . in particular , the first- and second - year students who 
 lacked the ability to adapt to daily living at high altitude , had lower fev1/fvc levels than 
 those of students living at low altitude .
third - year students living at high altitude showed no significant differences when compared 
 with students living at low altitude , while fourth - year students showed different fvc 
 levels .
these results indicate that the pulmonary function of third- and fourth - year 
 students had adapted to living at high altitude through living there for a long period .
our 
 results also showed that cardiac output increased in those taking a rest while living at low 
 altitude as well as those exercising at an earlier time while living at high altitude . 

however , cardiac output returned to the value seen at sea level once the subjects had 
 adapted to living at high altitude10 . 

this is explained by the fact that people living at low altitude increase pulmonary 
 perfusion and lung capacity in response to the low atmospheric pressure and low oxygen 
 partial pressure when temporarily living at high altitude11 .
also , the amount of ventilation experienced while resting does not 
 recover to the value seen at sea level even if complete adaptation is achieved . when living 
 at high altitude for a certain period of time , the human body acclimatizes by increasing 
 pulmonary perfusion and lung capacity , increasing the oxygen - binding capacity of blood and 
 peripheral tissues , and increasing the amount of red blood cells in order to endure the low 
 atmospheric pressure and low partial pressure of oxygen12
therefore , third- and fourth - year students had increased lung 
 capacity and pulmonary perfusion because of adaptation to daily living at high altitude .
our results suggest that , if an individual is not accustomed to high altitudes of between 
 1,500  m or 3,000  m above sea level , living at high altitude would mainly elicit 
 physiological changes in oxygen saturation and pulmonary function .
however , this study did 
 not identify how long a daily living period at high altitude is needed to influence 
 pulmonary function enough that it can improve the performance of athletes .
in addition , the 
 students living at high altitude did not stay at high altitude all the year round , only for 
 30 weeks of the year .
thus , the time spent at school at high altitude would be much shorter 
 than 30 weeks .
nonetheless , our study results show that there were changes in oxygen 
 saturation and pulmonary function levels , even under such conditions .
therefore , it would be 
 a good idea to search for measures to utilize high - altitude locations to improve the 
 pulmonary function of athletes .
that is , changes in pulmonary function can be obtained 
 through training that alternates between low- and high - altitude locations .
it would be more 
 advantageous to open a training field at high altitude and have athletes stay there for a 
 certain period rather than travel overseas to training facilities at a high altitude 
 locations , in terms of finances and the administration of athletes .
thus , an in - depth study 
 should be conducted of pulmonary function and physiological changes at high altitude .
also , 
 future research of male subjects and individuals of various ages is needed .
 [ purpose ] this study compared the respiratory function and oxygen saturation levels of 
 university students living at high altitude , to present a new approach for improving 
 respiratory function using high altitudes above sea level . [ subjects and methods ] the 
 subjects were 100 female students attending a university located approximately 850  m above 
 sea level and 104 female students attending a university located at low altitude . 
 oxygen 
 saturation , heart rate ( hr ) , and respiratory function levels were measured . 
 [ results ] for 
 the students living at high altitude , hr , pef , and fev1/fvc levels were low . 
 in contrast , 
 their oxygen saturation , fev1 , and fvc levels were higher than the levels found in 
 students living at low altitude . 
 differences in respiratory function were revealed in 
 first- and second - year students living at high and low altitudes . on the other hand , 
 no 
 significant differences in respiratory function were found between third- and fourth - year 
 students . 
 [ conclusion ] university students living at high altitude had a slower hr and 
 higher oxygen saturation levels as well as higher lung and inspiratory capacity levels . 
 
 thus , physiological improvement in oxygen saturation levels and pulmonary function were 
 seen in the individuals living at high altitude . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION