Vietnam Joumal of Physiology 13(2), 8/2009 ISSN: 1859-2376
response to prediction of reward associated with place in dopamine 02 receptor knockout mice, Proc Natl Acad Sci USA 99;
8986-8991.
9. Tran A.H., Tamura R., Uwano T. et al.
(2005), Dopamine 01 receptors involved in locomotor activity and accumbens neural responses to prediction of reward associated with place, Proc Natl Acad Sci USA 102: 2117-2122.
10. Yamaguchi H., Aiba A., Nakamura K.
et al. (1996), Dopamine 02 receptor plays a critical' role in cell proliferation and proopiomelanocortin expression in the pituitary. Genes Cells 1; 253-268.
SUMMARY
Tests for evaluating coordinated movement behavior and visual acuity in
experimental animals
In researches on behavioral science using experimental animals, the development of methods for evaluating objectively animal behavior is of necessary, since the behaviors of the experimental animal are the research results that need to be acquired. In the present study, we mentioned a type of simple tests that we developed to evaluate visual acuity (depth visual sensation) and to evaluate the coordinated locomotor activity in mice.
V\/e had used these tests for evaluation in normal animals and also in lesioned ones. The results showed that those tests met the requirement for simplicity, objectivity, and preeiseness for studies on visual and movement activities, suggesting that they should be used in researches more widely.
NGHIEN CLPU A N H HU'ANG C O A HOAT DONG BAY Q U A N SLT LEN MOT S6 CHl S6 DIEN TIM CCiA PHI CONG VIET NAM
Nguyin Tung Linh, Trin Ngoc Tuin, Vu Du'c Vipgng Hpc vien Quan y Nghien ciru dwgc thwc hien vdi muc tidu xdc djnh sw tac dgng ciia eae dieu kidn bay quan sw Idn mdt so ehi so didn tim d phi cdng quan sw Viet Nam. Doi tuxyng cua nghidn ciru Id 90 phi cdng qudn sw Vigt Nam. Cdc phi cdng ndy dwgc chia Idm 3 nhdm: bay thwc nghiem don gian trdn buong Idi md phong, bay thwc nghigm phirc t^p tren buong Idi md phdng vd bay thwc dia. Kit qua cho thay thdi khoang QT eua dien tim giam giira trwdc bay, trong bay vd sau bay tren ca bay thwc nghiem va thuv dia vdi p<0,05, khi bay thi/c dia, thdi khoang QT giam 8,57%, do lech chuan cua 100RR tren didn tim ciia phi cdng gidm so vdi lue xuit phdt trdn cd bay thwc nghigm vd bay thwc dia, sw khde bigt cd y nghTa thong ke vdi p<0,01. Khi bay thwc dja, do lech chuan ciia 100RR trdn dien tim cua phi cdng giam 25,0% so vdi trwdc khi bay. Chirc nang hd tim mach cdng thing han khi bay tren thwc nghidm vd thwc dia vdi p<0,01. Khi thwc hidn cdc bdi bay don gian, chi s6 cdng thing tren didn tim tang 40,71%, khi thwc hign cac bai bay phirc tap, ehi so cang thing
Vietnam Joumal of Physiology 13(2), 8/2009 ISSN; 1859-2376
tren dien tim tang 55,27%, khi bay thwc dja, chi so cdng thing trdn dien tim cua phi cdng tdng 72,51%.
I.DATVANOe
Dien tim l i do thj ghi lai cac hoat dpng dien sinh hj* cua tim trong qui trinh tim hoat dpng.
Cie xung ddng didn dugc biiu dien dudi dang sdng. Sy thay doi bien dp, tin so, hinh dang cac sdng phan inh sy thay doi trong hoat dpng sinh \^ v i benh ly ca tim. Cd nhiiu yeu to anh hudng len dipn tim nhu trgng thai than kinh, lao dpng the lye, him lugng oxy trong khi thd, gia toe, henh ly tim mach v i cac ca quan...[2], [3], [4]. Khi thye hipn cac ginh ning lao dpng the lye ngudi ta thiy bien dp sdng T cao, co dinh, thdi gian QT giam ty le nghjeh vdi cudng dp lao dpng v i QT ludn can xung vdi khoang RR di torde [2], [6]. Sy thay doi ve nong dp oxy trong khi thd cQng lam dien tim thay doi. Thieu oxy lam giam bien dp sdng T, sdng T det hoic dao ngugc nhung thd oxy i p lye cao cung giy roi togn nhip tim. nhip tim ehim [2]. [5], [7], [8], [9].
Thye hien nhidm vy bay quin sy ngoai cie yeu to bat Igi hay gap trong hang khong nhu thiiu oxy. giam ip, gia toe, thay doi dp cao, ngudi phi cdng quan sy cdn phai chju eic yeu to die thii khic nhu tiing on Idn, thuc thi cie tinh huong nguy hiem va mau Ip, tham chi nguy hiem den tinh mang. Cac yeu to nay da tic ddng va giy ra sy thay doi dien tim d mCrc bdnh ly. Qua nghien eCru ECG d phi cdng quan sy, cac tic gia thiy cd 0,32% bj ngoai tam thu, 2% block nhinh, 8% ed sdng Q hoic S siu [1], [5], [8]. Da cd mpt so cdng trinh dugc thye hien d i dinh gii sy tic ddng cua thiiu oxy. gia toe.
tiing on, cang thing thin kinh len dien tim. Tuy
nhien, cac tic gia mdi chf dCrng lai d viec nghien CLPU anh hudng cua cie yeu to len dien tim sau khi bay. Dieu niy khdng danh gia dugc chinh xac sy tic dgng cua cac yeu to bat lgi doi vdi dien tim vi sau bay ngudi phi cdng quan sy khdng cdn chju cac ginh nang d mCrc dp cao theo dung nhu khi thye hien bay. Han nCi-a, chua cd tic gia nao de cap den viec danh g'li sy cing thing tren dien tim khi thye hien cac nhiem vu bay quan su. Sy cing thing dien tim la mpt yeu to gdp phan lam gia tang sy met moi trong bay, lam gia ting nguy ca mac cac benh ly tim mach ndi chung v i eic roi ban dipn tim ndi rieng [2]. Xuit phit tCr thye tiin tren, ehung tdi tien hanh thye hien de tii niy nham xac djnh sy tic dpng cua cac dieu kipn bay quan sy len mpt so ehl so dien tim d phi cdng quin sy Viet Nam.
2.06l TUCfHG VA PHUUNG PHAP NGHIEN CUOJ
2.1. Ddi tufomg nghien cihi
- Nghien eCru dugc tien hinh tren 90 phi cdng (PC) quin sy Viet Nam, va dugc chia thanh 3 nhdm
+ Nhdm 1; gom 60 PC bay vdng kin trong buong lai md phong.'
+ Nhdm 2; gim 60 PC bay d dp cao tmng binh tra len trong buong lai md phdng.
+ Nhdm 3; gom 30 PC SU- 22 bay thye dia.
2.2. Phuvmg phap nghien ci>u
- Nghien eCru tien CLPU, so sanh chieu dpc.
- Ghi dien tim v i tinh cac chf so thong ke ciia nhjp tim
Vietnam Joumal of Physblogy 13(2). 8/2009 ISSN: 1859-2376
+ Phuang phap ghi dien tim do; ghi d dao trinh Oil, 100 khoang RR lien tiep. ECG dugc ghi d 5 thdi diim; torde bay, cit cinh, ca dpng tren khdng (don gian, phuc tap), ha canh v i sau bay khi bay thye nghiem.
+ Cac chf so thong ke nhjp tim dugc xac dmh theo phuang phip cua Baevski R.M.;
• Phan tich cac chf so thong ke khoang each cua 100 nhjp tim (chf so TKTHNT); AX (giay) = RR toi da - RR toi thieu. Mo (giay);
Gii trj cua khoang RR gap nhieu nhit trong 100 RR, AMo (%); So lugng khoang
RR cd gii trj gap nhiiu nhat (Mo) trong 100 RR; RRtb (giiy) = tong so RR/100
• Tan so tim (nhjp/phut) = 60/RRtb
• SD (giiy): E)d lech ehuin cua 10ORR
• V; He so dao dpng eua 10ORR = SD/RRtb
• CSCT; chf so cang thing (dan vj diiu kien)= AMo/2AX.Mo
3. K^T QUA NGHIEN CUU
Cac kit qua nghien ciru dugc trinh biy tu- bing 1 + 2 v i biiu do 1
Kit qua trong bang 1 cho thay khi bay trong buong lai md phdng, thdi khoang QT Bang 1. Thdi khoang QT tren dien tim ciia phi cdng khi thye hien cac nhipm vu bay
trong buong lii md phdng va thye dja.
B i i bay
Dan gian (A) (n= 60)
Phu-c tap (B) (n= 60)
Bay thye dja (C) (n= 30)
PA-B PA-C PB-C
Chf so thong
ke X
± S D B.doi
(%) P
X
± S D B.doi
(%) P
X
± S D B.doi
(%) P
Thdi khoang QT (gy) Trude bay
(1) 0,35
±0,03
Cat c i n h (2)
0,30
±0,02 Giam 14,28%
CD tren khdng (3)
0,31
±0,03 Giam 11.42%
Hg canh (4)
0.30
± 0 . 0 1 Giam 14.28%
Sau bay (5)
0,31
±0,02 Giam 8,57%
Pi.2<0,05; pi.3<0,05; pi^<0,05; pi.5>0,05 0,36
±0,02
0,31
±0,04 Giam 13,88%
0,30
±0,05 Giam 16,66%
0,32
±0,03 Giam 11,11%
0.34
±0.02 Giam 5.55%
Pi.2<0,05; pi.3<0,05; pi^<0,05; pi.5>0,05 0,37
±0.03
0,32
±0,04 Giam 13.51%
Pi.5<0,05
>0.05
>0,05
>0,05
>0,05 <0.05 >0,05 >0.05
>0,05
>0,05
tren dien tim cua phi cdng giam cd y nghTa thong ke vdi p<0,05 so vdi luc xuit phit.
Vietnam Joumal of Physiology 13(2), 8/2009 ISSN; 1859 - 2376
Bang 2. Od Ipch chuan cua 100RR tren dien tim cua phi cdng khi thye hien cie nhiem vy bay trong buong lai md phdng v i thye ^a.
B i i bay
Dan gian (A) (n= 60)
PhCrc tap (B) (n= 60)
Bay thye dia (C) (n= 30)
PA-B PA-C PB-C
Chl so thong
ke X
± S D B.dii
(%) P
X
± S D B.doi (%)
P X
± S D B.doi
(%) P
Dp lech chuan cua 100RR (giay) Trude bay
(1) 0,046
±0,014
C i t c i n h (2)
0,035
±0,014 Giam 23,91%
CD tren khdng (3)
0,039
±0,011 Giam 15,21%
H?
c i n h (4) 0,035
±0,016 Giam 23,91%
Sau bay (5)
0.040
±0,015 Giam 13,04%
Pi.2<0,01; pi.3<0,01; pi^<0,01; Pi.5>0,05 0,042
±0,015
0,032
±0,013 Giam 23,80%
0,030
±0,017 Giam 28,57%
0,031
±0,012 Giam 26.19%
0.038
±0,016 Giam 9.52%
Pi.2<0,01; pi-3<0,01; Pi.4<0,01; Pi.5>0,05 0.044
±0,012
0.033
±0,014 Giam 25,0%
Pi-5<0.05
>0,05
>0,05
>0,05
>0,05 <0,05 >0,05 >0,05
>0,05
>0,05
Khi bay thye dja, mCre giam thdi khoang QT tren dien tim ciia phi cdng nhieu han 8,57% so vdi khi bay trong buong lii md phdng (5,55%).
Kit qua nghien eCru trong bang 2 cho thay khi bay trong buong lii md phdng, dp ideh chuan cua 100RR tren dipn tim ciia phi cdng giam so vdi luc xuit phit, cd y nghTa thing ke vdi p<0,01. Khi thuc hien eic bai bay phu-c tap, dp lech chuan cua 100RR tren dipn tim eua phi cdng giam ro nhit d thdi diim ca dpng (CD) tren khdng
(28,57%) v i ha canh (26,19%). Khi bay thye dja, dd lech chuan cua 100RR tren dien tim eua phi cdng d thdi diim sau khi ha canh giam 25,0% v i giam nhieu han so vdi khi bay trong buong lii md phdng.
Cie so lieu tren bleu do 1 cho thiy khi bay trong buong lii mo phdng, chf s6 cang thing tren dien tim ciia phi cong ting cao han so vdi luc xuit phat, sy khic biet cd y nghTa thong ke vdi p<0,01; khi thye hien cie bii bay dan gian, chf so cang thing tren dien tim tang cao nhit d cie thdi diim
Vietnam Joumal of Physiology 13(2). 8/2009 ISSN; 1859 - 2376
550 n 500 450 J 400 Q
> 350 Q H 300 U 3 250
200 150 100
376.66 422.83
265.67 -
264.41
315.21
458.33
101.41 296.68
••—Dan gian
* Phuc tap -•— Thuc dia
Trurcrcbay CSt canh Ccr (tpng Ha canh Sau bay
Bieu dd 1. Chf so cang thing tren dien tim cua phi cdng khi thye hien cac nhiem vu bay trong buong lii md phdng v i thye d\a.
cit canh (33,0%) va ha canh (40,71%).cdn khi ca dpng tren khdng, chf so cing thing tren dien tim tang it han (tang 19,21%); khi thye hien cac bai bay phCre tap, ehf so cing thing tren dien tim tang cao d ca 3 thdi diim: cit einh (38,32%), ca dpng tren khdng (55,27%) v i ha cinh (42,34%); khi bay thye dja, ehf so cing thing tren dipn tim cua phi cdng d thdi diim sau khi ha canh tang (72,51%) cao han so vdi luc xuit phat (12,20%) v i khi bay tren budng lai mo phdng (10,68%).
4. B A N LUAN
Nhii-ng yeu to bit lgi trong chuyin bay, die biet la thiiu oxy, gia toe, qui tai anh hudng Idn den sy biin dii cie thdng so cua dien tim. Thiiu oxy trong khi thd lam giam bien dp sdng T, sdng T dpt hoic dao ngugc [6]. Dudi anh hudng cua gia toe, qui tai, trdn ECG thiy ST chenh len hoic giam, T dao ngugc, d mdt so trudng hgp
cd roi loan nhip xoang, mpt so trudng hgp khac thay ting t i n so tim [5], [6]. [7]. [8]
hoac chim nhip xoang [5]. Kit qua nghien cu-u ciia cac t i c gia eho thay da so PC deu cd ty le dipn tim bit thudng tuang doi cao.
Kit qua nghien cu-u cua chCing tdi cho thay khdng ed PC nio cd biin doi bat thudng tren dien tim. Khi bay trong buong lii mo phdng, thdi khoang QT tren dien tim cua PC giam ed y nghTa thong ke vdi p<0,05 so vdi luc xuit p h i t Khi thye hipn cac bai bay phCrc tap. Thdi khoang QT tren dien tim eua PC giam rd nhit d thdi diem ca ddng tren khdng (giam 16,66%). Dieu niy phu hgp vdi kit qua nghidn cu-u khac v i biin doi ECG trong lao dpng [1], [5], [7], [8]. De dinh g i i trang thii cing thing cua he thing tim mach, chung tdi su- dyng ehf so thong ke toin hpe nhip tim (TKTHNT) eua Baevski va ehf s6 thing kd toin hpe nhjp tim thdng qua ghi dipn tim do 100
Vietnam Joumal of Physiology 13(2), 8/2009 ISSN: 1859-2376
nhip d dao trinh DII. C i e chf so TKTHNT eua 100 khoang RR lien t i i p cua dien j a m do bao g i m khoang RR trung binh (^), tan so nhjp tim trung binh (TSNT), dp Ipch chuin (SD) va he so dao dpng (V), Mdt (Mo), bidn dp Mdt (AMo) v i khoang dao dpng cua RR toi da v i toi t h i i u (AX). Chf so cang t h i n g (CSCT) la chf so b i c 2 dugc tinh tCr cac chf s6 tren (CSCT=AMo/2.
AX.Mo). Qua nghien CLPU chung tdi t h i y khi bay trong buong l i i md phdng, dp lech chuan cua 100RR tren dien tim ciia PC giam ed 9 nghTa thong ke vdi p<0,01 so vdi luc xuit phit. Khi thye hien c i e b i i bay phu-c tap, dp lech ehuin cua 100RR tren dien tim eua PC giam rd n h i t d thdi diem ca ddng tren khdng v i ha c i n h (giam 28,57% va 26,19%). Nhung khi bay thye dja, dd Ideh c h u i n cua 100RR tren dien tim cua PC d thdi diem sau khi ha c i n h giam 25,0% v i giam nhiiu han so vdi khi bay trong buong l i i md phdng (giam 13,04% v i 9,52%). Chi so cang t h i n g tren dien tim ciia PC khi bay trong buong l i i md phdng tang co y nghTa thong ke vdi p<0,01 so vdi luc xuit phit. Doi vdi e i c b i i bay dan gian, chf so c i n g t h i n g tren dien tim t i n g cao nhat d cac thdi diem c i t c i n h va ha c i n h (ting 33,0% va 40,71%), cdn khi ca dpng trdn khdng, chf so n i y t i n g it han (tang 19,21%). D i i vdi e i c b i i bay phu-e tap, ehf so cang t h i n g tren didn tim tang cao d ca 3 thdi diem: c i t c i n h , ca dpng tren khdng va ha cinh (ting 38,32%; 55.27% v i 42.34%).
Cdn khi bay thye dia. chf so cang thing tren dien tim cua PC d thdi d i i m sau khi ha
c i n h tang cao han so vdi luc xuat phit (tang 72,51%) v i tang cao han so vdi khi bay tren buong lai mo phong (tang 12,20%
v i 10,68%).
C i e k i t qua nghien eCru cua chung toi cho t h i y khi bay tren buong l i i mo phong va bay tren thye dia, d PC co bieu hien c i n g thing chuc nang he tim mach cao han, kha nang thich nghi thap han theo chf so TKTHNT. Sy bien doi nay t h i y rd nhat d cac thdi diem c i t canh va ha c i n h . Dieu n i y the hien d ket qua chf so dp lech chuan 100RR t h i p han v i CSCT cao han.
Chung tdi cho rang cang thing chCrc ning tim mach trong khi bay l i mpt trong nhu'ng nguydn nhan dan den cam giac met moi keo dai nhieu gid sau khi bay, d i e biet l i sau nhu'ng bai bay phirc tap v i d i n den sy bien doi tren diem tim ciia phi cdng.
5. K f T LUAN
- Co sy giam thai khoang QT tren dipn tim giu-a trude bay, trong bay v i sau bay tren ca bay thye nghidm v i thuc dja. Khi bay trong buong lai md phong, thdi khoang QT tren dien tim cua phi cdng giam vdi sy khac biet cd y nghTa thong ke vdi p<0,05; Khi bay thye dia, thdi khoang QT giam 8,57%, nhieu han so vdi trude khi bay v i so vdi khi bay trong buong l i i md phdng.
- Dp lech chuan cua 100RR tren dipn tim cua PC giam so vdi luc x u i t phit tren ca bay thye nghiem va bay thye dja, sy khac biet cd y nghTa thong ke vdi p<0,01. Khi thye hien b i i bay phu'C tap, dp lech chuan cua 10ORR trdn dien tim cua phi cdng giam nhieu d thdi diem ca dpng tren khdng v i
Vietnam Joumal of Physiology 13(2), 8/2009 ISSN: 1 8 5 9 - 2 3 7 6
ha einh. Khi bay thye dja, dp Ipch c h u i n eua 10ORR tren dien tim cua phi cdng giam nhiiu han d thdi diem sau khi ha canh giam 25,0% v i so vdi bay tren buong l i i md phdng (giam 13,04 v i 9,52%).
ChCrc nang he tim mach cang t h i n g han khi bay tren ca thye nghiem v i thye dja vdi p<0,01. Khi thuc hien cac b i i bay dan gian, chf so c i n g t h i n g tren dien tim cua cac PC t i n g 40,71%,khi thye hien c i e b i i bay phu-c tap, chf so cang t h i n g tren dien tim tang cao 55,27%, khi bay thye dja, chf so nay cua phi cdng tang 72,51%.
T A I LIEU THAM K H A O
1. Nguyin Ngan Binh (1989), "Ap dyng dipn tim van dpng tren xe dap luc k i trong g i i m djnh sCre khde phi cdng tren 35 tuoi", TC Ky thuat khdng qudn. So 3, tr.21- 24.
2. Bp mon Y hgc Quan binh chung HVQY (2002), y hgc lao dgng qudn sw, NXB Quan dpi nhan d i n . H i Npi, 329 tr.
3. Bp Qudc phdng (2004), Dieu 1$ an todn bay eua Khdng qudn nhdn ddn Viet Nam, NXB Q u i n dpi n h i n dan. H i Ndi, 100 tr.
4. Quach Van Mich, Nguyin Anh Hung va cs (2006), Nghien ciru mdt so yeu to nguy ca ve sux: khoe eua phi cdng qudn sw cd lidn quan den an todn bay vd de xuat bien phdp khac phuc, De tai NCKH cap Bp Quoe phdng. H i Npi, 78 tr.
5. Phan Van Thoai va cs (1994), "Kit qua nghien eCru didn tam do hai nam 1992- 1933 d mpt so phi cdng Hang khdng d i n dung Viet Nam", Tap ehi Sinh hgc Viet Nam, S6 d i e biet n h i n dgi hdi Sinh ly hpc Vipt Nam l i th Cr IV, H i Ndi, tr. 65- 67.
6. Barlow C. W. et al. (1991), "Post- exercise time-course analysis of ST segment and T wave changes: an important contribution to the role of stress electrocardiography in aircrew", Aviat Space Environ. Med., 62(2), pp. 165-171.
7. Comens P. (1998), "Effect of 100%
oxygen on EKG changes and serum myoglobin in fighter pilots", Aviat. Space Environ. Med., 69(2). pp. 149-153.
8. Dussault C , Jouanin J . C , Guezennec C Y . (2004), "EEG and ECG changes during selected flight sequences", Aviat.
Space. Environ Med., 75(10), pp. 889-89 9. Ekstrand K., Bostrom P. A. et al.
(1996), "Cardiovascular risk factors in commercial flight aircrew officers compared with those in the general population", Angioiogy. 47(11), pp. 1089-1094.
SUMMARY
Research in electrocardiography changes of Vietnam military pilots
as perform flying activities
Vi/e studied on 90 Vietnam military pilots;
Oiey were divided into 3 groups: simple task in a simulated flying chamtier, complicated task in the simulated flying chamber, and field task groups. The result showed that: there is a decrease in QT interval in all three groups.
The decrease was about 8.57% in the field task group.
The 100RR inten/al SD decreased compared with that of before flying (pO.01).
Flying in the fieki, 100RR SD decreased about 25.0% compared with that before flying.
Vietnam Joumal of Physiology 13(2), 8/2009 ISSN: 1 8 5 9 - 2 3 7 6
Cardbvaseular stress index is greater than that in the starting task (pO.01). The increase in cardhvaseular stress index in the simple
task, complicated task in the simulated flying chamber, and field task were 40.71%, 55.27%, and 72.51%, respectively.
NGHIEN CLfU SLT BI^N 0 6 l MOT S 6 CHl S 6 TIM MACH C O A PHI CONG Q U A N SLf VIET NAM TRONG HOAT DONG BAY
N g u y i n Tung Linh, T r i n Ngoc T u i n , Cao Hdng Phuc Hgc vien Quan y
Nghidn cwu duxyc thi/c hien vdi muc tieu ddnh gid sw bien doi mdt so ehi so tim mach d phi cdng qudn sw Viet Nam trong hoat ddng bay. Doi twgng nghien ciru la 90 phi cdng quan s y Vipt Nam. Cdc phi cdng ndy dwgc chia Idm 3 nhdm: bay thwc nghiem don gian tren buong Idi md phdng, bay thwc nghiem phirc tap tren buong lai md phdng va bay thwc dia. Ket qud nghien ciru cho thay: tan sd mpch, huyet dp, the tich tdm thu trong bay deu tang so vdi trwdc bay, vd giwa sau bay so vdi trwdc bay, tuy nhien sw tang ndy la khdng ddng ke vdi p>0,05; Trong khi dd, Iwu luxyng mau/phiit ciia phi cdng tang ed y nghTa thong ke vdi p<0,01 trdn cd bay thwc nghiem va thwc dia, giua trong bay vd trwdc bay. giwa sau bay vd trwdc bay. Lwu luxyng mau phiit lan Iuxyt tang la 32,46%, va 26,95% khi bay thuc nghipm vd bay thwc dia.
LOATVANDE
Tim mpch l i he thong ca quan c6 chCpc nang van chuyen m i u ehu-a oxy v i cac chit dinh duo-ng tdi e i c mo cua ca the.
Trong lao dpng, e i c ca quan trong ca the nhu tim mach, ho h i p , t h i n kinh... phai t i n g hoat dpng [1]. S y tang hoat dpng eua he tim mach dugc d i e trung bdi cac chf so t i n so mach v i huyet i p . Nhiiu cong trinh nghien eCru cho t h i y tan so mach v i hieu s6 huyit i p tang trong lao ddng. Dieu nay dugc giai thich l i do nhu c i u oxy ca the v i tidu hao nang lugng t i n g [1], [7]. Ngudi ta cung thiy, cac chf so tim mach thay doi khi thieu oxy, thay doi dd cao h o i c thay doi gia toe xay ra [1], [2]. Khi thieu oxy trong khi
thd. he tim mach se ed e i c phan u-ng bii trCr de dap Crng nhu cau oxy cho ca the.
Phan ung sdm nhat la t i n g tan so tim. Tan so tim tang ngay tCr dp cao 1.500-2.000 m.
Ngay ca khi khdng hoat dpng. t i n so tim cung tang 10% d dp cao 3.000 m, tang 15% d dp cao 4.500 m va tang 25% d dp cao 6.000 m [1], [9]. Khi van dpng trong dieu kien thieu oxy, tan so tim tang han nhieu so vdi muc tang khi van dpng d mat dat. Sy bien doi huyet ap cung tang theo xu hudng tang kha nang thich nghi ciia ca the. K i t qua nghien cu-u trong nhieu cdng trinh da chf ro huyet i p (HA) t i m thu t i n g 10 d i n 15 mmHg d dp cao 4.500 m, HA tam truang giam tir lOmmHg den 15
