Período competitivo

Subjects

47 normal males ( aged 18 to 27 ) w ere used in this

study. Ten of the subjects w ere in training and underg­

oing various sorts of regular sporting activities. All the subjects underw ent b o th th e exercise and COp response

test and o f these subjects, the 11 untrained also under­

went an isocapnic hypoxia t e s t . An electrically braked

cycle erg o m eter was u sed , w ith th e load increased s te p w is e . The subject was f i r s t familiarised w ith using a n o s e -c lip

and breathing through the mouthpiece f o r 5 minutes p r i o r

to the exercise. None o f the subjects had any exercise

for at least $0 m inu tes b e fo re th e t e s t , to stabilise his 4

breathing pattern.

A f t e r 5 minutes, th e subject sat on th e cycle e rg o m e ter

and necessary adjustments made to th e h e ig h t o f the pedals

and mouthpiece. No unnecessary discomfort must be p re s e n t

as i t m ight disturb his b r e a th in g d u rin g later h ig h loads

of exercise. A f u r t h e r 5 m in u te rest p e r io d with th e mouth %

connected to the circuit was necessary, f o r b r e a th in g stab­

ilisation. This ensured th o ro u g h mixing of the expired gas

as well as keeping his COg and t i d a l sam ple within - 1 mm.Eg.

v a r i a t i o n . The subject th e n s ta r te d to pedal at 100 kpra

load k e e p in g the p e d a l fre q u e n c y a t 60 rpm f o r 2 to 3 mi- n u te s , u n t i l a s te a d y s t a te i s re a c h e d . The lo a d was th e n

in c re a s e d a t 100 kpm e v e ry 1 minute until he becomes exh~ |

austed.

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The OOg response test at rest was done on the same day but $ to 4 hours after, the exercise experiment. The isocapnic hypoxia experiment took place within a week of the exercise and COp response tests.

6 subjects repeated the exercise test within one week. Repeats of OOg and hypoxia response tests are discussed in Section 1A.

Equipments.

All subjects were weighed and their EVO, EEV and VO measured using the Vitalograph Single Breath Instrument.

a) Exercise. _{( Eig* 2—a )}

An electrically braked Cycle Ergometer ( ELEHA-SCHO- NANDER AM $68 ) was used for the exercise test. Stepwise increases of 100 kpm up to a maximum of 2000 kpm can be used. A mouthpiece was fitted to a low resistance two-way valve ( dead space of 140 ml ), with outlet of the valve going to a mixing chamber, volume 6 litres. A pneumotacho­ graph was attached to the inlet side of the valve, the

inspired flow measured by a Mercury Electric Manometer ( accuracy of - ) and the signal integrated. Inspired ventilation was measured for each tidal volume and used

later for measuring inspiratory and expiratory duration in Section $. The resistance for the inspired side was 2,0 cm.HgO and expired side was 1,1 cm.HgO at a flow rate of

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88

The mixing chambei' consisted of two separate halves with a gauze midwall for thorough mixing. In the second half of the chamber where air is thoroughly mixed, there

are two small outlets, one for Og measurement and the other for COp measurement. ?or COg measurement, a sample of air at a flow rate of 500 ml.min“* was passed through a Beckman COg Infra Red Medical Gas Analyser ( Model LB 1 ). The gas analyser ( accuracy - 1$ of meter-range of 0 to 10^ COg ) was calibrated using several gas mixtures which was first analysed by Lloyd-»Haldane apparatus. The COg meter was switched on overnight prior to the test for greater stability. The Og meter ( Paramagnetic-Servomex type OA 272 ) has air sample flowing at the rate of 200 ml,min*“ . Calibration of both meters was made every morning before a set of experiments were carried out later in the day. To monitor heart rate, 5 point chest electrodes are used and connected to a pen-x'ecorder ( DEVICES AC1 Pre-Amp with Sub 3 ECG sub-unit ). Simultaneous measurements of ventilation, heart rate, OOg# and Og# were made and recorded on a Devices four channel pen-recorder.

b) COg Response Test.

For this test, the same circuit, equipments and method were employed as in Section 1A.

In 16 subjects ( untrained ) in addition to ventilatory response, the maximum rate of development of pressure during occlusion, (dp/dt) , was measured; the mouth pressure signals differentiated into spikes which was recorded onto

89

a fast-responding pen-recorder ( GOULD BRUSH )# ( Section 1A ). Rebreathing was continued for 4 to 5 minutes or until the subject cannot continue longer. Repeat tests are discussed in Section 1A.

c) Response to Hypoxia*

For the hypoxia study at rest, details of the setup and method is discussed in Section 1A. The experiment took about 5 to 6 minutes. During the experiment COg and Og was measured continously by gas meters and minute volume measured by an electro-spirometer. The change in mouth

pressure was measured and differentiated to give (dp/dt) nicix # values.

11 subjects ( untrained ) underwent the test.

FORMULAE USED and CALCULATIONS.

The following formulae are used throughout the calcul­ ations.

1.00 - ( PgCOz + PgOg )

h ° 2 = % 0 . 2 0 9 5 VgOg = Vj X 0.7903

90

" VgOg

VCOg = FgCOg X Vj X 0.897

All values were corrected to STPD and BTPS as required,