Assistant Prof: Nermine Mounir RiadAin Shams University, Chest

Department

Oxygen is consumed in the production of ATP and that co2 is produced as waste product.

Respiratory quotient(RQ) this ratio of o2 consumption to co2 production.

It equals 0.8

Takes place by means of diffusion of substances.

External respiration:(within the lungs) Respiratory exchange ratio(R) is the ratio

of this exchange within the lungs between oxygen and carbon dioxide.

R= 200/250=0.8Internal respiration:(within the muscles)Gas exchange and nutrients.

1- The fuel needed for ATP production must be supplied.2-waste products that result from ATP production must be removed.

Metabolism parameters: 1-oxygen consumption:

-Normally at rest average 250 ml/min (3.5-4 ml/min/kg), with exercise it will increase directly with the level of muscular work, VO2 increase until exhaustion occurs and maximum level of O2consumption(VO2max) is reached.- VO2 max is a reproducible , well defined physiologic end point so it is used as a definitive indicator of an individual s muscular work capacity. Normally range from 1700-5800 ml/ min

2- CO2 production: Normally 200ml/min (2.8 ml/min/kg) During the initial phase of exercise it

increase at a rate similar to VO2, once the anaerobic threshold has been reached , VCO2 increases at a faster rate than VO2. the faster rate is the result of additional CO2 production from HCO3/CO2 buffering mechanism.

3-Anaerobic threshold: In normal individuals occurs at

approximately 60% ± 10% of the persons VO2 max.

At the onset of the AT , there is marked increase in CO2 production because of lactic acid buffering and a compensatory increase in ventilation.

After the onset of the AT, a breathlessness develops and a burning sensations begins in working muscles.

4-Respiratory Quotient: CO2 production ↑ during exercise esp. after

the AT has been achieved →↑RQ from resting levels of 0.8 to beyond 1.0

The subject will be able to continue exercise for a short period of time as much as 1.5

5-Blood PH: Remains relatively unchanged till the onset

of AT → the blood gradually becomes more acidotic as the body is less able to buffer the excessive acid (H)produced by anaerobic metabolism.

1-Minute Ventilation: Normally = 5-6 l/min,100l/min in maximal

exercise. At the very start of an exercise → vent. ↑(d.t.

resp. centers stimulation by the brain motor cortex and joint proprioceptors)

Humeral factors (chemoreceptors) do the fine tuning of vent.

The level of vent. Continue increasing correspondingly with the increase of the workload till AT reached → vent. ↑ in a rate greater than the rate of workload ↑to compensate for the additional C02 produced during anaerobic metabolism.

2-Tidal volume: Normally = 500 ml, 2.3-3 L during

exercise Increase early in exercise and are initially

responsible for the increase in vent.3-Breathing Rate: Normally = 12-16bpm, up to 40-50 bpm Responsible for the increase in minute

ventilation that occur late in maximal exercise, esp. after AT reached

4-Dead space/ Tidal volume Ratio: Normally= 0.20-0.40, ↓ during exercise

0.04-0.20 ↓significantly during exercise d.t ↑in

tidal volume with constant dead space5-Pulmonary capillary blood transit time: Normally= 0.75 second, ↓ 0.38 second

d.t ↑ C.O.

6-Alveolar-Arterial Oxygen Difference: Normally= 10 mmHg changes little until

a heavy workload is achieved . However, it can increase to 20-30 mmHg.

7-Oxygen Transport: Local conditions of increased temp.,

PCO2 and a relative acidosis in the muscle tissues → greater release of oxygen by the blood for use by the tissues for metabolism.

1-Cardiac Output: Normally = 4-6L/min up to 20L/min Increase linearly with increases in the

workload during exercise till the point of exhaustion.

At work levels of up 50%of an individuals exercise capacity, the ↑ in C.O is d.t ↑ in heart rate and stroke volume together. After this point, it ll be d.t. in ↑ heart rate.

2-Stroke Volume: Normally = 50-80 ml can double during

exercise. Increase linearly with increase in

workload until a maximum value is achieved, ≈ 50% of an individuals capacity for exercise.

After a HR of about 120bpm , there is little additional increase in SV → CO increase based in HR.

3-Heart Rate: Can increase as much as 2.5-4 times the

resting HR. HR max is achieved just prior of total

exhaustion, considered as physiologic end point for each individual.

HRmax (±10bpm)= 210-(0.65X age) HRmax (±10bpm)=220- age

4-Oxygen pulse: In order to meet the demands of

increasing muscle work during exercise, each heart contraction must deliver a greater quantity of oxygen out to the body.

O2 pulse= VO2/HR Normally = 2.5-4 ml o2/ heart beat up to

10-15 ml in exercise.

5-Blood pressure: During exercise→↑systolic blood pressure (up to

200mmHg) while diastolic blood pressure remains relatively stable( may ↑up to 90mmHg)

Pulse pressure (difference between systolic and diastolic pressure) ↑ during exercise.

6-Arterial- Venous Oxygen Content Difference: During maximal exercise the difference ↑2.5-3 times

the resting value. (N. 5 vol%) The ↑ is due to the greater amounts of O2 that are

extracted by the working muscle tissue during exercise.

7-Distribution of circulation: Circulation to the skeletal muscles

increases which in turn increase the cardiac output.

Circulation to the heart ↑. Skin perfusion ↑ as cooling mechanism for the

body but can ↓ at extreme exercise levels (as the muscles demand ↑)

Thank you