EFFECT OF EXERCISE & OTHER FACTORS ON RESPIRATION

1. EFFECT OF EXERCISE & OTHER FACTORS ON RESPIRATION Lecture 8 Dr. Zahoor Ali Shaikh

2. Effect Of Exercise On Respiration • Alveolar Ventilation increases 20-fold during heavy exercise to keep pace with increased demand of O2 uptake and CO2 output. • Big three chemical factors that is decreased PO2, increased PCO2 and increased H+ does not play major role. • During exercise, ventilation increases at the onset of exercise within seconds, long before arterial blood gases could become important which requires minutes.

3. Factors Increasing Ventilation During Exercise • Reflexes originating from joints and muscle receptors during exercise reflexly stimulate the respiratory center. • Increase in body temperature during exercise stimulates ventilation. • Increased Epinephrine release during exercise stimulates ventilation. • Impulses from cerebral cortex, at the onset of exercise stimulates medullary respiratory neuron.

5. Adjustment In Ventilation In Response To Arterial H+ Changes In Acid – Base Balance • Increased H+ ion stimulates Peripheral Chemoreceptors, therefore, increased respiration occurs. • Increased H+ ion can be produced in acidosis e.g. diabetes mellitus [diabetic ketoacidosis]. • Central Chemoreceptors are affected by CO2 produced H+ in brain Extra Cellular Fluid [ECF].

6. Respiration Can Be Influenced By Factors Unrelated To Need For Gas Exchange • Respiratory rate and depth can be modified by 1. Sneezing & Coughing – these are protective reflexes to expel irritant material. 2. Pain - anywhere in the body reflexly stimulate respiration. 3. Laughing, crying modifies the respiration. 4. Hiccups – Spasmodic contraction of the diaphragm occurs, causing rapid intake of air which is suddenly halted by abrupt closure of glottis. 5. Swallowing – reflexly inhabits respiratory center to prevent food from entering the lungs.

8. Cyanosis • Cyanosis is a blue coloration of skin and mucous membranes. • It results when reduced Hemoglobin in capillary blood is more than 5g/100ml of blood. • Central Cyanosis occurs in severe hypoxia.

9. Hypoxia • Types of Hypoxia are given in the Slide 7 [Table 13-7]. Here is the example for each type of Hypoxia. • Hypoxic Hypoxia occurs in lung disease, at high altitude. • Anemic Hypoxia occurs in Anemia and CO Poisoning. • Circulatory Hypoxia or Stagnant Hypoxia occurs in slow circulation e.g. Cardiac failure. • Histotoxic Hypoxia occurs when tissues are not able to use O2. It occurs in Cyanide Poisoning.

10. {CLINICAL ASPECT} Sudden Infant Death Syndrome [SIDS] • In SIDS, Apnea occurs [stoppage of breathing] and patient is unable to recover from Apnea period and death occurs. • SIDS or crib [cot] death – It is the leading cause of death in the first year of life, usually 2-4 months old infant is found dead in his or her cot for no apparent reason.

11. {CLINICAL ASPECT} Sudden Infant Death Syndrome [SIDS] • Cause is not clear but different possibilities are put forward: • Baby forgets to breath – as respiratory control mechanism are immature either in brain stem or chemoreceptors are poorly developed. • Abnormal lung development . • Aspiration of gastric [stomach] juice containing Helicobacter pylori. • Combination of factors maybe involved.

12. {CLINICAL ASPECT} Sudden Infant Death Syndrome [SIDS] • Other Observations In SIDS • Sleeping position of baby – 40% increased incidents of SIDS is associated with sleeping on the abdomen rather than on the back or side. • Infants whose mother smoked during pregnancy are more likely to die of SIDS.

13. What You Should Know From This Lecture • Effect of Exercise on - O2 use and CO2 production - Alveolar Ventilation - Arterial PO2, Arterial PCO2, Arterial H+ level • Clinically Important Respiratory States [Given in Table 13-7 Slide 7] • Effect of H+ Changes On Ventilation In Acid Base Balance • Cyanosis • Hypoxia • Sudden Infant Death Syndrome [SIDS]