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Lecture 8Dr. Zahoor Ali Shaikh

EFFECT OF EXERCISE & OTHER FACTORS ON

RESPIRATION

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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.

Effect Of Exercise On Respiration

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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.

Factors Increasing Ventilation During Exercise

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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.

Respiration Can Be Influenced By Factors Unrelated To Need For

Gas Exchange

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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.

6. Speaking, singing, and whistling: We also control our breathing to perform such voluntary acts.

Respiration Can Be Influenced By Factors Unrelated To Need For Gas Exchange [cont]

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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 in lung disease, Right to left shunt eg Ventricular septal defect.

Cyanosis

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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.

Hypoxia

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APNEA & SLEEP APNEAApnea is the transient interruption of

ventilation, with breathing resuming spontaneously. If breathing does not resume, the condition is called respiratory arrest.

During sleep ventilation is normally decreased and the central chemoreceptors are less sensitive to the arterial PCO2 drive , victims of sleep apnea may stop breathing for a 10 seconds or longer many times in the night.

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Mild sleep apnea is not dangerous unless the sufferer has pulmonary or circulatory disease, which can be exacerbated by recurrent bouts of apnea.

APNEA & SLEEP APNEA [cont]

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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.

{CLINICAL ASPECT} Sudden Infant Death Syndrome [SIDS]

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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.

{CLINICAL ASPECT} Sudden Infant Death Syndrome [SIDS]

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Other Observations In SIDSSleeping 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.

{CLINICAL ASPECT} Sudden Infant Death Syndrome [SIDS]

Role of Respiration In Acid-Base BalancepH of blood – 7.4 [7.35-7.45]Lungs and kidneys regulate the pH of body.Lungs play important role in regulation of pH

because they excrete CO2.Respiratory Acidosis

If respiratory center is depressed e.g. brain damage, drugs, it will increase CO2 in the body which will increase H+.

CO2 + H2O H2CO3 H + HCO3If H+ ion increases – it will cause Respiratory

Acidosis.

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Respiratory Alkalosis If person hyperventilates, it will cause

loss of CO2 and H+ ions and pH becomes alkaline [respiratory alkalosis].

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Effect of Exercise on - O2 use and CO2 production - Alveolar Ventilation - Arterial PO2, Arterial PCO2, Arterial H+ levelClinically Important Respiratory States [Given in Table 13-7 Slide 7]CyanosisHypoxiaApnea Sudden Infant Death Syndrome [SIDS]Respiratory acidosis and alkalosis

What You Should Know From This Lecture

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Thank you