4 The disease asthoma is a discase characterized by bronchoconstriction (narrowi

Question

4 The disease asthoma is a discase characterized by bronchoconstriction (narrowing of the airways), airway inflammsticon you would expect to see on spirometry for a patienst with asthma. 5 Why should a person breathe into a paper bag when he or she is hyperventilating abnormally? 6 A patient presents in a state of ketoacidosis (a type of metabolic acidosis in which the pH of the blood drops) caused by poorly controlled diabetes mellites. Will the patient be hyperventilating or hypoventilating? Why? 7 Why does the ventilatory rate increase during exercise? 548 I Exploring Anatomy& Physiology in the Laboratory

Explanation / Answer

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A4. There are some parameters assessed using spirometry which shows deviations from the normal values and can be useful in the diagnosis of asthma.

Forced expiratory volume per second (FEV1)- the volume of air exhaled in one second under force after a maximal inhalation. Generally, for asthmatics, this value is lesser than the normal. This value decreases in proportion to the severity of any lung disease.

Forced expiratory volume/Forced Vital capacity ratio (FEV1/FCV) - this ratio is also lower for people showing any case of bronchoconstriction or pulmonary obstruction.

A5. The physiological pH of human blood is slightly on the alkaline side (7.35-7.45, it may vary from textbooks to textbook but will be 7 only!). When a person is hyperventilating, excess of CO2 accumulated in the human body is given back into the atmosphere at a faster rate. This may result in systemic alkalosis and can be quickly and conveniently corrected by lowering the pH of the blood. A smart way is to just 're-breathe' our own air by placing a paper bag in front of our nose and mouth which can essentially bring in more CO2 in a human body and restore the physiological pH than what normal breathing does which is, in fact, a slow process.

A6. Diabetic ketoacidosis occurs due to the accumulation of high concentration of ketone bodies in blood viz. acetoacetic acid and beta-hydroxybutyric acid. These acids decrease the pH of human blood. The decrease in pH activates the chemoreceptors and they sense an increase in hydrogen ion concentration and this condition often associated with increased CO2. Subsequently, in order to restore the physiological pH, the respiratory centers send nerve impulses and to drive away the excess of CO2. This creates a state of hyperventilation. In case of diabetic ketoacidosis, this elevated ventilatory rate is termed as Kussmaul breathing.

A7. Ventilatory rate means the amount of air inspired in a defined time period. During exercise, more oxygen is used by the body to cater to increased oxygen needs, especially the muscular tissue. This, in turn, produces copious amounts of CO2 which needs to be removed from our body so as to prevent the condition of systemic acidosis. CO2 itself acts as a stimulant for respiratory centers in CNS. The nerve impulses from the respiratory centers then reach the intercostal muscles and diaphragm and lead to more active movement. This leads to hyperventilation. To sum up, in order to get rid of CO2 from our body and cater to increased oxygen demand by a human body, hyperventilation is an obligatory response given by our body during exercises or activities which require more physical effort.

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