Respiratory insufficiencies 1

Question 1

Respiratory diseases can occur due to: (3)

Answer 1

1. Inadequate ventilation
2. Abnormalities of diffusion through the pulmonary membrane
3. Abnormal transportation of gases in the blood

Question 2

What methods can be used to determine respiratory abnormalities?

Answer 2

1. Study of blood gases and pH
2. Measurement of Maximum Expiratory Flow
3. Forced Expiratory Vital Capacity and Forced Expiratory Volume

Question 3

The study of blood gases looks at which parameters?

Answer 3

PCO2, PO2, pH using a single droplet-sized blood sample.

Question 4

What technique can be used to measure PO2 concentration in a fluid sample?

Answer 4

Polarography

Question 5

What do Arterial Blood Gases (ABGs) determine?

Answer 5

They determine acidosis and alkalosis

Question 6

Differentiate between acidosis and alkalosis

Answer 6

A decrease in the elimination of CO2 by the lungs (hypoventilation) cause a decrease in blood pH Respiratory Acidosis
* Respiratory alkalosis occur as result of increase in pH secondary to a decrease in PCO2 and is due to an increase in the elimination of CO2 by the lungs (hyperventilation)

Question 7

What are the normal ranges for blood pH, PO2, and PCO2 respectively?

Answer 7

pH = 7.35-7.45 (pH < 7.35 = Acidosis; pH> 7.45 = Alkalosis)
PO2 = >85 mmHg
PCO2 = 35-45 mmHg

Question 8

Explain what maximum expiratory flow is.

Answer 8

When a person expires with great force, the
expiratory airflow reaches a maximum flow beyond
which the flow cannot be increased any more, even
with greatly increased additional force = This is called maximum expiratory flow or peak expiratory flow.

Question 9

When is maximum expiratory flow the greatest?

Answer 9

The maximum expiratory flow is greater when the
lungs are filled with a large volume of air than when they are almost empty.

Question 10

Explain the procedure for measuring PEFR using a peak flow meter (3 steps)

Answer 10

1. Take a full inspiration to maximum lung capacity.
2. Seal the lips tightly around the mouthpiece.
3. Blow out forcefully into the peak flow meter, held horizontally

Question 11

What is the normal PEFR? And what factors can cause difference in values from one person to another?

Answer 11

Normal PEFR is 400–650 L/min in healthy adults.
* Values differ according to height, age and sex of the patient

Question 12

What could cause a low PEFR

Answer 12

PEFR is reduced in conditions that cause airway obstruction
e.g. asthma

Question 13

Explain how constricted lungs would look like in a maximum expiratory flow-volume curve, and state reasons for this

Answer 13

In constricted lungs, both reduced total lung capacity (TLC) and reduced residual volume (RV) are reduced.
This is because the lung cannot expand to a normal maximum volume. Therefore, the maximal expiratory flow cannot rise to equal
that of the normal curve.

Question 14

What are some examples of constricted lung diseases

Answer 14

Constricted lung diseases include fibrotic diseases of the lung e.g. tuberculosis and diseases that constrict the chest cage e.g. scoliosis.

Question 15

Explain how airway obstruction diseases would look like in a maximum expiratory flow-volume curve, and state reasons for this

Answer 15

They would have a high RV and TLC but a low maximum expiratory flow rate.
This is because in diseases with airway obstruction, expiration is difficult than inspiration because the tendency of airways to close.
* Extra negative pleural pressure during inspiration “pulls” the airways open while it expands the alveoli. Therefore, air tends to enter the lung easily but then becomes trapped in the lungs.
*Over a period of months or years, trapped air increases both the TLC and RV.
* The obstruction of the airway greatly reduces the
maximum expiratory flow rate.

Question 16

Name examples of obstructive conditions

Answer 16

Asthma and emphysema

Question 17

FVC and FEV is measured using a __________________

Answer 17

Spirometer

Question 18

Explain how to measure FVC using a spirometer

Answer 18

Procedure for measuring the FVC:- first inspires maximally to the TLC and then exhales into the spirometer with maximum expiratory effort as rapidly and as completely as possible.

The total distance of the downslope of the lung volume record represents the FVC

Question 19

How is FEV1, FVC, and the ratio between the two values in restrictive conditions?

Answer 19

➢ Both FEV1 and FVC are reduced, often in proportion to each other
➢ FEV1:FVC ratio is normal or increased (> 80%)

Question 20

How is FEV1, FVC, and the ratio between the two values in obstructive conditions?

Answer 20

High intrathoracic pressures generated by forced expiration cause premature closure
of the airways with trapping of air in the chest
➢ FEV1 is reduced significantly than FVC.
➢ FEV1:FVC ratio is reduced (< 80%).

Question 21

Explain chronic infection

Answer 21

• inhaling smoke or other substances
  that irritate the bronchi and bronchioles. Nicotine in cigarette smoke paralyses cilia of the respiratory epithelium and as result mucus cannot be moved easily out of the passageways. Alveolar macrophages are also inhibited, weakening the combating of lung infection.

Question 22

Explain inflammatory edema

Answer 22

Inflammatory oedema as result of infection and excess mucus cause obstruction of many of the smaller airways.
*Obstruction of the airways makes expiration difficult, therefore cause entrapment of air in the alveoli and alveoli expansion reduce surface area for gaseous exchange.

Question 23

Explain the pathophysiology of emphysema

Answer 23

Infection cause a massive loss of alveolar walls therefore significant decreases the diffusing capacity of the lung. The overall result is reduced oxygenation of the blood and decrease capacity to remove CO2 from the blood.
* The obstructive process causes poor ventilation is some portions of the lung.
* The loss of the alveolar walls reduces the number of pulmonary capillaries that carry blood throughout the lungs.
* Pulmonary vascular resistance increases markedly, causing pulmonary hypertension, which in turn overloads the right side of the heart and frequently causes right-sided heart failure.

Question 24

What is pneumonia and what microorganism is usually responsible for causing this condition?

Answer 24

Pneumonia refers any inflammatory condition of the lung in which some or all of the alveoli are filled with fluid and blood cells.
* A common type of pneumonia is bacterial pneumonia, caused most by pneumococci.

Question 25

How does pneumonia usually begin?

Answer 25

It usually begins with alveolar infection which causes inflammation of the pulmonary membrane

Question 26

How does pneumonia affect the pulmonary membrane?

Answer 26

The pulmonary membrane become highly porous, allowing fluid and even blood cells to leak out of
the blood into the alveoli.

Question 27

How does the pneumonia infection spread within the lung?

Answer 27

the infection spreads by extension of bacteria or
virus from alveolus to alveolus

Question 28

Pneumonia causes the lung to eventually become ________________ which means that they are
filled with fluid and cellular debris.

Answer 28

Consolidated

Question 29

State the 2 major pulmonary abnormalities caused by pneumonia

Answer 29

1. Reduction in the total available surface area of the respiratory membrane
2. A decreased ventilation-perfusion ratio.
   *Both these effects cause hypoxemia (low blood O2) and hypercapnia (high blood CO2)

Question 30

What is atelectasis, and what causes it?

Answer 30

*The term atelectasis means collapse of the alveoli.
*Atelectasis can occur in a portion of a lung or in an entire lung.
*The common causes of atelectasis are:
1. Total obstruction of the airway.
2. lack of surfactant in the fluids lining the alveoli

Question 31

What are the 2 causes of airway obstruction type of atelectasis?

Answer 31

The airway obstruction type of atelectasis usually occurs because of the following:
➢ Blockage of many small bronchi with mucus
➢ Obstruction of a major bronchus by a large mucous plug or some solid object, e.g. a tumor

Question 32

How does airway obstruction lead to edema in fibrotic lungs?

Answer 32

-If the lung is rigid because of fibrotic tissue and alveoli cannot collapse, absorption of air from the alveoli into
pulmonary capillaries creates very negative pressures.
-The negative pressure with the alveoli within the alveoli, pull fluid out of the pulmonary capillaries
into the alveoli, thus causing the alveoli to fill completely with edema fluid.

Question 33

What happens to the blood flow & ventilation-perfusion ratio in the lungs when atelectasis occurs?

Answer 33

Vascular constriction occurs due to alveolar collapse, and blood is redirected to the ventilated lung.
As a result, the overall ventilation-perfusion ratio is slightly compromised and the aortic blood has only mild O2 desaturation, despite total loss of ventilation in an entire lung.

Question 34

Which cells secrete surfactant, and what is its function?

Answer 34

Surfactant is secreted by special alveolar epithelial cells (type II pneumocytes) into the fluids that coat the inside surface of the alveoli.
The function of surfactant is to decrease alveoli surface tension and plays a major role in preventing alveolar collapse.

Question 35

Explain hyaline membrane disease

Answer 35

In conditions, such as in hyaline membrane disease (also called respiratory distress syndrome), which
often affects in newborn premature babies, the quantity of surfactant secreted by the alveoli is reduced.
* This surfactant deficiency causes a serious tendency for the lungs of these babies to collapse or to become filled with fluid.
* Infants’ death may occur because of suffocation when large portions of the lungs become atelectatic.

Question 36

Briefly explain asthma

Answer 36

Asthma is characterized by spastic contraction of the smooth muscle in the bronchioles, which partially obstructs the bronchioles and causes extremely difficult breathing. It is contractile hypersensitivity of the bronchioles in response to foreign substances.

Question 37

What causes asthma in older people?

Answer 37

In older people, the cause is almost always hypersensitivity to nonallergenic types of irritants in the air, such as irritants in smog.

Question 38

What causes asthma in people younger than 30 years?

Answer 38

In people younger than 30 years, the asthma is usually caused by allergic hypersensitivity, especially sensitivity to plant pollens.

Question 39

Explain what happens when an asthmatic person inhales a substance that they are sensitive to, e.g. pollen. (6)

Answer 39

When an asthmatic person breathes in pollen to which he or she is sensitive (i.e., to which the person has already developed IgE antibodies during 1st exposure)
* The pollen reacts with the mast cell–attached antibodies and causes the mast cells to secrete inflammatory mediators: (1) histamine; (2) slow-reacting substance of anaphylaxis (which is a mixture of leukotrienes); (3) eosinophilic chemotactic factor; and (4) bradykinin (vasodilator).
* The combined effects of all these factors, especially the slow-reacting substance of anaphylaxis, are to produce the following:
1. Localized edema in the walls of the small bronchioles, as well as secretion of thick mucus into the bronchiolar lumens.
2. Spasm of the bronchiolar smooth muscle.
* The overall effect is that the airway resistance increases greatly.

Question 40

What pathogen causes Tuberculosis?

Answer 40

It is causes by the bacterium called tubercle bacilli

Question 41

What does tubercle bacilli cause in the lung?

Answer 41

Tubercle bacilli cause:
1. Attraction of macrophages to the site infection tissue
2. “walling off” of the lesion by fibrous tissue to form the so-called tubercle

Question 42

What is the function of the walling off process, and what happens if the walling off process fails?

Answer 42

The walling-off process helps limit further transmission of the tubercle bacilli in the lungs.
* If the disease is not treated, the walling-off process fails, and tubercle bacilli spread throughout the lungs,
causing extreme destruction of lung tissue, with formation of large abscess (swollen and pus
accumulation) cavities.