Types of Ventilation and Lung Mechanics

Question 1

What is eupnoea?

Answer 1

Eupnoea refers to normal or unlaboured breathing
- inspiration is active and involves the diaphragm and external intercostals
- expiration is passive during eupnoea

Question 2

What is diaphragmatic breathing?

Answer 2

(deep breathing) type of breathing where the diaphragm is the primary muscle used for breathing.
- during low levels of activity, diaphragmatic breathing is sufficient

Question 3

What is costal breathing?

Answer 3

(shallow breathing) type of breathing where the primary muscles used for breathing are the external intercostal muscles.
- can occur in situations such as pregnancy or obesity, when the diaphragm is restricted

Question 4

What is hypoventilation?

Answer 4

Hypoventilation is a condition where there is inadequate alveolar ventilation, leading to an increase in VCO2/VA above normal

Question 5

What are the possible causes of hypoventilation?

Answer 5

• a respiratory disease
• a behavioural response
• a reduced output of the respiratory controller in the brainstem.
• examples include COPD, behavioural response to pain, and alcohol overdose

Question 6

What is the consequence of hypoventilation?

Answer 6

Can lead to respiratory acidosis, as poor CO2 excretion results in an increase in PACO2, PaCO2, H+, and a decrease in pH.

Question 7

What is hyperventilation?

Answer 7

Condition where VCO2/VA decreases below normal, leading to excess alveolar ventilation

Question 8

What causes hyperventilation?

Answer 8

• behavioral response
• or when the respiratory controller is stimulated by factors other than CO2, such as anxiety, panic or hyperventilation syndrome, and altitude

Question 9

What is the consequence of hyperventilation on blood pH?

Answer 9

Leads to respiratory alkalosis, due to increased alveolar excretion of CO2, which causes a decrease in PACO2, then in PaCO2, and an increase in pH through H+ ions.

Question 10

What is hyperpnoea of moderate exercise?

Answer 10

Refers to the increase in breathing rate and depth during moderate exercise, where the amount of CO2 produced by the body is precisely matched by the amount of CO2 exhaled, and the respiratory rate tracks CO2 production.

Question 11

What stimulates hyperventilation during heavy exercise?

Answer 11

During heavy exercise above the anaerobic threshold, hyperventilation is stimulated by lactic acid, which activates the respiratory controller in the brainstem.

Question 12

What is apnoea?

Answer 12

Apnoea refers to the cessation of breathing.

Question 13

What are some causes of apnoea?

Answer 13

• voluntary breath-holding
• asphyxiation
• drug overdose
• obstructive sleep apnoea (OSA)

Question 14

What is obstructive sleep apnoea?

Answer 14

Obstructive sleep apnoea (OSA) is a type of apnoea in which there is no airflow, but there are efforts to breathe and arousal.

Question 15

What is compliance in lung mechanics?

Answer 15

The distensibility of an elastic structure and how easy it is to inflate the lungs
- change in volume for a given change in pressure

Question 16

What is the relationship between volume and compliance in the lungs?

Answer 16

(inverse relationship)
Compliance of lungs decreases with increasing volume
- meaning that at higher volumes, more pressure is needed to increase the volume

Question 17

What is elastance in lung mechanics?

Answer 17

• reciprocal of compliance
  -a measure of the resistance to expansion

Question 18

How is elastance related to pressure and volume in the lungs?

Answer 18

Elastance is the change in pressure needed for a given change in volume

Question 19

What is Static Pressure-Volume Curve (Passive)?

Answer 19

Curve generated by measuring the lung volume at different airway pressures without any airflow (i.e., no respiratory muscle activity)

• low lung volumes = steep curve, indicating high compliance
• high lung volumes = curve levels off, indicating reduced compliance
• reflects the elastic properties of the lung and chest wall

Question 20

What is Maximum Inspiratory and Expiratory Pressures (Static)?

Answer 20

Measure of the strength of the respiratory muscles

• Maximal inspiratory pressure (MIP): the maximum negative pressure that can be generated during a forced inspiration
• Maximal expiratory pressure (MEP): the maximum positive pressure that can be generated during a forced expiration
• Used as an index of respiratory muscle strength and to assess the presence of respiratory muscle weakness.