Podcast
Questions and Answers
What is the primary determinant of airway resistance?
What is the primary determinant of airway resistance?
- Elastic resistance of the lung
- Surface tension forces at the alveolar air-fluid interface
- Radius of the airway (correct)
- Compliance of the chest wall
Which of the following would increase lung compliance?
Which of the following would increase lung compliance?
- Production of surfactant (correct)
- Increase in surface tension forces
- Increase in elastic resistance of the lung
- Decrease in chest wall stiffness
A patient with airflow obstruction would likely have a decreased:
A patient with airflow obstruction would likely have a decreased:
- FEV1/FVC ratio
- Peak expiratory flow rate
- FVC
- All of the above (correct)
Dynamic compression of airways occurs during:
Dynamic compression of airways occurs during:
Which of the following is NOT a symptom of increased work of breathing?
Which of the following is NOT a symptom of increased work of breathing?
Spirometry is a test of lung function that measures:
Spirometry is a test of lung function that measures:
What is the relationship between flow and pressure difference according to Darcy's Law?
What is the relationship between flow and pressure difference according to Darcy's Law?
Which of the following is NOT a factor that determines resistance to flow?
Which of the following is NOT a factor that determines resistance to flow?
What happens to flow rate if the radius of a tube is halved, assuming the same pressure gradient?
What happens to flow rate if the radius of a tube is halved, assuming the same pressure gradient?
What is the main site of airway resistance in the respiratory system?
What is the main site of airway resistance in the respiratory system?
What is the equivalent of voltage in the context of flow through tubes?
What is the equivalent of voltage in the context of flow through tubes?
What is the relationship between resistance to flow and the length of a tube?
What is the relationship between resistance to flow and the length of a tube?
What is the site of highest individual airway resistance?
What is the site of highest individual airway resistance?
According to Darcy's Law, what is the relationship between flow and resistance to flow?
According to Darcy's Law, what is the relationship between flow and resistance to flow?
What is the primary mechanism by which high intrapleural pressures cause dynamic compression of airways during forced expiration?
What is the primary mechanism by which high intrapleural pressures cause dynamic compression of airways during forced expiration?
What is the main site of maximum airway resistance in the lungs?
What is the main site of maximum airway resistance in the lungs?
What is the effect of dynamic compression of airways on expiratory airflow in normal people?
What is the effect of dynamic compression of airways on expiratory airflow in normal people?
What is the unit of measurement for lung compliance?
What is the unit of measurement for lung compliance?
What is the primary determinant of elastic resistance in the lungs?
What is the primary determinant of elastic resistance in the lungs?
What is the role of neural inspiratory activity in regulating airway diameter?
What is the role of neural inspiratory activity in regulating airway diameter?
What is the primary mechanism by which adrenaline (in blood) affects airway diameter?
What is the primary mechanism by which adrenaline (in blood) affects airway diameter?
What is the effect of high RAW on expiratory airflow in people with lung disease?
What is the effect of high RAW on expiratory airflow in people with lung disease?
What is the primary factor affecting airway diameter during forced expiration?
What is the primary factor affecting airway diameter during forced expiration?
What is the term used to describe the effort-independent nature of expiratory airflow at low lung volumes?
What is the term used to describe the effort-independent nature of expiratory airflow at low lung volumes?
In a patient with lung fibrosis, which of the following is true?
In a patient with lung fibrosis, which of the following is true?
What is the characteristic feature of the flow-volume loop in obstructive airway disease of smaller airways?
What is the characteristic feature of the flow-volume loop in obstructive airway disease of smaller airways?
During respiratory muscle weakness, which of the following is true regarding FRC?
During respiratory muscle weakness, which of the following is true regarding FRC?
What is the effect of emphysema on lung compliance?
What is the effect of emphysema on lung compliance?
Which of the following would lead to an increased FEV1/FVC ratio?
Which of the following would lead to an increased FEV1/FVC ratio?
What is the relationship between FEV1 and FVC in restrictive disease?
What is the relationship between FEV1 and FVC in restrictive disease?
Surfactant plays a crucial role in reducing which of the following at the alveolar air-fluid interface?
Surfactant plays a crucial role in reducing which of the following at the alveolar air-fluid interface?
What is the effect of lung stiffness on FRC?
What is the effect of lung stiffness on FRC?
A patient with emphysema would likely have which of the following?
A patient with emphysema would likely have which of the following?
What is the feature of the flow-volume loop in normal individuals?
What is the feature of the flow-volume loop in normal individuals?
Which of the following would be affected by changes in stiffness of the lungs?
Which of the following would be affected by changes in stiffness of the lungs?
What is the effect of lung fibrosis on lung compliance?
What is the effect of lung fibrosis on lung compliance?
What is the characteristic feature of the flow-volume loop in restrictive lung disease?
What is the characteristic feature of the flow-volume loop in restrictive lung disease?
What is the effect of asthma on lung compliance?
What is the effect of asthma on lung compliance?
Study Notes
Lung Mechanics 2
Factors Affecting Airway Resistance
- Two main sources of resistance to breathing: elastic resistance of the lung and airway resistance
- Airway resistance is affected by two main factors:
- Factors within the airways (bronchial smooth muscle tone, inflammation of epithelium with hypertrophy of glands and secretions)
- Pressure across the airway wall (negative intrapleural pressure in normal breathing, positive intrapleural pressure in forced expiration)
- Medium-sized bronchi (around generation 3-5) contribute most to airway resistance
Dynamic Compression of Airways
- Occurs when airway pressure falls below pleural pressure during a forced expiration
- Airways most likely to collapse are bronchi around generation 3 or 4
- Causes limitation of expiratory airflow at low lung volumes (effort-independent airflow)
- In lungs with high airway resistance, it causes marked limitation of airflow, leading to slow expiration, low peak expiratory flow rate, air trapping, and expiratory wheezes
Lung Compliance
- Elastic resistance of the lung, usually measured as compliance (stretchiness)
- Compliance = change in lung volume / change in transpulmonary pressure
- Healthy lungs have high compliance (easy to expand), while stiff lungs have low compliance (hard to expand)
- Lung fibrosis (scarred/stiff) has low compliance, while emphysema (tissue destruction/floppy) has high compliance
- Asthma does not usually affect compliance
Measuring Lung Compliance
- Transmural pressure gradient = alveolar pressure - intrapleural pressure
- Intrapleural pressure measured with an oesophageal balloon, volume measured with a spirometer
- Subject breathes in from RV to TLC in steps to measure compliance
Simple Tests of Lung Function
- Spirometry: measures lung function and detects airflow obstruction
- FEV1 (forced expiratory volume in 1 second): measures airflow obstruction
- FVC (forced vital capacity): measures lung size and detects restrictive lung disease
- FEV1/FVC ratio: detects airflow obstruction (normal > 0.7)
- Peak expiratory flow rate: measures airflow obstruction and detects small airway disease
Effects of Chest Wall & Pulmonary Restriction and Airflow Obstruction
- Chest wall and pulmonary restriction: decrease FEV1, FVC, and peak expiratory flow rate
- Airflow obstruction: decrease FEV1, FEV1/FVC ratio, and peak expiratory flow rate, while FVC may be normal or decreased
Surface Tension Forces and Surfactant
- Surface tension forces at the alveolar air-fluid interface important for lung expansion and stability
- Surfactant: a complex mixture of lipids and proteins produced by type II alveolar cells, reduces surface tension and facilitates lung expansion
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Description
This quiz covers the main sources of resistance to breathing, including elastic resistance and airway resistance, and the factors that affect airway resistance, such as bronchial smooth muscle tone and intrapleural pressure. Learn about the mechanisms that influence airway resistance in normal breathing and forced expiration.
