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Questions and Answers

In a newborn with respiratory distress syndrome, what is the primary deficiency?

Alveolar surface tension

Chest wall compliance

Pulmonary surfactant (correct)

Lung elasticity

What is the primary function of inspiratory reserve volume?

To increase the lung's compliance

To provide additional oxygen during exercise (correct)

To decrease the lung's elasticity

To measure lung capacity during spirometry

What is the effect of emphysema on lung compliance?

Increases lung compliance (correct)

Depends on the severity of emphysema

Decreases lung compliance

Has no effect on lung compliance

What is the primary muscle involved in quiet expiration?

None, as expiration is passive Signup and view all the answers

What is the percentage of total energy expenditure spent on the work of breathing during normal quiet breathing?

3% Signup and view all the answers

What is the effect of kyphosis and scoliosis on lung compliance?

Decreases lung compliance Signup and view all the answers

What is the term for the work required to overcome the viscosity of lung and chest wall structures?

Tissue resistance work Signup and view all the answers

What is the term for the work required to expand the lungs against elastic forces?

Elastic work Signup and view all the answers

What is the primary factor that determines the characteristics of the compliance diagram?

The elastic forces of the lung tissue itself Signup and view all the answers

What happens to the elastin and collagen fibers in the lung parenchyma when the lungs expand?

They become stretched and unkinked Signup and view all the answers

What is the primary mechanism by which the lungs are expanded during inspiration?

Contraction of the diaphragm and external intercostal muscles Signup and view all the answers

What is the primary function of surfactant in the lungs?

To reduce the tendency of the lungs to recoil Signup and view all the answers

Which of the following muscles are involved in forced expiration?

Internal intercostal muscles and abdominal muscles Signup and view all the answers

What is the effect of a decrease in compliance on respiratory volumes and capacities?

A decrease in tidal volume and functional residual capacity Signup and view all the answers

What is the effect of increased surface tension on the lungs?

It causes the alveoli to try to collapse Signup and view all the answers

What is the direction of the change in intrapleural pressure during inspiration?

Decrease Signup and view all the answers

What is the compliance of the lungs when removed from the thoracic cage?

0.22 L/cm H2O Signup and view all the answers

What is the result of the elastic recoil of the lung tissue itself?

The lungs become less compliant Signup and view all the answers

Which of the following is a measure of lung stretchability?

Compliance Signup and view all the answers

What is the effect of contraction of the sternocleidomastoid muscles on the respiratory system?

Lifting of the sternum Signup and view all the answers

Study Notes

Inspiration and Expiration

During inspiration, contraction of the diaphragm pulls the lower surfaces of the lungs downward
Extra force is achieved by contraction of external intercostal muscles, sternocleidomastoid muscles, anterior serrati, and scaleni
During heavy breathing, additional muscles involved are internal intercostals and abdominal recti

Lung Volume and Pressure Changes

Intra-alveolar and intrapleural pressure changes throughout the respiratory cycle
Compliance is the magnitude of change in lung volume by a given change in transmural pressure gradient (ΔV / ΔP)
Compliance measures the stretchability of the lungs and chest wall

Compliance Diagram

Compliance diagram shows the characteristics of the lungs alone
Elastic forces of the lung tissue itself (elastic recoil) and surface tension of the fluid lining the alveoli determine the compliance diagram
Asbestosis leads to stiff lungs, requiring more force to stretch: less compliant

Elastic Recoil and Surface Tension

Elastic recoil is the tendency of the lungs to return to pre-inspiratory volume when inspiratory muscles relax
Elastin and collagen fibers in the lung parenchyma are responsible for elastic recoil
Surface tension causes the alveoli to try to collapse, exerting an elastic contractile force on the entire lung

Surfactant

Surfactant is a complex mixture of lipids and proteins that lowers alveolar surface tension
Benefits of surfactant include reducing the tendency to recoil and increasing pulmonary compliance

Pulmonary Elastic Behavior

Elastic connective tissue (elastin fibers) and alveolar surface tension contribute to pulmonary elastic behavior
Surface tension is responsible for 2/3 of pulmonary elastic behavior

Alveolar Structure

Alveoli have a surface area, with 10% of the surface area composed of alveoli
Interdependence of the alveoli maintains lung stability

Newborn Respiratory Distress Syndrome (RDS)

RDS is caused by a deficiency of pulmonary surfactant in infants born prematurely
More difficult to expand collapsed alveoli than to increase partially expanded alveoli

Changes in Compliance

Decreased compliance is seen in fibrotic lung tissue, pulmonary congestion, kyphosis, scoliosis, and paralyzed or fibrotic muscles
Increased compliance is seen in emphysema

Work of Breathing

Work of breathing includes compliance work, tissue resistance work, and airway resistance work
Work of breathing increases in cases of pulmonary compliance, airway resistance, and elastic recoil

Spirometry

Spirometry is a method for studying pulmonary ventilation by recording volume movement of air into and out of the lungs

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