Respiratory Physiology and Maximum Expiratory Flow

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Questions and Answers

What is the main reason why the maximum expiratory flow rate decreases as lung volume becomes smaller?

The volume of air in the lungs is reduced, decreasing the pressure gradient for airflow.

The bronchi and bronchioles are held open partially in the enlarged lung.

Airflow resistance increases as the lungs deflate. (correct)

The force of expiration is reduced as the lungs empty.

In which respiratory disease is the concept of maximum expiratory flow particularly relevant?

Bronchitis

Asthma (correct)

Pneumonia

Emphysema

What can be concluded about the relationship between lung volume and maximum expiratory flow?

Maximum expiratory flow is inversely proportional to lung volume.

Maximum expiratory flow is constant regardless of lung volume.

Maximum expiratory flow is greater when the lungs are full than when they are almost empty. (correct)

Maximum expiratory flow increases linearly with lung volume.

What is the maximum expiratory flow rate described in the text?

More than 400 L/min (A) Signup and view all the answers

What is the key characteristic of maximum expiratory flow?

It is the highest flow rate achievable with any expiratory effort. (C) Signup and view all the answers

What is the main reason why the maximum expiratory flow rate is limited?

The resistance of the airways (D) Signup and view all the answers

When is the maximum expiratory flow rate measured?

During forced exhalation (D) Signup and view all the answers

What does the curve recorded in the maximum expiratory flow test represent?

The maximum expiratory flow rate at all levels of lung volume (C) Signup and view all the answers

What happens when the lung cannot collapse due to fibrotic tissue?

Negative pressure in the alveoli pulls fluid from the pulmonary capillaries, filling the alveoli with edema fluid. (A) Signup and view all the answers

What condition is commonly associated with an insufficient amount of surfactant?

Hyaline membrane disease (D) Signup and view all the answers

What is the main function of surfactant?

To reduce surface tension in the alveoli. (E) Signup and view all the answers

What is the physiological effect of decreased surfactant in the lungs?

Increased likelihood of alveolar collapse. (A) Signup and view all the answers

Why is the lack of surfactant particularly problematic for premature babies?

Their respiratory system is not yet fully mature and they produce insufficient amounts of surfactant. (B) Signup and view all the answers

What is the primary cause of tissue hypoxia when O2 oxidase is blocked by cyanide?

Impaired oxygen utilization by tissues (C) Signup and view all the answers

What is the primary consequence of reduced lung diffusion capacity?

Decreased ability to remove CO2 from the blood (C) Signup and view all the answers

Which of these is NOT a direct consequence of reduced lung diffusion capacity?

Increased lung compliance (D) Signup and view all the answers

How does the uneven distribution of the obstructive process in the lungs affect ventilation?

It results in poorly ventilated areas with low VA/Q and well-ventilated areas with high VA/Q. (C) Signup and view all the answers

How does the loss of alveolar walls in emphysema affect pulmonary vascular resistance?

It increases pulmonary vascular resistance due to reduced capillary network. (A) Signup and view all the answers

Which statement best describes the development of hypoxia and hypercapnia in chronic emphysema?

Hypoxia and hypercapnia are caused by the combination of hypoventilation and loss of alveolar walls. (B) Signup and view all the answers

What is the primary indicator of a notable difference between individuals with similar lung volumes?

The forced expiratory volume in the first second (FEV1) (C) Signup and view all the answers

What is the primary reason for the obstruction of smaller airways in emphysema?

A combination of A and B (D) Signup and view all the answers

What is the key result of the obstructed airways in emphysema?

Trapping of air within the alveoli (A) Signup and view all the answers

How does emphysema cause a reduction in alveolar wall integrity?

Overstretching and destruction due to air trapping (B) Signup and view all the answers

What is the typical range of alveolar wall destruction observed in emphysema?

50-80% (B) Signup and view all the answers

What is the role of alveolar macrophages in emphysema?

They are inhibited and become less effective at fighting infection. (C) Signup and view all the answers

How does excess mucus secretion contribute to the symptoms of emphysema?

It contributes to the obstruction of airways, making it difficult to breathe. (B) Signup and view all the answers

What is the relationship between FEV1 and FVC in a person with emphysema, compared to a healthy person?

The FEV1/FVC ratio is much lower in a person with emphysema. (B) Signup and view all the answers

Which of the following is NOT a characteristic of asthma?

Permanent enlargement of the chest cage (D) Signup and view all the answers

In what percentage of people younger than 30 years is asthma caused by allergic hypersensitivity?

70% (C) Signup and view all the answers

What is the primary mechanism that aids in limiting the spread of tubercle bacilli in the lungs?

The formation of a fibrous wall around the infection site (C) Signup and view all the answers

How does the functional residual capacity and residual volume change during an asthma attack?

They both increase (A) Signup and view all the answers

What is the role of macrophages in the context of tuberculosis?

They engulf and digest the tubercle bacilli (B) Signup and view all the answers

In what percentage of people with tuberculosis does the disease progress despite the formation of a tubercle?

3% (C) Signup and view all the answers

What is the primary cause of asthma in older individuals?

Sensitivity to irritants in the air, such as those in smog (D) Signup and view all the answers

What is the approximate number of people worldwide suffering from asthma, according to the World Health Organization?

235 million (B) Signup and view all the answers

Study Notes

Respiratory Insufficiency - Pathophysiology, Diagnosis, Oxygen Therapy

Diagnosis and treatment of respiratory disorders relies heavily on understanding basic respiratory physiology and gas exchange.
Some respiratory diseases stem from inadequate ventilation, others from issues with diffusion through the pulmonary membrane or blood transport of gases.
Useful methods for studying respiratory abnormalities include measurements like vital capacity, tidal volume, functional residual capacity, dead space, physiological shunt, and physiological dead space. Additional methods are described for studying blood gases and blood pH.

Study of Blood Gases and Blood pH

Fundamental tests for assessing pulmonary function include determining blood partial pressures of oxygen (P02), carbon dioxide (CO2), and pH; rapid measurements are frequently needed to guide treatment.
Blood pH is measured using a miniaturized glass pH electrode, producing a voltage directly related to pH, often read from a voltmeter or charted.
Blood CO2 is measured using a glass electrode surrounded by a thin membrane separating it from bicarbonate solution. Blood CO2 diffuses into the solution, and the resulting pH change is used to calculate CO2.
Blood P02 is determined using polarography. Electric current between electrodes measures the proportional rate of O2 deposition, directly related to P02. Small electrodes with thin membranes surrounding them are used to minimize interference from other blood components.
Modern equipment combines pH, CO2, and P02 measurements into a single device allowing bedside monitoring of blood gas levels and pH.

Measurement of Maximum Expiratory Flow

Maximum expiratory flow is the maximal airflow rate during maximum exhalation, useful for assessing airflow resistance in diseases such as asthma.
Maximum expiratory flow is greater at larger lung volumes compared to smaller lung volumes due to differences in bronchiolar and airway support.
Abnormalities in the max. expiratory flow-volume curve indicate lung conditions like constricted lungs and airway obstruction.
Constricted lung conditions (fibrotic diseases, chest cage constrictions) result in lower maximum expiratory flow rates overall.
Airway obstruction makes exhalation more difficult, leading to a distinctly shallower maximum expiratory flow-volume curve shape.

Forced Expiratory Vital Capacity (FVC) and Forced Expiratory Volume (FEV1)

Forced expiratory vital capacity (FVC) and forced expiratory volume in the first second (FEV1) help assess lung function.
FVC measures the total capacity to exhale forcefully; FEV1 measures the volume exhaled in the first second of forced exhalation.
Normal FEV1/FVC ratio is approximately 80%, in diseases with airway obstruction this ratio is reduced.

Pathophysiology of Specific Pulmonary Abnormalities

Chronic pulmonary emphysema involves a complex destructive process in the lungs, characterized by chronic infection, excessive mucus, and inflammatory edema.
The obstructive process results in air trapping, alveolar overstretching, and alveolar wall destruction.
Key factors causing reduced lung function in emphysema include bronchiolar obstruction limiting airflow, and diminished diffusion capacity as alveolar walls are destroyed.

Pneumonia - Lung Inflammation and Fluid in Alveoli

Pneumonia is an inflammatory lung condition where alveoli fill with fluid and cells.
Bacterial pneumonia, frequently caused by pneumococci, involves infection and ensuing fluid buildup in alveoli.
Pneumonia negatively impacts lung's gas exchange function by reducing respiratory membrane surface area and increasing membrane thickness.

Atelectasis - Collapse of Alveoli

Atelectasis refers to the collapse of alveoli, potentially due to airway obstruction or surfactant deficiency in the alveolar fluid.
Airway obstruction can result in atelectasis by trapping air in the blocked lung segment, leading to collapse.
Insufficient surfactant in alveolar fluid reduces surface tension, creating a propensity for alveolar collapse (especially in newborns).

Hypoxia and Oxygen Therapy

Hypoxia, or low blood oxygen, results from various causes including inadequate oxygenation of the blood, impaired blood transport, and tissue utilization.
Various types of hypoxia exist; causes of hypoxia are classified for appropriate management.
Oxygen therapy can be useful in treating hypoxia and hypercapnia, particularly when resulting from hypoventilation and certain types of lung disease.
Cyanosis is a bluish discoloration of the skin caused by excessive deoxygenated hemoglobin in blood vessels.

Hypercapnia - Excess Carbon Dioxide

Hypercapnia occurs when CO2 levels in the body fluids rise; this typically arises from hypoventilation or reduced respiratory function.
Elevated CO2 levels can hinder respiration, causing a potential cycle of decreased respiration and elevated CO2.
Hypercapnia is not associated with all types of hypoxia, unlike hypoventilation-related hypoxia.

Artificial Respiration

Resuscitators provide intermittent positive pressure to assist breathing.
Tank respirators employ a mechanism to deliver positive or negative pressure to aid inhalation and exhalation cycles.
Excessively high positive or negative pressures in these methods can impede venous return to the heart.

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Description

This quiz delves into the relationship between lung volume and maximum expiratory flow rate, particularly in the context of respiratory diseases. It addresses key concepts such as the role of surfactant and the physiological effects of lung conditions. Test your understanding of these important respiratory concepts!