Mcq_mini3_(4)[1] Airway Resistance, Assessing Pulmonary Function

The normal value of FEV1/FVC is 80%. This means that 80% of the forced vital capacity is exhaled in the first second of the forced exhalation. This ratio is used to assess lung function and can help diagnose respiratory conditions such as obstructive lung diseases. A value of 80% indicates normal lung function, as the majority of the air is exhaled within the first second.

The value of FEV1/FVC being significantly below 80% indicates a lung obstructive disease. In a healthy person, the FEV1/FVC ratio is typically above 80%. In lung obstructive diseases, such as asthma or chronic obstructive pulmonary disease (COPD), there is a decrease in airflow due to narrowing or blockage of the airways. This leads to a decreased FEV1/FVC ratio as the person is unable to exhale as much air in the first second compared to their total lung capacity.

Normal expiration is a passive phase of respiration that does not require respiratory muscle force. During normal expiration, the diaphragm and external intercostal muscles relax, causing the lungs to recoil and air to be expelled from the lungs. This process does not require any conscious effort or voluntary control from the person.

Based on the given measurements, the patient's vital capacity, total lung capacity, and FEV-l are all significantly lower than the predicted values. This indicates a decrease in lung volume, suggesting a restrictive disease. A restrictive disease is characterized by a reduced ability of the lungs to expand and fill with air, leading to decreased lung volumes and capacities. This can be caused by conditions such as pulmonary fibrosis, chest wall deformities, or muscle weakness.

During an acute asthma attack, the airways become inflamed and narrowed, leading to difficulty in breathing. This narrowing of the airways causes a decrease in the Forced Expiratory Volume in 1 second (FEV1), which measures the amount of air forcefully exhaled in the first second of a forced breath. Therefore, a decreased FEV1 is associated with an asthma attack.

In a patient with chronic obstructive lung disease (emphysema), there is an increase in total lung capacity (TLC) due to air trapping and hyperinflation of the lungs. There is also an increase in residual volume (RV) because the patient is unable to fully exhale all the air from their lungs. The ratio of RV to TLC is also increased as a result of these changes. Therefore, an increase in TLC, RV, and RV/TLC ratio supports the diagnosis of emphysema.

The physiological dead space refers to the portion of the respiratory system where there is no gas exchange occurring. It is often increased in lung disease due to the impaired function of the lungs. In lung diseases such as chronic obstructive pulmonary disease (COPD) or asthma, there may be areas of the lungs that are not effectively ventilated, leading to an increase in physiological dead space. This can result in a decreased ability to exchange oxygen and carbon dioxide, leading to respiratory difficulties. The increase in physiological dead space is not directly measured using arterial PO2, but rather it is a characteristic feature observed in lung disease.

The partial pressure of a gas in a mixture is directly proportional to its mole fraction. In this case, the gas with 3 mol has a mole fraction of 3/10. Since the total pressure is 200 mm Hg, the partial pressure of the gas with 3 mol can be calculated as (3/10) * 200 mm Hg = 60 mm Hg. Therefore, the correct answer is 60 mm Hg.

Tracheoesophageal fistula is the most likely cause in this case because the infant is experiencing symptoms such as gagging and choking after swallowing milk, which suggests an abnormal connection between the trachea and esophagus. The excessive mucus around the mouth and nose, abdominal distention, pneumonitis, and air in the infant's stomach seen on radiographs further support this diagnosis. Hypertrophic pyloric stenosis, congenital lobar emphysema, respiratory distress syndrome, and pulmonary hypoplasia are not typically associated with these symptoms.

The correct developmental sequence for the stages mentioned is pseudoglandular period, canalicular period, terminal saccular period, alveolar period. This sequence represents the chronological order in which these stages occur during lung development. The pseudoglandular period is the earliest stage, followed by the canalicular period, terminal saccular period, and finally the alveolar period.

The function of the ductus venosus is to allow blood to bypass the hepatic sinusoids. This is important because the hepatic sinusoids are small blood vessels in the liver that can become congested with blood during fetal development. By bypassing the hepatic sinusoids, the ductus venosus ensures that oxygenated blood from the placenta can reach the rest of the fetal body without being filtered by the liver. This allows for efficient oxygenation of the fetal tissues and organs.

Alveolar epithelial cells type II are responsible for repairing the membrane of the alveolar surface. These cells are specialized in producing and secreting surfactant, a substance that helps to reduce surface tension in the alveoli and prevents their collapse. Additionally, alveolar epithelial cells type II have the ability to differentiate into type I cells, which are essential for gas exchange. Therefore, when the alveolar surface is injured, alveolar epithelial cells type II play a crucial role in repairing and maintaining the integrity of the membrane.

During an acute asthma attack, there is a narrowing of the airways due to inflammation and bronchoconstriction. This leads to a decrease in the amount of air that can be forcefully exhaled in one second, which is measured by FEV1 (forced expiratory volume in one second). Therefore, the correct answer is FEV1 is decreased.

The premature female infant is diagnosed with hyaline membrane disease (HMD), which is commonly seen in premature infants. HMD is caused by a deficiency of lung surfactant, a substance that helps to reduce surface tension in the alveoli and prevents them from collapsing. In premature infants, the production of lung surfactant is not yet fully developed, leading to difficulty in breathing and the formation of hyaline membranes in the alveoli. Therefore, the most likely deficiency in the infant is lung surfactant.

The highest resistance to expiratory airflow is expected to be measured close to the residual volume (RV) in a healthy person. This is because at RV, the lungs are at their most collapsed state, leading to narrower airways and increased resistance to airflow.

The expiratory muscles have their greatest force at total lung capacity (TLC). This is because TLC represents the maximum amount of air that can be contained in the lungs, and when the lungs are at their fullest, the expiratory muscles have to work harder to push out the air during exhalation. At minimal lung volume (resting volume of the lung), RV, and FRC, the expiratory muscles do not have to exert as much force since there is less air to be exhaled. At 60% of vital capacity (VC), the expiratory muscles are not at their maximum force as there is still more air that can be exhaled.

The correct answer is the pleuroperitoneal membrane. In a normal development, the pleuroperitoneal membrane separates the thoracic and abdominal cavities. However, in this infant, there is a defect in the left side of the body, allowing the abdominal contents to herniate into the thoracic cavity. This herniation inhibits lung development and inflation, resulting in pulmonary hypoplasia and life-threatening breathing difficulties.

During the development of the respiratory system, the respiratory bronchioles actually develop during the canalicular period. This is the correct statement because the canalicular period is the stage of lung development where the terminal bronchioles are formed, and the respiratory bronchioles are the branches that arise from the terminal bronchioles. Therefore, it is accurate to say that respiratory bronchioles develop during the canalicular period.

The ductus venosus is a shunt that allows oxygen-rich blood from the placenta to bypass the liver and flow directly into the inferior vena cava. This means that the blood in the ductus venosus has not yet been mixed with deoxygenated blood from other parts of the body. Therefore, the ductus venosus contains the highest level of oxygen among the given locations.

Based on the given information, the newborn male has symptoms of coughing, choking, and cyanosis prior to feeding, which are indicative of a problem with the esophagus. The fact that a nasogastric tube meets resistance at 10cm suggests a blockage in the esophagus. Additionally, the prenatal history of polyhydramnios is associated with esophageal atresia, which is a condition where the esophagus does not properly develop and is disconnected. Therefore, the most likely finding in this infant is esophageal atresia.

During the terminal sac period, the blood-air barrier is established in the lungs. This is the stage of lung development when the terminal sacs, which are the functional units of the lungs, begin to form. The terminal sacs are lined with specialized cells called type I and type II pneumocytes. Type I pneumocytes are responsible for the gas exchange between the lungs and the bloodstream, while type II pneumocytes produce surfactant, a substance that helps to reduce surface tension in the lungs and prevent them from collapsing. The establishment of the blood-air barrier during this period allows for efficient oxygenation of the blood and removal of carbon dioxide.