Chapter Summary Review
Structure and Function of the Pulmonary System
Recent insights into the regulation of breathing have been made in the field of autonomic neuroscience.
The structural and functional architecture of respiratory networks in the brainstem is crucial for breathing regulation.
Uncontrolled oxygen administration can lead to respiratory failure in acute asthma.
Chemosensory pathways in the brainstem control cardiorespiratory activity.
Murray and Nadel’s textbook of respiratory medicine is a key reference for respiratory care.
Air trapping in the alveoli and airways, consolidation of lung tissue, cavities, and nodules
Ventilation is the process by which air flows into and out of the gas-exchange airways.
Spiking and bursting pacemakers play a role in the neuronal control of breathing.
Two methods are compared to assess blood CO2 equilibration curve in mechanically ventilated patients.
Chest radiographs
Vital capacity decreases and residual volume increases
The largest amount of air that can enter and leave the lungs during respiration
Irritant receptors sense the need to expel unwanted substances.
Hypoxic pulmonary vasoconstriction is a physiological response to low oxygen levels in the lungs.
Surfactant plays a role in the pathobiology of pulmonary infection.
The pulmonary circulation and exercise responses change in the elderly.
At rest and during exercise
Structure and function in the very young and older adults
The gas-exchange airways are served by the pulmonary circulation.
The chest wall is lined by a serous membrane called the parietal pleura.
Models to understand contractile function in the airways are used in pulmonary pharmacology.
Riding a stationary bicycle or walking on a treadmill
The bronchi and other lung structures are served by a branch of the systemic circulation called the bronchial circulation.
The lungs are encased in a separate membrane called the visceral pleura.
There is increased immune dysregulation, asymptomatic low-grade inflammation, and increased risk of infection.
Loss of alveolar surface area and increased ventilation-perfusion mismatch contribute to the decline in PaO2 with age.
Changes in respiratory structure and function can vary considerably from person to person.
The normal range for PCO2 in arterial blood is 35-45 mmHg.
The Hering-Breuer reflex is related to lung volume and position in prematurely born infants.
Gender differences in airway behavior are observed over the human life span.
Asthma or emphysema
No, it remains unchanged
The maximum amount of air that can be expired from the lung in 1 second
Sometimes reported as maximum midexpiratory flow rate (MMFR)
The airway epithelium acts as a soldier in the fight against respiratory viruses.
Sublingual nitrate affects respiratory reflexes arising from stimulation of juxta-pulmonary capillary (J) receptors.
The novel paradigm for assessing pulmonary function in the aging lung involves new assessment techniques.
Abscesses or tuberculosis
Diminished alveolar surface area available for gas diffusion and decreased airway support
Decreased ventilatory reserves and decreased ventilation-perfusion ratios
Ventilation is controlled by the respiratory center in the brainstem and by the sympathetic and parasympathetic divisions of the ANS.
J-receptors sense alveolar size.
The normal pH range for mixed venous blood is 7.33-7.43.
The anatomy and neurophysiology of the cough reflex involve complex neural pathways.
Aging affects respiratory system physiology and immunology.
Pneumonia or pulmonary edema
They tend to lose alveoli wall tissue and capillaries
Vasoconstriction of the pulmonary arterial system is caused by alveolar hypoxia, acidemia, and inflammatory mediators (histamine, serotonin, prostaglandins, and bradykinin).
Stretch receptors sense lung volume (lung expansion).
Lung compliance is ensured by adequate production of surfactant.
Ventilation and perfusion are greatest in the bases of the lungs.
Surfactant therapy is used for acute lung injury and acute respiratory distress syndrome.
Muscarinic receptors on airway mesenchymal cells are a novel target for pulmonary pharmacology.
Structural and physiological age-associated changes occur in aging lungs.
Pa o2
Lung cancer
The chest wall contains and protects the contents of the thoracic cavity.
The pulmonary system enables oxygen to diffuse into the blood and CO2 to diffuse out of the blood.
The percentage of maximum inspiration that is expired in 1 second, usually 80% of FVC
Chemoreceptors in the circulatory system and brainstem sense the effectiveness of ventilation by monitoring the pH status of cerebrospinal fluid and the oxygen content of arterial blood (PaO2).
The perception of dyspnea remains intact and is even enhanced with age.
Respiratory muscle strength and endurance decrease with age.
Approximately 200 ml of CO2 is produced by the tissues per minute as a byproduct of cellular metabolism.
Mixed venous blood gas analysis is used for critically ill individuals and those undergoing cardiac catheterization.
The chief gas-exchange units of the lungs are the alveoli.
Central chemoreceptors are involved in the neural mechanisms of cardiorespiratory control.
Clinical manifestations and assessment of respiratory disease involve various diagnostic techniques.
Early changes in respiratory function
Ventilatory capacity
The amount of air that can be forcibly expired after a maximal inspiration
The maximum amount of gas that can be displaced from the lung during a forced expiration
The percentage of FVC that is expired in 3 seconds, usually 95% of FVC
Alterations in gas exchange are reflected by blood gas analysis.
Gas transport depends on ventilation of the alveoli, diffusion across the alveolocapillary membrane, perfusion of the pulmonary and systemic capillaries, and diffusion between systemic capillaries and tissue cells.
Changes are affected by activity and fitness earlier in life.
CO2 is more soluble in plasma than oxygen is.
Aging affects the mechanical aspects of ventilation by decreasing chest wall compliance and elastic recoil of the lungs.
The normal range for the partial pressure of oxygen (PO2) in arterial blood at sea level is 80-100 mmHg.
The normal range for the saturation of hemoglobin with oxygen (SO2) in mixed venous blood is 70-75%.
Carbonic acid quickly dissociates into H+ and HCO3− in red blood cells.
The amount of CO2 that is able to enter the blood is enhanced by the diffusion of oxygen out of the blood and into the cells.
Surfactant proteins SP-A and SP-D play diverse roles in innate and adaptive immunity.
Central respiratory chemoreception involves the detection of CO2/H+ levels in the blood.
The interaction of aging and lung disease affects respiratory health.
In routine chest radiographs of asymptomatic individuals
Elastic properties of the lungs and chest wall change, and chest wall compliance decreases
About 500 ml
The air that remains trapped in the alveoli
The maximum amount of gas that can be expired in 3 seconds
The major muscle of inspiration is the diaphragm.
PaO2 declines with age as a result of structural and mechanical changes.
Perfusion is greater in the bases as a result of gravity.
The pH value detects acidosis or alkalosis.
The saturation of hemoglobin with oxygen (SO2) indicates abnormalities of oxyhemoglobin association and dissociation.
H+ binds to hemoglobin as carbonic acid dissociates.
The binding of O2 to hemoglobin in the lungs facilitates the release of CO2 from the blood.
The bronchial arterial circulation is emerging as clinically important.
Central and peripheral chemoreceptors contribute to the ventilatory response to CO2/H+.
Airway clearance applications are important for the elderly and patients with neurologic or neuromuscular compromise.
When the system is stressed during exercise
Norms for the middle years
The chest wall loses some of its ability to expand
About 3300 ml
When the diaphragm contracts, it moves downward in the thoracic cavity, creating a vacuum that causes air to flow into the lungs.
Elastic recoil is the tendency of the lungs and chest wall to return to their resting state after inspiration.
Older adults are at greater risk for respiratory depression caused by medications due to changes in respiratory structure and function.
Oxygen is loaded onto hemoglobin by the driving pressure exerted by PaO2 in the plasma.
Bicarbonate (HCO3) measures the metabolic contribution to acid-base abnormality.
The enzyme carbonic anhydrase helps CO2 combine with water to form carbonic acid in red blood cells.
5% of the CO2 in arterial blood is carried as carbamino compounds.
O2 dissociation from hemoglobin facilitates the pickup of CO2 in the tissue capillaries.
The Haldane effect can have significant clinical implications for the management of lung disease.
Most pulmonary function tests are performed at hospitals and clinics.
Obstructive diseases affect gas flow.
The innate and adaptive immune response is induced by alveolar macrophages exposed to ambient particulate matter.
Renal acidification responses to respiratory acid-base disorders involve adjustments in kidney function.
Aging impacts CD8+ T cell immunity to respiratory virus infections.
Pa co2 or pH
Because the ribs become ossified and joints become stiffer
The chest wall consists of the skin, ribs, and intercostal muscles, which lie between the ribs.
The sympathetic and parasympathetic divisions of the ANS adjust airway caliber and control the rate and depth of ventilation.
Successful ventilation involves the mechanics of breathing: the interaction of forces and counterforces involving the muscles of inspiration and expiration, alveolar surface tension, elastic properties of the lungs and chest wall, and resistance to airflow.
Chest wall expansion depends on flexibility.
The alveoli in the bases are more compliant because their resting volume is low.
Radiographic examination of the chest evaluates air trapping, consolidation, cavity formation, or presence of tumors.
Hypothermia and decreased 2,3-BPG levels shift the curve to the left.
The normal range for the saturation of hemoglobin with oxygen (SO2) in arterial blood is 96-98%.
Approximately 10% of the total CO2 in venous blood is carried dissolved in the plasma.
The respiratory bronchioles, alveolar ducts, and alveoli together comprise the acinus.
The alveolar PaCO2 is 40 mmHg.
The effect of oxygen on CO2 transport is called the Haldane effect.
Nunn’s applied respiratory physiology is a comprehensive guide to respiratory function.
Reference values for arterial blood gases in the elderly are established for clinical assessment.
Spirometry and withdrawal of arterial blood for gas analysis
An understanding of changes from birth to old age
They decrease by up to 20%
Approximately 1000 ml
Surfactant is a lipoprotein that lines the alveoli.
The elastic recoil forces of the lungs and chest wall are in opposition and pull on each other, creating the normally negative pressure of the pleural space.
Hemoglobin is a protein contained within red blood cells.
The normal range for bicarbonate (HCO3) in arterial blood is 22-26 mEq/L.
The normal range for bicarbonate (HCO3) in mixed venous blood is 24-28 mEq/L.
The normal range for base excess (BE) in mixed venous blood is 0 to +4.
Changes in these elastic properties reduce ventilatory reserve.
The elimination of CO2 by the lungs plays an important role in the regulation of acid-base balance.
Air is inspired and expired through the conducting airways, which include the nasopharynx, oropharynx, trachea, bronchi, and bronchioles to the sixteenth division.
The drop in SaO2 at the tissue level increases the ability of hemoglobin to carry CO2 back to the lung.
The diffusion of CO2 out of the blood is enhanced by oxygen binding with hemoglobin in the lung.
Pulmonary function tests provide valuable information about the possible cause of a respiratory abnormality and evaluate the progression or resolution of disease.
Planning and evaluating exercise and rehabilitation programs
Loss of elastic recoil, stiffening of the chest wall, changes in gas exchange, and increases in flow resistance
The pulmonary circulation is innervated by the ANS.
The area where the parietal and visceral pleurae come into contact and slide over each other is called the pleural space.
Ventilation is involuntary most of the time.
Surfactant reduces alveolar surface tension and permits the alveoli to expand more easily with air intake.
The maximum PaO2 in an older adult at sea level can be estimated by multiplying the person’s age by 0.3 and subtracting the product from 100.
The remainder of the oxygen is transported dissolved in plasma.
The normal range for PCO2 in mixed venous blood is 41-57 mmHg.
Spirometry measures volume and flow rate during forced expiration.
Aging does not affect the PaCO2.
With aging, there is a decrease in vital capacity and an increase in residual volume.
CO2 is 20 times more soluble than O2.
By environmental and sociocultural factors, nutritional status, respiratory disease, body size, gender, and race
Vasodilation and vasoconstriction are controlled mainly by local and humoral factors, particularly arterial oxygenation and acid-base status.
Chemoreceptors become less sensitive to gas partial pressures with age.
An 80-year-old individual would have an estimated maximum PaO2 of 76 mmHg.
Oxygen enters the body by diffusing down the concentration gradient, from high concentrations in the alveoli to lower concentrations in the capillaries.
Arterial blood gas analysis can be used to determine pH and oxygen and CO2 concentrations.
Base excess (BE) reflects the deviation of bicarbonate concentration from normal.
The partial pressure of oxygen (PO2) indicates the driving pressure that causes oxyhemoglobin binding.
CO2 must be eliminated continuously to prevent acidosis.
As CO2 moves into the blood, it diffuses into the red blood cells.
Approximately 30% of the CO2 in venous blood is carried as carbamino compounds.
CO2 quickly diffuses into the alveoli because it is so soluble in the alveolocapillary membrane.
A spirogram records the individual’s ventilation in relation to time.
Neuroreceptors in the lungs monitor the mechanical aspects of ventilation.
The alveoli produce surfactant, produced by type II alveolar cells.
Almost all of the oxygen that diffuses into pulmonary capillary blood is transported by hemoglobin.
As pressure decreases at tissue level, oxygen dissociates from hemoglobin and enters tissue cells by diffusion, again down the concentration gradient.
Diffusing capacity is a measure of the gas diffusion rate at the alveolocapillary membrane.
The concentration of hemoglobin in the blood detects alterations of gas transport caused by anemia.
90% of the CO2 in arterial blood is carried in the form of bicarbonate.
The venous PvCO2 is 46 mmHg.
Several laboratory tests aid in the diagnosis and evaluation of pulmonary system abnormalities.
The most important spirometric tests are the forced vital capacity (FVC) and the forced expiratory volume in 1 second (FEV1).
Diffusing capacity is a measure of the rate of gas diffusion across the alveolocapillary membrane.
Diffusing capacity is decreased in individuals with emphysema.
With advancing age, pH and PaCO2 do not change much.
Efficient gas exchange depends on an even distribution of ventilation and perfusion within the lungs.
A very active, physically fit individual will have fewer changes in function at any age than one who has been sedentary.
The normal range for base excess (BE) in arterial blood is -2 to +2.
The pulmonary system consists of the lungs, airways, chest wall, diaphragm, and pulmonary and bronchial circulation.
Reduced hemoglobin (hemoglobin that is dissociated from oxygen) is able to carry more CO2 than hemoglobin that is saturated with O2.
Diffusion of CO2 in the lung is so efficient that diffusion defects that cause hypoxemia do not cause hypercapnia.
Spirometry is used to measure forced expiration.
Spirometry can detect restrictive or obstructive deficits early in the course of disease.
In restrictive lung diseases, the lungs are unable to expand normally, diminishing the amount of gas that can be inspired.
In obstructive diseases, airflow into and out of the lungs is obstructed.
Spirometry measures both volume and flow.
Direct analysis of pH and gas concentrations in arterial blood provides valuable information about an individual’s gas exchange and acid-base status.
Compliance is the ability of the lungs and chest wall to expand during inspiration.
There is a decrease in the capillary network with age.
The normal pH range for arterial blood is 7.35-7.45.
The alveolar-arterial oxygen gradient is used to evaluate the cause of hypoxia.
The normal concentration of hemoglobin in the blood is 15 g/dl.
Approximately 60% of the CO2 in venous blood is carried in the form of bicarbonate.
The diffusion gradient for CO2 in the lung is approximately 6 mmHg.
Restrictive lung diseases restrict the lungs’ volume.
A decreased diffusing capacity can be the result of an abnormal ventilation-perfusion ratio or an actual diffusion defect.
Older adults have a decreased compensatory response to hypercapnia and hypoxemia.
The decrease in PaO2 and diminished ventilatory reserve lead to a decrease in exercise tolerance in older adults.
Diffusion ceases when alveolar and capillary oxygen pressures equilibrate.
CO2 returns to the lungs dissolved in plasma, as bicarbonate, or in carbamino compounds (e.g., bound to hemoglobin).
CO2 is carried in the blood in three ways: dissolved in plasma, as bicarbonate, and as carbamino compounds.
Gas exchange occurs in structures beyond the sixteenth division: the respiratory bronchioles, alveolar ducts, and alveoli.
The measurement of diffusing capacity is made by determining how much carbon monoxide is taken up by the blood and dividing this amount by the pressure gradient across the alveolocapillary membrane.
The partial pressure of carbon dioxide (PCO2) measures the adequacy of ventilation and respiratory contribution of acid-base abnormality.
Aging causes the PaO2 to decrease.
The normal range for the partial pressure of oxygen (PO2) in mixed venous blood is 35-40 mmHg.
5% of the CO2 in arterial blood is carried dissolved in the plasma.
The remainder of CO2 combines with blood proteins, particularly hemoglobin, to form carbamino compounds.
A spirometer is a water-filled cylinder into which an inverted cylinder or bell has been inserted.
Mixed venous blood gas analysis provides important information about the adequacy of cardiac output and tissue oxygenation.
The membrane that surrounds each alveolus and contains the pulmonary capillaries is called the alveolocapillary membrane.
CO2 in the blood is removed from the lung with each expiration.
As hemoglobin binds with O2, the amount of CO2 carried by the blood is decreased.
The bell of a spirometer is attached to a pen that writes on calibrated paper rotating at a constant speed.
A blood gas report may be divided into an acid-base/ventilation portion and an oxygenation portion.
Oxygen, or more commonly carbon monoxide, is used to measure diffusing capacity.
Acidosis (low pH), alkalosis (high pH), ventilatory alterations, and decreased PaO2 can be diagnosed accurately only by arterial blood gas analysis.
Lung capacities, such as vital capacity and total lung capacity, are always the sum of two or more volumes.
Norms for volumes and capacities are based on age, gender, and height and are referred to as predicted values.
Helium is often added to the gas mixture to obtain a simultaneous measurement of residual volume (RV), functional reserve capacity (FRC), and total lung capacity (TLC).
Arterial blood gas analysis is commonly performed for individuals with suggested or diagnosed pulmonary disease.
