Med-Surg · chapter 11 · Gas Exchange, Airway Management, and Respiratory System Disorders
Concepts of Oxygenation and Perfusion
The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 3 practice questions with the reasoning.
Key points
Breath supports gas balance
Each breath provides an opportunity for the body to receive oxygen, remove carbon dioxide, and help maintain acid-base balance.
Functional respiratory requirements
A functioning respiratory system has adequate airflow in and out of the lungs, provides oxygen to fuel the body’s tissues, and allows sufficient clearance of carbon dioxide during exhalation.
Conducting zone purposes
The primary purposes of this zone are to humidify and warm air and to minimize the likelihood of pathogens and debris entering the body.
Mucociliary clearance
Respiratory epithelium generates mucus, which helps to catch and trap debris. The cilia of respiratory epithelium are short, hairlike structures that move continuously, sweeping mucus and debris toward the throat so it can be swallowed instead of advancing into the lower respiratory tract.
Carina foreign body response
The carina is the point where the trachea splits into the right and left primary bronchi. Specialized nervous tissue in the carina can detect foreign bodies (such as food) and will cause forceful coughing to expel it.
Pleural fluid function
A small volume of pleural fluid provides lubrication and creates surface tension to keep the lungs expanded.
Respiratory center control
The medulla oblongata in the brain is the respiratory center and controls breathing by responding to shifts in carbon dioxide, oxygen, and blood pH (potential hydrogen).
Alveolar surface area
Alveoli are elastic and stretch during inspiration, increasing the available surface area for gas exchange.
Ventilation pressure flow
Air flows from an area of high pressure to an area of low pressure. During inhalation, air passes through the conducting zone and travels to the respiratory bronchiole and the alveolar sacs.
Oxygen pressure gradient
Because there is a higher partial pressure of oxygen in the alveoli than the capillaries, the pressure gradient pulls oxygen into the bloodstream. Carbon dioxide in the blood diffuses across the capillaries into the alveoli, where it leaves the body during exhalation.
Oxygen blood transport
Because oxygen does not dissolve well in liquids, it uses red blood cells as a means of transportation. Oxygen molecules attach to hemoglobin in the red blood cells.
Decreased oxygenation factors
Any condition that creates a decreased respiratory rate or limitation of chest wall/diaphragmatic expansion can create a decrease in oxygenation either through hypoventilation or other factors.
Perfusion impairment
Factors that affect blood flow through the blood vessels of the lungs affect perfusion. When blood vessels are blocked or narrowed, it decreases the lung’s ability to oxygenate blood.
Ventilation-perfusion matching
Capillaries become constricted and blood flow is diverted to alveoli that are sufficiently ventilated. Conversely, in alveoli that are adequately ventilated, the diameter of the pulmonary arterioles increases in response to a greater partial pressure of oxygen in the alveoli.
Terms to know
- conducting zone
- The conducting zone includes all parts that help deliver air to the lower airway for ventilation and perfusion.
- respiratory zone
- The respiratory zone describes the parts that perform gas exchange.
- alveolus
- An alveolus is an individual, grapelike sac in the lungs where gas exchange occurs, and an alveolar sac is a group of alveoli.
- ventilation
- The movement of air into and out of the lungs, which allows gas exchange to occur, is called ventilation.
- oxygenation
- The process when oxygen from the air moves into the bloodstream is called oxygenation.
- diffusion
- When air enters the lungs and travels to the alveoli, oxygen molecules pass into the capillaries by diffusion, which is the movement of substances from an area of high concentration to an area of low concentration.
- partial pressure
- The term partial pressure refers to how much of a gas is dissolved in the blood.
- perfusion
- While the term perfusion is used to describe blood flow throughout all parts of the body, certain concepts specifically relate to perfusion of the respiratory system.
Practice questions
Stuck on select-all-that-apply? How to take them one option at a time.
The graded version needs JavaScript. Every question is below anyway, with the answer and why.
Every question here, with the answer
At 0900, a nurse is documenting how anemia affects oxygenation in a patient with decreased red blood cell volume. Which statement best connects this finding to its effect on oxygenation?
- Unventilated alveoli leave fewer capillaries available for gas exchange.
- Reduced hemoglobin limits the blood’s oxygen-carrying capability.
- Restricted pulmonary blood flow decreases the lungs’ ability to oxygenate blood.
- Narrowed airways limit airflow and reduce the oxygen available to the lungs.
Answer: Reduced hemoglobin limits the blood’s oxygen-carrying capability.
Decreased red blood cell volume reduces hemoglobin, limiting the blood’s ability to carry oxygen. Airway narrowing and unventilated alveoli describe different mechanisms associated with other conditions in the section. Restricted pulmonary blood flow describes a perfusion problem rather than the oxygen-carrying limitation identified here.
At 1400, a nurse explains how pulmonary blood flow responds when some alveoli are inadequately ventilated while others remain sufficiently ventilated. Which statements should the nurse include in the documented teaching summary? Select all that apply.
- Pulmonary vessels widen in poorly ventilated areas to bring in more blood.
- Capillary constriction reduces blood flow equally in poorly ventilated and sufficiently ventilated areas.
- Blood flow remains unchanged until ventilation improves in the affected alveoli.
- Capillaries in inadequately ventilated areas become constricted.
- Blood flow is redirected toward sufficiently ventilated alveoli.
Answer: Capillaries in inadequately ventilated areas become constricted., Blood flow is redirected toward sufficiently ventilated alveoli.
The section describes capillary constriction in inadequately ventilated areas and diversion of blood toward sufficiently ventilated alveoli. Widening vessels in poorly ventilated areas reverses that response, while unchanged flow or an equal reduction across regions misses the redistribution described.
At 1900, a nurse reviews a draft entry: “Oxygenation confirmed by air moving into and out of the lungs.” The entry is based only on observed air movement. Which replacement accurately identifies what that observation establishes?
- Air movement into and out of the lungs demonstrates ventilation.
- Air movement into and out of the lungs confirms oxygen diffusion into the bloodstream.
- Air movement into and out of the lungs demonstrates oxygen delivery to body tissues.
- Air movement into and out of the lungs confirms blood flow through pulmonary capillaries.
Answer: Air movement into and out of the lungs demonstrates ventilation.
Movement of air into and out of the lungs establishes ventilation. Oxygenation involves oxygen entering the bloodstream, while pulmonary perfusion involves blood flowing through pulmonary capillaries. The other entries claim oxygen transfer, pulmonary blood flow, or tissue oxygen delivery that the stated observation does not establish.
Where every quote comes from
Section 11.1 Concepts of Oxygenation and Perfusion of Medical-Surgical Nursing by Christy Bowen, Bridget Carey, Jessica Palozie, Maren Reinholdt, OpenStax, 2024. Read the whole section free at openstax.org.
The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.