Frequently Asked Questions
Chapter 39: Oxygenation

How do the respiratory muscles and respiratory centers in the brain work to produce respiration?

Inhalation begins when the diaphragm and the external intercostals contract, increasing the size of the intrathoracic space, elevating and separating the ribs, and moving the sternum forward. The result is a decrease in intrathoracic pressure, and inspiration of airs into the lungs. Stretch receptors in the lung tissue signal the brain to stop inhalation. After inhalation, the respiratory muscles relax, reducing the size of the intrathoracic space, increasing the intrathoracic pressure, and forcing air out of the lungs. Exhalation is usually passive.

What is represented on the oxyhemoglobin dissociation curve?

The oxyhemoglobin dissociation curve is a graphic representation of the shifts of oxygen from the hemoglobin molecule to the blood and back. A shift to the left of the curve represents an increase in the SaO2 in proportion to the PaO2. In this condition, the blood is carrying an adequate amount of oxygen but little of it is released from the hemoglobin to be carried to the tissue; this is caused by increased pH (alkalosis), hypothermia, or a decrease in the red blood cell enzyme 2,3-DPG (which occurs after a massive transfusion of banked blood). A shift to the right of the curve represents a decrease of SaO2 in proportion to the PaO2. This shift occurs with acidosis, hyperthermia, and hypoxia and results in an improved delivery of oxygen to the tissues.

What are the differences among the common pleural defects?

Pleural effusion is the collection of fluid between the pleural layers. Hemothorax is the collection of blood between the pleural layers. Pneumothorax is the collection of air between the pleural layers caused by a hole in one or both layers of the pleural membrane. Tension pneumothorax is a pneumothorax that rapidly expands with each respiratory cycle—a medical emergency requiring immediate medical attention.

What are some cautions to keep in mind when using a pulse oximeter on a client?

When using a pulse oximeter on a client, the nurse should remember that (1) the pulse oximeter uses light wavelengths to measure oxyhemoglobin saturation, but the readings are not as accurate as the SaO2 of arterial blood gases; (2) pulse oximetry measures the delivery of oxygen to the cells, but not the actual amount of oxygen used by the client; (3) bright environmental lights may cause a higher reading than an actual one; (4) anemia and low blood pressure, blood ph, Pco2, and body temperature can affect oximeter readings; and (5) health professionals have over-relied on pulse oximeter readings and under-relied on observations, vital signs, and actual lab values to make decisions about clinical care.

What questions should the nurse ask to elicit information about a cough during a health history?

The nurse should ask for the following information about a cough during a health history: (1) What was its onset? Was the onset gradual or sudden? (2) Is the cough dry, moist, barking, hacking, wheezing, or productive? If productive, what did the sputum look like? (3) When does the cough occur? Is it continuous or occasional? Related to time of day, position or activity, or the weather? Is it severe or mild? (4) What other symptoms occur at the same time (for example, pain, shortness of breath, or wheezing)? and (5) What types of medications or treatments are used to alleviate the cough?

What assessment strategies are important when assessing the affects of oxygenation on skin color?

When assessing the affects of oxygenation on skin color, the nurse should (1) use favorable lighting; (2) consider environmental factors, such as air conditioning, the use of vas-constricting medications, and smoking; (3) examine the least pigmented areas, such as the nails, lips, mucous membrane, conjunctiva, palms, and soles; and (4) observe for other clinical signs of decreased oxygenation to the brain, such as changes in the level of consciousness, increased respirations, use of accessory muscles of respiration, nasal flaring, and positional changes.