Walsh: Perinatal and Pediatric Respiratory Care, 3rd Edition

Chapter 12: Oxygen Administration

Answers to Assessment Questions and Clinical Scenarios

1.	B
Rationale: The documentation of hypoxemia through arterial blood gas sampling or pulse oximetry provides the most definitive evidence of actual or impending tissue hypoxia.
2.	D
Rationale: Nasal trauma and bleeding (epistaxis) may occur if the catheter is forced into small or obstructed nasal passages. If the catheter is not secured properly and slips past the oropharynx, gagging may occur and lead to vomiting and aspiration. Excessive flow can produce pain in the frontal sinuses as well as gastric distention and impaired diaphragm movement.
3.	A
Rationale: The decrease in oxygenation status of this patient suggests that only a small increase in fraction of inspired oxygen (FiO2) is indicated, and this would be easily achieved with a nasal cannula.
4.	B
Rationale: It is also important that an adequate flow of gas be delivered to wash out any carbon dioxide that may accumulate inside the hood. In general, flow rates should be greater than 7 L/minute. Flows of 10 to 15 L/minute are adequate for most infants and children.
5.	D
Rationale: In the hypoxic child with increased respiratory rates and tidal volumes, the air-entrainment mask is the preferred oxygen delivery system because it is capable of maintaining total flows in excess of the patient’s inspiratory flow rate. Air-entrainment masks, or Venturi masks, are examples of high-flow systems that provide the patient’s entire inspiratory requirements while delivering predetermined, precise oxygen concentrations ranging from 24% to 50%.
6.	D
Rationale: Self-inflating bags incorporate reservoirs attached to the back of the bag which can provide high FiO2 to patients by supplying fresh oxygen to the bladder of the bag via a series of one-way valves.
7.	A
Rationale: If the patient’s spontaneous inspiratory flow rate exceeds the flow rate being provided to the nonrebreather bag, then the bladder could become collapsed. By increasing the flow rate, more fresh gas is supplied to the patient during inhalation and the bag does not deflate during inhalation.
8.	B
Rationale: On the basis of the capillary blood gas and saturations, the patient appears to be oxygenating and ventilating well. The Pco2 (partial pressure of oxygen, determined transcutaneously) is a poor indicator of arterial oxygenation; however, the Spo2 (percentage of oxygen saturation) indicates that the oxygen is set too high, which could place this infant at greater risk for developing retinopathy of prematurity (ROP). The proper measure would be to decrease the FiO2 and then reevaluate the Spo2. Evidence now exists that supports targeting Spo2 levels at 89% to 90% in infants weighing less than 1500 g.
9.	B
Rationale: The greatest disadvantage of using an incubator to administer oxygen is the inability to stabilize and maintain the FiO2, regardless of whether the unit has flow-controlling solenoids or conventional methods of oxygenation. This drawback results from the large open space within the incubator and the inherent leaks that occur.
10.	C
Rationale: To a greater extent than with the low-flow nasal cannula, there is considerable concern about the lack of knowledge of the actual amount of positive pressure generated when using a high-flow nasal cannula.