Chapter 5: Pulmonary Function Testing and Bedside Pulmonary Mechanics Test Bank

Multiple Choice

1. Which of the following major forces opposes inspiration?

a. Inspiratory flow b. Surface tension c. Airway resistance d. Respiratory rate

ANS: C

The combination of lung compliance (C) and airway resistance (Raw) is the major force opposing inspiration, whereas elastic recoil is the force responsible for passive normal exhalation.

REF: p. 66 a. The infant may require sedation for up to 3 hours. b. If the infant cries, it will make the test invalid or open to misinterpretation. c. The gases used for the PFT may be toxic for the infant. d. The inability to feed the child 24 hours prior to the test

2. Pulmonary function testing has been ordered in an infant. Which of the following represents a real risk to this infant?

ANS: B

In infant testing, the subject may need to be lightly sedated in the laboratory for 2 to 3 hours to complete a full set of studies. Sedation carries some risk, and testing should not be viewed as routine. The NPO guidelines from the hospital sedation policy may allow infants who are younger than 6 months to receive formula and solids for up to 6 hours, breast milk for up to 4 hours, and clear liquids for up to 2 hours before sedation. Children who are 6 months or older may receive solids and liquids for up to 6 hours and clear liquids for up to 2 hours before sedation.

REF: p. 66 a. To prevent trigeminal nerve stimulation b. To avoid necrosis of the facial skin c. To prevent vagal reflexes d. To prevent gastric insufflations

3. Why must caution be exercised when using a face mask while performing pulmonary function testing on neonates?

ANS: A

A face mask is required when testing neonates and infants. Caution must be exercised because using a face mask can cause trigeminal nerve stimulation and induce vagal reflexes that may alter the pattern of heart or respiratory rhythm.

REF: pp. 66-67 b. Minimize the amount of helium used during the test. c. Minimize oxygen concentration and increase nitrogen concentration. d. Apply petroleum jelly on the edges of the mask before applying the mask to the face.

4. The respiratory therapist places a face mask on an infant to measure FRC. What should the therapist do to minimize the presence of air leaks and improve accuracy of the test? a. Place a nose clip on the infant.

ANS: D

Applying petroleum jelly to the edges of a disposable mask is helpful for ensuring an airtight seal with no leaks on the infant's face.

REF: p. 68 a. By dividing the airway occlusion pressure by the expiratory flow b. By dividing the transpulmonary pressure by the expiratory flow c. By multiplying the expiratory flow by the pressure gradient responsible for initiating inspiration d. By multiplying the expiratory occlusion pressure by the transpulmonary pressure gradient

5. How is airway resistance calculated?

ANS: A

Airway resistance (Raw) reflects the nonelastic airway and tissue influences resisting gas flow. Raw is calculated from the ratio of airway occlusion pressure to expiratory flow. Raw is described in centimeters of water per liter per second (cm H2O/L/s).

REF: p. 68

6. Which of the following factors is the most important determinant of high airway resistance and air trapping in small infants? a. The small tidal volume b. Small diameter of the airways c. Excessive amount of mucus production d. The length of the airways

ANS: B

Raw is dependent on the radius, length, and number of airways and varies with volume, flow, and respiratory frequency. The small diameters of an infant's tracheobronchial tree result in high resistance to gas flow.

REF: p. 68

7. On the partial expiratory flow–volume loop shown here, identify the point depicting the “maximal expiratory flow at FRC.” a. A b. B c. C d. D

ANS: C

A relatively noninvasive technique to generate a partial expiratory flow volume (PEFV) curve in infants allows the measurement of expiratory flows during a forced maneuver in infants and small children. A rapid thoracic compression or "hug" is delivered to the sleeping infant's chest and abdomen with an inflatable jacket to produce a forced expiration. A pneumotachometer with a sealed face mask measures exhaled gas flow. The flow at the endexpiratory point of a normal resting tidal breath (FRC) is measured on the PEFV curve. This flow value, the maximal expiratory flow at FRC, is reported as liters per second.

REF: p. 68 a. The data are erroneous. b. The data are inconclusive. c. The patient will not clinically improve with bronchodilator administration. d. The patient has demonstrated clinically significant improvement with bronchodilator administration.

8. A pre- and postbronchodilator, partial expiratory pressure–volume maneuver was performed on a 9-month-old boy. The child’s prebronchodilator maxFRC was 67 mL/second and the postbronchodilator maxFRC was 94 mL/second. How should the therapist interpret these data?

ANS: D

PEFV studies are frequently performed before and after aerosolized bronchodilator therapy. An increase in maximal expiratory flow at FRC by at least 20% demonstrates a positive response to bronchodilator therapy. The maxFRC values presented in the question (pre-maxFRC, 67 mL/s; and post-maxFRC, 94 mL/s) indicate a 40% improvement.

REF: p. 68

9. According to the ATS-ERS acceptability criteria for an FVC maneuver performed on a 9yearold child, what is considered a satisfactory exhalation time? a. 1 second b. 2 seconds c. 3 seconds d. 6 seconds

ANS: C

Satisfactory exhalation duration is 6 seconds (3 second for children <10 years old) or a plateau in the volume–time curve.

REF: p. 70

10. A child has been diagnosed with vocal cord dysfunction. Which of the following flow–volume loops demonstrates this condition? a. Figure 5-9C b. Figure 5-9A c. Figure 5-9B d. Figure 5-8B

ANS: A

Flow limitation on the inspiratory portion of the loop is characteristic of an extrathoracic obstruction (Figure 5-9B). This is common in children with vocal cord dysfunction (VCD).

REF: p. 70

11. The respiratory therapist is looking at a flow–volume curve that displays a concave shape on the expiratory tracing. What is this change most consistent with? a. Neuromuscular disease b. Abnormal chest wall configuration c. Interstitial fibrosis d. Asthma

ANS: D

The most common chronic diseases in children asthma, cystic fibrosis, and bronchopulmonary dysplasia are obstructive. Obstructive diseases produce a concave shape or scoop to the flow–volume curve.

REF: p. 74

12. A reduction in the DLCO may indicate the presence of which of the following conditions?

I. Pulmonary fibrosis

II. Pulmonary edema

III. Hematologic disordersIV. Bronchiolitis obliterans a. I and II only b. I and III only c. I, II, and III only d. I, II, III, and IV

ANS: D

Indications for testing in the pediatric population that may produce a reduced DLCO include pulmonary fibrosis (primary disease or secondary to radiation treatment or chemotherapy), immunologic disorders (scleroderma, systemic lupus erythematosus), bronchiolitis obliterans, pulmonary edema, and hematologic disorders.

REF: p. 74

13. The therapist is reviewing a flow–volume loop obtained from a pediatric patient and observes decreased volume and normal flows. On the basis of this observation, how should the therapist interpret this finding? a. Obstructive pattern b. Restrictive pattern c. Fixed airway obstruction d. Variable extrathoracic obstruction

ANS: B

The restrictive pattern is typically characterized by preserved flows with a reduction in the volume.

REF: p. 74

14. Which of the following pulmonary function values characterize an obstructive lung defect?

I. The forced vital capacity (FVC) may remain normal.

II. The forced expiratory volume in 1 second (FEV1) is decreased.

III. The ratio of residual volume to total lung capacity (RV/TLC) may be normal.IV. The FEV1 is decreased. a. II and IV only b. I, II, and III only c. I, III, and IV only d. II, III, and IV only

ANS: C

On the basis of spirometry, an obstructive lung disorder is characterized as follows:

• FVC normal or decreased

• FEV1 decreased

• FEV1/FVC decreased

• TLC normal or increased

• RV increased

• RV/TLC increased

Table 5-2 in the textbook compares obstructive and restrictive lung diseases in terms of these spirometric measurements.

REF: p. 74 a. 0.025 mg/mL b. 0.25 mg/mL c. 2.5 mg/mL d. 10 mg/mL

15. On the basis of the bronchial provocation data presented in the following table, identify the PD20 (provocative dose that produces a 20% fall in FEV1).

ANS: D

Methacholine and mannitol are two very common inhalation challenge agents that have welldescribed protocols. In methacholine testing, a test is considered positive if the FEV1 falls more than 20% from baseline. The concentration of the challenge drug is used as a marker of the degree of bronchial reactivity and is called the PD20, the provocative dose that produces a 20% fall in FEV1. For example, a patient with highly reactive asthma may have a fall in FEV1 of 20% with a methacholine concentration of 0.25 mg/mL. A patient with mild asthma may experience a 20% fall in the FEV1 at 10 mg/mL. In mannitol testing a 15% decline in FEV1 is considered a positive response. The patient presented in this question experienced clinically significant bronchial provocation at a methacholine dose of 10 mg/mL because the FEV1 dropped 24% from baseline at that point.

REF: p. 78

16. On the basis of the data presented below, calculate the time constant.

• Tidal volume (VT), 600 mL

• Respiratory rate (RR), 12 breaths/minute

• Lung compliance (C), 0.2 L/cm H2O

• Airway resistance (Raw), 2.5 cm H2O/L/second

• Peak inspiratory pressure (PIP), 30 cm H2O

• Inspiratory time (TI), 2 seconds a. 4.5 seconds b. 3.0 seconds c. 0.5 second d. 0.1 second

ANS: C

• Expiratory time (TE), 1 second

Respiratory time constants, tau ( ), are the mathematical product of compliance and resistance expressed as seconds because all the units of pressure and volume measurement cancel out except time. A time constant is an interval over which a given change occurs, as a percentage of total change. Three time constants are required to reach 95% of inflation or exhalation. TI, or inflation time, and TE should be at least three times the respiratory time constants for optimal inspiration or expiration to occur.

REF: p. 82 a. A leak has developed in the ventilator–patient system. b. The patient’s lungs are being overinflated. c. The patient is displaying trigger dyssynchrony. d. The patient’s lungs are exhibiting increased compliance.

17. How should the therapist interpret the following pressure–volume loop obtained from a mechanically ventilated infant?

ANS: B

The pressure–volume loop demonstrates overdistention. Note the "penguin" or "bird's beak" appearance in the shape of the loops. These loops demonstrate idealized slopes (dashed lines) for change in compliance for the entire breath (C) and change in compliance in the last 20% of inspiratory pressure (C20). The C20/C ratio identifies lung overdistention.

REF: p. 83 a. To assess lung function before and after bronchodilator administration b. To help patients with asthma management at home c. To evaluate the strength of respiratory muscles d. To assist in performing bronchial hygiene techniques

18. What is the clinical purpose for measuring the maximal inspiratory pressure (MIP)?

ANS: C

MIP is an important measure to help differentiate weakness from other causes of restrictive lung disease. It can be an important differentiating point for children and young adults with various neuromuscular diseases. These patients usually have a combination of scoliosis and muscle weakness, both of which might contribute to reduced lung volumes. Measuring MIP helps in determining how much reduction might be caused by weakness. Because many neuromuscular diseases are progressive, MIP helps to document this progression. MIP may also indicate the patient's physical ability to take a deep breath and is often measured when weaning a patient from mechanical ventilation is being considered.

REF: p. 84