Test yourself: COPD


Case 1: Increasing dyspnea

A 63-year-old woman is evaluated in the emergency department for a three-day history of increasing dyspnea. She has severe COPD requiring long-term oxygen therapy. Her baseline arterial PCO2 is 48 mm Hg. She has had increasing cough productive of yellowish phlegm but is expectorating without difficulty. She has no chest pain.

On physical examination, she is in moderate respiratory distress and using accessory muscles to breathe, but she is alert and cooperative. Her blood pressure is 144/82 mm Hg, her pulse rate is 122 beats/min and her respiration rate is 28 breaths/min. There is no jugular venous distention. Examination of the lungs reveals bilateral rhonchi and a prolonged expiratory phase. Heart sounds are distant, and the abdomen is soft without masses. She is not cyanotic (using oxygen at 4 L/min by nasal cannula), and she has 1+ pedal edema.

Laboratory results show a hemoglobin level of 13 g/dL and a serum bicarbonate level of 31 mEq/L. Arterial blood gases show a PO2 of 64 mm Hg, PCO2 of 56 mm Hg and pH of 7.28. Electrocardiography shows multifocal atrial tachycardia without acute ischemic changes. Respiratory treatments and intravenous corticosteroids and antibiotics are started.

In addition to the supplemental oxygen and intravenous corticosteroids and antibiotics, which of the following would be most appropriate in this patient?

A. Close observation
B. Continuous positive airway pressure
C. Prompt intubation
D. Noninvasive positive pressure ventilation

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Case 2: Worsening carbon dioxide retention

A 74-year-old man with severe COPD (FEV1 0.66 L) and chronic carbon dioxide retention (baseline arterial PCO2 55 mm Hg) who is receiving long-term oxygen therapy is evaluated in the emergency department for an exacerbation of his disease and worsening carbon dioxide retention (PO2 112 mm Hg, PCO2 279 mm Hg, and pH 7.12 on oxygen 5 L/min by nasal cannula). On examination, the patient is tachypneic (respiration rate 35 breaths/min), his blood pressure is 135/78 mm Hg, and he can be roused only by noxious physical stimuli.

Noninvasive ventilation by an oronasal mask is begun at inspiratory pressure 16 cm H2O and expiratory pressure 5 cm H2O with an oxygen flow rate of 6 L/min via the ventilator circuit. Two hours later, the patient has awakened but has become agitated. His respiration rate is 35 breaths/min, and his blood pressure is 190/110 mm Hg. He frequently removes the mask despite light sedation and hand restraints. He is using accessory muscles of breathing vigorously. Repeat arterial blood gases show a PO2 of 112 mm Hg, PCO2 of 74, and pH of 7.16.

Which of the following is the most appropriate next step in the management of this patient?

A. Promptly intubate
B. Increase the inspiratory pressure, give more sedation and reduce the FiO2
C. Stop noninvasive ventilation and start oxygen by high-flow mask at an FiO2 of 0.35
D. Continue noninvasive ventilation

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Case 3: Respiratory arrest

A 78-year-old man is admitted to the intensive care unit from the emergency department where he had presented with a respiratory arrest and was promptly intubated. The patient has a long history of smoking and of severe COPD and is on long-term oxygen therapy at home. Previous measurement of arterial blood gases on 2 L oxygen during a stable state revealed a PO2 of 92 mm Hg, PCO2 of 58 mm Hg and pH of 7.45.

Physical examination is notable for a barrel chest and fine expiratory wheezes. Heart sounds are barely audible. Arterial blood gases just before intubation were PO2 220 mm Hg, PCO2 122 mm Hg, and pH 7.04 while he was receiving 100% oxygen. In the emergency department, initial ventilator settings were assist/control mode with a rate of 20/min, tidal volume of 600 mL, PEEP of 5 cm H2O and FiO2 of 50%. Chest radiograph shows hyperinflation, extensive bullous emphysema, and a right lower-lobe infiltrate.

On arrival to the intensive care unit, he is hypotensive with a systolic pressure of 80 mm Hg, unresponsive to an initial fluid bolus. A pulmonary artery catheter is inserted; right atrial pressure is 20 cm H2O, pulmonary artery pressure is 66/25 mm Hg, pulmonary capillary wedge pressure is 21 mm Hg and cardiac index is 1.8 L/min/m2. Electrocardiography shows a rate of 122/min, sinus rhythm with multiple premature atrial beats and nonspecific STT changes. During an accidental disconnection from the ventilator, the patient's blood pressure and wedge pressure normalize but deteriorate when he is reconnected.

Which of the following is the most appropriate next step in the management of this patient?

A. Administer more fluids
B. Start dobutamine therapy
C. Obtain a repeat STAT portable chest radiograph
D. Lower the respiration rate and tidal volume

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Case 4: Shortness of breath and ankle swelling

A 65-year-old man with severe COPD is evaluated for worsening shortness of breath and ankle swelling. He uses a long-acting β-agonist in combination with an inhaled corticosteroid on a regular basis.

The patient's weight and vital signs are normal. There is neck vein distention at 30 degrees. Cardiac examination shows a regular rate and rhythm without murmur. The pulmonic closure sound is accentuated. An S3 gallop was noted that varied with respiration. Examination of the lungs reveals faint wheezes bilaterally. The abdomen is nonobese without organomegaly. Examination of the legs and ankles reveals 1+ edema. Arterial blood gases with the patient breathing room air show pH 7.40, PO2 65 mm Hg and Pco2 44 mm Hg. The hematocrit is 52%.

Which of the following is the most appropriate next step in the management of this patient?

A. Nocturnal mechanical ventilation
B. Phlebotomy
C. Nocturnal pulse oximetry
D. Ipratropium bromide therapy

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Case 5: Airplane travel with severe COPD

A 60-year-old man with severe COPD asks your opinion on the advisability of flying from New York to San Francisco (simulated altitude 8,000 ft) to attend his daughter's wedding. He has dyspnea on exertion but no comorbid diseases; he has not had any recent exacerbations of COPD. Examination of the lungs shows decreased breath sounds bilaterally without wheezes or crackles. The neck veins are not distended.

Cardiac examination shows a regular rhythm, with no murmur or gallop. There is no peripheral edema. Pulmonary function tests show an FEV1 of 1.0 L (33% of predicted), and the FEV1/FVC ratio is 45%. Measurement of arterial blood gases with the patient breathing room air in New York shows PO2 65 mm Hg, PCO2 40 mm Hg and pH 7.40.

Which of the following is the most appropriate next step in the management of this patient?

A. Advise against the flight
B. Schedule a hypoxic inhalation test to simulate an altitude of 8,000 ft
C. Recommend flying with supplemental oxygen at 2 to 3 L/min
D. Calculate the estimated PaO2 at 8,000 ft using a regression equation
E. Determine the airline's policy on the use of supplemental oxygen

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Answers and commentary

Case 1

Correct answer: D. Noninvasive positive pressure ventilation.

This patient is the ideal candidate for noninvasive positive pressure ventilation (NPPV). Numerous controlled trials as well as meta-analyses have demonstrated significant benefits of NPPV compared to standard therapy in such patients, including more rapid improvements in respiratory and heart rate, gas exchange, avoidance of intubation, reduced rates of morbidity and mortality and shorter hospital lengths of stay. The patient has the usual features of patients benefiting from NPPV in the studies, including moderate respiratory distress, use of accessory muscles, tachypnea and acute on chronic carbon dioxide retention. She also has none of the contraindications, such as excessive secretions, uncooperativeness or acute ischemic changes on electrocardiography (the multifocal atrial tachycardia is not a problem as long as the patient is hemodynamically stable).

Close observation is not the most appropriate next step because, although she has roughly a 50% of responding to medical therapy, waiting to see if she worsens increases the likelihood of NPPV failure. CPAP alone has been shown to reduce work of breathing by counterbalancing auto-PEEP in patients with COPD, but is less effective at doing so than the combination of pressure support plus positive end-expiratory pressure. Intubation should be avoided in patients with COPD because of the increased morbidity and mortality associated with its use.

Key points

  • Noninvasive positive pressure ventilation in selected patients with moderate respiratory distress has been shown to improve heart and respiration rates and gas exchange and to reduce morbidity and mortality rates, the need for intubation and the length of hospital stay in patients with severe COPD.
  • Contraindications to noninvasive positive pressure ventilation in patients with moderate respiratory distress include excessive secretions, uncooperativeness and acute ischemic changes on electrocardiography.</div>

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Case 2

Correct answer: A. Promptly intubate.

Although the patient's PCO2 has declined a bit, he is doing poorly on noninvasive ventilation. Recent studies indicate that delaying needed intubation can add to patient morbidity and mortality. One study showed an increase in intensive care unit mortality when patients at risk for postextubation respiratory failure were treated with noninvasive ventilation as compared to conventional therapy, including intubation. A major difference in the management between the two groups was that re-intubations were delayed by almost 10 hours in the noninvasive ventilation group compared with the conventional therapy group, and this was thought to have contributed to the excess mortality.

Another study showed that the combination of a respiration rate of more than 35 breaths/min, an APACHE score greater than 29, a pH less than 7.25 and a Glasgow Coma Score less than 11 predicted a noninvasive ventilation failure rate of greater than 80%. However, if these abnormalities persisted at the two-hour time point, the likelihood of failure was virtually 100%. Therefore, because this patient's pH remained below 7.25 at the two-hour time point and there were a number of other indicators of difficulty, including secretions and agitation unresponsive to sedation, prompt intubation would be the prudent course to avoid a respiratory arrest that would increase the likelihood of morbidity and/or mortality. The other options, such as making adjustments in the settings or oxygen supplementation (presumably to stimulate hypoxic drive), are very unlikely to avoid the need for intubation considering all the poor prognostic indicators. Taking the patient off noninvasive ventilation could precipitate a respiratory arrest.

Key point

  • Predictors of failure of noninvasive ventilation in patients with an exacerbation of COPD include a respiration rate above 35 breaths/min, an APACHE score greater than 29, a pH less than 7.25 and a Glasgow Coma Score less than 11.

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Case 3

Correct answer: D. Lower the respiration rate and tidal volume.

This situation occurs in patients with severe COPD and respiratory failure as a result of overzealous attempts to correct severe carbon dioxide retention. The tidal volume and rate selected in the emergency department are inappropriately high and can lead to two serious adverse consequences. One is excessively rapid reduction in PaCO2, potentially causing severe alkalemia. The other, which is what occurred in this case, is the induction of dynamic hyperinflation leading to a severe elevation of intrinsic positive end-expiratory pressure (auto-PEEP). By increasing the intrathoracic pressure excessively and impeding venous return, it produced a hemodynamic picture resembling cardiogenic shock. The high intrathoracic pressures are transmitted to the elastic vascular structures, causing an artifactual overestimation of filling pressures. Disconnection of the patient from the ventilator permits release of the pressure and reversal of the adverse hemodynamic consequences. Cardiac index and systemic blood pressure should rapidly rise as intrathoracic, wedge and right atrial pressures drop. Infusing more fluids would not correct the fundamental problem: the high intrathoracic pressure. Dobutamine will not help because the limitation in cardiac output is not inotropic—it is inadequate preload. Lowering the respiratory rate and tidal volume provides more time for exhalation of less air, reducing the auto-PEEP and intrathoracic pressure, increasing venous return and alleviating the hemodynamic abnormalities.

Key point

  • In a patient with severe COPD and respiratory failure with severe carbon dioxide retention, inappropriately high rate and tidal volume of mechanical ventilation can cause 1) excessively rapid reduction in PaCO2, potentially causing severe alkalemia and 2) the induction of dynamic hyperinflation leading to a severe elevation of intrinsic positive end-expiratory pressure (auto-PEEP).

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Case 4

Correct answer: C. Nocturnal pulse oximetry.

This patient's physical findings suggest pulmonary hypertension and cor pulmonale. Even though his PO2 is greater than 60 mm Hg while he is awake, he may have nocturnal oxygen desaturation that is responsible for pulmonary hypertension. Pulse oximetry could document the presence of nocturnal hypoxemia. A full polysomnography is useful if sleep staging is required to document rapid eye movement (REM) sleep-related oxygen desaturation. Supplemental oxygen would be appropriate if marked nocturnal hypoxemia is documented. Nocturnal mechanical ventilation would not be indicated unless nocturnal hypoventilation is present. A phlebotomy is not likely to improve symptoms at this modest level of polycythemia. Adding ipratropium bromide is unlikely to reverse the nocturnal hypoxemia associated with COPD.

Key point

  • Nocturnal pulse oximetry can document nocturnal hypoxemia causing pulmonary hypertension in patients with obstructive lung disease.

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Case 5

Correct answer: D. Calculate the estimated PaO2 at 8,000 ft using a regression equation.

Preflight assessment of patients with COPD is useful to determine the need for in-flight oxygen supplementation because commercial airlines are required to maintain cabin pressures only equivalent to altitudes of 8,000 feet or less, and the corresponding lower alveolar Po2 (PaO2) may cause a fall in PaO2. Since patients with COPD may experience a fall in PaO2 of as much as 25 to 30 mm Hg due to the decreased PaO2, preflight assessment is useful to determine the need for in-flight oxygen supplementation with the goal of maintaining PaO2 either at 50 mm Hg or greater or, in high-risk patients, at the PaO2 with which the patient is clinically stable at sea level.

PaO2 at altitude can be estimated with published regression equations, which can be used to estimate whether the PaO2 at 8,000 feet will fall below 50 mm Hg and therefore whether additional evaluation with the hypoxic inhalation test is needed. One such equation is as follows:

Estimated PaO2 at 8,000 feet = (0.238 × PaO2 at sea level) + (20.098 × FEV1/FVC) + 22.258.

Key point

  • Patients with COPD may experience a fall in PaO2 of as much as 25 to 30 mm Hg during air travel, and preflight assessment is useful to determine the need for in-flight oxygen supplementation with the goal of maintaining PaO2 either at 50 mm Hg or greater or, in high-risk patients, at the PaO2 with which the patient is clinically stable at sea level.