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Update your knowledge with MKSAP 14 Q&A


MKSAP 14 will help you update your knowledge in the field of internal medicine for improved patient care, support your clinical decisions in practice, and assess your medical knowledge with 1,200 multiple-choice questions. For more information on how to order MKSAP 14 click here


A 74-year-old man with severe chronic obstructive pulmonary disease (FEV1 0.66 L), long-term oxygen therapy, and chronic carbon dioxide retention (baseline PaCO2 55 mm Hg) is evaluated in the emergency department for an exacerbation of his disease and worsening carbon dioxide retention (PO2 112 mm Hg, PCO2 79 mm Hg, and pH 7.12 on oxygen 5 L/min by nasal cannula). On presentation, he is tachypneic (respiration rate 35/min), his blood pressure is 135/78 mm Hg, and he is arousable only to 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, he has awakened but has become agitated. His respiration rate is 35/min and 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 place on a high-flow mask at an FiO2 of 0.35
D. Continue noninvasive ventilation

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Answer: A, Promptly intubate

Objective: Recognize poor prognostic indicators in COPD patients on noninvasive ventilation

Critique: Although the patient’s PaCO2 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. The study by Esteban et al 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 by Confalonari et al showed that the combination of a respiration rate > 35/min, APACHE score > 29, pH < 7.25, and Glasgow Coma Score < 11 predicted a noninvasive ventilation failure rate of greater than 80%. However, if these abnormalities persisted at the 2-h time point, the likelihood of failure was virtually 100%. Therefore, because this patient’s pH remained below 7.25 at the 2-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, like 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 > 35/min, APACHE score > 29, pH < 7.25, and Glasgow coma score < 11.


Esteban A, Frutos-Vivar F, Ferguson ND, Arabi Y, Apezteguía C, González M, et al. Noninvasive positive-pressure ventilation for respiratory failure after extubation. N Engl J Med. 2004;350:2452-60. [PMID: 15190137]
Confalonieri M, Garuti G, Cattaruzza MS, Osborn JF, Antonelli M, Conti G, et al. A chart of failure risk for noninvasive ventilation in patients with COPD exacerbation. Eur Respir J. 2005;25:348-55. [PMID: 15684302]

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