After reading the article by Driver and Reardon in the January 2017 edition of Annals , I have several questions for the authors, as well as a few comments from personal experience.

First, what was the FiO ₂ when the patient began receiving bilevel positive airway pressure? According to the arterial blood gas, this patient appeared to be a long-term carbon dioxide retainer with a baseline PCO ₂ of approximately 50 to 55 mm Hg. The more accurate description of her condition would have then been an acute worsening of her chronic respiratory acidosis instead of “acute respiratory acidosis.” They were delivering high-flow oxygen by nonrebreather mask before the noninvasive positive pressure ventilation, so although the temporal association may suggest a medication effect causing apnea, it may have been the application of high FiO ₂ again with bilevel positive airway pressure. Second, the definition of apnea by medical literature is a minimum of 20 seconds (the default apnea alarm on many models of mechanical ventilators) or less if resulting in symptoms such as bradycardia or cyanosis. The authors describe 15 seconds of apnea before their decision to move from delayed sequence intubation to rapid sequence intubation, but did any clinical deterioration, such as desaturation or bradycardia, occur?

During the last 3 years, I have used ketamine frequently in the ICU to accomplish percutaneous endoscopic gastrostomy tube placement after ischemic and hemorrhagic strokes in patients who have been successfully extubated but do not regain the ability to swallow. I typically use a total of 1 to 1.5 mg/kg intravenously to complete the 30- to 40-minute procedure, and my patients have not had any episodes of apnea. I have also used a ketamine infusion during several days on 2 different occasions in nonintubated patients with nonconvulsive status epilepticus whose living will or family requested no intubation or mechanical ventilation, again without any episodes of apnea. I would question the claim that “It is probable that critically ill patients have higher rates of apnea with ketamine administration.”