Andrew C. McKown

Randomized Trial of Apneic Oxygenation during Endotracheal Intubation of the Critically Ill

RATIONALE Hypoxemia is common during endotracheal intubation of critically ill patients and may predispose to cardiac arrest and death. Administration of supplemental oxygen during laryngoscopy (apneic oxygenation) may prevent hypoxemia. OBJECTIVES To determine if apneic oxygenation increases the lowest arterial oxygen saturation experienced by patients undergoing endotracheal intubation in the intensive care unit. METHODS This was a randomized, open-label, pragmatic trial in which 150 adults undergoing endotracheal intubation in a medical intensive care unit were randomized to receive 15 L/min of 100% oxygen via high-flow nasal cannula during laryngoscopy (apneic oxygenation) or no supplemental oxygen during laryngoscopy (usual care). The primary outcome was lowest arterial oxygen saturation between induction and 2 minutes after completion of endotracheal intubation. MEASUREMENTS AND MAIN RESULTS Median lowest arterial oxygen saturation was 92% with apneic oxygenation versus 90% with usual care (95% confidence interval for the difference, -1.6 to 7.4%; P = 0.16). There was no difference between apneic oxygenation and usual care in incidence of oxygen saturation less than 90% (44.7 vs. 47.2%; P = 0.87), oxygen saturation less than 80% (15.8 vs. 25.0%; P = 0.22), or decrease in oxygen saturation greater than 3% (53.9 vs. 55.6%; P = 0.87). Duration of mechanical ventilation, intensive care unit length of stay, and in-hospital mortality were similar between study groups. CONCLUSIONS Apneic oxygenation does not seem to increase lowest arterial oxygen saturation during endotracheal intubation of critically ill patients compared with usual care. These findings do not support routine use of apneic oxygenation during endotracheal intubation of critically ill adults. Clinical trial registered with www.clinicaltrials.gov (NCT 02051816).

A Multicenter, Randomized Trial of Ramped Position vs Sniffing Position During Endotracheal Intubation of Critically Ill Adults

BACKGROUND: Hypoxemia is the most common complication during endotracheal intubation of critically ill adults. Intubation in the ramped position has been hypothesized to prevent hypoxemia by increasing functional residual capacity and decreasing the duration of intubation, but has never been studied outside of the operating room. METHODS: Multicenter, randomized trial comparing the ramped position (head of the bed elevated to 25°) with the sniffing position (torso supine, neck flexed, and head extended) among 260 adults undergoing endotracheal intubation by pulmonary and critical care medicine fellows in four ICUs between July 22, 2015, and July 19, 2016. The primary outcome was lowest arterial oxygen saturation between induction and 2 minutes after intubation. Secondary outcomes included Cormack‐Lehane grade of glottic view, difficulty of intubation, and number of laryngoscopy attempts. RESULTS: The median lowest arterial oxygen saturation was 93% (interquartile range [IQR], 84%‐99%) with the ramped position vs 92% (IQR, 79%‐98%) with the sniffing position (P = .27). The ramped position appeared to increase the incidence of grade III or IV view (25.4% vs 11.5%, P = .01), increase the incidence of difficult intubation (12.3% vs 4.6%, P = .04), and decrease the rate of intubation on the first attempt (76.2% vs 85.4%, P = .02), respectively. CONCLUSIONS: In this multicenter trial, the ramped position did not improve oxygenation during endotracheal intubation of critically ill adults compared with the sniffing position. The ramped position may worsen glottic view and increase the number of laryngoscopy attempts required for successful intubation. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT02497729; URL: www.clinicaltrials.gov

A Multicenter Randomized Trial of a Checklist for Endotracheal Intubation of Critically Ill Adults

BACKGROUND: Hypoxemia and hypotension are common complications during endotracheal intubation of critically ill adults. Verbal performance of a written, preintubation checklist may prevent these complications. We compared a written, verbally performed, preintubation checklist with usual care regarding lowest arterial oxygen saturation or lowest systolic BP experienced by critically ill adults undergoing endotracheal intubation. METHODS: A multicenter trial in which 262 adults undergoing endotracheal intubation were randomized to a written, verbally performed, preintubation checklist (checklist) or no preintubation checklist (usual care). The coprimary outcomes were lowest arterial oxygen saturation and lowest systolic BP between the time of procedural medication administration and 2 min after endotracheal intubation. RESULTS: The median lowest arterial oxygen saturation was 92% (interquartile range [IQR], 79‐98) in the checklist group vs 93% (IQR, 84‐100) with usual care (P = .34). The median lowest systolic BP was 112 mm Hg (IQR, 94‐133) in the checklist group vs 108 mm Hg (IQR, 90‐132) in the usual care group (P = .61). There was no difference between the checklist and usual care in procedure duration (120 vs 118 s; P = .49), number of laryngoscopy attempts (one vs one attempt; P = .42), or severe life‐threatening procedural complications (40.8% vs 32.6%; P = .20). CONCLUSIONS: The verbal performance of a written, preprocedure checklist does not increase the lowest arterial oxygen saturation or lowest systolic BP during endotracheal intubation of critically ill adults compared with usual care. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT02497729; URL: www.clinicaltrials.gov.

Preadmission Oral Corticosteroids Are Associated With Reduced Risk of Acute Respiratory Distress Syndrome in Critically Ill Adults With Sepsis

Objectives: To determine the association between preadmission oral corticosteroid receipt and the development of acute respiratory distress syndrome in critically ill patients with sepsis. Design: Retrospective observational study. Setting: Medical, surgical, trauma, and cardiovascular ICUs of an academic medical center. Patients: A total of 1,080 critically ill patients with sepsis. Interventions: None. Measurements and Main Results: The unadjusted occurrence rate of acute respiratory distress syndrome within 96 hours of ICU admission was 35% among patients who had received oral corticosteroids compared with 42% among those who had not (p = 0.107). In a multivariable analysis controlling for prespecified confounders, preadmission oral corticosteroids were associated with a lower incidence of acute respiratory distress syndrome in the 96 hours after ICU admission (odds ratio, 0.53; 95% CI, 0.33–0.84; p = 0.008), a finding that persisted in multiple sensitivity analyses. The median daily dose of oral corticosteroids among the 165 patients receiving oral corticosteroids, in prednisone equivalents, was 10 mg (interquartile range, 5–30 mg). Higher doses of preadmission oral corticosteroids were associated with a lower incidence of acute respiratory distress syndrome (odds ratio for 30 mg of prednisone compared with 5 mg 0.53; 95% CI, 0.32–0.86). In multivariable analyses, preadmission oral corticosteroids were not associated with in-hospital mortality (odds ratio, 1.41; 95% CI, 0.87–2.28; p = 0.164), ICU length of stay (odds ratio, 0.90; 95% CI, 0.63–1.30; p = 0.585), or ventilator-free days (odds ratio, 1.06; 95% CI, 0.71–1.57; p = 0.783). Conclusions: Among ICU patients with sepsis, preadmission oral corticosteroids were independently associated with a lower incidence of early acute respiratory distress syndrome.

Lung Recruitment and Positive End-Expiratory Pressure Titration in Patients With Acute Respiratory Distress Syndrome

Author Affiliations: Corporal Michael J. Crescenz Philadelphia Veterans Affairs Medical Center, Philadelphia, Pennsylvania (Navathe); Department of Medicine, University of Washington School of Medicine, Seattle (Liao); Department of Medical Ethics and Health Policy, University of Pennsylvania Perelman School of Medicine, Philadelphia (Shah, Lyon, Emanuel); Department of General Internal Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia (Chatterjee); Leonard Davis Institute of Health Economics at the University of Pennsylvania, Philadelphia (Polsky).

Best PEEP trials are dependent on tidal volume

Determining the optimal positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome remains an area of active investigation. Most trials individualizing PEEP optimize one physiologic parameter (e.g., driving pressure) by titrating PEEP while holding other ventilator settings constant. Optimal PEEP, however, may depend on the tidal volume, and changing the tidal volume with which a best PEEP trial is performed may lead to different best PEEP settings in the same patient.Trial registrationClinicalTrials.gov, NCT02871102. Registered on 12 August 2016.

Risk Factors for and Prediction of Hypoxemia during Tracheal Intubation of Critically Ill Adults

Rationale: Hypoxemia is a common complication during tracheal intubation of critically ill adults and is a frequently used endpoint in airway management research. Identifying patients likely to experience low oxygen saturations during tracheal intubation may be useful for clinical practice and clinical trials. Objectives: To identify risk factors for lower oxygen saturations and severe hypoxemia during tracheal intubation of critically ill adults and develop prediction models for lowest oxygen saturation and hypoxemia. Methods: Using data on 433 intubations from two randomized trials, we developed linear and logistic regression models to identify preprocedural risk factors for lower arterial oxygen saturations and severe hypoxemia between induction and 2 minutes after intubation. Penalized regression was used to develop prediction models for lowest oxygen saturation after induction and severe hypoxemia. A simplified six‐point score was derived to predict severe hypoxemia. Results: Among the 433 intubations, 426 had complete data and were included in the model. The mean (standard deviation) lowest oxygen saturation was 88% (14%); median (interquartile range) was 93% (83‐98%). Independent predictors of severe hypoxemia included hypoxemic respiratory failure as the indication for intubation (odds ratio [OR], 2.70; 95% confidence interval [CI], 1.58‐4.60), lower oxygen saturation at induction (OR, 0.92 per 1% increase; 95% CI, 0.89‐0.96 per 1% increase), younger age (OR, 0.97 per 1‐year increase; 95% CI, 0.95‐0.99 per 1‐year increase), higher body mass index (OR, 1.03 per 1 kg/m2; 95% CI, 1.00‐1.06 per 1 kg/m2), race (OR, 4.58 for white vs. black; 95% CI, 1.97‐10.67; OR, 4.47 for other vs. black; 95% CI, 1.19‐16.84), and operator with fewer than 100 prior intubations (OR, 2.83; 95% CI, 1.37‐5.85). A six‐point score using the identified risk factors predicted severe hypoxemia with an area under the receiver operating curve of 0.714 (95% CI, 0.653 to 0.778). Conclusions: Lowest oxygen saturation and severe hypoxemia during tracheal intubation in the intensive care unit can be accurately predicted using routinely available preprocedure clinical data, with saturation at induction and hypoxemic respiratory failure being the strongest predictors. A simple bedside score may identify patients at risk for hypoxemia during intubation to help target preventative interventions and facilitate enrichment in clinical trials.

External Validity of Electronic Sniffers for Automated Recognition of Acute Respiratory Distress Syndrome

Introduction: Automated electronic sniffers may be useful for early detection of acute respiratory distress syndrome (ARDS) for institution of treatment or clinical trial screening. Methods: In a prospective cohort of 2929 critically ill patients, we retrospectively applied published sniffer algorithms for automated detection of acute lung injury to assess their utility in diagnosis of ARDS in the first 4 ICU days. Radiographic full-text reports were searched for “edema” OR (“bilateral” AND “infiltrate”) and a more detailed algorithm for descriptions consistent with ARDS. Patients were flagged as possible ARDS if a radiograph met search criteria and had a PaO2/FiO2 or SpO2/FiO2 of 300 or 315, respectively. Test characteristics of the electronic sniffers and clinical suspicion of ARDS were compared to a gold standard of 2-physician adjudicated ARDS. Results: Thirty percent of 2841 patients included in the analysis had gold standard diagnosis of ARDS. The simpler algorithm had sensitivity for ARDS of 78.9%, specificity of 52%, positive predictive value (PPV) of 41%, and negative predictive value (NPV) of 85.3% over the 4-day study period. The more detailed algorithm had sensitivity of 88.2%, specificity of 55.4%, PPV of 45.6%, and NPV of 91.7%. Both algorithms were more sensitive but less specific than clinician suspicion, which had sensitivity of 40.7%, specificity of 94.8%, PPV of 78.2%, and NPV of 77.7%. Conclusions: Published electronic sniffer algorithms for ARDS may be useful automated screening tools for ARDS and improve on clinical recognition, but they are limited to screening rather than diagnosis because their specificity is poor.

Quantification of lung recruitment by respiratory mechanics and CT imaging: what are the clinical implications?

Acute respiratory distress syndrome (ARDS) is characterized by increased elastance of the lung and respiratory system (1). Depending on the precipitating factor, pulmonary vs. extrapulmonary, the distribution of pathologic findings and altered respiratory mechanics in the lung is heterogeneous (2). Portions of the lung can be collapsed and/or fluid-filled while others are well-aerated. In order to facilitate gas exchange, recruitment maneuvers are sometimes employed in patients with ARDS (3). These can be performed with a constant high pressure inspiratory hold for 30–40 seconds (4,5) or via stepwise recruitment by increasing the positive end-expiratory pressure (PEEP) (6), typically followed by application of PEEP at a higher level than the previous baseline to maintain aeration of the recruited lung units (7). Recruitment maneuvers have been proposed as useful tools in managing patients with ARDS in order to add previously non-participatory lung units to gas exchange as well as to assess disease severity. The potential effectiveness of recruitment maneuvers in incorporating previously collapsed lung units into gas exchange or in improving the distension of previously poorly aerated pulmonary units differs from patient to patient consequent to the variability in etiology of the lung injury and the heterogeneity of lung parenchyma (8).