Gotta read VI


A systematic review and meta-analysis evaluating the role of high-flow nasal cannula in critically ill patients with or at risk for respiratory failure [1] was published. Nine studies included, but unfortunately, the recent study by Hernandez and colleagues [2] was not (will be discussed here soon). And although there is a hype around HFNC, the results were not encouraging for its defenders. HFNC did not reduce the incidence of mechanical ventilation, neither compared with noninvasive ventilation (OR 0.83, 95% CI 0.57–1.20, P=0.31), nor standard oxygen therapy (OR 0.49, 95% CI 0.22–1.08, P =.17). Secondary outcomes found no difference in ICU mortality when comparing HFNC with the other groups. Except for increased patient’s comfort, I cannot see an advantage of using it, even after the Hernandez trial. In a few weeks we’ll show why.


A phase II study published on Chest (IASIS Trial) [3] concluded that adjunctive aerosol therapy with amikacin fosfomycin was not better than IV antibiotics for the treatment of ventilator associated pneumonia (VAP) caused by gram-negative bacterias. Small trial with a primary endpoint of change from baseline in the Clinical Pulmonary Infection Score (CPIS). However, the new Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society [4], recommend (weak recommendation, very low quality evidence) the use of inhaled aminoglycosides or polymyxins in addition to IV antibiotics for the treatment of VAP due to gram-negative bacilli that are only susceptible to those antibiotics.


Our predictions of difficult mask ventilation sucks. How many times you thought: “Well, this is gonna be easy”, and BOOM! You’re sweating like a pig, praying to the closest god available for an easy laryngoscopy! A Dannish group published a study [5] comparing eleven risk factors for difficult airway management (facial beard; snoring; history of sleep apnoea; neck radiation changes; mouth opening; thyromental distance; modified Mallampati classification; neck movement; ability to extend lower jaw; weight; and history of difficult intubation) with existing standards for pre-operative airway assessment. Ninety-four thousand patients were evaluated. There was no difference in the incidence of unpredicted difficult mask ventilation between intervention (0.91%) and control (0.88%) groups. The incidence of falsely predicted difficult was higher in the intervention group compared to control, respectively 0.64% vs 0.35%. However, in my opinion, the most significant finding was that 86.3% (intervention) and 91.2% (control) of all difficult mask ventilations were not predicted. Man, that’s huge! The negative likelihood ratio of both tests is 0.9! Fortunately, the incidence of difficult mask ventilation is around 1%. My advise: expect the best, prepare for the worst.


The first time I really paid attention to mediation analysis was after the publication of the Driving Pressure study [6], by Amato and colleagues in NEJM. In this trial they used mediation analysis to isolate the effects of changes in driving pressure resulting from ventilator settings while minimizing confounding. A group of Chinese guys published an article discussing causal mediation analysis in the context of clinical research [7]. Worth the reading. Also, if you wanna a more dissected view of mediation analysis, a good review [8] was published few years ago.


You can leave fifth grade, but fifth grade never leaves you. Some Greek dudes studied the association between somatometric parameters and genitalia size in normal men under 40 y/o. The only somatometric parameter associated with the “dimensions of the flaccid, maximally stretched, penis” was the index finger length. Unfortunately the Pearson correlation coefficient was only 0.339, P=0.014. I wish I had this scientific based information when I was in fifth grade. But I think it will still be useful next time someone asks for 6.0 gloves!


1. Nedel WL, Deutschendorf C, Moraes Rodrigues Filho E. High-Flow Nasal Cannula in Critically Ill Subjects With or at Risk for Respiratory Failure: A Systematic Review and Meta-Analysis. Respir Care. 2016.2. Hernández G, Vaquero C, Colinas L, et al.

2. Effect of Postextubation High-Flow Nasal Cannula vs Noninvasive Ventilation on Reintubation and Postextubation Respiratory Failure in High-Risk Patients: A Randomized Clinical Trial. JAMA. 2016;316(15):1565-1574.

3. Kollef MH, Ricard JD, Roux D, et al. A randomized trial of the amikacin fosfomycin inhalation system for the adjunctive therapy of Gram-negative ventilator-associated pneumonia: IASIS Trial. Chest. 2016.

4. Kalil AC, Metersky ML, Klompas M, et al. Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016;63(5):e61-e111.

5. Nørskov AK, Wetterslev J, Rosenstock CV, et al. Prediction of difficult mask ventilation using a systematic assessment of risk factors vs. existing practice – a cluster randomised clinical trial in 94,006 patients. Anaesthesia. 2016.

6. Amato MB, Meade MO, Slutsky AS, et al. Driving pressure and survival in the acute respiratory distress syndrome. N Engl J Med. 2015;372(8):747-755.

7. Zhongheng Z, Cheng Z, Chanmin K, et al. Causal Mediation Analysis in the Context of Clinical Research. Annals of Translational Medicine. 2016

8. MacKinnon DP, Fairchild AJ, Fritz MS. Mediation analysis. Annu Rev Psychol. 2007;58:593-614.

9. Spyropoulos E, Borousas D, Mavrikos S, Dellis A, Bourounis M, Athanasiadis S. Size of external genital organs and somatometric parameters among physically normal men younger than 40 years old. Urology. 2002;60(3):485-489; discussion 490-481.


Photo Credit
Gregorio J. Caraballo

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