CCP Podcast 055: Papers of the Month - Critical Care Practitioner

CCP Podcast 055: Papers of the Month

 November 11

by Jonathan Downham


In this podcast episode, Gavin Denton and I look at three recent papers, breaking them down to try to help us and you understand some of their conclusions and how they reached them.

Our notes can be found below.

Video laryngoscopy vs direct laryngoscopy on successful first pass orotracheal intubation amongst ICU patients. JAMA Jan 2017


Lascarrou et al

Clinical Question

Routine use of video laryngoscopy for orotracheal intubation of patients in ICU increases the frequency of successful first pass intubation compared with the use of the Macintosh direct laryngoscope.


Non blinded, multi centre, open label, 2 parallel group RCT


7 ICUs in France


Inclusion criteria: ICU admission and need for intubation to allow mechanical ventilation.

Exclusion criteria: 1. Contraindications to intubation e.g. unstable spinal lesion. 2. Insufficient time to include and randomise. 3. < 18 yrs.  4. Pregnant or breastfeeding…..and others…..


Using McGrath MAC video laryngoscope- this device was chosen because intubation technique is similar to Macintosh, a previous study suggests benefits for ICU intubation, the small size of the device enabled bedside use and cost was relatively low.

  •         Pre ox with BVM at 15l min for at least 3 minutes, or vent in non-invasive mode providing 100% oxygen or HFNC at 60l/min with 100% for 3 minutes.
  •         Etomidate or ketamine/sux or roc.
  •         Tube position confirmed with capnography over 4 or more breaths.
  •         Sellick at discretion of clinician.
  •         If first pass failure then following technique chosen according to French guidelines.


Same as above but using Macintosh laryngoscope.


Primary outcome: Proportion of patients with successful first pass orotracheal intubations which was defined based on a normal appearing waveform of the partial pressure of end tidal exhaled carbon dioxide curve over 4 or more breathing cycles.

Secondary outcomes:

  • proportion of patients with successful orotracheal intubation at any attempt.
  • total time to successful orotracheal intubation
  • grade of glottis visibility.
  • percentage of glottic opening score
  • proportion of patients with difficult intubations
  • proportion of patients intubated using alternative techniques
  • Complications (incl death, cardiac arrest, cardiovascular collapse, hypoxemia  and others)
  • duration of mechanical ventilation
  • ICU length of stay
  • ICU mortality
  • 28 day mortality

Sample size

Needed 185 patients in each arm assuming a first pass success rate with Dl of 65% and DL increasing this to 80%.


Primary Outcomes

366 patients were successfully intubated.

There was no significant difference with first pass intubation- VL (126 0f 186 patients, [67.7%]); DL (130 of 185 patients, [70.3%]).

Frequency of first pass failure was not significantly different with VL (odds ratio 1.12) both after adjustment for operator expertise (randomization stratification factor) and after adjustment for the MACOCHA score (OR, 1.10 [95% CI, 0.69-1.75]; P = .69).

Secondary Outcomes

VL group had better glottis visualisation, glottis opening score and the bougie was used more often.

Most first intubation attempts were by non experts.

Not surprisingly first intubation attempts were successful more often when performed by experts.

Median duration of intubation of 3 minutes did not differ between groups.

Proportion of patients with severe life threatening complications was higher in the video laryngoscopy group (9.5% vs 2.8% in the direct laryngoscopy group; absolute difference, 6.7% [95% CI, 1.8% to 11.6%]; P = .01) but not significantly so.

Duration of mechanical ventilation, ICU length of stay, sepsis-related organ failure assessment score on day 1, sepsis related organ failure assessment score on day 2, ICU mortality, and 28-day mortality did not differ between the 2 groups.

Authors’ Comments and Conclusions

“Improved glottis visualization with video laryngoscopy did not translate into a higher success rate for first-pass intubation because tracheal catheterization under indirect vision was more difficult, in keeping with earlier data.”

“The better visualization of the glottis with video laryngoscopy might lead to a false impression of safety when orotracheal intubation is performed by non experts. The subgroup analyses did not identify factors associated with life-threatening complications with video laryngoscopy. In addition, poorer alignment of the pharyngeal axis, laryngeal axis, and mouth opening despite good glottis visualization by video laryngoscopy can lead to mechanical upper airway obstruction and faster progression to hypoxemia”

“Use of a gum elastic bougie during the first intubation attempt was more common with video laryngoscopy. Due to the indirect visualization of the glottis with video laryngoscopy, some manufacturers recommend using an intubation stylet.”

Among patients in the ICU requiring intubation, video laryngoscopy compared with direct laryngoscopy did not improve first-pass orotracheal intubation rates and was associated with higher rates of severe life-threatening complications.


Multi centre RCT

Objective primary outcome measure (capnography).


Assessed only single type of laryngoscope.

Other blades might have had different outcomes.

Most of first attempts were made by non experts.

Blinding not feasible.


Protective mechanical ventilation in United Kingdom critical care units: A multi-centre audit.

Newell. C et al 2016.

Clinical question.
How compliant are intensive care units in the south-west of England to lung protective ventilation and low/high PEEP titration based on ARDSnet protocols.?

• Observational study.
• Prospectively collected data taken in 2 hourly increments over a 24 hour period.


• 7 intensive care units in the Severn region, 9 intensive care units in Wessex region.


• Adult intensive care units.
• Mainly general intensive care units.
• All patients ventilated with a mandatory mode of ventilation.
• The Wessex area excluded patients who required tight regulation of pCO2.

Primary data endpoints.

• All patients had predicted body weight calculated based on height measurement. The desired total volume was considered to be less than 6.5ml/Kg based on the low vs high tidal volume ARDSnet study.
• Compliance to ARDSnet PEEP protocol was based on the low tidal volume table. This titrated PEEP against FIO2 requirements.


• Data from 80 patients included in the study.
• One intensive care unit did not supply data due to the pCO2 exclusion (neuro ITU).
• The mean tidal volume across both regions was 7.2ml/Kg.
• Overall compliance to 6.5ml/kg ventilation was 34%.
• Patients ventilated on a volume control mode were had a statistically significantly lower tidal volume than patients on pressure control modes of ventilation p-value 0.0001.
• There was a significant difference in mean tidal volumes between the two regions which related to a high use of volume control ventilation in one region compared to the other.
• 72% of patients were compliant to the ARDSnet low PEEP table based on FIO2 requirements.

Author’s conclusion.
There is a large variation in the delivery of lung protective ventilation in the UK which may have adverse consequences. Volume control ventilation seems to convey better compliance to lung protective ventilation.

• A good cross section of intensive care units which may make this generalisable to UK intensive care ventilation practices.


• It is not clear why plateau airway pressure was not measured in this study as this is a key feature of the original ARDSnet protocol.
• Staff on the intensive care units were aware of the study and this may have induced a Hawthorn effect.

Bottom line.
Compliance to 6ml/Kg lung protective ventilation to all ventilated patients is poor.
Protective mechanical ventilation in United Kingdom critical care units: A multicentre audit. Newell. C et al 2016. DOI: 10.1177/1751143716683712
Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The Acute Respiratory Distress Syndrome Network. N Engl J Med 2000; 342: 1301–1308.
ARDSnet PEEP protocol


Association Between Tracheal Intubation During Adult In-Hospital Cardiac Arrest and Survival JAMA 2017


Anderson et al

Clinical Question

The aim of the current study was to evaluate the association between tracheal intubation during adult in-hospital cardiac arrest and survival to hospital discharge using the multicenter Get WithTheGuidelines–Resuscitation (GWTG-R) registry (a prospective quality improvement registry of inhospital cardiac arrest in US hospitals).

This study also aimed to assess whether this association was modified by the first documented rhythm (shockable vs nonshockable) or other patient and event factors explored in prespecified subgroups.


Multicenter, retrospective, observational, matched cohort study which analyzed data from the GWTG-R registry, a prospective quality improvement registry of inhospital cardiac arrest in US hospitals.


American hospitals.


Inclusion criteria: This study included adult patients (aged ≥18 years)with an index cardiac arrest for which they received chest compressions.

Exclusion criteria: Patients who had an invasive airway in place at the time of the cardiac arrest (including tracheal tube, tracheostomy, laryngeal mask airway, or other invasive airways but not including nasopharyngeal or oropharyngeal airways).

Hospital visitors and employees .

For the main analysis, patients with missing data on tracheal intubation, covariates (except race, for which a “not reported” category was created), and survival. This included patients with missing or inconsistent data on timing of tracheal intubation, timing of epinephrine administration, or timing of defibrillation (in those with a shockable rhythm). These patients were included after imputation of missing values in a preplanned sensitivity analysis (see “Statistical Analysis”).

Intervention Tracheal intubation was defined as insertion of a tracheal or tracheostomy tube during the cardiac arrest.

The end of the cardiac arrest was when the patient had return of spontaneous circulation (ROSC) or when resuscitation was terminated without ROSC.

The time to tracheal intubation was defined as the interval in whole minutes from loss of pulses until the tracheal tube was inserted.



Primary outcome: The primary outcome was survival to hospital discharge.

Secondary outcomes:  Secondary outcomes were ROSC and favorable functional outcome at hospital discharge. ROSC was defined as no further need for chest compressions (including cardiopulmonary bypass) sustained for at least 20 minutes.

A cerebral performance category score of 1 (mild or no neurological deficit) or 2 (moderate cerebral disability) was considered a good functional outcome consistent with current Utstein guidelines.


The study population included 108 079 patients from 668 hospitals.

The median age was 69 years, and 45 073 patients (42%) were female.

Among the population, 75 579 patients (69.9%)were intubated, with 71 615 (66.3% of all patients and 94.8% of those intubated) intubated within the first 15minutes.

The median time to tracheal intubation in those intubated within the first 15 minutes was 5minutes (IQR, 3-8 minutes).

Among 88 749 patients with an initial non shockable rhythm, 61 264 (69.0%) were intubated within 15 minutes, with a median time to intubation of 5 minutes (IQR, 3-8minutes).

Among 19 330 patients with an initial shockable rhythm, 10 351 (53.5%) were intubated within 15 minutes. The median time to intubation in these patients was 5 minutes (IQR, 3-8 minutes).

Primary outcome:

A total of 24 256 patients (22.4%) survived to hospital discharge.

In the unadjusted analysis, patients intubated within the first 15 minutes had lower survival compared with those not intubated: 12 140 of 71 615 (17.0%) vs 12 116 of 36 464 (33.2%), respectively (RR = 0.58; 95% CI, 0.57-0.59; P < .001).

Among the study population, 67 540 patients (62.5%) had ROSC (data were missing for 7 patients). The proportion of patients with ROSC was lower in those intubated within the first 15 minutes compared with those not intubated: 42 366 of 71 611 (59.2%) vs 25 174 of 36 461 (69.0%), respectively (RR = 0.75; 95% CI, 0.73-0.76;P < .001).

Of the 103 448 patients without missing data on functional outcome, 16 504 (16.0%) had a good functional outcome.

Time-Dependent Propensity Score–Matched Analysis

43 314 intubated patients [exposed group] matched 1:1 to 43 314 patients without intubation during the same minute [unexposed group], although these patients could have been intubated later.

For patients in the exposed group, the median time to tracheal intubation was 4minutes.

Among the unexposed group, 29 539 patients (68.2%) were intubated at some timepoint after the matching.For these patients, the time to intubation was 8 minutes (IQR, 5-12 minutes).

In this matched cohort, survival was lower among the exposed group than among the unexposed group: 7052 of 43 314 (16.3%) vs 8407 of 43 314 (19.4%), respectively (RR = 0.84; 95% CI, 0.81-0.87; P < .001).

The proportion of patients with ROSC was lower among the exposed group than among the unexposed group: 25 022 of 43 311 (57.8%) vs 25 685 of 43 310 (59.3%), respectively (RR = 0.97;95%CI,0.96-0.99;P < .001).

Good functional outcome was also lower among the exposed group than among the unexposed group: 4439 of 41 868 (10.6%) vs 5672 of 41 733 (13.6%), respectively (RR = 0.78; 95% CI, 0.75-0.81; P < .001).

Sub Group analysis

There was a significant interaction for initial rhythm (P < .001) such that tracheal intubation was more strongly associated with a lower likelihood of survival in those with an initial shockable rhythm (RR = 0.68; 95% CI, 0.65-0.72) compared with those with an initial non shockable rhythm (RR = 0.91;95%CI,0.88-0.94).

In those without preexisting respiratory insufficiency, intubation was associated with lower likelihood of survival (RR = 0.78; 95% CI, 0.75-0.81), whereas no association was seen in those with preexisting respiratory insufficiency (RR = 0.97;95%CI,0.92-1.02).

Authors’ Conclusions

In this large,multicenter, retrospective, observational,matched cohort study, tracheal intubation at any minute within the first 15 minutes during in-hospital cardiac arrest, compared with no intubation during that minute, was associated with a 3% absolute reduction and 16% relative reduction in survival to hospital discharge.

Intubation was also associated with a 2% absolute reduction and 3% relative reduction in ROSC and a 3% absolute reduction and 22% relative reduction in good functional outcome at hospital discharge.

An observational study (n = 470) from 1990 of patients with in hospital cardiac arrest found that tracheal intubation during the cardiac arrest was associated with increased mortality  similar to an observational study from 2001 (n = 445).

A meta-analysis from 2013 of observational out-of-hospital cardiac arrest studies found that tracheal intubation compared with basic airway management was not associated with ROSC but was associated with decreased survival.

Multiple mechanisms could explain a potential causal relationship between tracheal intubation and poor outcomes:

  • Tracheal intubation might lead to a prolonged interruption in chest compressions.
  • Tracheal intubation might lead to hyperventilation and hyperoxia, which are associated with poor outcomes.
  • Tracheal intubation could delay other interventions such as defibrillation or epinephrine administration.
  • Delays in the time to success of intubation could result in inadequate ventilation or oxygenation by other means.
  • Unrecognized esophageal intubation or dislodgement of the tube during the cardiac arrest could lead to fatal outcomes. Potential beneficial effects of intubation include better control of ventilation and oxygenation as well as protection from aspiration.24 Moreover, once an advanced airway is established, chest compressions may be provided in a more continuous fashion.

Tracheal intubation was associated much more strongly with decreased survival among patients with an initial shockable rhythm (32% relative decrease) compared with those with an initial non shockable rhythm (9% relative decrease). These findings may indicate that the potential detrimental effects of intubation are more pronounced in patients with a shockable rhythm, for whom other interventions such as early defibrillation are more relevant.



US only based.

Unable to identify some of the potential confounders.

Data on unsuccessful intubation attempts not available- potential bias.

Data missing on a least one variable for 25% of the patients.

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