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Foundational Trials

MACMAN

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Publication

  • Title: Video Laryngoscopy vs Direct Laryngoscopy on Successful First-Pass Orotracheal Intubation Among ICU Patients: A Randomized Clinical Trial
  • Acronym: MACMAN
  • Year: 2017
  • Journal published in: JAMA
  • Citation: Lascarrou JB, Boisrame-Helms J, Bailly A, et al; Clinical Research in Intensive Care and Sepsis (CRICS) Group. Video laryngoscopy vs direct laryngoscopy on successful first-pass orotracheal intubation among ICU patients: a randomized clinical trial. JAMA. 2017;317(5):483-493.

Context & Rationale

  • Background
    • Tracheal intubation in the ICU is frequent and physiologically hazardous, with high rates of hypoxaemia, cardiovascular collapse, and cardiac arrest.
    • First-pass success is a plausible, modifiable driver of safety because repeated attempts increase duration of apnoea and airway trauma and may compound haemodynamic instability.
    • Videolaryngoscopy improves glottic visualisation in operating theatres, but effectiveness and safety in ICU intubations were uncertain given different case-mix (hypoxaemia, shock), operator mix, and urgency.
    • Prior ICU data were dominated by observational studies and small trials, with inconsistent signals for first-pass success and limited harms reporting.
  • Research Question/Hypothesis
    • In adults requiring ICU orotracheal intubation, does first-attempt use of a Macintosh-blade videolaryngoscope (McGrath MAC) increase successful first-pass intubation compared with standard Macintosh direct laryngoscopy?
    • Hypothesis underpinning sample size: videolaryngoscopy would increase first-pass success from 65% to 80% (15% absolute improvement).
  • Why This Matters
    • Routine adoption of videolaryngoscopy in critical care has major implications for procurement, training, and airway algorithms.
    • A neutral or harmful effect would shift emphasis to physiology-first airway bundles and targeted device use (anticipated difficulty, supervision), rather than universal deployment.
    • Clarifying whether improved laryngeal view translates into clinically meaningful first-pass success in ICU patients is essential before extrapolating from theatre evidence.

Design & Methods

  • Research Question: In adult ICU patients requiring orotracheal intubation, does first-attempt McGrath MAC videolaryngoscopy (indirect view) improve first-pass success compared with Macintosh direct laryngoscopy?
  • Study Type: Multicentre, parallel-group, investigator-initiated, unblinded randomised clinical trial; 7 adult ICUs in France; May 2015 to January 2016.
  • Population:
    • Setting: adult ICU patients requiring orotracheal intubation, for any indication.
    • Inclusion: adults (≥18 years) requiring orotracheal intubation in ICU.
    • Key exclusions: pregnancy; contraindication to orotracheal intubation; nasotracheal intubation; fibreoptic intubation planned; no time for inclusion/randomisation; previous study inclusion; protected persons (guardianship/curatorship); persons deprived of liberty; no health insurance; refusal.
    • Operator strata: randomisation stratified by centre and operator status (expert vs non-expert).
    • Expert definition: ≥5 years ICU experience, or ≥1 year ICU experience after ≥2 years of anaesthesiology training.
  • Intervention:
    • Device: McGrath MAC videolaryngoscope (Covidien).
    • First-pass technique: indirect view on the screen mandated for the first attempt.
    • Adjuncts on first attempt: no endotracheal tube stylet and no gum elastic bougie.
    • After first-attempt failure: repeat laryngoscopy or alternative airway technique at the operator’s discretion, consistent with local guidelines; subsequent laryngoscopy attempts could use videolaryngoscopy with indirect or direct view.
  • Comparison:
    • Device: standard Macintosh direct laryngoscope.
    • Adjuncts on first attempt: no endotracheal tube stylet and no gum elastic bougie.
    • After first-attempt failure: repeat laryngoscopy or alternative airway technique at the operator’s discretion, consistent with local guidelines.
  • Blinding: Unblinded (operators and bedside staff); primary endpoint objective (capnography-confirmed), but open-label delivery could influence process measures and some complication reporting.
  • Statistics: A total of 370 patients were required to detect a 15% absolute increase in first-pass success (from 65% to 80%) with 90% power (type II error 10%) at a 2-sided 5% significance level; primary analysis was intention-to-treat using a mixed-effects logistic regression model (centre random effect; group and operator status fixed effects); missing primary endpoint counted as failure; secondary outcomes were not adjusted for multiplicity.
  • Follow-Up Period: Peri-intubation outcomes during the procedure and up to 1 hour post-intubation; ICU outcomes followed to day 28 (mortality and other follow-up data reported in the supplement).

Key Results

This trial was not stopped early. Recruitment met the planned sample size (371 randomised; target 370); no interim stopping was reported.

Outcome McGrath MAC videolaryngoscopy Macintosh direct laryngoscopy Effect p value / 95% CI Notes
Successful first-pass orotracheal intubation (primary; intention-to-treat) 126/186 (67.7%) 130/185 (70.3%) Absolute difference −2.5% 95% CI −11.9 to 6.9; P=0.60 Success required waveform capnography for ≥4 breaths.
Successful first-pass orotracheal intubation (per-protocol) 126/183 (68.9%) 130/182 (71.4%) Absolute difference −2.5% 95% CI −12.3 to 6.4; P=0.54 Per-protocol population n=365.
Glottic view: Cormack–Lehane grade I 133/176 (75.6%) 93/177 (52.5%) Absolute difference 23.1% 95% CI 13.3 to 32.7; P<0.001 Better visualisation with videolaryngoscopy did not translate into higher first-pass success.
Time to successful intubation (min; median [IQR]) 3.9 (2.8 to 7.0) 3.8 (2.4 to 6.4) Median difference 0.0 min 95% CI −0.6 to 0.4; P=0.74 Measured from start of anaesthetic induction to capnography confirmation.
Any life-threatening complication (prespecified composite) 24/180 (13.3%) 17/179 (9.5%) Absolute difference 3.8% 95% CI −2.7 to 10.4; P=0.25 Composite included severe hypoxaemia, severe cardiovascular collapse, cardiac arrest, and death.
Severe life-threatening complication (post hoc composite) 17/179 (9.5%) 5/179 (2.8%) Absolute difference 6.7% 95% CI 1.8 to 11.6; P=0.01 Post hoc severity categorisation; no multiplicity adjustment across secondary outcomes.
Day-28 mortality 66/185 (35.7%) 67/184 (36.4%) Absolute difference −0.7% 95% CI −10.5 to 9.1; P=0.88 Follow-up outcome; trial not powered for mortality.
  • Videolaryngoscopy improved glottic view (Cormack–Lehane grade I 75.6% vs 52.5%) but did not improve first-pass success (67.7% vs 70.3%).
  • Sensitivity analysis (intention-to-treat) adjusting for MACOCHA >4 showed no difference in first-pass failure (aOR for videolaryngoscopy 1.10; 95% CI 0.69 to 1.75; P=0.69).
  • In the per-protocol MACOCHA subgroup analysis, first-pass success remained similar in MACOCHA >4 (64.9% videolaryngoscopy vs 67.7% direct; absolute difference 2.9%; 95% CI −19.6 to 25.4; interaction P=0.55).

Internal Validity

  • Randomisation and allocation:
    • Centralised, computer-generated randomisation (software), using permuted blocks of 4 and stratified by centre and operator status (expert vs non-expert).
    • Analytic approach matched the stratified design (mixed-effects logistic regression with centre random effect; group and operator status fixed effects).
  • Dropout or exclusions:
    • 371 patients randomised (186 videolaryngoscopy; 185 direct laryngoscopy).
    • Primary endpoint missing in 5 participants; per protocol, these were counted as first-pass failures.
    • Per-protocol analysis included 365 participants (183 videolaryngoscopy; 182 direct laryngoscopy).
  • Performance and detection bias:
    • Unblinded intervention and bedside outcome recording introduce potential performance bias (operator behaviour) and detection bias for clinician-judgement outcomes.
    • Primary outcome definition was objective and pre-specified (capnography-confirmed first pass).
    • Many complications were defined using physiologic thresholds (e.g., oxygen saturation and blood pressure), limiting subjectivity; some events (e.g., aspiration, airway trauma) remain susceptible to reporting differences.
  • Protocol adherence:
    • Allocated device was used for the first attempt in 183/186 (98.4%) in the videolaryngoscopy group and 182/185 (98.4%) in the direct laryngoscopy group.
    • Induction and preoxygenation were protocol-guided but clinician-selected; key elements were similar between groups (e.g., etomidate 89.1% vs 90.7%; succinylcholine 78.3% vs 75.8%; bag-valve-mask preoxygenation 51.6% vs 52.5%).
    • Mandated technique differences (indirect view for videolaryngoscopy first attempt; no stylet/bougie on first attempt in either group) enhanced between-group separation but may not reflect all contemporary videolaryngoscopy practices.
  • Baseline characteristics:
    • Overall severity was high and balanced (SAPS II mean 58.0 vs 57.7; SOFA median 7 vs 7; PaO2:FiO2 median 95 vs 91).
    • Indications for intubation were similar (acute respiratory failure 65.6% vs 63.8%; coma 23.1% vs 24.3%).
  • Heterogeneity:
    • Seven ICUs with broad indications and variable physiology (shock, hypoxaemia) increase pragmatic relevance but add clinical heterogeneity.
    • Most intubations were performed by non-experts (84.4% vs 83.2%), reflecting typical ICU workforce structures but potentially increasing sensitivity to learning-curve effects.
  • Timing:
    • Randomisation occurred at the time of the intubation procedure, with immediate application of allocated device.
    • Time-to-success was defined from the start of anaesthetic induction, not laryngoscope insertion, which may dilute device-related differences in “laryngoscopy time”.
  • Separation of the variable of interest:
    • Laryngeal view was substantially better with videolaryngoscopy (Cormack–Lehane grade I 75.6% vs 52.5%; P<0.001).
    • Despite improved view, rescue bougie use after first-attempt failure was more common with videolaryngoscopy (12.0% vs 5.5%; P=0.03), suggesting challenges with tube delivery/catheterisation.
    • Time to successful intubation was similar (median 3.9 vs 3.8 minutes; P=0.74), indicating that improved view did not produce procedural efficiency gains in this setting.
  • Outcome assessment:
    • Primary outcome was clearly defined and objectively verified.
    • Complication composites were prespecified, but the “severe life-threatening” composite was post hoc, reducing robustness of inference for that signal.
  • Statistical rigor:
    • Planned sample size achieved (371 randomised vs 370 planned).
    • Primary analysis followed intention-to-treat with prespecified handling of missing primary endpoint (counted as failure).
    • Secondary outcomes were not adjusted for multiplicity, so individual secondary P values should be interpreted as exploratory.

Conclusion on Internal Validity: Overall, internal validity appears moderate-to-strong given robust randomisation, minimal attrition, and an objective primary endpoint; however, open-label delivery and extensive, unadjusted secondary comparisons (including a post hoc “severe” composite) limit confidence in some secondary and harm inferences.

External Validity

  • Population representativeness:
    • High-severity adult ICU population (SAPS II ~58; PaO2:FiO2 ~90–95), broadly reflective of many ICU intubations in high-income systems.
    • Exclusions (e.g., “no time for inclusion/randomisation”, planned fibreoptic/nasotracheal intubation, pregnancy) reduce applicability to crash intubations and selected airway pathologies.
  • Applicability:
    • Device-specific (McGrath MAC) and technique-specific (indirect view mandated on first attempt; no stylet/bougie on first attempt), which may not map to current practice in some ICUs that routinely use stylets or different videolaryngoscope designs.
    • Operator-mix (majority non-expert intubators) enhances relevance to training environments; effects may differ where intubations are performed predominantly by airway experts.
    • Centres were in France with guideline-informed practice (e.g., general anaesthesia with hypnotic and neuromuscular blockade); transferability to systems with different drug availability, staffing, and airway pathways is uncertain.

Conclusion on External Validity: External validity is moderate: findings are most generalisable to routine ICU intubations in resourced centres using Macintosh-blade videolaryngoscopy with mixed-experience operators, but extrapolation to crash scenarios, other device designs, or different adjunct strategies is less secure.

Strengths & Limitations

  • Strengths:
    • Multicentre, pragmatic ICU trial with broad indications and high illness severity.
    • Central randomisation with stratification by centre and operator status.
    • Objective, clinically relevant primary endpoint (capnography-confirmed first-pass success).
    • High protocol delivery for first attempt (≈98% received allocated device) and minimal missingness for the primary endpoint.
  • Limitations:
    • Unblinded design may influence operator behaviour and reporting of some complications.
    • Mandated technique (indirect view on first attempt; no stylet/bougie on first attempt) may not reflect optimised or contemporary videolaryngoscopy practice in all ICUs.
    • Control first-pass success was higher than expected (observed ~70% vs assumed 65%), reducing power to detect smaller benefits than the prespecified 15% absolute increase.
    • Secondary outcomes were not multiplicity-adjusted, and the “severe life-threatening complications” signal was based on a post hoc composite definition.

Interpretation & Why It Matters

  • Clinical practice
    • Routine first-attempt McGrath MAC videolaryngoscopy (as delivered in this trial) did not improve first-pass success compared with Macintosh direct laryngoscopy.
    • Improved visualisation alone is an insufficient surrogate for success in ICU intubation, where tube delivery, apnoea tolerance, and haemodynamic instability are dominant constraints.
  • Mechanistic signal
    • The combination of better view (Cormack–Lehane grade I 75.6% vs 52.5%) and higher post-first-attempt bougie use (12.0% vs 5.5%) supports a “see more, struggle to pass” interpretation for Macintosh-blade videolaryngoscopy when used indirectly without a stylet on first attempt.
    • This underscores that device design and adjunct strategy (stylet shaping, bougie use, external laryngeal manipulation) are integral to effectiveness, not optional add-ons.
  • Implementation & safety
    • The neutral primary outcome and uncertain secondary harm signal reinforce the need to implement videolaryngoscopy alongside physiologically optimised airway bundles, minimised attempts, and structured training/supervision.
    • Device adoption decisions should be made on patient-centred endpoints (first-pass success and complications), not laryngeal view alone.

Controversies & Subsequent Evidence

  • Post hoc severe-complication signal:
    • The higher rate of “severe life-threatening complications” with videolaryngoscopy (9.5% vs 2.8%; P=0.01) was derived from a post hoc severity categorisation, within a framework of multiple unadjusted secondary outcomes, increasing the probability of a chance finding and limiting causal inference.1
  • Correspondence on definitions and technique (what was really being tested):
    • Time-to-success was measured from start of anaesthetic induction rather than from laryngoscope insertion, potentially obscuring device-specific effects on laryngoscopy duration and apnoea exposure.
    • For a Macintosh-blade videolaryngoscope, mandating indirect view for first attempt and prohibiting stylet/bougie on the first attempt was challenged as potentially suboptimal and not reflective of common videolaryngoscopy technique, raising concerns about whether the intervention was “videolaryngoscopy as typically practised” versus a constrained technique.
    • The authors’ reply emphasised a pragmatic comparison with symmetrical adjunct restrictions on the first attempt, and argued that improved view without improved first-pass success reflected real-world constraints in ICU intubation.2345
  • Subsequent RCT evidence shifted the evidential centre of gravity:
    • In the single-centre ICU FELLOW trial, first-pass success did not differ (68.9% vs 65.8%; unadjusted P=0.68), aligning with MACMAN’s neutral primary outcome despite improved view with videolaryngoscopy.6
    • In the larger multicentre DEVICE trial of critically ill adults, videolaryngoscopy improved first-attempt success (85.1% vs 70.8%; absolute risk difference 14.3 points; 95% CI 9.9 to 18.7) with similar severe complications (21.4% vs 20.9%; difference 0.5 points; 95% CI −3.9 to 4.9), implying that context, operator factors, and device/technique implementation materially influence clinical effect.7
  • Meta-analytic synthesis:
    • Systematic reviews generally report higher first-pass success with videolaryngoscopy outside the operating theatre but emphasise heterogeneity across devices, operator experience, and setting, and inconsistent effects on patient-centred outcomes—consistent with MACMAN’s “better view, same first-pass success” phenotype and later trial-to-trial variability.89
  • Guideline trajectory:
    • Recent guidance increasingly recommends videolaryngoscopy availability (and often first-line use) for ICU intubation, but places equal emphasis on training, physiologic optimisation, and minimising attempts—principles that sit alongside MACMAN’s device-specific neutral primary outcome and highlight that “videolaryngoscopy” is an implementation strategy, not a single invariant intervention.10111213

Summary

  • In 371 ICU intubations, first-attempt McGrath MAC videolaryngoscopy did not improve first-pass success versus Macintosh direct laryngoscopy (67.7% vs 70.3%).
  • Videolaryngoscopy markedly improved laryngeal view (Cormack–Lehane grade I 75.6% vs 52.5%) but did not reduce time to successful intubation (median 3.9 vs 3.8 minutes).
  • Overall life-threatening complications were not significantly different; a post hoc “severe” composite was higher with videolaryngoscopy (9.5% vs 2.8%), warranting cautious interpretation.
  • Mortality to day 28 was similar (35.7% vs 36.4%); the trial was not powered for survival endpoints.
  • MACMAN is a landmark ICU airway trial because it demonstrates that improved glottic exposure is not a sufficient surrogate for first-pass success, and that device effects depend on technique and context.

Further Reading

Other Trials

Systematic Review & Meta Analysis

Observational Studies

Guidelines

Overall Takeaway

MACMAN is “landmark” because it challenged an intuitive assumption—better glottic view equals better intubation success—in the physiologically high-risk ICU context. It showed that Macintosh-blade videolaryngoscopy (as delivered: indirect first-pass view without a stylet/bougie) did not improve first-pass success versus direct laryngoscopy, while highlighting that device effects are tightly coupled to technique, operator factors, and implementation context.

Overall Summary

  • McGrath MAC videolaryngoscopy improved laryngeal view but did not increase first-pass success in ICU intubations.
  • The post hoc severe-complication signal requires cautious interpretation given multiplicity and post hoc definition.
  • Later larger trials and meta-analyses support that videolaryngoscopy benefits depend on device choice, adjunct strategy, and implementation quality.

Bibliography