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Mechanical Ventilation

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General Information

  • respiratory failure is the most common indication for mechanical ventilation
    • may occur due to
      • ventilatory failure
        • characterized by increased arterial carbon dioxide tension (PaCO2) due to alveolar hypoventilation or increased sustained work of breathing
        • managed by assisting patient to maintain alveolar ventilation (alveolar ventilation = minute ventilation minus dead space, with minute ventilation = tidal volume (Vt) × respiratory rate)
      • failure to oxygenate
        • characterized by abnormally low PaO2:FiO2 (P:F) and/or requirement for positive pressure to maintain P:F
        • caused by ventilation perfusion mismatch, decreased alveolar oxygen tension, and/or alveolar hypoventilation
        • treatment includes ≥ 1 of
          • increasing fraction of inspired oxygen (FiO2)
          • increasing airway pressure
          • increasing lung segment recruitment (by applying positive end-expiratory pressure [PEEP] and increasing duration of inspiration [i-time])
    • can be managed by
    • References
  • no uniform criteria for determining need for endotracheal intubation and mechanical ventilation exists
    • decision should be based on clinical judgment
    • generally considered for
      • inability to maintain adequate oxygenation (defined as arterial oxygen saturation ≥ 90%) despite use of supplemental oxygen
      • inadequate spontaneous ventilation and/or sustained high work of breathing (tachypnea) despite maximal noninvasive support
      • inability to protect one's airway
    • decision to intubate should also include a reasoned assessment of the timely reversibility of the condition for which mechanical support is being considered
    • References
  • 2 major invasive mechanical ventilation classifications are distinguished by which parameter triggers transition from inspiration to expiration2
    • volume-controlled ventilation (VCV) - breaths are triggered by patient or ventilator, limited by flow and cycled (ended) by volume (volume remains constant)
    • pressure-controlled ventilation (PCV) - breaths are triggered by patient or ventilator, limited by pressure, and cycled (ended) by time or flow (pressure remains constant)
      Mechanical ventiliation
      Image 1 of 1

      Mechanical ventiliation

      Volume control (top) and pressure control (bottom) are 2 major modes of mechanical ventilation. Black: volume; Red: airway pressure; Green: flow.

References

References

General references used

  1. Goligher E, Ferguson ND. Mechanical ventilation: epidemiological insights into current practices. Curr Opin Crit Care. 2009 Feb;15(1):44-51OpenInNew
  2. Mireles-Cabodevila E, Diaz-Guzman E, Heresi GA, Chatburn RL. Alternative modes of mechanical ventilation: a review for the hospitalist. Cleve Clin J Med. 2009 Jul;76(7):417-30OpenInNewfull-textOpenInNew, correction can be found in Cleve Clin J Med. 2009 Aug;76(8):445

Recommendation grading systems used

  • American Thoracic Society/European Society of Intensive Care Medicine/Society of Critical Care Medicine (ATS/ESICM/SCCM) grading system
    • strength of recommendations
      • Strong recommendation
        • most patients should receive the recommended course of action
        • most patients would want the intervention, only a small proportion would not
      • Conditional/Weak recommendation
        • clinicians should be more prepared to help patients make decisions consistent with patient's values
        • most patients would want the intervention, but many would not
    • quality of evidence determination and implications/confidence in estimate of effect
      • High
        • randomized trial without limitation in study quality, indirectness, important inconsistency, sparse or imprecise data, or high probability of publication bias
        • further research is very unlikely to change confidence in estimate of effect
      • Moderate
        • downgraded randomized trial or upgraded observational study with strong association (no plausible confounders), evidence of a dose-response gradient, or plausible confounders which would have reduced the effect
        • further research is likely to have important impact on confidence in estimate of effect and may change estimate
      • Low
        • well-done observational study with control groups
        • further research is very likely to have important impact on confidence in estimate of effect and is likely to change estimate
      • Very low
        • any other evidence (for example, case reports, case series)
        • very uncertain about estimate
    • Reference - ATS/ESICM/SCCM clinical practice guideline on mechanical ventilation in adult patients with acute respiratory distress syndrome (28459336Am J Respir Crit Care Med 2017 May 1;195(9):1253OpenInNew)
  • American Thoracic Society/American College of Chest Physicians (ATS/ACCP) grading system
    • strength of recommendation
      • Strong - most individuals should receive intervention; adherence to recommendation according to guideline could be used as quality criterion or performance indicator
      • Conditional - different choices will be appropriate for individual patients; help each patient arrive at management decision consistent with his or her values and preferences
    • levels of evidence
      • High - further research is very unlikely to change our confidence in the estimate of effect
      • Moderate - further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate
      • Low - further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate
      • Very low - any estimate of effect is very uncertain
    • Reference - ATS/ACCP clinical practice guideline on liberation from mechanical ventilation in critically ill adults (27762608Am J Respir Crit Care Med 2017 Jan 1;195(1):115OpenInNew)
  • American College of Critical Care Medicine/Society of Critical Care Medicine (ACCCM/SCCM) 2018 grading system
    • strengths of recommendation
      • Strong recommendation - benefits of intervention significantly outweigh risks (or vice versa) and majority of patients and clinicians would and should pursue this course of action (or not)
      • Conditional recommendation - benefits of intervention likely outweigh risks (or vice versa) but guideline developers were not confident in quality of evidence or trade-offs between risks and benefits were closely balanced
      • Good practice statement - strong but ungraded recommendation in which there is unequivocal belief that benefit of intervention outweighs risk but no available direct evidence could be summarized or evaluated
    • quality of evidence
      • High
        • randomized controlled trials (RCTs) without important limitations
        • observational studies upgraded 2 levels based on large effect, dose-response, and/or antagonistic bias
      • Moderate
        • RCTs downgraded 1 level for risk of bias, inconsistency, indirectness, imprecision, or publication bias
        • observational studies upgraded 1 level based on large effect, dose-response, or antagonistic bias
      • Low
        • observational studies
        • RCTs downgraded 2 levels for risk of bias, inconsistency, indirectness, imprecision, and/or publication bias
      • Very low - RCTs downgraded 3 levels or observational studies downgraded 1 level for risk of bias, inconsistency, indirectness, imprecision, and/or publication bias
    • Reference - ACCM/SCCM clinical practice guideline on prevention and management of pain, agitation/sedation, delirium, immobility, and sleep disruption in adult patients in the ICU (30113379Crit Care Med 2018 Sep;46(9):e825OpenInNew)
  • American College of Critical Care Medicine/Society of Critical Care Medicine (ACCCM/SCCM) uses Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system
    • strengths of recommendation
      • Strong - we recommend
      • Weak - we suggest
      • Good practice statement - no clear alternative exists and consensus among Task Force members
    • levels of evidence
      • High-quality evidence - further research unlikely to change confidence in estimate of effect
      • Moderate-quality evidence - further research likely to have impact on confidence in estimate of effect
      • Low-quality evidence - further research very likely to have important impact on confidence in estimate of effect and is likely to change estimate
      • Very low-quality evidence - estimate of effect very uncertain
    • Reference - ACCCM/SCCM clinical practice guideline on sustained neuromuscular blockage in adult critically ill patient (27755068Crit Care Med 2016 Nov;44(11):2079OpenInNew)
  • British Thoracic Society/Intensive Care Society (BTS/ICS) uses Scottish Intercollegiate Guidelines Network (SIGN) grading system
    • grades of recommendations
      • Grade A
        • at least 1 meta-analysis, systematic review, or randomized controlled trial (RCT) rated as 1++ and directly applicable to the target population, or
        • body of evidence consisting principally of studies rated as 1+, directly applicable to target population and demonstrating overall consistency of results
      • Grade B
        • body of evidence including studies rated as 2++, directly applicable to target population and demonstrating overall consistency of results, or
        • extrapolated evidence from studies rated as 1++ or 1+
      • Grade C
        • body of evidence including studies rated as 2+, directly applicable to target population and demonstrating overall consistency of results, or
        • extrapolated evidence from studies rated as 2++
      • Grade D
        • evidence level 3 or 4, or
        • extrapolated evidence from studies rated as 2+
      • Good Practice Point (GPP) - recommended best practice based on clinical experience of guideline development group
    • levels of evidence
      • 1++ - high-quality meta-analyses, systematic reviews of RCTs, or RCTs with very low risk of bias
      • 1+ - well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with low risk of bias
      • 1- - meta-analyses, systematic reviews of RCTs, or RCTs with high risk of bias
      • 2++
        • high-quality systematic reviews of case-control or cohort studies
        • high-quality case-control or cohort studies with very low risk of confounding or bias and high probability that relationship is causal
      • 2+ - well-conducted case-control or cohort studies with low risk of confounding or bias and moderate probability that relationship is causal
      • 2- - case-control or cohort studies with high risk of confounding or bias and significant risk that relationship is not causal
      • 3 - nonanalytical studies (for example, case reports, case series)
      • 4 - expert opinion
    • Reference - BTS/ICS guideline on ventilatory management of acute hypercapnic respiratory failure in adults (26976648Thorax 2016 Apr;71 Suppl 2:ii1OpenInNew)
  • American College of Chest Physicians, American Association for Respiratory Care, and American College of Critical Care Medicine (ACCP/AARC/ACCCM) grades of evidence
    • Grade A - scientific evidence provided by well-designed, well-conducted, controlled trials (randomized and nonrandomized) with statistically significant results that consistently support the guideline recommendation
    • Grade B - scientific evidence provided by observational studies or by controlled trials with less consistent results to support the guideline recommendation
    • Grade C - expert opinion supported the guideline recommendation, but scientific evidence either provided inconsistent results or was lacking
    • Reference - ACCP/AARC/ACCCM task force evidence-based guideline on weaning and discontinuing ventilatory support can be found in aph10359286pa9h10359286pbyh10359286pafh10359286phch10359286pnyh10359286pcxh10359286pChest 2001 Dec;120(6 Suppl):375SOpenInNew
  • British Medical Journal (BMJ) Rapid Recommendations uses Grades of Recommendation, Assessment, Development, and Evaluation (GRADE)
    • strength of recommendation
      • Strong - most patients should receive recommended course of action; decision aids unnecessary as almost all informed patients will make same choice
      • Weak - clinicians should recognize that different choices will be appropriate for different patients and must help each patient arrive at management decision consistent with his or her values or preferences
    • quality of evidence
      • High - panel is very confident that true effect lies to close to estimate of effect
      • Moderate - panel is moderately confident in effect estimate; true effect is likely to be close to estimate of effect, but there is possibility that it is substantially different
      • Low - panel's confidence in effect estimate is limited; true effect may be substantially different from estimate of effect
      • Very low - panel has very little confidence in effect estimate; true effect is likely to be substantially different from estimate of effect
    • Reference - BMJ Rapid Recommendations clinical practice guideline on oxygen therapy for acutely ill medical patients (BMJ 2018 Oct 24;363:k4169OpenInNew), editorial can be found in BMJ 2018 Oct 24;363:k4436OpenInNew

Synthesized Recommendation Grading System for DynaMed

  • DynaMed systematically monitors clinical evidence to continuously provide a synthesis of the most valid relevant evidence to support clinical decision-making (see 7-Step Evidence-Based MethodologyOpenInNew).
  • Guideline recommendations summarized in the body of a DynaMed topic are provided with the recommendation grading system used in the original guideline(s), and allow DynaMed users to quickly see where guidelines agree and where guidelines differ from each other and from the current evidence.
  • In DynaMed (DM), we synthesize the current evidence, current guidelines from leading authorities, and clinical expertise to provide recommendations to support clinical decision-making in the Overview & Recommendations section.
  • We use the Grading of Recommendations Assessment, Development and Evaluation (GRADE)OpenInNew to classify synthesized recommendations as Strong or Weak.
    • Strong recommendations are used when, based on the available evidence, clinicians (without conflicts of interest) consistently have a high degree of confidence that the desirable consequences (health benefits, decreased costs and burdens) outweigh the undesirable consequences (harms, costs, burdens).
    • Weak recommendations are used when, based on the available evidence, clinicians believe that desirable and undesirable consequences are finely balanced, or appreciable uncertainty exists about the magnitude of expected consequences (benefits and harms). Weak recommendations are used when clinicians disagree in judgments of relative benefit and harm, or have limited confidence in their judgments. Weak recommendations are also used when the range of patient values and preferences suggests that informed patients are likely to make different choices.
  • DynaMed (DM) synthesized recommendations (in the Overview & Recommendations section) are determined with a systematic methodology:
    • Recommendations are initially drafted by clinical editors (including ≥ 1 with methodological expertise and ≥ 1 with content domain expertise) aware of the best current evidence for benefits and harms, and the recommendations from guidelines.
    • Recommendations are phrased to match the strength of recommendation. Strong recommendations use "should do" phrasing, or phrasing implying an expectation to perform the recommended action for most patients. Weak recommendations use "consider" or "suggested" phrasing.
    • Recommendations are explicitly labeled as Strong recommendations or Weak recommendations when a qualified group has explicitly deliberated on making such a recommendation. Group deliberation may occur during guideline development. When group deliberation occurs through DynaMed-initiated groups:
      • Clinical questions will be formulated using the PICO (Population, Intervention, Comparison, Outcome) framework for all outcomes of interest specific to the recommendation to be developed.
      • Systematic searches will be conducted for any clinical questions where systematic searches were not already completed through DynaMed content development.
      • Evidence will be summarized for recommendation panel review including for each outcome, the relative importance of the outcome, the estimated effects comparing intervention and comparison, the sample size, and the overall quality rating for the body of evidence.
      • Recommendation panel members will be selected to include at least 3 members that together have sufficient clinical expertise for the subject(s) pertinent to the recommendation, methodological expertise for the evidence being considered, and experience with guideline development.
      • All recommendation panel members must disclose any potential conflicts of interest (professional, intellectual, and financial), and will not be included for the specific panel if a significant conflict exists for the recommendation in question.
      • Panel members will make Strong recommendations if and only if there is consistent agreement in a high confidence in the likelihood that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. Panel members will make Weak recommendations if there is limited confidence (or inconsistent assessment or dissenting opinions) that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. No recommendation will be made if there is insufficient confidence to make a recommendation.
      • All steps in this process (including evidence summaries which were shared with the panel, and identification of panel members) will be transparent and accessible in support of the recommendation.
    • Recommendations are verified by ≥ 1 editor with methodological expertise, not involved in recommendation drafting or development, with explicit confirmation that Strong recommendations are adequately supported.
    • Recommendations are published only after consensus is established with agreement in phrasing and strength of recommendation by all editors.
    • If consensus cannot be reached then the recommendation can be published with a notation of "dissenting commentary" and the dissenting commentary is included in the topic details.
    • If recommendations are questioned during peer review or post publication by a qualified individual, or reevaluation is warranted based on new information detected through systematic literature surveillance, the recommendation is subject to additional internal review.

DynaMed Editorial Process

Special acknowledgements

  • DynaMed topics are written and edited through the collaborative efforts of the above individuals. Deputy Editors, Section Editors, and Topic Editors are active in clinical or academic medical practice. Recommendations Editors are actively involved in development and/or evaluation of guidelines.
  • Editorial Team role definitions
    Topic Editors define the scope and focus of each topic by formulating a set of clinical questions and suggesting important guidelines, clinical trials, and other data to be addressed within each topic. Topic Editors also serve as consultants for the internal DynaMed Editorial Team during the writing and editing process, and review the final topic drafts prior to publication.
    Section Editors have similar responsibilities to Topic Editors but have a broader role that includes the review of multiple topics, oversight of Topic Editors, and systematic surveillance of the medical literature.
    Recommendations Editors provide explicit review of DynaMed Overview and Recommendations sections to ensure that all recommendations are sound, supported, and evidence-based. This process is described in "Synthesized Recommendation Grading."
    Deputy Editors are employees of DynaMed and oversee DynaMed internal publishing groups. Each is responsible for all content published within that group, including supervising topic development at all stages of the writing and editing process, final review of all topics prior to publication, and direction of an internal team.

How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T253048, Mechanical Ventilation; [updated 2018 Nov 30, cited place cited date here]. Available from https://www.dynamed.com/topics/dmp~AN~T253048. Registration and login required.

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