Students should be able to describe:
- The major indications for intubation.
- The role of non-invasive mask ventilation in managing patients with acute on chronic respiratory failure secondary to COPD.
- The difference between pressure and volume cycled ventilators.
- Typical initial adult ventilator settings.
- How to assess the adequacy of these initial ventilator settings.
- An understanding of how to calculate and interpret Airways Resistance and Respiratory System Compliance.
- Ventilator Strategies for the management of patients suffering from ARDS.
- An approach to Weaning.
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Students should be able to:
HISTORY AND PHYSICAL EXAM:
- Recognize the symptoms and signs of impending respiratory failure.
- Succinctly present data relevant to the evaluation of the mechanically ventilated patient to members of the health care team.
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Students should be able to:
- Show empathy for the mechanically ventilated patient and, specifically, be cognizant of the potential for patient discomfort
- Interact with the mechanically ventilated patient in a professional and personal fashion, despite the inherent communication difficulties
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Mechanical Ventilation Principles
- Tobin MJ: Mechanical ventilation. N Engl J Med 1994:330:1056-60.
- http://www.icucorner.com/vents-101.html A recorded powerpoint presentation summarizing the basics of mechanical ventilation.
- Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med 1995; 332:345-50. Prospective, randomized study found once daily or multiple daily trials of spontaneous breathing (T-piece or CPAP <5 cm) resulted in more rapid successful extubation than gradual weaning of pressure support or IMV.
- Brochard L, Rauss A, Benito S, et al. Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation. Am J Respir Crit Care Med 1994; 150:896-903. Prospective, randomized study found weaning with pressure support mode superior to SIMV mode and T-piece trials. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=7921460
- Yang KL, Tobin MJ. A prospective study of indexes predicting the outcome of trials of weaning from mechanical ventilation. N Engl J Med 1991; 324:1445-50. Study in a VA population found the rapid shallow breathing index (RSBI = RR/Vtidal) was the single best predictor of weaning success (sensitivity 0.97, specificity 0.64). http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2023603
- Keenan SP, et al. Which patients with acute exacerbation of chronic
obstructive pulmonary disease benefit from noninvasive positive-pressure
ventilation? A systematic review of the literature. Annals of Int Med 2003;
Esteban A, et al. Noninvasive Positive-Pressure Ventilation for Respiratory
Failure after Extubation. NEJM 2004;350:2452-60.
F/U editorial by Truwit JD and Bernard GR. Noninvasive Ventilation Ė Donít
Push Too Hard. NEJM 2004;350:2512-15.
- A meta-analysis describing the benefit of CPAP/BiPAP in exacerbations of COPD.
Mechanical Ventilation in Specific Disease States
- Darioli R, Perret C. Mechanical controlled hypoventilation in status asthmaticus.
Am Rev Respir Dis 1984;129:385-7. Noteworthy for being the first description of
permissive hypercapnea and low tidal volumes during mechanical ventilation of
asthmatics with high airway pressures.
- ARDS Network. Ventilation with lower tidal volumes as compared with traditional
tidal volumes for ALI and ARDS. N Engl J Med. 2000;342:1301-8. Results of the
ARMA study found the use of low (6 ml/kg predicted weight) rather than "standard" (12 ml/kg predicted weight) tidal volumes reduced mortality from 40
to 30%. These results form much of the basis for use of low- stretch/low tidal
volume ventilation strategy in acute lung injury.
- Eichacker PQ, Gerstenberger EP, Banks SM, et al. Meta-analysis of ALI and ARDS
trials testing low tidal volumes. Am J Respir Crit Care Med 2002;166:1510-4. In
this controversial analysis, the authors question the validity of the ARDS
network study above, arguing that 1) the mortality benefit resulted from excess
mortality in the traditional arm, 2) the traditional arm did not receive the
standard of care (authors argue the traditional arm received excessively large
tidal volumes), and 3) very low tidal volumes are harmful. This analysis and the
authors' conclusions have been vigorously challenged and rebutted by others. See
links to commentaries at the end of article.
- Mercat A, Richard JC, Vielle B, et al. Positive end-expiratory pressure setting
in adults with acute lung injury and acute respiratory distress syndrome: a
randomized controlled trial. JAMA 2008;299:646-55. The ExPress study compared
low vs. high PEEP in 767 patients with ALI/ARDS receiving low tidal volume
ventilation. In the high-PEEP group, PEEP was adjusted to a target plateau
pressure of 28 to 30 cm H2O regardless of oxygenation while target PEEP in the
minimal distension group was 5 to 9 cm H2O. Mortality at 28 days did not differ,
but the high-PEEP group had a higher median number of ventilator-free days and
required fewer "rescue" interventions such as proning. It appears the greatest
benefit to a high-PEEP strategy is in patients with more severe lung edema, but
whether there is a survival benefit in this subpopulation is still unclear. See
also results of the Lung Open Ventilation Study (LOVS) in the same issue
(Stewart TE et al.).
- Wiedemann HP, Wheeler AP, Bernard GR, et al. Comparison of two fluid-management
strategies in acute lung injury. N Engl J Med. 2006; 354:2564-75. A randomized
study, comparing conservative vs. liberal fluid management (via explicit
protocols) applied over seven days to 1000 patients with acute lung injury.
Although there was no significant difference in the primary outcome of 60-day
mortality, the conservative strategy of fluid management shortened the duration
of mechanical ventilation and ICU stay without increasing nonpulmonary-organ
- Wheeler AP, Bernard GR, Thompson BT, et al. Pulmonary-artery versus central
venous catheter to guide treatment of acute lung injury. N Engl J Med. 2006;
354:2213-24. PAC-guided therapy did not improve survival or organ function but
was associated with more complications than CVC-guided therapy. These results,
along with previous studies of PACs in the MICU population, suggest that the PAC
should not be routinely used for the management of acute lung injury.
- UpToDate has very nice succinct summaries of treatment strategies for Non-Cardiogenic
Pulmonary Edema (i.e. ARDS), Cardiogenic Pulmonary Edema, and Status Asthmaticus.
- Guerin, C et al. Prone positioning in severe ARDS. NEJM 2013;368;2159-68.