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Ventilation and Oxygenation Management 407

Research vignette, Continued
ventilation I = 76%, P < 0.01) and duration of weaning I = 97%, delays in the recognition of weaning/extubation readiness and
2
2
P < 0.01), which could not be explained by subgroup analyses variation in practice thereby improving weaning outcomes.
based on type of unit or type of approach.
This well-conducted systematic review demonstrated discordant
Conclusion results in 11 trials of protocolised weaning (that included auto-
There is evidence of a reduction in the duration of mechanical mated weaning) when compared to usual care despite an overall
ventilation, weaning, and stay in the intensive care unit when stan- benefit of weaning protocols. The authors postulate this may be
dardised weaning protocols are used, but there is significant het- due to variability in organisational environments in the usual care
erogeneity among studies and an insufficient number of studies arm of trials such as the type of ICU [open vs closed], levels of
to investigate the source of this heterogeneity. Some studies physician and nurse staffing, frequency and structure of ward
suggest that organisational context could influence outcomes, but rounds, patient case-mix, and extent of collaborative interdisciplin-
this could not be evaluated as it was outside the scope of this ary discussion. Unfortunately these contextual elements are fre-
review. quently not sufficiently measured or defined in descriptions of
usual care. Critical care clinicians and administrators need to be
Critique aware of these contextual differences when considering the intro-
Weaning protocols generally include two components: (1) a daily duction of behavioural interventions such as weaning and seda-
assessment of weaning readiness using a list of objective criteria; tion protocols. This is of particular importance in Australia and New
and (2) a spontaneous breathing trial during which the patient is Zealand, as the majority of weaning protocol studies that demon-
evaluated for extubation readiness, and/or an algorithm detailing strate statistically and clinically significant reductions in the dura-
stepwise reductions in ventilatory support prior to extubation tion of mechanical ventilation have been conducted in North
assessment. The aim of this standardised approach is to reduce American ICUs where a very different organisational model exists.

Learning activities
1. What is the rationale for using oxygen therapy in patients with 8. Identify the clinical applications of pressure-volume and flow-
COPD and low SpO 2 ? volume loops.
2. Why is it important to consider the patient’s respiratory rate 9. What are the potential risks of mechanical ventilation as well
and tidal volume when using a low flow (variable flow) oxygen as those related to premature discontinuation of ventilation?
delivery device? Activities 10–15 relate to the case study:
3. How should ETT placement be confirmed? 10. What were the rationales for switching from SIMV-VC to
4. Describe assessment priorities and interventions before and SIMV-PC for Mr Smith on day 2?
after extubation. 11. What is the current research evidence on the benefits and dis-
5. What are the indications and relative and absolute contraindi- advantages of volume versus pressure ventilation?
cations for NIV? 12. Why was semirecumbent positioning a priority for Mr Smith?
6. Familiarise yourself with the ventilators in your unit. Confirm 13. Why do you think FiO 2 was weaned before PEEP?
you have a thorough understanding of the function and 14. What is the current research evidence for the use, benefits and
purpose of all ventilator settings. disadvantages of muscle relaxants in the critically ill?
7. Ensure you have a clear understanding of ventilator mode 15. Why was NIV beneficial for Mr Smith?
terminology.

ONLINE RESOURCES NHS Institute for Innovation and Improvement, http://www.institute.nhs.uk/
safer_care/general/human_factors.html
American Association for Respiratory Care, http://www.aarc.org/resources/ Thoracic Society of Australia and New Zealand, http://www.thoracic.org.au/
Anaesthesia UK, http://www.frca.co.uk/default.aspx Vent World, http://www.ventworld.com/
Australian and New Zealand Intensive Care Society, www.anzics.com.au/
safety-quality?start=2
ARDS network, http://www.ardsnet.org/ FURTHER READING
Canadian Society of Respiratory Therapists, Respiratory Resource, http://www.
respiratoryresource.ca/ Canadian Critical Care Trials Group/Canadian Critical Care Society Noninvasive
College of Intensive Care Medicine of Australia and New Zealand, www.cicm.org.au/ Ventilation Guidelines Group. Clinical practice guidelines for the use of non-
policydocs.php invasive positive-pressure ventilation and noninvasive continuous positive
Covidien education resources, http://www.nellcor.com/educ/OnlineEd.aspx airway pressure in the acute care setting. CMAJ 2011; 183(3): E195–214.
Critical Care Medicine Tutorials, http://www.ccmtutorials.com/ Esan A, Hess DR, Raoof S, George L, Sessler CN. Severe hypoxemic respiratory
Fisher and Paykel Resource Centre, http://www.fphcare.com/respiratory-acute- failure. Part 1: ventilatory strategies. Chest 2010: 137(6): 1203–16.
care/resource-library.html Lacherade JC, De Jonghe B, Guezennec P, Debbat K, Hayon J et al. Intermittent
Intensive Care Coordination and Monitoring Unit, http://intensivecare.hsnet. subglottic secretion drainage and ventilator-associated pneumonia: a multi-
nsw.gov.au/ center trial. Am J Respir Crit Care Med 2010; 182(7): 910–17.