Angie Kriner, BHA, RRT, Clinical Education Specialist, Anne Arundel Medical Center, Annapolis, MD
Caring for critically ill patients is a complex process, particularly when urgent interventions are necessary. Simple but critical tasks may be overlooked while clinicians and providers are distracted by the most obvious threat to mortality.
For this reason, among others, the implementation of evidence-based, protocolized medicine has become increasingly common in the ICU. Protocols provide a framework for clinicians to operate within, removing guesswork and decreasing the burden on clinicians as algorithms are followed and care is directed. If implemented appropriately, the use of protocols, checklists, and guidance statements can provide safer, more efficient care and drive improved patient outcomes.1
Examples of such in the care of critically ill patients range from the sepsis and interdisciplinary A-F bundles2,3 to mechanical ventilation, weaning, and bronchodilator protocols. However, the risk or disadvantage of treating patients similarly is the loss of individualization of care. Emerging to intersect with protocol-guided care is personalized or precision medicine. Trends in patient-centered or personalized medicine are emerging for many diseases, but also specifically with regards to the management of mechanical ventilation.
What are we missing?
Recently published guidelines for the mechanical ventilation management of patients with the acute respiratory distress syndrome (ARDS) strongly recommend the use of low tidal volume/low pressure strategies and prone positioning.4 These recommendations, based on the classic 2001 ARMA trial5 and the more recent 2013 PROSEVA study,6 which showed a significant reduction in mortality and other clinically important outcomes, are the foundation for widely accepted mechanical ventilation strategies and protocols.
However, adherence to these widely referenced strategies and subsequent outcomes was examined in a “real-world” epidemiologic report card of ARDS management, and the results were dismal.7 Recognition of ARDS, appropriate dosing of tidal volume, routine assessment of plateau pressure (PPLAT), provision of moderate PEEP, and the use of prone positioning did not occur despite meeting ARDS inclusion criteria. Although strong evidence points to the efficacy of those interventions in reducing mortality, the assessment in LungSafe demonstrates the challenge in identifying the indications for and the implementation of ARDS protocols.
But even if the mortality reported in the literature had been translated to clinical practice, the mortality for ARDS with our best, most regimented protocols remains 16-32%. Which begs the question: what are we missing?
Investigators retrospectively analyzed data from a large sample of patients with ARDS, examining individual components of data and their association with outcomes.8 Indices included PPLAT, low vs. high PEEP, and driving pressure (ΔP=VT/CRS), among others. Driving pressure (∆P) was the most closely associated variable with survival, namely a ∆P ≤ 14 cmH2O.
Bedside evaluation of ∆P is the difference between the PPLAT and the end expiratory alveolar pressure (PEEPTOT). Although not yet proven to be causal in nature in a prospective randomized controlled trial, individualized adjustments to mechanical ventilator parameters (tidal volume and the PEEP) that target a ∆P ≤ 14 cmH2O may have a significant impact on outcomes.
A recent publication by Goligher and colleagues further explored these efforts to decrease ∆P.9 The mortality benefit of reducing tidal volume was only evident in patients with an increased elastance. Mortality was only reduced if a reduction in tidal volume resulted in a correlating decrease in ∆P below 14 cmH2O; there was no such benefit of reducing tidal volume if the ∆P was already below 14 cmH2O.
Patients with etiologies that significantly contribute to a decreased chest wall compliance may also benefit from individualization of mechanical ventilator settings guided by transpulmonary pressure. The EpVent2 study10 showed no difference in primary outcomes between transpulmonary pressure guided PEEP and PEEP set according to the high PEEP/FiO2 table. However, when translated to clinical practice, the use of the high PEEP/FiO2 table calls for a PEEP setting of 20-24 cmH2O, as FiO¬2 requirements go above 0.70.
Although not studied, one could ponder the probability of their own institution’s use of PEEP > 20cmH2O within a therapist driven-protocol in the absence of a detailed assessment of the chest wall and lung mechanics. Beyond the use of transpulmonary pressure or a PEEP/FiO2 table, the therapeutic intention of PEEP is to recruit lung units. If the increase in PEEP does not result in recruitment and increase in lung volume, the risk of volutrauma and injury may outweigh any benefit.
Assessing an individual patient’s potential for lung recruitment at the bedside11 may be an additional tool for identifying a patient’s potential benefit from changes in mechanical ventilator settings, in this case PEEP, as opposed to a change that is arbitrary in nature. Advanced monitoring tools such as electrical impedance tomography (EIT), although not yet studied with respect to guiding mechanical ventilation settings, may also emerge as useful bedside monitoring tools for assessing an individual’s response to changes in mechanical ventilation settings.
A balanced approach
Improving mechanical ventilation practice and outcomes for patients with ARDS may involve a combination of approaches, both protocolized and personalized. Diagnosis of ARDS requires vigilance from clinicians to institute those interventions that are proven to reduce mortality.
Institution of protocolized care in ARDS patients should be a starting point, with clinicians led by respiratory therapists applying their technical expertise and advanced interpretation of lung physiology. Individualized patient treatment approaches are necessary due to the broad heterogeneous nature of ARDS and mortality that remains persistently high despite interventions supported by high level data.
Kenneth Miller, MEd, RRT, RRT-ACCS, FAARC, Education Coordinator, Lehigh Valley Health Network, Allentown, PA
As I creep towards the closure of my 46 year career as a respiratory therapist, I would like to reflect on an issue that has been in the forefront of my thoughts throughout my career.
Historically, one of the hallmarks of being a respiratory therapist charged with managing patients on mechanical ventilators is performing a ventilator check. This “check” is often viewed as a task to be completed every four hours, and it is often performed mindlessly, without much thought or detail. Often a ventilator check is done to fulfill a legal credentialing agency’s requirements to ensure patient safety. Even the AARC allocates a defined amount time to be utilized for each ventilator check, as if all ventilator checks are truly equal.
Fortunately, many respiratory therapists like myself have never viewed the ventilator check as a task. Rather, it is an opportunity to optimize the patient-ventilator relationship, adjust and maintain ventilatory parameters, maximize adequate gas exchange, reduce the risk of ventilator-induced trauma, and assess for the potential of ventilatory liberation.
Time for a new name
For the past several decades, I have advocated for changing the term “ventilator check” to “patient-ventilator assessment.” A patient-ventilator assessment is the perfect time to assess the patient-ventilator relationship, not just document parameters and perform required tasks.
Therapists have an opportunity to diagnosis the ventilator parameters and mode set to meet the patient’s ventilator requirements and facilitate clinical endpoints. In order to assess this, a thorough assessment of ventilator waveforms, synchrony, and gas exchange is required. During the ventilator assessment the RRT should be asking which ventilator parameters should be changed and which interventions can achieve the desired clinical endpoints.
Questions to ask oneself include, but are not limited to:
Ventilator alarms serve as a good example
A ventilator assessment is performed not just to document or validate an electronic record but to ensure that the goals of mechanical ventilation are being achieved and the ventilator is set to maximize a positive patient outcome and safety.
For example, ventilator alarms should be set to guarantee the patient is safe during mechanical ventilation and to alert bedside clinicians of changing patient clinical status. However, the setting of ventilator alarms is often just a generic process, where all ventilated patients have preset values; for example, low minute ventilation might be preset to four liters per minute.
In this scenario, the low minute ventilation alarm can be adjusted to 80% of the actual patient’s minute ventilation. Understanding that the ventilator alarm settings need to be balanced with preventing alarm fatigue,1 by judiciously setting mechanical ventilator alarms to the current, specific clinical status of each patient and adjusting them as needed, the goals of both patient safety and the prevention of alarm fatigue can be achieved.
Maximizing our role
Moving forward as a profession, we must jettison the concept of the “ventilator check” and engage in the concept of “patient-ventilator assessments” to maximize our role in the optimization of patient outcomes and add value to our role at the bedside. The value-added respiratory therapist is not a taskmaster slave but a caregiver that helps direct and shape the patient’s outcome.2
Respiratory therapy as a profession is at a crossroads. Performing ventilator assessments will strengthen and guarantee our critical role at the patient’s bedside.
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