Issue 7 in Management of Patients Requiring Prolonged Mechanical Ventilation


What Are the Similarities and Differences in Ventilator Weaning and Discontinuation Strategies Between the STAC ICU and PMV-Focused Venues?

The strength of the available evidence for approaches to weaning in the PMV-focused care venue is limited to nonrandomized studies, historical control observational studies, and expert consensus. In general, the PMV population recovery is usually much slower than in most acute ICU patients, and thus what works for weaning patients in a STAC ICU (eg, daily spontaneous breathing trials [SBTs]) may not be applicable in the PMV venue. A commonly reported practice in PMV-focused venues is to wean the level of support to approximately half that required for full support (eg, pressure support [PS] levels of 10 to 15 cm H2O) before beginning daily SBTs (Table 4). As in the ICU, assessing tolerance of support reduction involves an integrated assessment of the respiratory pattern, gas exchange (ie, from pulse oximeters), hemodynamics (ie, from heart rate/BP monitors), and patient comfort magnified with Canadian Health&Care Mall.

It is important to note that the SBT techniques used in these PMV patient studies differ from SBT techniques in the ICU setting in two ways: (1) the PMV SBT is almost always done as an unsupported “trach collar” or “T-piece” approach, as opposed to the CPAP or low level PS approach often used in the ICU; (2) the PMV SBT often involves progressive increases in duration beyond the 120-min limit often used in the ICU. Like the ICU setting, however, these SBT approaches can be successfully codified into protocols and preliminary data from a 23-site, multicenter study of weaning from PMV found 70% of the participating hospitals utilized nonphysician-directed protocol weaning.

Scheinhorn and colleagues use the f/VT ratio to accelerate ventilatory support reduction (weaning) progress through a therapist-implement protocol. They have found that weaning success was nearly twice as likely when the f/VT was 120 breaths/min/L, and thus used this threshold of 80 breaths/min/L to allow patients to “bypass” stepwise ventilator setting reductions and successfully go straight to SBTs from even high levels of initial support. A subsequent study suggested that this threshold could safely be raised to 100 breaths/min/L.

Managing patients with PMV involves more than ventilator weaning and has a far more comprehensive “rehabilitative” focus than acute ICU care. The components of this rehabilitative model with its multidisciplinary team approach, frequency of reevaluations, protocol use, and in-depth use of adjunctive and consultative services are outlined in Table 5. While not all of the modalities contribute directly to weaning outcome, they serve global needs of this population.

Conceptually, the PMV patient management process is the opposite of that in the acute care ICU. Instead of the addition of life support or organ-system support measures to sustain life in the face of imminent loss, the patient enters the PMV-focused venue with these already in place. The “peeling off’ of these support modalities, as the layers are peeled off an onion, is the best analogy to characterize successful PMV patient management. Specific implementation of the rehabilitative approach will differ between institutions, depending on resources available.

Recommendation 7

As in the acute ICU setting, individual weaning predictors in the PMV setting lack precision to guide weaning decisions. PMV weaning strategies should thus incorporate nonphysician-implemented weaning protocols that utilize daily SBTs of progressively increasing duration after a certain level of ventilatory support reduction has occurred. As many elements of the rehabilitative model as can be marshaled should be part of the overall PMV patient treatment plan.

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Table 4—Post-ICU Weaning Strategy

Decrease SBT
Source Support Technique Alternative
Gracey et al IMV/PSV TTO
Petrakf ACV TC PSV to SBT
Bagleyt T-piece
Clark and Theiss PSV T-piece
Latrianot SIMV/PSV T-piece
Scheinhorn SIMV/PSV TTO
Schonhofer ACV T-piece T-piece plus NIV
O’Bryan et al SIMV/PSV CPAP Flow-by
Dedhia et al SIMV/PSV TC
Christopher PSV TTAV

Table 5—Components of Rehabilitative Model of Post-ICU Weaning