Potentially harmful effects of inspiratory synchronization during pressure preset ventilation
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Pressure preset ventilation (PPV) modes with set inspiratory time can be classified according to their ability to synchronize pressure delivery with patient’s inspiratory efforts (i-synchronization). Non-i-synchronized (like airway pressure release ventilation, APRV), partially i-synchronized (like biphasic airway pressure), and fully i-synchronized modes (like assist-pressure control) can be distinguished. Under identical ventilatory settings across PPV modes, the degree of i-synchronization may affect tidal volume (V T), transpulmonary pressure (P TP), and their variability. We performed bench and clinical studies.
In the bench study, all the PPV modes of five ventilators were tested with an active lung simulator. Spontaneous efforts of −10 cmH2O at rates of 20 and 30 breaths/min were simulated. Ventilator settings were high pressure 30 cmH2O, positive end-expiratory pressure (PEEP) 15 cmH2O, frequency 15 breaths/min, and inspiratory to expiratory ratios (I:E) 1:3 and 3:1. In the clinical studies, data from eight intubated patients suffering from acute respiratory distress syndrome (ARDS) and ventilated with APRV were compared to the bench tests. In four additional ARDS patients, each of the PPV modes was compared.
As the degree of i-synchronization among the different PPV modes increased, mean V T and P TP swings markedly increased while breathing variability decreased. This was consistent with clinical comparison in four ARDS patients. Observational results in eight ARDS patients show low V T and a high variability with APRV.
Despite identical ventilator settings, the different PPV modes lead to substantial differences in V T, P TP, and breathing variability in the presence spontaneous efforts. Clinicians should be aware of the possible harmful effects of i-synchronization especially when high V T is undesirable.
KeywordsPressure preset ventilation ARDS APRV BIPAP
Airway pressure release ventilation
Acute respiratory distress syndrome
Biphasic positive airway pressure
Coefficient of variation
Inspiratory to expiratory ratio
Intensive care unit
Pressure assist control
Positive end-expiratory pressure
Pressure preset ventilation
Spontaneous respiratory rate
Minute ventilation attributed to spontaneous breathing activity
Total minute ventilation
The authors are grateful to Prof. Jordi Mancebo for the critical appraisal of the manuscript. This study was supported by grants from the Société de Réanimation de Langue Française (SRLF) for Nathalie Rey and the Coordenação de Aperfeioçoamento de Pessoal de Nível Superior (CAPES)-Ministry of Education, Brazil (Bolsita da CAPES, Proc. no. BEX-18231-12-8) for Ricardo Cordioli.
Conflicts of interest
We hereby declare that we have no conflict of interest directly related to the manuscript. LB’s research laboratory received grants from several ventilator companies for specific research projects (Maquet, NAVA; Covidien, PAV; Drager, SmartCare; Philips Respironics, NIV; General Electric, FRC).
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