Effects of different triggering systems and external PEEP on trigger capability of the ventilator

Patient-controlled positive end-expiratory pressure with neuromuscular disease: effect on speech in patients with tracheostomy and mechanical ventilation support

OBJECTIVE

Communication is a major issue for patients with tracheostomy who are supported by mechanical ventilation. The use of positive end-expiratory pressure (PEEP) may restore speech during expiration; however, the optimal PEEP level for speech may vary individually. We aimed to improve speech quality with an individually adjusted PEEP level delivered under the patient's control to ensure optimal respiratory comfort.

METHODS

Optimal PEEP level (PEEPeff), defined as the PEEP level that allows complete expiration through the upper airways, was determined for 12 patients with neuromuscular disease who are supported by mechanical ventilation. Speech and respiratory parameters were studied without PEEP, with PEEPeff, and for an intermediate PEEP level. Flow and airway pressure were measured. Microphone speech recordings were subjected to both quantitative and qualitative assessments of speech, including an intelligibility score, a perceptual score, and an evaluation of prosody determined by two speech therapists blinded to PEEP condition.

RESULTS

Text reading time, phonation flow, use of the respiratory cycle for phonation, and speech comfort significantly improved with increasing PEEP, whereas qualitative parameters remained unchanged. This resulted mostly from the increase of the expiratory volume through the upper airways available for speech for all patients combined, with a rise in respiratory rate for nine patients. Respiratory comfort remained stable despite high levels of PEEPeff (median, 10.0 cm H2O; interquartile range, 9.5-12.0 cm H₂O).

CONCLUSIONS

Patient-controlled PEEP allowed for the use of high levels of PEEP with good respiratory tolerance and significant improvement in speech (enabling phonation during the entire respiratory cycle in most patients). The device studied could be implemented in home ventilators to improve speech and, therefore, autonomy of patients with tracheostomy.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01479959; URL: clinicaltrials.gov.

Flow triggering added to pressure support ventilation improves comfort and reduces work of breathing in mechanically ventilated patients

PURPOSE

The purpose of this study was to measure the effect of flow triggering (FT), added to pressure support ventilation (PSV), during spontaneous breathing in intubated patients.

MATERIALS AND METHODS

A prospective observational study was conducted at a Comprehensive Cancer Center, University Hospital. Fourteen consecutive critically ill, mechanically ventilated patients on PSV with positive end-expiratory pressure were studied. Flow triggering was added to PSV in spontaneously breathing ventilated patients.

RESULTS

Respiratory rate (f), minute ventilation (Vepsilon), patient work of breathing (WOBp), respiratory drive (P0.1), rapid shallow breathing index (f/Vt), tidal volume (Vt) and a visual analog scale of breathing effort and comfort all improved. There was a large decrease in WOBp and P0.1 when flow triggering was added to PSV (P<.001). There was a moderate decrease in f/V1 during the same procedure (P<.01). Twelve patients felt subjectively better with the intervention.

CONCLUSIONS

Flow triggering offers an excellent complement to PSV because it improves patient comfort and reduces the magnitude of the inspiratory effort as well as the delay time between inspiratory muscle contraction and gas flow. It augments gas exchange at no metabolic cost to the patient while reducing the work of breathing.

Liberation from mechanical ventilation: a decade of progress

Multiple complications associated with mechanical ventilation mandate that clinicians expeditiously define and reverse the pathophysiologic processes that precipitate respiratory failure and then, detect the earliest point that a patient can breathe without the ventilator. Over the past decade, numerous laboratory and clinical studies have been reported that may inform transformation of the "art of weaning" to the science of liberation. We review these studies and use them to formulate a systematic approach to assure early, safe, and successful liberation of patients from mechanical ventilation.