Mechanical Insufflation-Exsufflation Implementation and Management, Aided by Graphics Analysis.

Mechanical insufflation-exsufflation (MIE) facilitates airway clearance to mitigate respiratory infection, decompensation, and ultimately the need for intubation and placement of a tracheostomy tube. Despite widespread adoption as a respiratory support intervention for motor neuron disease, muscular dystrophy, spinal cord injury, and other diseases associated with ventilatory pump failure and ineffective cough peak flow, there is debate in the clinical community about how to optimize settings when MIE is implemented. This article will demonstrate the clinical utility of MIE graphics in titrating the initial MIE settings, guiding upper airway and lung protective strategies and providing insight to clinicians for ongoing clinical management.

Patient ventilator asynchrony in critically ill adults: frequency and types.

BACKGROUND: Patient ventilator asynchrony (PVA) occurs frequently, but little is known about the types and frequency of PVA. Asynchrony is associated with significant patient discomfort, distress and poor clinical outcomes (duration of mechanical ventilation, intensive care unit and hospital stay). METHODS: Pressure-time and flow-time waveform data were collected on 27 ICU patients using the Noninvasive Cardiac Output monitor for up to 90 min per subject and blinded waveform analysis was performed. RESULTS: PVA occurred during all phases of ventilated breaths and all modes of ventilation. The most common type of PVA was Ineffective Trigger. Ineffective trigger occurs when the patient's own breath effort will not trigger a ventilator breath. The overall frequency of asynchronous breaths in the sample was 23%, however 93% of the sample experienced at least one incident of PVA during their observation period. Seventy-seven percent of subjects experienced multiple types of PVA. CONCLUSIONS: PVA occurs frequently in a variety of types although the majority of PVA is ineffective trigger. The study uncovered previously unidentified waveforms that may indicate that there is a greater range of PVAs than previously reported. Newly described PVA, in particular, PVA combined in one breath, may signify substantial patient distress or poor physiological circumstance that clinicians should investigate.

Using ventilator graphics to identify patient-ventilator asynchrony.

Patient-ventilator interaction can be described as the relationship between 2 respiratory pumps: (1) the patient's pulmonary system, which is controlled by the neuromuscular system and influenced by the mechanical characteristics of the lungs and thorax, and (2) the ventilator, which is controlled by the ventilator settings and the function of the flow valve. When the 2 pumps function in synchrony, every phase of the breath is perfectly matched. Anything that upsets the harmony between the 2 pumps results in asynchrony and causes patient discomfort and unnecessarily increases work of breathing. This article discusses asynchrony relative to the 4 phases of a breath and illustrates how asynchrony can be identified with the 3 standard ventilator waveforms: pressure, flow, and volume. The 4 phases of a breath are: (1) The trigger mechanism (ie, initiation of the inspiration), which is influenced by the trigger-sensitivity setting, patient effort, and valve responsiveness. (2) The inspiratory-flow phase. During both volume-controlled and pressure-controlled ventilation the patient's flow demand should be carefully evaluated, using the pressure and flow waveforms. (3) Breath termination (ie, the end of the inspiration). Ideally, the ventilator terminates inspiratory flow in synchrony with the patient's neural timing, but frequently the ventilator terminates inspiration either early or late, relative to the patient's neural timing. During volume-controlled ventilation we can adjust variables that affect inspiratory time (eg, peak flow, tidal volume). During pressure-controlled or pressure-support ventilation we can adjust variables that affect when the inspiration terminates (eg, inspiratory time, expiratory sensitivity). (4) Expiratory phase. Patients with obstructive lung disease are particularly prone to developing intrinsic positive end-expiratory pressure (auto-PEEP) and therefore have difficulty triggering the ventilator. Bedside evaluation for the presence of auto-PEEP should be routinely performed and corrective adjustments made when appropriate.