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The following is a summary of “Post-insufflation diaphragm contractions in patients receiving various modes of mechanical ventilation,” published in the September 2024 issue of Critical Care by Rodrigues et al.

Post-insufflation diaphragm contractions (PIDCs) during mechanical ventilation could be dangerous and may occur with different modes of assisted ventilation, especially with reverse-triggering.

Researchers conducted a retrospective study investigating the association between PIDCs, ventilator settings, and patient characteristics in mechanically ventilated patients with hypoxemic respiratory failure.

They collected 1-hour recordings of diaphragm electromyography (EAdi), airway pressure, and flow once daily for up to 5 days, from intubation until complete recovery of diaphragm activity or death. Each breath was classified as mandatory (without reverse triggering), reverse triggering, or patient-triggered. Reverse triggering was categorized on EAdi timing about the ventilator cycle or instances leading to breath stacking. Measurements of EAdi timing (onset, offset), peak, and neural inspiratory time (Ti_neuro) were taken breath-by-breath and compared to the ventilator’s expiratory time. A multivariable logistic regression model was used to explore factors independently associated with PIDCs, EAdi timing, amplitude, Ti_neuro, ventilator settings, and the Acute Physiology and Chronic Health Evaluation II (APACHE II).

The results showed that 47 patients (median [25%-75% IQR] age: 63 [52–77] years, BMI: 24.9 [22.9–33.7] kg/m², 49% male, APACHE II: 21 [19–28]) contributed an average of 2 ± 1 recordings, totaling 183,962 breaths and PIDCs occurred in 74% of reverse-triggering breaths, 27% of pressure support breaths, 21% of assist-control breaths, with  5% of Neurally Adjusted Ventilatory Assist (NAVA) breaths, PIDCs were linked to a higher EAdi peak (odds ratio [OR] [95% CI] 1.01 [1.01; 1.01]), longer Ti_neuro (OR 37.59 [34.50; 40.98]), shorter ventilator inspiratory time (OR 0.27 [0.24; 0.30]), higher peak inspiratory flow (OR 0.22 [0.20; 0.26]), and smaller tidal volumes (OR 0.31 [0.25; 0.37]) (all P≤ 0.008). The NAVA was associated with the absence of PIDCs (OR 0.03 [0.02; 0.03]; P<0.001). Reverse triggering showed lower EAdi peaks than pressure support breaths and was associated with smaller tidal volumes and shorter set inspiratory times compared to assist-control breaths (all P< 0.05). Reverse triggering that led to breath stacking was characterized by higher peak EAdi and longer Ti_neuro, with smaller tidal volumes than all other reverse-triggering phenotypes (all P< 0.05).

They concluded that PIDCs and reverse triggering phenotypes were associated with modifiable factors, including ventilator settings, suggesting that proportional modes like NAVA could potentially eliminate PIDCs.

Source: ccforum.biomedcentral.com/articles/10.1186/s13054-024-05091-y