Refractory ineffective triggering during pressure support ventilation: effect of proportional assist ventilation with load-adjustable gain factors

Annals of Intensive Care

Table 3 Physiological measurements under PSV and PAV+

	PSV	PAV+	Δ (PAV+ – PSV)	p
SpO₂, %	96 [93–97]	96 [94–98]	− 1 [− 1–0]	0.629
PaO₂/FiO₂, mm Hg	228 [209–257]	213 [203–298]	− 14 [− 28–60]	0.820
PaCO₂, mm Hg	36 [33–41]	45 [34–55]	8 [1–12]	0.032
Heart rate, /min	103 [89–109]	101 [96–108]	2 [− 1–8]	0.181
MAP, mm Hg	89 [79–94]	92 [88–98]	5 [0–12]	0.032
Lactate, mmol/L	1 [0.9–1.1]	0.9 [0.8–1]	− 0.1 [− 0.2–0]	0.611
Inspiratory delay, ms	230 [200–290]	240 [180–290]	− 30 [− 43–9]	0.289
Ventilator insufflation time, s	1 [0.9–1.2]	0.8 [0.7–1.2]	− 0.1 [− 0.3–0.2]	0.519
Tidal volume
mL	385 [322–485]	332 [237–398]	− 71 [− 176–2]	0.052
mL/kg of PBW	6.5 [5.5–8.2]	5.6 [4.1–7.2]	− 1.0 [− 3.0–0.0]	0.045
Respiratory rate
Ventilator, breaths/min	26 [22–27]	35 [29–40]	7 [3–14]	0.007
Patient, breaths/min	41 [28–46]	39 [30–43]	− 2 [− 4–1]	0.264
Minute ventilation, L/min	9.1 [8.3–11.8]	11 [8.8–12.5]	0.7 [− 1.9–2.1]	0.791
Ventilatory ratio*	2.1 [1.41–2.3]	1.74 [1.29–2.65]	0.1 [− 0.1–0.5]	.0515
Pmus_peak, cmH₂O	9.1 [4.7–11.4]	11.6 [9.6–13.2]	3.1 [− 0.1–5.7]	0.06
Total PTPes, cmH₂O/s/min	107 [79–131]	149 [129–170]	43 [1–89]	0.092
Effective PTPes, cmH₂O/s/min	84 [70–104]	135 [127–161]	54 [20–84]	0.016
Ineffective PTPes, cmH₂O/s/min	8 [3–30]	2 [1–6]	− 8 [− 28–− 2]	0.012
Intrinsic PEEP, cmH₂O	3.9 [3–4.1]	5.6 [2.1–7.2]	0.5 [− 1.3–2.5]	0.380

PSV: Pressure support ventilation with the lowest tolerated pressure support level; PAV+: proportional assist ventilation with load-adjustable gain factors with the gain adjusted to target a peak muscle pressure between 5 and 10 cmH₂O; the Δ (PAV+-PSV) column represents the median [interquartile range] of individual differences between PAV+ and PSV. MAP: mean arterial pressure; PBW: predicted body weight; Pmus_peak: peak muscle pressure; PTPes: esophageal pressure–time product; PEEP: positive end-expiratory pressure. Note that intrinsic PEEP was measured as the drop in esophageal pressure before increase in flow, which could also capture expiratory muscles relaxation. Effective PTPes denotes PTPes recorded during respiratory efforts that effectively trigger an insufflation from the ventilator; ineffective PTPes denotes PTPes recorded during ineffective triggerings. * Ventilatory ratio is defined as (minute ventilation × PaCO₂)/((predicted body weight/10) × 37.5))