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Table 2 Physiological variables and diaphragm shear modulus under the different ventilatory conditions

From: Ultrasound shear wave elastography for assessing diaphragm function in mechanically ventilated patients: a breath-by-breath analysis

Variables Condition of ventilation
PS+25% PS PS-25% PSZEEP SBT Start SBT End
Pressure support, cmH2O 13 (12–16) 10 (10–13) 8 (7–9) 10 (10–13) 0 0
PEEP, cmH2O 5 (5–5) 5 (5–5) 5 (5–5) 0 0 0
VT, mL/kg 5.7 (4.9–7.4)def 4.9 (4.2–6.2)ef 4.6 (4.1–5.4)ace 4.8 (3.8–6.8)ae 3.3 (3.1–4.9)abcd 3.9 (3.2–5.4)ab
Respiratory rate, cycles/min 19 (13–25) 21 (17–27) 23 (18–29) 24 (17–30) 24 (18–33)ab 26 (22–32)a
Inspiratory time, s 1.1 (1.0–1.6) 1.0 (0.9–1.3) 1.0 (0.9–1.2)a 1.0 (0.8–1.3) 1.2 (0.9–1.3)c 1.1 (0.9–1.3)a
Expiratory time, s 2.0 (1.5–2.8) 1.8 (1.3–2.4) 1.5 (1.2–2.1) 1.5 (1.2–2.2) 1.3 (1.0–1.8)ab 1.3 (1.0–1.6)
Inspiratory duty cycle 0.40 (0.37–0.45)e 0.41 (0.36–0.45) 0.39 (0.37–0.43)e 0.41 (0.38–0.43)e 0.45 (0.43–0.50)acd 0.45 (0.41–0.47)
Minute ventilation (l.min−1) 7.8 (5.8–10.4) 8.1 (6.0–10.1) 7.9 (6.1–9.5) 8.2 (5.8–9.4) 6.4 (5.2–9.0) 7.5 (5.5–8.6)
ΔPdi, cmH2O 3.9 (1.6–9.4)ef 3.2 (1.3–8.9)ef 4.3 (2.5–12.9)ef 5.8 (2.8–10.5)ef 10.3 (5.6–21.8)abcd 10.0 (7.1–23.5)abcd
PTPdi, cmH2O.s/breath 2.9 (0.8–6.7)ef 1.5 (0.7–4.1)ef 3.4 (1.3–6.9)ef 3.5 (1.8–6.4)ef 9.2 (2.7–13.7)abcd 7.4 (3.6–11.4)abcd
PTPdi, cmH2O.s/min 42 (17–131)ef 33 (16–137)ef 78 (23–128)ef 78 (34–167)f 188 (66–369)abc 178 (103–297)abcd
ΔPes, cmH2O − 1.7 (− 8.5 to − 0.9)ef − 1.7 (− 9.0 to − 0.9)ef − 2.9 (− 12.2 to − 1.9)ef − 4.8 (− 8.8 to − 2.8)ef − 11.3 (− 18.7 to − 8.6)abcd − 10.6 (− 23.5 to − 9.3)abcd
ΔPga, cmH2O 0.9 (0.2–2.3) 1.1 (0.2–1.9) 1.0 (0.5–2.3) 0.9 (0.3–2.4) 0.4 (0.0–1.3) 0.2 (0.0–1.0)
ΔSMdi, kPa 5.5 (3.8–9.0)ef 5.4 (3.5–8.8)ef 7.0 (5.8–8.6)ef 7.7 (4.0–11.8)ef 12.2 (7.7–14.3)abcd 7.5 (4.8–13.1)abcd
  1. Results are shown as median (Q1–Q3). PEEP, positive end-expiratory pressure; VT, tidal volume; ΔPdi, inspiratory change in transdiaphragmatic pressure; PTPdi, pressure–time product of Pdi; ΔPes, inspiratory changes in esophageal pressure; ΔPga, inspiratory changes in gastric pressure; ΔSMdi, inspiratory change in diaphragm shear modulus assessed using ultrasound shear wave elastography; PS, pressure support ventilation with baseline inspiratory support and positive end-expiratory pressure; PS+25%, PS with inspiratory pressure support increased by 25%; PS−25%, PS with inspiratory pressure support decreased by 25%; PSZEEP, PS with baseline inspiratory support and zero end-expiratory pressure; SBT, spontaneous breathing trial. a, significantly different from PS+25%; b, Significantly different from PS; c, significantly different from PS−25%; d, significantly different from PSZEEP; e, significantly different from the start of the SBT; f, significantly different from the end of the SBT; all p < 0.05