Table 2.
Variables associated with an increase in diaphragm function* and a decrease or no change in diaphragm function between the two measurements
| Increase in diaphragm function n = 40 |
Decrease or no change in diaphragm function n = 52 |
p | |
|---|---|---|---|
| Time between intubation and second measure, days | 5 (3–6) | 4 (2–6) | 0.163 |
| Time between 2 measures, days | 4 (3–5) | 3 (1–5) | 0.134 |
| Sepsis at inclusion, n (%) | 29 (73) | 22 (42) | 0.004 |
| Age, years | 61 (49–72) | 63 (54–71) | 0.425 |
| Male sex, n (%) | 22 (55) | 34 (65) | 0.312 |
| Body mass index, kg m−2 | 24 (21–25) | 25 (23–28) | 0.036 |
| SAPS2 at inclusion | 58 (35–66) | 54 (45–64) | 0.831 |
| SOFA at inclusion | 9 (5–11) | 10 (7–12) | 0.301 |
| Comorbidities, n (%) | |||
| Active smoking | 20 (50) | 25 (48) | 0.855 |
| COPD | 9 (23) | 12 (23) | 0.948 |
| Diabetes | 11 (28) | 14 (27) | 0.951 |
| Cirrhosis | 7 (18) | 10 (19) | 0.832 |
| Primary reason for ventilation, n (%) | |||
| Acute respiratory failure | 28 (70) | 27 (52) | 0.080 |
| Shock | 5 (13) | 7 (13) | 0.892 |
| Cardiac arrest | 1 (3) | 6 (12) | 0.105 |
| Coma | 6 (15) | 12 (23) | 0.333 |
| Biological variables | |||
| PCT at inclusion, ng/ml | 3 (0.3–20) | 1.7 (0.9–7.3) | 0.909 |
| Blood lactate at inclusion, mmol.l−1 | 1.8 (1.2–3.2) | 2.1 (1.4–2.9) | 0.838 |
| PaO2/FiO2 at inclusion | 230 (160–305) | 226 (162–306) | 0.940 |
| PaO2/FiO2 at second measure | 280 (202–327) | 260 (220–333) | 0.990 |
| Sedation | |||
| Hypnotics at inclusion (propofol or midazolam), n (%) | 33 (100) a | 44 (100) c | 1.000 |
| Sufentanyl at inclusion, n (%) | 29 (88) a | 38 (86) c | 1.000 |
| Hypnotics at second measure (propofol or midazolam), n (%) | 19 (56) b | 16 (40) d | 0.130 |
| Sufentanyl at second measure, n (%) | 9 (26) b | 14 (35) d | 0.808 |
| Organ support | |||
| Vasopressors, n (%) | 28 (70) | 38 (73) | 0.745 |
| Diaphragm function | |||
| Ptr,stim at inclusion, cmH2O | 5.8 (4.0–8.0) | 10.2 (7.0–14.3) | < 0.001 |
| Ptr,stim at second measure, cmH2O | 10.5 (7.0–12.5) | 6.9 (4.5–9.4) | 0.002 |
| Absolute change in Ptr,stim, cmH2O | 3.4 (1.8–4.8) | – 1.5 (– 4.9 to – 0.6) | < 0.001 |
| Relative change in Ptr,stim, % | 59 (32–78) | – 19 (– 43 to – 7) | < 0.001 |
| End-expiratory diaphragm thickness at inclusion, mm | 2.3 (1.9–2.9) e | 2.1 (1.7–2.5) f | 0.484 |
| End-expiratory diaphragm thickness at second measure, mm | 1.9 (1.5–2.3) e | 2.0 (1.7–2.2) f | 0.565 |
Categorical variables are expressed as absolute value (%) and continuous variables as median (interquartile range)
* Increase in diaphragm function is defined as an increase > 10% of the change of endotracheal tube pressure induced by bilateral phrenic nerve stimulation during airway occlusion (Ptr,stim) between first measure at inclusion and second measure after switch to pressure support mode
SOFA: Sepsis-related Organ Failure Assessment; SAPS 2: New Simplified Acute Physiology Score; COPD: chronic obstructive pulmonary disease; PCT: procalcitonin; PaO2/FiO2: partial arterial oxygen tension on inspired oxygen fraction ratio; Ptr,stim: endotracheal tube pressure induced by bilateral phrenic nerve stimulation during airway occlusion
a Data available for 33/40 patients, b data available for 34/40 patients
c Data available for 44/52 patients, d data available for 40/52 patients
e Data available for 28/40 patients
f Data available for 30/52 patients