Table 2.
Physiologic variables at HFNC initiation and 12 h of HFNC onset.
| Parameters | All patients (n = 324) | HFNC success (n = 177) | HFNC failure (n = 147) | p-value success vs. failure |
|---|---|---|---|---|
| Heart rate at HFNC initiation | 88.8 ± 16.3 | 87.0 ± 13.8 | 91.0 ± 18.7 | 0.0121 |
| Systolic arterial pressure at HFNC initiation | 129.2 ± 17.4 | 128.3 ± 17.0 | 130.3 ± 17.8 | 0.1612 |
| Arterial blood gas analysis at HFNC initiation | ||||
| pH | 7.47 ± 0.05 | 7.46 ± 0.04 | 7.47 ± 0.07 | 0.1103 |
| Paco2, mm Hg | 34.3 ± 7.7 | 34.9 ± 6.5 | 33.5 ± 9.1 | 0.0106 |
| , mmol/L | 25.1 ± 5.4 | 25.6 ± 4.8 | 24.3 ± 6.1 | 0.1430 |
| Pao2/Fio2, mm Hg | 141.1 [115.6–188.9] | 151.2 [122.8–199.2] | 129.6 [100.0–163.4] | <0.001 |
| <200 mm Hg | 174 (79.8%) | 96 (75.0%) | 78 (86.7%) | 0.025 |
| Respiratory parameters at HFNC initiation | ||||
| Spo2 | 86 [80–90] | 88 [83–92] | 84 [75–89] | <0.001 |
| Spo2/Fio2 | 108.7 [91.6–143.3] | 121.4 [100.0–150.0] | 97.8 [85.4–112.5] | <0.001 |
| RR (beats per minute) | 25 [22–30] | 24 [22–30] | 26 [22–30] | 0.1319 |
| ROX index | 4.3 [3.4–5.5] | 4.9 [3.8–6.1] | 3.8 [3.0–4.7] | 0.0001 |
| After HFNC treatment | ||||
| Spo2 | 93 [90–96] | 95 [92-96] | 92 [89–94] | <0.001 |
| Spo2/Fio2 | 117.5 [105.0–141.0] | 134.2 [117.5–158.3] | 108.7 [94.6–116.3] | <0.001 |
| RR (beats per minute) | 22 [21–24] | 22 [20–24] | 23 [22–25] | <0.001 |
| Flow (L/min) | 55.0 [50.0–60.0] | 50.0 [50.0–60.0] | 60.0 [50.0–60.0] | 0.0005 |
| ROX index | 5.2 [4.6–6.4] | 5.9 [5.0–7.5] | 4.8 [4.1– 5.3] | <0.001 |
| Length of HFNC, median [IQR], days | 6.0 [3.0–11.0] | 10.0 [7.0–15.0] | 3.0 [1.0–4.0] | <0.001 |
| Median time to MV, days¶ | 3 [1–6] | 11 [9–18] | 2 [1–4] | <0.001 |
COVID-19, coronavirus disease 2019; Fio2, fraction of inspired oxygen; IQR, interquartile range; Pao2, partial pressure of oxygen; Paco2, partial pressure of carbon dioxide. ROX, Respiratory rate-oxygenation; SD, standard deviation; Data were expressed median [interquartile range] or as mean ± standard deviation.
Arterial blood gas analysis was conducted in 90 HFNC failure patients and 128 success patients.
¶
Median time to MV were available in 141 patients, because do-not-intubate or non-invasive ventilation intolerance was 32 in HFNC failure patients and 23 in success patients.