pEEP at each respiratory support level including effect of mouth position
| HFNC | nCPAP | |||||||
| Flow (L/min) | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 6 cm H2O |
| pEEP (cm H2O) | 2.3±1.3 | 3.4±1.6 | 4.1±1.6 | 4.2±1.4 | 4.8±1.7 | 5.4±2.0 | 6.1±2.1 | 6.4±1.5 |
| Mouth closed | 2.7 | 4.0 | 4.8 | 5.1 | 5.7 | 6.4 | 7.3 | n/a |
| Mouth open | 2.1 | 2.9 | 3.3 | 3.5 | 4.2 | 4.5 | 5.1 | n/a |
| Difference | 0.6 | 1.1 | 1.5 | 1.6 | 1.4 | 1.9 | 2.3 | n/a |
| P value* | 0.002 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | n/a |
| pEECO2 (%) | 2.3±1.6 | 1.9±1.5 | 1.7±1.5 | 1.7±1.7 | 1.4±1.5 | 1.0±1.3 | 0.9±1.1 | 2.4±1.8 |
| Vt/kg (mL/kg) | 4.3±1.9 | 3.8±2.0 | 4.0±1.9 | 4.4±2.3 | 3.9±1.6 | 3.9±1.6 | 4.2±1.8 | 4.7±2.1 |
| RR (bpm)† | 70±17 | 64±15 | 66±18 | 64±17 | 63±18 | 61±16 | 62±15 | 66±17 |
| MV (mL/kg/min) | 309±162 | 235±122 | 258±128 | 269±157 | 247±133 | 239±99 | 268±148 | 315±176 |
| TCCO2 (kPa) | 6.2±1.1 | 6.2±0.8 | 6.1±0.9 | 6.1±1.1 | 6.1±1.0 | 6.3±1.0 | 6.3±0.9 | 6.5±1.1 |
| SpO2 (%)‡ | 92.0±4.4 | 93.5±3.8 | 94.2±4.0 | 94.8±3.5 | 95.3±3.0 | 95.9±3.2 | 96.4±3.3 | 95.1±3.8 |
| HR (bpm) | 156±13 | 158±12 | 159±12 | 160±12 | 160±10 | 162±12 | 164±12 | 165±13 |
Effects of HFNC therapy on pEECO2, tidal volume, ventilation, gas exchange and haemodynamics.
Expressed as means±SD.
*Wilcoxon signed rank test (mouth position).
†Analysis of variance, p=0.047, when HFNC 8 L/min reduced to HFNC 2 L/min across all flows.
‡Friedman, p≤0.0001, when HFNC 8 L/min reduced to HFNC 2 L/min across all flows.
HR, heart rate; HFNC, high-flow nasal cannula; n/a, not available; nCPAP, nasal continuous positive airway pressure; MV, minute vol; pEEP, nasopharyngeal end-expiratory pressure; pEECO2, nasopharyngeal end-expiratory CO2; RR, respiratory rate; SpO2, oxygen saturation; TCCO2, transcutaneous CO2; Vt, tidal volume.