Table 2.
Effort to Breathe, Respiratory Mechanics, Gas Exchange, and Hemodynamics
| HFNO | Helmet CPAP | Helmet NIV |
P Value* HFNO vs. CPAP |
P Value† HFNO vs. NIV |
P Value‡ CPAP vs. NIV |
|
|---|---|---|---|---|---|---|
| Effort to breathe and respiratory mechanics | ||||||
| ΔPES, cm H2O | 10 (8 to 13) | 13 (10 to 19) | 5 (3 to 9) | 0.17 | 0.01 | 0.001 |
| Quasi-static ΔPL, cm H2O | 9 (8 to 10) | 12 (7 to 18) | 13 (8 to 17) | 0.26 | 0.13 | >0.99 |
| PEEP, cm H2O | 2.5§ | 13.5 (12.1 to 14.8) | 13.6 (12.7 to 15.1) | 0.001 | 0.001 | >0.99 |
| Respiratory rate, breaths/min | 26 (21 to 32) | 30 (25 to 34) | 28 (23 to 33) | 0.29 | >0.99 | 0.15 |
| PES pressure‒time product per minute, cm H2O ⋅ sec ⋅ min−1 | 215 (143 to 305) | 299 (234 to 437) | 181 (88 to 236) | 0.34 | 0.56 | 0.002 |
| Mean airway expiratory pressure, cm H2O | 2.5§ | 14 (12 to 15) | 16 (16 to 19) | 0.001 | 0.001 | 0.001 |
| Mean transpulmonary expiratory pressure, cm H2O | −5 (−13 to −3) | 0 (−3 to 3) | −1 (−4 to 5) | 0.001 | 0.001 | >0.99 |
| Esophageal pressure, end-expiratory, cm H2O | 7 (6 to 16) | 14 (11 to 17) | 14 (10 to 18) | 0.02 | 0.03 | >0.99 |
| Transpulmonary pressure, mean pressure, cm H2O | −5 (−13 to −3) | 0 ( to 3 to 3) | 1 (−1 to 7) | 0.001 | 0.001 | 0.13 |
| Inspiratory time, s | 1.14 (0.77 to 1.49) | 1.01 (0.79 to 1.26) | 1.06 (0.84 to 1.29) | >0.99 | >0.99 | >0.99 |
| Expiratory time, s | 1.26 (0.96 to 1.52) | 1.08 (0.70 to 1.24) | 1.20 (0.96 to 1.37) | 0.88 | >0.99 | 0.73 |
| Dyspnea, VAS | 3 (0 to 6) | 2 (0 to 5) | 2 (0 to 4) | 0.55 | 0.21 | >0.99 |
| Self-assessed discomfort, VAS | 2 (0 to 4) | 4 (2 to 6) | 4 (1 to 7) | 0.008 | 0.11 | >0.99 |
| Gas exchange | ||||||
| FiO2 | 0.6 (0.5 to 0.6) | 0.6 (0.5 to 0.6) | 0.6 (0.5 to 0.6) | 0.23 | 0.25 | >0.99 |
| PaO2 | 67 (60 to 75) | 105 (84 to 140) | 87 (81 to 110) | 0.001 | 0.001 | 0.14 |
| PaO2/FiO2 | 120 (107 to 149) | 175 (158 to 281) | 166 (136 to 215) | 0.001 | 0.002 | 0.13 |
| SpO2 | 93 (86 to 95) | 97 (94 to 98) | 95 (93 to 97) | 0.40 | 0.12 | 0.025 |
| SpO2/FiO2 | 158 (142 to 182) | 165 (163 to 194) | 162 (158 to 188) | 0.03 | 0.07 | 0.02 |
| PaCO2 | 32 (26 to 35) | 34 (27 to 38) | 35 (28 to 37) | 0.09 | 0.10 | >0.99 |
| Hemodynamics | ||||||
| Heart rate, beats/min | 81 (70 to 91) | 79 (70 to 92) | 80 (70 to 92) | >0.99 | >0.99 | >0.99 |
| Arterial pressure, mm Hg | ||||||
| Systolic | 137 (130 to 160) | 140 (120 to 163) | 141 (124 to 154) | 0.65 | 0.94 | >0.99 |
| Mean | 87 (80 to 96) | 90 (81 to 102) | 87 (80 to 98) | 0.35 | >0.99 | >0.99 |
| Diastolic | 62 (60 to 70) | 68 (60 to 70) | 67 (60 to 77) | >0.99 | 0.33 | 0.21 |
Definition of abbreviations: CPAP = continuous positive airway pressure; HFNO = high-flow nasal oxygen; NIV = noninvasive ventilation; PEEP = positive end-expiratory pressure; PES = esophageal pressure; PL = transpulmonary pressure; SpO2 = oxygen saturation as measured by pulse oximetry; VAS = visual analog scale; ΔPES = inspiratory effort; ΔPL = transpulmonary pressure.
Data are reported as median (interquartile range). All paired comparisons were adjusted with Bonferroni’s or Dunn’s correction, as appropriate. P values ⩽ 0.05 are considered statistically significant.
Comparison between HFNO and helmet CPAP.
Comparison between HFNO and helmet NIV.
Comparison between helmet CPAP and helmet NIV.
The airway pressure during HFNO was not measured but assumed to be constant at 2.5 cm H2O.