Table 1.
Characteristics at Inclusion and Study Outcomes, according to Study Group*
| PaCO2 < 35mm Hg (n = 59) |
PaCO2 ⩾ 35 mm Hg (n = 50) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Helmet Noninvasive Ventilation (n = 28) | High-Flow Nasal Oxygen (n = 31) | Absolute or Mean Difference (95% CI) | OR (95% CI) | P Value | Helmet Noninvasive Ventilation (n = 26) | High-Flow Nasal Oxygen (n = 24) | Absolute or Mean Difference (95% CI) | OR (95% CI) | P Value | |
| Characteristics at study inclusion | ||||||||||
| Age, yr | 66 (53 to 73) | 64 (55 to 71) | −1 (−8 to 4) | — | 0.93 | 66 (60 to 72) | 61 (53 to 68) | 8 (1 to 14) | — | 0.056 |
| Sex, F, n (%) | 4 (14) | 5 (16) | −2 (−20 to 18) | 0.87 (0.21 to 3.6) | >0.99 | 18 (69) | 20 (83) | −14 (−36 to 10) | 2.22 (0.57 to 8.65) | 0.33 |
| Sex, M, n (%) | 24 (86) | 26 (84) | 2 (−18 to 20) | 1.15 (0.28 to 4.81) | >0.99 | 8 (31) | 4 (17) | 14 (−10 to 36) | 0.45 (0.12 to 1.75) | 0.33 |
| Body mass index† | 26 (26 to 29) | 27 (23 to 32) | 0 (−1 to 1) | — | 0.97 | 28 (26 to 31) | 30 (23 to 33) | −2 (−5 to 1) | — | 0.18 |
| Respiratory rate at enrollment, breaths/min | 28 (24 to 35) | 26 (23 to 32) | 1 (−3 to 5) | — | 0.61 | 30 (24 to 31) | 28 (23 to 31) | 1 (−2 to 3) | — | 0.69 |
| Device-related discomfort at enrollment‡ | 1 (0 to 3) | 0 (0 to 1) | 1 (0 to 2) | — | 0.13 | 0 (0 to 5) | 0 (0 to 2) | 0 (−1 to 2) | — | 0.96 |
| VAS dyspnea at enrollment‡ | 3 (2 to 6) | 4 (0 to 6) | 1 (−1 to 2) | — | 0.41 | 4 (1 to 7) | 3 (1 to 7) | 2 (−1 to 2) | — | 0.98 |
| VAS dyspnea change after 1 h of treatment‡ | 1 (0 to 3) | 0 (−1 to 1) | 2 (0 to 3) | — | 0.006 | 1 (0 to 3) | 0 (−1 to 3) | 1 (−1 to 2) | — | 0.10 |
| Arterial blood gases at enrollment | ||||||||||
| PaO2/FiO2 ratio, mm Hg | 103 (84 to 126) | 93 (80 to 122) | 10 (−4 to 17) | — | 0.30 | 106 (82 to 126) | 109 (84 to 130) | −4 (−21 to 13) | — | 0.68 |
| PaCO2, mm Hg | 31 (28 to 33) | 32 (30 to 34) | −1 (−3 to 0) | — | 0.046 | 37 (36 to 39) | 37 (36 to 40) | 0 (−1 to 2) | — | 0.85 |
| SAPS II | 32 (25 to 35) | 29 (24 to 37) | 0 (−4 to 3) | — | 0.98 | 32 (28 to 37) | 24 (28 to 32) | 4 (0 to 9) | — | 0.024 |
| Outcomes | ||||||||||
| Respiratory support–free days | 21 (11 to 25) | 14 (0 to 21) | 5 (0 to 11) | — | 0.07 | 16 (0 to 24) | 20 (1 to 23) | −2 (−8 to 4) | — | 0.80 |
| Intubation within 28 d from enrollment | 5 (18) | 19 (61) | −43 (−61 to −19) | 0.14 (0.04 to 0.46) | 0.001 | 11 (42) | 9 (38) | 9 (−17 to 33) | 1.22 (0.39 to 3.80) | 0.78 |
| 28-d invasive ventilation-free days | 28 (28 to 28) | 19 (3 to 28) | 8 (2 to 14) | — | 0.003 | 28 (4 to 28) | 28 (9 to 28) | −2 (−8 to 5) | — | 0.81 |
| 60-d invasive ventilation-free days | 60 (60 to 60) | 50 (5 to 60) | 17 (5 to 30) | — | 0.002 | 60 (8 to 60) | 60 (33 to 60) | −8 (−20 to 5) | — | 0.36 |
| 28-d mortality | 3 (11) | 8 (26) | −15 (−34 to 5) | 0.34 (0.08 to 1.46) | 0.19 | 5 (19) | 2 (8) | 11 (−10 to 30) | 2.62 (0.46 to 15) | 0.42 |
| 60-d mortality | 5 (18) | 10 (32) | −14 (−35 to 8) | 0.46 (0.13 to 1.55) | 0.24 | 8 (31) | 2 (8) | 22 (0 to 43) | 4.89 (0.92 to 25.97) | 0.78 |
| In-ICU mortality | 3 (11) | 12 (39) | −28 (−47 to −6) | 0.19 (0.05 to 0.77) | 0.018 | 8 (31) | 2 (8) | 22 (0 to 43) | 4.89 (0.92 to 25.97) | 0.78 |
| In-hospital mortality§ | 5 (18) | 12 (39) | −21 (−41 to 2) | 0.34 (0.10 to 1.15) | 0.092 | 8 (31) | 2 (8) | 22 (0 to 43) | 4.89 (0.92 to 25.97) | 0.78 |
| Duration of stay in the ICU, d | 8 (4 to 17) | 12 (6 to 23) | −9 (−18 to 0) | — | 0.12 | 9 (4 to 22) | 8 (5 to 17) | −3 (−13 to 8) | — | 0.88 |
| Duration of stay in the hospital, d | 22 (14 to 33) | 23 (13 to 47) | −8 (−20 to 3) | — | 0.37 | 20 (13 to 28) | 18 (13 to 32) | −4 (−15 to 6) | — | 0.91 |
| PaO2/(FiO2 × VAS Dyspnea) ⩾ 30 (n = 55) |
PaO2/(FiO2 × VAS Dyspnea) < 30 (n = 54) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Helmet Noninvasive Ventilation (n = 27) | High-Flow Nasal Oxygen (n = 28) | Absolute or Mean Difference (95% CI) | OR (95% CI) | P Value | Helmet Noninvasive Ventilation (n = 27) | High-Flow Nasal Oxygen (n = 27) | Absolute or Mean Difference (95% CI) | OR (95% CI) | P Value | |
| Characteristics at study inclusion | ||||||||||
| Age, yr | 65 (59 to 72) | 64 (57 to 69) | 3 (−3 to 9) | — | 0.36 | 67 (53 to 73) | 59 (53 to 70) | 2 (−4 to 8) | — | 0.44 |
| Sex, F, n (%) | 5 (18) | 6 (21) | −3 (−24 to 18) | 0.83 (0.22 to 3.14) | >0.99 | 7 (26) | 3 (11) | 15 (−6 to 35) | 2.8 (0.6 to 12.2) | 0.29 |
| Sex, M, n (%) | 22 (82) | 22 (79) | 3 (−18 to 24) | 1.2 (0.32 to 4.52) | >0.99 | 20 (74) | 24 (89) | −15 (−35 to 6) | 0.36 (0.08 to 1.56) | 0.29 |
| Body mass index† | 26 (26 to 29) | 28 (25 to 31) | −1.2 (−3.8 to 1.3) | — | 0.62 | 28 (26 to 30) | 28 (27 to 32) | −0.5 (−2.5 to 1.5) | — | 0.72 |
| Respiratory rate at enrollment, breaths/min | 29 (24 to 31) | 25 (22 to 29) | 2 (0 to 5) | — | 0.11 | 28 (24 to 32) | 30 (25 to 34) | −1 (−5 to 3) | — | 0.42 |
| Device-related discomfort at enrollment‡ | 0 (0 to 2) | 0 (0 to 0) | 0 (0 to 1) | — | 0.67 | 2 (0 to 5) | 1 (0 to 5) | 0 (−1 to 2) | — | 0.47 |
| VAS dyspnea at enrollment‡ | 2 (0 to 3) | 1 (0 to 2) | 0 (0 to 1) | — | 0.37 | 7 (5 to 7) | 6 (4 to 7) | 1 (0 to 1) | — | 0.15 |
| VAS dyspnea change after 1 h of treatment‡ | 0 (0 to 2) | 0 (−2 to 0) | 1 (0 to 2) | — | 0.005 | 2 (1 to 4) | 1 (0 to 3) | 1 (0 to 3) | — | 0.04 |
| Arterial blood gases at enrollment | ||||||||||
| PaO2/FiO2 ratio, mm Hg | 114 (83 to 133) | 115 (92 to 136) | 1 (−17 to 19) | — | 0.98 | 97 (82 to 115) | 90 (72 to 115) | 7 (−6 to 20) | — | 0.34 |
| PaCO2, mm Hg | 34 (31 to 37) | 34 (32 to 38) | −1 (−3 to 1) | — | 0.51 | 34 (31 to 38) | 34 (32 to 37) | 0 (−2 to 2) | — | 0.93 |
| SAPS II | 32 (27 to 35) | 29 (24 to 36) | 1 (−3 to 5) | — | 0.56 | 32 (29 to 35) | 29 (24 to 32) | 2 (−2 to 6) | — | 0.10 |
| Outcomes | ||||||||||
| Respiratory support-free days | 22 (13 to 25) | 21 (10 to 23) | 1 (5 to 6) | — | 0.49 | 13 (0 to 24) | 1 (0 to 19) | 3 (−2 to 9) | — | 0.29 |
| Intubation within 28 d from enrollment | 6 (22) | 9 (32) | −10 (−32 to 13) | 0.6 (0.18 to 2.01) | 0.55 | 10 (37) | 19 (70) | −33 (−54 to −7) | 0.25 (0.08 to 0.77) | 0.03 |
| 28-d invasive ventilation-free days | 28 (28 to 28) | 28 (18 to 28) | 1 (−5 to 6) | — | 0.46 | 28 (5 to 28) | 9 (2 to 28) | 6 (0 to 13) | — | 0.04 |
| 60-d invasive ventilation-free days | 60 (60 to 60) | 60 (50 to 60) | 2 (−10 to 13) | — | 0.45 | 60 (9 to 60) | 30 (9 to 60) | 10 (−3 to 23) | — | 0.09 |
| 28-d mortality | 3 (11) | 4 (14) | −3 (−22 to 16) | 0.75 (0.15 to 3-72) | >0.99 | 5 (18) | 6 (22) | −4 (−25 to 18) | 0.80 (0.21 to 3) | >0.99 |
| 60-d mortality | 5 (19) | 5 (18) | 1 (−20 to 21) | 1.05 (0.27 to 4.12) | >0.99 | 8 (30) | 7 (26) | 4 (−20 to 26) | 1.2 (0.36 to 4) | >0.99 |
| In-ICU mortality | 4 (15) | 5 (18) | −3 (−23 to 17) | 0.8 (0.19 to 3.36) | >0.99 | 7 (26) | 9 (33) | −7 (−30 to 16) | 0.7 (0.22 to 2.27) | 0.76 |
| In-hospital mortality§ | 4 (15) | 5 (18) | −3 (−23 to 17) | 0.8 (0.19 to 3.36) | >0.99 | 9 (33) | 9 (33) | 0 (−24 to 24) | 1 (0.32 to 3.1) | >0.99 |
| Duration of stay in the ICU, d | 5 (3 to 10) | 8 (5 to 11) | −1 (−8 to 6) | — | 0.21 | 13 (6 to 26) | 14 (5 to 57) | −11 (−23 to 0) | — | 0.42 |
| Duration of stay in the hospital, d | 17 (11 to 26) | 19 (13 to 30) | −1 (−9 to 6) | — | 0.50 | 24 (16 to 36) | 23 (14 to 70) | −12 (−26 to 1) | — | 0.50 |
Definition of abbreviations: CI = confidence interval; OR = odds ratio; SAPS II = Simplified Acute Physiology Score II; VAS = visual analog scale.
There were no missing data among the two groups. For calculations, PaO2 was expressed in mm Hg and FiO2 as fraction of the unity (0.21–1). For nonnormal quantitative variables, comparison between groups was performed with Mann-Whitney test. Comparisons between groups for qualitative variables were performed with the chi-square test or the Fisher’s exact test, as appropriate in agreement with test’s assumptions. Mean differences and odds ratios are unadjusted. For adjusted results, see the main text. Respiratory support: invasive or noninvasive mechanical ventilation, high-flow nasal cannula.
*
Values are displayed as median (interquartile range) if not otherwise specified.
†
The body mass index is the weight in kilograms divided by the square of the height in meters.
‡
Dyspnea and discomfort were assessed through visual analog scales adapted for patients in the ICU ranging from 0 to 10.
§
One patient was discharged from hospital but died upon readmission.