- •COVID-19 respiratory failure may be resistant to conventional high-flow oxygen delivery systems.
- •Mechanical ventilation of COVID-19 patients is associated with high mortality.
- •Oxygen hoods improve saturation in patients failing on conventional oxygen delivery systems.
- •Oxygen hoods prevented imminent mechanical ventilation in patients failing on conventional oxygen delivery systems.
- •Lower mechanical ventilation and mortality rates are observed with the use of oxygen hoods.
Main outcome(s) and measure(s)
What this research paper adds?
What is already known?
- •A previous randomized controlled study found that oxygen hoods resulted in improved oxygenation, decreased mechanical ventilation and mortality rates in patients with Adult Respiratory Distress Syndrome (ARDS).
- •COVID-19 associated respiratory failure demonstrates similarities to ARDS related respiratory failure but is not identical in its pathophysiology.
- •Preliminary experience in Italy suggested oxygen hoods improved oxygenation in COVID-19 patients failing on other forms of conventional oxygen delivery systems.
- •There were no clinical trials investigating whether oxygen hoods would benefit and improve oxygenation, decrease the need for mechanical ventilation, or mortality rates in COVID-19 patients.
What this study adds?
- •Our study was conducted during the surge in COVID-19 admissions to our hospital institution. It supports the role of oxygen hoods to improve patient oxygenation and prevent immediate and imminent intubation in patients failing on conventional high-flow oxygen delivery systems during the COVID-19 pandemic.
- •Our study observed reductions in mechanical ventilation and mortality rates using the oxygen hoods in patients with COVID-19 impending respiratory failure. However these observations in mechanical ventilation and mortality did not reach the threshold for statistical significance.
- 1)To compare the differences in oxygenation before and after the use of oxygen hoods on COVID-19 patients failing on conventional high flow oxygen systems.
- 2)To compare mechanical ventilation rates, mortality rates, and length of hospitalization in COVID-19 patients failing on conventional oxygen delivery systems who are subsequently placed on oxygen hoods as compared to COVID-19 patients failing on conventional high flow oxygen delivery systems prior to the availability of oxygen hoods.
- 3)To determine which risk factors, and whether the use of the intervention oxygen hoods can predict the outcomes mechanical ventilation and mortality rates.
2.1 Study design and setting
- B L
- A C
- Z B
- et al.
2.2 Patient and public involvement
2.3 Study protocol
2.3.2 Outcome measures
|n||Minimum SaO2 (%)||Maximum SaO2 (%)||Mean SaO2(%)||% Change pre and post SaO2||Paired t||Sig (2-tailed)|
aHigh Flow Delivery System SaO2
|58||72||94||85.7||8.8||17.009||P < 0.001|
|Post Oxygen Hood SaO2||58||83||100||94.5|
2.3.3 Outcome variables of interest
- 1)Oxygen Difference pre/post-hood (SaO2 difference, %)
- 2)Intubation/MV status (Y/N)
- 3)Survival/Mortality (Y/N)
- 4)Hospital Length of Stay (days)
2.3.4 Inclusion criteria
- •Hospital census was reviewed for ALL patients seen in the ED and admitted with COVID -19 diagnosis experiencing hypoxia requiring supplemental high-flow oxygen delivery or mechanical ventilation, along with those failing on these high-flow oxygen systems.
- •Consent (native language services provided).
- •No limitations/restrictions based on age, gender, race/ethnicity, comorbidities, pregnancy status, DNR/DNI status.
2.3.5 Exclusion criteria
- •SaO2 > 90% and controlled on room air (RA) or low-flow O2-delivery system (nasal cannula, simple mask, or venturi-mask).
- •Confinement anxiety post-oxygen hood placement with request for removal.
2.3.7 Comparison/control group
2.3.8 Sample size estimate
2.3.9 Sensitivity analysis
3.1 Primary outcomes
3.2 Characteristics of participants included in the study
|Characteristic or condition|
N = 136
a(n = 58)
|Control cohort (n = 78)||p-value|
aMean Difference 95%CI
|Age -mean (yrs.)|
|68 (25–93)||70.4 (26–98||−2.4 (−3.0 to 8.0)|
|BMI kg/height (m2)|
|28.2 (17.1–47.4)||29.7 (14.8–75.6)||−1.5 (−7.6 to 2.8)|
|Male gender no/total, (%)||42/58, (72)||48/78, (61.5)||0.19|
|Smoking history||19/55 (35)||20/66 (26)||0.62|
|CLD||7/58 (12)||13/78 (17)||0.45|
|CVD||14/58 (24)||28/78 (36)||0.14|
|CKD||4/58 (6.9)||17/78 (22)||0.02|
|Immunosuppression||5/58 (8.6)||11/77 (14)||0.31|
|DM||17/58 (29)||40/78 (51)||0.01|
|DNR||25/58 (43)||22/78 (28)||0.71|
|Plasma||21/58 (36)||2/78 (2.6)||<0.001|
|Mean 95%CI n||Mean 95%CI n|
|D-Dimer (ng/mL)||4049 (187–52915) n = 52/58||5611 (187–55559) n = 49/78||−1563 (−6151 to 3026)|
|Lymphocyte count (absolute cell count)||999 (92–7876) n = 57/58||1026 (112–6903) n = 76/78||- 27 (−389 to 336)|
|WBC (absolute cell count)||10079 (1700–35800) n = 58/58||9812 (3800–24900) n = 77/78||268 (−1456 to 1991)|
|Hgb (gm/dL)||13.4 (8.5–17.9) n = 58/58||12.8 (6.7–18) n = 77/78||0.63 (−0.13 to 1.4)|
|Creatinine (mg/dL)||1.50 (0.5–15.9) n = 58/58||1.84 (0.3–10.2) n = 76/78||−0.34 (- 1.1 to 0.39)|
|ALT (U/L)||62 (17–160) n = 58/58||69 (10–430) n = 75/78||−7.1 (−29 to 15)|
|CRP (mg/L)||228 (35–481) n = 58/58||204 (5–798) n = 77/78||24 (−23 to 72)|
|Ferritin (ng/mL)||1745 (218–9295) n = 56/58||1670 (47–17933) n = 63/78||75 (−719 to 868)|
|LDH (U/L)||1418 (366–3521) n = 55/58||1472 (368–9614) n = 71/78||−54 (−426 to 318)|
|Procalcitonin (ng/mL)||0.58 (0.02–3.63) n = 47/58||1.54 (0.04–29.9) n = 51/78||−1.5 (- 3.2 to 0.12)|
|INR||1.9 (0.9–15) n = 43/58||1.5 (1–15) n = 64/78||0.40 (−0.47 to 1.3)|
3.3 Mechanical ventilation and mortality rates in the total sample
|Mortality in the Intubated patients||Mortality in the Non - Intubated Patients||OR 95%CI||p-value Pearson Chi squared|
|Total Sample||60/136 (44.1%)||76/136 (55.9%)||45/60 (75%)||45/76 (59.2%)||2.07 (0.98 to 4.34)||p = 0.053|
3.4 Mechanical ventilation and mortality rates in the intervention and control cohorts
Sample (N = 136)
|Intervention cohort (n1 = 58)||Control cohort (n2 = 78)||Difference (%)||OR 95%CI||Mean|
T - test
|Mechanical Ventilation||23/58 (39.7%)||37/78 (47.4%)||7.7%||0.73 (0.37 to 1.5)||0.37|
|Mortality||36/58 (62.1%)||54/78 (69.2%)||7.1%||0.73 (0.36 to 1.5)||0.38|
|Length of Stay||12.62 days||10.13 days||2.49 (−0.37 to 5.35)||0.90|
3.5 Subgroup analyses
- A.Subgroup Analysis Excluding Any Patients Who Received Convalescent Plasma Antibodies From Both Cohorts (Excluded 21-Intervention and 2-Control Patients). Table 4a
- B.Mechanical Ventilation Rates after Reassignment of DNI/DNR Patients who Expired AND were never Mechanically ventilated as Mechanically Ventilated; with the Exclusion of Patients Receiving Convalescent Plasma Antibodies in both cohorts. Table 4b
3.6 Logistic regression analysis (using forward and backward stepwise Likelihood Ratio)
N = 113
|Intervention cohort (n1 = 36)||Control cohort (n2 = 75)||Difference (%)||OR 95%CI||Mean|
T - test
|Mechanical Ventilation||23/37 (40.5%)||36/76 (47.4%)||6.9%||0.76 (0.34 to1.7)||0.49|
|Mortality||23/37 (62.2%)||52/76 (68.4%)||6.2%||0.76 (0.33 to 1.7)||0.51|
|Length of Stay||10.57 days||10.36 days||0.21 (−2.6 to 3.0)||0.88|
N = 113
|Intervention cohort (n1 = 37)||Control cohort (n2 = 76)||Difference||OR 95%CI||p-value|
|Mechanical Ventilation||24/37 (63.9%)||49/76 (69.7%)||5.8%||0.77 (0.33 to 1.8)||0.54|
|Coefficient (B)||Standard Error (SE)||Wald|
|Sig.||Exp (B)||Exp (B) 95%CI|
|Age||0.035||0.014||6.097||0.014||1.036||(1.007 to 1.07)|
|Coefficient (B)||Standard Error (SE)||Wald|
|Sig.||Exp (B)||Exp (B) 95%CI|
|Age||0.046||0.015||9.213||0.002||1.047||1.02 to 1.08|
Conflict of interest disclosures
Role of the funder/sponsor
CRediT authorship contribution statement
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