Clinical Trial Details
— Status: Recruiting
Administrative data
| NCT number |
NCT05549882 |
| Other study ID # |
2020ZDSYLL303-P02 |
| Secondary ID |
|
| Status |
Recruiting |
| Phase |
|
| First received |
|
| Last updated |
|
| Start date |
October 1, 2022 |
| Est. completion date |
August 2023 |
Study information
| Verified date |
August 2023 |
| Source |
Southeast University, China |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
|
| Study type |
Observational [Patient Registry]
|
Clinical Trial Summary
High-flow nasal cannula (HFNC) is increasingly used in patients with acute hypoxemic
respiratory failure (AHRF) and has been shown to improve outcome in specific patient
categories, including community acquired pneumonia and after extubation. Since HFNC failure
and delayed intubation is associated with adverse clinical outcome, predicting HFNC failure
is of clinical importance.
In patients with pneumonia and hypoxemic failure treated with HFNC, the ROX index (SpO2/FiO2
over respiratory rate), has been validated to predict the risk for endotracheal intubation.
Increased respiratory rate, an important component of ROX, is used as an estimate for high
respiratory drive, although it is well known that respiratory rate is insensitive to early
changes in respiratory drive. Indeed, it has been shown that ROX worked best only after 12
hours after HFNC initiation. Earlier and more sensitive predictors of HFNC failure would be
of clinical importance. Initially, elevated respiratory drive increases tidal volume (VT),
but not respiratory rate. In addition, high VT has been linked to patient self-inflicted lung
injury (P-SILI) and such may increase intubation rate in patients with AHRF. Taken together,
from a physiological perspective, elevated TV may be a better predictor for HFNC failure
compared to respiratory rate. Hence, we report an approach to measure VT generated by
patients supported with HFNC and establish a novel index named VOX (Volume-OXygenation) based
on VT to predict HFNC failure in patients with AHRF.
Description:
Study design This is a multi-center prospective observational study performed over a 12-month
period (from August 2022 to August 2023). The research premise was granted approval by the
local Ethics Committee (2020ZDSYLL303-P02).
VOX index The VOX index was defined as the ratio of SpO2/FiO2 over VT. Investigators briefly
interrupted HFNC (3 minutes) to measure VT using a mechanical ventilator (SV800, Mindray) in
noninvasive ventilation (NIV) mode, as an "NIV test". Inspiratory support was set at 5 cmH2O
and 5 cmH2O positive end-expiratory pressure level for all patients, and initial oxygen
concentration was set as in HFNC. NIV was delivered through a face mask (ZS-MZ-A, Zhongshan
Medical) and a double-pipe system, while minimizing leaks. In consideration of variations in
VT, we recorded mean VT and respiratory rate for 1 minute under stable conditions.
Study protocol HFNC therapy was started within 15 minutes after recruitment and initiated
with a 30-40 LPM minimum flow. Investigators adjusted FiO2 as suitable, targeting SpO2 of 92%
or more, and the rate of flow set on the basis of the physician's decision. HFNC
discontinuation and invasive mechanical ventilation (IMV) initiation were based on the
intubation criteria defined in investigators clinical protocol, finial decisions were made by
the physicians in charge, who were blinded to the VT during NIV test. HFNC failure was
defined as a need for IMV, on account of NIV is not employed as the second line of
ventila,ory support in the event of HFNC failure, in the participating units. Patient
demographics, comorbidities, and chest radiographs prior to HFNC initiation were documented
upon inclusion into the research analysis. The acute physiologic assessment and chronic
health evaluation II (APACHE II) score along with the sequential organ failure assessment
score (SOFA) were documented based on the highest scores in the 24h previous HFNC initiation.
The time of HFNC onset was defined as 0h. Vital signs; HFNC settings including FiO2, flow
rate, and temperature; clinical respiratory variables including RR, VT, and SpO2;
diaphragmatic ultrasonography including diaphragmatic displacement, diaphragm thickness
(tdi), and Δtdi% (was calculated as [tdi end-inspiration-tdi end-expiration/tdi
end-expiration] ×100) were recorded at 0, 2, 6, 12, 18, and 24h following initiation of HFNC
treatment. Variables of pulmonary gas exchange variables with the arterial line were
documented at 0, 6, 12, and 24h after initiation of HFNC treatment.
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