To the Editors:
The efficacy of proning for intubated and sedated patients with ARDS (Acute Respiratory
Distress Syndrome) is well established.
1
Proning of non‐intubated coronavirus disease 2019 (COVID‐19) patients has, therefore,
emerged as a potential early treatment of respiratory deterioration.
2
,
3
,
4
However, there are limited data on proning for non‐intubated patients with COVID‐19.
Thus, in non‐intubated COVID‐19 patients, we aimed to examine whether, compared to
the first proning treatment, subsequent proning treatments lead to a similar magnitude
of change for key respiratory observations.
This audit was performed during the second wave of COVID‐19 in Victoria, Australia
(1 July 1–30 September 2 020). Following ethics approval, we used clinical records
to retrospectively identify patients where proning was deemed clinically indicated.
This applied to 27 spontaneously breathing adults with COVID‐19 admitted to the Austin
Hospital. Proning was considered clinically indicated if the patient required supplemental
oxygen or was tachypnoeic (respiratory rate ≥ 25 breaths per minute). We applied linear
mixed effect modelling with the patient as a random effect for data analysis. We compared
the changes in oxyhaemoglobin saturation (SpO2), measured with pulse oximetry, and
in respiratory rate (breaths per minute) induced by the first proning treatment with
those induced by subsequent proning treatments. We performed a sensitivity analysis
with events where oxygen flow rate (litres per minute) remained constant during proning
to determine whether changes in supplemental oxygen during proning per se modified
the findings. Statistical significance was set at P < 0.05 and analyses were performed
using Stata 16.1.
5
The median age was 57 years (interquartile range (IQR): 51, 73), most were male (n
= 21, 78%) and chronic disease burden was low (Charlson comorbidity index score median
1, IQR: 0–1). Twenty (74%) patients received proning at least once, six (22%) never
received proning despite clinical indication (e.g. refused) and for one patient proning
was documented but no data were available. There were 94 documented proning events
in 20 patients, the majority occurred in the intensive care unit (n = 67, 71%) and
the remaining in the COVID‐19 ward (n = 27, 29%). For the patients who received proning
(n = 20), the median (IQR) number of treatments per patient and their duration (min)
were 3 (1, 6) and 105 (57, 170), respectively. Overall, the median SpO2 change per
proning treatment was −1% (−2, 2) and 0 (−3, 2) breaths per minute for respiratory
rate. There was no statistically significant effect of subsequent proning treatment
when compared to the first proning treatment for either change in SpO2 or respiratory
rate (SpO2: β = 0.10 (95% CI: −1.77 to 1.97); respiratory rate: β = −1.66 (95% CI:
−4.21 to 0.89)). Plotting differences in SpO2 and respiratory rate for the proning
event sequence in each patient did not reveal any clear response trajectories, that
is, ‘responders’ (Fig. 1).
Figure 1
Spontaneously breathing patients with COVID‐19 who received at least two proning treatments
(n = 14); changes in oxyhaemoglobin saturation measured with pulse oximetry and RR
per patient for each proning treatment are displayed. Reference line (zero) indicates
no change in oxyhaemoglobin saturation or RR. , Change in SpO2 (%) per treatment;
, change in RR (bpm) per treatment. bpm, breaths per minute; COVID‐19, coronavirus
disease 2019; RR, respiratory rate; SpO2, peripheral oxyhaemoglobin saturation.
The sensitivity analysis revealed that during the majority of proning treatments,
patients were receiving supplemental oxygen (n = 83, 88%), predominantly via nasal
prongs (n = 55 events, 59%). When oxygen flow rate remained constant (n = 61), SpO2
decreased in 52% of treatments (pre‐ and post‐proning difference < 0%, range: −9%
to −1%) and increased in 39% of treatments (pre‐ and post‐proning difference > 0%,
range: 1% to 13%). In all these patients, there was no effect of subsequent proning
treatment compared to the first for both SpO2 and respiratory rate.
In spontaneously breathing patients with COVID‐19, the novel and clinically important
findings of this research were that there was no evidence of a consistent response
to proning treatment and that the magnitude of any response to proning was not indicative
of any subsequent response to another proning treatment. Studies of proning in non‐ventilated
patients have reported improvement in oxygenation following proning and a lower incidence
of intubation.
3
,
4
,
6
,
7
However, none of these were controlled, let alone randomized. Moreover, all these
studies had small sample sizes (n = 10–56) with limited or no data on subsequent proning
outcomes. In contrast, a recent observational cohort study (n = 199) reported no difference
in clinical outcomes for patients receiving proning in addition to high‐flow nasal
oxygen therapy. In fact, proning delayed but did not avoid intubation.
8
We observed a heterogeneous response to proning and were unable to identify responders
and non‐responders.
In summary, in spontaneously breathing patients with COVID‐19, on an analysis of close
to 100 treatments, we found no evidence of reproducible response to proning and no
relationship between the effect of proning on first treatment with subsequent treatments.
Our findings imply uncertainty about the benefit of this intervention.
Author contributions
Conceptualization: Z.A., T.R., D.J.B. Formal analysis: J.R.A.J., M.G., D.J.B. Investigation:
Z.A., N.B., A.D., T.R. Methodology: J.R.A.J., R.B., M.G., T.R., D.J.B. Supervision:
R.B., D.J.B. Validation: N.B., A.D. Writing—original draft: J.R.A.J. Writing—review
and editing: J.R.A.J., R.B., M.G., T.R., D.J.B.