In total, 12 COVID-19 patients underwent
surgical tracheotomy over a 4-week period (March-April 2020), of which
two died (patients B and C). Patient B had FiO2 values
ranging between 81-90% in the 24 hours before tracheotomy, whilst
patient C had their tracheotomy performed 4 days after having a positive
swab result. Of the remaining patients that survived, patients D and E
took the longest to be decannulated, both of whom had pre-operative
FiO2 values ≥50%, as well as high PEEP values (Table
1).
The data suggest that a patient’s pre-operative status in the 24 hours
preceding the procedure may highlight those patients likely to benefit
from tracheotomy. Figure 1 illustrates each patient’s pre-operative
FiO2 concentration and PEEP requirements in the format
of a bubble plot, which suggests that an FiO2 of ≥50%
with a PEEP of ≥8cm of H2O in the 24 hours preceding
tracheotomy may be associated with a worse outcome, as the patients that
did not fulfil these criteria in the 24 hours preceding tracheotomy
either died or had a prolonged wean of ventilation despite the
procedure.
Cumulative data suggested that patients requiring an
FiO2 of ≤50% and PEEP of ≤8cm of H2O in
the first 48 hours following tracheotomy tended to have a more favorable
outcome compared to those exceeding these values. To examine this in
greater depth, the proportion of time for each patient at which the PEEP
was ≥8cm H20 and the proportion of time
FiO2 was ≥50% across all days were calculated
regardless of length of follow-up. From this, the average proportion of
time that PEEP was ≥8cm H20 and average proportion of
time that FiO2≥50% were calculated, with the patients
subsequently ranked accordingly. These steps were then repeated but with
only looking at the data for up to day 2 post-tracheotomy to look for
early prognostic indicators (see Supplementary Figures 1 and 2). The
ranks for both parameters were then plotted on a scatter plot (Figure
2), which illustrates that rank at day 2 post-tracheotomy strongly
correlates with rank from all days, and therefore with the patient’s
final outcome (ρ=0. 955, P<0.05).
Discussion
This is the first report of patient outcomes following tracheotomy in
COVID-19 patients, and on the basis of our institutional experience we
propose criteria that offer a pragmatic solution to facilitate patient
care whilst minimizing risks to healthcare workers.
Given the risk that tracheotomy in COVID-19 patients poses to healthcare
workers through aerosolization of SARS-CoV-2 virions, it is paramount
that these risks are carefully balanced against potential benefits to
patient care. Concerns around infection in COVID-19 patients stem from
previous experience from SARS-CoV, which posed a particular risk to
healthcare workers as peak viral load tended to occur 7-10 days
post-infection 10. In contrast, COVID-19 patients
appear to have the highest viral load at the onset of infection and this
subsequently declines over time, which may account for the speed at
which this novel coronavirus is spreading within the community11. Furthermore, although it has been shown that
SARS-CoV-2 RNA can be detected in patients up to 20 days or longer
post-infection, it is unclear whether this represents patients shedding
live virus, or if this reflects shedded virions inactivated by host
antibodies 11. In the context of planning a
tracheotomy, this has two important implications; first, a positive test
does not reflect the degree of infectivity of a patient, and second, on
the basis of current data we can draw a cautious degree of reassurance
that patients are likely to be less infectious the further away they are
from their initial presentation. Thus, we believe that undertaking a
tracheotomy at least 14 days following a positive swab result, in
conjunction with wearing full Personal Protective Equipment (PPE) and
taking all the necessary steps to minimize aerosolization
peri-tracheotomy insertion (see Supplementary Material) presents a
pragmatic solution to minimizing risk to staff. To date, none of the OR
staff who have been involved with undertaking tracheotomies in COVID-19
patients has tested positive for the disease in our institution.
In light of the relative uncertainties that exist in the treatment of
patients with COVID-19, patient selection for tracheotomy will
ultimately be refined through experience. The selection criteria
proposed in this study (FiO2≤50% and PEEP≤8cm of
H2O in the 24 hours prior to the tracheotomy) were
derived on the basis of our early experience with the first five
COVID-19 tracheotomies; of which, one survived (patient A), two died
(patients B and C) and the remaining two had a prolonged wean off the
ventilator (patient D, who was taken off ventilation at day 17
post-procedure, and patient E, who continues to be on ventilation at the
time of writing). Of the 4 patients who had less favorable outcomes,
three had either an FiO2≥50% or a PEEP requirement
exceeding 8cm H2O. The ‘anomaly’ was patient C who
despite being within an acceptable range for both FiO2and PEEP unfortunately died. In retrospect, this patient probably had
their tracheostomy too early at day 4 post-intubation; it is thus vital
that ICU teams liaise closely with surgical teams when identifying
potential candidates for tracheotomy, and put forward those patients who
have demonstrated improvement in their clinical course.
From this study, two important findings emerge in terms of the
prognostic value of ventilation-related parameters prior to tracheotomy.
These are an FiO2 requirement ≤50% and PEEP≤8cm
H2O in the 24 hours prior to tracheotomy with all
patients exceeding these cut off values either experiencing a prolonged
wean and dying or failing to improve and continuing to require ICU
support. Satisfying both the FiO2 and PEEP criteria is
equally important when considering tracheotomy in COVID-19 patients
failing trial(s) of extubation. The case of patient D illustrates why
consideration of FiO2 requirements alone is not adequate
when it comes to COVID-19 patients. Even if pre-operative
FiO2 requirements remain below the 50% cut off,
COVID-19 patients are unlikely to do well following tracheotomy if their
PEEP requirements exceed 8cm H2O. The reason is that the
high PEEP dependence makes them less able to tolerate the combination of
a reduction in FiO2 to 21% during tracheal exposure and
the subsequent cessation of ventilation prior to tube exchange, both key
recommendation for tracheotomy in COVID-19 patients.12
Furthermore, we have demonstrated that there is a correlation (ρ=0. 955,p <0.05) between the proportion of time patients’ PEEP
values are ≤8cm H2O and their FiO2values are ≤50% in the first 48 hours following tracheotomy with the
respective values (ventilation requirements) across all days of their
stay in critical care. This is of clinical importance because it could
potentially permit prognostication through early risk-stratification;
with those patients whose ventilator requirements consistently remain
below the described cut off values (i.e. FiO2≤50% and
PEEP≤8cm of H2O) for the first 2 post-operative days to
represent a subgroup that can potentially be safely stepped down to
another clinical area outside the ICU environment at that stage. This
has the potential of freeing up intensive care beds as early as day 2
post-tracheotomy for other patients that need it more. Furthermore, with
the emergence of field hospitals to help cope with the increased patient
demand from the COVID-19 pandemic, this could assist in identifying
those patients who following tracheotomy are suitable for transfer to
such facilities, further enhancing ICU capacity, a precious and limited
resource in the fight against COVID-19.
Prior to concluding, it is important to consider the strengths and
limitations of this study. The key limitation relates to the small
number of patients (n=12). Another relates to the novelty of the disease
studied meaning that it is likely that further refinements to the
proposed criteria will be needed in the future as our understanding of
the pathophysiology of COVID-19 evolves. Finally, only two prognostic
parameters were studied. Despite these limitations, this study also
features a number of key strengths. It is the first to look into the
development of formal selection criteria for tracheotomy in ventilated
patients with COVID-19 and the first to determine early prognostic
factors for these patients. Moreover, this has been done in a
quantitative manner. By providing actual cut off values for pre- and
post-tracheotomy ventilatory requirements, it facilitates patient
selection, permits risk stratification and in doing so can directly
assist clinical decision-making and inform policy.
In conclusion, this study presents for the first time measurable patient
selection criteria for tracheotomy in COVID-19 patients, illustrating
that an FiO2≤50 % and PEEP≤8cm H20 in
the 24 hours prior to tracheotomy are useful markers in helping to
identify those patients that are most likely to benefit from a
tracheotomy. It has also shown that patients that are able to remain
below these threshold values in the first 48 hours following tracheotomy
are likely to exhibit a favourable outcome and can thus be stepped down
from an intensive care setting at that (early) stage, freeing up vital
capacity for other critically ill COVID-19 patients in need of urgent
ICU care.
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