Discussion
This study aimed to examine the impact of the PP on critically ill
COVID-19 patients receiving invasive mechanical ventilation. We employed
a matching technique to establish comparable groups. The findings
revealed that PP has the potential to enhance the oxygenation levels and
All-cause survival rate. Furthermore, a positive correlation was
observed between the frequency of PP and the extent of oxygenation
improvement. The potential mechanism underlying the effect of the PP may
be associated with variations in lymphocyte count and the duration of
PP.
According to our data, the utilization of PP appeared to enhance
oxygenation and improve short-term survival rate in COVID-19 patients
who are invasive mechanical ventilated. Within 10 days after ICU
admission,, the survival rate of individuals in the PP group was notably
higher compared to those in the non-PP group, 94.9% of patients
received PP treatment. However, no significant disparity in survival
rate was observed between the two groups at the 20-day and 30-day.
29.5% and 6.4% of patients in the PP group have undergone PP treatment
for 10-20 days and 20-30 days, respectively. Notably, patients who
underwent PP three times exhibited a 100.0% survival rate during their
hospitalization period.
The survival rate during ICU stay was observed to be lower in patients
with critical COVID-19 infection, ranging from 33.3% to 47.6%
[11-13]. In a retrospective analysis conducted by Douglas, I.S et al
[14], a total of 61 critically ill patients receiving invasive
mechanical ventilation for COVID-19 were examined, revealing a hospital
survival rate of 68.9% in the PP group. However, the study lacked a
control group to ascertain whether the PP intervention influenced the
survival rate. Similarly, Engerstrom, L et al [15] investigated 1714
patients on mechanical ventilation in the ICU with neocoronary, and
determined that the PP did not have a significant impact on the 30-day
survival rate. Hence, it can be inferred that the implementation of PP
yields enhanced short-term survival rates, and the adoption of multiple
PPs contributes to improved survival rates during hospitalization;
however, their impact on long-term survival appears to be comparatively
limited.
The data presented in our study indicates a positive correlation between
the frequency of PP and the extent of improvement in oxygenation.
Specifically, the oxygenation index continued to rise for a duration of
6 hours following the conclusion of the initial PP, with the most
significant increase observed during the second PP. Among the 14
patients, the second PP resulted in the highest increase in oxygenation
index (ranging from 109 mmHg to 373 mmHg), and 4 patients achieved
normal levels of oxygenation index.
Previous research has established[16, 17] the efficacy of PP in
enhancing the oxygenation index among patients. In a retrospective
analysis conducted by Tyler T. Weiss et al [7], involving 42
COVID-19 patients receiving invasive mechanical ventilation, it was
observed that repeated PP yielded a more significant improvement in
oxygenation. However, the impact of varying frequencies of PP on
oxygenation alteration remained inconclusive. Our study, on the other
hand, determined that PP1 exhibited the longest duration of oxygenation,
while PP2 demonstrated the most substantial increase in oxygenation
levels for the majority of patients.
The current study provides evidence that PP can effectively mitigate the
severity of COVID-19 in critically ill patients who require invasive
mechanical ventilation. Previous research has demonstrated the utility
of the SOFA score in evaluating disease severity among mechanically
ventilated patients. In this study, approximately half of the patients
experienced a decrease in their SOFA score following treatment with PP.
Notably, nearly one-third of the patients exhibited a reduction in SOFA
score exceeding 20%, while another one-third did not demonstrate any
improvement in their SOFA score.
Patients who did not experience any improvement in SOFA score exhibited
a significantly longer average duration between their admission to ICU
and the commencement of PP (3day vs 1day). Additionally, these
patients had a shorter average duration of each PP (15.5h vs22.0h). Previous research studies[20, 21] have demonstrated that PP
enhances oxygenation in patients, yet it remains uncertain whether PP
effectively reduces the severity of the disease. We hypothesize that the
alteration in disease severity among patients may be associated with the
start time and duration of PP interventions.
Furthermore, a comparison was conducted between patients who exhibited
improvement and survival in the initial three PP oxygenation indices and
those who did not. The findings revealed that the duration of PP was
significantly longer in patients who demonstrated improvement in the
initial three PP oxygenation indices. Previous studies [22, 23] have
also reported that early and prolonged implementation of PP may yield
enhanced oxygenation outcomes in individuals afflicted with
COVID-19-induced lung infections.
Okin et al. [24] conducted a study involving 157 patients with
neocoronary who were subjected to invasive mechanical ventilation. Their
analysis revealed that extended durations of PP (≥24h) led to notable
enhancements in respiratory compliance, oxygenation indices, as well as
30-day and 90-day survival rates. The researchers concluded that
recurrent supine positioning could potentially exacerbate atelectasis
injury and ventilator-induced lung injury. Consequently, they suggest
that initiating and prolonging PP may offer greater benefits in terms of
improving oxygenation.
In the present study, it was observed that lymphocyte counts could
potentially serve as a useful indicator for assessing the efficacy of
PP. The collected data revealed that patients who demonstrated
improvement and survival after undergoing the initial three sessions of
PP with oxygenation exhibited higher WBC and lymphocyte counts upon
admission to the ICU compared to those who did not experience any
enhancement in oxygenation. Furthermore, it was observed that the
lymphocyte counts of patients who failed to exhibit any improvement in
oxygenation were consistently ≤0.5 × 109/L. Previous studies [25,
26] have demonstrated that lymphocyte count serves as a valuable and
dependable measure for assessing the severity of COVID-19. Patients with
severe COVID-19 exhibit compromised cellular immune function, resulting
in a diminished lymphocyte count.
However, the current body of academic literature exhibits a dearth of
information pertaining to the correlation between lymphocyte counts and
PP. In a prospective study undertaken by Coppo et al. [27], it was
discovered that an active inflammatory response was linked to a more
advantageous PP oxygenation index. Our contention is that PP might
exhibit diminished efficacy in patients with diminished lymphocyte
counts and compromised immune systems.
This study is a retrospective investigation conducted on a limited
sample size. The participants of this study consisted of critically ill
patients diagnosed with COVID-19, who were receiving invasive mechanical
ventilation in ICU. These patients exhibited more severe and intricate
medical conditions, as well as a higher number of influencing factors.
However, we conducted the study in which we included PPs from three
general hospitals simultaneously.The relevant information and inspection
data was complete. Additionally, we employed a 1:1 PSM analysis to
ensure comparability between the PP group and non-PP group, thereby
minimizing differences in objective factors. We then dynamically
compared the oxygenation index, disease severity, and survival rate
between the two groups throughout their hospitalization, thus presenting
the impact of PP in a comprehensive and multi-faceted manner across
multiple centers.