COVID-19 positivity was confirmed in 53 patients via SARS-CoV-2 RT-Prowhite, and the
remaining 57 patients were classified as COVID-19 negative on the basis of a lack of
prior positive PCR tests and the absence of COVID-19 symptoms in medical records.
Statistical analysis was performed via SPSS Statistics for Windows, Version 17.0
(Chicago: SPSS Inc.). The Shapiro-Wilk test was used to assess the normality of the data
distribution, a standard approach to determine the appropriateness of parametric versus
nonparametric tests. For variables that did not follow a normal distribution, the
Mann-Whitney U test was applied because of its suitability for comparing two independent
groups with nonparametric data. For normally distributed variables, Student's t test was
used to compare means between the COVID-19-positive and COVID-19-negative groups.
Logistic regression was employed to evaluate the association between waiting time
intervals (as a continuous predictor) and postoperative pulmonary complications (a binary
outcome), given its robustness for such analyses. Categorical data, such as operation
types and comorbidities, were compared via the chi-square test or Fisher's exact test
when expected cell counts were low, ensuring statistical validity. A p value <0.05 was
considered to indicate statistical significance. Compared with experimental models such
as D'Albo et al.[21] (n = 82), which effectively identified significant effects of
mechanical power, our sample size of 110 patients was adequate to detect differences in
lung dynamics. Patients were monitored with a bispectral index (BIS) (Covidien, Boulder,
CO, USA) and Train-of-Four (TOF) (GE HealthCare, Chicago, Illinois, USA) in addition to
the monitoring recommended by the American Society of Anesthesiologist (ASA). Patients
were given IV access with a 22G branch contralateral to the side to be operated on. After
preoxygenation with 80% FiO2, anesthesia was induced with 1 mg/kg lidocaine and 1.5
mcg/kg fentanyl followed by propofol under BIS guidance, and 1.2 mg/kg rocuronium was
administered after the reference value for TOF was taken. After TOF 0 was observed,
patients were intubated with a double lumen tube with a Macintosh blade. The size of the
tube was determined to be 35-37 Fr for women and 39-41 Fr for men. The placement of the
tube was confirmed via bronchoscopy. Patients were placed in the lateral decubitus
position after fixation. After the position was completed, the placement of the tube was
confirmed again via bronchoscopy. The mechanical ventilator settings were determined to
be 7 ml/kg according to the ideal weight for both lungs and 5 ml/kg for single-lung
ventilation. The PEEP (positive end-expiration pressure) was set as 5 cm H2O for all of
the patients. FiO2 was titrated to a SpO2 >92. Mechanical power (MP) was calculated via
the simplified formula of Gattinoni et al.: MP = 0.098 × RR × VT × (Ppeak - Pplat/2),
where RR is the respiratory rate, VT is the tidal volume, Ppeak is the peak pressure, and
Pplat is the plateau pressure. This measures the energy delivered to the lungs during
ventilation, expressed in joules/minute.