Preoperative and intraoperative oxygen consumption in patients undergoing lung resection surgery: a retrospective study using cardiopulmonary exercise test and intraoperative data

Figures

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  Fig. 1. Patient flow diagram. CPAP, continuous positive airway pressure; TIVA, total intravenous anesthesia; Hb, hemoglobin

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  Fig. 2. Changes in physiological parameters across CPET stages.Individual trajectories of key physiological parameters were displayed across three standardized stages of cardiopulmonary exercise testing (CPET): rest, anaerobic threshold (AT), and peak exercise. Colored points indicate stage-specific values, with each dotted line connecting measurements from the same subject. The parameters included oxygen consumption (VO₂), metabolic equivalents (METs), heart rate (HR), minute ventilation (VE), ventilatory equivalents for carbon dioxide (VE/VCO₂) and oxygen (VE/VO₂), respiratory exchange ratio (RER), partial pressure of end-tidal carbon dioxide (EtCO₂), and partial pressure of end-tidal oxygen (EtO₂)

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  Fig. 3. Intraoperative trajectories of metabolic equivalents (METs) compared to the METs at rest (preoperative). Time-series plots of intraoperative METs are shown for each patient (Subjects 1–32). Black points represent minute-by-minute estimates of METs during the intraoperative period. The red dashed line indicates each subject’s mean intraoperative METs, while the blue solid line indicates their preoperative resting METs, as determined from CPET. Despite minor within-subject fluctuations, intraoperative metabolic demand generally remained consistent over time, typically below or near resting levels

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  Fig. 4. Relationship between heart rate and metabolic equivalents (METs) during preoperative cardiopulmonary test (CPET) and intraoperative period. This figure depicts the relationship between the heart rate (HR, bpm) and oxygen consumption (expressed as metabolic equivalents [METs]) for each patient (n = 32), combining data from two distinct physiological contexts: preoperative CPET and intraoperative monitoring. Three CPET stages—resting (blue circle), anaerobic threshold (green square), and peak exercise (red triangle)—are connected with dotted lines to illustrate the progression of cardiovascular and metabolic demands during exercise. The intraoperative mean (black downward triangle) represents the average value obtained under general anesthesia. Across patients, intraoperative HR and METs consistently clustered near or below the CPET resting state, indicating a substantial reduction in the metabolic and cardiovascular demand during anesthesia

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  Fig. 5. Correlation between resting and intraoperative oxygen consumption (VO2).Scatter plots illustrating the relationship between preoperative resting and intraoperative VO2. Each dot represents a single patient. No significant correlation was observed between the resting and intraoperative VO₂ levels (left). However, a strong positive correlation was found between resting VO₂ and the reduction in intraoperative VO₂ (right). Consequently, regardless of preoperative resting VO₂, intraoperative VO₂ converged to a relatively narrow range, averaging 1.1 ± 0.2 METs. Abbreviations: VO₂, oxygen consumption; ΔVO₂, reduction in VO₂ (i.e., difference between resting and intraoperative mean values); METs, metabolic equivalents