Ventilatory efficiency in combination with peak oxygen uptake improves risk stratification in patients undergoing lobectomy

Different measures of ventilatory efficiency in preoperative cardiopulmonary exercise testing are useful for predicting postoperative complications in abdominal cancer surgery

BACKGROUND

Ventilation as a function of elimination of CO2 during incremental exercise (VE/VCO2 slope) has been shown to be a valuable predictor of complications and death after major non-cardiac surgery. VE/VCO2 slope and partial pressure of end-tidal carbon dioxide (PetCO2) are both affected by ventilation/perfusion mismatch, but research on the utility of PetCO2 for risk stratification in major abdominal surgery is limited.

AIM

We aimed to determine the correlation between VE/VCO2 slope and PetCO2 measured during preoperative cardiopulmonary exercise testing (CPET) and its association with major cardiopulmonary complications (MCPCs) or death following oesophageal and other major abdominal cancer surgeries.

METHOD

In a retrospective cohort of 116 patients undergoing preoperative CPET 2008-2023, VE/VCO2 slope and PetCO2 (kPa) were recorded. The main outcome was MCPC during hospitalisation or death ≤90 days of surgery. We determined threshold values for each measure, corresponding to 90% specificity, using receiver operating characteristics analysis.

RESULTS

A strong negative correlation was found between PetCO2 after a 5-minute warm-up and VE/VCO2 slope (Pearson r = -.88). In oesophagus cancer, VE/VCO2 slope >38 and PetCO2 < 4.1 kPa (30.8 mmHg) were both significant thresholds for the main outcome. For other major abdominal surgery patients, threshold analyses were non-significant. The area under the curve to predict outcome was similar using VE/VCO2 slope (0.70, 95% confidence interval 0.51-0.89) as compared to PetCO2 (0.71, 0.53-0-90).

CONCLUSION

Both preoperative VE/VCO2 slope and PetCO2 could identify subjects with a very high risk of complications following oesophageal resection, with similar prognostic utility. PetCO2 can be measured with simpler equipment and could therefore be useful when CPET is not available.

Ventilatory efficiency as a prognostic factor for postoperative complications in patients undergoing elective major surgery: a systematic review

BACKGROUND

Major surgery is associated with high complication rates. Several risk scores exist to assess individual patient risk before surgery but have limited precision. Novel prognostic factors can be included as additional building blocks in existing prediction models. A candidate prognostic factor, measured by cardiopulmonary exercise testing, is ventilatory efficiency (VE/VCO2). The aim of this systematic review was to summarise evidence regarding VE/VCO2 as a prognostic factor for postoperative complications in patients undergoing major surgery.

METHODS

A medical library specialist developed the search strategy. No database-provided limits, considering study types, languages, publication years, or any other formal criteria were applied to any of the sources. Two reviewers assessed eligibility of each record and rated risk of bias in included studies.

RESULTS

From 10,082 screened records, 65 studies were identified as eligible. We extracted adjusted associations from 32 studies and unadjusted from 33 studies. Risk of bias was a concern in the domains 'study confounding' and 'statistical analysis'. VE/VCO2 was reported as a prognostic factor for short-term complications after thoracic and abdominal surgery. VE/VCO2 was also reported as a prognostic factor for mid- to long-term mortality. Data-driven covariable selection was applied in 31 studies. Eighteen studies excluded VE/VCO2 from the final multivariable regression owing to data-driven model-building approaches.

CONCLUSIONS

This systematic review identifies VE/VCO2 as a predictor for short-term complications after thoracic and abdominal surgery. However, the available data do not allow conclusions about clinical decision-making. Future studies should select covariables for adjustment a priori based on external knowledge.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO (CRD42022369944).

Increased minute ventilation-to-carbon dioxide slope during cardiopulmonary exercise test is associated with poor postoperative outcome following lung cancer resection

OBJECTIVES

Ventilatory efficiency [minute ventilation-to-carbon dioxide output slope (VE/VCO2 slope)] can be measured at sub-maximal workload during cardiopulmonary exercise test. The aim of this study is to assess the association between VE/VCO2 slope and outcome after lung cancer resections.

METHODS

Retrospective, single-centre analysis on all patients undergoing lung resection for cancer (April 2014-August 2022) and with a preoperative cardiopulmonary exercise test. VE/VCO2 slope >40 was chosen as high-risk threshold. Logistic regression analysis was used to test the association of VE/VCO2 slope and several patient- and surgery-related factors with 90-day mortality.

RESULTS

A total of 552 patients were included (374 lobectomies, 81 segmentectomies, 55 pneumonectomies and 42 wedge resections). Seventy-four percent were minimally invasive procedures. Cardiopulmonary morbidity was 32%, in-hospital/30-day mortality 6.9% and 90-day mortality 8.9%. A total of 137 patients (25%) had a slope of >40. These patients were older (72 vs 70 years, P = 0.012), had more frequently coronary artery disease (17% vs 10%, P = 0.028), lower carbon monoxide lung diffusion capacity (57% vs 68%, P < 0.001), lower body mass index (25.4 vs 27.0 kg/m2, P = 0.001) and lower peak VO2 (14.9 vs 17.0 ml/kg/min, P < 0.001) than those with a lower slope. The cardiopulmonary morbidity among patients with a slope of >40 was 40% vs 29% in those with lower slope (P = 0.019). Ninety-day mortality was 15% vs 6.7% (P = 0.002). The 90-day mortality of elderly patients with slope >40 was 21% vs 7.8% (P = 0.001). After adjusting for peak VO2 value, extent of operation and other patient-related variables in a logistic regression analysis, VE/VCO2 slope retained a significant association with 90-day mortality.

CONCLUSIONS

VE/VCO2 slope was strongly associated with morbidity and mortality following lung resection and should be included in the functional algorithm to assess fitness for surgery.

VE/VCO2 slope threshold optimization for preoperative evaluation in lung cancer surgery: identifying true high- and low-risk groups

Background

Cardiopulmonary exercise testing (CPET) enables measurement of the slope of the increase in minute ventilation in relation to carbon dioxide elimination during exercise (the VE/VCO2 slope). Several studies have shown that the VE/VCO2 slope is a strong marker for postoperative complications and mortality. However, current thresholds for adverse outcomes are generated from historical data in heart failure patients.

Methods

This was a retrospective analysis of 158 patients with lung cancer who underwent lobectomy or pneumonectomy during 2008-2020. The main outcome was major pulmonary complications (MPC) or death ≤30 days of cancer surgery. Patients were first categorized using two different single threshold approaches; the traditional threshold of 35 and the highest Youden value from the receiver operating curve (ROC) analysis. Secondly, patients were categorized into three risk groups using two thresholds. These two thresholds were determined in an ROC analysis, where the VE/VCO2 slope values generating either a 90% sensitivity (lower threshold) or a 90% specificity (upper threshold) for the main outcome were chosen. The frequency of complications was compared using Chi2. The overall model quality was evaluated by an area under the curve (AUC) analysis. Positive predictive values (PPVs) and negative predictive values (NPVs) are presented.

Results

The two thresholds, <30 (90% sensitivity) and >41 (90% specificity), created three risk groups: low risk (VE/VCO2 slope <30, n=44, 28%); intermediate risk (VE/VCO2 slope 30-41, n=95, 60%) and high risk (VE/VCO2 slope >41, n=19, 12%). The frequency of complications differed between groups: 5%, 16% and 47% (P<0.001). Using two thresholds compared to one threshold increased the overall model quality (reaching AUC 0.70, 95% confidence interval: 0.59-0.81), and identified a high sensitivity threshold (VE/VCO2 slope <30) which generated a NPV of 95% but importantly, also a high specificity threshold (VE/VCO2 slope >41) with a PPV of 47%.

Conclusions

Risk stratification based on three risk groups from the preoperative VE/VCO2 slope increased the model quality, was more discriminative and generated better PPV and NPV compared to traditional risk stratification into two risk groups.

Peak oxygen uptake in combination with ventilatory efficiency improve risk stratification in major abdominal surgery

This pilot study aimed to evaluate if peak VO2 and ventilatory efficiency in combination would improve preoperative risk stratification beyond only relying on peak VO2 . This was a single-center retrospective cohort study including all patients who underwent cardiopulmonary exercise testing (CPET) as part of preoperative risk evaluation before major upper abdominal surgery during years 2008-2021. The primary outcome was any major cardiopulmonary complication during hospitalization. Forty-nine patients had a preoperative CPET before decision to pursue to surgery (cancer in esophagus [n = 18], stomach [6], pancreas [16], or liver [9]). Twenty-five were selected for operation. Patients who suffered any major cardiopulmonary complication had lower ventilatory efficiency (i.e., higher VE/VCO2 slope, 37.3 vs. 29.7, p = 0.031) compared to those without complications. In patients with a low aerobic capacity (i.e., peak VO2  < 20 mL/kg/min) and a VE/VCO2 slope ≥ 39, 80% developed a major cardiopulmonary complication. In this pilot study of patients with preoperative CPET before major upper abdominal surgery, patients who experienced a major cardiopulmonary complication had significantly lower ventilatory efficiency compared to those who did not. A low aerobic capacity in combination with low ventilatory efficiency was associated with a very high risk (80%) of having a major cardiopulmonary complication.

The Year in Thoracic Anesthesia: Selected Highlights from 2022

This article reviews research highlights in the field of thoracic anesthesia. The highlights of this year included new developments in the preoperative assessment and prehabilitation of patients requiring thoracic surgery, updates on the use of devices for one-lung ventilation (OLV) in adults and children, updates on the anesthetic and postoperative management of these patients, including protective OLV ventilation, the use of opioid-sparing techniques and regional anesthesia, and outcomes using enhanced recovery after surgery, as well as the use of expanding indications for extracorporeal membrane oxygenation, specialized anesthetic techniques for airway surgery, and nonintubated video-assisted thoracic surgery.

Prognostic role of minute ventilation/carbon dioxide production slope for perioperative morbidity and long-term survival in resectable patients with nonsmall-cell lung cancer: a prospective study using propensity score overlap weighting

BACKGROUND

The role of minute ventilation/carbon dioxide production ( / CO 2 ) slope, a ventilation efficiency marker, in predicting short-term and long-term health outcomes for patients with nonsmall-cell lung cancer (NSCLC) undergoing lung resection has not been well investigated.

MATERIAL AND METHODS

This prospective cohort study consecutively enrolled NSCLC patients who underwent a presurgical cardiopulmonary exercise test from November 2014 to December 2019. The association of / CO 2 slope with relapse-free survival (RFS), overall survival (OS), and perioperative mortality was evaluated using the Cox proportional hazards and logistic models. Covariates were adjusted using propensity score overlap weighting. The optimal cut-off point of the E/ CO 2 slope was estimated using the receiver operating characteristics curve. Internal validation was completed through bootstrap resampling.

RESULTS

A cohort of 895 patients [median age (interquartile range), 59 (13) years; 62.5% male] was followed for a median of 40 (range, 1-85) months. Throughout the study, there were 247 relapses or deaths and 156 perioperative complications. The incidence rates per 1000 person-years for relapses or deaths were 108.8 and 79.6 among patients with high and low E/ CO 2 slopes, respectively [weighted incidence rate difference per 1000 person-years, 29.21 (95% CI, 7.30-51.12)]. A E/ CO 2 slope of greater than or equal to 31 was associated with shorter RFS [hazard ratio for relapse or death, 1.38 (95% CI, 1.02-1.88), P =0.04] and poorer OS [hazard ratio for death, 1.69 (1.15-2.48), P =0.02] compared to a lower / CO 2 slope. A high E/ CO 2 slope increased the risk of perioperative morbidity compared with a low E/ CO 2 slope [odds ratio, 2.32 (1.54-3.49), P <0.001].

CONCLUSIONS

In patients with operable NSCLC, a high E/ CO 2 slope was significantly associated with elevated risks of poorer RFS, OS, and perioperative morbidity.

Early outcomes of “low-risk” patients undergoing lung resection assessed by cardiopulmonary exercise testing: Single-institution experience

Objective

Cardiopulmonary exercise testing (CPET) is currently recommended for all patients undergoing lung resection with either respiratory comorbidities or functional limitations. The main parameter evaluated is oxygen consumption at peak (VO2peak). Patients with VO2peak above 20 ml/kg/min are classified as low risk surgical candidates. The aims of this study were to evaluate postoperative outcomes of low-risk patients, and to compare their outcomes with those of patients without pulmonary impairment at respiratory function testing.

Methods

Retrospective monocentric observational study was designed, evaluating outcomes of patients undergoing lung resection at San Paolo University Hospital, Milan, Italy, between January 2016 and November 2021, preoperatively assessed by CPET, according to 2009 ERS/ESTS guidelines. All low-risk patients undergoing any extent surgical lung resection for pulmonary nodules were enrolled. Postoperative major cardiopulmonary complications or death, occurring within 30 days from surgery, were assessed. A case-control study was nested, matching 1:1 for type of surgery the cohort population with control patients without functional respiratory impairment consecutively undergoing surgery at the same centre in the study period.

Results

A total of 80 patients were enrolled: 40 subjects were preoperatively assessed by CPET and deemed at low risk, whereas 40 subjects represented the control group. Among the first, 4 patients (10%) developed major cardiopulmonary complications, and 1 patient (2.5%) died within 30 days from surgery. In the control group, 2 patients (5%) developed complications and none of the patients (0%) died. The differences in morbidity and mortality rates did not reach statistically significance. Instead, age, weight, BMI, smoking history, COPD incidence, surgical approach, FEV1, Tiffenau, DLCO and length of hospital stay resulted significantly different between the two groups. At a case-by-case analysis, CPET revealed a pathological pattern in each complicated patient, in spite of VO2peak above target for safe surgery.

Conclusions

Postoperative outcomes of low-risk patients undergoing lung resections are comparable to those of patients without any pulmonary functional impairment; nonetheless the formers represent a dramatically different category of individuals from the latter and may harbour few patients with worse outcomes. CPET variables overall interpretation may add to the VO2peak in identifying higher risk patients, even in this subgroup.

Multimodal prehabilitation for major surgery in elderly patients to lower complications: protocol of a randomised, prospective, multicentre, multidisciplinary trial (PREHABIL Trial)

INTRODUCTION

The global volume of surgery is growing and the population ageing, and economic pressure is rising. Major surgery is associated with relevant morbidity and mortality. Postoperative reduction in physiological and functional capacity is especially marked in the elderly, multimorbid patient with low fitness level, sarcopenia and malnutrition. Interventions aiming to optimise the patient prior to surgery (prehabilitation) may reduce postoperative complications and consequently reduce health costs.

METHODS AND ANALYSIS

This is a multicentre, multidisciplinary, prospective, 2-arm parallel-group, randomised, controlled trial with blinded outcome assessment. Primary outcome is the Comprehensive Complications Index at 30 days. Within 3 years, we aim to include 2×233 patients with a proven fitness deficit undergoing major surgery to be randomised using a computer-generated random numbers and a minimisation technique. The study intervention consists of a structured, multimodal, multidisciplinary prehabilitation programme over 2-4 weeks addressing deficits in physical fitness and nutrition, diabetes control, correction of anaemia and smoking cessation versus standard of care.

ETHICS AND DISSEMINATION

The PREHABIL trial has been approved by the responsible ethics committee (Kantonale Ethikkomission Bern, project ID 2020-01690). All participants provide written informed consent prior to participation. Participant recruitment began in February 2022 (10 and 8 patients analysed at time of submission), with anticipated completion in 2025. Publication of the results in peer-reviewed scientific journals are expected in late 2025.

TRIAL REGISTRATION NUMBER

NCT04461301.