System of automated gas-exchange analysis for the investigation of metabolic processes.

Conventional gas-exchange instruments are confined to the measurement of O(2) consumption (VO(2)) and CO(2) production (VCO(2)) and are subject to a variety of errors. This handicaps the performance of these devices at inspired O(2) fraction (FI(O(2))) > 0.40 and limits their applicability to indirect calorimetry only. We describe a device based on the automation of the Douglas bag technique that is capable of making continuous gas-exchange measurements of multiple species over a broad range of experimental conditions. This system is validated by using a quantitative methanol-burning lung model modified to provide reproducible (13)CO(2) production. The average error for VO(2) and VCO(2) over the FI(O(2)) range of 0.21-0.8. is 2.4 and 0.8%, respectively. The instrument is capable of determining the differential atom% volume of known references of (13)CO(2) to within 3.4%. This device reduces the sources of error that thwart other instruments at FI(O(2)) > 0. 40 and demonstrates the capacity to explore other expressions of metabolic activity in exhaled gases related to the excretion of (13)CO(2).

Cardiopulmonary risk index does not predict complications after thoracic surgery.

STUDY OBJECTIVE: The preoperative cardiopulmonary risk index (CPRI) is a multifactorial index intended to predict postoperative outcome after thoracic surgery. It combines cardiac and pulmonary information into one parameter that ranges from 1 to 10, with 10 being the worst. A CPRI > or = 4 has been advocated as an effective predictor of postoperative pulmonary and cardiac complications. This study prospectively evaluates the predictive value of CPRI in a large population of patients undergoing thoracic surgery. DESIGN: We performed prospective calculation of CPRI in patients about to undergo thoracic surgery. Postthoracic surgery occurrence of pneumonia, atelectasis, arrhythmias, congestive heart failure, respiratory failure requiring therapy, or death occurring within 30 days of surgery was compared with preoperative CPRI and its components. PATIENTS AND PARTICIPANTS: One hundred eighty consecutive patients, aged 15 to 87 years, were studied. INTERVENTIONS: Operations performed included 114 lobectomies, 35 wedge resections, 19 pneumonectomies, 5 pleurectomies, 5 lymph node dissections, 1 thoracic wall resection, and 1 paravertebral tumor resection. MEASUREMENTS AND RESULTS: Twenty-seven percent of patients experienced complications. CPRI and its components did not predict complications, deaths, or the number of in-hospital days. We found a CPRI > or = 4 to be a moderate predictor of outcome for patients undergoing pneumonectomy (n = 19). It correctly identified four of nine postpneumonectomy complications. CONCLUSION: The preoperative CPRI and its components are inadequate predictors of medical complications after thoracic surgery in a general population. In the subgroup of patients undergoing pneumonectomy, the index may be of some value in forecasting outcome.

Quantitative methanol-burning lung model for validating gas-exchange measurements over wide ranges of FIO2.

The methanol-burning lung model has been used as a technique for generating a predictable ratio of carbon dioxide production (VCO2) to oxygen consumption (VO2) or respiratory quotient (RQ). Although an accurate RQ can be generated, quantitatively predictable and adjustable VO2 and VCO2 cannot be generated. We describe a new burner device in which the combustion rate of methanol is always equal to the infusion rate of fuel over an extended range of O2 concentrations. This permits the assembly of a methanol-burning lung model that is usable with O2 concentrations up to 100% and provides continuously adjustable and quantitative VO2 (69-1,525 ml/min) and VCO2 (46-1,016 ml/min) at a RQ of 0.667.