Alfredo Lissoni

The effects of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia

We investigated the effects of body mass index (BMI) on functional residual capacity (FRC), respiratory mechanics (compliance and resistance), gas exchange, and the inspiratory mechanical work done per liter of ventilation during general anesthesia.We used the esophageal balloon technique, together with rapid airway occlusion during constant inspiratory flow, to partition the mechanics of the respiratory system into its pulmonary and chest wall components. FRC was measured by using the helium dilution technique. We studied 24 consecutive and unselected patients during general anesthesia, before surgical intervention, in the supine position (8 normal subjects with a BMI <or=to25 kg/m2, 8 moderately obese patients with a BMI >25 kg/m2 and <40 kg/m2, and 8 morbidly obese patients with a BMI >or=to40 kg/m2). We found that, with increasing BMI: 1.FRC decreased exponentially (r = 0.86; P < 0.01) 2.the compliance of the total respiratory system and of the lung decreased exponentially (r = 0.86; P < 0.01 and r = 0.81; P < 0.01, respectively), whereas the compliance of the chest wall was only minimally affected (r = 0.45; P < 0.05) 3.the resistance of the total respiratory system and of the lung increased (r = 0.81; P < 0.01 and r = 0.84; P < 0.01, respectively), whereas the chest wall resistance was unaffected (r = 0.06; P = not significant) 4.the oxygenation index (PaO2/PAo2) decreased exponentially (r = 0.81; P < 0.01) and was correlated with FRC (r = 0.62; P < 0.01), whereas PaCO2 was unaffected (r = 0.06; P = not significant) 5.the work of breathing of the total respiratory system increased, mainly due to the lung component (r = 0.88; P < 0.01 and r = 0.81; P < 0.01, respectively). In conclusion, BMI is an important determinant of lung volumes, respiratory mechanics, and oxygenation during general anesthesia with patients in the supine position.Implications: The aim of this study was to investigate the influence of body mass on lung volumes, respiratory mechanics, and gas exchange during general anesthesia. (Anesth Analg 1998;87:654-60)

Organ Allocation Waiting Time During Extracorporeal Bridge to Lung Transplant Affects Outcomes

BACKGROUND The use of extracorporeal membrane oxygenation (ECMO) as a bridge to lung transplant (LTX) is still being debated. METHODS We performed a retrospective two-center analysis of the relationship between ECMO bridging duration and survival in 25 patients. Further survival analysis was obtained by dividing the patients according to waiting time on ECMO: up to 14 days (Early group) or longer (Late group). We also analyzed the impact of the ventilation strategy during ECMO bridging (ie, spontaneous breathing and noninvasive ventilation [NIV] or intubation and invasive mechanical ventilation [IMV]). RESULTS Seventeen of 25 patients underwent a transplant (with a 76% 1-year survival), whereas eight patients died during bridging. In the 17 patients who underwent a transplant, mortality was positively related to waiting days until LTX (hazard ratio [HR], 1.12 per day; 95% CI, 1.02-1.23; P = .02), and the Early group showed better Kaplan-Meier curves (P = .02), higher 1-year survival rates (100% vs 50%, P = .03), and lower morbidity (days on IMV and length of stay in ICU and hospital). During the bridge to transplant, mortality increased steadily with time. Considering the overall outcome of the bridging program (25 patients), bridge duration adversely affected survival (HR, 1.06 per day; 95% CI, 1.01-1.11; P = .015) and 1-year survival (Early, 82% vs Late, 29%; P = .015). Morbidity indexes were lower in patients treated with NIV during the bridge. CONCLUSIONS The duration of the ECMO bridge is a relevant cofactor in the mortality and morbidity of critically ill patients awaiting organ allocation. The NIV strategy was associated with a less complicated clinical course after LTX.

Simulation-Based Training of Extracorporeal Membrane Oxygenation During H1N1 Influenza Pandemic: The Italian Experience

&NA; On November 2009, the Italian health authorities set up a network of selected intensive care unit (ICU) centers (ECMOnet) to prepare for the treatment of the sickest patients of influenza A (H1N1) by means of extracorporeal membrane oxygenation (ECMO). To quickly and efficaciously train all the physicians working in the ICUs of the ECMOnet on ECMO use, we decided to take advantages of the opportunity provided by simulation technology. Simulation proved efficacious in providing adequate training and education to participants as confirmed by the survival results obtained by the group of ICUs of the ECMOnet. Our experience supports the use of simulation as a valuable alternative to animal laboratory sessions proposed by traditional ECMO training programs providing participants with cognitive, technical, and behavioral skills and allowing a proficient transfer of those skills to the real medical domain.

Pathophysiology and diagnosis of respiratory acid-base disturbances in patients with critical illness

Acid-base balance may be defined as a status in which, at steady state, the acid-base input in the system equals the acid-base output.

ECMO as a Bridge to Lung Transplant

Patient candidates to lung transplant could die awaiting organ allocation due to the worsening of their end-stage respiratory failure. In recent years, the outcome improvement after lung transplant, a more accurate patient selection and the technological development of simpler and safer extracorporeal systems, has made the use of extracorporeal membrane oxygenation (ECMO) as bridge to lung transplant possible in the critically ill patients. The correct choice of the extracorporeal configuration in function to the pathophysiologic characteristics of the end-stage respiratory failure permits performing lung transplants, even in more severe patients, decreasing perioperative morbidity and mortality.