Adaptive non-invasive ventilation treatment for sleep apnea.

The purpose of this study was to investigate the effectiveness of two non-invasive mechanical ventilation (NIV) modalities to treat sleep apnea: (1) Average Volume Assured Pressure Support (AVAPS) NIV, and (2) Pressure Support (PS) NIV with Continuously Calculated Average Required Ventilation (CCARV). Two detailed (previously developed and tested) simulation models were used to assess the effectiveness of the NIV modalities. One simulated subjects without chronic obstructive pulmonary disease (COPD), and the other simulated patients with COPD. Sleep apnea was simulated in each model (COPD and Non-COPD), and the ability of each NIV modality to normalize breathing was measured. In both NIV modalities, a low level continuous positive airway pressure was used and a backup respiratory rate was added to the algorithm in order to minimize the respiratory work rate. Both modalities could help normalize breathing in response to an episode of sleep apnea within about 5 min (during which time blood gases were within safe limits). AVAPS NIV and PS NIV with CCARV have potential value to be used for treatment of sleep apnea. Clinical evaluations are needed to fully assess the effectiveness of these NIV modalities.

Non-invasive ventilation treatment for patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) affects the lives of millions of patients worldwide. Patients with advanced COPD may require non-invasive ventilation (NIV) to support the resultant deficiencies of the respiratory system. The purpose of this study was to evaluate the effects of varying the continuous positive airway pressure (CPAP) and oxygen supplementation components of NIV on simulated COPD patients by using an established and detailed model of the human respiratory system. The model used in the study simulates features of advanced COPD including the effects on the changes in ventilation control, increases in respiratory dead space and airway resistance, and the acid-base shifts in the blood seen in these patients over time. The results of the study have been compared with and found to be in general agreement with available clinical data. Our results demonstrate that under non-emergency conditions, low levels of oxygen supplementation combined with low levels of CPAP therapy seem to improve hypoxemia and hypercapnia in the model, whereas prolonged high-level CPAP and moderate-to-high levels of oxygen supplementation do not. The authors conclude that such modelling may be useful to help guide beneficial interventions for COPD patients using NIV.

S-nitrosoglutathione preserves platelet function during in vitro ventricular assist device circulation.

Complications (severe bleeding/thromboembolism) may occur during ventricular assist device (VAD) circulation, caused mainly by platelet dysfunction from platelet activation. We hypothesized that S-nitrosoglutathione (GSNO), having platelet activity preservation properties like nitric oxide (NO), may be a titratable agent to diminish platelet activation and thus preserve platelet function. Dose-response measurement of platelet aggregation by GSNO was performed using an aggregometer. GSNO (1,000 microM) caused inhibition of collagen and ristocetin induced aggregation by approximately 50%. Next, in vitro ventricular assist device (VAD) circulation was performed (over 48 hours using human whole blood), both without (control) and with GSNO (1,000 microM), and the aggregability of perfusate was measured at 0, 0.5, 1, 3, 6, 12, 24, and 48 hours. In control VAD circuits, collagen induced platelet aggregability gradually decreased and became significantly lower after 3 hours of circulation. With GSNO, platelet function did not significantly decrease until after 12 hours. Similar results were seen for ristocetin induced aggregation; control aggregation dropped significantly after 6 hours, but not until after 24 hours with GSNO. Liquid phase measurement of total nitrogen oxides (NO(T)) confirmed added GSNO maintained high perfusate NO(T) compared with control. GSNO is effective in preserving platelet aggregation during the first 12 to 24 hours in vitro and may be effective in preserving platelet function by inhibiting platelet activation during in vivo VAD circulation.

Flex: a new computerized system for mechanical ventilation.

OBJECTIVE: To describe and evaluate a new weaning and decision support system for mechanical ventilation. BACKGROUND: FLEX is a computerized weaning and decision support system for mechanical ventilation that unlike previous rule-based systems derives many of its rules on the basis of the conditions of individual patients. This system can be used in a wide range of ventilatory modes as well as automatic control of weaning. It incorporates the features of the patented ventilatory mode known as Adaptive Support Ventilation (ASV) along with other new features for control of weaning, and control of patient's oxygenation by adjustment of PEEP and the fraction of inspired oxygen. METHODS: Ventilator data was collected for 10 patients in medical/surgical ICU at baseline and about 24 hours later. Required data fields for each patient for these two time points were also entered into the FLEX program. Comparison of clinical data and FLEX recommendations were made with regard to minute ventilation, alarms, weaning institution and other variables. RESULTS: At baseline, 7 patients were being treated with AC, the remainder with IMV/PS. There was good agreement between the measured and recommended minute ventilations; variances were seen in some patients being treated with permissive hypercapnea and those with evidence of high oxygen needs or other metabolic derangements. At 24 hours, there was improved correlation between measured minute ventilation and that recommended by FLEX, suggesting that clinical adjustments were in-line with Flex recommendations over time. Furthermore, FLEX made recommendations with regard to FIO(2) and PEEP that would potentially diminish the risk of oxygen toxicity, hypoxemia, and barotrauma in selected patients. FLEX has also been implemented as a closed loop system in an initial set up. CONCLUSION: A new weaning and decision support system for mechanical ventilation is presented. The recommendations made by the system were found to be in line with clinical determinations. Further refinements in the FLEX predictions can be easily made by including inputs which represent permissive hypercapnea or increased metabolic demand for selected patients.

Intelligent decision support systems for mechanical ventilation.

OBJECTIVE: An overview of different methodologies used in various intelligent decision support systems (IDSSs) for mechanical ventilation is provided. The applications of the techniques are compared in view of today's intensive care unit (ICU) requirements. METHODS: Information available in the literature is utilized to provide a methodological review of different systems. RESULTS: Comparisons are made of different systems developed for specific ventilation modes as well as those intended for use in wider applications. The inputs and the optimized parameters of different systems are discussed and rule-based systems are compared to model-based techniques. The knowledge-based systems used for closed-loop control of weaning from mechanical ventilation are also described. Finally, in view of increasing trend towards automation of mechanical ventilation, the potential utility of intelligent advisory systems for this purpose is discussed. CONCLUSIONS: IDSSs for mechanical ventilation can be quite helpful to clinicians in today's ICU settings. To be useful, such systems should be designed to be effective, safe, and easy to use at patient's bedside. In particular, these systems must be capable of noise removal, artifact detection and effective validation of data. Systems that can also be adapted for closed-loop control/weaning of patients at the discretion of the clinician, may have a higher potential for use in the future.