Integration of Active and Passive Safety Technologies--A Method to Study and Estimate Field Capability.

The objective of this study is to develop a method that uses a combination of field data analysis, naturalistic driving data analysis, and computational simulations to explore the potential injury reduction capabilities of integrating passive and active safety systems in frontal impact conditions. For the purposes of this study, the active safety system is actually a driver assist (DA) feature that has the potential to reduce delta-V prior to a crash, in frontal or other crash scenarios. A field data analysis was first conducted to estimate the delta-V distribution change based on an assumption of 20% crash avoidance resulting from a pre-crash braking DA feature. Analysis of changes in driver head location during 470 hard braking events in a naturalistic driving study found that drivers' head positions were mostly in the center position before the braking onset, while the percentage of time drivers leaning forward or backward increased significantly after the braking onset. Parametric studies with a total of 4800 MADYMO simulations showed that both delta-V and occupant pre-crash posture had pronounced effects on occupant injury risks and on the optimal restraint designs. By combining the results for the delta-V and head position distribution changes, a weighted average of injury risk reduction of 17% and 48% was predicted by the 50th percentile Anthropomorphic Test Device (ATD) model and human body model, respectively, with the assumption that the restraint system can adapt to the specific delta-V and pre-crash posture. This study demonstrated the potential for further reducing occupant injury risk in frontal crashes by the integration of a passive safety system with a DA feature. Future analyses considering more vehicle models, various crash conditions, and variations of occupant characteristics, such as age, gender, weight, and height, are necessary to further investigate the potential capability of integrating passive and DA or active safety systems.

Effects of a Highly Portable Noninvasive Open Ventilation System on Activities of Daily Living in Patients with COPD.

Background: For patients with chronic obstructive pulmonary disease (COPD), an increase in exercise tolerance and ability to perform activities of daily living (ADLs) can mean an improved quality of life with fewer exacerbations and lower health care expenses. We evaluated a wearable, noninvasive open ventilation (NIOV) system designed to enhance exercise capacity and increase mobility. Methods: Patients with stable, oxygen-dependent COPD were recruited for this prospective, open-label, crossover study. Inclusion criteria included supplemental oxygen use, elevated dyspnea score, and the ability to perform ADLs. Patients performed a selected ADL for as long as tolerable while using standard oxygen therapy. Following a rest period, the same ADL was repeated using the NIOV system. ADL endurance time, oxyhemoglobin saturation measured by pulse oximeter ( SpO2), dyspnea, fatigue, and discomfort scores were recorded. Results: Thirty patients were enrolled and 29 patients completed the study. Mean ADL endurance increased by 85% (13.4 vs. 7.2 min) using NIOV compared with oxygen therapy (p<0.0001). Mean SpO2 was significantly higher during ADLs using NIOV versus oxygen therapy (p<0.0001). Median dyspnea, fatigue, and discomfort scores were significantly lower using NIOV during ADLs compared to oxygen therapy (p<0.01). No device-related adverse events were observed. Conclusions: This study demonstrated that a novel, portable noninvasive open ventilation system can improve ADL performance in the home setting. Compared to standard oxygen therapy, the NIOV system provided statistically and clinically significant increases in ADL endurance time and oxygenation, while decreasing dyspnea, fatigue, and discomfort. The NIOV system appears to offer a practical option for increasing activity and exercise tolerance in oxygen-dependent patients with COPD.

Options for home oxygen therapy equipment: storage and metering of oxygen in the home.

Home oxygen therapy equipment options have increased over the past several decades, in response to innovations in technology, economic pressure from third-party payers, and patient demands. The delivery of oxygen in the home has evolved from packaged gas systems containing 99% United States Pharmacopeia oxygen provided by continuous-flow delivery to intermittent-flow delivery, with oxygen concentrators delivering < 99% oxygen purity. The majority of published papers indicating the value of long-term oxygen therapy have been based on continuous-flow delivery of 99% United States Pharmacopeia oxygen. The lack of research on new home oxygen therapy devices requires more clinical involvement from physician and respiratory therapist to evaluate the performance of oxygen devices used in the home to ensure the patient is provided adequate oxygenation at all activity levels. New standards of care are required to address the need to have consistent titration of long-term oxygen therapy to meet the patient's home needs at all activity levels. Consistent labeling of metering devices on home oxygen equipment will need to be developed by professional medical societies to be implemented by standards organizations that direct industrial manufacturers. Home oxygen therapy will need professionally trained respiratory therapists reimbursed for skills and service to ensure that patients receive optimal benefits from home oxygen equipment to improve patient outcomes and prevent complications and associated costs.

Nocturnal oxygenation using a pulsed-dose oxygen-conserving device compared to continuous flow.

BACKGROUND: The pulsed-dose oxygen-conserving device (PDOCD) has gained wide acceptance as a tool to reduce the cost and inconvenience of portable oxygen delivery. Despite the widespread use of PDOCDs in awake and ambulating patients, few studies report their use during sleep. This study was designed to compare heart rate and oxygen saturation (measured via pulse oximetry [S(pO2)]) of sleeping patients using one brand of PDOCD versus continuous-flow oxygen. METHODS: We studied 10 home-oxygen patients who were using various continuous-flow oxygen systems and prescriptions. Baseline asleep and awake S(pO2) and heart rate were recorded while the patients used their existing home-oxygen systems (liquid oxygen or oxygen concentrator with nasal cannula) and continuous-flow oxygen prescription. Patients were then switched to a nasal cannula connected to a PDOCD. The PDOCD setting was adjusted to produce an S(pO2) equal to the patient's awake baseline on continuous-flow. This setting was then used while the patient subsequently slept. Mean values for S(pO2) and heart rate and hours of sleep were calculated by the software in the oximeter. Mean values for S(pO2) and heart rate were compared with the paired Student's t test. RESULTS: There was a statistically significant but clinically unimportant S(pO2) difference between the patients who used continuous-flow oxygen and those who used the PDOCD (95.7% vs 93.2%, respectively, p = 0.043). There was no difference in heart rate (77.3 beats/min vs 77.9 beats/min, p = 0.70). The sample size was adequate to detect a difference in heart rate of 5 beats/min at a power of 80%. For the subset of patients whose PDOCD triggering sensitivity was set on sensitive (vs the default lower sensitivity) there was a statistically significant but clinically unimportant S(pO2) difference (continuous-flow 95.6% vs PDOCD 93.2%, p = 0.044). All other comparisons showed no differences, but the samples sizes were too small to make any firm conclusions. One patient experienced an 11% S(pO2) drop with the PDOCD because of an inadequate triggering sensitivity setting. CONCLUSIONS: The PDOCD model we studied was able to deliver oxygen therapy (via nasal cannula) comparable to continuous-flow in 9 of 10 patients. The resting daytime S(pO2) on continuous-flow appears to be an appropriate target for setting the PDOCD to ensure adequate oxygenation, even during sleep, with the PDOCD we tested. We conclude that the PDOCD we tested is able to maintain adequate S(pO2) during sleep in selected patients. Because of differences in design, triggering-signal sensitivity, and oxygen-pulse volume, these results cannot be generalized to all patients or all oxygen-conserving devices. Further research is needed to determine the general performance of PDOCDs on larger populations of oxygen-dependent patients and patients with sleep-disordered breathing.

Characteristics of demand oxygen delivery systems: maximum output and setting recommendations.

BACKGROUND: Demand oxygen delivery systems (DODS) allot oxygen by interrupting the oxygen flow during exhalation, when it would mostly be wasted. Because DODS conserve oxygen by various methods, there are important performance differences between DODS. We studied certain performance factors that have not previously been carefully examined. METHODS: A bench model was constructed to simulate a nose, airway, and alveolar chamber. A breathing simulator generated 4 respiratory patterns, at frequencies of 15, 20, 25, and 30 breaths/min. Eighteen models of DODS were tested at 4 settings, each up to the maximum output, and compared to continuous-flow oxygen. The variable of interest was the fraction of inspired oxygen (F(I)O(2)) in the alveolar chamber, which was measured for each condition. RESULTS: The DODS differed from continuous-flow oxygen, delivering 0.5-2.1 times (mean = 1.13 times) the F(I)O(2) increase at similar settings. During maximum output the DODS showed a wide range of F(I)O(2), from 0.27 to 0.46. There was a direct relationship between volume output per pulse in the first 0.6 s of inhalation and the delivered F(I)O(2). CONCLUSIONS: DODS settings were not equivalent to continuous-flow oxygen in a bench model assessment; with equivalent settings the DODS tended to deliver greater F(I)O(2) than did continuous-flow oxygen. The maximum output capacity differed markedly among the DODS, and the user should know the device's capacity. A volume-referenced setting system for DODS should be adopted that would allow more predictable oxygen prescription and delivery via DODS.