Adaptive restraint design for a diverse population through machine learning.

Objective: Using population-based simulations and machine-learning algorithms to develop an adaptive restraint system that accounts for occupant anthropometry variations to further enhance safety balance throughout the whole population. Methods: Two thousand MADYMO full frontal impact crash simulations at 35 mph using two validated vehicle/restraint models representing a sedan and an SUV along with a parametric occupant model were conducted based on the maximal projection design of experiments, which considers varying occupant covariates (sex, stature, and body mass index) and vehicle restraint design variables (three for airbag, three for safety belt, and one for knee bolster). A Gaussian-process-based surrogate model was trained to rapidly predict occupant injury risks and the associated uncertainties. An optimization framework was formulated to seek the optimal adaptive restraint design policy that minimizes the population injury risk across a wide range of occupant sizes and shapes while maintaining a low difference in injury risks among different occupant subgroups. The effectiveness of the proposed method was tested by comparing the population-wise injury risks under the adaptive design policy and the traditional state-of-the-art design. Results: Compared to the traditional state-of-the-art design for midsize males, the optimal design policy shows the potential to further reduce the joint injury risk (combining head, chest, and lower extremity injury risks) among the whole population in the sedan and SUV models. Specifically, the two subgroups of vulnerable occupants including tall obese males and short obese females had higher reductions in injury risks. Conclusions: This study lays out a method to adaptively adjust vehicle restraint systems to improve safety balance. This is the first study where population-based crash simulations and machine-learning methods are used to optimize adaptive restraint designs for a diverse population. Nevertheless, this study shows the high injury risks associated with obese and female occupants, which can be mitigated via restraint adaptability.

Effects of an integrated safety system for swivel seat arrangements in frontal crash.

Objective: Autonomous vehicles (Avs) have paved the way for the arrangement of swivel seats in vehicles, which could pose a challenge to traditional safety systems. The integration of automated emergency braking (AEB) and pre-pretension (PPT) seatbelts improves protection for a vehicle's occupant. The objective of this study is to explore the control strategies of an integrated safety system for swiveled seating orientations. Methods: Occupant restraints were examined in various seating configurations using a single-seat model with a seat-mounted seatbelt. Seat orientation was set at different angles, from -45° to 45° with 15° increments. A pretension was used on the shoulder belt to represent an active belt force cooperating with AEB. A generic full frontal vehicle pulse of 20 mph was applied to the sled. The occupant's kinematics response under various integrated safety system control strategies was analyzed by extracting a head pre-crash kinematics envelope. The injury values were calculated for various seating directions with or without an integrated safety system at the collision speed of 20 mph. Results: In a lateral movement, the excursions of the dummy head were 100 mm and 70 mm in the global coordinate system for negative and positive seat orientations, respectively. In the axial movement, the head traveled 150 mm and 180 mm in the global coordinate system for positive and negative seating directions, respectively. The 3-point seatbelt did not restrain the occupant symmetrically. The occupant experienced greater y-axis excursion and smaller x-axis excursion in the negative seat position. Various integrated safety system control strategies led to significant differences in head movement in the y direction. The integrated safety system reduced the occupant's potential injury risks in different seating positions. When the AEB and PPT were activated, the absolute HIC15, brain injury criteria (BrIC), neck injury (Nij), and chest deflection were reduced in most seating directions. However, the pre-crash increased the injury risks at some seating positions. Conclusion: The pre-pretension seatbelt could reduce the occupant's forward movement in the rotating seat positions in a pre-crash period. The occupant's pre-crash motion envelope was generated, which could be beneficial to future restraint systems and vehicle interior design. The integrated safety system could reduce injuries in different seating orientations.

An in silico analysis of oxygen uptake of a mild COPD patient during rest and exercise using a portable oxygen concentrator.

Oxygen treatment based on intermittent-flow devices with pulse delivery modes available from portable oxygen concentrators (POCs) depends on the characteristics of the delivered pulse such as volume, pulse width (the time of the pulse to be delivered), and pulse delay (the time for the pulse to be initiated from the start of inhalation) as well as a patient's breathing characteristics, disease state, and respiratory morphology. This article presents a physiological-based analysis of the performance, in terms of blood oxygenation, of a commercial POC at different settings using an in silico model of a COPD patient at rest and during exercise. The analysis encompasses experimental measurements of pulse volume, width, and time delay of the POC at three different settings and two breathing rates related to rest and exercise. These experimental data of device performance are inputs to a physiological-based model of oxygen uptake that takes into account the real dynamic nature of gas exchange to illustrate how device- and patient-specific factors can affect patient oxygenation. This type of physiological analysis that considers the true effectiveness of oxygen transfer to the blood, as opposed to delivery to the nose (or mouth), can be instructive in applying therapies and designing new devices.

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.

Effect of allergen immunotherapy practice parameters on cat extract prescribing patterns, 1993-2009.

BACKGROUND: Cat extract allergen immunotherapy (AIT) is an effective treatment for cat allergy. The prescribed dose for cat AIT varies among prescribers, despite published data supporting an effective dose range. The original practice parameter published in December 1996 did not recommend a dose of cat allergen, but updates in January 2003 and September 2007 recommend cat extract dose ranges of 2,000 to 3,000 BAU and 1,000 to 4,000 BAU, respectively. OBJECTIVE: To describe the prescribing patterns for cat AIT among practicing allergists in a large health care system and the effect of practice parameters on these patterns. METHODS: A total of 27,788 prescriptions were analyzed to determine the date and amount of maintenance dose cat allergen prescribed. The data were subdivided into periods before and after the 3 published AIT practice parameters. RESULTS: From January 2003 to September 2007, 1,810 prescriptions (18.0%) were written in the recommended range. From September 2007 to May 2009, 3,143 prescriptions (82.6%) were written in the recommended range. Cat AIT maintenance doses were 1,000 to 4,000 BAU 22.1% of the time before January 2003, 61.8% from January 2003 to September 2007, and 82.6% from September 2007 to May 2009. CONCLUSIONS: In this large systemic evaluation of cat AIT prescribing patterns, maintenance dose recommendations in the AIT practice parameters were associated with changes in the prescribing patterns for cat AIT. Most prescriptions for cat AIT were inconsistent with recommended doses in the AIT practice parameters between 2003 and 2007. Dosing within recommended ranges improved after 2007, in part due to a widening of the recommended dose range.

Imported fire ant immunotherapy prescribing patterns in a large health care system during a 17-year period.

BACKGROUND: No large evaluation has been performed of the maintenance vial concentration commonly used by physicians when prescribing imported fire ant (IFA) immunotherapy since the publication of the first Stinging Insect Hypersensitivity Practice Parameter 10 years ago. OBJECTIVE: To describe the prescribing patterns for IFA immunotherapy among practicing allergists in a large health care setting and the impact of published Practice Parameter recommendations. METHODS: Data from the US Army Centralized Allergen Extract Laboratory were analyzed to determine IFA immunotherapy prescribing patterns from 1990 to May 2007. This extract laboratory provides prescriptions for more than 320 US Department of Defense, US Department of Veterans Affairs, and US Public Health Service clinics. RESULTS: A total of 1,091 patients were given 1,437 new or revised prescriptions for IFA immunotherapy. Monotherapy for Solenopsis invicta and Solenopsis richteri was prescribed in 169 (11.8%) and 3 (0.1%) instances, respectively, with the remainder of patients given both IFA antigens. The most commonly prescribed maintenance vial dose was 0.5 mL of a 1:200 (wt/vol) dilution, accounting for 36.3% of prescriptions. A total of 17.3% of prescriptions had a maintenance vial dose of 0.5 mL of a 1:100 (wt/vol) dilution, 4.6% had a dilution of 1:10 (wt/vol), and 50.6% had a dilution between 1:10 and 1:100 (wt/vol). The mean starting dose was 4.4 10-fold dilutions below the maintenance dose (5.4 vials per treatment set). CONCLUSIONS: The most commonly prescribed maintenance dose was 0.5 mL of a 1:200 (wt/vol) dilution, although most prescriptions used a maintenance dose consistent with recommended dosing in the Stinging Insect Practice Parameters. Both IFA antigens were used by most physicians. Further study evaluating the effective dose range for IFA immunotherapy is needed.

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.