Takkin Lo

A dual closed-loop control system for mechanical ventilation.

Objective. Closed-loop mechanical ventilation has the potential to provide more effective ventilatory support to patients with less complexity than conventional ventilation. The purpose of this study was to investigate the effectiveness of an automatic technique for mechanical ventilation. Methods. Two closed-loop control systems for mechanical ventilation are combined in this study. In one of the control systems several physiological data are used to automatically adjust the frequency and tidal volume of breaths of a patient. This method, which is patented under US Patent number 4986268, uses the criterion of minimal respiratory work rate to provide the patient with a natural pattern of breathing. The inputs to the system include data representing CO2 and O2 levels of the patient as well as respiratory compliance and airway resistance. The I:E ratio is adjusted on the basis of the respiratory time constant to allow for effective emptying of the lungs in expiration and to avoid intrinsic positive end expiratory pressure (PEEP). This system is combined with another closed-loop control system for automatic adjustment of the inspired fraction of oxygen of the patient. This controller uses the feedback of arterial oxygen saturation of the patient and combines a rapid stepwise control procedure with a proportional-integral-derivative (PID) control algorithm to automatically adjust the oxygen concentration in the patients inspired gas. The dual closed-loop control system has been examined by using mechanical lung studies, computer simulations and animal experiments. Results. In the mechanical lung studies, the ventilation controller adjusted the breathing frequency and tidal volume in a clinically appropriate manner in response to changes in respiratory mechanics. The results of computer simulations and animal studies under induced disturbances showed that blood gases were returned to the normal physiologic range in less than 25 s by the control system. In the animal experiments under steady-state conditions, the maximum standard deviations of arterial oxygen saturation and the end-tidal partial pressure of CO2 were ± 1.76% and ± 1.78 mmHg, respectively. Conclusion. The controller maintained the arterial blood gases within normal limits under steady-state conditions and the transient response of the system was robust under various disturbances. The results of the study have showed that the proposed dual closed-loop technique has effectively controlled mechanical ventilation under different test conditions.

Closed-Loop Control of the Inspired Fraction of Oxygen in Mechanical Ventilation

Objective.Supplemental oxygen treatment of patients on mechanical ventilation is crucial in maintaining the patients’ oxygen levels in the normal range. The purpose of this study was to evaluate the effectiveness of a closed-loop controller for automatic adjustment of the fraction of inspired oxygen, FIO2. More specifically, the aim of the study was to assess the robustness of the controller in correcting hypoxemia as well as its effectiveness in prevention of hyperoxemia and oxygen toxicity. Methods.The microprocessor-based feedback control system combines a rapid control algorithm with a proportional-integral-derivative (PID) control procedure to automatically adjust FIO2. The system is designed to prevent hypoxemia by applying a stepwise control procedure in response to rapid declines in arterial oxygen saturation while fine-tuning FIO2 and avoiding hyperoxemia by resuming to the PID control procedure when appropriate. The system includes a sophisticated safeguard unit which is designed to communicate any oxygenation problems or measurement artifacts to the medical personnel while keeping FIO2 at a safe and sufficiently high level. The control system has been tested by using computer simulations as well as animal studies. Results.In response to different disturbances, the arterial oxygen saturation returned to the normal safe range within less than 20 seconds, thereby avoiding any untoward effects of hypoxemia. Under steady state conditions, the variations in arterial oxygen saturation were kept within ± 3% of the mean value. The controller corrected hypoxemia within seconds while preventing hyperoxemia, rejecting artifacts, and minimizing exposure to high concentrations of oxygen. Conclusion.The results of the study attest to the reliability of the proposed closed-loop control scheme for automatic adjustment of FIO2. Further evaluation of the controller will require testing the effectiveness of the system on different patient groups.

The combined effect of a three-channel electrode delivery system with local heat on the healing of chronic wounds.

BACKGROUND Historically, electrical stimulation (ES) has been used as a treatment for wound care. However, some studies show wounds healing with ES, whereas others do not. Part of the difficulty can be resolved by using heat to help dilate blood vessels, but an inherent problem with ES is uneven currents across the wound due to the use of only two electrodes. Therefore, we designed and tested a multi-electrode ES device in combination with local warming of the wound in non-healing chronic ulcers. STUDY DESIGN Eighteen subjects (mean +/- SD age, 35.7 +/- 21.3 years) with chronic ulcers (no healing for 26.1 +/- 24.6 months) received ES treatment three times a week for 4 weeks. A heat lamp was used before and during ES to keep the wound and area surrounding the wound warm (37 degrees C). ES was applied for 30 min with biphasic sine wave stimulation at a frequency of 30 Hz, pulse width of 250 micros, and current of about 20 mA. Skin blood flow (BF) in and around the wound was measured with a laser Doppler imager. Wound size was measured prior to each treatment. RESULTS Over the 1-month period, the mean wound area significantly decreased by 43.4 +/- 44.5% (P < 0.05), and wound volume decreased by 57.0 +/- 27.9% (P < 0.05). Skin BF significantly increased after application of ES and local heat (P < 0.05). The skin BF response decreased as time progressed and the wound healed. CONCLUSIONS Thus, in this pilot study, application of a three-channel ES system in combination with local heat is effective in the healing of non-healing chronic wounds. Future studies should examine a larger population with variables such as treatment duration, number of days, or length of treatment to optimize the effect of ES on healing of non-healing chronic wounds.

Does hyperbaric oxygen therapy have the potential to improve salivary gland function in irradiated head and neck cancer patients

Following radiotherapy, many patients with osteoradionecrosis suffer from xerostomia, thereby decreasing their quality of life. Patients can develop problems with speech, eating, increased dental caries, dysphagia, fractured dentition, chronic refractory osteomyelitis and osteoradionecrosis. Symptoms associated with salivary gland dysfunction can be severe enough that patients terminate the course of their radiotherapy prematurely due to the decrease in their quality of life. Currently, the only treatments available to patients are palliative. A definitive treatment has yet to be discovered. Head and neck cancers, which comprise 5% of overall cancer treatments, rank 8th most expensive to treat in the United States today. Hyperbaric oxygen is being considered for the therapy of radiated salivary glands because it has been shown to stimulate capillary angiogenesis and fibroplasia in radiation treated tissues. It has been hypothesized that salivary acinar cells undergo apoptosis following radiation therapy. The purpose of this paper is to discuss the mechanisms of salivary gland injury and evaluate whether hyperbaric oxygen therapy improves salivary gland function in patients who develop xerostomia and osteoradionecrosis following head and neck radiation.

Emotional Impact of Cardiopulmonary Resuscitation Training on High School Students

Background The American Heart Association (AHA) has implemented several programs to educate the public about cardiopulmonary resuscitation (CPR). A common issue in bystander CPR is the fear of hurting the victim. As a result, the victim may not receive CPR in time. The purpose of this study was to measure the emotional impact of CPR training on high school students using two approved AHA courses. Methods A total of 60 students participated in this study. These students had a mean age of 15.4 ± 1.2 years old and were selected from a high school in Southern California. Subjects were divided into two groups, Basic Life Support (BLS) (n1 = 31) and Hands-Only™ CPR (n2 = 29). Emotional impacts were assessed by having each subject answer a questionnaire based on given scenarios before and after their training session. Results There was a significant difference in both groups when comparing positive-emotion scores before and after the training (BLS: 30.3 ± 6.0 vs. 34.5 ± 6.7, p < 0.001; Hands-Only 27.9 ± 5.0 vs. 32.1 ± 6.5, p < 0.001). In addition, both groups showed significant reductions in negative-emotion scores (BLS: 29.2 ± 6.7 vs. 23.7 ± 6.5, p < 0.001 and Hands-Only: 26.8 ± 6.1vs. 24.8 ± 7.7, p = 0.05). Conclusion Our results indicate that the AHA programs have positive effects on students’ emotional response. We recommend that future studies include an in-depth study design that probes the complexity of students’ emotions after completing an AHA session.