Background:Various estimates of the incidence and mortality rate of the acute (adult) respiratory distress syndrome (ARDS) have been published. The studies that led to those estimates were based on relatively small patient populations and employed variable diagnostic identifiers of ARDS. The purpose of this study was to estimate the incidence of ARDS and its mortality rate from a large database to which refined diagnostic criteria were applied. We conducted a retrospective review of all hospital discharges over a 4-year period, using screening criteria designed to select patients with ARDS. Discharges from all acute care hospitals in the state of Maryland were reviewed using a computer database from the Health Services Cost Review Commission (HSCRC). Patients ≥ 12 years of age were included. Screening criteria consisted of ICD-9 codes 518.5 and 518.82 cross-referenced with procedural codes for ventilatory support (96.70, 96.71 and 96.72). Data were normalized to the number of cases per 100,000 people.Results:During the 4-year study period there were 2,501,147 hospitalizations. Applying the ICD-9 ARDS criteria yielded lower and upper limits of 159-205, 439-568, 531-694 and 529-720 cases of ARDS for 1992, 1993, 1994 and 1995, respectively. Normalizing for a population of 5 million yields yearly lower and upper limit rates of 3.2-4.2, 8.8-11.4, 10.6-13.8 and 10.5-14.2 cases of ARDS per 100,000 people. Mortality upper and lower limit rates based upon the same duration, admissions and population were 38-49%, 39-52%, 36-47%, and 36-49%, respectively.Conclusions:The incidence of ARDS in Maryland is in the range of 10-14 cases per 100,000 people. The ARDS mortality rate is 36% to 52%, similar to that calculated in previous studies.

Video-based monitoring of HR, RR, and oxygen saturation may be performed with reasonable accuracy during acute hypoxic conditions in an anesthetized porcine hypoxia model using standard visible light camera equipment. However, the study was conducted during relatively low motion. A better understanding of the effect of motion and the effect of ambient light on the video photoplethysmogram may help refine this monitoring technology for use in the clinical environment.

The robust monitoring of heart rate from the video-photoplethysmogram (video-PPG) during challenging conditions requires new analysis techniques. The work reported here extends current research in this area by applying a motion tolerant algorithm to extract high quality video-PPGs from a cohort of subjects undergoing marked heart rate changes during a hypoxic challenge, and exhibiting a full range of skin pigmentation types. High uptimes in reported video-based heart rate (HRvid) were targeted, while retaining high accuracy in the results. Ten healthy volunteers were studied during a double desaturation hypoxic challenge. Video-PPGs were generated from the acquired video image stream and processed to generate heart rate. HRvid was compared to the pulse rate posted by a reference pulse oximeter device (HRp). Agreement between video-based heart rate and that provided by the pulse oximeter was as follows: Bias = − 0.21 bpm, RMSD = 2.15 bpm, least squares fit gradient = 1.00 (Pearson R = 0.99, p < 0.0001), with a 98.78% reporting uptime. The difference between the HRvid and HRp exceeded 5 and 10 bpm, for 3.59 and 0.35% of the reporting time respectively, and at no point did these differences exceed 25 bpm. Excellent agreement was found between the HRvid and HRp in a study covering the whole range of skin pigmentation types (Fitzpatrick scales I–VI), using standard room lighting and with moderate subject motion. Although promising, further work should include a larger cohort with multiple subjects per Fitzpatrick class combined with a more rigorous motion and lighting protocol.

The management of impaired respiratory gas exchange in patients with nonuniform posttraumatic and septic adult respiratory distress syndrome (ARDS) contains its own therapeutic paradox, since the need for volume-controlled ventilation and PEEP in the lung with the most reduced compliance increases pulmonary barotrauma to the better lung. A computer-based system has been developed by which respiratory pressure-flow-volume relations and gas exchange characteristics can be obtained and respiratory dynamic and static compliance curves computed and displayed for each lung, as a means of evaluating the effectiveness of ventilation therapy in ARDS. Using these techniques, eight patients with asymmetrical posttraumatic or septic ARDS, or both, have been managed using simultaneous independent lung ventilation (SILV). The computer assessment technique allows quantification of the nonuniform ARDS pattern between the two lungs. This enabled SILV to be utilized using two synchronized servo-ventilators at different pressure-flow-volumes, inspiratory/expiratory ratios, and PEEP settings to optimize the ventilatory volumes and gas exchange of each lung, without inducing excess barotrauma in the better lung. In the patients with nonuniform ARDS, conventional ventilation was not effective in reducing shunt (QS/QT) or in permitting a lower FIO2 to be used for maintenance of an acceptable PaO2. SILV reduced per cent v-a shunt and permitted a higher PaO2 at lower FIO2. Also, there was x-ray evidence of ARDS improvement in the poorer lung. While the ultimate outcome was largely dependent on the patient's injury and the adequacy of the septic host defense, by utilizing the SILV technique to match the quantitative aspects of respiratory dysfunction in each lung at specific times in the clinical course, it was possible to optimize gas exchange, to reduce barotrauma, and often to reverse apparently fixed ARDS changes. In some instances, this type of physiologically directed ventilatory therapy appeared to contribute to a successful recovery.