Automatic detection of patient-ventilator asynchrony by spectral analysis of airway flow.

INTRODUCTION: Adequate ventilatory support of critically ill patients depends on prompt recognition of ventilator asynchrony, as asynchrony is associated with worse outcomes.We compared an automatic method of patient-ventilator asynchrony monitoring, based on airway flow frequency analysis, to the asynchrony index (AI) determined visually from airway tracings. METHODS: This was a prospective, sequential observational study of 110 mechanically ventilated adults. All eligible ventilated patients were enrolled. No clinical interventions were performed. Airway flow and pressure signals were sampled digitally for two hours. The frequency spectrum of the airway flow signal, processed to include only its expiratory phase, was calculated with the Cooley-Tukey Fast Fourier Transform method at 2.5 minute intervals. The amplitude ratio of the first harmonic peak (H1) to that of zero frequency (DC), or H1/DC, was taken as a measure of spectral organization. AI values were obtained at 30-minute intervals and compared to corresponding measures of H1/DC. RESULTS: The frequency spectrum of synchronized patients was characterized by sharply defined peaks spaced at multiples of mean respiratory rate. The spectrum of asynchronous patients was less organized, showing lower and wider H1 peaks and disappearance of higher frequency harmonics. H1/DC was inversely related to AI (n = 110; r2 = 0.57; P < 0.0001). Asynchrony, defined by AI > 10%, was associated H1/DC < 43% with 83% sensitivity and specificity. CONCLUSIONS: Spectral analysis of airway flow provides an automatic, non-invasive assessment of ventilator asynchrony at fixed short intervals. This method can be adapted to ventilator systems as a clinical monitor of asynchrony.

The effect of race on long term mortality in mechanically ventilated patients.

OBJECTIVE: Determine the impact of race on one-year mortality following mechanical ventilation. BACKGROUND: There is a lack of prospective studies on the effect of race on survival following mechanical ventilation. METHODS: Observational study of adult patients on ventilatory support for <24 h prior to enrollment. Socioeconomic factors, laboratory and clinical data were recorded. Primary outcome was one-year mortality. RESULTS: We enrolled 178 patients; 100 African American (AA), 78 other races (OTH). One-year mortality for AA was 49% and 33% for OTH (p = 0.035). After correcting for covariates, race was not significantly associated with mortality (p = 0.42). AA patients had higher mean arterial blood pressure, serum creatinine, heart rate, and peak (p < 0.01) and mean (p = 0.05) airway pressures. CONCLUSIONS: AA patients who underwent mechanical ventilation had greater one-year mortality, although race per se was not a significant factor. It remains to be determined if strict blood pressure control and lower airway pressures may improve survival in this racial group.

[Isolation of environmental mycobacteria from soils of Córdoba city Argentina]. / Aislamiento de micobacterias medioambientales en suelos de la ciudad de Córdoba.

The interest for the research on enviromental mycobacteria has risen over the last decades, in part, due to a significant incidence rate rise. Reports from all over the world address the soil as the major source for human contamination. In Argentina two documents report the prevalence of atypical mycobacteriosis at Córdoba (1997), and the isolation of enviromental mycobacteria from soils of the Province of La Pampa (1999) respectively. The aim of our study was to confirm the presence of enviromental mycobacteria in soil of the city of Córdoba. The map of the city was divided in 9 regions according to avenues and major streets distribution. A total of 120 soil samples were recollected with spatula from a 10 x 10 cm square up to 1 cm deep. Samples were kept at 4 degrees C no more than 7 days. Soil samples were homogenized with destilled water in a 1:1 proportion, and decontaminated according to Petroff's method. The cultures were made in Lowestein-Jehnsen media and incubated at 37 degrees C controlling development every 7 days for 2 months. An acid-fast-bacilli smear was made from colonies obtained. Twenty three cultures (19%) were discarded due to contamination. Twenty cultures (17%) developed acid fast bacilli (AFB). Colonies obtained were sent to the Mycobacteria Service of the Instituto Nacional de Enfermedades Infecciosas Dr. Carlos G. Malbrán, in the city of Buenos Aires, for identification. A single isolation was identified as Mycobacterium triviale. A positive correlation was observed between the frequency of positive AFB isolation and the number of samples taken from park areas. The presence of enviromental mycobacteria in soils of Córdoba was confirmed. Results suggest higher odds of isolation in parklands and soils where animals live. Extensive works are needed to asset the features that allow and contribute the proliferation of mycobacteria in soils.

Decreased respiratory rate variability during mechanical ventilation is associated with increased mortality.

OBJECTIVE: Patients on ventilatory support often experience significant changes in respiratory rate. Our aim was to determine the possible association between respiratory rate variability (RRV) and outcomes in these patients. DESIGN: A longitudinal, prospective, observational study of patients mechanically ventilated for at least 12 h performed in a medical-surgical intensive care unit. Patients were enrolled within 24 h of the initiation of ventilatory support. We measured airway signals continuously for the duration of ventilatory support and calculated expiratory flow frequency spectra at 2.5-min intervals. We assessed RRV using the amplitude ratio of the flow spectrum's first harmonic to the zero frequency component. Measures of the amplitude ratio were averaged over the total monitored time. Patients with time-averaged amplitude ratios <40 % were classified as high RRV and those ≥40 % as low RRV. All-cause mortality rates were assessed at 28 and 180 days from enrollment with a Cox proportional hazards model adjusted for disease acuity by the simplified acute physiology score II. RESULTS: We enrolled 178 patients, of whom 47 had high RRV and 131 low RRV. Both groups had similar disease acuity upon enrollment. The 28- and 180-day mortality rates were greater for low RRV patients with hazard ratios of 4.81 (95 % CI 1.85-12.65, p = 0.001) and 2.26 (95 % CI 1.21-4.20, p = 0.01), respectively. Independent predictors of 28-day mortality were low RRV, i.v. vasopressin, and SAPS II. CONCLUSIONS: Decreased RRV during ventilatory support is associated with increased mortality. The mechanisms responsible for this finding remain to be determined.

Pulmonary nontuberculous mycobacterial infections: antibiotic treatment and associated costs.

Recent studies suggest an increasing prevalence of pulmonary nontuberculous mycobacteria (NTM) disease. In the absence of prevalence and cost data, the public health burden of pulmonary NTM disease is difficult to assess. The goal of this study was to assess costs associated with NTM disease treatment and to identify risk factors associated with increased costs. Records from subjects with pulmonary NTM disease enrolled in a natural history protocol were abstracted for presenting symptoms, comorbidities, microbiology, and treatment histories. Antibiotic frequency, duration, adverse reaction, and costs were noted, the total antibiotic burden and cost were calculated, and risk factors associated with high costs were analyzed. From Jan 2004 to Dec 2005, 33 subjects were enrolled; 27 met disease criteria and had sufficient data to assess antibiotic use. Mycobacterium avium complex was present in 89% and Mycobacterium abscessus was present in 21% of subjects. Subjects received a median of 5 (1-10) antibiotics. Adverse effects were common seen in up to 50% with common antibiotics and up to 100% with uncommonly used antibiotics. Median burden of treatment was 2638 (84-7689) drug-days and the median total cost per patient was $19,876 ($398-70,917). Subjects with high treatment costs had an adjusted 9.5 fold (95% CI 1.5-97.2) likelihood of having M. abscessus and a 4.2 fold (95% CI 0.6-59.3) increased likelihood of having more extensive disease. Pulmonary NTM represent an underappreciated disease burden in the US population, with an associated treatment cost comparable to that for other chronic diseases of infectious origin such as HIV/AIDS.

Aislamiento de micobacterias medioambientales en suelos de la ciudad de Córdoba / Isolation of environmental mycobacteria from soils of Córdoba city Argentina

Durante los últimos años ha resurgido el interés por el estudio de las micobacterias medioambientales debido al aumento en incidencia de las micobacteriosis atípicas. Estudios realizados en todo el mundo señalan al suelo como una fuente importante de contaminación humana. En el país existen trabajos que documentan la prevalencia de las micobacteriosis atípicas en Córdoba (1997). y su aislamiento en suelos de La Pampa (1999). El objetivo fue demostrar la existencia de micobacterias mdioambientales en suelos de la ciudade de Córdoba. Se dividió la ciudad en nueve regiones. Se recogieron un total de 120 muestrars en lugares de fácil acceso a suelos orgánicos; cada una se obtuvo en un área cuadrada de 10 cm de lado, hasta 1 cm de profundidad. Se conservaron en heladera hasta 7 días. Fueron homogeneizadas con agua tridestilada en relación 1:1, y decontaminadas según el método de Petroff. Se procedió a la siembra en medio de Lowestein-Jensen, y se incubó en stufa a 37ºC con controles cada 7 días durante 2 meses. Se realizó tinción de Ziehl-Neelsen a los cultivos positivos. Veintitrés muestras (19) fueron descartadas por contaminación. En 20 muestras (17) se observaron bacilos ácido-alcohol resistentes. Las colonias obtenidas fueron enviadas para su identificación al Servicio de Micobacterias del Instituto Nacional de Enfermedades Infecciosas Dr. Carlos G. Malbrán, a cargo de la Lic. Lucía Barrera. Hast el momento uno de los aislameientos fue identificado como Mycobacterium triviale. Con respecto a la distribución redional de los aislamientos, se observó correlación entre el porcentaje de muestras positivas y el número de muestras obtenidas en espacios parquizados. Se demostró la presencia de micobacterias medioambientales en suelos de micobacterias medioambientales en suelos de la ciudad de Córdoba. Los resultados sugieren mayores probabilidades de aislamiento en parquizaciones y suelos habitados por animales. Nuevos trabajos permitirán aclarar características del suelo que favorecen la proliferación de micobacterias, el microorganismo aislado más frecuente, y tal vez brindar armas para la prevención de la enfermedad