Automatic detection of reverse-triggering related asynchronies during mechanical ventilation in ARDS patients using flow and pressure signals.

Asynchrony due to reverse-triggering (RT) may appear in ARDS patients. The objective of this study is to validate an algorithm developed to detect these alterations in patient-ventilator interaction. We developed an algorithm that uses flow and airway pressure signals to classify breaths as normal, RT with or without breath stacking (BS) and patient initiated double-triggering (DT). The diagnostic performance of the algorithm was validated using two datasets of breaths, that are classified as stated above. The first dataset classification was based on visual inspection of esophageal pressure (Pes) signal from 699 breaths recorded from 11 ARDS patients. The other classification was obtained by vote of a group of 7 experts (2 physicians and 5 respiratory therapists, who were trained in ICU), who evaluated 1881 breaths gathered from recordings from 99 subjects. Experts used airway pressure and flow signals for breaths classification. The RT with or without BS represented 19% and 37% of breaths in Pes dataset while their frequency in the expert's dataset were 3% and 12%, respectively. The DT was very infrequent in both datasets. Algorithm classification accuracy was 0.92 (95% CI 0.89-0.94, P < 0.001) and 0.96 (95% CI 0.95-0.97, P < 0.001), in comparison with Pes and experts' opinion. Kappa statistics were 0.86 and 0.84, respectively. The algorithm precision, sensitivity and specificity for individual asynchronies were excellent. The algorithm yields an excellent accuracy for detecting clinically relevant asynchronies related to RT.

[Argentine consensus of non-invasive ventilation]. / Consenso argentino de ventilación no invasiva.

Non-invasive ventilation (NIV) is nowadays increasingly used. The significant decrease in tracheal intubation related complications makes it particularly attractive in patients with moderately acute respiratory failure (ARF) who still have some degree of respiratory autonomy. It has also been used to support patients with chronic respiratory failure. However, final outcomes are variable according to the conditions which determined its application. This Consensus was performed in order to review the evidence supporting the use of positive pressure NIV. The patho-physiological background of NIV and the equipment required technology are described. Available evidence clearly suggests benefits of NIV in acute exacerbation of chronic obstructive pulmonary disease (COPD) and in cardiogenic pulmonary edema (Recommendation A). When considering ARF in the setting of acute respiratory distress syndrome results are uncertain, unless dealing with immunosupressed patients (Recommendation B). Positive results are also shown in weaning of mechanical ventilation (MV), particularly regarding acute exacerbation of COPD patients (Recommendation A). An improved quality of life in chronic respiratory failure and a longer survival in restrictive disorders has also been shown (Recommendation B) while its benefit in stable COPD patients is still controversial (Recommendation C). NIV should be performed according to pre-established standards. A revision of NIV related complications is performed and the cost-benefit comparison with invasive MV is also considered.

Monitoreo respiratorio y su rol en Terapia intensiva / Respiratory monitoring and its role in intensive therapy

El monitoreo respiratorio (MR) complementa al juicio clínico y puede estar asociado a la asistencia respiratoria mecánica (ARM) o no. Se reconocen tres períodos asociados al desarrollo del MR: entre 1964 y 1974 el MR lo constituía la medición de pH y gases en sangre arterial, y la medición de volumen minuto respiratorio era excepcional. Entre 1975 y 1985 seintrodujeron componentes electrónicos en los respiradores y se disponía de respiradores volumétricos con espirómetro incorporado, permitiendo desarrollar técnicas de mediciónde compliance y otros valores derivados. También se desarrolló la oxicapnometría, que se transformó en un auxiliar para el control de la respiración. El último período comenzó en 1985 y se caracteriza por la aparición de respiradores microprocesados, que suministrandiferentes modos ventilatorios y de monitores simples y fáciles de operar, capaces de determinar variables mecánicas antes reservadas a laboratorios de fisiopatología. Estosrespiradores de alta tecnología contienen monitores que informan en tiempo real sobre diversas variables durante la ARM, pero que al retirar el respirador dejan de informar. Sedebería aprovechar la disponibilidad de monitores aislados para continuar con el monitoreo, aún después del retiro del respirador, lo cual ha demostrado ser beneficioso.

Respiratory monitoring (RM) complements the clinical judgement and may be associated or not with mechanical ventilation (MV). Three periods in relation to the development of RM could be recognized: from 1964 to 1974 RM was done by pH and blood gases measurements, the measurement of minute ventilation was not routinely performed. Between 1975 and 1985 electronic components were introduced in the ventilators and volumetric ventilators with incorporated spirometer became available permitting the measuring of compliance and other derived measurements. After becoming available, oxicapnometry was considereda useful tool for monitoring respiration. The last period began in 1985 and was characterized by the arising of microprocessed ventilators able to provide different ventilatory modalities,equipped with simple and easy to operate monitors that could calculate mechanical variables that in the past were limited to respiratory physiology laboratories. These high tech ventilators are equipped with monitors informing at real time about physiological variables,however, after the weaning this information stops to be available. The availability of those stand alone monitors should be taken into account to continue the monitoring, even after the weaning; as this has been demonstrated to be beneficial.