Ventilation-perfusion heterogeneity measured by the multiple inert gas elimination technique is minimally affected by intermittent breathing of 100% O2.

Proton magnetic resonance (MR) imaging to quantify regional ventilation-perfusion ( V˙A/Q˙ ) ratios combines specific ventilation imaging (SVI) and separate proton density and perfusion measures into a composite map. Specific ventilation imaging exploits the paramagnetic properties of O2 , which alters the local MR signal intensity, in an FI O2 -dependent manner. Specific ventilation imaging data are acquired during five wash-in/wash-out cycles of breathing 21% O2 alternating with 100% O2 over ~20 min. This technique assumes that alternating FI O2 does not affect V˙A/Q˙ heterogeneity, but this is unproven. We tested the hypothesis that alternating FI O2 exposure increases V˙A/Q˙ mismatch in nine patients with abnormal pulmonary gas exchange and increased V˙A/Q˙ mismatch using the multiple inert gas elimination technique (MIGET).The following data were acquired (a) breathing air (baseline), (b) breathing alternating air/100% O2 during an emulated-SVI protocol (eSVI), and (c) 20 min after ambient air breathing (recovery). MIGET heterogeneity indices of shunt, deadspace, ventilation versus V˙A/Q˙ ratio, LogSD V˙ , and perfusion versus V˙A/Q˙ ratio, LogSD Q˙ were calculated. LogSD V˙ was not different between eSVI and baseline (1.04 ± 0.39 baseline, 1.05 ± 0.38 eSVI, p = .84); but was reduced compared to baseline during recovery (0.97 ± 0.39, p = .04). There was no significant difference in LogSD Q˙ across conditions (0.81 ± 0.30 baseline, 0.79 ± 0.15 eSVI, 0.79 ± 0.20 recovery; p = .54); Deadspace was not significantly different (p = .54) but shunt showed a borderline increase during eSVI (1.0% ± 1.0 baseline, 2.6% ± 2.9 eSVI; p = .052) likely from altered hypoxic pulmonary vasoconstriction and/or absorption atelectasis. Intermittent breathing of 100% O2 does not substantially alter V˙A/Q˙ matching and if SVI measurements are made after perfusion measurements, any potential effects will be minimized.

Intra- and Inter-Physician Agreement in Therapeutic Decision for Sleep Apnea Syndrome / Concordancia intra e inter-médico en la decisión terapéutica para el síndrome de apnea del sueño

Background: Large variation in diagnostic procedures and treatment recommendations may hinder the management of obstructive sleep apnea (OSA) and also compromise correct interpretation of the results of multicenter clinical trials, especially in subjects with non-severe OSA. The aim of this study was to analyze the therapeutic decision-making between different sleep physicians in patients with AHÍ < 40 events/h. Methods: Six experienced senior sleep specialists from different sleep centers of Spain were asked to make a therapeutic decision (CPAP treatment) based on anonymized recordings of patients with suspected OSA that has previously performed a sleep study. The clinical data was shown in an online database and included anthropometric features, clinical questionnaires, comorbidities, physical examination and sleep study results. Intra- and inter-observer decision-making were analyzed by the Fleiss’ Kappa statistics (Kappa). Results: A total of 720 medical decisions were taken to analyze the agreement between sleep professionals. Overall intra-observer evaluation reliability was almost perfect (Kappa = 0.83, 95% CI, 0.75-0.90, p < 0.001). However, overall inter-observer concordance decreased to moderate agreement (Kappa = 0.46, 95% CI, 0.42-0.51, p < 0.001). Nevertheless, it was especially low when considering AHÍ < 15 events/h. Conclusions: This study demonstrates a good intra-observer concordance in the therapeutic decision-making of different sleep physicians treating patients with low/moderate OSA. However, when analyzing inter-observer agreement the results were considerably worse. These findings underline the importance of developing improved consensus management protocols

Introducción: La gran variedad de procedimientos diagnósticos y recomendaciones de tratamiento puede dificultar el manejo del síndrome de apnea obstructiva del sueño (SAHS), y del mismo modo comprometer la correcta interpretación de los resultados de ensayos clínicos multicéntricos, especialmente en pacientes con SAHS no grave. El objetivo de este estudio fue analizar la decisión terapéutica de distintos médicos expertos en sueño en pacientes con el índice de apnea hipopnea < 40 eventos/h. Métodos: Se pidió a seis especialistas con amplia experiencia en sueño de diferentes centros de España que tomaran una decisión terapéutica (terapia de presión positiva continua en las vías respiratorias o CPAP) basada en datos anónimos de los pacientes con sospecha de SAHS en los que previamente se había llevado a cabo un estudio del sueño. Los datos clínicos procedían de una base de datos online e incluían características antropométricas, cuestionarios clínicos, comorbilidades, examen físico y resultados del estudio del sueño. La concordancia intra- e interobservador de la toma de decisiones se analizó mediante el estadístico Fleiss' Kappa (Kappa). Resultados: Se analizaron un total de 720 decisiones médicas para evaluar el consenso entre profesionales del sueño. De manera global, la fiabilidad de la evaluación intraobservador fue casi perfecta (Kappa = 0,83; 95% CI; 0,75 a 0,90, p < 0,001). Sin embargo, la concordancia global interobservador disminuyó hasta alcanzar un grado moderado de consenso (Kappa = 0,46; 95% CI; 0,42 a 0,51, p < 0,001), que fue especialmente bajo cuando se tuvo en cuenta un índice de apnea hipopnea < 15 eventos/h. Conclusiones: Este estudio demuestra una buena concordancia intraobservador en la toma de decisiones terapéuticas de distintos médicos expertos en sueño que tratan a pacientes con SAHS leve o moderado. Sin embargo, los resultados relativos al acuerdo interobservador fueron notablemente peores. Estos hallazgos señalan la importancia de desarrollar mejores protocolos consensuados de manejo

Spiroergometric measurements under increased inspiratory oxygen concentration (FIO2)-Putting the Haldane transformation to the test.

Spiroergometric measurements of persons who require oxygen insufflation due to illness can be performed under conditions of increased inspiratory oxygen concentration (FIO2). This increase in FIO2, however, often leads to errors in the calculation of oxygen consumption ([Formula: see text]). These inconsistencies are due to the application of the Haldane Transformation (HT), an otherwise indispensable correction factor in the calculation of [Formula: see text] that becomes inaccurate at higher FIO2 concentrations. A possible solution to this problem could be the use of the 'Eschenbacher transformation' (ET) as an alternative correction factor. This study examines the concentration of FIO2 at which the HT and the ET are valid, providing plausible data of oxygen consumption corresponding to the wattage achieved during cycle ergometry. Ten healthy volunteers underwent spiroergometric testing under standard conditions (FIO2 = 20.9%), as well as at FIO2 = 40% and 80%. When compared with the predicted values of [Formula: see text], as calculated according to Wasserman et al. (2012), the data obtained show that both the HT and ET are valid under normal conditions and at an increased FIO2 of 40%. At FIO2 concentrations of 80%, however, the [Formula: see text] values provided by the HT begin to lose plausibility, whereas the ET continues to provide credible results. We conclude that the use of the ET in place of the HT in spiroergometric measurements with increased FIO2 allows a reliable evaluation of stress tests in patients requiring high doses of supplemental oxygen.

Tolerance to a haemorrhagic challenge during heat stress is improved with inspiratory resistance breathing.

NEW FINDINGS: What is the central question of this study? Does inspiratory resistance breathing improve tolerance to simulated haemorrhage in individuals with elevated internal temperatures? What is the main finding and its importance? The main finding of this study is that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress. These findings demonstrate a scenario in which exploitation of the respiratory pump can ameliorate serious conditions related to systemic hypotension. ABSTRACT: Heat exposure impairs human blood pressure control and markedly reduces tolerance to a simulated haemorrhagic challenge. Inspiratory resistance breathing enhances blood pressure control and improves tolerance during simulated haemorrhage in normothermic individuals. However, it is unknown whether similar improvements occur with this manoeuvre in heat stress conditions. In this study, we tested the hypothesis that inspiratory resistance breathing improves tolerance to simulated haemorrhage in individuals with elevated internal temperatures. On two separate days, eight subjects performed a simulated haemorrhage challenge [lower-body negative pressure (LBNP)] to presyncope after an increase in internal temperature of 1.3 ± 0.1°C. During one trial, subjects breathed through an inspiratory impedance device set at 0 cmH2 O of resistance (Sham), whereas on a subsequent day the device was set at -7 cmH2 O of resistance (ITD). Tolerance was quantified as the cumulative stress index. Subjects were more tolerant to the LBNP challenge during the ITD protocol, as indicated by a > 30% larger cumulative stress index (Sham, 520 ± 306 mmHg min; ITD, 682 ± 324 mmHg min; P < 0.01). These data indicate that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress.

Evolución de la ventilación mecánica no invasiva en la bronquiolitis / Evolution of non-invasive ventilation in acute bronchiolitis

OBJETIVOS: Estudiar la evolución durante 12 años del uso de la ventilación mecánica invasiva (VMI) y no invasiva (VNI) en niños con bronquiolitis ingresados en una unidad de cuidados intensivos pediátricos (UCIP). PACIENTES Y MÉTODOS: Estudio retrospectivo observacional de 12 años de duración (2001-2012) en el que se incluyó a todos los niños ingresados con bronquiolitis en UCIP que requirieron VMI y/o VNI. Se analizaron las características demográficas, el tipo de asistencia respiratoria y la evolución clínica, comparándose los primeros 6 años de estudio con los segundos. RESULTADOS: Se estudió a 196 pacientes. Un 30,1% requirió VMI y un 93,3% VNI. La mediana de duración de VMI fue de 9,5 días y la de VNI de 3 días. La duración de ingreso en UCIP fue de 7 días y falleció un 2% de los pacientes. La utilización de VNI aumentó del 79,4% en el primer periodo al 100% en el segundo periodo (p < 0,0001) y disminuyó el de VMI del 46% en el primer periodo al 22,6% en el segundo (p < 0,0001). La presión positiva continua en la vía aérea y el tubo endotraqueal cortado fueron la modalidad y la interfase más utilizadas, aunque en el segundo periodo aumentó significativamente el uso de ventilación con 2 niveles de presión (p < 0,0001) y de púas nasales (p < 0,0001), y disminuyó la duración de ingreso en la UCIP (p = 0,011). CONCLUSIONES: La mayor utilización de VNI en pacientes con bronquiolitis en nuestra unidad en los últimos años se asoció a una disminución de la necesidad de VMI y de la duración del ingreso en la UCIP

OBJECTIVES: The aim of the study was to analyse the evolution, over a12-year period, of the use of non-invasive (NIV) and invasive ventilation (IV) in children admitted to a Paediatric Intensive Care Unit (PICU) due to acute bronchiolitis. PATIENTS AND METHODS: A retrospective observational study was performed including all children who were admitted to the PICU requiring NIV or IV between 2001 and 2012. Demographic characteristics, ventilation assistance and clinical outcome were analysed. A comparison was made between the first six years and the last 6 years of the study. RESULTS: A total of 196 children were included; 30.1% of the subjects required IV and 93.3% required NIV. The median duration of IV was 9.5 days and NIV duration was 3 days. The median PICU length of stay was 7 days, and 2% of the patients died. The use of NIV increased from 79.4% in first period to 100% in the second period (P<.0001) and IV use decreased from 46% in the first period to 22.6% in the last 6 years (P<.0001). Continuous positive airway pressure and nasopharyngeal tube were the most frequently used modality and interface, although the use of bi-level non-invasive ventilation (P<.001) and of nasal cannulas significantly increased(P<.0001) in the second period, and the PICU length of stay was shorter (P=.011). CONCLUSION: The increasing use of NIV in bronchiolitis in our PICU during the last 12 years was associated with a decrease in the use of IV and length of stay in the PICU

Optimum insufflation capacity and peak cough flow in neuromuscular disorders.

RATIONALE: For patients with neuromuscular disorders, lung insufflation with positive pressure is an accepted technique to increase inspiratory volume over VC to improve peak cough flow (PCF). OBJECTIVES: The aim of the study was to determine the pressure or volume required to achieve the highest individual PCF. METHODS: In 40 patients dependent on noninvasive ventilation (VC, 16 ± 11% predicted; age, 20 ± 4 yr) and in 20 healthy control subjects, insufflation capacity (IC) was measured during titration from 10 to maximum 40 mbar using intermittent positive pressure breathing (IPPB) or the lung insufflation assist maneuver (LIAM) of the VENTIlogic LS ventilator. MEASUREMENTS AND MAIN RESULTS: IPPB or LIAM titration resulted in a pressure-volume curve with an estimated total compliance of 0.23 ± 0.11 L/kPa in the patients and 1.0 ± 0.3 L/kPa in the controls and a plateau for IC at pressures between 30 and 40 mbar. IPPB or LIAM improved VC from 451 ± 229 ml to a maximum IC (ICmax) of 1,027 ± 329 ml, and PCF improved from 109 ± 45 to 202 ± 62 L/min (P < 0.01 for all). The highest individual PCF was achieved with 27 ± 6 mbar and an IC of 924 ± 379 ml, which was significantly below ICmax (P < 0.01). CONCLUSIONS: A submaximal insufflation is ideal for generating the best individual PCF even in patients with severely reduced compliance of the respiratory system. Optimum insufflation capacity can be achieved using IPPB or LIAM with moderate pressures. Both techniques are equally effective and considered safe.

Aplicación individualizada de la presión positiva al final de la espiración en pacientes con síndrome de distrés respiratorio agudo / Individualized positive end-expiratory pressure application in patients with acute respiratory distress syndrome

En el manejo actual del síndrome de distrés respiratorio agudo, la aplicación de ventilación mecánica se debe realizar bajo una estrategia protectora, evitando el desarrollo de iatrogenia, entre la que se incluye el daño pulmonar asociado a la misma (ventilator-induced lung injury). Uno de los mecanismos implicados en este daño es el atelectrauma, abogándose por la aplicación de presión positiva al final de la espiración (PEEP) para evitarlo. El nivel de PEEP a aplicar no está definido y en muchas ocasiones se realiza dependiendo de la cantidad de oxígeno aportada al paciente en cada momento. Sin embargo, esta estrategia no tiene en cuenta la mecánica respiratoria que varía de un paciente a otro y que depende de múltiples factores entre los que destaca el tiempo de evolución del síndrome de distrés respiratorio agudo. Por ello, revisamos los diferentes métodos de ajuste de la PEEP, centrándonos en las ventajas derivadas de una aplicación individualizada

Current treatment of acute respiratory distress syndrome is based on ventilatory support with a lung protective strategy, avoiding the development of iatrogenic injury, including ventilator-induced lung injury. One of the mechanisms underlying such injury is atelectrauma, and positive end-expiratory pressure (PEEP) is advocated in order to avoid it. The indicated PEEP level has not been defined, and in many cases is based on the patient oxygen requirements for maintaining adequate oxygenation. However, this strategy does not consider the mechanics of the respiratory system, which varies in each patient and depends on many factors-including particularly the duration of acute respiratory distress syndrome. A review is therefore made of the different methods for adjusting PEEP, focusing on the benefits of individualized application

Comparison of three cough-augmentation techniques in neuromuscular patients: mechanical insufflation combined with manually assisted cough, insufflation-exsufflation alone and insufflation-exsufflation combined with manually assisted cough.

BACKGROUND: Mechanical insufflation-exsufflation (MI-E), more commonly known as 'cough assist therapy', is a method which produces inspiratory and expiratory assistance to improve cough performances. However, other alternatives or combinations are possible. OBJECTIVE: The objective was to compare the effects of mechanical insufflation combined with manually assisted coughing (MAC), insufflation-exsufflation alone and insufflation-exsufflation combined with MAC in neuromuscular patients requiring cough assistance. METHODS: Eighteen neuromuscular patients with severe respiratory muscle dysfunction and peak cough flow (PCF) lower than 3 liters/s or maximal expiratory pressure (MEP) lower than +45 cm H2O were studied. Patients were studied under three cough-assisted conditions, which were used in random order: insufflation by intermittent positive-pressure breathing (IPPB) combined with MAC, MI-E and MI-E + MAC. RESULTS: Overall, PCF was higher with IPPB + MAC than with MI-E + MAC or MI-E alone. Among the 12 patients who had higher PCF values with IPPB + MAC than with the two other techniques, 9 exhibited mask pressure swings during MI-E exsufflation, with a transient positive-pressure value due to the expiratory flow produced by the combined patient cough effort and MAC. Each of these 9 patients had higher PCF values (>5 liters/s) than did the other 9 patients when using IPPB + MAC. CONCLUSION: Our results indicate that adding the MI-E device to MAC is unhelpful in patients whose PCF with an insufflation technique and MAC exceeds 5 liters/s. This is because the expiratory flow produced by the patient's effort and MAC transitorily exceeds the vacuum capacity of the MI-E device, which therefore becomes a transient load against the PCF.

Presión positiva teleespiratoria alta o convencional en el síndrome de distrés respiratorio agudo / High or conventional positive end-expiratory pressure in acute respiratory distress

En el síndrome de distrés respiratorio agudo se puede necesitar una presión positiva teleespiratoria (PEEP) elevada, sin embargo, no se ha llegado a determinar cuánto. Varios ensayos clínicos han comparado esos niveles con los convencionales en este síndrome. Globalmente, aunque la PEEP elevada mejora la oxigenación y es segura, no mejora la mortalidad. No obstante, los metaanálisis han puesto de manifiesto 2 situaciones en las que una PEEP elevada puede disminuir la mortalidad: en el síndrome de distrés respiratorio agudo grave y cuando se titula mediante las características de la mecánica pulmonar. Cinco estudios han explorado esto último, todos de pequeño tamaño muestral, usando diferentes maneras de determinar la PEEP óptima. Resulta necesario, por tanto, realizar un estudio con el suficiente tamaño muestral que compare el tratamiento de pacientes con síndrome de distrés respiratorio agudo grave mediante una estrategia de ventilación protectora, con PEEP elevada, guiada por las características de la mecánica pulmonar y la ventilación según el protocolo de la ARDS Network

Patients with acute respiratory distress syndrome may require high positive endexpiratory pressure (PEEP) levels, though the optimum level remains to be established. Several clinical trials have compared high PEEP levels versus conventional PEEP. Overall, although high PEEP levels improve oxygenation and are safe, they do not result in a significant reduction of the mortality rates. Nevertheless, some metaanalyses have revealed 2 situations in which high PEEP may decrease mortality: When used in severe distress and when PEEP is set following thec haracteristics of lung mechanics. Five studies have explored this latter scenario. Unfortunately, all of them have small sample sizes and have used different means to determine optimum PEEP. It is therefore necessary to conduct studies of sufficient sample size to compare the treatment of patients with severe acute respiratory distress syndrome, using a protective ventilation strategy with high PEEP guided by the characteristics of lung mechanics and ventilation with the protocol proposed by the ARDS Network

Comparación de la respiración con presión positiva intermitente y la presión espiratoria positiva temporal en pacientes con enfermedad pulmonar obstructiva crónica grave / Comparison of Intermittent Positive Pressure Breathing and Temporary Positive Expiratory Pressure in Patients With Severe Chronic Obstructive Pulmonary Disease

ANTECEDENTES: Los resultados que respaldan el uso y la efectividad de los dispositivos de presión espiratoria positiva en pacientes con enfermedad pulmonar obstructiva (EPOC) continúan siendo objeto de controversia. Hemos evaluado la hipótesis de que la adición de la TPEP o la IPPB a un tratamiento farmacológico estándar pueda aportar un beneficio clínico adicional respecto al tratamiento farmacológico solo en los pacientes con EPOC grave. MÉTODOS: Un total de 45 pacientes fueron asignados aleatoriamente a los 3 grupos siguientes: un grupo fue tratado con IPPB, otro fue tratado con TPEP y un tercer grupo recibió únicamente tratamiento farmacológico (grupo de control).Las variables de valoración principales fueron la puntuación de la escala o cuestionario relativo a la disnea (escala del MRC); la de disnea, tos y esputo (BCSS); y la de calidad de vida (test de evaluación de la EPOC) (CAT). Las variables de valoración secundarias fueron las pruebas de la función respiratoria, la gasometría arterial y los análisis hematológicos. RESULTADOS: Tanto los pacientes del grupo de IPPB como los del grupo de TPEP mostraron una mejoría significativa en 2 de las 3 evaluaciones (MRC y CAT) en comparación con el grupo de control. Sin embargo, en el análisis de comparación de los grupos para las mismas variables en el grupo de IPPB frente al grupo de TPEP observamos una mejoría significativa en el grupo de IPPB (p ≤ 0,05 para la escala del MRC y p ≤ 0,01 para el CAT).La diferencia de efecto de las 2 técnicas se pone de manifiesto en los resultados de las pruebas de la función pulmonar: la IPPB aumenta los valores de FVC, FEV1 y MIP; esto refleja su capacidad de aumentar el volumen pulmonar. Por su parte, la TPEP aumenta la FVC y el FEV1 (en menor medida que la IPPB), pero eleva la MEP, mientras que reduce la capacidad pulmonar total y el volumen residual. CONCLUSIONES: Las 2 técnicas (IPPB y TPEP) mejoran significativamente la disnea, los instrumentos de valoración de la calidad de vida y la función pulmonar en los pacientes con una EPOC grave. La IPPB mostró una mayor efectividad en la mejora de los instrumentos de evaluación de la disnea y la calidad de vida (MRC y CAT) en comparación con la TPEP

BACKGROUND: Results supporting the use and the effectiveness of positive expiratory, pressure devices in chronic obstructive pulmonary disease (COPD) patients are still controversial, We have tested the hypothesis that adding TPEP or IPPB to standard pharmacological therapy may provide additional clinical benefit over, pharmacological therapy only in patients with severe COPD. METHODS: Fourty-five patients were randomized in three groups: a group was treated; with IPPB, a group was treated with TPEP and a group with pharmacological; therapy alone (control group). Primary outcome measures included the measurement of scale or, questionnaire concerning dyspnea (MRC scale), dyspnea, cough, and, sputum (BCSS) and quality of life (COPD assessment test) (CAT). Secondary, outcome measures were respiratory function testing, arterial blood gas, analysis, and hematological examinations. RESULTS: Both patients in the IPPB group and in the TPEP group showed a significant, improvement in two of three tests (MRC, CAT) compared to the control, group. However, in the group comparison analysis for, the same variables between IPPB group and TPEP group we observed a, significant improvement in the IPPB group (P≤0.05 for MRC and P≤0.01 for, CAT).The difference of action of the two techniques are evident in the results of, pulmonary function testing: IPPB increases FVC, FEV1, and MIP; this reflects, its capacity to increase lung volume. Also TPEP increases FVC and FEV1 (less, than IPPB), but increases MEP, while decreasing total lung capacity and, residual volume. CONCLUSIONS: The two techniques (IPPB and TPEP) improves significantly dyspnea; quality of; life tools and lung function in patients with severe COPD. IPPB demonstrated a greater effectiveness to improve dyspnea and quality of life tools (MRC, CAT) than TPEP

Evaluation of manual and automatic manually triggered ventilation performance and ergonomics using a simulation model.

BACKGROUND: In the absence of endotracheal intubation, the manual bag-valve-mask (BVM) is the most frequently used ventilation technique during resuscitation. The efficiency of other devices has been poorly studied. The bench-test study described here was designed to evaluate the effectiveness of an automatic, manually triggered system, and to compare it with manual BVM ventilation. METHODS: A respiratory system bench model was assembled using a lung simulator connected to a manikin to simulate a patient with unprotected airways. Fifty health-care providers from different professional groups (emergency physicians, residents, advanced paramedics, nurses, and paramedics; n = 10 per group) evaluated manual BVM ventilation, and compared it with an automatic manually triggered device (EasyCPR). Three pathological situations were simulated (restrictive, obstructive, normal). Standard ventilation parameters were recorded; the ergonomics of the system were assessed by the health-care professionals using a standard numerical scale once the recordings were completed. RESULTS: The tidal volume fell within the standard range (400-600 mL) for 25.6% of breaths (0.6-45 breaths) using manual BVM ventilation, and for 28.6% of breaths (0.3-80 breaths) using the automatic manually triggered device (EasyCPR) (P < .0002). Peak inspiratory airway pressure was lower using the automatic manually triggered device (EasyCPR) (10.6 ± 5 vs 15.9 ± 10 cm H2O, P < .001). The ventilation rate fell consistently within the guidelines, in the case of the automatic manually triggered device (EasyCPR) only (10.3 ± 2 vs 17.6 ± 6, P < .001). Significant pulmonary overdistention was observed when using the manual BVM device during the normal and obstructive sequences. The nurses and paramedics considered the ergonomics of the automatic manually triggered device (EasyCPR) to be better than those of the manual device. CONCLUSIONS: The use of an automatic manually triggered device may improve ventilation efficiency and decrease the risk of pulmonary overdistention, while decreasing the ventilation rate.

Relationship between positive end-expiratory pressure and internal jugular vein cross-sectional area.

BACKGROUND: Application of positive end-expiratory pressure (PEEP) has been used to increase the cross-sectional area (CSA) of the right internal jugular vein (IJV) in order to facilitate catheterisation. We aimed to determine the PEEP level at which the maximum increase of CSA occurred. METHODS: We enrolled 60 American Society of Anesthesiologists physical status I and II patients undergoing general endotracheal anaesthesia. The CSA was measured in the supine position with no PEEP (control condition, P0) and after applying five different PEEPs in random order: 3 (P3), 6 (P6), 9 (P9), 12 (P12), and 15 (P15) cm H(2) O. Ultrasound was used to measure and record the CSA of the right IJV at the level of the cricoid cartilage. RESULTS: All PEEP levels increased the CSA of the right IJV relative to the control (all P < 0.05). On average, P3, P6, P9, P12, and P15 increased the CSA by 21.5, 37.4, 51.9, 66.5, and 72.4%, respectively. There was no significant increase in CSA above a PEEP of 12 cm H(2) O. CONCLUSION: The application of PEEP effectively increases the CSA of the right IJV. The PEEP giving the largest CSA is 12 cm H(2) O.

Evaluation of the inspiratory pressure using a digital vacuometer in mechanically ventilated patients: analysis of the time to achieve the inspiratory peak.

BACKGROUND: The measurement of the maximal inspiratory pressure (P(Imax)) is of great importance in choosing the time for the start of weaning. OBJECTIVE: To measure the inspiratory pressure in mechanically ventilated patients suitable for weaning to determine the point at which the P(Imax) is achieved within 60 seconds of observation, and analyze factors associated with P(Imax) values. METHODS: Measurement of P(Imax) was accomplished with a digital vacuometer with a unidirectional valve, which allows only exhalation (P(ImaxUV)). With this technique, values are registered and stored, remaining accessible whenever necessary. All patients were on mechanical ventilation, and met the criteria recommended by the American Thoracic Society/European Respiratory Society in 2007 to undergo weaning trial. RESULTS: Eighty-four from the 87 enrolled patients completed the test. No patients reached the P(ImaxUV) in the first 20 seconds of observation. P(ImaxUV) was achieved between 20.1 and 40 seconds in 12 patients (14.0%), and between 40.1 and 60 seconds in 72 cases (86.0%). In a multivariate analysis model in which age, sex, days of mechanical ventilation, APACHE score, and respiratory drive (measured as airway-occlusion pressure 0.1 s after the start of inspiratory flow [P(0.1)]) were included, only age (P = .006) and P(0.1) (P = .003) were significantly associated with the values of P(ImaxUV). CONCLUSIONS: Within an observation period of 60 seconds, the majority of patients reached the maximal inspiratory peak between 40.1 and 60 seconds. Older patients were found to have lower P(ImaxUV) values, whereas higher values for P(0.1) strongly correlated with higher P(ImaxUV) values. These findings are potentially useful to improve successful weaning prediction in the future, but further studies are needed to better clarify this issue.

Prolonging survival in amyotrophic lateral sclerosis: efficacy of noninvasive ventilation and uncuffed tracheostomy tubes.

OBJECTIVE: To assess the efficacy of noninvasive ventilatory support and intermittent positive pressure ventilation via uncuffed tracheostomy tubes (uTIPPV) to prolong survival in amyotrophic lateral sclerosis. DESIGN: Survival was prolonged by continuous noninvasive ventilatory support or TIPPV dependence. Once noninvasive ventilatory support was no longer adequate for six noninvasive ventilatory support users, they and 22 others underwent tracheotomy within 1 mo of measurement of spirometry (forced vital capacity and forced volume expired in 1 sec), peak cough flows, maximum insufflation capacity, manually assisted peak cough flows, and mechanically assisted peak cough flows. Glottic function was estimated by maximum insufflation capacity, FVC difference, and bulbar-innervated muscle function by Norris scale bulbar-innervated muscle subscore. Cuffless tubes were replaced by cuffed ones when hypoventilation developed despite increasing uTIPPV volumes. RESULTS: The survival of 22 patients was prolonged by continuous noninvasive ventilatory support dependence for 7.8 +/- 8.1 mos (range, 1-36 mos; median, 5 mos) after 13.9 +/- 11.2 mos (range, 2-36 mos) of part-time noninvasive ventilatory support. Six of these and 22 others underwent tracheotomy and initially used uTIPPV effectively. For ten of the 28 (35.7%) patients, the tubes had to be replaced by cuffed ones after 5.7 +/- 7.8 mos with the other 18 still using tracheostomy intermittent positive pressure ventilation volumes via uncuffed tubes for 20.2 +/- 17.6 mos at data collection. Pretracheotomy FVC was significantly lower in the ten patients who eventually required cuffed tubes (0.70 +/- 0.44 vs. 1.06 +/- 0.43 L, P < 0.05). The bulbar-innervated muscle was significantly lower when the uTIPPV users required cuffed TIPPV than when beginning uTIPPV (Norris scale bulbar-innervated muscle subscore, 3.20 +/- 1.30 vs. 8.00 +/- 3.20, P < 0.05), respectively. CONCLUSIONS: Noninvasive and tracheostomy IPPV via cuffless tubes can prolong survival for patients with amyotrophic lateral sclerosis until excessive air leak and hypoventilation necessitate a cuffed tube.

Noninvasive ventilation reduces intubation in chest trauma-related hypoxemia: a randomized clinical trial.

BACKGROUND: Guidelines for noninvasive mechanical ventilation (NIMV) recommend continuous positive airway pressure in patients with thoracic trauma who remain hypoxic despite regional anesthesia. This recommendation is rated only by level C evidence because randomized controlled trials in this specific population are lacking. Our aim was to determine whether NIMV reduces intubation in severe trauma-related hypoxemia. METHODS: This was a single-center randomized clinical trial in a nine-bed ICU of a level I trauma hospital. Inclusion criteria were patients with Pao(2)/Fio(2)<200 for >8 h while receiving oxygen by high-flow mask within the first 48 h after thoracic trauma. Patients were randomized to remain on high-flow oxygen mask or to receive NIMV. The interface was selected based on the associated injuries. Thoracic anesthesia was universally supplied unless contraindicated. The primary end point was intubation; secondary end points included length of hospital stay and survival. Statistical analysis was based on multivariate analysis. RESULTS: After 25 patients were enrolled in each group, the trial was prematurely stopped for efficacy because the intubation rate was much higher in controls than in NIMV patients (10 [40%] vs 3 [12%], P = .02). Multivariate analysis adjusted for age, gender, chronic heart failure, and Acute Physiology and Chronic Health Evaluation II at admission revealed NIMV as the only variable independently related to intubation (odds ratio, 0.12; 95% CI, 0.02-0.61; P = .01). Length of hospital stay was shorter in NIMV patients (14 vs 21 days P = .001), but no differences were observed in survival or other secondary end points. CONCLUSION: NIMV reduced intubation compared with oxygen therapy in severe thoracic trauma-related hypoxemia.

Análisis de coste-eficacia de la graduación automática de la presión positiva continua de la vía aérea en el domicilio: ¿una o 2 noches? / Cost-effectiveness analysis of automatic titration of continuous positive airway pressure at home in 1 night versus 2 nights

OBJETIVO: Evaluar el coste-eficacia de la graduaciónautomática de la presión positiva continua de la vía aérea(CPAP) en el domicilio, en una y 2 noches consecutivas, enpacientes con síndrome de apneas-hiponeas durante el sueño.PACIENTES Y MÉTODOS: Se practicó un estudio degraduación domiciliaria con un equipo de CPAP automática(APAP) durante 2 noches consecutivas a 100 pacientes consíndrome de apneas-hipopneas durante el sueño e indicaciónde tratamiento con CPAP. Se evaluaron el número deestudios satisfactorios y el coste resultante de la primeranoche y de las 2 noches. Se compararon las necesidades depresión durante cada noche y la concordancia entre lapresión seleccionada visualmente por 2 observadores.RESULTADOS: La graduación de CPAP fue satisfactoria enel 85 y el 80% de los pacientes en la primera y la segundanoches, respectivamente, y en el 88% después de las 2noches. No hubo diferencias significativas entre las 2 nochesen la presión percentil 95% (media ± desviación estándar:10,2 ± 1,8 y 10,2 ± 1,6 cmH2O), la presión media (7,8 ± 1,7 y7,7 ± 1,7 cmH2O) y la presión visual (9,4 ± 1,5 y 9,4 ± 1,4cmH2O). Se obtuvo un buen grado de concordancia entre 2observadores en la selección de presión (kappa = 0,956 parala noche 1; kappa = 0,91 para la noche 2). El coste de losestudios fue 232,63 € para la primera noche y 227,93 € paralas 2 noches consecutivas.CONCLUSIONES: Con un coste similar, la adopción de unprotocolo de graduación automática de la CPAP una noche enel domicilio permite incrementar sustancialmente el númerode pacientes estudiados, respecto a 2 noches consecutivas

OBJECTIVE: To assess the cost-effectiveness of automaticcontinuous positive airway pressure (CPAP) titration athome on 1 night or 2 consecutive nights in patients with thesleep apnea-hypopnea syndrome (SAHS).PATIENTS AND METHODS: A home titration study wasperformed using automatic CPAP for 2 consecutive nightson 100 patients with SAHS and an indication for CPAP. Thenumber of successful studies and the costs of the first nightand both nights were analyzed. The pressure requirementson each night and the agreement between the pressuresselected visually by 2 different observers were compared.RESULTS: CPAP titration was successful in 85% and 80%of patients on the first night and second night, respectively,and in 88% of patients after both nights. No significantdifferences between the 2 nights were found for the followingparameters: 95th percentile pressure (mean [SD], 10.2 [1.8]cm H2O and 10.2 [1.6] cm H2O on the first and secondnights, respectively), mean pressure (7.8 [1.7] cm H2O and7.7 [1.7] cm H2O), or the pressure selected visually (9.4 [1.5]cm H2O and 9.4 [1.4] cm H2O). Interobserver agreement onthe pressure selected was good: the k statistics were 0.956 forthe first night and 0.91 for the second night. The 1-nightstudy cost €232.63 and the 2-night study cost €227.93.CONCLUSIONS: Automatic CPAP titration at home for1 night enables a substantially greater number of patients tobe studied at a similar cost than is possible when titration isaccomplished in 2 consecutive nights