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Research paper thumbnail of Volume-assured pressure support ventilation (VAPSV). A new approach for reducing muscle workload during acute respiratory failure

Chest, 1992

This study reports the preliminary clinical evaluation of a new mode of ventilation--volume-assur... more This study reports the preliminary clinical evaluation of a new mode of ventilation--volume-assured pressure support ventilation (VAPSV)--which incorporates inspiratory pressure support (PSV) with conventional volume-assisted cycles (VAV). This combination optimizes the inspiratory flow during assisted/controlled cycles, reducing the patient's respiratory burden commonly observed during VAV. Different from conventional PSV, VAPSV assures precise control of tidal volume (VT) in unstable patients. Eight patients with acute respiratory failure (ARF) were submitted to assisted ventilation under VAV and VAPSV. Patient's ventilatory workload (evaluated through the pressure-time product, mechanical work per liter of ventilation, and work per minute) and patient's ventilatory drive (occlusion pressure--P0.1) were significantly reduced during VAPSV. This "relief" was more evident among the most distressed patients (p < 0.001), allowing a reduction of more than 60 percent in muscle load, without the need of increasing peak tracheal pressure. Mean inspiratory flow (VT/TI), VT, and effective dynamic compliance were significantly increased during VAPSV, whereas the effective inspiratory impedance decreased. These mechanical advantages of VAPSV allowed a reduction of intrinsic PEEP, whenever it was present. Blood gas values were similar in both periods. We concluded that VAPSV is a promising form of ventilatory support. At the same time that it was able to safely assure a minimum preset VT, VAPSV reduced patient workload and improved synchrony between the patient and the ventilator during ARF.

Research paper thumbnail of Modelo de cámara inhaladora para los estudios controlados sobre la toxicidad del humo del tabaco en los roedores

Archivos De Bronconeumologia, 2010

Research paper thumbnail of An Inhalation Chamber Model for Controlled Studies of Tobacco Smoke Toxicity in Rodents

Archivos De Bronconeumologia, 2010

Research paper thumbnail of Mathematical Model for a New Mode of Artificial Ventilation: Volume Assisted Pressure Supported Ventilation: A Comparative Study

Artificial Organs, 1995

Abstract: The patient submitted to artificial ventilation generally is connected to a high impeda... more Abstract: The patient submitted to artificial ventilation generally is connected to a high impedance flow source with controlled respiratory cycles to assure volume requirements or to a low impedance pressure source with spontaneous cycles to allow synchronization between his effort and system flow delivery. These two types of cycles represent the initial and final stages of artificial ventilation. The patient who needs a volume guarantee and at the same time presents unstable or insufficient inspiratory effort is difficult to manage with assisted cycles which are analogous to the controlled presence of a high impedance flow source. This paper presents a new approach where the respiratory cycles are obtained by the combination of flow and pressure sources using mathematical modeling. These cycles, named volume assisted pressure supported (VAPS) cycles, are compared with conventional assisted cycles showing a decrease in the patient work of breathing (WOB) during assisted ventilation. The theoretical results have been confirmed by clinical trials.

Research paper thumbnail of Tidal volume during mechanical ventilation in the newborn: Is it possible to estimate according to clinical parameters?: VOLUME CORRENTE DURANTE A VENTILA????O MECANICA EM REC??M NASCIDOS

Pediatric Critical Care Medicine, 2005

Research paper thumbnail of Nasal-airway pressure release ventilation (NASAL-APRV) and nasal-continuous positive airway pressure (NASAL-CPAP): hemodynamic, respiratory and gasometric effects

Research paper thumbnail of Liberação de pressão de vias aéreas em pacientes pediátricos submetidos à cirurgia cardíaca

Revista Da Associacao Medica Brasileira, 2000

Research paper thumbnail of The Effects of Abdominal Opening on Respiratory Mechanics During General Anesthesia in Normal and Morbidly Obese Patients: A Comparative Study

Anesthesia and Analgesia, 2002

Morbid obesity has a profound effect on respiratory mechanics and gas exchange. However, most stu... more Morbid obesity has a profound effect on respiratory mechanics and gas exchange. However, most studies were performed in morbidly obese patients before or after anesthesia. We tested the hypothesis that anesthesia and abdominal opening could modify the elastic and resistive properties of the respiratory system. Eleven morbidly obese and eight normal-weight patients scheduled for gastric binding and cancer treatment, respectively, under laparotomy were studied. Respiratory mechanics, partitioned into its lung and chest wall components, were investigated during surgery by means of the end-inspiratory inflation occlusion method and esophageal balloon at five time points. Static respiratory and lung compliance were markedly reduced in obese patients; on the contrary, static compliance of chest wall presented comparable values in both groups. Obese patients also presented higher resistances of the total respiratory system, lung and chest wall, as well as "additional" lung resistance. Mainly in obese patients, laparotomy provoked a significant increase in lung compliance and decrease in "additional" lung resistance 1 h after the peritoneum was opened, which returned to original values after the peritoneum had been closed (P < 0.005). In obese patients, low respiratory compliance and higher airway resistance were mainly determined by the lung component.

Research paper thumbnail of Volume-assured pressure support ventilation (VAPSV). A new approach for reducing muscle workload during acute respiratory failure

Chest, 1992

This study reports the preliminary clinical evaluation of a new mode of ventilation--volume-assur... more This study reports the preliminary clinical evaluation of a new mode of ventilation--volume-assured pressure support ventilation (VAPSV)--which incorporates inspiratory pressure support (PSV) with conventional volume-assisted cycles (VAV). This combination optimizes the inspiratory flow during assisted/controlled cycles, reducing the patient's respiratory burden commonly observed during VAV. Different from conventional PSV, VAPSV assures precise control of tidal volume (VT) in unstable patients. Eight patients with acute respiratory failure (ARF) were submitted to assisted ventilation under VAV and VAPSV. Patient's ventilatory workload (evaluated through the pressure-time product, mechanical work per liter of ventilation, and work per minute) and patient's ventilatory drive (occlusion pressure--P0.1) were significantly reduced during VAPSV. This "relief" was more evident among the most distressed patients (p < 0.001), allowing a reduction of more than 60 percent in muscle load, without the need of increasing peak tracheal pressure. Mean inspiratory flow (VT/TI), VT, and effective dynamic compliance were significantly increased during VAPSV, whereas the effective inspiratory impedance decreased. These mechanical advantages of VAPSV allowed a reduction of intrinsic PEEP, whenever it was present. Blood gas values were similar in both periods. We concluded that VAPSV is a promising form of ventilatory support. At the same time that it was able to safely assure a minimum preset VT, VAPSV reduced patient workload and improved synchrony between the patient and the ventilator during ARF.

Research paper thumbnail of Modelo de cámara inhaladora para los estudios controlados sobre la toxicidad del humo del tabaco en los roedores

Archivos De Bronconeumologia, 2010

Research paper thumbnail of An Inhalation Chamber Model for Controlled Studies of Tobacco Smoke Toxicity in Rodents

Archivos De Bronconeumologia, 2010

Research paper thumbnail of Mathematical Model for a New Mode of Artificial Ventilation: Volume Assisted Pressure Supported Ventilation: A Comparative Study

Artificial Organs, 1995

Abstract: The patient submitted to artificial ventilation generally is connected to a high impeda... more Abstract: The patient submitted to artificial ventilation generally is connected to a high impedance flow source with controlled respiratory cycles to assure volume requirements or to a low impedance pressure source with spontaneous cycles to allow synchronization between his effort and system flow delivery. These two types of cycles represent the initial and final stages of artificial ventilation. The patient who needs a volume guarantee and at the same time presents unstable or insufficient inspiratory effort is difficult to manage with assisted cycles which are analogous to the controlled presence of a high impedance flow source. This paper presents a new approach where the respiratory cycles are obtained by the combination of flow and pressure sources using mathematical modeling. These cycles, named volume assisted pressure supported (VAPS) cycles, are compared with conventional assisted cycles showing a decrease in the patient work of breathing (WOB) during assisted ventilation. The theoretical results have been confirmed by clinical trials.

Research paper thumbnail of Tidal volume during mechanical ventilation in the newborn: Is it possible to estimate according to clinical parameters?: VOLUME CORRENTE DURANTE A VENTILA????O MECANICA EM REC??M NASCIDOS

Pediatric Critical Care Medicine, 2005

Research paper thumbnail of Nasal-airway pressure release ventilation (NASAL-APRV) and nasal-continuous positive airway pressure (NASAL-CPAP): hemodynamic, respiratory and gasometric effects

Research paper thumbnail of Liberação de pressão de vias aéreas em pacientes pediátricos submetidos à cirurgia cardíaca

Revista Da Associacao Medica Brasileira, 2000

Research paper thumbnail of The Effects of Abdominal Opening on Respiratory Mechanics During General Anesthesia in Normal and Morbidly Obese Patients: A Comparative Study

Anesthesia and Analgesia, 2002

Morbid obesity has a profound effect on respiratory mechanics and gas exchange. However, most stu... more Morbid obesity has a profound effect on respiratory mechanics and gas exchange. However, most studies were performed in morbidly obese patients before or after anesthesia. We tested the hypothesis that anesthesia and abdominal opening could modify the elastic and resistive properties of the respiratory system. Eleven morbidly obese and eight normal-weight patients scheduled for gastric binding and cancer treatment, respectively, under laparotomy were studied. Respiratory mechanics, partitioned into its lung and chest wall components, were investigated during surgery by means of the end-inspiratory inflation occlusion method and esophageal balloon at five time points. Static respiratory and lung compliance were markedly reduced in obese patients; on the contrary, static compliance of chest wall presented comparable values in both groups. Obese patients also presented higher resistances of the total respiratory system, lung and chest wall, as well as "additional" lung resistance. Mainly in obese patients, laparotomy provoked a significant increase in lung compliance and decrease in "additional" lung resistance 1 h after the peritoneum was opened, which returned to original values after the peritoneum had been closed (P < 0.005). In obese patients, low respiratory compliance and higher airway resistance were mainly determined by the lung component.

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