No abstract available.
Positive-Pressure Respiration, Intrinsic*

We have studied 27 patients on medical ventilation in whom we measured auto-PEEP by means of end expiratory airway occlusion. Four patients with ARDS had 10.25  2.05 cm H2O of auto PEEP. Six patients with COPD had 12.83  4.98 cm H2O of auto PEEP. Seven patients with acute severe asthma had 20.29  7.21 cm H2O of auto PEEP. Ten patients with neuromuscular disease had 5.2  4.07 cm H2O of auto PEEP. PEEP was set equal to half the auto-PEEP to treat patients with ARDS, COPD and acute severe asthma. We have show that the value of auto PEEP fell to 4.67  3.7 cm H2O in patient with ARDS, to 7  2.31 in patient of COPD and to 9.71  1.67 in patients of asthma. PEEP 50% of auto-PEEP is safe and does not worsen pulmonary hyperinflation
Positive-Pressure Respiration, Intrinsic ; Respiratory Insufficiency ; Respiration, Artificial

BACKGROUND: Unilateral lung hyperinflation develops in lungs with asymmetric compliance, which can lead to vital instability. The aim of this study was to investigate the respiratory dynamics and the effect of airway diameter on the distribution of tidal volume during mechanical ventilation in a lung model with asymmetric compliance. METHODS: Three groups of lung models were designed to simulate lungs with a symmetric and asymmetric compliance. The lung model was composed of two test lungs, lung1 and lung2. The static compliance of lung1 in C15, C60, and C120 groups was manipulated to be 15, 60, and 120 ml/cmH₂O, respectively. Meanwhile, the static compliance of lung2 was fixed at 60 ml/cmH₂O. Respiratory variables were measured above (proximal measurement) and below (distal measurement) the model trachea. The lung model was mechanically ventilated, and the airway internal diameter (ID) was changed from 3 to 8 mm in 1-mm increments. RESULTS: The mean ± standard deviation ratio of volumes distributed to each lung (VL1/VL2) in airway ID 3, 4, 5, 6, 7, and 8 were in order, 0.10 ± 0.05, 0.11 ± 0.03, 0.12 ± 0.02, 0.12 ± 0.02, 0.12 ± 0.02, and 0.12 ± 0.02 in the C15 group; 1.05 ± 0.16, 1.01 ± 0.09, 1.00 ± 0.07, 0.97 ± 0.09, 0.96 ± 0.06, and 0.97 ± 0.08 in the C60 group; and 1.46 ± 0.18, 3.06 ± 0.41, 3.72 ± 0.37, 3.78 ± 0.47, 3.77 ± 0.45, and 3.78 ± 0.60 in the C120 group. The positive end-expiratory pressure (PEEP) of lung1 was significantly increased at airway ID 3 mm (1.65 cmH₂O) in the C15 group; at ID 3, 4, and 5 mm (2.21, 1.06, and 0.95 cmH₂O) in the C60 group; and ID 3, 4, and 5 mm (2.92, 1.84, and 1.41 cmH₂O) in the C120 group, compared to ID 8 mm (P < 0.05). CONCLUSIONS: In the C15 and C120 groups, the tidal volume was unevenly distributed to both lungs in a positive relationship with lung compliance. In the C120 group, the uneven distribution of tidal volume was improved when the airway ID was equal to or less than 4 mm, but a significant increase of PEEP was observed.
Airway Obstruction ; Compliance ; Lung Compliance* ; Lung* ; Positive-Pressure Respiration ; Positive-Pressure Respiration, Intrinsic ; Respiration, Artificial ; Tidal Volume ; Trachea ; Ventilation

BACKGROUND: Unilateral lung hyperinflation develops in lungs with asymmetric compliance, which can lead to vital instability. The aim of this study was to investigate the respiratory dynamics and the effect of airway diameter on the distribution of tidal volume during mechanical ventilation in a lung model with asymmetric compliance. METHODS: Three groups of lung models were designed to simulate lungs with a symmetric and asymmetric compliance. The lung model was composed of two test lungs, lung1 and lung2. The static compliance of lung1 in C15, C60, and C120 groups was manipulated to be 15, 60, and 120 ml/cmH₂O, respectively. Meanwhile, the static compliance of lung2 was fixed at 60 ml/cmH₂O. Respiratory variables were measured above (proximal measurement) and below (distal measurement) the model trachea. The lung model was mechanically ventilated, and the airway internal diameter (ID) was changed from 3 to 8 mm in 1-mm increments. RESULTS: The mean ± standard deviation ratio of volumes distributed to each lung (VL1/VL2) in airway ID 3, 4, 5, 6, 7, and 8 were in order, 0.10 ± 0.05, 0.11 ± 0.03, 0.12 ± 0.02, 0.12 ± 0.02, 0.12 ± 0.02, and 0.12 ± 0.02 in the C15 group; 1.05 ± 0.16, 1.01 ± 0.09, 1.00 ± 0.07, 0.97 ± 0.09, 0.96 ± 0.06, and 0.97 ± 0.08 in the C60 group; and 1.46 ± 0.18, 3.06 ± 0.41, 3.72 ± 0.37, 3.78 ± 0.47, 3.77 ± 0.45, and 3.78 ± 0.60 in the C120 group. The positive end-expiratory pressure (PEEP) of lung1 was significantly increased at airway ID 3 mm (1.65 cmH₂O) in the C15 group; at ID 3, 4, and 5 mm (2.21, 1.06, and 0.95 cmH₂O) in the C60 group; and ID 3, 4, and 5 mm (2.92, 1.84, and 1.41 cmH₂O) in the C120 group, compared to ID 8 mm (P < 0.05). CONCLUSIONS: In the C15 and C120 groups, the tidal volume was unevenly distributed to both lungs in a positive relationship with lung compliance. In the C120 group, the uneven distribution of tidal volume was improved when the airway ID was equal to or less than 4 mm, but a significant increase of PEEP was observed.
Airway Obstruction ; Compliance ; Lung Compliance ; Lung ; Positive-Pressure Respiration ; Positive-Pressure Respiration, Intrinsic ; Respiration, Artificial ; Tidal Volume ; Trachea ; Ventilation

BACKGROUND: There are several METHODS: for auto-PEEP measurement during mechanical ventilation. The end-expiratory port occlusion (EEPO) method is simple and easy. Theoretically, auto- PEEP level can be also calculated by using trapped lung volume and static compliance. However, the relationship between measured auto-PEEP by EEPO method and the calculated auto-PEEP has not been studied. The purpose of this study is to observe the relationship between the measured and the calculated auto-PEEP. METHODS: 15 patients with auto-PEEP during mechanical ventilation were included. Auto-PEEP was measured by EEPO method, and calculated by using a formula; trapped lung volume/static compliance. All of the patients were paralyzed during the study. If the measured auto-PEEP is higher than calculated auto-PEEP, this patient was included in `high group'; in the opposite case, `low group'. We compared respiratory mechanics between these two groups. RESULTS: Measured auto-PEEP was 9.60+/-2.82 cmH2O, and calculated auto-PEEP was 9.78+/-2.90 cmH2O. There was statistically significant relationship between measured and calculated auto-PEEP (r=0.81, p<0.01). There was no difference on respiratory mechanics between `high group' and `low group'. CONCLUSIONS: The auto-PEEP obtained by calculation with trapped lung volume and static compliance showed a good correlation with that of using EEPO method in the paralyzed patients.
Compliance ; Humans ; Lung* ; Positive-Pressure Respiration, Intrinsic* ; Respiration, Artificial ; Respiratory Mechanics

During mechanical ventilation in the intensive care unit, auto-positive end-expiratory pressure (auto-PEEP) has been reported to occur in obstructive airway conditions aggravated by inappropriate ventilator settings. In this paper, we report a case of auto-PEEP-like problem during anesthesia, mainly caused by excessive sputum. After being positioned prone for spine surgery, the patient received pressure controlled ventilation at a low fresh gas flow rate. One hour after the start of surgery, sudden decreases in pressure and flow occurred. The typical maneuvers which could be performed by the anesthesiologists in the situations suggesting leakage within the breathing circuit consist of pressing the oxygen flush valve and manual hyperventilation for the initial evaluation. But from our experience in this case, we have learned that such maneuvers could cause unacceptable aggravation in the event of auto-PEEP. Also in this report, we discuss the difficulties in prediction based on the present knowledge of preoperative evaluation and the presumably best management policy regarding this type of auto-PEEP.
Anesthesia* ; Humans ; Hyperventilation ; Intensive Care Units ; Oxygen ; Positive-Pressure Respiration, Intrinsic ; Respiration ; Respiration, Artificial ; Spine ; Sputum ; Ventilation* ; Ventilators, Mechanical

BACKGROUND: The aim of the present study was to detect and quantify auto-positive end-expiratory pressure (auto-PEEP) in anesthetized patients using a Laser-Flex endotracheal tube (Mallincrodt, ID, 6.0 mm), by comparing the effects of changes in tidal volume and respiratory rate. METHODS: All patients (n = 30) undergoing elective surgery were anesthetized, paralyzed and intubated with a ID 8.0 mm endotracheal tube (n = 10, control), ID 6.0 mm endotracheal tube (n = 10, group S), or ID 6.0 mm Laser-Flex endotracheal tube (n = 10, group L), respectively. After anesthetic induction, ventilator settings using a Siemens Servo 900C were changed for a tidal volume of 8, 10 ml/kg, respiratory rates of 10, 12 or 14 breaths/min. Peak airway pressure was measured and auto-PEEP was quantified using an end-expiratory occlusion method. Data recorded on the Bicore CP-100 pulmonary monitor was transfered to a PC and analyzed by processing software (ANADAT). RESULTS: In group S and L, peak airway pressure and auto-PEEP were higher than control group and increased during an increase in tidal volume (P < 0.05). But they were increased significantly during an increase of respiratory rate, only when the tidal volume was 10 ml/kg (P < 0.05). CONCLUSIONS: There was an increase of auto-PEEP in anesthetized patients using a Laser-Flex endotracheal tube during incremental changes of tidal volume and respiratory rates.
Humans ; Positive-Pressure Respiration, Intrinsic* ; Respiratory Rate* ; Tidal Volume* ; Ventilators, Mechanical

BACKGROUND: Bronchoscopy in patients on mechanical ventilation is being performed much more frequently. However, there is little data on the changes in physiologic parameters and no established mechanical ventilation protocol during bronchoscopy. A decreasing or the removal of positive end-expiratory pressure (PEEP) during bronchoscopy may precipitate severe hypoxemia and/or derecruitment. METHODS: Our standardized mechanical ventilation protocol, without changing the PEEP level, was used during bronchoscopy. The physiological parameters were measured during the bronchoscopic procedure. RESULTS: During bronchoscopy, respiratory acidosis, elevation of peak pressure, elevation of heart rate and auto-PEEP were developed, but were reversible changes. Procedure-related gross barotraumas or other severe complications did not developed. CONCLUSION: No serious complications developed during bronchoscopy under our standardized mechanical ventilation protocol when the PEEP level remained unchanged. The procedure time should be kept to a minimum to decrease the exposure time to undesirable physiological changes.
Acidosis, Respiratory ; Anoxia ; Barotrauma ; Bronchoscopes ; Bronchoscopy* ; Heart Rate ; Humans ; Intensive Care Units ; Intubation, Intratracheal ; Positive-Pressure Respiration ; Positive-Pressure Respiration, Intrinsic ; Pulmonary Gas Exchange ; Respiration, Artificial ; Respiratory Mechanics

BACKGROUND: The effect of PEEP(ed note: Define PEEP.) on the lung volume in patients with auto-PEEP during mechanical ventilation is not even. In patients with an expiratory limitation such as COPD, a PEEP of 85% from an auto-PEEP can be used with minimal increase in the lung volume. However, the application of PEEP to patients without an expiratory flow limitation can result in progressive lung. This study was carried out to evaluate the different PEEP effects on the lung volume according to the different pulmonary diseases. METHODS: Sixteen patients who presented with auto-PEEP during mechanical ventilation were enrolled in this study. These patients were divided into 3 groups: asthma, COPD and tuberculosis sequela (patients with severe cicatrical fibrosis as a result of previous tuberculosis and compensatory emphysema). A PEEP of 25, 50, 75 and 100% of the auto-PEEP was applied, and the lung volume increments were estimated using the trapped lung volume. RESULTS: In the asthma group, the trapped lung volume was not increased at a PEEP of 25 and 50% of the auto-PEEP. This group showed a significant lung volume increment from a 75% PEEP. In the COPD group, the lung volume was increased only at 100% PEEP. In the tuberculosis sequela group, the lung volume was increased progressively from low PEEP levels. However, a significant increment of the lung volume was noted only at 100% PEEP. CONCLUSION: The effects of the applied PEEP on the lung volume were different depending on the underlying lung pathology. The level of the applied PEEP >50% of the auto-PEEP might increase the trapped lung volume in patients with asthma.
Asthma ; Fibrosis ; Humans ; Lung Diseases* ; Lung* ; Pathology ; Positive-Pressure Respiration, Intrinsic* ; Pulmonary Disease, Chronic Obstructive ; Respiration, Artificial ; Tuberculosis

BACKGROUND: Surgical resection of severely emphysematous lung tissue can significantly ameliorate shortness of breath, possibly by reducing dynamic airway compression and auto-PEEP. We utilized online spirometry to examine the intraoperative relationship between expiratory flow rate and compliance changes associated with a reduction pneumoplasty. METHODS: Eight surgical patients were anesthetized with IV propofol, isoflurane inhalation and thoracic epidural lidocaine/bupivacaine. A 37 or 39 left double lumen endobronchial tube (DLT) was placed and mechanical ventilation provided with tidal volume set at approximately 10 ml/kg. A Datex UltimaTM spirometer was placed at the proximal end of the DLT. Copies of flow/volume and pressure/volume curves (3 - 10 breaths) were obtained on a digital recorder during closed and open chest conditions, and before and after lung reduction. The mean +/- SD of expired tidal volume (VT), inspiratory plateau airway pressure (Pplat), respiratory rate, % of breath exhaled in 1 sec (V1.0%), and total dynamic compliance (CT) was measured. RESULTS: After a reduction pneumoplasty, CT decreased by an average 23% with open chest and 35% with closed chest conditions. Three subjects showed improved V1.0%, while 5 showed little change or reduced flow, hence no statistically significant change. There was no significant correlation between change in compliance and change in V1.0% (r2 = 0.24, p = 0.22). CONCLSIONS: An emphysematous reduction pneumoplasty reliably reduces lung compliance. However, reduced lung compliance did not reliably predict improved expiratory flow rates after a reduction pneumoplasty. The further reduction in CT with sternal closure may have been due to the return of dynamic airway compression.
Compliance ; Dyspnea ; Emphysema* ; Humans ; Inhalation ; Isoflurane ; Lung ; Lung Compliance ; Positive-Pressure Respiration, Intrinsic ; Propofol ; Respiration, Artificial ; Respiratory Rate ; Spirometry* ; Thorax ; Tidal Volume