The Lazarus Syndrome / 中华急诊医学杂志

The Lazarus phenomenon is defined as delayed ROSC,or ROSC after failure of CPR and cessation of all the emergency medical care,including the cessation of chest compression,mechanical ventilation,and venous fluid resuscitation.It was first reported in 1982 and 53 cases of Lazarus phenomenon have been reported in the medical literature so far.Even though Lazarus phenomenon is rare and the pathophysiological mechanisms are poorly understood,several possible mechanisms are still proposed,which could be rational to explain this phenomenon,such as auto-PEEP,hyperkalemia,alkalosis,delayed action of drugs,etc.In most cases,it was reported that ROSC occurred within 10 minutes after cessation of medical effort.Therefore,before the announcement of death of patient,it is mandatory to monitor those patients for at least 10 minutes after the cessation of CPR.However,more explicit studies seem to be necessary to gain a better understanding of this phenomenon.

Auto-PEEP-like condition recognized by a sudden decrease in airway pressure during pressure controlled ventilation and low-flow anesthesia: A case report

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.

Effects of upper airway obstruction on respiratory mechanics in a variable compliance model

BACKGROUND: Upper airway obstruction is caused by an intrinsic or extrinsic neck mass and vocal cord paralysis. A recognized hazard of prolonged endotracheal intubation is progressive airway occlusion resulting from deposition of secretions. If the obstruction persists, it may be life threatening condition. However, early diagnosis of partial airway obstruction is very difficult because patients are asymptomatic and do not have lesions with abnormal radiological characteristics. METHODS: In the test lung model, lung compliances were set to normal (25 ml/cmH2O; [control, C25 group]) and to levels seen in chronic obstructive pulmonary disease (40 ml/cmH2O; [C40 group]), and acute respiratory distress syndrome (20 ml/cmH2O; [C20 group] and 15 ml/cmH2O; [C15 group]). A ventilator (Drager Fabius GS, Germany) was attached to a test lung, and a series of endotracheal tubes (ETTs) ranging in size from 7.5 to 2.5 mm in inner diameter (ID) of the connector were used to simulate progressive occlusion. During the lung compliance and the connector size were changed, we measured some respiratory mechanics. RESULTS: Progressive ETT occlusion induced an increase in the peak inspiratory pressure. In the C40 group, the inspiratory pause pressure spontaneously increased on repeated ventilation. Auto- positive end-expiratory pressure (Auto-PEEP) was observed under the condition of high compliance and occlusion. Dynamic compliance decreased at an ID of 5.5 mm in all groups. Respiratory resistance was inversely proportional to the ID of the connector. CONCLUSIONS: The dynamic compliance and resistance were significantly changed. However the change of static compliance had little effect on respiratory mechanics.

Comparison of Auto-PEEP Levels Measured by End-expiratory Port Occlusion Method and Trapped Lung Volume / 대한구급학회지

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.

Different PEEP Effects on Lung Volume According to Underlying Lung Disease in Patients with Auto-PEEP / 결핵및호흡기질환

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.

Mechanical Ventilation in Patients with Chronic Obstructive Pulmonary Disease / 대한구급학회지

Patients with severe chronic obstructive pulmonary disease (COPD) may require mechanical ventilation following cardiac or general surgery, in connection with thoracic surgery such as lobectomy, wedge resection, lung reduction or bullectomy, during an episode of acute respiratory failure (ARF) secondary to a disease other than COPD such as sepsis, drug overdose, or trauma or for acute-on-chronic respiratory failure (the COPD exacerbation) where acute illness, usually presumed to be infectious in nature, destabilizes the characteristically compensated state. Ventilatory intervention is often life-saving when patients with asthma or COPD experience acute respiratory compromise. Although both noninvasive and invasive ventilation methods may be viable initial choice, which is better depends upon the severity of illness, the rapidity of response, coexisting disease, and capacity of the medical environment. In addition, noninvasive ventilation often relieves dyspnea and hypoxemia in patients with stable severe COPD. This review will only briefly cover noninvasive ventilation and focus primarily on the management of the intubated, mechanically ventilated patient with COPD, with particular emphasis on factors unique to this patient population such as the propensity for dynamic hyperinflation and auto-PEEP, barotrauma, difficult weaning and the prognosis following mechanical ventilation.

Measurement of Auto-PEEP in Anesthetized Patients Using a Laser-Flex Endotracheal Tube with Changes in Respiratory Rates and Tidal Volume / 대한마취과학회지

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.

The Effect of External PEEP on Work of Breathing in Patients with Auto-PEEP / 결핵

BACKGROUND: Auto-PEEP which develops when expiratory lung emptying is not finished until the beginning of next inspiration is frequently found in patients on mechanical ventilation. Its presence imposes increased risk of barotrauma and hypotension, as well as increased work of breathing (WOB) by adding inspiratory threshold load and/or adversely affecting to inspiratory trigger sensitivity. The aim of this study is to evaluate the relationship of auto-PEEP with WOB and to evaluate the effect of PEEP applied by ventilator (external PEEP) on WOB in patients with auto-PEEP. METHOD: 15 patients, who required mechanical ventilation for management of acute respiratory failure, were studied. First, the differences in WOB and other indices of respiratory mechanics were examined between 7 patients with auto-PEEP and 8 patients without auto-PEEP. Then, we applied the 3 cm H2O of external PEEP to patients with auto-PEEP and evaluated its effects on lung mechanics as well as WOB. Indices of respiratory mechanics including tidal volume (V(T)), repiratory rate, minute ventilation (V(E)), peak inspiratory flow rate (PIFR), peak expiratory flow rate (PEFR), peak inspiratory pressure (PIP), T(I)/T(TOT), auto-PEEP, dynamic compliance of lung (Cdyn), expiratory airway resistance (RAWe), mean airway resistance (RAWm), P(0.1), work of breathing performed by patient (WOB), and pressure-time product (PTP) were obtained by CP-100 Pulmonary Monitor (Bicore,USA). The values were expressed as meanSEM (standard error of mean). RESULTS: 1) Comparison of WOB and other indices of respiratory mechanics in patients with and without auto-PEEP: There was significant increase in WOB (1.71 +/-0.24 vs 0.500.19 J/L, p=0.007), PTP (317+/-70 vs 98+/-36 cm H2O * sec/min, p=0.023), RAWe (35.6+/-5.7 vs 18.2+/-2.3 cm H20/L/sec, p=0.023), RAWm (28.8+/-2.5 vs 11.9+/-2.0 cm H2O/L/sec, p=0.001) and P0.1 (6.21.0 vs 2.9+0.6 cm H2O, p=0.021) in patients with auto-PEEP compared to patients without auto-PEEP. The differences of other indices including V(T), PEFR, V(E) and T(I)/T(TOT) showed no significance. 2) Effect of 3 cm H2O external PEEP on respiratory mechanics in patients with auto-PEEP: When 3 cm H2O of external PEEP was applied, there were significant decrease in WOB (1.71+/-0.24 vs 1.20+/-0.21 J/L, p=0.021) and PTP (317+/-70 vs 231+/-55 cm H2O * sec/min, p=0.038). RAWm showed a tendency to decrease (28.8+/-2.5 vs 23.9+/-2.1 cm H2O, p=0.051). But PIP was increased with application of 3 cm H2O of external PEEP (16+/-2 vs 22+/-3 cm H2O, p=0.008). V(T), V(E), PEFR, T(I)/T(TOT) and Cdyn did not change significantly. CONCLUSION: The presence of auto-PEEP in mechanically ventilated patients was accompanied with increased WOB performed by patient, and this WOB was decreased by 3 cm H2O of externally applied PEEP. But, with 3 cm H2O of external PEEP, increased PIP was noted, implying the importance of close monitoring of the airway pressure during application of external PEEP.