Regional pulmonary pressure volume curves in mechanically ventilated patients with acute respiratory failure measured by electrical impedance tomography

BACKGROUND: We hypothesized, that in mechanically ventilated patients with acute respiratory failure, regional pressure volume curves differ markedly from conventional global pressure volume curves of the whole lung. METHODS: In nine mechanically ventilated patients with acute respiratory failure during an inspiratory low-flow manoeuvre, conventional global pressure volume curves were registered by spirometry and regional pressure volume curves in up to 912 regions were assessed simultaneously using electrical impedance tomography. We compared the lower (LIP) and upper (UIP) inflection points obtained from the conventional global pressure volume curve and regional pressure volume curves. RESULTS: We identified from the conventional global pressure volume curves LIP [3-11 (8) cmH2O] in eight patients and UIP [31-39 (33) cmH2O] in three patients. Using electrical impedance tomography (EIT), LIP [3-18 (8) cmH2O] in 54-264 (180) regions and UIP [23-42 (36) cmH2O] in 149-324 (193) regions (range and median) were identified. Lung mechanics measured by conventional global pressure volume curves are similar to the median of regional pressure volume curves obtained by EIT within the tomographic plane. However, single regional pressure volume curves differ markedly with a broad heterogeneity of lower and upper inflection points. CONCLUSION: Lower and upper inflection points obtained from conventional global pressure volume curves are not representative of all regions of the lungs.     

Pressure-volume relationships in acute lung injury: methodological and clinical implications

BACKGROUND: Pressure-volume relationships (PV curves) are the only available method for bedside monitoring of respiratory mechanics. Alveolar recruitment modifies the results obtained from the PV curves. We hypothesized that method-related differences may influence PV-curve guided ventilatory management. METHODS: Twelve acute lung injury (ALI) patients [PaO2/FiO2 13.0 +/- 1.5 kPa (97.6 +/- 11.3 mmHg), bilateral pulmonary infiltrates] were studied. Two PV curves [one at variable, and another at constant level of positive end-expiratory pressure (PEEP)] were obtained from each patient using constant inspiratory flow and end-inspiratory and -expiratory occlusions. Upper and lower inflection points (UIP, LIP) were estimated. Recruitment due to PEEP and during inflation was assessed by respiratory inductive plethysmography (RIP). RESULTS: (1) Pressure-volume curves at constant PEEP tended to provide higher LIP values compared with curves at variable PEEP (mean difference +/- SEM 5.1 +/- 1.9 cmH2O); and (2) recruitment occurred throughout the PV curve with no relationship with LIP or UIP. CONCLUSION: Pressure-volume curves obtained using variable PEEP translate a different physiological reality and seem to be clinically more relevant than curves constructed at constant PEEP. If curves constructed at constant PEEP are used to set the ventilator, unnecessarily high PEEP levels may be used. Respiratory inductive plethysmography technology may be used for monitoring of recruitment at the bedside.     

Expiratory flow-volume curves in mechanically ventilated patients with chronic obstructive pulmonary disease

BACKGROUND: Forced expiratory flow-volume curves are commonly used to assess the degree of airflow obstruction in patients with chronic obstructive pulmonary disease (COPD). In mechanically ventilated subjects, expiratory airways obstruction can only be estimated from relaxed expirations. The aim of this study was to quantify the degree of airways obstruction from relaxed expiratory flow-volume curves in mechanically ventilated patients with COPD. METHODS: As measure of airflow obstruction, the effective time constant during the last 50% of expired volume (tau) was calculated. For bedside monitoring, tau was recalculated as the slope of the flow during the last 50% of expired volume (SF50). In order to study reproducibility, the variables were calculated from consecutive breaths and at different levels of end-expiratory lung volume (EEV). The SF50 and the tau-were correlated with the forced expiratory volume in 1 s (FEV1) measured prior to the start of ventilatory support. RESULTS: Twenty-seven patients were studied with a FEV1 expressed as percentage predicted of 31 +/- 12% (mean +/- SD). The SF50 amounted to 19 +/- 10 degrees. A positive linear correlation was established between SF50 and the FEV1, (%pred), (r = 0.90, P < 0.0001). The tau showed an exponential relationship with FEV1 (%pred), (r2 = 0.78). From 5 consecutive breaths the mean variation coefficient of SF50 was 5 +/- 2%. Changes of delta EEV from 0.05 to 1.00 L did not affect the SF50-values. In 12 patients, mechanically ventilated for respiratory diseases other than COPD, mean tau and SF50 were significantly different from the COPD-patients (P < 0.0001). CONCLUSIONS: This study indicates that relaxed expiratory flow-volume curves can be used to assess airflow obstruction in mechanically ventilated patients with COPD. This information can be used to adapt ventilatory settings.     

Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgery

BACKGROUND: Morbidly obese patients have an increased risk for peri-operative lung complications and develop a decrease in functional residual capacity (FRC). Electric impedance tomography (EIT) can be used for continuous, fast-response measurement of lung volume changes. This method was used to optimize positive end-expiratory pressure (PEEP) to maintain FRC. METHODS: Fifteen patients with a body mass index of 49 +/- 8 kg/m(2) were studied during anaesthesia for laparoscopic gastric bypass surgery. Before induction, 16 electrodes were placed around the thorax to monitor ventilation-induced impedance changes. Calibration of the electric impedance tomograph against lung volume changes was made by increasing the tidal volume in steps of 200 ml. PEEP was titrated stepwise to maintain a horizontal baseline of the EIT curve, corresponding to a stable FRC. Absolute FRC was measured with a nitrogen wash-out/wash-in technique. Cardiac output was measured with an oesophageal Doppler method. Volume expanders, 1 +/- 0.5 l, were given to prevent PEEP-induced haemodynamic impairment. RESULTS: Impedance changes closely followed tidal volume changes (R(2) > 0.95). The optimal PEEP level was 15 +/- 1 cmH(2)O, and FRC at this PEEP level was 1706 +/- 447 ml before and 2210 +/- 540 ml after surgery (P < 0.01). The cardiac index increased significantly from 2.6 +/- 0.5 before to 3.1 +/- 0.8 l/min/m(2) after surgery, and the alveolar dead space decreased. P(a)O2/F(i)O2, shunt and compliance remained unchanged. CONCLUSION: EIT enables rapid assessment of lung volume changes in morbidly obese patients, and optimization of PEEP. High PEEP levels need to be used to maintain a normal FRC and to minimize shunt. Volume loading prevents circulatory depression in spite of a high PEEP level.     

Prone position in mechanically ventilated patients with reduced intracranial compliance

BACKGROUND: Prone position has been used for several years to treat acute lung insufficiency, but in previous studies patients with unstable intracranial pressure (ICP) are mostly excluded. The aim of this study was to investigate if prone position is a safe and useful treatment in patients with reduced intracranial compliance. METHODS: A consecutive, prospective pilot study of 11 patients admitted to the neuro intensive care unit (NICU) due to traumatic brain injury or intracerebral haemorrhage. ICP, cerebral perfusion pressure (CPP), heart rate (HR), mean arterial blood pressure (MABP), arterial partial pressure of oxygen (PaO(2)), arterial partial pressure of carbon dioxide (PaCO(2)), arterial oxygen saturation (SaO(2)) and respiratory system compliance were measured before, three times during and two times after the patients were placed in the prone position. RESULTS: No significant changes were demonstrated in ICP, CPP or MABP. PaO(2) and SaO(2) were significantly increased in the prone position. HR was significantly increased in the prone position and after 10 min in the supine post-prone position and the respiratory system compliance was increased after 1 h in the supine post-prone position. CONCLUSION: Turning NICU patients from the supine to the prone position did not influence ICP, CPP or MABP, but significantly improved patient PaO(2), SaO(2) and respiratory system compliance.     

Maximal hysteresis: a new method to set positive end‐expiratory pressure in acute lung injury?

Background: No methods are superior when setting positive end-expiratory pressure (PEEP) in acute lung injury (ALI). In ALI, the vertical distance (hysteresis) between the inspiratory and expiratory limbs of a static pressure–volume (PV) loop mainly indicates lung recruitment. We hypothesized that PEEP set at the pressure where hysteresis is 90% of its maximum (90%MH) would give similar oxygenation, but less cardiovascular depression than PEEP set at the pressure at lower inflection point (LIP) on the inspiratory limb or at the point of maximal curvature (PMC) on the expiratory limb in ALI.
Methods: In 12 mechanically ventilated pigs, ALI was induced in a randomized fashion by lung lavage, lung lavage plus injurious ventilation, or by oleic acid. From a static PV loop obtained by an interrupted low-flow method, the pressures at LIP [25 (25, 25) cmH₂O, mean and 25, 75 percentiles], at PMC [24 (20, 24) cmH₂O], and at 90% MH [19 (18, 19) cmH₂O] were determined and used for the PEEP-settings. We measured lung inflation (by computed tomography), end-expiratory lung volume (EELV), airway pressures, compliance of the respiratory system (Crs), blood gases, cardiac output and arterial blood pressure.
Results: There were no differences between the PEEP settings in EELV or oxygenation, but the 90%MH setting gave lower end-inspiratory pause pressure ( P <0.025), higher Crs ( P <0.025), less hyper-aeration ( P <0.025) and better maintained hemodynamics.
Conclusion: In this porcine lung injury model, PEEP set at 90% MH gave better lung mechanics and hemodynamics, than PEEP set at PMC or LIP.     

Evaluation of a recruitment maneuver with positive inspiratory pressure and high PEEP in patients with severe ARDS

BACKGROUND: To evaluate the effect of a recruitment maneuver (RM) with constant positive inspiratory pressure and high positive end-expiratory pressure (PEEP) on oxygenation and static compliance (Cs) in patients with severe acute respiratory distress syndrome (ARDS). METHODS: Eight patients with ARDS ventilated with lung-protective strategy and an arterial partial pressure of oxygen to inspired oxygen fraction ratio (PaO2/FIO2) < or =100 mmHg regardless of PEEP were prospectively studied. The RM was performed in pressure-controlled ventilation at FIO2 of 1.0 until PaO2 reached 250 mmHg or a maximal plateau pressure/PEEP of 60/45 cmH2O was achieved. The RM was performed with stepwise increases of 5 cmH2O of PEEP every 2 min and thereafter with stepwise decreases of 2 cmH2O of PEEP every 2 min until a drop in PaO2 >10% below the recruitment PEEP level. Data was collected before (preRM), during and after 30 min (posRM). RESULTS: The PaO2/FIO2 increased from 83 +/- 22 mmHg preRM to 118 +/- 32 mmHg posRM (P = 0.001). The Cs increased from 28 +/- 10 ml cmH2O(-1) preRM to 35 +/- 12 ml cmH2O(-1) posRM (P = 0.025). The PEEP was 12 +/- 3 cmH2O preRM and was set at 15 +/- 4 cmH2O posRM (P = 0.025). The PEEP of recruitment was 36 +/- 9 cmH2O and the collapsing PEEP was 13 +/- 4 cmH2O. The PaO2 of recruitment was 225 +/- 105 mmHg, with five patients reaching a PaO2 > or = 250 mmHg. The FIO2 decreased from 0.76 +/- 0.16 preRM to 0.63 +/- 0.15 posRM (P = 0.001). No major complications were detected. CONCLUSION: Recruitment maneuver was safe and useful to improve oxygenation and Cs in patients with severe ARDS ventilated with lung-protective strategy.     

Resistive load of laryngeal mask airway and ProSeal laryngeal mask airway in mechanically ventilated patients

BACKGROUND: The ProSeal Laryngeal Mask Airway (PLMA) ventilation tube is narrower and shorter than the standard Laryngeal Mask Airway (LMA) and is without the vertical bars at the end of the tube. In this randomized, crossover study, PLMA and LMA resistances were compared. METHODS: Respiratory mechanics was calculated in 26 anesthetized, mechanically ventilated patients with both LMA and PLMA. The laryngeal mask positioning was fiberoptically evaluated. Differences in the respiratory mechanics of the LMA and the PLMA were attributed to the differences between the laryngeal masks. RESULTS: In the total study population the airway resistance was 1.5 +/- 2.6 hPa.l-1.s-1 (P = 0.005) higher with the PLMA than with the LMA. During the PLMA use, the peak expiratory flow reduced by 0.02 +/- 0.05 l min-1 (P = 0.046), the expiratory resistance increased by 0.6 +/- 1.3 hPa.l-1.s-1 (P = 0.022), and the time constant of respiratory system lengthened by 0.09 +/- 0.18 s (P = 0.023). These differences doubled when the LMA was better positioned than the PLMA, whereas they disappeared when the PLMA was positioned better than the LMA. CONCLUSIONS: The standard LMA offers a lower resistive load than the PLMA. Moreover, the fitting between the laryngeal masks and the larynx, as fiberoptically evaluated, plays a major role in determining the resistive properties of these devices.     

Propofol induces bronchodilation in mechanically ventilated chronic obstructive pulmonary disease (COPD) patients

The aim of this study was to evaluate the effects of propofol administration (2 mg · kg^-1 i.v.) on the airways resistances and respiratory mechanics of patients affected by COPD exacerbation, requiring mechanical ventilation. Twenty patients required anaesthesia for diagnostic or therapeutic procedures. Fourteen consecutive patients were divided at random into two groups: Group P received propofol and Group C (control) received only Intralipid 10%; an additional group of six patients received i.v. flunitrazepam (0.03 mg · kg^-1). Lung mechanics (dynamic and static compliance, peak inspiratory pressure, intrinsic positive and expiratory pressure, minimal and maximal resistances of the respiratory system) were evaluated in basal conditions and 3 and 6 min after propofol, Intralipid or flunitrazepam administration. We did not observe significant variations of the evaluated variables after Intralipid or flunitrazepam (Groups C and F), while in patients who received propofol (Group P), we observed the following modifications: dynamic compliance increased from 2.3 ± 0.3 to 2.8 ± 0.4 ml · kPa^-1 (P<0.05), peak inspiratory pressure decreased from 3.3 ± 0.7 to 2.8 ± 0.4 kPa (P <0.05), minimal resistances of the respiratory system (that mainly reflect airways resistances) decreased from 1 ± 0.2 to 0.7 ± 0.2 kPa · 1^-1 · s^-1 (P <0.01). Our results suggest that propofol induces bronchodilation in mechanically ventilated COPD patients, and that this effect is not related specifically to the induction of general anesthesia.     

Effects of PEEP on extra vascular lung water and central blood volume in the dog

Twenty-four mongrel dogs were anaesthetized and ventilated mechanically in the supine position. Extravascular lung water (EVLW) and central blood volume (CBV) were measured with a double indicator (dye/cold) dilution technique. Both indicators were detected intravascularly in the aortic root with a fibreoptic thermistor catheter. Seven dogs ventilated with a positive end-expiratory pressure (PEEP) of 1.0 kPa (10 cmH2O) for a short period of time (less than 20 min) displayed no significant change in EVLW as measured with the indicator dilution technique (= EVLWi), while reductions were seen in both CBV (15%, P less than 0.01) and cardiac output (CO-thermodilution technique) (10%, P less than 0.05). Another seven dogs ventilated with a PEEP of 1.0 kPa for 8 h showed a gradual increase in EVLWi. After 8 h, a mean increase of 34% (P less than 0.01) was recorded, and the increase was also verified by post-mortem gravimetric determination of EVLW (= EVLWg), displaying an increase of 61% (P less than 0.01). In five dogs ventilated with zero end-expiratory pressure (ZEEP) for 8 h, no changes in EVLWi, CO, and CBV were observed, and EVLWg was mean 4.39 g/kg body weight (BW). Five additional dogs were sacrificed after 15 min of anaesthesia without catheterization and EVLWg was found to be 4.24 g/kg BW. It is concluded that EVLWi does not change measurably during ZEEP or short periods of PEEP. However, long periods (8 h) of PEEP result in elevated EVLWi values. Gravimetry supports these conclusions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Delayed derecruitment after removal of PEEP in patients with acute lung injury

Background: A step decrease in positive end-expiratory airway pressure (PEEP) is not followed by an instantaneous loss of the PEEP-induced increase in end-expiratory lung volume (EELV). Rather, the reduction of EELV is delayed, while adverse PEEP effects on hemodynamics are immediately attenuated upon the drop in airway pressure. Step PEEP increments were applied to the lungs of patients with acute lung injury. It was investigated retrospectively whether enlargement of end-expiratory lung volume and changes in lung mechanics persist 45 min after removal of the PEEP increment.
Methods: In 14 patients with acute lung injury (LIS score 2.7) EELV and volume-dependent dynamic compliance of the respiratory system (C_dyn,rs) were determined 45 min after removal of an additional PEEP increment (0.64 kPa added to baseline PEEP of 1.0 kPa).
Results: Nine patients kept an EELV gain of 13% (SD 7) and showed improved C_dyn,rs. In 5 patients, EELV was reduced (by 9% (SD 6)) and C_dyn,rs unchanged after removal of the PEEP increment compared to baseline.
Conclusion: A subgroup of patients with acute lung injury, the characteristics of which remain to be defined, benefit from prolonged recruitment effects up to 45 min after removal of a PEEP increment, while sequelae of continuously increased airway pressures are minimised.     

个体化呼气末正压通气对肥胖患者腹腔镜胃减容术后肺部并发症的影响

目的 研究个体化呼气末正压（PEEP）通气策略对肥胖患者腹腔镜胃减容术后肺部并发症（PPCs）的影响。
方法 选择行全身麻醉腹腔镜胃减容术的成年肥胖患者40例,男15例,女25例,年龄18～44岁,BMI 35～55 kg/m²,ASA Ⅱ或Ⅲ级。采用随机数字表法分为两组：个体化PEEP组（I组）和固定PEEP组（C组）,每组20例。I组在诱导插管后依据肺动态顺应性（Cdyn）个体化滴定最佳PEEP并维持此PEEP进行术中通气,C组以PEEP 8 cmH2O进行术中通气。记录插管后5 min、气腹后1 h的氧合指数、分流率以及气道峰压、气道平台压、驱动压、Cdyn等呼吸力学参数,记录术中低血压发生情况、输液量、血管活性药用量、机械通气时间和术后住院时间,记录术后第1天、第2天、第3天、第8天PPCs的发生情况以及术后8 d内PPCs累积发生率。
结果 I组PPCs累积发生率明显低于C组 ［13例（65%） vs 19例（95%）, P＜0.05］。气腹后1 h 时I组氧合指数、气道峰压、气道平台压、Cdyn均明显高于C组（P<0.05）,I组驱动压明显低于C组（P<0.05）。两组术中低血压发生率、输液量、去氧肾上腺素用量、机械通气时间和术后住院时间差异无统计学意义。
结论 个体化PEEP能够降低腹腔镜胃减容术患者PPCs发生率,并在不影响血流动力学稳定性的同时降低术中驱动压,改善氧合。     

Selective PEEP in Acute Bilateral Lung Disease. Effect on Patients in the Lateral Posture

Seven patients with acute respiratory failure due to diffuse and fairly uniform lung disease were studied during mechanical ventilation in the lateral decubital position with: (a) zero end-expiratory pressure (ZEEP) through a double-lumen oro-bronchial tube to permit a recording of the ventilation to each lung; (b) bilateral positive end-expiratory pressure (PEEP) of 1.2 kPa, with maintenance of ventilation distribution between lungs as observed during ZEEP; (c) selective PEEP of 1.2 kPa, applied to the dependent lung only, with ventilation as during ZEEP; and (d) conventional PEEP of 1.2 kPa applied to both lungs through a single-lumen tube, with free distribution of ventilation between the lungs. During ZEEP, 69% of ventilation was distributed to the non-dependent and 31% to the dependent lung; cardiac output was 6.51 X min-1, venous admixture (QS/QT) 40% and arterial oxygen tension (PaO2) 8.3 kPa. With bilateral PEEP, functional residual capacity (FRC) increased by 0.331, cardiac output was reduced to 5.11 X min-1 and venous admixture to 32%. PaO2 increased to 10.1 kPa. With selective PEEP the dependent lung FRC increased by 0.211 and the FRC of the non-dependent lung decreased by 0.081. Cardiac output increased to 6.11 X min-1, which was no longer significantly different from that during ZEEP. Venous admixture remained at the same level as with bilateral PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pulmonary effects of body position, PEEP, and surfactant depletion in dogs

The influence of position (sphinx, lateral, supine), surfactant depletion, and different positive end-expiratory pressure (PEEP) on functional residual capacity (FRC), series dead space (VdS) and compliance of the respiratory system (Crs) were evaluated in five dogs. Ventilation homogeneity as measured by an index (multiple breath alveolar mixing efficiency), oxygenation, and cardiovascular hemodynamics were additionally examined. The dogs were anesthetized with halothane, paralyzed, and mechanically ventilated. FRC and VdS were found to be notably large in dogs, 45 +/- 8 ml/kg and 6 +/- 1 ml/kg, respectively. FRC and ventilation homogeneity were improved in the sphinx position (prone position with upright head). Surfactant depletion by lung lavage with 37 degrees C saline caused an immediate and stable decrease in FRC, Crs, and oxygenation (P less than 0.05, respectively) for about 5 h without marked effects on the circulatory system. FRC and VdS increased with increasing PEEP. At the highest PEEP, 10 cmH2O (1 kPa), Crs decreased (P less than 0.05) and ventilation became more uneven, indicating alveolar overdistension.     

Intraoperative changes in arterial oxygenation during volume-controlled mechanical ventilation in modestly obese patients undergoing laparotomies with general anesthesia

BACKGROUND: In obese patients, arterial oxygenation can be greatly impaired during general anesthesia. Both avoidance of denitrogenation and application of positive end-expiratory pressure (PEEP) during mechanical ventilation may be effective in preventing such impairment of arterial oxygenation. METHODS: We studied 28 obese/overweight and seven non-obese (BMI < 25 kg x m-2) patients who underwent laparotomies with general anesthesia (i.e. isoflurane with or without nitrous oxide). During anesthesia, their lungs were mechanically ventilated at a rate of 10 breaths x min-1 with a constant flow, inspiratory-to-expiratory ratio 1 : 2, and tidal volume approximately 10 ml x kg-1. The obese/overweight patients were allocated to four different groups in terms of denitrogenation and application of PEEP (7 cm H2O) during the ventilation (n = 7 each). In the non-obese patients, their denitrogenated lungs were ventilated without application of PEEP. Arterial gas analyses were performed before induction of anesthesia, and 30, 90, 150 and 210 min after tracheal intubation. The ratio of PaO2 to FiO2 was calculated as an index of arterial oxygenation. RESULTS: No significant changes in the PaO2/FiO2 ratio were observed throughout the study in the non-obese patients and in the obese/overweight patients whose non-denitrogenated lungs were ventilated with PEEP. In the obese/overweight patients whose lungs were ventilated after denitrogenation or without application of PEEP, significant decreases in the PaO2/FiO2 ratio were observed 30 and 90 min after tracheal intubation. CONCLUSIONS: In obese or overweight patients under general anesthesia, it may be advisable to avoid denitrogenation and apply PEEP during mechanical ventilation in order to minimize the impairment of arterial oxygenation.     

Respiratory and haemodynamic effects of conventional volume controlled PEEP ventilation, pressure regulated volume controlled ventilation and low frequency positive pressure ventilation with extracorporeal carbon dioxide removal in pigs with acute ARDS

The purpose of this study was to evaluate whether any benefit of low frequency positive pressure ventilation with extracorporeal carbon dioxide removal (LFPPV–ECCO₂R) existed over either volume controlled ventilation (VCV) with measured best–PEEP or pressure regulated volume controlled ventilation (PRVCV) with an inspiration/expiration (I/E) ratio of 4:1, with respect to arterial oxygenation, lung mechanics and haemodynamics, in acute respiratory failure.
Fifteen adult pigs were used for the study. Respiratory failure was induced by surfactant depletion by repeated lung lavage. The different therapeutic approaches were applied randomly to each pig for 1 h. Measurements of gas exchange, airway pressures and haemodynamics were performed during ventilatory and haemodynamic steady state. Paco₂ was kept constant in all modes.
At almost similar total–PEEP, Pao₂ values were significantly higher with LFPPV–ECCO₂R comared to VCV with best–PEEP. Peak inspiratory pressure (PIP) and intrapulmonary pressure amplitude defined as the difference between PIP and total–PEEP were significantly lower with PRVCV and LFPPV–ECCO₂R compared to VCV with best–PEEP. There was no significant difference between the modes concerning cardiocircu–latory parameters.
PRVCV with I/E ratio of 4:1 and LFPPV–ECCO₂R proved to be better modes to achieve better gas exchange and lower PIP at lower intrapulmonary pressure amplitudes. It is concluded that PRVCV is an adequate form of treatment under these experimental conditions imitating acute respiratory failure, without necessitating other invasive measures.     

两种气囊测压法预防机械通气患者呼吸机相关性肺炎效果比较

目的 比较持续测压与间断测压对预防机械通气患者呼吸机相关性肺炎的临床效果,为人工气道气囊管理提供依据。 方法 将134例机械通气患者随机均分为间断测压组和持续测压组。间断测压组使用气囊测压表采用改进方法分别间隔4 h、6 h、8 h监测1次气囊压力;持续测压组采用持续测压仪持续测压。比较两组呼吸机相关性肺炎发生率、机械通气时间、ICU住院时间、气囊上滞留物引流量、抗生素使用种类及时间、炎性指标。 结果 两组呼吸机相关性肺炎发生率、机械通气时间、ICU住院时间、抗生素使用种类及时间比较,差异无统计学意义（均P＞0.05）。两组入科第1天、第3天、第7天白细胞、C反应蛋白、降钙素原及24 h气囊上滞留物引流量比较,差异无统计学意义（均P＞0.05）。持续测压组检测值25～30 cmH2O;间断测压组间隔4 h、6 h、8 h检测气囊压力,差异有统计学意义（P＜0.05）,间隔8 h检测气囊压力＜25 cmH2O。 结论 两种测压方法对患者呼吸机相关性肺炎发生率、机械通气时间、ICU住院时间、抗生素应用的影响没有显著差异,提示锥形气囊导管应用两种测压方法可达到相同的临床效果,间断测压间隔时间以≤6 h为宜。