全麻气管插管后七氟醚和异氟醚吸入对吸烟患者呼吸力学的影响

目的 比较观察全麻气管插管后七氟醚和异氟醚吸入对吸烟和非吸烟患者气道阻力、肺顺应性和气道峰压的影响.方法 选择既往有和无吸烟史择期手术的普通外科患者80例[美国麻醉医师协会(ASA)Ⅰ～Ⅱ级,既往有或无吸烟史患者各40例],随机分为4组(n=20):有吸烟史患者吸入七氟醚全麻组(SS组)和吸入异氟醚全麻组(SI组),无吸烟史患者吸入七氟醚全麻组(NS组)和吸入异氟醚全麻组(NI组).使用多功能麻醉气体监护仪监测患者吸入麻醉剂浓度达到肺泡最低有效浓度(1MAC)后4、8、12、16min的气道峰压、肺顺应性,同时用无创心功能测定仪监测气道阻力,记录各组患者在吸入麻醉剂期间各项指标的变化情况.结果 与吸入前相比,所有接受全麻气管插管的患者在使用七氟醚和异氟醚吸入维持4、8、12、16 min后均出现气道阻力和气道峰压的明显下降(均P＜0.05),其中SS组和NS组8min后下降趋于稳定[气道阻力:SS组(10.38±1.12)cmH2O·L-1·s-1,NS组(9.65±1.04)cm H2O·L-1·s-1;气道峰压:SS组(13.52±1.01)cm H2O,NS组(12.86±0.94)cm H2O,1 cm H2O=0.098kPa],SI组和NI组则于12 min后下降趋于稳定[气道阻力:SI组(10.30±0.98)cm H2O·L-1·s-1,NI组(11.00±0.73)cm H2O·L-1·s-1;气道峰压:SI组(13.47±0.88)cm H2O,NI组(12.85±0.65)cm H2O],同时间点的非吸烟组下降幅度高于吸烟组(均P＜0.05).4组患者在使用七氟醚和异氟醚吸入维持后其肺顺应性较吸入前均无明显变化(均P＞0.05),同时间点的非吸烟组与吸烟组相比肺顺应性差异也没有统计学意义(均P＞0.05).结论 全麻气管插管后七氟醚和异氟醚吸入使患者的气道阻力和气道峰压出现明显下降,吸烟者比非吸烟者下降程度低.     

不同压力及时间机械通气对大鼠血清白细胞介素8、白细胞介素10水平和肺组织形态学的影响

目的 探讨不同压力及时间机械通气对大鼠血清白细胞介素8(IL-8)、IL-10水平及肺组织形态学的影响.方法 成年雄性SD大鼠30只,随机分为空白对照组(C组)、低气道压力2 h组[L2组,压力为15 cm H2O(1 cm H2O=0.098 kPa),通气时间为2 h]、低气道压力4 h组(L4组,压力为15 cmH2O,通气时间为4 h)和高气道压力2 h组(H2组,压力为25 cm H2O,通气时间为2 h)、高气道压力4 h组(H4组,压力为25 cm H2O,通气时间为4 h),每组6只.连接呼吸机,设定呼吸频率为40次/min,按既定压力及时间进行机械通气,分别于机械通气2、4 h后血处死大鼠,检测血清中IL-8、IL-10的含量,并取肺组织,光镜及电镜下观察组织损伤的病理改变.结果 与C组相比,L2、L4、H2、H4组血清中IL-8、IL-10的含量均明显增加,且随通气时间的延长而升高,L4组高于L2组[IL-8:(71.5±7.6)ng/L比(38.4±6.3)ng,L,IL-10:(364.5±18.6)ng/L比(271.6±21.3)ng/L,P<0.05],H4组高于H2组[IL-8:(140.7±23.5)ng/L比(76.4±9.2)ng/L,IL-10:(472.8±22.5)ng/L比(357.6±20.4)ng/L,P<0.05];相同通气时间下,高气道压力组血清中IL-8、IL-10的含量较低气道压力组明显增多,H2组高于L2组,H4组高于L4组(P<0.05).光镜及电镜下组织学检查显示与C组比较,其余各组肺组织均出现不同程度的炎性细胞浸润、肺气肿、线粒体肿胀、内质网扩张、细胞核质间隙增宽等炎性反应改变,且随时问及气道压力的增加而加重.结论 通气压力及时间的增加能够刺激大鼠血清中炎性反应因子IL-8、IL-10水平的升高,加重肺组织的损伤.有效控制通气的压力及时间可以减轻肺组织炎性反应和损伤.     

Effects of mechanical load on flow, volume and pressure delivered by high-frequency percussive ventilation

High-frequency percussive ventilation (HFPV) has proved its unique efficacy in the treatment of acute respiratory distress, when conventional mechanical ventilation (CMV) has demonstrated a limited response. We analysed flow (V(dot)), volume (V) and airway pressure (Paw) during ventilation of a single-compartment mechanical lung simulator, in which resistance (R) and elastance (E) values were modified, while maintaining the selected ventilatory settings of the HFPV device. These signals reveal the physical effect of the imposed loads on the output of the ventilatory device, secondary to constant (millisecond by millisecond) alterations in pulmonary dynamics. V(dot), V and Paw values depended fundamentally on the value of R, but their shapes were modified by R and E. Although peak Paw increased 70.3% in relation to control value, mean Paw augmented solely 36.5% under the same circumstances (maximum of 9.4 cm H2O). Finally, a mechanism for washing gas out of the lung was suggested.     

Pressure controlled inverse ratio ventilation in acute respiratory distress syndrome patients

Appropriate ventilatory intervention is life saving in acute respiratory distress syndrome (ARDS). Pressure controlled inverse ratio ventilation (PC-IRV) is the likely mode of ventilation benefiting in extreme conditions of ARDS. However, guidelines when to start PC-IRV is not yet well defined. The ventilation-related dilemma, which we faced in two illustrative cases of ARDS are presented. The first patient presenting clinically with ARDS but with high peak airway pressure (PIP) and low dynamic lung compliance, PC-IRV helped in reducing PIP, improved haemodynamics and the oxygenation of blood. In second patient with similar clinical presentation of ARDS, where although PIP was high but the dynamic compliance was better, the PC-IRV caused deterioration in PaO2. Here, patient rather did better with high PEEP (15 cm H2O) and usual I: E ratio (1:2). It is probable that the dynamic lung compliance (< 20ml/cmH2O), PIP (> 50 cm H2O) at conventional I: E ratio (1:2) ventilation (10 ml/kg) with hypotension might form the basis to develop a scoring system for guidance to switch over to PC-IRV ventilation. Further randomised prospective controlled clinical trials will then be required to establish indication to start PC-IRV in ARDS.     

Auto-adjusting versus fixed positive pressure therapy in mild to moderate obstructive sleep apnoea

STUDY OBJECTIVES: To determine if auto-adjusting positive airway pressure (APAP) would be better tolerated on the basis of delivering a lower mean pressure in patients with mild to moderate obstructive sleep apnoea syndrome (OSAS). DESIGN: Patients spent 8 weeks on continuous positive airway pressure (CPAP) and 8 weeks on APAP in a randomized crossover design. SETTING: Respiratory Sleep Disorders Unit in a University Hospital and the patient's home. PARTICIPANTS: Twenty-nine patients with newly diagnosed mild to moderate OSAS (apnoea-hypopnoea frequency of 5-30 events/hour) were studied. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Overnight polysomnography and Epworth Sleepiness Scale were recorded at baseline and at the end of each treatment period in addition to patient preference for device, side effects, and objective compliance. No differences were found in polysomnographic variables or Epworth Sleepiness Scale scores between the 2 treatment modes, but all variables were significantly improved from baseline values. Mean APAP pressure levels were significantly lower than CPAP (6.3 +/- 1.4 vs 8.1 +/- 1.7 cm H2O, p < .001). Patient compliance was similar with both treatments. More patients requiring higher fixed pressure (> or = 8cm H2O) preferred APAP, whereas those requiring lower pressure (< 8 cm H2O) preferred CPAP (p = .03). Follow-up after 18 months of therapy indicated that 76% of subjects continued to be compliant, with a nightly use of 5.8 +/- 1.9 hours per night, despite high levels of minor side effects. CONCLUSIONS: APAP and CPAP are equally effective in managing patients with mild to moderate OSAS, but device preference may be influenced by fixed pressure requirements.     

不同压力及时间机械通气对大鼠血清白细胞介素8、白细胞介素10水平和肺组织形态学的影响

目的 探讨不同压力及时间机械通气对大鼠血清白细胞介素8（IL-8）、IL-10水平及肺组织形态学的影响.方法 成年雄性SD大鼠30只,随机分为空白对照组（C组）、低气道压力2 h组[L2组,压力为15 cm H2O（1 cm H2O=0.098 kPa）,通气时间为2 h]、低气道压力4 h组（L4组,压力为15 cmH2O,通气时间为4 h）和高气道压力2 h组（H2组,压力为25 cm H2O,通气时间为2 h）、高气道压力4 h组（H4组,压力为25 cm H2O,通气时间为4 h）,每组6只.连接呼吸机,设定呼吸频率为40次/min,按既定压力及时间进行机械通气,分别于机械通气2、4 h后血处死大鼠,检测血清中IL-8、IL-10的含量,并取肺组织,光镜及电镜下观察组织损伤的病理改变.结果 与C组相比,L2、L4、H2、H4组血清中IL-8、IL-10的含量均明显增加,且随通气时间的延长而升高,L4组高于L2组[IL-8：（71.5±7.6）ng/L比（38.4±6.3）ng,L,IL-10：（364.5±18.6）ng/L比（271.6±21.3）ng/L,P〈0.05],H4组高于H2组[IL-8：（140.7±23.5）ng/L比（76.4±9.2）ng/L,IL-10：（472.8±22.5）ng/L比（357.6±20.4）ng/L,P〈0.05];相同通气时间下,高气道压力组血清中IL-8、IL-10的含量较低气道压力组明显增多,H2组高于L2组,H4组高于L4组（P〈0.05）.光镜及电镜下组织学检查显示与C组比较,其余各组肺组织均出现不同程度的炎性细胞浸润、肺气肿、线粒体肿胀、内质网扩张、细胞核质间隙增宽等炎性反应改变,且随时问及气道压力的增加而加重.结论 通气压力及时间的增加能够刺激大鼠血清中炎性反应因子IL-8、IL-10水平的升高,加重肺组织的损伤.有效控制通气的压力及时间可以减轻肺组织炎性反应和损伤.     

Chemoreflex control of ventilation is altered during wakefulness in humans with OSA

We hypothesized that patients with obstructive sleep apnea (OSA) have a different awake ventilatory response to carbon dioxide above and below eupnea compared with normal. Eight male subjects with OSA and control subjects matched for gender, race, age, height and weight voluntarily hyperventilated during wakefulness to reduce the partial pressure of carbon dioxide (PET(CO2)) below 25 mmHg. Subjects were then switched into a rebreathing bag containing a normocapnic (42 mmHg) hypoxic [partial pressure of end tidal oxygen (PET(O2))=50 mmHg (H50)] or hyperoxic [PET(O2)=140 mmHg (H140)] gas mixture. During the trial PET(CO2) increased while PET(O2) was maintained at a constant level. The point at which ventilation and PET(CO2) increased linearly was considered to be the carbon dioxide ventilatory recruitment threshold (VRT(CO2)). Measurements of ventilation and its components (i.e. tidal volume and breathing frequency) were made below this threshold and the slope of the minute ventilation; tidal volume or breathing frequency response above the threshold was determined. Four trials for a given oxygen level were completed. The PET(CO2) that demarcated the VRT(CO2) was increased (H(50)=43.43+/-0.92 vs. 41.05+/-0.67; H(140)=47.65+/-0.80 vs. 45.28+/-0.75), as were measures of ventilation below the threshold (H(50)=18.50+/-2.11 vs. 13.44+/-1.43; H(140)=19.66+/-2.71 vs. 10.83+/-1.24) in the OSA subjects compared with control. In contrast the OSA and control subjects did not respond differently to changes in PET(CO2) above the threshold. We conclude that the PET(CO2) that delineates the VRT(CO2) and ventilation below this threshold is elevated in subjects with OSA.     

双水平气道正压无创通气全身麻醉期间患者胃内压及咽后部pH值的变化

目的 通过对双水平正压无创通气全身麻醉患者行连续胃内压监测,探讨该通气模式引起胃内容物反流的可能机制.方法 选择行腹腔镜胆囊切除手术的成年患者60例随机分为2组:双水平气道正压(BiPAP)面罩通气组(Ⅰ组)和气管内捕管气道正压通气(IPPV)组(Ⅱ组),每组30例.麻醉前将测压管送达胃内,观察麻醉前、麻醉后30 min、气腹后30 min、拔管或撤离通气后30 min的循环、血气指标、胃内压及咽部pH值.结果 麻醉通气期间2组MAP、HR尚平稳,拔管后30min Ⅱ组PaO_2低于麻醉前水平[(78±14.1)mm Hg 比(85±10.4)mm Hg,P<0.05,1 mm Hg=0.133 kPa],而Ⅰ组前后差异无统计学意义(P>0.05).Ⅰ组麻醉后30min胃内压比麻醉前明显下降[(7.2±2.6)cm H_2O比(8.0±3.2)cm H_2O,P<0.05,1 cm H_2O=0.098 kPa],而Ⅱ组升高[(9.6±2.3)cm H_2O比(7.8±4.5)cm H_2O,P<0.05].气腹后30 min 2组胃内压骤升,Ⅱ组比Ⅰ组更高[(23±5.3)cm H_2O比(20±4.1)cm H_2O,P<0.05),Ⅱ组拔管后30 min仍较麻醉前高[(11.8±4.6)cm H_2O比(7.8±4.5)cm H_2O,P<0.05],且比Ⅰ组术后胃内压[(8.3±4.1)cm H_2O]明显增高(P<0.05).麻醉前和拔管后,2组咽部pH值差异无统计学意义(p>0.05).结论 双水平气道正压面罩通气能安全有效地维持全身麻醉时进行的机械通气,对围麻醉期的生理干扰较少.在腹腔镜胆囊切除术时胃内压变化剧烈,双水平气道正压面罩通气的胃内压升高幅度较小,导致胃食管反流的风险较低.     

Tracheal traction effects on upper airway patency in rabbits: the role of tissue pressure

STUDY OBJECTIVES: To investigate the mechanisms via which lung volume related caudal tracheal traction decreases upper airway collapsibility. DESIGN: Acute physiological study. PARTICIPANTS: 20 male, supine, anesthetised, tracheostomised, spontaneously breathing, NZ white rabbits fitted with a sealed face mask. SETTING: N/A. MEASUREMENTS AND RESULTS: Upper airway extraluminal tissue pressure (ETP) was measured in the lateral (ETPlat) and anterior (ETPant) pharyngeal walls (pressure transducer tipped catheters). Graded traction was applied to the isolated upper airway (n = 17, 0-140 g). Subsequently, inflation and deflation was performed (with and without traction, 48 g, n = 13) with measurement of intraluminal pressure. Upper airway transmural pressure (PTM) was calculated (at closure and reopening) for both ETP sites (PTMlat and PTMant, respectively). A traction force of 144 g decreased ETPlat from 2.6 +/- 0.7 cm H2O (mean +/- SEM) to 2.1 +/- 0.7 cm H2O and ETPant from 1.1 +/- 0.4 cm H2O to 0.8 +/- 0.4 cm H2O (both P < 0.001). Increasing traction decreased closing and reopening pressures by 1.4 +/- 0.2 cm H2O for 48 g of traction (n = 13, P < 0.0001). In addition, 48 g of traction decreased ETPlat (at closure and reopening) by 0.2 +/- 0.05 cm H2O (P < 0.0001), and decreased ETPant by 0.5 +/- 0.1 cm H2O at closing pressure and 0.8 +/- 0.1 cm H2O at reopening (both p < 0.0001). Thus, for 48 g of traction, PTMlat (at closure and reopening) fell by 1.1 +/- 0.2 cm H2O and PTMant (reopening only) fell by 0.9 +/- 0.3 cm H2O (all P < 0.0001). CONCLUSIONS: Since tracheal traction decreased PTMlat and PTMant by a greater amount than ETPlat and ETPant, we conclude that the decrease in upper airway collapsibility mediated by lung volume related caudal tracheal traction is partially explained by reductions in ETP.     

Constant mean airway pressure with different patterns of positive pressure breathing during the adult respiratory distress syndrome

Twenty-one ARDS patients were divided into two groups of severity according to FIO2 and PEEP required to maintain an adequate gas exchange. The 10 most severe patients (group A) underwent continuous positive pressure ventilation (CPPV) (I/E 3:1) with the mean airway pressure maintained at 21 +/- 6.2 cmH2O. The PEEP values were 12.6 +/- 4.3 cmH2O during CPPV and 6.5 +/- 3.7 cmH2O during IRV (p less than 0.01). Eleven less severe ARDS patients (group B) underwent CPPV and positive pressure spontaneous breathing (CPAP) at constant mean airway pressure of 14.3 +/- 3.8 cmH2O. The PEEP was 7 +/- 2.5 cmH2O during CPPV and 14.9 +/- 4.3 cmH2O during CPAP (p less than 0.001). In five patients of each group, the SF6 shunt was measured as representative of true shunt. The results showed that gas exchange, including true shunt, and haemodynamics did not change between CPPV and IRV and between CPPV and CPAP tests. Taken with previous work on mean airway pressure, our results further support the concept that the main determinant of oxygenation and haemodynamics is the mean airway pressure, irrespective of the PEEP level and of the mode of ventilation.     

Non-invasive measurement of total respiratory compliance and resistance in cats

We adapted non-invasive techniques developed for human infants to measure total respiratory system compliance (Crs) and resistance (Rrs) in 21 healthy cats. The animals breathed through a face mask attached to a respiratory circuit and measurements were taken of changes in lung volume and airway pressure during brief occlusions of the airway at different lung volumes. The slope of the plot of change in volume against airway pressure yielded the multiple occlusion Crs with a mean (+/-95%CI) value of 6.8 (6.3-7.3) ml/cm H2O. In 12 animals measurements were made by the single breath technique in which occlusion was made early in expiration and on release, a plot of the subsequent relaxed expiratory flow and volume yielded the time constant (taurs), Crs and Rrs with mean (+/-95%CI) values of 0.27 (0.22-0.31) s, 7.0 (6.1-7.8) ml/cm H2O, and 38.7 (33.7-43.6) cm H2O/l/s, respectively. Rrs was significantly correlated inversely with forced expiratory flow at resting lung volume (V'maxFRC).     

双水平正压通气对慢阻肺患者行椎管内麻醉及手术时呼吸功能的影响

目的探讨双水平正压通气对慢性阻塞性肺疾病（COPD）患者在椎管内麻醉及手术中呼吸支持的效果。方法选择23例COPD合并Ⅱ型呼吸衰竭拟行下腹部或下肢手术的患者,腰-硬联合麻醉后行双水平正压（BiPAP）通气,BiPAP呼吸机采用S／T模式,设定呼吸频率为15次／min,吸气相压力（IPAP）为10～16cmH2O,呼气相压力（EPAP）为4cmH2O,吸入氧浓度为50％。监测无创血压、呼吸、心电图、脉搏氧饱和度、麻醉前、BiPAP通气后1h及脱机30min后的动脉血气值。结果患者BiPAP通气后动脉血二氧化碳分压（PaCO2）显著降低,从（62．6±13．1）mmHg降至（51．0±8．7）mmHg（P〈0．01）;动脉血氧分压（PaO2）显著增高,从（54．3±12．2）mmHg升至（71．4±14．5）mmHg（P〈0．01）;动脉血pH显著增高,从（7.31±0．09）升至（7．39±0．07）,（P〈0．01）;脱离BiPAP通气30min后动脉血气比麻醉前基础水平略有改善,但差异无统计学意义（P〉0．05）。结论双水平正压通气可明显改善COPD患者在低平面阻滞麻醉及手术期呼吸功能。     

A new expiratory support system for resolving air trapping in lungs during mechanical ventilation: a lung model study.

The aim of the study was to assess a new expiratory support (ES) system in resolving air trapping in the lungs during mechanical ventilation. The ES system consisted of a cylinder and two valves that were connected to the ventilatory circuit. The movements of them were synchronized with the ventilator. The cylinder aspirated gas during expiration. We compared the effects of the ES on air trapping between a narrower and an ordinary size endotracheal tube (ETT) (internal diameter (ID): 5 and 8 mm). In addition, we compared the effects of the ES on air trapping between normal and high airway resistance of the lungs (5 and 20 cm H(2)O/L/s). The ventilatory settings were as follows: volume controlled ventilation with constant inspiratory flow rate; tidal volume, 0.5 L; inspiratory time, 1.0 s; expiratory time, 1.0, 1.5, or 2.0 s; and PEEP, 0 cm H(2)O. The ES normalized the end-expiratory alveolar pressure of the 5 mm ID ETT at a level similar to that of the 8 mm ID ETT. The ES also resolved the air trapping induced by the high airway resistance of the lungs. In conclusion, the ES system resolved the air trapping associated with a narrow endotracheal tube and high airway resistance of the lungs.     

A comparison of nine nasal continuous positive airway pressure machines in maintaining mask pressure during simulated inspiration.

Nasal continuous positive airway pressure (CPAP) "splints" the airway and prevents inspiratory collapse of the upper airway in patients with obstructive sleep apnea. Nine nasal CPAP machines were compared for their ability to maintain airway pressure at various simulated inspiratory flows. Each machine was connected to a vacuum system at 20, 40, and 60 L/min flow after it was initially set at test pressures of 5, 10, or 15 cm H2O and the system or "mask" pressures were measured. In all machines, mask pressure fell during simulated inspiration and the declines in mask pressure were as high as 5 cm H2O. Because machines varied in their ability to maintain a test pressure, it is recommended that the nasal CPAP machine used in the home be the same as that which was tested in the sleep laboratory. If a different machine is used, it may require adjustment to assure efficacy.     

Influence of head extension, flexion, and rotation on collapsibility of the passive upper airway

STUDY OBJECTIVES: To determine the effect of head posture on upper airway collapsibility and site of collapse of the passive human upper airway. DESIGN: Pharyngeal critical closing pressure (Pcrit) and site of airway collapse were assessed during head flexion, extension and rotation in individuals undergoing propofol anesthesia. SETTING: Operating theatre of major teaching hospital. PARTICIPANTS: Fifteen healthy volunteers (8 male), including 7 who were undergoing surgery unrelated to the head or neck. MEASUREMENTS AND RESULTS: Applied upper airway pressure was progressively decreased to induce variable degrees of inspiratory flow limitation and to define Pcrit. Upper airway and oesophageal pressure transducers identified the site of collapse. Genioglossus muscle activity (EMGgg) was assessed using intramuscular fine wire electrodes inserted percutaneously. Data from 3 subjects were excluded from analysis due to persistent EMGgg. In the neutral posture Pcrit was -0.4 +/- 4.4 cm H2O and collapsed most frequently in the velopharyngeal region. Relative to neutral, Pcrit increased to 3.7 +/- 2.9 cm H2O (P < 0.01) and decreased to -9.4 +/- 3.8 cm H2O (P < 0.01) when the head was flexed and extended, respectively but was unchanged by rotation (-2.6 +/- 3.3 cm H2O; n = 10; P = 0.44). The site of collapse varied, in no consistent pattern, with change in head posture in 5 subjects. CONCLUSIONS: Head posture has a marked effect on the collapsibility and site of collapse of the passive upper airway (measured by EMGgg) indicating that controlling head posture during sleep or recovery from anesthesia may alter the propensity for airway obstruction. Further, manipulating head posture during propofol sedation may assist with identification of pharyngeal regions vulnerable to collapse during sleep and may be useful for guiding surgical intervention.     

Hemodynamic, mechanical and renal effects during "apneic oxygenation" with extracorporeal carbon dioxide removal, at different levels of intrapulmonary pressure in lambs.

It has been shown that apneic oxygenation can be safely performed for many days when metabolic carbon dioxide is removed by an extracorporeal membrane lung, and 100% oxygen is supplied directly into the trachea to keep the intrapulmonary pressure at 5 cm. H2O. The study was designed to find "best intrapulmonary pressure (IP)", analogous to "best PEEP" during continuous positive pressure ventilation. In the present study we have shown that when IP was progressively raised from 5cm H2O to 20 cm H2O the PaO2 rose significantly due to progressive decrease in QVA/Q. A linear positive correlation was found between CO and QVA/Q. There was a negative correlation between QVA/Q and FRC. Total static lung compliance and FRC increased significantly at 15--20 cm H2O IP. There was no significant change in urinary flow, urea and creatinine clearances. We conclude that in apneic oxygenation a more "optimal IP" is attained at an IP pressure of 20 cm H2O than at 5 cm H2O.     

喉罩对颈总动脉和颈内动脉血流动力学的影响

目的 研究喉罩对颈总动脉(CCA)和颈内动脉(ICA)内径、血流速率和血流量等血流动力学参数的影响.方法 随机选择择期全麻下行腹腔镜胆囊切除术患者60例,为美国麻醉医师协会(ASA)Ⅰ～Ⅲ级.根据不同年龄分为中青年组(A组,20～59岁)和老年组(B组,60～85岁).按不同的喉罩套囊内压力将A组和B组分为4个亚组,即A1、B1(套囊内压为20～30 cm H2O)(1 cm H2O=0.098 kPa)和A2、B2(套囊内压为40～50 cm H2O),每组15例.所有患者术毕后送入ICU复苏,尚未清醒时拔除气管导管,而后置入喉罩.记录置入喉罩前(T0),置入喉罩后3 min(T1)、10 min(T2)和拔除喉罩后(T3)各时点CCA和ICA的内径、血流速率和血流量等血流动力学参数以及生命体征参数.结果 CCA、ICA的内径和CCA血流量的基础值B组比A组要大(P<0.05).与T0比较,在T1和T2时点,A组和B组CCA内径分别减少9.5%～12.9%和14.5%～24.3%(P<0.05或P<0.01),其中以B2组减少最为显著,A2组和B2组ICA内径分别减少10.9%和16.3%(P<0.05).CCA和ICA的血流速率无明显变化(P>0.05).与T0比较,A组和B组,T1和T2时CCA的血流量分别减少9.3%～10.7%和12.2%～19.1%(P<0.05),其中以B2组减少最为显著,A组和B组ICA血流量分别减少10.0%～13.5%和13.9%～16.6%(P<0.05).在T3时点各观察指标均恢复至T0水平.结论 喉罩通气时,CCA和ICA的内径有所缩小,其血流量相应减少,老年患者减少更为明显,而其血流速率则无明显改变.     

无创通气下应用强迫振荡技术检测呼吸阻力

目的 构建强迫振荡测量系统,在无创正压通气(NPPV)条件下检测人呼吸系统阻抗(Rrs)和电抗(Xrs),用于评估肺阻力(RL)和弹件阻力(EL).方法 基于现有的强迫振荡技术,构建包括振荡发生器和信号分析软件在内的新强迫振荡测量系统,采用呼吸系统一阶线性力学模型(R-I-E模型)验证新系统测量的准确性和可靠性.8例健康正常人为研究对象,分别经鼻罩给予不同水平的双水平气道止压(BiPAP)和持续气道正压(CPAP)通气,探讨在不同通气模式和压力水平下利用Rrs无创评价R,的可行性.结果 (1)振荡压力和振荡流量的相干函数系数值r2=0.98,强迫振荡测量可靠.5 Hz强迫振荡测定的模型阻抗与模型的粘性阻力接近,两者平均相差(1.26±0.44)cm H2O·s·L-1,一敛性范嗣在(0.36～2.14)cm H2O·s·L-1.(2)8例在不同通气模式及压力条件下测定的Rrs值大小接近,与RL平均相差(0.16±1.58)cm H2O·s·L-1.RL的预计方程式为RL=1.40+0.77Rrs,[决定系数(r2)=0.43,P<0.01].(3)强迫振荡弹性阻力EFOT(EFOT=-2πfXrs)显著大于实际值EL,(P<0.01).两者存在低水平的相关(r=0.40,P<0.01).结论 新强迫振荡系统测量准确、可靠.Rrs近似地反映了RL的大小,RL预测值可用于优化NPPV的压力支持水平,使呼吸机提供的压力支持能有效地克服肺阻力.     

Effect of expiratory positive airway pressure on sleep disordered breathing

STUDY OBJECTIVES: We sought to determine the effect of expiratory positive airway pressure on end expiratory lung volume (EELV) and sleep disordered breathing in obstructive sleep apnea patients. DESIGN: Observational physiology study PARTICIPANTS: We studied 10 OSA patients during sleep wearing a facial mask. We recorded 1 hour of NREM sleep without treatment (baseline) and 1 hour with 10 cm H2O EPAP in random order, while measuring EELV and breathing pattern. RESULTS: The mean EELV change between baseline and EPAP was only 13.3 mL (range 2-25 mL). Expiratory time was significantly increased with EPAP compared to baseline 2.64 +/- 0.54 vs 2.16 +/- 0.64 sec (P = 0.002). Total respiratory time was longer with EPAP than at baseline 4.44 +/- 1.47 sec vs 3.73 +/- 0.88 sec (P = 0.3), and minute ventilation was lower with EPAP vs baseline 7.9 +/- 4.17 L/min vs 9.05 +/- 2.85 L/min (P = 0.3). For baseline (no treatment) and EPAP respectively, the mean apnea+hypopnea index (AHI) was 62.6 +/- 28.7 and 56.8 +/- 30.3 events per hour (P = 0.4). CONCLUSION: In OSA patients during sleep, the application of 10 cm H2O EPAP led to prolongation of expiratory time with only marginal increases in FRC. These findings suggest important mechanisms exist to avoid hyperinflation during sleep.     

Comparison of automatic (AUTO-CPAP)and "manual" CPAP pressure titration in patients with obstructive sleep apnea

Auto-CPAP gives an opportunity to decrease costs of evaluating patient with OSA, replacing manual titration of pressure during PSG. The aim of this study was to compare automatic (auto-CPAP) and manual CPAP pressure titration in patients with OSA. We studied 50 obese patients (BMI--35 +/- 6 kg/m2), mean age 52.4 +/- 9.4 years with severe OSA, mean: AHI--62.9 +/- 22.1, mean overnight SaO2--89.1 +/- 3.7%, T90--54.4 +/- 29.6%. Two polysomnographies were performed: first when patient slept with CPAP and pressure was titrated manually by a technician and second on auto-CPAP device. Both methods had similar efficacy in reduction of AHI (< 10/h) and hypoxaemia, despite lower pressure established during auto-CPAP mode preventing apnoeas and hypopnoes during 90% of sleep time (8.2 +/- 1.7 cm H2O) compared to manual CPAP titration (9.2 +/- 1.7 cm H2O) (p < 0.05). CONCLUSION: Auto-CPAP seems to be a reliable alternative to manual titration of the therapeutic pressure in patients with OSA. This may help to cut a waiting list for PSG of patients suspected of OSA.