加压胸带预防腹腔镜皮下气肿的临床研究

目的观察加压胸带对腹腔镜下完全腹膜外疝修补术中皮下气肿程度及CO2吸收的影响。方法选择行全麻腹腔镜下完全腹膜外疝修补术患者60例,年龄60～80岁。按随机数字表法分为观察组和对照组,每组30例。前者于入室后麻醉前开始采用加压胸带处理,后者不做任何处理。记录麻醉前(T0)、气腹前5min(T1)、气腹后30min(T2)、60min(T3)、放气腹后15min(T4)和60min(T5)的SBP、DBP、HR、SpO2、气道峰压(Ppeak)、VE、肺顺应性(Compl)和血气分析,并记录术后皮下气肿发生程度等。计算CO2排出率(VCO2)。结果与T0时比较,T2～T5时对照组SBP、DBP、PaCO2均明显升高,HR明显增快,pH明显降低(P0.05);与T1时比较,T2、T3时两组Ppeak、VCO2和VE均明显升高,T4时对照组VCO2和VE明显升高(P0.05或P0.01)。与对照组比较,T2～T5时观察组HR明显减慢,SBP、DBP和PaCO2明显降低,pH明显升高(P0.05);观察组T2、T3时Ppeak明显降低,T2～T4时VCO2及VE明显降低(P0.05或P0.01)。与对照组比较,观察组皮下气肿较严重,清醒时间及拔管时间均明显缩短(P0.05)。结论加压胸带能有效地预防腹腔镜手术中皮下气肿,减轻高碳酸血症及呼吸性酸中毒,对呼吸循环功能影响较小。     

Cerebrovascular reactivity measured by functional magnetic resonance imaging during breath-hold challenge: A systematic review

Cerebrovascular reactivity (CVR) is the cerebral hemodynamic response to a vasoactive substance. Breath-hold (BH) induced CVR has the advantage of being non-invasive and easy to implement during magnetic resonance imaging (MRI). We systematically reviewed the literature regarding MRI measurement of BH induced CVR. The literature was searched using MEDLINE with the search terms breath-hold; and MRI or cerebrovascular reactivity. The search yielded 2244 results and 54 articles were included. Between-group comparisons have found that CVR was higher among healthy controls than patients with various pathologies (e.g. sleep apnea, diabetes, hypertension etc.). However, counter-intuitive findings have also been reported, including higher CVR among smokers, sedentary individuals, and patients with schizophrenia vs. controls. Methodological studies have highlighted important measurement characteristics (e.g. normalizing signal to end-tidal CO₂), and comparisons of BH induced CVR to non-BH methods. Future studies are warranted to address questions about group differences, treatment response, disease progression, and other salient clinical themes. Standardization of CVR and BH designs is needed to fully exploit the potential of this practical non-invasive method.     

Galanin microinjection into the PreBötzinger or the Bötzinger Complex terminates central inspiratory activity and reduces responses to hypoxia and hypercapnia in rat

Respiratory rhythm is generated and shaped by the synaptic interaction of neurons in the Bötzinger Complex (BötC) and PreBötzinger Complex (PreBötC) located in the ventral respiratory column of the medulla. Metabotropic receptors are important modulators of fast neurotransmission in the generation and shaping of respiratory rhythm. Microinjection of the neuropeptide galanin (1 mM, 50 nL, 50 pmol) into functionally identified BötC or PreBötC in urethane anesthetized, mechanically ventilated and vagotomized rats caused severe dysrhythmia or persistent apnea. In the BötC and PreBötC, galanin reduced the ventilatory response to hypercapnia (5% CO₂) by 21% (P < 0.001) and 38% (P < 0.01) respectively. In the BötC and PreBötC, galanin reduced the ventilatory response to hypoxia (10% O₂) by 15% (P < 0.05) and 23% (P < 0.01) respectively. These results indicate that microinjection of galanin into the BötC or PreBötC depresses a neural substrate required for the generation of respiratory motor output and reflex responses to hypercapnea and hypoxia.     

Effects of withdrawal of phasic lung inflation during normocapnia and hypercapnia on the swallowing reflex in humans

Purpose This study was done to test the hypothesis that hypercapnia has a direct, inhibitory effect on swallowing.Methods We investigated changes in the frequency and timing of repeated swallows induced by continuous infusion of water into the pharynx before, during, and after transient airway occlusion at normocapnia and hypercapnia in 12 healthy volunteers. Hypercapnia was induced by adding a dead space. Ventilation was monitored using a pneumotachograph, and swallowing was identified by submental electromyogram.Results We found that hypercapnia decreased the frequency of swallows (8.2 ± 3.7 vs 11.4 ± 5.3 swallows·min^–1 [mean ± SD]: hypercapnia vs normocapnia; P 0.05), together with a loss of the preponderant coupling of swallows with expiratory phase observed at normocapnia. We also found that the withdrawal of phasic lung inflation produced by airway occlusion at end-expiration suddenly increased the swallowing frequency, both at normocapnia (from 11.4 ± 5.3 to 16.7 ± 3.7 swallows·min^–1; P 0.01) and at hypercapnia (from 8.2 ± 3.7 to 22.0 ± 6.7 swallows·min^–1; P 0.01). Although the degree of increased swallowing frequency during airway occlusion was more prominent at hypercapnia than at normocapnia (P 0.05), the distribution of the timing of swallows in relation to the phase of the respiratory cycle during airway occlusion at hypercapnia was similar to that during airway occlusion at normocapnia.Conclusion The results of our study strongly suggest that the attenuation of the swallowing reflex during hypercapnia is not due to the direct, inhibitory effect of CO₂ on the swallowing center, but, rather, is due to the increased inhibitory influence of a lung-volume-related reflex.     

Influence of hypercapnia and hypocapnia on bladder contractions and their respiratory consequences

Rhythmic contractions of the detrusor muscle, induced by gradual filling of the urinary bladder in decerebrate or anesthetized cats, are accompanied by decreased inspiratory activity in motor nerves to respiratory muscles, particularly those of the upper airway. We have examined the influence of hypercapnia and hypocapnia on these contractions and the accompanying activities of the phrenic and hypoglossal nerves in decerebrate, vagotomized, paralyzed and ventilated cats, some of which had denervated carotid chemoreceptors. Hypercapnia slowed, and then reversibly abolished bladder contractions in most animals, regardless of the state of the carotid chemoreceptors. Bladder contractions were well maintained in progressive hypocapnia, even at end-tidal CO(2) levels below the 'apneic' thresholds of the hypoglossal and phrenic activities. The reductions of the nerve activities in response to bladder contractions were not significantly altered by hypercapnia or hypocapnia. The abolition of bladder contractions by hypercapnia is unlikely to reflect a direct effect of CO(2) or H+ ion on the contractile mechanism of the detrusor muscle, but may be based on inhibition of stretch receptors in the bladder wall and/or an effect of CO(2) or H+ in or near the micturition centers in the brain stem.     

慢性肺心病左右心室改变及其与高CO2的关系

目的 研究慢性肺心病左右心室改变的特点及其与高二氧化碳存在的关系。方法 通过复制慢性缺氧性及慢性缺氧高二氧化碳性肺心病模型,观察单纯缺氧四周,缺氧调一氧化碳二周及四周,正常对照组在鼠,肺动脉压,右心室压力及右心室最大压力上升笔下降速度,右室重量（ＲＶ）和左室加室间隔重量（ＬＶ＋Ｓ）,并分析左右心室重的相关性。结果 缺氧四周中及缺氧高二氧化碳二周和四周均引起明星肺动脉高压和右室收缩压升高,其程度相似     

Repeated apneas do not affect the hypercapnic ventilatory response in the short term

Long-term training of breath-hold diving reduces the hypercapnic ventilatory response (HCVR), an index of the CO₂ sensitivity. The aim of the present study was to elucidate whether also short-term apnea training (repeating apneas with short intervals) reduces the HCVR, thereby being one contributing factor explaining the progressively increasing breath-holding time (BHT) with repetition of apneas. Fourteen healthy volunteers performed a series of five maximal-duration apneas with face immersion and two measurements of the HCVR, using the Read rebreathing method. The BHT increased by 43% during the series of apneas (P < 0.001). However, the slope of the HCVR test was not affected by the series of apneas, being 2.52 (SD 1.27) and 2.24 (SD 1.14) l min⁻¹ mmHg⁻¹ in the control test and in the test performed within 2 min after the last apnea of the series, respectively (NS). Thus, a change in the HCVR cannot explain the observed short-term training effect on BHT.     

Severe Acute Asthma with Bowel Infarction and Pneumatosis Intestinalis in a Young Adult

A young patient presented with a small bowel infarction with pneumatosis intestinalis in the early course of life-threatening severe acute asthma. Low cardiac output with severe congestive right heart failure combined with the use of high doses of epinephrine to reverse the near-fatal bronchospasm probably contributed to this previously unreported complication. The presence of gas collections in the submucosal space was possibly the consequence of diffuse small bowel mucosal disruption. Early recognition of this unusual complication is of major importance to ensure appropriate therapeutic management.     

Ventilatory function assessment in safety pharmacology: Optimization of rodent studies using normocapnic or hypercapnic conditions

Although the whole body plethysmography for unrestrained animals is the most widely used method to assess the respiratory risk of new drugs in safety pharmacology, non-appropriate experimental conditions may mask deleterious side effects of some substances. If stimulant or bronchodilatory effects can be easily evidenced in rodents under standard experimental conditions, i.e. normal air breathing and diurnal phase, drug-induced respiratory depression remains more difficult to detect. This study was aimed at comparing the responsiveness of Wistar rats, Duncan Hartley guinea-pigs or BALB/c mice to the respiratory properties of theophylline (50 or 100 mg/kg p.o.) or morphine (30 mg/kg i.p.) under varying conditions (100% air versus 5% CO₂-enriched air, light versus dark day phase), in order to select the most appropriate experimental conditions to each species for safety airway investigations. Our results showed that under normocapnia the ventilatory depressant effects of morphine can be easily evidenced in mice, slightly observed in guinea-pigs and not detected in rats in any day phase. Slight hypercapnic conditions enhanced the responsiveness of rats to morphine but not that of guinea-pigs and importantly they did not blunt the airway responsiveness of rats to the stimulation and bronchodilation evoked by theophylline, the most widely used reference agent in safety pharmacology studies. In conclusion, hypercapnic conditions associated with the non-invasive whole body plethysmography should be considered for optimizing the assessment of both the ventilatory depressant potential of morphine-like substances or the respiratory stimulant effects of new drugs in the rat, the most extensively used species in rodent safety and toxicological investigations.