Ventilatory support in the intensive care unit

This article focuses on the functional features of positive-pressure ventilators, the modes of invasive and non-invasive mechanical ventilation, and the main ventilator settings. It also highlights the potential complications of mechanical ventilation, the basic principles of weaning, and the pathophysiological basis of patient-ventilator dyssynchrony.     

Prevention of Descending Pneumonia in Rats with Perflubron-delivered Tobramycin

OBJECTIVES: Patients undergoing emergent endotracheal intubation are at increased risk for developing pneumonia. Although numerous strategies have been investigated to reduce ventilator-associated pneumonia (VAP), the incidence of VAP and its associated mortality remains high. This investigation tested the hypothesis that LiquiVent (Alliance Pharmaceutical, San Diego, CA-LV) delivered antibiotics (via spray-dried microspheres-SDM) would improve survival in a rat model of descending gram-negative pneumonia. METHODS: Wistar rats (n = 49) were randomized to receive prophylaxis with 1). nothing (controls); 2). intramuscular (IM) tobramycin, 3). intratracheal LV plus SDM shells (vehicle), 4). intratracheal LV plus SDM shells plus IM tobramycin, or 5). intratracheal LV plus SDM containing 1 mg/kg of tobramycin. All interventions were given 24 hours before a bacterial challenge with 10(8) colony-forming units of intratracheal Klebsiella pneumoniae. Mortality at ten days was the sole outcome measure. Survival in individual groups was compared with controls by Fisher's exact test with Bonferroni correction for multiple comparisons. RESULTS: All animals in the control group died of pneumonia within ten days of bacterial inoculation (0% survival). Prophylaxis with either IM tobramycin or SDM vehicle plus IM tobramycin provided no protection (0% survival). This is in sharp contrast to the cohort receiving pretreatment with tobramycin-containing SDM delivered via LV, in which 60% of the animals survived to study completion (p < 0.05). CONCLUSIONS: Prophylaxis with SDM containing antibiotics delivered in low-dose LV provided significant protection in a rat model of descending gram-negative pneumonia. These data support the hypothesis that perfluorocarbon-delivered intratracheal antimicrobials may be useful in the prevention of VAP.     

The interactive role of mucosal T lymphocytes in intestinal growth, development and enteropathy

Abstract Over the past 15–20 years, research has progressively focused on the mucosal T cell as the central factor in the initiation of physiological or pathological changes, first in the growth and maturation of the early (postnatal) intestine, and second in adult-type enteropathies resulting from sensitivity to either food or pathogen-derived antigens. T cell-mediated events may be measured, for example, in terms of specific immunopathologic patterns of change and injury, such as type 1 (lymphocyte infiltration), type 2 (crypt hyperplasia) and type 3 (flat-destructive), which can be recognized and quantitated microscopically; by determination of lymphocyte reactivity through secretion of interleukin-2 receptors (IL-2R) into plasma or expression by mucosal lymphocytes; by quantitation of lymphocyte subsets emigrating into inflamed tissues by immunoperoxidase-labelled monoclonal antibodies; or by the determination of T cell receptor polymorphisms. Alterations in intestinal growth, structure and function at weaning are likely to be T cell-mediated as they are analogous to the same type 1/2 lesions that reflect modulation of adult mucosal architecture in food and parasite-induced hypersensitivity reactions. Enteropathies associated with HIV infection and T cell deficiency display a milder degree of villous flattening and impaired crypt hyperplasia than that typical of gluten-sensitivity, suggesting a reversion to lesser degrees of mucosal pathology (type 1/2). Clearly more information will accrue; meanwhile the remarks in this brief survey should provide a firm basis whereby clinician and scientist can meet, and together recognize and further dissect the modulatory effect of T lymphocytes on mucosal structure and function.     

Carbon dioxide recruitment threshold as a predictor of successful weaning in chronic obstructive pulmonary disease patients: A pilot study

Abstract Several methods have been used to predict successful weaning and extubation among chronic obstructive pulmonary disease (COPD) patients. The objective of this study is to determine whether carbon dioxide recruitment threshold (PCO₂RT) can be used as adjunct to conventional weaning parameters to predict early weaning and successful extubation. Twelve COPD patients who were ready to be extubated based on conventional weaning parameters were divided into group A ( n = 7) and group B ( n = 5). Group A were those patients with better weaning parameters and hence a higher probability of successful extubation as compared to group B. Carbon dioxide apnoeic threshold (PCO₂AT) was obtained by hyperventilating the patient using an increment of two breaths per min until apnoea occurs. At this point, the PCO₂AT or the PaCO₂ during said apnoeic period was recorded. A dead space of 150 cc is then added to the circuit until the patient starts to breathe as evidenced by the sensitivity trigger indicator. The PCO₂ obtained at this period is termed PCO₂RT. After weaning for 30 min on a T-tube, another arterial blood gas is determined and this is called the PCO₂SB or the CO₂ level after 30 min on spontaneous breathing. If the PCO₂SB-PCO₂RT difference is high with a sensitivity of 85.71% and specificity of 100% vs sensitivity of 57.14% and specificity of 60% using the conventional weaning parameters. Thus an increase in PCO₂SB at 30 min T-tube is indicative of impending respiratory pump failure and that other causes of failure to wean must be investigated.     

鸟牌呼吸机故障及排除三例

呼吸机在国内外医院广泛应用，详细介绍鸟牌呼吸机在临床上3例常见的故障和排除方法。     

A Weaning Reaction to Microbiota Is Required for Resistance to Immunopathologies in the Adult

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A Consideration on the new classification of latest lung ventilators

Concerning the classification of ventilators, Elam (1958), Faireley (1959), and Hunter (1961) reported some simple ones such as pressure limited, volume limited, pressure preset, or volume preset models. Mapleson (1969) also classified them by the generating force or cycling together with the above-mentioned types.The latest ventilators applicable to patients with respiratory failure usually have some cut-off function at high airway pressures as a safety measure. Therefore, all of them belong to the pressure limited type. Some ventilators are of two types such as the time cycled and pressure cycled type.Therefore, we attempted to classify ventilators into four groups, i.e. the time cycled, volume cycled, pressure cycled and selective time-pressure cycled types according to the fundamental mode of ventilator function, the so-called change of cycling from inspiration to expiration. Each group was further divided into subgroups according to preset dials such as respiratory rate, I/E ratio, inspiration time, expiration time, tidal volume, flow rate and airway pressure.By this method, fifty one ventilators on the market in Japan can be classified without overlapping. Although this classification seems complex, it will be of use in selecting ventilators by emphasizing preset dials according to the users needs, ability or both.(Goto Y, Takahashi K, Harada J et al.: A consideration on the new classification of latest lung ventilators. J Anesth 1: 178–182, 1987)     

无创呼吸机治疗新生儿肺炎临床疗效

目的:探究新生儿肺炎患儿采用无创呼吸机治疗的临床效果。方法:于2017年5月~2019年9月选取本院收治的88例新生儿肺炎患儿,按照数字表法分为2组,对照组44例患儿实施头罩式吸氧治疗,观察组44例采用无创呼吸机治疗,并对两组患儿的疗效、PaO2以及PaCO2水平进行比较。结果:观察组中的总疗效93.18%,比对照组的72.73%更高(P<0.05);治疗前两组患者心率、PaO2以及PaCO2水平比较没有明显区别(P>0.05);治疗后两组患者心率以及PaCO2水平均有一定降低,PaO2水平有一定升高,且观察组治疗后的升高与降低水平均大于对照组(P<0.05)。结论:新生儿肺炎患儿采用无创呼吸机治疗的临床效果确切,可降低患儿的心率水平,改善其血气指标。