Dead Space Breathing in Patients with Malignancies: Determination by Cardiopulmonary Exercise Testing

Rationale: Patients with cancer commonly experience dyspnea originating from ventilatory, circulatory and musculoskeletal sources, and dyspnea is best determined by cardiopulmonary exercise testing (CPET). Objectives: In this retrospective pilot study, we evaluated patients with hematologic and solid malignancies by CPET to determine the primary source of their dyspnea. Methods: Subjects were exercised on a cycle ergometer with increasing workloads. Minute ventilation, heart rate, breathing reserve, oxygen uptake (V’O2), O2-pulse, ventilatory equivalents for carbon dioxide and oxygen (V’E/V’CO2 and V’E/V’O2, respectively) were measured at baseline and peak exercise. The slope and intercept for V’E/V’CO2 was computed for all subjects. Peak V’O2 4% predicted indicated a circulatory or ventilatory limitation. Results: Complete clinical and physiological data were available for 36 patients (M/F 20/16);32 (89%) exhibited ventilatory or circulatory limitation as shown by a reduced peak V’O2 and 10 subjects with normal physiologic data. The largest cohort comprised the pulmonary vascular group (n = 18) whose mean ± SD peak V’O2 was 61% ± 17% predicted. There were close associations between V’O2 and spirometric values. Peak V’E/V’O2 and V’E/V’CO2 were highest in the circulatory and ventilatory cohorts, consistent with increase in dead space breathing. The intercept of the V’E-V’CO2 relationship was lowest in patients with cardiovascular impairment. Conclusion: Dyspneic patients with malignancies exhibit dead space breathing, many exhibiting a circulatory source for exercise limitation with a prominent pulmonary vascular component. Potential factors include effects of chemo- and radiation therapy on cardiac function and pulmonary vascular endothelium.

Prognostic value of time-varying dead space estimates in mechanically ventilated patients with acute respiratory distress syndrome

Background The dead space fraction(VD/VT)has proven to be a powerful predictor of higher mortality in acute respiratory distress syndrome(ARDS).However,its measurement relies on expired carbon dioxide,limiting its widespread application in clinical practice.Several estimates employing routine variables have been found to be reliable substitutes for direct measurement of VD/VT.In this study,we evaluated the prognostic value of these dead space estimates obtained in the first 7 days following the initiation of ventilation.Methods This retrospective observational study was conducted using data from the Chinese database in intensive care(CDIC).Eligible participants were adult ARDS patients receiving invasive mechanical ventilation while in the intensive care unit between 1st January 2014 and 31st March 2021.We collected data during the first 7 days of ventilation to calculate various dead space estimates,including ventilatory ratio(VR),corrected minute ventilation(V_(Ecorr)),VD/VT(Harris–Benedict),VD/VT(Siddiki estimate),and VD/VT(Penn State estimate)longitudinally.A time-dependent Cox model was used to handle these time-varying estimates.Results A total of 392 patients(median age 66[interquartile range:55–77]years,median SOFA score 9[interquartile range:7–12])were finally included in our analysis,among whom 132(33.7%)patients died within 28 days of admission.VR(hazard ratio[HR]=1.04 per 0.1 increase,95%confidence interval[CI]:1.01 to 1.06;P=0.013),V_(Ecorr)(HR=1.08 per 1 increase,95%CI:1.04 to 1.12;P<0.001),VD/VT(Harris–Benedict)(HR=1.25 per 0.1 increase,95%CI:1.06 to 1.47;P=0.006),and VD/VT(Penn State estimate)(HR=1.22 per 0.1 increase,95%CI:1.04 to 1.44;P=0.017)remained significant after adjustment,while VD/VT(Siddiki estimate)(HR=1.10 per 0.1 increase,95%CI:1.00 to 1.20;P=0.058)did not.Given a large number of negative values,VD/VT(Siddiki estimate)and VD/VT(Penn State estimate)were not recommended as reliable substitutes.Long-term exposure to VR>1.3,V_(Ecorr)>7.53,and VD/VT(Harris–Benedict)>0.59 was independently associated with an increased risk of mortality in ARDS patients.These findings were validated in the fluid and catheter treatment trial(FACTT)database.Conclusions In cases where VD/VT cannot be measured directly,early time-varying estimates of VD/VT such as VR,,V_(Ecorr),and VD/VT(Harris–Benedict)can be considered for predicting mortality in ARDS patients,offering a rapid bedside application.

Hydrodynamic characteristics of a four-compartment periodic anaerobic baffled reactor

Periodic anaerobic baffled reactor （PABR） is a novel reactor based on the design concept of anaerobic baffled reactor （ABR）. Residence time distribution （RTD） studies on both clean and working reactors at the same hydraulic residence time （HRT） of 2 d were carded out to investigate the dead spaces and mixing patterns in PABRs at different organic loading rates （OLRs） in various switching manners and frequencies. The results showed that the fraction of dead space in PABR was similar to that in ABR, which was low in comparison with other reactor designs. Dead space may be divided into two categories, hydraulic and biological. In RTD studies without biomass, the hydraulic dead space in the PABR run in an ＂every second＂ switching manner with T = 2 d was the lowest whereas that in the PABR run in a T = ∞ （ABR） switching manner was the highest. The same trend was obtained with the total dead space in RTD studies with biomass no matter what the OLR was. Biological dead space was the major contributor to dead space but affected decreasingly at higher OLR whichever switching manner the PABR run in. The flow patterns within the PABRs were intermediate between plug-flow and perfectly mixed under all the conditions tested,

Application of Froude dynamic similitude in anaerobic baffled reactors to prediction of hydrodynamic characteristics of a prototype reactorusing a model reactor

An anaerobic baffled reactor is a system developed in recent decades and has been used as part of the treatment of high-strength wastewater. Since the function of this system is based on its hydrodynamic features, hydrodynamics and the regime of the flow through the reactor are crucial. In this study, a prototype reactor with eight chambers, which had a total volume of 48 L, and a model reactor, whose dimensions were half of those of the prototype reactor, were used. The Froude dynamic similitude in these reactors was investigated. The results show that the curve dimensionless variances were 0.089 and 0.096 for the prototype and model reactors, respectively, the short-circuiting indices were 0.483 and 0.489 for the prototype and model reactors, respectively, the effective volume and short-circuiting index measurement errors were both 1%, the hydraulic efficiency error was 2%, and the Peclet and dispersion number errors were both 7%. Most of the compared indices were close to one another in value. Therefore, the model reactor can be used based on the Froude dynamic similitude to determine hydrodynamic charac-teristics of a baffled reactor at a full scale.

Hydraulic modeling of an anaerobic expanded bed reactor for municipal sewage treatment

Anaerobic expanded bed reactor(AEBR) is mostly used for the treatment of fairly low strength wastewaters. Since the performance of AEBR largely depends on its hydraulic characteristics, residence time distribution(RTD) method is commonly used for investigation of the hydraulic characteristics of AEBR under different ascending velocity of mixed liquor. In this paper, a pilot-scale AEBR reactor is investigated for treatment of municipal sewage in which lithium chloride is used as a tracer. The results show that the AEBR could be considered as the superimposition of several constant stirred tank reactors(CSTR) and the increase of hydraulic up-flow velocity could increase the number of the CSTR and decrease the volume rate of the dead zone. The optimal up-flow velocity of the investigated AEBR was approximately 1.9 m/h in the municipal sewage treatment.

Is COVID-19 different from other causes of acute respiratory distresssyndrome?

Coronavirus disease 2019(COVID-19)pneumonia can lead to acute hypoxemic respiratory failure.When mechanical ventilation is needed,almost all patients with COVID-19 pneumonia meet the criteria for acute respiratorydistress syndrome(ARDS).The question of the specificities of COVID-19-associated ARDS compared to othercauses of ARDS is of utmost importance,as it may justify changes in ventilatory strategies.This review aims todescribe the pathophysiology of COVID-19-associated ARDS and discusses whether specific ventilatory strategiesare required in these patients.

Hydraulic characteristics of an anaerobic baffled reactor as onsite wastewater treatment system

The feasibility of using anaerobic baffled reactor （ABR） as onsite wastewater treatment system was discussed. The ABR consisted of one sedimentation chamber and three up-flow chambers in series was experimented under different peak flow factors （PFF of 1 to 6）, superficial gas velocities （between 0.6 and 3.1 cm/hr） and hydraulic retention times （HRT） （24, 36 and 48 hr）. Residence time distribution （RTD） analyses were carded out to investigate the hydraulic characteristics of the ABR. It was found that the PFF resulted in hydraulic dead space. The dead space did not exceed 13% at PFF of 1, 2 and 4 while there was 2-fold increase （26%） at PFF of 6. Superficial gas velocities did not result in more （biological） dead space. The mixing pattern of ABR tended to be a completely- mixed reactor when PFF increased. Superficial gas velocities did not affect mixing pattern. The effects of PFF on mixing pattern could be minimized by higher HRT （48 hr）. The tank-in-series （TIS） model （N = 4） was suitable to describe the hydraulic behaviour of the studied system. The HRT of 48 hr was able to maintain the mixing pattern under different flow patterns, introducing satisfactory hydraulic efficiency. Chemical oxygen demand （COD） and total suspended solids （TSS） removals under all flow patterns were achieved more than 85% and 90%, respectively. The standard deviation of effluent COD and TSS concentration did not exceed 15 mg/L.

硬骨凌霄叶对伤口愈合的促进作用(英文)

The aim of the present study was to evaluate the potential wound healing activity of Tecomaria capensis leaves extract (TCLE) using different models in rats. (a) Excision wound model, (b) Incision wound model and (c) Dead space wound model. TCLE (100, 300, 1 000 and 2 000 mg·kg-1) was given to rats to observe acute toxicity. No toxicity was found in animals till 14 days. TCLE 5% and 10% ointment were applied topically in excision wound model and incision wound model. TCLE 200 and 400 mg·kg-1 were given orally in dead space wound model. It improved healing in excision wound model, increased breaking strength of tissue in incision wound model, and increased granuloma breaking strength and hydroxyproline content in dead space wound model. These results showed that TCLE presents significant wound healing activity.