Understanding the Relationship between Vaccine Supply Dead Space and Wasted COVID-19 Vaccine Doses

ABSTRACT Introduction: By July 2023, Brazil had administered approximately 540 million COVID-19 vaccine doses. This study aimed to quantify wasted doses resulting from dead space in vaccine supplies. Methods: The vaccine supply was initially weighed, filled with distilled water, and expelled to simulate administration. Weighing it again after the application determined the dead space volume. Descriptive analyses calculated the waste rate/wasted dose count. Results: The estimated total number of wasted vaccine doses using supplies with the lowest dead space was 62,097,338. Conclusions: Syringe dead space is a crucial factor in dose wastage, directly influencing the number of wasted doses.

Dead space fraction for treatment guidance and prognosis evaluation of acute respiratory distress syndrome / 中华危重病急救医学

Acute respiratory distress syndrome (ARDS) is a common cause of critical illness and high mortality from respiratory failure. Increased dead space fraction (VD/VT) was independently associated with lung injury and mortality of ARDS. VD/VT is readily obtained by bedside measurements of arterial blood gas and end-tidal carbon dioxide. Early attention and application of VD/VT as an indicator will help to better understand the pathophysiological of ARDS, guide clinical treatment, and better assess the severity and clinical prognosis of the disease.

Correlation between dead space fraction and pulmonary ultrasound score in patients with acute respiratory distress syndrome and its prognostic value / 中华危重病急救医学

Objective:To investigate the correlation between dead space fraction and lung ultrasound score (LUS) and their prognostic value in patients with acute respiratory distress syndrome (ARDS).Methods:The data of 98 patients with ARDS treated in the intensive care unit (ICU) of the First Affiliated Hospital of Jinzhou Medical University from January to December 2020 were collected and analyzed. The gender, age, acute physiology and chronic health evaluationⅡ(APACHEⅡ), oxygenation index, dead space fraction and LUS score immediately and 24, 48, 72 and 96 hours after ICU admission and 28-day outcomes of all patients were collected. Pearson correlation was used to analyze the correlation between dead space fraction and LUS score. Binary Logistic regression was performed to analyze whether the dead space fraction and LUS score could be the risk factors of the prognosis in patients with ARDS. Receiver operator characteristic curve (ROC) was used to analyze the predictive effect of dead space fraction and LUS score on 28-day mortality in patients with ARDS.Results:A total of 98 patients with ARDS were included, of which 76 cases survived and 22 cases died within 28 days. With the prolongation of ICU stay, the dead space fraction and LUS score in the survival group increased first and then decreased. The dead space fraction and LUS score in the death group continued to increase to 96 hours, and were significantly higher than those in the survival group (dead space fraction: 0.569±0.019 vs. 0.491±0.021, LUS score: 20.09±2.39 vs. 15.13±1.91, both P < 0.05). There was a positive correlation between the dead space fraction and LUS score at 48, 72 and 96 hours in ICU ( r values were 0.200, 0.471 and 0.677, all P < 0.05). Binary Logistic regression analysis showed that dead space fraction and LUS score were independent risk factors affecting the prognosis of patients with ARDS [dead space fraction: odds ratio ( OR) was 69.064, 95% confidence interval (95% CI) was 22.680-123.499, P = 0.008; LUS score: OR was 4.790, 95% CI was 1.609-14.261, P = 0.005]. The results of ROC curve analysis showed that the dead space fraction at 48, 72 and 96 hours after ICU admission could be used to predict the 28-day mortality of patients with ARDS, the sensitivity was 59.1%, 90.9% and 95.5%, and the specificity was 89.5%, 80.3% and 98.7%. The area under the curve (AUC) of dead space fraction predicting 28-day mortality was 0.802, 0.952 and 0.998, all P < 0.01. The LUS score of 72 hours and 96 hours in ICU could be used to predict the 28-day mortality of patients with ARDS, the sensitivity was 77.3%, 77.3% and 100.0%, and the specificity was 68.4%, 88.2% and 80.3%, respectively. The AUC of the LUS score to predict the 28-day mortality of patients were 0.935 and 0.959, both P < 0.01. Conclusion:There was significant correlation between dead space fraction and LUS score, both of which were risk factors of 28-day mortality and be used to evaluate the 28-day prognosis of patients with ARDS.

Design and application of a push-pull adjustable artificial dead space / 中华危重病急救医学

Using artificial dead space to correct hypocapnia or induce hypercapnia is of particular significance for diagnosing and treating specific neurocritical diseases. At present, the above purpose is mainly achieved by adding an extension tube between the Y-type connector of the ventilator and the artificial airway in clinical practice. However, its volume is often fixed and cannot adapt to the individualized diagnosis and treatment in different clinical scenarios. The research group led by Professor Zhou Jianxin from the department of critical care medicine of Beijing Tiantan Hospital, Capital Medical University, has designed an artificial dead cavity with adjustable volume based on years of research in the respiratory field and has been granted a national utility model patent (patent number: ZL 2020 2 0496413.4). The artificial dead chamber is simple in structure, composed of a barrel body, a piston head, and a push-pull rod. By freely adjusting the size of the artificial dead chamber volume, it can accurately regulate the target carbon dioxide, correct the spontaneous hyperventilation, terminate intractable hiccup, and shorten the operation time of asphyxia test in clinical diagnosis of brain death while correcting hypocapnia or inducing hypercapnia. It has the advantages of solid reliability, convenient operation, and low production cost, which significantly facilitates scientific research and clinical diagnosis and treatment.

Espacio muerto y destete de ventilación mecánica invasiva en residentes de la gran altitud / Dead space and weaning from invasive mechanical ventilation in high-altitude residents

RESUMEN Objetivo Determinar el valor predictivo del cálculo del espacio muerto a través de la fracción espacio muerto/volumen corriente en el destete de la ventilación mecánica invasiva en pacientes críticamente enfermos en la gran altitud. Materiales y métodos Estudio epidemiológico, observacional, analítico y prospectivo realizado en la Unidad de Terapia Intensiva Adultos del Hospital del Norte de la ciudad de El Alto, Bolivia (4090 m s. n. m. y presión barométrica de 453 mmHg) del 01 de noviembre de 2016 al 31 de marzo de 2017. Se estudiaron a los residentes de la gran altitud en ventilación mecánica invasiva. Los criterios de inclusión fueron los siguientes: a) residentes de la altitud hospitalizados en la Unidad de Terapia Intensiva en ventilación mecánica invasiva, b) pacientes con evidencia de resolución de la causa que motivó su conexión al ventilador mecánico invasivo, c) paciente con criterios e índices de destete positivos, d) prueba de respiración espontanea positivo. Las variables estudiadas fueron el espacio muerto a través de la fracción Vd/Vt y su relación con el éxito o fracaso del proceso de destete de ventilación mecánica. Se calculó la fracción Vd/Vt en los pacientes incluidos en el estudio para luego proceder al destete de la ventilación mecánica invasiva. Se dividió a los pacientes en dos grupos según la necesidad de reintubación y reconexión al ventilador mecánico dentro de las 72 horas. Resultados Se incluyeron 21 pacientes: 7 mujeres (33 %) y 14 varones (67 %). La media de edad fue 41 años con desviación estándar de 22,38 años. Dieciocho pacientes (86 %) presentaron éxito y tres (14,00 %) fracasaron en el proceso de destete de la ventilación mecánica invasiva. El valor de Vd/Vt en el grupo éxito y fracaso correspondió a 0,43 vs. 0,53 (p < 0,011109), con una sensibilidad de 0,61 y especificidad de 1; con valor predictivo positivo de 1 y valor predictivo negativo de 0,3. Conclusiones El cálculo del espacio muerto a través de la medida de la fracción espacio muerto/volumen corriente predice el éxito del destete de pacientes críticamente enfermos bajo ventilación mecánica invasiva a gran altitud.

ABSTRACT Objective To determine the predictive value of the dead space calculation through the dead space/tidal volume fraction at weaning from invasive mechanical ventilation in critically ill patients at high altitude. Materials and methods An epidemiological, observational, analytical and prospective study carried out in the Adult Intensive Care Unit of the Hospital del Norte in the city of El Alto, Bolivia (4,090 m a.s.l.; barometric pressure: 453 mm Hg) from November 01, 2016 to March 31, 2017. High-altitude residents under invasive mechanical ventilation were studied. The inclusion criteria were: a) Altitude residents hospitalized in the Invasive Mechanical Ventilation Therapy Intensive Care Unit. b) Patients with evidence of resolution of the cause that prompted their connection to the invasive mechanical ventilator. c) Patients with positive weaning criteria and rates. d) Positive spontaneous respiration test. The study variables were the dead space through the Vd/Vt fraction and its relationship with the success or failure of the weaning process from mechanical ventilation. The Vd/Vt fraction was calculated in the study patients and then weaning from invasive mechanical ventilation was performed. Patients were divided into two groups according to the need for reintubation and reconnection to the mechanical ventilator within 72 hours. Results Twenty-one (21) patients were included: 7 (33 %) women and 14 men (67 %). The mean age was 41 years with a standard deviation of 22.38 years. Eighteen (18) patients (86 %) succeeded and 3 (14 %) failed in the weaning process from invasive mechanical ventilation. The Vd/Vt values in the success and failure groups were 0.43 and 0.53 (p < 0.011109), respectively, with a sensitivity of 0.61 and specificity of 1; a positive predictive value of 1 and a negative predictive value of 0.3. Conclusions The calculation of the dead space through the measurement of the dead space/tidal volume fraction predicts the success of weaning of critically ill patients under invasive mechanical ventilation at high altitude.

Diagnostic value of volumetric capnography in patients with chronic cough variant asthma

OBJECTIVES: To evaluate the quantitative changes and diagnostic performance of volumetric capnography (VCap) parameters in patients with cough variant asthma. METHODS: This cross-sectional study enrolled 31 patients with cough variant asthma and 30 patients with chronic cough without asthma between November 2010 and March 2012. VCap measurements were recorded at baseline, during the five steps of the histamine challenge, and after bronchodilation with salbutamol. They were then compared between the baseline and histamine challenge, and between the two groups. Receiver operating characteristic curve analysis was performed for different VCap measurements. RESULTS: The slope of phase III (dc/dv3) and the ratio of phase III slope to phase II slope (SR23%) decreased from baseline upon challenge with 1.1 mg histamine in cough variant asthma patients but increased in patients with chronic cough without asthma. Additionally, the change upon challenge with 1.1 mg histamine in dc/dv3 from baseline (S6-S1dc/dv3) in cough variant asthma patients had the largest area under the curve (AUC) (0.814, 95% CI: 0.697-0.931; p<0.001). The AUC for change upon challenge with 1.1 mg histamine in SR23% from baseline was 0.755 (95%CI: 0.632-0.878; p<0.001). At a cutoff of 19.8, S6-S1 dc/dv3 had a sensitivity of 74.2% and specificity of 90.0% and at a cutoff of 40.7, S6-S1 SR23% had a sensitivity of 48.4% and specificity of 96.7%. CONCLUSION: Patients with cough variant asthma exhibit distinct VCap responses for dead space parameters upon challenge with histamine in comparison to patients with chronic cough. VCap parameters like phase III slope and phase III/phase II slope ratio could be used to aid the diagnosis of cough variant asthma.

Application of alveolar dead space fraction in acute respiratory distress syndrome / 国际儿科学杂志

The high mortality of acute respiratory distress syndrome(ARDS) has been a great challenge in the intensive care unit and early diagnosis and treatment have greatly improved the prognosis of ARDS.In the previous studies,the problem has been studied mainly on the alveolar collapse and pulmonary shunt.However,recent studies have shown that the alveolar dead space ventilation in ARDS is also significantly increased,and may be related to the severity and prognosis of ARDS which has received a generous concern and become a research focus.This article reviews the progress in alveolar dead space fraction (ADSF) which may shed light on the role of ADSF in the diagnosis and treatment of ARDS.

Evaluation value of dead-space fraction on prognosis of acute respiratory distress syndrome / 重庆医学

Objective To investigate the dynamic changes of dead space fraction (VD/VT) and its effect on the prognosis in the patients with acute respiratory distress syndrome (ARDS).Methods Thirtytwo patients with ARDS in EICU of the First Affiliated Hospital of Kunming Medical University from January 2015 to August 2016 were selected and divided into the survival group and the death group according to the 28 d mortality rate.VD/VT on 1-6 d in the two groups was calculated according to the formula.The parameters of basic condition,PaO2/FiO2,APACHE Ⅱ score,LIPS score,PEEP of the two groups were compared.Results LIPS and APACHE Ⅱ scores had statistical difference between the death group and survival group (P＜0.05);VD/VT on 1-3 d had no statistical difference between the two groups (P＞0.05),and VD/VT on 4-6 d in the death group was significantly higher than that in the survival group (P＜0.01).△PCO2,pH and PaO2/FiO2 had statistical difference between the death group and the survival group (P＜0.05).The binary classification Logistic regression analysis found that APACHE Ⅱ,LIPS,△PCO2,VD/VT were the risk factors.VD/VT on the 4th day was selected,its' cut off value was 0.62,and the sensitivity of the prognostic evaluation was 90.0 ％,the specificity was 95.5 ％.Conclusion The dead space fraction is an independent risk factor for the prognosis of ARDS patients,and VD/VT on 4th day could effectively identify the high-risk patients.

Study on severity and outcome in children with acute respiratory distress syndrome by measurement of alveolar dead space fraction / 中国小儿急救医学

Objective To investigate the role of alveolar dead space fraction(ADSF) on the severity and outcome among children with acute respiratory distress syndrome ( ARDS). Methods Totally 20 chil-dren with ARDS in early stage were enrolled in this prospective study from December 2016 to November 2017 in PICU of Shengjing Hospital of China Medical University. According to the OI value,the cases were devided into mild-moderate group(4≤OI <16,n ＝12)and severe group (OI≥16,n ＝8). According to 28-day hospital mortality,the cases were devided into survival group(n＝11) and death group (n＝9). The general situation,PaCO2,PetCO2,oxygenation index(P/F,O/I) and 28-day hospital mortality were recorded and evaluated,and ADSF was measured by ADSF＝( PaCO2-PetCO2)/PaCO2. These variables were ana-lyzed by using student′s t-test,non-parametric test and ROC curve,to analyze the relationship between the severity of ARDS and ADSF,and the predictive value of the prognosis. Results (1) Compared with the mild-moderate group,the OI and ADSF of the severe group were significantly higher,and the P/F was signif-icantly lower(P<0. 05). (2)Compared with the survival group,the OI and ADSF of the death group were significantly higher,and the P/F was significantly lower(P<0. 05). (3)The area under the ROC judged by ADSF was 0. 690 (P<0. 05). If 0. 338 was as the critical value to evaluate the prognosis,the sensitivity and specificity for judging death were 0. 704 and 0. 634,respectively. The AUC of predicting the prognosis with OI was 0. 720 (P<0. 05). If 0. 348 was as the critical value to predict death,the sensitivity and specificity were 0.551 and 0.797,respectively. The area under the ROC judged by P/F was 0.256(P > 0.05). Conclusion The ADSF on early stage is higher in children with severe ARDS than those with mild to moderate ARDS. The ADSF on early stage is higher in death group than that in survival group. ADSF is of guiding significance in the prognosis of ARDS.

Repair of the soft tissue defects combined dead space in lower extremities with the descending branch of lat-eral circumflex femoral artery chimeric perforator flap / 中华显微外科杂志

Objective To investigate the feasibility and clinical effects of chimeric perforator flap based on the descending branch of lateral circumflex femoral artery (d-LCFA) for reconstructing the three-dimensional tissue defect in lower extremities. Methods From May, 2008 to June, 2017, 79 cases of soft tissue defects with dead space were repaired by using a d-LCFA chimeric perforator flap, in which 33 cases of car accident trauma, 12 cases of chronic tibial osteomyelitis, 10 cases of plowing machine injury, 9 cases of chronic calcaneal osteomyelitis, 6 cases of falling injury, 5 cases of crushing injury, 3 cases of spoke injury, and 1 case of suppurative knee arthritis. These patients were accompany with different degrees of infection and dead space after radical debridement. The dead cavity was filled by muscular flap, and perforator flap covered the superficial wound. Recording the flap 's appearance, color, texture, osteomyelitis recurrence and the patient 's knee extension at 1, 3, 6, 9 and 12 months followed-up. Results Seventy-five flaps survived without complications, and the donor sites were closed directly. All patients had no post-operative hematoma or secondary infection. Vascular crisis occurred in 2 days after the operation in 4 flaps, 1 flap had an arterial crisis on the second-postoperative-day, and the flap was necrotic after surgical exploration. The deep cir-cumflex iliac artery chimeric perforator flap was used for repairing. Three flaps with venous crisis during 48 h after operation, in which 2 flaps survived eventually after surgical exploration, and another flap was necrosis and repaired by skin graft. The followed-up periods ranged from 3 months to 30 months (mean, 9.7 months). All flaps had satisfied with appearance and texture. There were no osteomyelitis recurrence and any ranges of motion limitations in the hip and knee joints of the operated leg. Conclusion The chimeric perforator flap with d-LCFA merely anastomosed 1 group vascular pedicle can make the dead space be filled and cover the superficial wound simultaneously. It is an ideal option for reconstructing the skin defect with dead space in lower extremity, which can improve the quality of restoration of recipient site and reduce the damage of donor site.

Transpulmonary pressure guided optimal positive end-expiratory pressure selection in patients with acute respiratory distress syndrome / 中华危重病急救医学

Objective To evaluate the value of transpulmonary pressure (Ptp) guided optimal positive end-expiratory pressure (PEEP) selection in patients with early acute respiratory distress syndrome (ARDS).Methods A prospective randomized self-control study was conducted.ARDS patients in the early stage (onset ≤3 days) undergoing intubation and mechanical ventilation admitted to intensive care unit (ICU) of Jiangsu Provincial Subei People's Hospital from December 2013 to December 2015 were enrolled.The PEEP level was regulated to 30 cmH2O (1 cmH2O =0.098 kPa) after recruitment maneuver,and then it was gradually decreased to 0 with lowering by 3 cmH2O every 5 minutes.The optimal PEEP was titrated by Ptp,lowest dead space fraction (VD/VT),highest static lung compliance (Cst),and optimal oxygenation,respectively.Parameters of respiratory mechanics and gas exchange were observed.Results Totally 28 patients with ARDS (including 17 male and 11 female) were included with the average age of (45 ± 12) years old,acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) score was 21 ± 9,oxygenation index (PaO2/FiO2) was (165 ± 76) mmHg (1 mmHg =0.133 kPa).① During decremental PEEP titration,Ptp was gradually decreased,and expiratory Ptp (Ptp-e) was more than zero [(1.3±0.3) cmH2O] when PEEP was (9.6 ± 2.3) cmH2O.Cst was initially improved until reaching a peak,and then deteriorated.Cst was highest [(50 ± 8) mL/cmH2O] when PEEP was (11.5 ± 2.4) cmH2O.PaO2/FiO2 reached the maximum [(312 ± 99) mmHg] at PEEP level of (18.0 ± 2.5) cmH2O.Compared with Ptp-e 3.00-5.99 cmH2O,PaO2/FiO2 was significantly decreased when Ptp-e became negative (all P ＜ 0.05).VD/VT was lowest (0.52 ±0.05) when PEEP was (10.1 ± 2.2) cmH2O.When compared with ventilation [inspiratory Ptp (Ptp-i) 0-2.99 cmH2O],it was significantly higher during high (Ptp-i ≥ 15 cmH2O,all P ＜ 0.05).② There were no statistically significant differences in the levels of optimal PEEP,Ptp-i and Ptp-e among Ptp,lowest VD/VT and highest Cst methods (all P ＞ 0.05),but they were significantly less than optimal oxygenation method (all P ＜ 0.05).Compared with baseline and the method of optimal oxygenation,Cst in other three PEEP titration methods including Ptp,lowest VD/VT and highest Cst was improved obviously (mL/cmH2O:46± 7,47±9,50± 8 vs.30± 8,35 ± 10,all P ＜ 0.05).PaO2/FiO2 (mmHg) in the method of Ptp and lowest VD/VT were higher than the baseline (252 ± 86,258 ± 72 vs.165 ± 76,both P ＜ 0.05),but significantly lower than that of optimal oxygenation method (312 ± 99,both P ＜ 0.05),and did not significantly differ from that of highest Cst (268± 85,both P ＞ 0.05).Compared with baseline and the method of optimal oxygenation,VD/Vr improved significantly in ventilated patients on PEEP targeting with Ptp and lowest VD/VT (0.53±0.05,0.52±0.05 vs.0.59±0.05,0.58±0.04,all P ＜ 0.05).Conclusion Titration the optimal PEEP level with the method of Ptp could promote collapse alveolar recruitment,improve oxygenation and lung compliance,decrease dead space ventilation,and will not cause alveolar excessive inflation in patients who undergoing mechanical ventilation with early ARDS.

Wound healing potential of flowers extracts of Woodfordia fruticosa Kurz.

Wound healing or repair is the body’s natural process of regenerating dermal and epidermal tissue. Woodfordia fruticosa Kurz (Family: Lythraceae) is used traditionally in wound healing by the tribals of Chhattisgarh district. However, there is a paucity of scientific data in support. In this study, we evaluated antimicrobial activity of petroleum ether, chloroform, ethanolic and aqueous extracts against a diverse range of gram +ve and gram -ve bacteria along with pathogenic fungi. The wound healing activity of ethanolic extract was also evaluated at dose levels of 250 and 500 mg/kg body wt in rats by excision, incision and dead space wound healing models along with histopathology of wound area of skin. The ethanolic extract showed potent wound healing activity, as evident from the increase in the wound contraction and breaking strength in dose-dependent manner. Treatment with ethanolic extract (250 and 500 mg/kg body wt) showed significant dose-dependently decrease in epithelization period and scar area. Hydroxyproline, hexuronic acid and hexosamine contents, the important constituents of extracellular matrix of healing were also correlated with the observed healing pattern. During early wound healing phase, pro-inflammatory cytokines TNF-α, IL-6 and anti-inflammatory cytokine IL-10 levels were found to be upregulated by the ethanolic extract treatment. The ethanolic extract exhibited a strong and broad spectrum antimicrobial activity, as compared to other extracts. It showed very low Minimum inhibitory concentration (MIC) values and inhibited the growth of E. coli, Staphylococcus aureus and Candida albicans in concentration of 2.5 µg/disc. Thus, the results of the present study demonstrated the strong wound healing potential and antimicrobial activities of W. fruticosa, flowers, supporting the folklore use of the plant by the tribal people of Chhattisgarh district.

The changes of pulmonary dead space, shunt and gas exchange after thromboembolism of lungs in swine / 中华急诊医学杂志

Objective To investigate the alterations of pulmonary dead space,pulmonary shunt fraction (Qs/Qt) and gas exchange after thromboembolism of lungs in swines and to evaluate the mechanism in respect of pathophysiology and implication.Methods Swine model of pulmonary thromboembolism was made by injection of thrombus into pulmonary artery.Eight swine were used for study of physiologic dead space (VDphy),alveoli dead space (VDalv),airway dead space (VDaw),Qs/Qt,pulmonary arterial pressure (PAP),oxygen partial pressure in arterial blood (PaO2 ),carbon dioxide partial pressure in arterial blood (PaCO2 ),alveolar-arterial O2 gradient (PA-aDO2) determined 30 min before thromboembolism and 0 min,30 min,60 min,120 min after thromboembolism.Results The results showed that VDphy,VDalv,Qs/Qt,PAP,PA-aDO2 increased markedly after thromboembolism in comparison with pre-thromboembolism (P ＜ 0.01 ),while PaO2 declined significantly (P ＜ 0.01 ),and the differences in VDaw and PaCO2 were not significant ( P ＞ 0.05 ).SNK test showed that VDphy and VDalv declined to be smaller at 60 min,120 min than those at 30 min,and PAP declined to be lower at 30 min,60 min,120 min than that at 0 min.Other variables did not change at different intervals after thromboembolism.Hemodynamics did not change significantly after embolization.Conclusions After pulmonary thromboembolism,a various of changes in pathophysiology happened such as increase in dead space,Qs/Qt and PA-aDO2 and decrease in PaO2,but PaCO2 did not change.

Prognostic value of the pulmonary dead-space fraction in patients during the early phases of acute respiratory distress syndrome / 中华急诊医学杂志

ObjectiveTo evaluate the association between alveolar dead space fraction and the prognosis of patients with acute respiratory syndrome in the early phase ( ＜ 3 days).MethodsTwentythree patients with ARDS were enrolled in this study.The VD/VT was measured by the single breath test of CO2 (SBT-CO2).The age,heart rate,mean arterial pressure,APACHE Ⅱ,Murray lung injury score,functional residual capacity ( FRC ),PaO2/FiO2,tidal volume,airway plateau pressure ( Pplat ),static pulmonary compliance (Cst),28-day mortality were recorded.ResultsThe alveolar dead-space fraction was markedly elevated (0.59 ±0.06) and the mean FRC was markedly decreased (1643 ±409) ml in the early phase of ARDS.The mortality of 28 days was 52.2％.The mean dead-space fraction was significantly higher in non-survived patients than that in survival [(0.64 ± 0.08 ) vs.(0.53 ±0.04 )].VD/VT was correlated significantly with Murray lung injury score ( r=0.464,P =0.026).The area under the ROC curve for dead space fraction was 0.867,with sensitivity of 83％,and specificity of 82％.Conclusions Increased alveolar dead-space fraction of patients in the early phases of ARDS is associated with greater risk of death.

The effect of a pediatric heat and moisture exchanger on dead space in healthy pediatric anesthesia / 대한마취과학회지

BACKGROUND: Heat and moisture exchangers (HME) are often used to maintain humidity of breathing circuits during anesthesia. It is also known to increase dead space ventilation in respiratory distress syndromes. However, the effect of a pediatric HME in healthy pediatric patients has not yet been clarified. The purpose of this study was to evaluate the effect of a pediatric HME on dead space in healthy pediatric patients during anesthesia. METHODS: 20 ASA physical class I pediatric patients, without respiratory impairment, who underwent elective surgery for inguinal hernia or hydrocele with general anesthesia were enrolled. Fifteen minutes after ventilation with and without pediatric HME (internal volume of 22 ml), hemodynamic variables, end tidal CO2, minute volume and airway pressure were measured, and arterial blood sampling was conducted simultaneously. RESULTS: The removal of pediatric HME decreased PaCO2 significantly from 46.1 +/- 6.9 mmHg to 37.9 +/- 4.3 mmHg (P < 0.001) and increased the pH from 7.32 to 7.37 (P < 0.001). The differences between PaCO2 with and without HME (Delta PaCO2) were significantly correlated with weight (P < 0.001, beta1 = -0.749) and age (P = 0.002, beta1 = -0.623). CONCLUSIONS: The use of a pediatric HME significantly increased PaCO2 in healthy pediatric patients that was inversely proportional to weight and age. The use of pediatric HME should be carefully considered in small pediatric patients.

The influence of inspired oxygen fraction for the diagnosis of acute respiratory distress syndrome / 中华急诊医学杂志

Objective To investigate the influence of inspired oxygen fraction (FiO2) on the ratio of PaO2/FiO2(P/F) during the implementation of lung protective ventilation strategy in patients with acute respiratory distress syndrome(ARDS) in order to unravel its clinical significance. Method This was a prospective study of 16 selected patients with ARDS treated with mechanical ventilation ( MV ) to get ratio of P/F in range of 100 to 200 by PEEP≥5 cmH2O and high inspired oxygen. After lung recruitment maneuvers by BiPAP with high pressure (PH) of 40 cmH2O for40 s, the MV was maintained the basic requirement for stabilizing the patients for 30 minutes. A series of FiO2 were set at fractions of 0.5,0.6,0.7,0.8,0.9 and 1in random sequence, and the changes of respiratory mechanics, blood gas and hemodynamics under the different concentrations of FiO2 were analyzed by using SPSS version 13.0 software. Results ( 1 ) The ratio of P/F increased as FiO2 increased, and it's significant as FiO2 increased to 0.7 or above. As the fractions of FiO2 were set at 0.5 and 1. O, the ratios of P/F changed in 24.70% ± 23.36% respectively. ( 2 ) Of them,6 patients ( 37.5% ) treated with FiO2 set at 0.5 had the ratio of P/F ＜ 200, and the fraction of FiO2 was increased to 1.0, the P/F ＞ 200. (3) FiO2 and Qs/Qt were negatively correlated ( r = - 0.390, P = O. 027 ),the higher inspired oxygen fraction, the lower shunt. When the fractions of FiO2 were set at 0.5 and 1.0 ,there was a positive correlation between △Qs/Qt and △P/F( r = 0.82, P = 0.005 ). Conclusions The inspired oxygen fraction affects the ratio of P/F, which may be resulted from shunt and it may influence the diagnosis of ARDS.

Dead space guided positive end-expiratory pressure in patients with acute respiratory distress syndrome / 中华内科杂志

ObjectiveTo evaluate the value of dead space fraction (VD/VT) guided positive end expiratory pressure ( PEEP ) in acute respiratory distress syndrome ( ARDS ).Methods Twenty-three intubated and mechanically ventilated patients with early ARDS were enrolled in the study.PEEP was titrated by lowest VD/VT.Parameters of oxygenation and respiratory mechanics were observed.Results PEEP titrated by lowest VD/VT and highest static lung compliance ( CLst ) ( P ＞ 0.05 ) respectively,were lower than PEEP titrated by optimal oxygenation ( P ＜ 0.05),but there was no significant difference between lowest VD/VT and highest Ctst method.The VD/VT that ventilated on PEEP titrated by the lowest VD/VT decreased than its basal level.There was no difference significantly between the VD/VT that ventilated on PEEP elected by the other two methods with basal level ( P ＞ 0.05 ).The the ratio of arterial PO2 to the inspired oxygen fraction (PaO2/FiO2)ratios improved significantly than the baseline values in three ventilation strategies,and that ventilated on PEEP targeting the lowest VD/VT was lower than PEEP targeting optimal oxygenation.The plateau airway pressure that ventilated on PEEP targeting optimal oxygenation was higher than the other two methods.The functional residual capacity (FRC) of patients ventilated by PEEP targeting optimal oxygenation was increased than the lowest VD/VT and maximum CLst.Conclusions VD/VT could be one of the methods to titrate the optimal PEEP in patients with early ARDS.Optimal PEEP targeting the highest compliance in conjunction with the lowest dead space fraction indicated a maximumamount of effectively expanded alveoli.

Effect of inhaled low density nitric oxyde in pig' s pulmonary thromboembolism / 中华急诊医学杂志

Objective To investigate the mechanism and significance of low concentration nitric oxide (NO) inhalation in the treatment of pulmonary thromboembelism in swine. Method The pulmonary thromboem-bolism(PTE) model was made in 15 healthy infantile swines which were subsequently assigned to either control group (n = 8) or NO group (n = 7). Swines of the control group were not treated with any medicine, while 10 ppm of NO was administered by continuous inhalation for 2 hours to swines of NO group. Volume of physiological dead space (VDphy), volume of alveolar dead space (VDalv), intrapulmonary shunt (Qs/Qt), mean pulmonary arterial pressure (PAP), systolic blood pressure (SBP), heart rate (HR), cardiac output (CO), arterial blood pH (pH), arterial partial pressure of carbon dioxide (PaCO2) and arterial partial pressure of oxygen (PaO2) were measured 30 min before and 0 min, 30 min, 60 min, 120 min and 180 min after establishment of VIE. Results The post-FIE VDphy, VDalv, Qs/Qt and PAP in both groups increased markedly after PTE compared with the cor-responding pre-PTE measurements (P < 0.01). Post-FIE PaO2 of both groups decreased significandy (P <0.05 and P <0.01), while significance difference was found between pre- and post-PTE HR, SBP, CO, pH or PaCO2 in neither groups (P > 0.05). Both post-PTE PAP and VDalv in NO group were markedly lower(P <0.05 and P <0.01) and beth PaCO2 and PaO2 were much higher than those of the control group (P <0.05). No signi-fieant difference were found in other measurements between two groups. Conclusions Pulmonary arterial pressure may be lowered, alveoli dead space may be reduced and PaCO2 increased by low concentration NO inhalation for the treatment of PIE without decline in haemodynamic status.

Alveolar Dead Space Ventilation Ratio as an Early Predictor of Acute Respiratory Distress Syndrome in Severe Sepsis and Septic Shock Patients

PURPOSE: Examine the clinical utility of the alveolar dead space ventilation ratio (VdA/VT) as a predictor of acute respiratory distress syndrome (ARDS) in severe sepsis and septic shock patients. METHODS: A prospective observation study was done for 113 patients with severe sepsis and septic shock seen at the emergency department of a university hospital from January 2005 to June 2007. Therapies in the emergency department included central venous access, antibiotics, fluid resuscitation, mechanical ventilation, vasopressors and inotropes as required. The major outcome assessed was the development of ARDS within 3 days after admission. Hemodynamic variables, arterial blood gas values, serum lactate concentration, and estimated VdA/VT were evaluated at presentation (0 hour) and at 4 hours. Briefly the estimated VdA/VT was calculated by dividing the deference of the arterial CO2 and end-tidal CO2 by the PaCO2 value. Data were presented as median+/-SD. RESULTS: ARDS developed in twenty-two patients (<24 hours: 17 persons, 24~48 hour: 4 persons, 48~72 hour: 1 person). Patients who developed ARDS had significantly higher age, higher frequency of pneumonia, greater use of mechanical ventilation and dubutamine during ED therapy, and higher sepsis related organ failure assessment (SOFA) scores. The in-hospital mortality of patients with ARDS was significantly higher than that of patients without ARDS (54.5% vs. 15.4%, p<0.001). Pneumonia, use of dobutamine during ED therapy, and VdA/VT at 4 hours were independent predictive factors for the development of ARDS. The area under the receiving operating characteristic curve for predicting ARDS was 0.891 (95% CI; 0.808-0.980) with a value of VdA/VT at 4 hours. The cut off value of VdA/VT at 4 hours was 0.25 (sensitivity 81.8%, specificity 93.3%). At 4 hours, patients with VdA/VT equal to or greater than 0.25 under resuscitation showed a high rate of fluid and high inhospital mortality when compared with patients with VdA/VT <0.25 (CVP<10 cmH2O; 37.5% vs. 16.9%, p=0.047, mortality; 75.0% vs. 4.5%, p<0.001). In patients with VdA/VT equal to or greater than 0.25 at 0 hour, patients without ARDS showed significantly improvement of VdA/VT at 4 hours. CONCLUSION: VdA/VT was found to be an independent predictive variables for ARDS in the early in-hospital period. Improvement of VdA/VT through early goal directed therapy in emergency department may decrease the development of ARDS in severe sepsis and septic shock patients.

End Tidal CO2 Derived Variable as a Prognostic Factor in Post Resuscitated Cardiac Arrest Patients

PURPOSE: End-tidal carbon dioxide (ETCO2) reflects pulmonary perfusion and ventilation of resuscitated cardiac arrest patients. Single use of ETCO2 has some limitations in predicting outcomes of cardiac arrest. We hypothesized the dead space ventilation ratio (Vdt/Vt) using arterial CO2 and ETCO2 difference (Pa-etCO2) can be used as a better prognostic indicator of survival in resuscitated cardiac arrest patients. METHODS: 94 patients were cardiac arrest in emergency department from January 2004 to october 2005. Patients were intubated in the emergency department and treated using the standard advanced cardiac life support protocol. 48 patients were resuscitated following cardiac arrest. Their ETCO2 were evaluated by using mainstream capnography. ETCO2 and simultaneously, blood gas studies were evaluated within 1 hour following return of spontaneous circulation (ROSC). 17 Patients were excluded because they had chronic pulmonary disease or they were cardiac arrest after cerebrovascular accident. RESULTS: There was no difference in mean age, arrest rhythm, systolic blood pressure, and base excess between patients that were discharged alive and patients that died in the hospital. Arterial pH of patients expired within 24 hours was significantly lower than that of survivors. The ETCO2 following ROSC averaged 19.7 +/- 10.73 mmHg in cases of hospital death with ROSC 24 hours and 26.2 +/- 5.22 mmHg in survivors (p=0.050). The VdA/Vt averaged 0.20 +/- 0.087 mmHg in alive discharges, 0.59 +/- 0.187 mmHg in hospital death with ROSC 24 hours (p=0.000). CONCLUSION: This study showed that high P(a-et)CO2 and high VdA/Vt suggest poor outcomes in arrest patients with ROSC. If future studies validate this model, the use of VdA/Vt that compare to ETCO2 may be a more useful adjunct in assessing the outcomes of cardiac arrest..