Dead Space Volume Research Articles

İndirekt Kalorimetrede Kullanılan Aparatların Ölü Boşluk Hacimlerinin Hatalı Girişinin Enerji Tüketimi Ölçümüne Etkisi

İndirekt Kalorimetrede Kullanılan Aparatların Ölü Boşluk Hacimlerinin Hatalı Girişinin Enerji Tüketimi Ölçümüne Etkisi

A model-based approach to interpreting multibreath nitrogen washout data.

The multibreath nitrogen washout (MBNW) test, as it is currently practiced, provides parameters of potential physiological significance that are derived from the relationship between the volume-normalized Phase III slope of the exhaled nitrogen fraction ([Formula: see text]) vs. the cumulative change in lung volume (V). Reliable evaluation of these parameters requires, however, that the subject breathe deeply and evenly, so that Phase III can be clearly identified in every breath. This places a burden on the test subject that may prove troublesome for young children and those with lung disease. Furthermore, the determination of the slope of Phase III requires that a decision be made as to when Phase II ends and Phase III begins. In an attempt to get around these methodological limitations, we develop here an alternative method of analysis based on a multicompartment model of the lung that accounts for the entire exhaled nitrogen profile, including Phases I, II, and III. Fitting this model to [Formula: see text] and V measured during a MBNW provides an estimate of the coefficient of variation of specific ventilation, as well as functional residual capacity, dead space volume, and a parameter that reflects structural asymmetry at the acinar level in the lung. In the present study, we demonstrate the potential utility of this modeling approach to the analysis of MBNW data. NEW & NOTEWORTHY The multibreath nitrogen washout test potentially provides important physiological information about regional ventilation heterogeneity throughout the lung, but the conventional analysis requires the subject to breathe deeply and regularly, which is not always practical. We have developed a model-based analysis method that avoids this limitation and that also provides measures of functional residual capacity and dead space volume, thereby expanding the applicability and scope of the method.

Evaluation of Specific Administering Devices for Antineoplastic Drugs Compounded in Syringes in Paediatry: Methodology Proposal.

Purpose The aims of this study were to propose a simple methodology to assess the rinsing volume of syringe extension sets and to compare several marketed devices. Methods A UV-spectrophotometry assay using quinine hydrochloride as drug substitute was developed. Quinine concentration ranged from 20 to 200 µg/ml. The assay was validated with the accuracy profile method and tested on five different assemblies (device+extension sets) with different dead-space volumes (1.28-2.80 ml) and at two different quinine concentrations (0.3 and 8.0 mg/ml). Rinsing was performed stepwise with water for injection until reaching an undetectable quinine concentration. After fitting the data with a Weibull model, assemblies were compared with an ANOVA performed on ranks (GraphPad, La Jolla, USA). Results The within-day and between-day precision ranges were 0.39-0.81 and 0.48-0.84%, respectively. The lower limit of quantification was 4.26 µg/ml. The volume required to completely rinse the infusion line was different according to the initial drug concentration and to the device assessed: from 6 to 10 ml for a low quinine concentration and from 7 to 17 ml for a high quinine concentration. Conclusion This study shows that a simple, cheap and easy-to-use methodology may be used to assess the rinsing volume of syringe extension sets. The rinsing volume is different according to the tested device.

Official ERS technical standards: Global Lung Function Initiative reference values for the carbon monoxide transfer factor for Caucasians.

There are numerous reference equations available for the single-breath transfer factor of the lung for carbon monoxide (T LCO); however, it is not always clear which reference set should be used in clinical practice. The aim of the study was to develop the Global Lung Function Initiative (GLI) all-age reference values for T LCOData from 19 centres in 14 countries were collected to define T LCO reference values. Similar to the GLI spirometry project, reference values were derived using the LMS (lambda, mu, sigma) method and the GAMLSS (generalised additive models for location, scale and shape) programme in R.12 660 T LCO measurements from asymptomatic, lifetime nonsmokers were submitted; 85% of the submitted data were from Caucasians. All data were uncorrected for haemoglobin concentration. Following adjustments for elevation above sea level, gas concentration and assumptions used for calculating the anatomic dead space volume, there was a high degree of overlap between the datasets. Reference values for Caucasians aged 5-85 years were derived for T LCO, transfer coefficient of the lung for carbon monoxide and alveolar volume.This is the largest collection of normative T LCO data, and the first global reference values available for T LCO.

Spirometry and volumetric capnography in lung function assessment of obese and normal‐weight individuals without asthma

ObjectiveTo analyze and compare lung function of obese and healthy, normal‐weight children and adolescents, without asthma, through spirometry and volumetric capnography. MethodsCross‐sectional study including 77 subjects (38 obese) aged 5–17 years. All subjects underwent spirometry and volumetric capnography. The evaluations were repeated in obese subjects after the use of a bronchodilator. ResultsAt the spirometry assessment, obese individuals, when compared with the control group, showed lower values of forced expiratory volume in the first second by forced vital capacity (FEV1/FVC) and expiratory flows at 75% and between 25 and 75% of the FVC (p<0.05). Volumetric capnography showed that obese individuals had a higher volume of produced carbon dioxide and alveolar tidal volume (p<0.05). Additionally, the associations between dead space volume and tidal volume, as well as phase‐3 slope normalized by tidal volume, were lower in healthy subjects (p<0.05). These data suggest that obesity does not alter ventilation homogeneity, but flow homogeneity. After subdividing the groups by age, a greater difference in lung function was observed in obese and healthy individuals aged >11 years (p<0.05). ConclusionEven without the diagnosis of asthma by clinical criteria and without response to bronchodilator use, obese individuals showed lower FEV1/FVC values and forced expiratory flow, indicating the presence of an obstructive process. Volumetric capnography showed that obese individuals had higher alveolar tidal volume, with no alterations in ventilation homogeneity, suggesting flow alterations, without affecting lung volumes.

Volumetric capnography: abilities in practical pulmonology

The aim of this review was to analyze abilities of a novel diagnostic method intended to measure the lung function. Volumetric capnography is one of the most promising tools for assessing pulmonary function. This method reflects CO 2 elimination pattern at the exhaled air volume. Changes in CO 2 portion at the tidal volume are related to the integrated evaluation of the respiratory function and could be expressed as the following parameters: emphysema index, the dead space volume, phases 2 and 3 slopes, etc. Possible use of the volumetric capnography for diagnosis of chronic obstructive pulmonary disease, asthma, emphysema, and other respiratory diseases is discussed in the article. This method is simple, non-invasive, and safe. Diagnostic value of the volumetric capnography needs further investigation in order to implement this method in clinical practice.

Minimally invasive estimation of ventricular dead space volume through use of Frank-Starling curves.

This paper develops a means of more easily and less invasively estimating ventricular dead space volume (Vd), an important, but difficult to measure physiological parameter. Vd represents a subject and condition dependent portion of measured ventricular volume that is not actively participating in ventricular function. It is employed in models based on the time varying elastance concept, which see widespread use in haemodynamic studies, and may have direct diagnostic use. The proposed method involves linear extrapolation of a Frank-Starling curve (stroke volume vs end-diastolic volume) and its end-systolic equivalent (stroke volume vs end-systolic volume), developed across normal clinical procedures such as recruitment manoeuvres, to their point of intersection with the y-axis (where stroke volume is 0) to determine Vd. To demonstrate the broad applicability of the method, it was validated across a cohort of six sedated and anaesthetised male Pietrain pigs, encompassing a variety of cardiac states from healthy baseline behaviour to circulatory failure due to septic shock induced by endotoxin infusion. Linear extrapolation of the curves was supported by strong linear correlation coefficients of R = 0.78 and R = 0.80 average for pre- and post- endotoxin infusion respectively, as well as good agreement between the two linearly extrapolated y-intercepts (Vd) for each subject (no more than 7.8% variation). Method validity was further supported by the physiologically reasonable Vd values produced, equivalent to 44.3–53.1% and 49.3–82.6% of baseline end-systolic volume before and after endotoxin infusion respectively. This method has the potential to allow Vd to be estimated without a particularly demanding, specialised protocol in an experimental environment. Further, due to the common use of both mechanical ventilation and recruitment manoeuvres in intensive care, this method, subject to the availability of multi-beat echocardiography, has the potential to allow for estimation of Vd in a clinical environment.

Spirometry and volumetric capnography in lung function assessment of obese and normal-weight individuals without asthma

ObjectiveTo analyze and compare lung function of obese and healthy, normal-weight children and adolescents, without asthma, through spirometry and volumetric capnography. MethodsCross-sectional study including 77 subjects (38 obese) aged 5–17 years. All subjects underwent spirometry and volumetric capnography. The evaluations were repeated in obese subjects after the use of a bronchodilator. ResultsAt the spirometry assessment, obese individuals, when compared with the control group, showed lower values of forced expiratory volume in the first second by forced vital capacity (FEV1/FVC) and expiratory flows at 75% and between 25 and 75% of the FVC (p<0.05). Volumetric capnography showed that obese individuals had a higher volume of produced carbon dioxide and alveolar tidal volume (p<0.05). Additionally, the associations between dead space volume and tidal volume, as well as phase-3 slope normalized by tidal volume, were lower in healthy subjects (p<0.05). These data suggest that obesity does not alter ventilation homogeneity, but flow homogeneity. After subdividing the groups by age, a greater difference in lung function was observed in obese and healthy individuals aged >11 years (p<0.05). ConclusionEven without the diagnosis of asthma by clinical criteria and without response to bronchodilator use, obese individuals showed lower FEV1/FVC values and forced expiratory flow, indicating the presence of an obstructive process. Volumetric capnography showed that obese individuals had higher alveolar tidal volume, with no alterations in ventilation homogeneity, suggesting flow alterations, without affecting lung volumes.

Minimally invasive, patient specific, beat-by-beat estimation of left ventricular time varying elastance

BackgroundThe aim of this paper was to establish a minimally invasive method for deriving the left ventricular time varying elastance (TVE) curve beat-by-beat, the monitoring of which’s inter-beat evolution could add significant new data and insight to improve diagnosis and treatment. The method developed uses the clinically available inputs of aortic pressure, heart rate and baseline end-systolic volume (via echocardiography) to determine the outputs of left ventricular pressure, volume and dead space volume, and thus the TVE curve. This approach avoids directly assuming the shape of the TVE curve, allowing more effective capture of intra- and inter-patient variability.ResultsThe resulting TVE curve was experimentally validated against the TVE curve as derived from experimentally measured left ventricular pressure and volume in animal models, a data set encompassing 46,318 heartbeats across 5 Piétrain pigs. This simulated TVE curve was able to effectively approximate the measured TVE curve, with an overall median absolute error of 11.4% and overall median signed error of −2.5%.ConclusionsThe use of clinically available inputs means there is potential for real-time implementation of the method at the patient bedside. Thus the method could be used to provide additional, patient specific information on intra- and inter-beat variation in heart function.

A Modeling Study on Inspired CO2 Rebreathing Device for Sleep Apnea Treatment by Means of CFD Analysis and Experiment

We present the device design, simulation, and measurement results of a therapy device that potentially prevents sleep apnea by slightly increasing inspired CO2 through added dead space (DS). The rationale for treatment of sleep apnea with CO2 manipulation is based on two recently reported premises: (i) preventing transient reductions in PaCO2 will prevent the patient from reaching their apneic threshold, thereby preventing “central” apnea and instabilities in respiratory motor output; and (ii) raising PaCO2 and end-tidal CO2, even by a minimal amount, provides a strong recruitment of upper airway dilator muscles, thereby preventing airway obstruction. We have also provided the simulation results, obtained from solving the Navier–Stokes (NS) equations within the device volume. Therein, the NS equations are coupled with a convection–diffusion equation that represents the transport of CO2 in the device, thus enabling the transient simulation of CO2 propagation. Using this procedure, a prototype of variable volume dead space reservoir device was designed. Volumetric factors influencing carbon dioxide increases in the added reservoir (open-ended DS) were investigated. The maximum/minimum amount of CO2 concentration were obtained for the maximum/minimum device volume; 3.4 and 2.4 mol/m3 for the DS volumes of 1.2 and 0.5 × 10−3 m3, respectively. In all case studies, the CO2 buildup reached a plateau after approximately 20 breathing cycles. The experimental measurement results are in agreement with the simulation and numerical results obtained using the proposed simplified modeling technique, with a maximum relative error of 3.5%.

Критические времена воздействия моноксида углерода на человека при пожаре в помещении

The aim of this work was to create the mathematical model for calculation of the carboxyhemoglobin concentration in the human blood in case of fire. Tests were conducted in conditions of variable CO density, typical for the initial stage of indoor fire, and increased pulmonary ventilation rate. It is offered the criteria for determination of the critical values of fire duration under the terms of safe evacuation and people rescue. The methods of theoretical analysis of the content of carboxyhemoglobin in the human blood and calculation of the carbon monoxide (CO) concentration, in conditions of fire in premises, were used during the experiment. The mathematical model was created taking into account the concentration of CO in the inhaled air, the mass of hemoglobin in the blood, the pulmonary ventilation rate, the volume of respiratory dead space and the CO exposure time. Critical time of safe evacuation for people under the effects of CO is accepted when the content of carboxyhemoglobin in the blood reaches the 20 % by mass (minor poisoning). Critical time from the initial stage of fire and until the moment when people, which stay in premises without protection means against CO (respirators, gas masks, self-rescuers, etc.), and, with high probability, are unable to leave the premises independently, is accepted when the concentration of carboxyhemoglobin in the blood reaches the 50 % by mass (moderate poisoning). The model premises were in the form of parallelepiped with dimensions (m): 4´5´3, 4´5´6 and 24´12´3. As combustible materials there were used the wood building materials, PVC sheath of cables and transformer oil. The results of numerical experiments on determination of the carboxyhemoglobin concentration using the analytical solution of the integral calculation model for the thermal and gas dynamics of fire are presented. The estimated values of CO exposure intervals prior to various degrees of human intoxication are obtained. The comparison of critical durations of fire (considering CO effects), obtained using proposed model and existing approach, is made. The critical duration of fire, obtained using proposed model, was significantly greater than the corresponding value determined by existing methods (for example, in case of burning of the transformer oil in the room with dimensions of 4´5´3 m). The main conclusion is that existing scientific and regulatory literature contains the calculation methods for critical duration of fire, considering CO effects, which may lead to qualitatively and quantitatively wrong results. The proposed criteria for determination of the critical values of CO exposure time and the calculation methods for the content of carboxyhemoglobin allow defining the time of safe evacuation and people rescue more reasonably than existing approach.

Noninvasive monitoring of CO2 during polysomnography: a review of the recent literature.

Sleep-related breathing disorders are complex conditions that require the integration of clinical and sleep laboratory findings to support a diagnosis. Analysis of carbon dioxide (CO2) levels during sleep provides important additional information to the clinician that is not obtained from other polysomnographic indices, and that may have a direct impact on both diagnosis and patient mortality. Although arterial blood gas (ABG) is considered the gold standard for assessing PaCO2 levels, there are numerous drawbacks. Noninvasive methods for PaCO2 estimation include end-tidal and transcutaneous monitoring, which allow for continuous monitoring of trends. Review of the recent literature suggests that transcutaneous methods correlate strongly with PaCO2 levels and can provide an accurate surrogate in replacement of ABGs. End-tidal methods provide breath to breath information that can be used to assess hypoventilation; however, they have more variability, especially in patients with increased dead space and small tidal volumes. To date, however, there are limited studies investigating noninvasive CO2 monitoring during sleep. Given the benefits of CO2 monitoring and the importance of assessing for hypercapnia, noninvasive continuous CO2 monitoring should be considered for all patients undergoing polysomnography.

Case Studies in Physiology: The Case of the Giant Giraffe.

N/A.

ВЛИЯНИЕ СРЕДСТВ ГИПЕРКАПНИЧЕСКОЙ ГИПОКСИИ НА ФУНКЦИОНАЛЬНУЮ И СПЕЦИАЛЬНУЮ ФИЗИЧЕСКУЮ ПОДГОТОВЛЕННОСТЬ ЮНЫХ ДЗЮДОИСТОВ

Aim was to assess the efficiency of Karbonik respiratory trainer developed by professor Kulikov in 15-16-year-old judokas’ training. Materials and Methods. The study involved two groups of first- and second-category judokas. Each group included 10 athletes of approximately the same physical fitness level. Training of the experimental group used hypoxic hypercapnic gas mixture formed by the above mentioned respiratory trainer. Response of the functional systems to the training program was assessed based on the changes in hypoxic index, timed inspiratory and expiratory capacities, lung capacity, and heart rate; as well as tests reflecting the levels of special physical fitness and sport performance. Results. It was revealed that regular respiratory training via additional volume of dead air breath provided by Karbonik respiratory trainer system contributed to adaptation of a young judoka’s body to hypoxia and hypercapnia, which, in its turn, resulted in improvement of special physical fitness and sport performance. Conclusion. The respiratory trainer due to additional dead space volume creates the conditions of moderate hypoxia and hypercapnia which have a combined positive effect on the increase of special physical fitness and sport performance in young judokas.

Generalized estimation of the ventilatory distribution from the multiple-breath nitrogen washout.

BackgroundThis work presents a generalized technique to estimate pulmonary ventilation-to-volume (v/V) distributions using the multiple-breath nitrogen washout, in which both tidal volume (VT) and the end-expiratory lung volume (EELV) are allowed to vary during the maneuver. In addition, the volume of the series dead space (vd), unlike the classical model, is considered a common series unit connected to a set of parallel alveolar units.MethodsThe numerical solution for simulated data, either error-free or with the N2 measurement contaminated with the addition of Gaussian random noise of 3 or 5 % standard deviation was tested under several conditions in a computational model constituted by 50 alveolar units with unimodal and bimodal distributions of v/V. Non-negative least squares regression with Tikhonov regularization was employed for parameter retrieval. The solution was obtained with either unconstrained or constrained (VT, EELV and vd) conditions. The Tikhonov gain was fixed or estimated and a weighting matrix (WM) was considered. The quality of estimation was evaluated by the sum of the squared errors (SSE) (between reference and recovered distributions) and by the deviations of the first three moments calculated for both distributions. Additionally, a shape classification method was tested to identify the solution as unimodal or bimodal, by counting the number of shape agreements after 1000 repetitions.ResultsThe accuracy of the results showed a high dependence on the noise amplitude. The best algorithm for SSE and moments included the constrained and the WM solvers, whereas shape agreement improved without WM, resulting in 97.2 % for unimodal and 90.0 % for bimodal distributions in the highest noise condition.ConclusionsIn conclusion this generalized method was able to identify v/V distributions from a lung model with a common series dead space even with variable VT. Although limitations remain in presence of experimental noise, appropriate combination of processing steps were also found to reduce estimation errors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12938-016-0213-y) contains supplementary material, which is available to authorized users.

Recovering Infectious HIV from Novel Syringe-Needle Combinations with Low Dead Space Volumes.

This study determines if detachable syringe-needle combinations redesigned to reduce their dead space volume may substantially reduce the burden of exposure to infectious HIV among people who inject drugs. Two novel, low dead space (LDS) syringe-needle designs-one added a piston to the plunger (LDS syringe) and the other added a filler to the needle (LDS needle) to reduce their dead space-were compared to standard detachable needle-syringe combinations and to syringes with fixed needles. LDS and standard syringes attached to LDS and standard needles of 23-, 25-, and 27-gauge size were contaminated with HIV-infected blood in the laboratory. The proportion of syringe-needle combinations containing infectious HIV was analyzed after syringes were (1) stored up to 7 days at 22°C or (2) rinsed with water. Detachable syringes attached to 25-gauge needles yielded comparable proportions of syringes with infectious HIV, whether the needle was standard or LDS. Among needles of greater diameter (23 gauge), LDS needles tended to reduce recoverable HIV to a greater extent than standard needles. Syringes with fixed needles showed superior results to LDS syringes attached to needles of equivalent diameter and were less likely to get clogged by blood. Detachable LDS syringe-needle designs must be recommended with caution since they still pose potential risk for HIV transmission. Distribution of LDS syringes and needles must be accompanied by recommendations and instructions for their proper rinsing and disinfection in order to reduce viral burden and chances of needle clogging.

Inhalation sedation with the ‘Anaesthetic Conserving Device’ for patients in intensive care units: A literature review

Background. The Anaesthetic Conserving Device is a modified heat and moisture exchanger that enables the application of inhalation sedation with existing ventilators in intensive care units. The following review describes the advantages of inhalation sedation using the Anaesthetic Conserving Device in comparison to standard intravenous sedation for patients in intensive care units and highlights the technical aspects of its functioning.Methods. The literature search was limited to PubMed, Sage Journals and CINAHL databases, using the terms »anaesthetic conserving device«, »volatile anaesthetic reflection filter«, »AnaConDa« independently and in connection with the terms »sedation« and intensive care unit«. Included are articles published up until December 2014.Results. Use of inhalation sedation with the Anaesthetic Conserving Device enables faster transition to spontaneous breathing and a shorter awakening time than with intravenous sedation. Even short-term inhalation sedation of patients after open heart procedures has a cardioprotective effect and reduces troponin T values. Despite increased concentrations of inorganic fluoride in serum after sevoflurane exposure, no clinical studies to date have shown its nephrotoxic effect, even after long-term (48 h) sedation. The Anaesthetic Conserving Device is accurate in maintaining target values of volatile anaesthetics. However, increased dead space volume was found in several studies, exceeding the internal volume of the Anaesthetic Conserving Device.Conclusion. Results to date show that inhalation sedation with the Anaesthetic Conserving Device may be an effective and safe alternative to existing protocols of intravenous sedation for patients requiring intensive treatment.

Survival of Hepatitis C Virus in Syringes Is Dependent on the Design of the Syringe-Needle and Dead Space Volume.

BackgroundMany people who inject drugs (PWID) use syringes with detachable needles, which have high dead space (HDS). Contaminated HDS blood may substantially contribute to the transmission of HIV, hepatitis C (HCV), and other blood-borne viruses within this population. Newly designed low dead space (LDS) syringe-needle combinations seek to reduce blood-borne virus transmission among PWID. We evaluated the infectivity of HCV-contaminated residual volumes recovered from two LDS syringe-needle combinations.MethodsWe tested two different design approaches to reducing the dead space. One added a piston to the plunger; the other reduced the dead space within the needle. The two approaches cannot be combined. Recovery of genotype-2a reporter HCV from LDS syringe-needle combinations was compared to recovery from insulin syringes with fixed needles and standard HDS syringe-needle combinations. Recovery of HCV from syringes was determined immediately following their contamination with HCV-spiked plasma, after storage at 22°C for up to 1 week, or after rinsing with water.ResultsInsulin syringes with fixed needles had the lowest proportion of HCV-positive syringes before and after storage. HCV recovery after immediate use ranged from 47%±4% HCV-positive 1 mL insulin syringes with 27-gauge ½ inch needles to 98%±1% HCV-positive HDS 2 mL syringes with 23-gauge 1¼ inch detachable needles. LDS combinations yielded recoveries ranging from 65%±5% to 93%±3%. Recovery was lower in combinations containing LDS needles than LDS syringes. After 3 days of storage, as much as 6-fold differences in virus recovery was observed, with HCV recovery being lower in combinations containing LDS needles. Most combinations with detachable needles required multiple rinses to reduce HCV infectivity to undetectable levels whereas a single rinse of insulin syringes was sufficient.ConclusionsOur study, the first to assess the infectivity of HCV in residual volumes of LDS syringes and needles available to PWID, demonstrates that LDS syringe-needle combination still has the greater potential for HCV transmission than insulin syringes with fixed needles. Improved LDS designs may be able to further reduce HCV recovery, but based on the designed tested, LDS needles and syringes remain intermediate between fixed-needle syringes and HDS combinations in reducing exposure to HCV.

Spurious hyperglycaemia impairs automated leucocyte counting. A pilot study with two different haematological analysers.

Pre-analytical errors are a frequent problem that can compromise the quality of the total testing process and, along with analytical mistakes, can have a negative impact on the reliability of test results and patients’ safety1. There is now consolidated evidence that the vast majority of pre-analytical problems emerge from mishandling or scarcely standardised procedures during collection, management and preparation of biological specimens2. In particular, sample contamination by exogenous fluids (e.g., saline) or therapeutics (e.g., antibiotics, thrombolytic agents, glucose or potassium solutions) is a frequent source of problems in diagnostic testing, wherein test values may be variably biased by dilution or direct interference from the specific contaminating substance3. A paradigmatic example is contamination of biological samples with glucose-containing solutions. The administration of intravenous standard glucose solutions, typically 5% (i.e., 278 mmol/L) dextrose in water, is commonplace in clinical practice not only for the treatment of hypoglycaemia, but also for maintaining tissue hydration after acute disease or surgery, and as a means of parenteral nutrition4. Although it has been recommended that blood samples should be drawn from the opposite arm from which glucose solutions and other intravenous fluids are administered5, blood samples are frequently collected from infusion routes, in order to avoid a second venipuncture and save precious time in short stay or critical wards such as emergency departments and intensive care units. Even the best practice of the Clinical and Laboratory Standards Institute for collecting blood from intravenous lines, that is clearance of fluid before the sample is collected by discarding an adequate amount of fluid (i.e., typically 5 mL or 6 times the dead space volume)6, is frequently overlooked. Therefore, blood sample contamination is a relatively common occurrence and may lead to diagnostic errors and adverse consequences for patients’ health, including inappropriate therapeutic correction of spurious abnormalities (e.g., hypoglycaemia or hyperkalaemia), as well as unjustified transfusion of blood components in the case of spurious dilution of blood7,8. It has been previously shown that blood sample contamination by glucose solutions may generate a significant bias in clinical chemistry9 and coagulation testing10. Nevertheless, to the best of our knowledge, no information exists on the effect of spurious hyperglycaemia on leucocyte counts and differential. This is of paramount importance, since biased results may confound diagnostic reasoning and lead to inappropriate therapeutic decisions. The aim of this study was, therefore, to evaluate whether contamination of whole blood samples with standard glucose solutions (as may occur during normal venipuncture contaminated by exogenous glucose) may affect leucocyte counts measured by two widely used haematological analysers (ADVIA 2120 [Siemens Diagnostic Solutions, Milan, Italy] and XE-2100 [Dasit SpA, Cornaredo, Italy]), characterised by different analytical technologies.

A non-invasive method for estimating lung function

Conventional methods for monitoring lung function usually require complex gas analysers and the co-operation of the patient. Therefore, they are not compatible with the crowded environment of the Intensive Care Unit (ICU) or operating theatre, where the patient co-operation is usually impossible. However, it is precisely these patients that would benefit the most from accurate monitoring of lung function. This paper develops a compact and non-invasive system for the measurement and monitoring of lung function in a clinical setting, such as lung volume, airway dead space volume, and pulmonary blood flow. In contrast with conventional methods, the compact apparatus and non-invasive nature of the proposed method allow it to be used in the ICU, as well as in general clinical settings. The system implements a breath-by-breath computer ventilation model using a non-invasive technique, in which a tracer gas is injected into the patient's inspired breath. Experimental results are shown for both an artificial lung and a healthy volunteer. Our findings show that the proposed technique has several advantages over the conventional method for the estimation of lung function.