Diffusion Reaction of Carbon Monoxide in the Human Lung.

The capture of CO, a standard lung function test, results from diffusion-reaction processes of CO with hemoglobin inside red blood cells (RBCs). In its current understanding, suggested by Roughton and Forster in 1957, the capture is represented by two independent resistances in series, one for diffusion from the gas to the RBC periphery, the second for internal diffusion reaction. Numerical studies in 3D model structures described here contradict the independence hypothesis. This results from two different theoretical reasons: (i) The RBC peripheries are not equi-concentrations; (ii) diffusion times in series are not additive.

Partial versus maximal forced exhalations in COPD: enhanced signal detection for novel therapies.

BACKGROUND: Evaluation of novel compounds for COPD often relies on FEV1 for signal detection. Partial forced exhalations from end-tidal inspiration (PEFV) might complement FEV1 in identifying such a signal. We examined the prevalence of bronchodilator response (BDR) using PEFV and FEV1 in patients with COPD. METHODS: 110 consecutive COPD patients were tested prospectively with PEFV and maximal expiratory flow before and after inhalation of a short-acting ß2 agonist (salbutamol, 400 µg). Partial flow at 800 ml above residual volume was derived from the PEFV (PF800). Significant changes in PF800 and/or FEV1 were set at the upper 95% confidence interval after placebo (n = 28). RESULTS: Four groups were identified by the presence (+) or absence (-) of a BDR: Group 1 [PF800 (-)FEV1(-)] when no change was observed (n = 31), Group 2 [PF800(+)FEV1(-)] when PF800 alone improved (n = 31), Group 3 [PF800(-)FEV1(+)] when FEV1 alone improved (n = 26), and Group 4 [PF800(+)FEV1(+)] when both variables improved (n = 18). There were 35 non-responders in any parameter, and 75/110 subjects who showed a response in at least one parameter. The changes in PF800 and FEV1 were not correlated suggesting these assess different airway generations. CONCLUSIONS: The use of PF800 increased detection of a BDR in COPD compared to FEV1 alone and may reflect small airway responses. The PEFV maneuver is simple, repeatable and may avoid some of the theoretical disadvantages of FEV1. The role of PF800 for evaluating novel anti-inflammatory agents remains to be determined.

[Evaluation and follow up of hyperinflation in COPD]. / Comment mesurer et suivre la distension pulmonaire au cours de la BPCO.

Plethysmography is the reference method and requires rigorous methodology, particularly in patients with severe airflow limitation. Dilution techniques (nitrogen or most often helium) may underestimate true lung volumes as they do not measure trapped gas. Inspiratory capacity is the only available method to evaluate exercise induced dynamic hyperinflation. It is an imperfect surrogate of plethysmography for evaluating the reversibility of hyperinflation with bronchodilators. Resting hyperventilation has recently been shown to be a sensitive method to detect dynamic hyperinflation. Evaluation of hyperinflation is an important criterion in the phenotyping of COPD patients. However, its natural history remains at present poorly defined.

[Practical methods for controlled diaphragmatic breathing in 2009: proposals for a consensus]. / Modalités pratiques de réalisation de la ventilation dirigée abdomino-diaphragmatique en 2009: propositions pour un consensus.

BACKGROUND: This work has been completed at the request of the French Language Society of Pneumology. It is the result of collaboration between the 'Muscles and Respiration Group' and the 'Working Group in Physiotherapy', arriving at a consensus on diaphragmatic breathing. RESULTS: From the literature followed by a formalized consensus methodology, the authors specify the terminology and define the appropriate methods of this technique that should be used. CONCLUSION: Analysis of the literature to date does not allow assessment of the efficacy of this technique. The precise definition of the methods of diaphragmatic breathing as proposed in the present study will be used as a basis for forthcoming studies on this technique.

[Swallowing disorders, pneumonia and respiratory tract infectious disease in the elderly]. / Troubles de la déglutition du sujet âgé et pneumopathies en 14 questions/réponses.

Swallowing disorders (or dysphagia) are common in the elderly and their prevalence is often underestimated. They may result in serious complications including dehydration, malnutrition, airway obstruction, aspiration pneumonia (infectious process) or pneumonitis (chemical injury caused by the inhalation of sterile gastric contents). Moreover the repercussions of dysphagia are not only physical but also emotional and social, leading to depression, altered quality of life, and social isolation. While some changes in swallowing may be a natural result of aging, dysphagia in the elderly is mainly due to central nervous system diseases such as stroke, parkinsonism, dementia, medications, local oral and oesophageal factors. To be effective, management requires a multidisciplinary team approach and a careful assessment of the patient's oropharyngeal anatomy and physiology, medical and nutritional status, cognition, language and behaviour. Clinical evaluation can be completed by a videofluoroscopic study which enables observation of bolus movement and movements of the oral cavity, pharynx and larynx throughout the swallow. The treatment depends on the underlying cause, extent of dysphagia and prognosis. Various categories of treatment are available, including compensatory strategies (postural changes and dietary modification), direct or indirect therapy techniques (swallow manoeuvres, medication and surgical procedures).

European reference equations for CO and NO lung transfer.

The aim of the present study was to calculate reference equations for carbon monoxide and nitric oxide transfer, measured in two distinct populations. The transfer factor of the lung for nitric oxide (T(L,NO)) and carbon monoxide (T(L,CO)) were measured in 303 people aged 18-94 yrs. Measurements were similarly made in two distant cities, using the single-breath technique. Capillary lung volume (V(c)) and membrane conductance, the diffusing capacity of the membrane (D(m)), for carbon monoxide (D(m,CO)) were derived. The transfer of both gases appeared to depend upon age, height, sex and localisation. The rate of decrease in both transfers increased after the age of 59 yrs. T(L,NO)/alveolar volume (V(A)) and T(L,CO)/V(A) were only age-dependent. The mean T(L,NO)/T(L,CO) was 4.75 and the mean D(m)/V(c) was 6.17 min(-1) x kPa(-1); these parameters were independent of any covariate. V(c) and D(m,CO) calculations depend upon the choice of coefficients included in the Roughton-Forster equation. Values of 1.97 for D(m,NO)/D(m,CO) ratio and 12.86 min x kPa(-1) for 1/red cell CO conductance are recommended. The scatter of transfer reference values in the literature, including the current study, is wide. The present results suggest that differences might be due to the populations themselves and not the methods alone.

[Atopic dermatitis aggravates the allergic airways inflammation in acute viral bronchiolitis]. / La dermatite atopique aggrave l'inflammation allergique dans la bronchiolite aiguë virale.

INTRODUCTION: Exhaled nitric oxide (FeNO) is a putative non-invasive marker of eosinophilic airway inflammation with a good predictive value for allergic asthma in preschool children. The aim of the present study was to compare FeNO after acute viral bronchiolitis (AVB) in children aged less than 2 years without atopic dermatitis (AD) vs those with atopic dermatitis, as well as children with AD without any history of AVB. METHODS: Forty-two children (mean age +/- SD: 12.3 +/- 5.2 months; range 5.0-23.5; sex-ratio M: F=1.3: 1) were included in this prospective study, > 8 wks after an episode of AVB. The patients' atopic status was assessed both by clinical phenotype and IgE- mediated response to inhaled and/or food allergens. FeNO (ppb) was measured off-line by the chemoluminescence method on samples obtained from gas collected in a balloon during tidal breathing. RESULTS: There was a significant difference between the AVB/AD (23.4 +/- 14.3 ppb, n=15) vs the AVB without AD group (13.5 +/- 10. 1 ppb, n=13) or the AD without AVB group (11.0 +/- 8.3 ppb, n=14). Maternal feeding for more than 2 months decreased FeNO by 50%. CONCLUSION: Atopic children below 2 years with AD produce more NO after AVB than non-atopic children or atopic children without any history of AVB. Maternal feeding decreases FeNO.

[Lung cancer in the elderly subject]. / Cancer bronchique du sujet âgé.

INTRODUCTION: In France, the average age for the diagnosis of bronchial carcinoma is 64. It is 76 in the population of over 70. In fact, its incidence increases with age linked intrinsic risk of developing a cancer and with general ageing of the population. Diagnosis tools are the same for elderlies than for younger patients, and positive diagnosis mainly depends on fibreoptic bronchoscopy, complications of which being comparable to those observed in younger patients. STATE OF THE ART: The assessment of dissemination has been modified in recent years by the availability of PET scanning which is increasingly becoming the examination of choice for preventing unnecessary surgical intervention, a fortiori in elderly subjects. Cerebral imaging by tomodensitometry and nuclear magnetic resonance should systematically be obtained before proposing chirurgical treatment. An assessment of the general state of health of the elderly subject is an essential step before the therapeutic decision is made. This depends on the concept of geriatric evaluation: Geriatric Multidimensional Assessment, and the Comprehensive Geriatric Assessment which concerns overall competence of the elderly. PERSPECTIVES: This is a global approach that allows precise definition and ranking of the patient's problems and their impact on daily life and social environment. Certain geriatric variables (IADL, BADL, MMSE, IMC etc) may be predictive of survival rates after chemotherapy or the incidence of complications following thoracic surgery. The main therapeutic principles for the management of bronchial carcinoma are applicable to the elderly subject; long term survival without relapse after surgical resection is independent of age. Whether the oncological strategy is curative or palliative, the elderly patient with bronchial carcinoma should receive supportive treatments. They should be integrated into a palliative programme if such is the case. In fact, age alone is not a factor that should detract from optimal oncological management. CONCLUSIONS: The development of an individual management programme for an elderly patient suffering from bronchial carcinoma should be based on the combination of oncological investigation and comprehensive geriatric assessment.

The Roughton-Forster equation for DLCO and DLNO re-examined.

Roughton and Forster (RF) proposed to split the lung diffusing capacity into two contributions describing first, diffusion to red blood cells (RBC), and second, capture by diffusion from the RBC surface and reaction with haemoglobin. Solving the diffusion-reaction equations for simplified capillary-RBC structures, we investigate the RF interpretation. This reveals first that the conventional extrapolation to zero pressure of 1/DLCO on PO2 is not a correct measure of the diffusive component. Consequently the capillary volumes deduced from this extrapolation are erroneous. Secondly, capture mechanisms are different for CO and NO: while DLCO characterizes "volume absorption" in the RBC and is correlated with hematocrit, DLNO quantifies "surface absorption" and provide information about the morphology of the space between the alveolar surface and the RBC surfaces. In conclusion, the RF approach may lead to erroneous physiological interpretations of DLCO; nevertheless, the measurement of DLCO and DLNO bring different types of information that give the potential for a better understanding of respiratory diseases.

[Factors influencing pulmonary function in Tunisian women aged 45 years and more]. / Facteurs influençant les variables ventilatoires des Tunisiennes âgées de 45 ans et plus.

INTRODUCTION: The aim of this study was to analyse the factors influencing pulmonary function and inspiratory muscle strength in healthy Tunisian women aged >or=45 years and in particular to determine the effect of parity. METHODS: A medical questionnaire together with an evaluation of sporting activity score and 2 levels for schooling and socio-economic status was administered. Parity was introduced as numeric, as dichotomous (G1:or=4) and in 3 classes (C1:<2; C2:=3-4; C3: > 4). Plethysmography with measurement of airway conductance and maximal inspiratory pressure was performed. RESULTS: 108 women were included. According to the ascending multiple linear regression, and in decreasing order, the following influencing factors are noted: Age and height, parity, weight and daily activity, schooling level, and finally leisure activity, body mass index, and physical activity. With high parity, and especially in women aged >or=60 years, there was a decrease in inspiratory muscle strength and an obstructive tendency, without associated restrictive component. Parity effects are age independent. CONCLUSIONS: Factors influencing the pulmonary function of healthy Tunisian women aged >or=45 years are multiple. Lung function declines with increasing parity.

[Aging of the lung parenchyma]. / Vieillissement du poumon profond.

INTRODUCTION: The study of lung parenchymal function is focused on the measurement of carbon monoxide diffusing transfer (TLCO) which is a function of both membrane characteristics (Dm) and capillary lung volume (Vc) The objective of this study was to estimate the effect of age on both variables. METHODS: At rest, 134 healthy non-smokers (18-85 year old) were investigated by a double transfer NO-CO method. Capillary pulmonary compliance was estimated by applying a continuous negative pressure (CNP: -10 mmHg) at the mouth to 24 subjects. RESULTS: Significant decreases in VA, TLCO, TLNO, Dm and Vc in relation to age were observed (p < 0.05). CNP induced a significant increase in all variables, the increase in Vc in elderly was greater than that in younger subjects. CONCLUSION: Alveolo capillary membrane aging induces a decrease in Dm and Vc, however the increase in the estimated capillary compliance with CNP could provide an adaptation to the decrease in Vc.

[Physiological factors influencing pulmonary capillary volume and membrane diffusion]. / Facteurs physiologiques influençant le volume capillaire pulmonaire et la diffusion membranaire.

BACKGROUND: The lung is subject to many physiological changes during life. The aim of this study was to identify factors that influence gas transfer, which depends on membrane diffusion (Dm) and pulmonary capillary blood volume (Vc). METHODS: Dm and Vc measurements were performed at rest in 135 healthy patients divided into three groups according to age and after an exercise in 22 non-trained children. Measurements were made using a simultaneous transfer of 2 gases; nitric oxide (NO) and carbon monoxide (CO). RESULTS: Dm was correlated with height in the adult group and with weight in the elderly group. Vc was not correlated with weight in the three studied groups, but correlated with height in the adult group. Dm and Vc declined with age (p<0.05), For Dm this started at the age of forty whereas a fall in Vc was apparent at sixty. Pulmonary and vascular ageing could explain these results. Sex had no effect on Dm and Vc. Exercise led to a significant rise in Dm and Vc (p<0.05) which was attributed to pulmonary capillary distension and recruitment. CONCLUSION: Knowledge of these physiological changes permits a better understanding of pathological changes.

[Evaluation of pulmonary function in the elderly. Intergroupe Pneumo Gériatrie SPLF-SFGG]. / Evaluation de la fonction respiratoire chez le sujet âgé. Intergroupe Pneumo Gériatrie SPLF-SFGG.

Aging is associated with a progressive decrease in lung function. As a consequence of aging, individual's reserve is diminished, but this decrease is heterogeneous between individual subjects. Many factors are involved in the overall decline in lung function. The prevalence of asthma in the elderly is estimated between 6 and 10%. Mortality due to COPD is increasing, especially among older subjects. Older subjects are at an increased risk of developing chronic diseases such as Parkinson's disease, which can have consequences for lung function. Under-nutrition is also common in the elderly and can produce sarcopenia and skeletal muscle dysfunction. The presentation of respiratory disorders may differ in the elderly, especially because of a lack of perception of symptoms such as dyspnea. The impact of bronchodilatators or corticosteroids on respiratory function has not been studied in the elderly. Drugs usually used for the treatment of hypertension or arrhythmias, which are often observed with aging, can have pulmonary toxicity. There is no difference between functional evaluation in younger and older subjects but it is more difficult to find predicted values for older patients. Performing pulmonary function tests in older patients is often difficult because of a higher prevalence of cognitive impairment and/or poor coordination. When assessing pulmonary function in the elderly, the choice of tests will be depend on the circumstances, with the use of voluntary manoeuvres dependent on the condition of the patient.

Gas exchange alterations in patients with chronic obstructive lung disease.

In a series of 23 patients with COPD, Wagner et al showed three distinct patterns of VA/Q distributions and a correlation between Burrows' clinical classification and the observed distribution patterns. Using the inert gas method, we studied 51 patients suffering from severe but stable COPD (FEV1 = 0.84 +/- 0.38 L; PaO2 = 58.5 +/- 10.5 mm Hg; PaCo2 = 48 +/- 6 mmHg; Ppa = 22 +/- 8 mmHg) breathing room air in a steady state. The H pattern (high mode of VA in high VA/Q) was found in 24 cases. There was an L pattern (Q mode in low VA/Q units) in nine cases and an HL (high-low) pattern in 16 cases (two patients were assigned another group). The analysis of the distribution data confirmed that VA/Q heterogeneity was the main factor underlying gas exchange disturbances in COPD. The PaO2 of the H subjects was higher than that of both HL (p less than 0.02) and L subjects. The true shunt value in the L group was significantly lower than in the H and HL groups. However, the relationship between clinical or functional aspects and distribution was not direct. The fraction of patients of H, HL, or (H + HL) types was nearly identical in the three clinical groups. The H pattern was found to be predominant in cases of COPD.

Effect of dry warm air on respiratory water loss in children with exercise-induced asthma.

The variation in respiratory water loss (RWL) over time, expressed as the mass of water vapor lost per liter (body temperature and pressure, saturated) of ventilation (MH2O), was investigated in two groups: (1) children with exercise-induced asthma; and (2) healthy children. Children were matched for age and sex and went without medication for at least 12 hours before each experiment. The children breathed dry warm air (TI = 28.4 degrees C +/- 0.3 degree C) for 15 minutes while bicycling at constant and moderate work load (50 W). The MH2O was measured by collecting and weighing the expired water vapor (1) at rest breathing in warm conditions of inspired gas (control values), (2) every five minutes during exercise while breathing dry warm air, and (3) four minutes after the end of exercise. Pulmonary function tests were performed before and six minutes after exercise. The results were abnormal only in children with exercise-induced asthma. During exercise, RWL significantly fell (compared to control value) at the tenth and 15th minute in both groups. Whereas normal subjects recovered their initial values for MH2O four minutes after stopping exercise, asthmatic children still had a reduction in respiratory water loss. During exercise, MH2O decreased a little more in healthy than in asthmatic children. The decrease in MH2O in both groups suggests that the means to fully humidify expired gas are overwhelmed by thermal stress. The lack of increase in MH2O in asthmatic children on stopping exercise suggests that the airway mucosa is unable to produce enough water vapor and is thus dehydrated and probably hyperosmotic.

Lung density and lung mass in emphysema.

Mean lung density (dm) and radiologic (VLx) lung volume can be calculated using CT scan data. As many emphysematous patients are overdistended, the analysis of dm alone could be meaningless. However, lung mass (m) can be calculated as the product of dm and VLx. Twenty-four patients suspected of mild or severe emphysema as judged by roentgenographic and physiologic examinations as well as 16 healthy subjects were included in the protocol. They all underwent both a CT scan of the whole lung and functional tests from which the following were derived: airway resistance, forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), total lung capacity (TLC), CO transfer capacity, quasi-static compliance at functional residual capacity (FRC), and blood gases. All CT scans were performed at the FRC of each patient. The dm was lower in emphysema patients than in healthy subjects, as m was greater in patients than in healthy subjects; 1,303 +/- 398 g and 997 +/- 133 g, respectively. Although dm values were significantly correlated to FEV1, FEV1/FVC, and TLC, m values were not correlated to any of these functional indices. Unexpectedly, these results show that most patients (22/24) with emphysema have a normal or increased lung mass. Normal or above normal m values might be due to oversecretion in some patients. Nevertheless, the synthesis of new tissue due to chronic inflammation is the most likely explanation that could account for this finding.

Distribution of lung density and mass in patients with emphysema as assessed by quantitative analysis of CT.

STUDY OBJECTIVE: To assess the effects of emphysema on the apex-to-base gradient of lung density (D) and lung mass (M) and to explore the relationship between M and lung function. METHODS: CT scans of whole lungs were performed in 12 healthy subjects and 29 patients who were breathing at functional residual capacity, after which lung function tests were performed. Whole D and M and regional D (RLD) and M (RLM) were calculated. The degree of emphysema was scored. RESULTS: The RLM for each height did not differ significantly between patients with disease and healthy subjects, while RLD was significantly lower in the patients with disease. A less marked nonlinear, increasing, craniocaudal gradient of D was observed in the group with disease, suggesting that the distension increases progressively from the apex to the base. RLD and RLM in the 40 to 90% lung height differed significantly among patients in the emphysema group with normal, high, and low M compared to the healthy subjects. M did not differ significantly between patients with centrilobular and panlobular emphysema, which was thought to stem from the marked variations in the results. Vital capacity was lower in the patients with low M. CONCLUSIONS: The lower RLD in the group with low M was due to both lung overinflation and to tissue loss, while in the groups with high or normal M, it was due only to lung overinflation.

In vitro accuracy of three blood O2 saturation optic catheter systems.

OBJECTIVE: The measure of the precision and accuracy of three optic SvO2 systems in vitro (SAT-2 Baxter, oximetrix 3 Abbott, HEMOPRO-2 Spectramed in a wide range of saturations (24-85%) and hematocrit (20-40%). DESIGN: In vitro comparison of the results given by a Co-Oximeter and the SvO2 systems. MEASUREMENTS AND RESULTS: 144 blood samples were tonometered with a variety of gas mixtures. Measurements of SvO2 were compared to those obtained by means of a Co-Oximeter, the difference (dSO2) between paired values were calculated. Precision was evaluated from confidence intervals (2SD) and accuracy was tested using dSO2 figures. As there was no difference in either precision or accuracy among catheters for a given system, data obtained from a given system were pooled. Mean precision was 14.2%, 8.6%, 9% for the Spectramed, Baxter and Abbott systems, respectively. CONCLUSION: The rather low reliability of the optic method should be borne in mind in patients with low SvO2 and/or low hematocrit.

High frequency jet ventilation and upper tracheal stenosis: a model study.

A chest-lung model, consisting of a human laryngo-tracheo-bronchial tree cast (4 or 5 bronchial generations) tightly enclosed in a 100 l rigid box was used to assess the potential efficiency of high frequency jet ventilation in patients with upper tracheal stenosis. The elasticity of the air in the box stimulated normal adult chest-lung compliance. Diaphragms (0.5 or 1.5 cm thick) were inserted into the upper trachea to simulate stenoses of 0.7, 1, 1.5 and 1.75 cm inner diameter. A rigid injector-catheter (5 mm outside diameter) was directed in the axis of the trachea with its tip 2.5 cm beneath the stenosis. The end inspiratory alveolar pressure (PA), the end expiratory pressure (PEEP) and the tidal volume (VT) were measured at a rate of 100/min and 30% inspiratory to total periods ratio. Entrained flow, Vem, measured at the start of air insufflation, was compared to that calculated (Vec) from a simple model. For a given setting of the ventilator, PEEP, PA--PEEP and VT were approximately linearly related to the difference in diameters of stenosis and injector. While PEEP decreased, both PA--PEEP and VT increased with increasing diameter of stenosis. When the diameter of the stenosis was higher than 1.5 cm no changes in PA--PEEP and VT were observed, owing to the narrowest section of the larynx. Vec was always higher than Vem. The thickness of the stenosis did not affect the results, and the diameter of the stenosis appeared to be the main factor affecting the ventilatory parameters under our experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)