Mucoviscidose : du bon usage des explorations fonctionnelles respiratoires

INTRODUCTION

Neonatal screening for cystic fibrosis (CF) leads to early dedicated specialist care for all patients.

BACKGROUND

Pulmonary function tests (PFT) are mandatory for routine monitoring of CF patients. The aim of this article is to review the current guidelines for PFTs in CF, particularly the type of test, the age and the clinical status of the patient.

VIEWPOINT

The regular use of spirometry is generally accepted. Many other tests are used but their clinical value in the routine follow-up of CF patients remains to be established.

CONCLUSION

Further efforts should be made to evaluate the value of PFTs in CF, particularly in very young children.

Performance and Muscle Oxygenation during Isometric Exercise and Recovery in Children with Congenital Heart Diseases

This study investigated performance, muscle oxygen saturation (StO2), and blood volume (BV) in patients with congenital heart diseases (CHD) and healthy children during and following sustained exercise. Maximal volunteered contraction (MVC) and endurance at 50 % of MVC (time to exhaustion, Tlim) of the knee extensor were measured in nine patients with CHD and 14 healthy control children. Near infrared spectroscopy was used to evaluated StO2 and BV in vastus lateralis. The drop in muscle oxygen saturation (D(mO2)), half time of recovery (T(SR)), and recovery speed to maximal oxygen saturation (Rs) were analyzed. Patients with CHD showed lower MVC (101.0 +/- 6.2 vs. 125.5 +/- 7.4 N x m, p < 0.01) and Tlim (67.0 +/- 7.5 vs. 127.5 +/- 11.1 s, p < 0.001) than control children. StO2 and BV values in both groups were similar at rest and decreased at the onset of contraction. D(mO2) was larger in patients, which reflected pronounced deoxygenation. During recovery, the patients exhibited a longer TSR (25.2 +/- 2.1 vs. 18.4 +/- 2.0 s, p < 0.05) and R(S) (64.6 +/- 5.5 vs. 42.7 +/- 4.6 s, p < 0.01) than control children. We concluded that reduced strength and endurance in patients with CHD were associated with an impairment of StO2 and BV, and a slower reoxygenation during recovery.

Acid dye adsorption onto cationized polyamide fibres. Modeling and consequent interpretations of model parameter behaviours

Experimental adsorption isotherms of four acid dyes named Acid Blue 25, Acid Yellow 99, Reactive Yellow 23, and Acid Blue 74 from aqueous solution onto cationized nylon-6,6 have been analyzed using a double layer adsorption model. The parameters involved in the analytical expression of this model such as the number or fraction of adsorbed dye molecule per site, n, the number of receptor sites per gram of adsorbent, N(M), and the concentration at half-saturation, c1/2, are determined from adsorption isotherms at four temperatures between 293 and 353 K. The evolution of these parameters with temperature is discussed in relation with adsorption process and the behaviours of the different dyes taking into account their particular structure. The results are compared with those already published dealing with the adsorption of these same dyes onto cationized cotton. The configurational entropy at various temperatures has been studied. This parameter allowed to deduce some results related to the evolution of the disorder during the adsorption process.

Six-Minute Walking Test to Assess Exercise Tolerance and Cardiorespiratory Responses During Training Program in Children With Congenital Heart Disease

This study assessed the exercise tolerance and the cardiorespiratory responses to a training program by the six-minute walk test (6'WT) in children with congenital heart disease (CHD). Seventeen cardiac and 14 healthy children performed maximal cardiopulmonary exercise test (CPET) and 6'WT. Reliability of 6'WT was assessed in all subjects (test-retest) by Bland-Altman plots. Cardiac subjects were randomly divided in training (T-CHD) and control groups (C-CHD). T-CHD underwent an individualized training exercise at the ventilatory threshold (VT) intensity during 12 weeks. We found that the 6'WT is a reliable and reproducible test. CHD children walked a lower distance than healthy children before training (472.5 +/- 18.1 vs. 548.8 +/- 7.7 m, respectively, p < 0.001). Likewise, power output, oxygen uptake (V.O (2)), and heart rate (HR) at the maximum and the VT levels, were significantly lower in patients (p < 0.001). After training, a significant improvement of walking distance (WD) was shown in T-CHD (529.6 +/- 15.3 vs. 467.7 +/- 17.1 m, p < 0.001). The power output, VO2, HR, and V.E increased slightly (6 to 10 %, p > 0.05) at peak exercise and significantly at ventilatory threshold level (p < 0.05) in T-CHD. Significant relationships between WD and VO2max as well as VO2 at VT were founded (p < 0.05). We concluded that the 6'WT is a useful and reliable tool in the assessment and follow-up of functional capacity during rehabilitation program in children with CHD.

Timing and driving components of the breathing strategy in children with cystic fibrosis during exercise

The aim of this study was twofold: first, to determine the breathing strategies of children with cystic fibrosis (CF) during exercise, and secondly, to see if there was a correlation with lung function parameters. We determined the tension-time index of the inspiratory muscles (T(T0.1)) during exercise in nine children with CF, who were compared with nine healthy children with a similar age distribution. T(T0.1) was determined as followed T(T0.1) = P0.1/PImax . T(I)/T(TOT), where P0.1 is mouth occlusion pressure, PImax is maximal inspiratory pressure, and T(I)/T(TOT) is the duty cycle. CF children showed a significant decrease of their forced expiratory volume in 1 sec (FEV1), forced vital capacity (FCV), and FEV1/FVC, whereas the residual volume to total lung capacity ratio (RV/TLC) ratio and functional residual capacity (FRC) were significantly increased (P < 0.001). Children with CF showed mild malnutrition assessed by actual weight expressed by percentage of ideal weight for height, age, and gender (weight/height ratio; 82.3 +/- 3.6%). Children with CF showed a significant reduction in their PImax (69.3 +/- 4.2 vs. 93.8 +/- 7 cmH2O). We found a negative linear correlation between PImax and weight/height only in children with CF (r = 0.9, P < 0.001). During exercise, P(0.1), P0.1/PImax, and T(T0.1) were significantly higher, for a same percent maximal oxygen uptake in children with CF. On the contrary, T(I)/T(TOT) ratio was significantly lower in children with CF compared with healthy children. At maximal exercise, children with CF showed a T(T0.1) = 0.16 vs. 0.14 in healthy children (P < 0.001). We observed at maximal exercise that P0.1/PImax increased as FEV1/FVC decreased (r = -0.90, P < 0.001), and increased as RV/TLC increased (r = 0.92, P < 0.001) only in children with CF. Inversely, T(I)/T(TOT) decreased as FEV1/FVC decreased (r = 0.89, P < 0.001), and T(I)/T(TOT) decreased as RV/TLC increased (r = -0.94, P < 0.001). These results suggest that children with CF adopted a breathing strategy during exercise in limiting the increase of the duty cycle. Two determinants of this strategy were degrees of airway obstruction and hyperinflation.

Clinical characteristics at initial presentation and impact of dual therapy on the outcome of bacteremic Streptococcus pneumoniae pneumonia in adults

BACKGROUND

Approximately 10% of patients hospitalized with community-acquired pneumonia (CAP) are bacteremic. Bacteremic Streptococcus pneumoniae pneumonia (BSPP) is the number one cause of mortality, representing up to 70% of all CAP deaths. In fact, all CAP guidelines have identified this issue as one of the most important issues when establishing their recommendations.

OBJECTIVE

To assess the impact of dual antibiotic therapy in patients with BSPP.

PATIENTS AND METHODS

All cases of BSPP in patients 18 years of age and older who were hospitalized from 1995 to 2000 were retrospectively analyzed. The standard initial therapeutic regimen used was cefuroxime with or without a macrolide from 1995 to 1997, and ceftriaxone and azithromycin or clarithromycin from 1998 to 2000. During the 1995 to 1997 period, only 16% of the patients initially received a macrolide, whereas all patients in the 1998 to 2000 period received a macrolide at admission.

RESULTS

Ninety-five patients (49 men, 46 women) with a mean age of 63 years (range 20 to 98 years) were included in the present study. The mean pneumonia severity index at admission was 113 for the monotherapy cohort and 114 for the dual therapy group. At admission, 30.5% of patients had a leukocyte count greater than 20 109/L, 11.5% had a systolic blood pressure less than 90 mmHg, 44.2% had a respiratory rate greater than 30 breaths/min and 33.6% had nausea/vomiting, necessitating some form of therapy or preventing the patient from eating. In addition, 16.8% had no fever at admission. Overall, 72.5% became afebrile within 48 h. Fifteen (15.8%) patients died (four within the first 72 h). The mortality rate was significantly higher in the monotherapy group (11 of 42 patients; 25.6%) than in the dual therapy cohort (four of 53 patients; 7.5%) (OR 0.23; 95% CI 0.07 to 0.74). Antibiotic resistance was not associated with increased mortality.

CONCLUSION

The combination of ceftriaxone plus a macrolide significantly reduced the mortality rate compared with monotherapy (cefuroxime) in patients with CAP that have the highest mortality rate.

Distribution and habitat niches of 37 peatland Cyperaceae species across a broad geographic range in Canada

The presence and absence of 37 Cyperaceae species found on 498 peatlands across Canada were examined along surface water chemistry, shade, height above the water table, and climatic gradients. A canonical correspondence analysis of the species distribution along the environmental gradients indicated that surface water chemistry and climate were highly correlated with the first and second axes and were the two most important gradients distinguishing among groups. The climatic gradient was further subdivided into western oceanic continental and eastern oceanic continental gradients. Height above the water table and shade were correlated to the third canonical correspondence analysis axis and were of secondary importance in explaining species distributions. A TWINSPAN analysis of the species separated them into eight groups: (1) widespread, obligate rich fen, wet, shade-tolerant species; (2) widespread rich fen preferential species; (3) continental and eastern oceanic, rich fen preferential, wet, shade-intolerant species; (4) widespread fen, wet, shade-intolerant species; (5) widespread bog or fen, shade-tolerant species; (6) widespread subcontinental and oceanic, bog or fen, shade-intolerant species; (7) eastern subcontinental and oceanic, poor fen preferential species; (8) western oceanic, bog and poor fen preferential, shade-intolerant species. Response surfaces were generated by quantifying the frequency of occurrence of representative species in each group along pH and height above the water table, shade and mean annual temperature, and mean annual total precipitation gradients. Frequency of occurrence values for several of the rarer species indicated that they were not limited by the number of suitable habitats analyzed in this study but by other factors such as competition, failure to establish, or dispersal. This study emphasizes the importance of habitat and climate in determining the local and regional diversity and distribution of the most common Cyperaceae on peatlands in Canada.Key words: sedges, Carex, peat lands, response surfaces, climate, water chemistry.

Differential sensitivity to apoptosis between the human small and large intestinal mucosae: linkage with segment-specific regulation of BCL-2 homologs and involvement of signaling pathways

The small and large intestines differ in their expression profiles of Bcl-2 homologs. Intestinal segment-specific Bcl-2 homolog expression profiles are acquired as early as by mid-gestation (18-20 weeks) in man. In the present study, we examined the question whether such distinctions underlie segment-specific control mechanisms of intestinal cell survival. Using mid-gestation human jejunum and colon organotypic cultures, we analyzed the impact of growth factors (namely insulin; 10 microg/ml) and pharmacological compounds that inhibit signal transduction molecules/pathways (namely tyrosine kinases, Fak, P13-K/Akt, and MEK/Erk) on cell survival and Bcl-2 homolog expression (anti-apoptotic: Bcl-2, Bcl-X(L), Mcl-1; pro-apoptotic: Bax, Bak, Bad). The relative activation levels of p125Fak, p42Erk-2, and p57Akt were analyzed as well. Herein, we report that (1) the inhibition of signal transduction molecules/pathways revealed striking differences in their impact on cell survival in the jejunum and colon (e.g., the inhibition of p125Fak induced apoptosis with a significantly greater extent in the jejunum [approximately 43%] than in the colon [approximately 24%]); (2) sharp distinctions between the two segments were noted in the modulatory effects of the various treatments on Bcl-2 homolog steady-state levels (e.g., inhibition of tyrosine kinase activities in the jejunum down-regulated all anti-apoptotics analyzed while increasing Bax, whereas the same treatment in the colon down-regulated Bcl-X(L) only and increased all pro-apoptotics); and (3) in addition to their differential impact on cell survival and Bcl-2 homolog expression, the MEK/Erk and P13-K/Akt pathways were found to be distinctively regulated in the jejunum and colon mucosae (e.g., insulin in the jejunum increased p42Erk-2 activation without affecting that of p57Akt, whereas the same treatment in the colon decreased p42Erk-2 activation while increasing that of p57Akt). Altogether, these data show that intestinal cell survival is characterized by segment-specific susceptibilities to apoptosis, which are in turn linked with segmental distinctions in the involvement of signaling pathways and the regulation of Bcl-2 homolog steady-state levels. Therefore, these indicate that cell survival is subject to segment-specific control mechanisms along the proximal-distal axis of the intestine.

A nosocomial outbreak of fluoroquinolone-resistant Streptococcus pneumoniae

Over the course of a 20-month period, in a hospital respiratory ward in which ciprofloxacin was often used as empirical antimicrobial therapy for lower respiratory tract infections (LRTIs), 16 patients with chronic bronchitis developed nosocomial LRTIs caused by penicillin- and ciprofloxacin-resistant Streptococcus pneumoniae (serotype 23 F). The minimum inhibitory concentration (MIC) of ciprofloxacin for all isolates from the first 9 patients was 4 microg/mL, in association with a parC mutation. Isolates from the subsequent 7 patients all had a ciprofloxacin MIC of 16 microg/mL, in association with an additional mutation in gyrA. The MICs for this isolate were 8 microg/mL of levofloxacin (resistant), 2 microg/mL of moxifloxacin and gatifloxacin (intermediately resistant), and 0.12 microg/mL of gemifloxacin. This outbreak demonstrates the ability of S. pneumoniae to acquire multiple mutations that result in increasing levels of resistance to the fluoroquinolones and to be transmitted from person to person.

Human intestinal epithelial cell survival: differentiation state-specific control mechanisms

To investigate whether human intestinal epithelial cell survival involves distinct control mechanisms depending on the state of differentiation, we analyzed the in vitro effects of insulin, pharmacological inhibitors of Fak, MEK/Erk, and PI3-K/Akt, and integrin (β1, β4)-blocking antibodies on the survival of the well-established human Caco-2 enterocyte-like and HIEC-6 cryptlike cell models. In addition, relative expression levels of six Bcl-2 homologs (Bcl-2, Bcl-XL, Mcl-1, Bax, Bak, and Bad) and activation levels of Fak, Erk-2, and Akt were analyzed. Herein, we report that 1) the enterocytic differentiation process results in the establishment of distinct profiles of Bcl-2 homolog expression levels, as well as p125Fak, p42Erk-2, and p57Aktactivated levels; 2) the inhibition of Fak, of the MEK/Erk pathway, or of PI3-K, have distinct impacts on enterocytic cell survival in undifferentiated (subconfluent Caco-2, confluent HIEC-6) and differentiated (30 days postconfluent Caco-2) cells; 3) exposure to insulin and the inhibition of Fak, MEK, and PI3-K resulted in differentiation state-distinct modulations in the expression of each Bcl-2 homolog analyzed; and 4) Fak, β1 and β4 integrins, as well as the MEK/Erk and PI3-K/Akt pathways, are distinctively involved in cell survival depending on the state of cell differentiation. Taken together, these data indicate that human intestinal epithelial cell survival is regulated according to differentiation state-specific control mechanisms.

Dystocia among women with symptomatic uterine rupture

OBJECTIVE

The purpose of this study was to analyze cervical dilatation patterns among women with uterine rupture by means of a mathematic model and to use the results to determine optimal intervention criteria.

STUDY DESIGN

This was a case-control review that compared a case patient group of 19 women with uterine rupture during labor with control groups with either no previous cesarean deliveries, vaginal birth after cesarean delivery, or failure of attempted vaginal birth after cesarean delivery. The mathematic model quantified dilatation and adjusted for conditions specific to each patient. Case patients were compared with matched control subjects by means of paired t tests, analysis of variance, odds ratios, and conditional logistic regression.

RESULTS

Dystocia was present in 31.6% to 47.4% of patients with uterine rupture, versus 2.6% to 13.2% of the control group with no previous cesarean deliveries (P< or =.001). The incidence of an arrest disorder among patients with uterine rupture was similar to that seen in the control group with failure of attempted vaginal birth after cesarean delivery. However, the interval from diagnosis to rupture or cesarean delivery was 5.5 +/- 3.3 hours among case patients with uterine rupture and 1.5 +/- 1.3 hours in the control group with failure of attempted vaginal birth after cesarean delivery.

CONCLUSION

When cervical dilatation was lower than the 10th percentile and was arrested for > or =2 hours, cesarean delivery would have prevented 42.1% of the cases of uterine rupture and resulted in excess 2.6% and 7.9% cesarean delivery rates among women with no previous cesarean deliveries and women with vaginal birth after cesarean delivery, respectively.

Analysis of the behaviour of erythrocytes in an optical trapping system

We present a theoretical analysis of the behaviour of erythrocytes in an optical trapping system. We modeled erythrocyte behaviour in an optical trap by an algorithm which divided the cell surface into a large number of elements and recursively summed the force and torque on each element. We present a relationship between the torque and angle of orientation of the cell, showing that stable equilibrium orientations are at angles of 0 o , 180 o and 360 o and unstable equilibrium orientations are at 90 o and 270 o relative to the axis of beam propagation. This is consistent with our experimental observations and with results described in the literature. We also model behaviour of the erythrocyte during micromanipulation by calculating the net force on it. Such theoretical analysis is practical as it allows for the optimization of the optical parameters of a trapping system prior to performing a specific optical micromanipulation application, such as cell sorting or construction of a cell pattern for lab-on-a-chip applications.

[Several aspects of respiratory function testing in children]

Some practical aspects of respiratory function testing (RFT) are reviewed with special interest on applications in preschool children. RFT may be used for diagnostic, management and follow up purposes. Children may benefit from RFT in a variety of pathological situations. Asthma and other obstructive airways diseases certainly represent the most frequent conditions. Vital Capacity and Forced Expiratory Volume in one second (FEV1) may usually be obtained from age 7 on. In smaller children, the forced expiratory manoeuvre is much less successful. Non invasive measurements such as respiratory resistance (Rrs) or specific airway resistance (sRaw) may be used. Rrs is usually measured by the interrupter technique or the forced oscillation technique and sRaw by body plethysmography, not requiring the estimation of thoracic gas volume. Because much variability is introduced by the upper airways, these parameters are less suited than FEV1 to establish the degree of baseline airway obstruction. On the other hand, Rrs and sRaw may quantify reversibility of airway obstruction and/or bronchial hyperresponsiveness. Lung hyperinflation may be identified by the assessment of Functional Residual Capacity (FRC) with a dilution method. More generally lung growth may be followed up in longitudinal studies of FRC even in small children. More work is needed to standardize RFT techniques and indications in the preschool child.

[Randomized trial of two health care deliveries during premature labor]

The main target of this clinical trial was to determine if, for a diagnosis of premature labour, a home prenatal follow-up compared to a classical hospitalization influenced the outcome of pregnancy in terms of gestation age and weight at birth. The participants were recruited in the population of pregnant women in hospital for a threat of premature delivery. The data collection was carried out with the help of four instruments, i.e. the perinatal and personal information Guide, the Scale of antenatal stress, the Inventory of support behaviour and the Scale of the dyadic relations. The analyses carried out do not reveal any statistically significant differences between the two groups for the main variables. But staying at home presents a safe and human alternative to traditional hospitalization and offers some advantages for the pregnant women, specially those faced with socio-economic difficulties.

A sealless centrifugal blood pump with passive magnetic and hydrodynamic bearings

We are developing a permanently implantable ventricular assist system based on a sealless centrifugal blood pump. The impeller of the pump is supported by a passive radial magnetic bearing acting in synergy with hydrodynamic bearings. Torque is transmitted to the impeller by electromagnetic coupling via an integrated axial flux gap motor. Computer modeling has been used extensively to guide the hydraulic and electromagnetic design of the pump. As part of the development effort, a prototype system was built, which consisted of a radial magnetic bearing, an axial air gap motor, and a pivot bearing to constrain the axial motion. The following testing has been completed to validate the design. First, hydraulic tests have demonstrated sufficient hydraulic performance. Second, preliminary in vitro evaluation of hemolysis was low compared to that of a BioPump control. Third, a 6 h in vivo experiment was successfully completed.

Maximal exercise capacity and peripheral skeletal muscle function following lung transplantation

BACKGROUND

There have been many suggestions that diminished exercise capacity in patients that have undergone lung transplantation is due, in part, to peripheral muscle dysfunction, brought on by either detraining or immunosuppressive therapy. There is limited data quantifying skeletal muscle function in this population, especially in those more than 18 months post-procedure. The present study sought to quantitate skeletal muscle function and cardiopulmonary responses to graded exercise in 19 lung transplant recipients, 15 of which were mostly more than 18 months post-procedure.

METHODS

Ten single- (SLT) and 9 double-lung transplantation (DLT) underwent anthropometric measures and performed expiratory spirometry, whole body plethysmography to assess lung volumes, static maximal mouth pressures to assess respiratory muscle strength, progressive exercise testing on a cycle ergometer (with cardiac output measurements being performed every second workload) and isokinetic cycling to assess peripheral muscle power and work capacity.

RESULTS

The DLT group was younger than the SLT group (23.0 [21.0-32.0] vs 47.5 [43.0-55.0] median [interquartile range], p < .05) with no differences in height, weight, or BMI. Despite the DLT group having significantly better spirometric values (FEV1: 86% vs 56.5% median) and less airtrapping (RV/TLC: 30% vs 53.5%), both groups were equally limited in exercise capacity (Wmax)(38.0 percent predicted [30.0-65.0] vs 37.5 percent predicted [30.0-44.0], SLT vs DLT), leg power (76.1 percent predicted [53.8-81.4] vs 69.0 percent predicted [58.3-76.0]) and leg work capacity (63.3 percent predicted [34.7-66.8] vs 38.4 percent predicted [27.5-57.3]). This lack of difference in performance persisted when the analysis was limited to those more than 18 months post-procedure. Respiratory muscle strength was also not different for the two groups, and was within normal limits. Wmax was best correlated with leg work capacity (r = .84), but also with leg power, RV/TLC, FEV1 (r = .49, -.52, .58). When normalized for age, height, and sex, percent predicted Wmax only correlated with percent predicted leg work capacity (r = .58). Cardiac output was appropriate for the work performed.

CONCLUSIONS

We conclude that peripheral skeletal muscle work capacity is reduced following lung transplantation and mostly responsible for the limitation of exercise performance. While the causes of muscular dysfunction have yet to be clarified, the preservation of respiratory muscle strength with the concomitant reduction in leg power and work capacity suggests that most of the muscular dysfunction post-transplantation is attributable to detraining.