Implication des facteurs cardiorespiratoires dans l’intolérance à l’effort de l’adolescent obèse

Introduction

To identify the parameters, which can explain the effort intolerance in young obese during standard cardiorespiratory evaluation at rest and exercise.

Synthesis

Fourty-two obese (degree 2) adolescents systematically underwent pulmonary function measurements and maximal graded exercise on ergocycle. Two subgroups were drawn on the basis of their VO2peak${\text{V}}_{{\text{O}}_{\text{2peak}}}$ (‘normal’ group: N is greater than 80% of predictive value, n = 14;‘abnormal’ group: A is less than 80% of predictive value) and compared for all the measured parameters. Forced vital capacity (FVC) and forced expiratory volume in the first second (FEV₁) though in the lower normal range were lower in A compared to N (P = 0.01 and P = 0.02, respectively). At the end of maximal exercise, maximal VT/FVC (P = 0.001) and VO2peak${\text{V}}_{{\text{O}}_{\text{2peak}}}$/HR_max (P = 0.04) obtained in A are lower too. VO2peak${\text{V}}_{{\text{O}}_{\text{2peak}}}$ was correlated to lean mass and spirometric data. In addition, spirometric data correlated with VO2peak${\text{V}}_{{\text{O}}_{\text{2peak}}}$/HR_max.

Conclusion

These results emphasized the possible involvement of ventilatory factors and the stress they may impose to central cardiovascular system in exercise intolerance of obese adolescent.     

Volumetric-modulated arc stereotactic body radiotherapy for prostate cancer: dosimetric impact of an increased near-maximum target dose and of a rectal spacer

Objective:

In volumetric-modulated arc therapy (VMAT) prostate stereotactic body radiotherapy (SBRT), dose coverage of the planning target volume (PTV) becomes challenging when the sparing of rectum, bladder and urethra is strictly pursued. Our current 35-Gy-in-five-fraction plans only assure 33.2 Gy to ≥95% PTV (V33.2PTV ≥ 95%). Looking for an improved V33.2PTV, increased near-maximum target dose (D_2%) and prostate–rectum spacer insertion were tested.

Methods:

For 11 patients, two VMAT plans, with D_2% ≤ 37.5 Gy (Hom) or D_2% ≤ 40.2 Gy (Het), on each of two CT studies, before or after spacer insertion, were computed. All plans assured V33.2PTV ≥95%, and <1 cm³ of rectum, bladder and urethra receiving ≥35 Gy. By hypothesis testing, several dose–volume metrics for target coverage and rectal sparing were compared across the four groups of plans. The impact of spacer insertion on the fractions of rectum receiving more than 18, 28 and 32 Gy (VXr) was further tested by linear correlation analysis.

Results:

By hypothesis testing, the increased D_2% was associated with improvements in target coverage, whereas spacer insertion was associated with improvements in both target coverage and rectal VXr. By linear correlation analysis, spacer insertion was related to the reductions in rectal VXr for X ≥ 28 Gy.

Conclusion:

A slightly increased D_2% or the use of spacer insertion was each able to improve V33.2PTV. Their combined use assured V33.2PTV ≥ 98% to all our patients. Spacer insertion was further causative for improvements in rectal sparing.

Advances in knowledge:

For VMAT plans in prostate SBRT, the distinct dosimetric usefulness of increased D_2% and of the use of spacer insertion were validated in terms of target coverage and rectal sparing.     

Puissance critique de l’enfant prépubère et de l’adulte

Aim

The aim of the study was to compare aerobic and anerobic abilities of prepubertal children and adults with the critical power concept.

Methods

Sixteen children (10.3 ± 0.9 years) and 15 adults (23.5 ± 3.6 years) performed five tests: a maximal-graded test and four constant load exercises until exhaustion. Critical power (CP) and anaerobic-work capacity (CTA) were determined from the power-1/time (P-t) linear relationship.

Results

Determination coefficients for P-t were 0.94 ± 0.05 in children and 0.96 ± 0.04 in adults. PC values were significantly (p < 0.01) lower in children (2.7 ± 0.4 W/kg) than in adults (3.1 ± 0.3 W/kg). CTA values were significantly (p < 0.001) lower in children (136.4 ± 50.8 J/kg) than in adults (247.1 ± 45.7 J/kg).

Conclusion

Satisfying determination coefficients for CP and CTA were found in children and adults. Children have a lower CP and CTA than adults. This result is in accordance with literature.     

Effets d'une restriction hydrique et alimentaire prolongée (ramadan) sur la performance et les réponses cardiovasculaires au cours d'un exercice incrémental en milieu tropical chaud

Backgroung

Previous studies showed that maximal oxygen uptake and maximal heart rate were not different during prolonged fasting (ramadan) compared to normal feeding period. However, the effect of ramadan on the blood pressure response during incremental exercise has not been investigated.

Objective

This study aimed to evaluate the evolution of blood pressure during incremental trial in ramadan period.

Methods

Twelve young trained male aged 24 ± 4 yrs participated as voluntary subjects. Their anthropometric parameters, maximal aerobic power and maximal heart were measured in fasting and in normal feeding periods during incremental trial on cycle ergometer.

Results

No significant difference was observed in any anthropometric parameter. Maximal aerobic power of fasting period was significantly less (P < 0,05) compared to normal feeding. Heart rate at rest, at maximal exercise and during a 15 min period of recovery was not significantly affected. Systolic blood pressure of fasting period at maximal power was significantly lower than during the control period (P < 0,05).

Conclusion

Ramadan negatively influences the capacity of maximal power and cardiovascular response at maximal power.     

Dynamic contrast enhancement magnetic resonance imaging (DCE-MRI) for differential diagnosis in head and neck cancers

Purpose

To examine the potential of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) for differential diagnosis of head and neck cancer.

Methods and materials

DCE-MRI was performed in 26 patients with untreated squamous cell carcinoma (SCC), 28 undifferentiated carcinoma (UD) and 8 lymphoma. DCE-MRI was analyzed with the pharmacokinetic model proposed by Tofts and Kermode to produce the three DCE parameters: k_trans, ve$v_e$ and vp$v_p$. Areas under the curve (AUC) at the initial 60 and 90 s (AUC60 and AUC90) were also recorded. Histogram analysis was conducted to obtain the mean, 25%, 50%, 75% and 95% percentile values and the Kruskal–Wallis test was used to compare the DCE parameters between the three groups of cancer.

Results

k_trans, AUC60 and AUC90 showed significant differences (p < 0.01) between UD/SCC and UD/lymphoma, but not between SCC/lymphoma. The mean AUC90 demonstrated the highest accuracy of 78% (sensitivity of 68% and specificity of 88%) for distinguishing UD and SCC, and the 75% percentile AUC90 provided the highest accuracy of 97% (sensitivity of 100% and specificity of 88.5%) for distinguishing UD and lymphoma.

Conclusions

There are significant differences in the DCE parameters which show the potential for distinguishing UD from SCC or lymphoma.