The ventilatory and cardiac function do not appear negatively affected by SG; thus, we hypothesize that the decrease in aerobic capacity could be due to alterations in peripheral muscles. This might in part be due to a loss of muscle mass, although our patients' muscle strength did not decrease. Pilot results from VO-kinetics analysis seem to support the hypothesis of a deterioration of oxidative muscle metabolism after SG.
Backgrounds: The effects of acute blood volume expansion (BVE) on the respiratory mechanics of normal animals have been not extensively studied. The subject is of both theoretical and practical interest since BVE is a frequent medical intervention, and the associated increase in cardiac output may occur in different physiopathological situations. Objectives: To describe the changes in the parameters of respiratory mechanics occurring as an effect of acute BVE and the related increase in cardiac output. Methods: We applied the end-inflation occlusion method in normal, positive pressure-ventilated rats to measure the respiratory mechanics under control and BVE conditions. Results: Under BVE conditions, we found a statistically significant increase in static respiratory system elastance (Est,rs), ohmic airway resistance plus resistance of respiratory system tissues to movement (Rmin,rs), and overall resistance including pendelluft and stress relaxation effects (Rmax,rs). Under BVE conditions, the resistive component due to sole stress relaxation and pendelluft (Rvisc,rs) increased almost significantly while a significant increment in mean respiratory system hysteresis surface area (Hyrs) was also found. Conclusions: Increasing pulmonary blood flow by BVE increases the mechanical work of breathing because of the effects on Est,rs, Rmin,rs and Rmax,rs, and because of the increase in Hyrs.
Purpose: Previous data suggest that tronco-conical cuffs should be used for accurate blood pressure (BP) measurement in the obese. However, not only arm size but also its shape may affect the accuracy of BP measurement when a cylindrical cuff is used. Methods: In 197 subjects with arm circumference >32 cm, and 157 subjects with arm circumference 32 cm, the upper-arm was considered as formed from two truncated cones and the frustum slant angles of the proximal (upper angle) and distal (middle angle) truncated cones were measured. Five cylindrical and five tronco-conical cuffs of appropriate size in relation to arm circumference were used. Results: In the group with large arm, the upper slant angle was greater than the middle angle (86.5 ± 1.7 versus 84.7 ± 2.3 ), whereas in the group with normal arm the two angles were similar. In the former group, the cylindrical cuff overestimated BP by 2.5 ± 5.4/1.7 ± 4.7 mmHg, whereas in the latter negligible between-cuff BP discrepancies were found. In the whole sample, BP discrepancies between the cylindrical and the tronco-conical cuffs correlated with both arm size and shape, considered as the difference between the upper and middle slant angles (all p < 0.0001). Among the participants with large arm, the between-cuff BP discrepancies increased progressively with increasing upper-middle angle difference (3.75 ± 0.38/ 2.78 ± 0.32 mmHg for the top tertile, p < 0.001/<0.001). Conclusions: These data indicate that in people with large upper arms, the tronco-conical shape of the arm is more pronounced on the lower than the upper half, a feature that amplifies the BP measurement error when cylindrical cuffs are used.
Introduction Sleeve gastrectomy (SG) has become a widespread treatment option in patients affected by severe obesity. However, studies investigating the impact of the subsequent weight loss on the ventilatory response at rest and during physical exercise are lacking. Methods This is an observational study on 46 patients with severe obesity (76% females), comparing parameters of ventilatory function 1 month before and 6 months after SG. Patients were first evaluated by resting spirometry and subsequently with an incremental, maximal cardiopulmonary exercise test (CPET) on treadmill. Results The important weight loss of 26.35 ± 6.17% of body weight (BMI from 43.59 ± 5.30 to 32.27 ± 4.84 kg/m2) after SG was associated with a significant improvement in lung volumes and flows during forced expiration at rest, while resting ventilation and tidal volume were reduced (all p ≤ 0.001). CPET revealed decreased ventilation during incremental exercise (p < 0.001), with a less shallow ventilatory pattern shown by a lower increase of breathing frequency (∆BFrest to ATp = 0.028) and a larger response of tidal volume (∆TVAT to Peakp < 0.001). Furthermore, a concomitant improvement of the calculated dead space ventilation, VE/VCO2 slope and peripheral oxygen saturation was shown (all p ≤ 0.002). Additionally, the increased breathing reserve at peak exercise was associated with a lower absolute oxygen consumption but improved exercise capacity and tolerance (all p < 0.001). Conclusion The weight loss induced by SG led to less burdensome restrictive limitations of the respiratory system and to a reduction of ventilation at rest and during exercise, possibly explained by an increased ventilatory efficiency and a decrease in oxygen demands.
Purpose Obstructive sleep apnea (OSA) is a widespread comorbidity of obesity. Nasal continuous positive airway pressure (CPAP) has been demonstrated very effective in treating patients with OSA. The aims of this study were to investigate whether or not cardiopulmonary exercise testing (CPET) can characterize patients with OSA and to evaluate the effect of nasal CPAP therapy. Methods An observational study was conducted on patients with moderate to severe obesity and suspected OSA. All patients underwent cardiorespiratory sleep study, spirometry, and functional evaluation with ECG-monitored, incremental, maximal CPET. Results Of the 147 patients, 94 presented with an apnea–hypopnea index (AHI) ≥ 15 events/h and were thus considered to have OSA (52 receiving nasal CPAP treatment; 42 untreated) while 53 formed a control group (AHI < 15 events/h). Patients with untreated OSA showed significantly lower oxygen uptake (VO2), heart rate, minute ventilation (VE), and end tidal carbon dioxide (PETCO2) at peak exercise compared to controls. Patients receiving nasal CPAP showed higher VE and VO2 at peak exercise compared to untreated patients. A difference in PETCO2 between the maximum value reached during test and peak exercise (ΔPETCO2 max-peak) of 1.71 mmHg was identified as a predictor of OSA. Conclusion Patients with moderate to severe obesity and untreated OSA presented a distinctive CPET-pattern characterized by lower aerobic and exercise capacity, higher PETCO2 at peak exercise associated with a lower ventilatory response. Nasal CPAP treatment was shown to positively affect these cardiorespiratory adaptations during exercise. ΔPETCO2 max-peak may be used to suggest OSA in patients with obesity.
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