Mickaël Martin

Influence of norepinephrine and phenylephrine on frontal lobe oxygenation during cardiopulmonary bypass in patients with diabetes.

OBJECTIVE Although utilization of vasopressors recently has been associated with reduced cerebral oxygenation, the influence of vasopressors on cerebral oxygenation during cardiopulmonary bypass in patients with diabetes is unknown. The aim of this study was to document the impact of norepinephrine and phenylephrine utilization on cerebral oxygenation in patients with and without diabetes during cardiopulmonary bypass. DESIGN Prospective, clinical study. SETTING Academic medical center. PARTICIPANTS Fourteen patients with diabetes and 17 patients without diabetes undergoing cardiac surgery. INTERVENTIONS During cardiopulmonary bypass, norepinephrine (diabetics n = 6; non-diabetics n = 8) or phenylephrine (diabetics n = 8; non-diabetics n = 9) was administered intravenously to maintain mean arterial pressure above 60 mmHg. MEASUREMENTS AND MAIN RESULTS Mean arterial pressure, venous temperature, arterial oxygenation, and frontal lobe oxygenation (monitored by near-infrared spectroscopy) were recorded before anesthesia induction (baseline) and continuously during cardiopulmonary bypass. Frontal lobe oxygenation was lowered to a greater extent in diabetics versus non-diabetics with administration of norepinephrine (-14±13 v 3±12%; p<0.05). There was also a trend towards a greater reduction in cerebral oxygenation in diabetics versus non-diabetics with administration of phenylephrine (-12±8 v -6±7%; p = 0.1) during cardiopulmonary bypass. CONCLUSIONS Administration of norepinephrine to restore mean arterial pressure during cardiopulmonary bypass is associated with a reduction in frontal lobe oxygenation in diabetics but not in patients without diabetes. Administration of phenylephrine also were associated with a trend towards a greater reduction in frontal lobe oxygenation in diabetics. The clinical implications of these findings deserve future consideration.

Acute Effects of Low-Load/High-Repetition Single-Limb Resistance Training in COPD.

Exercising small muscle groups at a time allows higher muscle specific workloads compared with whole body aerobic exercises in people with chronic obstructive pulmonary disease (COPD). Whether similar effects also occur with partitioning exercise during low load/high-repetition resistance exercises is uncertain. PURPOSE To investigate the acute effects of partitioning exercise on exercise workload, exertional symptoms and quadriceps muscle fatigue during low load/high-repetition resistance exercises in people with COPD and healthy controls. METHODS We compared the acute physiological effects of single-limb (SL) versus two-limb (TL) execution of isokinetic knee extension and of six low load/high-repetition elastic resistance exercises in 20 people with COPD (forced expiratory volume in 1 s = 38% predicted) and 15 healthy controls. RESULTS Among people with COPD, SL exercises resulted in higher exercise workloads during isokinetic knee extension (17% ± 31%, P < 0.05) and elastic exercises (rowing, 17% ± 23%; leg curl, 23% ± 21%; elbow flexion, 19% ± 26%; chest press, 14% ± 15%; shoulder flexion, 33% ± 24%; and knee extension, 24% ± 18%, all P < 0.05). Muscle fatigue ratings were similar during SL compared with TL exercises, whereas dyspnea ratings were similar between conditions during isokinetic exercises and lower during SL compared with TL elastic exercises (P < 0.05). In COPD, SL knee extension resulted in greater quadriceps fatigue than TL knee extension as evidenced by a greater fall in quadriceps potentiated twitch force after the former exercise (-24% ± 10% vs -16% ± 8%, P = 0.025). In healthy controls, partitioning exercise with SL exercise did not modify workload, quadriceps fatigue nor dyspnea achieved during the various exercises. CONCLUSIONS Partitioning exercise by exercising using an SL allowed higher muscle localized exercise workloads, larger amount of quadriceps muscle fatigue with lower, or similar level of exertional symptoms during low load/high-repetition resistance exercises in people with advanced COPD.

Ectopic fat accumulation in patients with COPD: an ECLIPSE substudy

Background Obesity is increasingly associated with COPD, but little is known about the prevalence of ectopic fat accumulation in COPD and whether this can possibly be associated with poor clinical outcomes and comorbidities. The Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints (ECLIPSE) substudy tested the hypothesis that COPD is associated with increased ectopic fat accumulation and that this would be associated with COPD-related outcomes and comorbidities. Methods Computed tomography (CT) images of the thorax obtained in ECLIPSE were used to quantify ectopic fat accumulation at L2–L3 (eg, cross-sectional area [CSA] of visceral adipose tissue [VAT] and muscle tissue [MT] attenuation, a reflection of muscle fat infiltration) and CSA of MT. A dose–response relationship between CSA of VAT, MT attenuation and CSA of MT and COPD-related outcomes (6-minute walking distance [6MWD], exacerbation rate, quality of life, and forced expiratory volume in 1 second [FEV1] decline) was addressed with the Cochran–Armitage trend test. Regression models were used to investigate possible relationships between CT body composition indices and comorbidities. Results From the entire ECLIPSE cohort, we identified 585 subjects with valid CT images at L2–L3 to assess body composition. CSA of VAT was increased (P<0.0001) and MT attenuation was reduced (indicating more muscle fat accumulation) in patients with COPD (P<0.002). Progressively increasing CSA of VAT was not associated with adverse clinical outcomes. The probability of exhibiting low 6MWD and accelerated FEV1 decline increased with progressively decreasing MT attenuation and CSA of MT. In COPD, the probability of having diabetes (P=0.024) and gastroesophageal reflux (P=0.0048) at baseline increased in parallel with VAT accumulation, while the predicted MT attenuation increased the probability of cardiovascular comorbidities (P=0.042). Body composition parameters did not correlate with coronary artery scores or with survival. Conclusion Ectopic fat accumulation is increased in COPD, and this was associated with relevant clinical outcomes and comorbidities.

Cardiorespiratory and muscle oxygenation responses to low-load/high-repetition resistance exercises in COPD and healthy controls

Single-limb exercises have been used as a strategy to improve aerobic exercise tolerance in patients with chronic obstructive pulmonary disease (COPD) by alleviating the cardiopulmonary demand. We asked whether this strategy would also apply to cardiorespiratory demand and amount of work performed during single-limb and two-limb low-load/high-repetition resistance exercises in 20 patients with COPD [forced expiratory volume in 1 s (FEV1) = 1.0 liters, 38% of predicted] and 15 age-, sex-, and activity-matched healthy controls. Peak ventilation, peak oxygen consumption (V̇o2), and peak heart rate (HR) were assessed to document cardiorespiratory demand during shoulder flexion and knee extension exercises while exercise tolerance was assessed by the total amount of work achieved. In addition, changes in myoglobin-deoxyhemoglobin level (Δdeoxy-[Hb/Mb]) were measured during single-limb knee extension. In COPD, single-limb shoulder flexion and knee extension elicited higher localized workloads than two-limb exercises (21 and 24% higher workloads for the former exercise) while cardiopulmonary demand was 8-16% higher during two-limb exercises. When expressed as a percentage of peak values achieved during incremental cycle ergometry, peak V̇O2 and HR were similarly high during single-limb shoulder flexion and knee extension exercises, representing 90% of peak HR and 60% of peak V̇O2. Apart from single-limb knee extension, cardiorespiratory demand per kilogram work during low-load/high-repetition knee extension and shoulder flexion exercises was higher in patients with COPD than in healthy controls (range 27-122%, P < 0.0125). Δdeoxy-[Hb/Mb] of the quadriceps during knee extension was similar between the two groups, while Δdeoxy-[Hb/Mb] per kilogram work was higher in patients with COPD. We conclude that 1) in patients with COPD, single-limb exercises resulted in lower peak cardiorespiratory demand as well as higher localized workloads compared with two-limb exercises; 2) compared with healthy controls, the cardiorespiratory demand, either expressed per unit of work or relative to peak capacity, was higher in patients with COPD than in controls during low-load/high-repetition resistance exercises, irrespective of the involvement of one or two limbs or of the upper or lower extremity; 3) quadriceps muscle deoxygenation per unit of work during low-load/high-repetition knee extension was increased in COPD compared with controls; and 4) single- and two-limb low-load/high-repetition knee extension and shoulder flexion resistance exercises imposed a similar burden on the cardiorespiratory system, resulting in a higher cardiorespiratory demand per kilogram work performed during shoulder flexion compared with knee extension, in both COPD and healthy controls. NEW & NOTEWORTHY In chronic obstructive pulmonary disease (COPD), single-limb knee extension and shoulder flexion resulted in a lower peak cardiorespiratory response as well as larger localized exercise workloads compared with two-limb exercises. Cardiorespiratory and quadriceps deoxygenation cost per kilogram work was greater in COPD compared with healthy controls, despite similar acute responses. Compared with knee extension, shoulder flexion imposed a similar burden on the cardiorespiratory system in patients with COPD and healthy controls.