Eva Bernardi

Treadmill walking speed and survival prediction in men with cardiovascular disease: a 10-year follow-up study

Objective To determine whether the walking speed maintained during a 1 km treadmill test at moderate intensity predicts survival in patients with cardiovascular disease. Design Population-based prospective study. Setting Outpatient secondary prevention programme in Ferrara, Italy. Participants 1255 male stable cardiac patients, aged 25–85 years at baseline. Main outcome measures Walking speed maintained during a 1 km treadmill test, measured at baseline and mortality over a median follow-up of 8.2 years. Results Among 1255 patients, 141 died, for an average annual mortality of 1.4%. Of the variables considered, the strongest predictor of all-cause mortality was walking speed (95% CI 0.45 to 0.75, p<0.0001). Based on the average speed maintained during the test, participants were subdivided into quartiles and mortality risk adjusted for confounders was calculated. Compared to the slowest quartile (average walking speed 3.4 km/h), the relative mortality risk decreased for the second, third and fourth quartiles (average walking speed 5.5 km/h), with HRs of 0.73 (95% CI 0.46 to 1.18); 0.54 (95% CI 0.31 to 0.95) and 0.20 (95% CI 0.07 to 0.56), respectively (p for trend <0.0001). Receiver operating curve analysis showed an area under the curve of 0.71 (p<0.0001) and the highest Youden index (0.35) for a walking speed of 4.0 km/h. Conclusions The average speed maintained during a 1 km treadmill walking test is inversely related to survival in patients with cardiovascular disease and is a simple and useful tool for stratifying risk in patients undergoing secondary prevention and cardiac rehabilitation programmes.

Peak oxygen uptake prediction from a moderate, perceptually regulated, 1-km treadmill walk in male cardiac patients.

PURPOSE: To determine whether a moderate 1-km treadmill walking test (1KTWT) could be used to predict peak oxygen uptake ( O2peak) in patients with cardiovascular disease. METHODS: One hundred seventy-eight male patients, aged 38 to 83 years, completed a O2peak treadmill test and a 1KTWT using a self-regulated intensity of 11 to 13 of 20 on the Borg scale. Multivariable regression analysis was used to develop equations for predicting O2peak in a development group (n = 110), both for subjects prescribed and not prescribed a &bgr;-blocking agent (BB/NBB, 66/44). These equations were then applied to a cross-validation and reproducibility group (n = 68, BB/NBB, 37/31), who completed the protocol twice within 2 weeks. RESULTS: Analysis from 1KTWT in the development group showed that age, body mass index, walking speed, and heart rate were the most potent predictors of O2peak. Measured and predicted O2peak were not significantly different, and were strongly associated among both the NBB (r = 0.81, P < .0001) and BB (r = 0.69, P < .0001) groups, with a mean residual of approximately 1.0 mL·kg−1·min−1. When applied to the cross-validation and reproducibility group, the equations similarly yielded strong associations (r = 0.64, P < 0.001 and r = 0.71, P < 0.001 for the NBB and BB groups, respectively), with no significantly differences between measured and predicted O2peak. Mean test-retest differences for measured and predicted O2peak were between 0.1 and −0.5 mL·kg−1·min−1. CONCLUSIONS: Equations developed from the 1KTWT accurately predicted O2peak in patients with cardiovascular disease. The model may represent a valid, low cost, and simple tool for indirect estimations of cardiorespiratory fitness in an outpatient setting.

Association between VO2 peak estimated by a 1-km treadmill walk and mortality. A 10-year follow-up study in patients with cardiovascular disease

PURPOSE The aim of this study is to assess the association between peak oxygen uptake (VO2 peak), determined using a perceptually regulated 1-km walking test (1k-TWT), and all-cause mortality in cardiac patients. METHODS 1255 male patients, aged 25-85 years, completed a moderate 1k-TWT to estimate VO2 peak. Subjects were followed for all-cause mortality for up to 10 years. Cox proportional hazard models were employed to determine variables associated with mortality. Based on the estimated VO2 peak, the sample was subdivided into quartiles and mortality risks were calculated. To assess the discriminatory accuracy of the estimated VO2 peak for estimating survival, receiver-operating-characteristics curves were constructed. RESULTS During a median 8.2 year follow-up, a total of 141 deaths from any cause occurred, yielding an average annual mortality of 1.4%. The strongest predictor of all-cause mortality was the estimated VO2 peak (c-statistic 0.71, 95% confidence intervals: 0.69-0.74, P<0.0001). Survival decreased in a graded fashion from the highest estimated VO2 peak quartile to the lowest quartile. Compared to the lowest quartile, the hazard ratios (95% confidence intervals) for the second, third, and fourth quartiles were 0.77 (0.35-1.33), 0.43 (0.20-0.91), and 0.16 (0.05-0.54) respectively (P for trend <0.0001). An 89% reduction in mortality risk was observed among a subset of subjects in the fittest quartile who improved their estimated VO2 peak over the follow-up period relative to subjects in the least fit quartile who did not improve. CONCLUSION VO2 peak estimated by a novel 1k-TWT predicts survival in subjects with stable cardiovascular disease.

Long-Term Monitoring of Oxygen Saturation at Altitude Can Be Useful in Predicting the Subsequent Development of Moderate-to-Severe Acute Mountain Sickness

OBJECTIVE The use of pulse oximetry (Spo2) to identify subjects susceptible to acute mountain sickness (AMS) is the subject of debate. To obtain more reliable data, we monitored Spo2 for 24 hours at altitude to investigate the ability to predict impending AMS. METHODS The study was conducted during the climb from Alagna (1154 m) to Capanna Regina Margherita (4559 m), with an overnight stay in Capanna Gnifetti (3647 m). Sixty subjects (11 women) were recruited. Each subject was fitted with a 24-hour recording finger pulse oximeter. The subjects rode a cable car to 3275 m and climbed to 3647 m, where they spent the night. RESULTS In the morning, 24 subjects (6 women) had a Lake Louise Questionnaire score (LLS) ≥ 3 (AMS(+)), and 15 subjects (4 women) exhibited moderate-to-severe disease (LLS ≥ 5 = AMS(++)). At Alagna, Spo2 did not differ between the AMS(-) and AMS(+) subjects. At higher stations, all AMS(+) subjects exhibited a significantly lower Spo2 than did the AMS(-) subjects: at 3275 m, 85.4% vs 87.7%; resting at 3647 m, 84.5% vs 86.4%. The receiver operating characteristics curve analysis resulted in a rather poor discrimination between the AMS(-) subjects and all of the AMS(+) subjects. With the cutoff LLS ≥ 5, the sensitivity was 86.67%, the specificity was 82.25%, and the area under the curve was 0.88 (P < .0001) for Spo2 ≤ 84% at 3647 m. CONCLUSIONS We conclude that AMS(+) subjects exhibit a more severe and prolonged oxygen desaturation than do AMS(-) subjects starting from the beginning of altitude exposure, but the predictive power of Spo2 is accurate only for AMS(++).

Respiratory muscle training with normocapnic hyperpnea improves ventilatory pattern and thoracoabdominal coordination, and reduces oxygen desaturation during endurance exercise testing in COPD patients

Background Few data are available about the effects of respiratory muscle training with normocapnic hyperpnea (NH) in COPD. The aim is to evaluate the effects of 4 weeks of NH (Spirotiger®) on ventilatory pattern, exercise capacity, and quality of life (QoL) in COPD patients. Methods Twenty-six COPD patients (three females), ages 49–82 years, were included in this study. Spirometry and maximal inspiratory pressure, St George Respiratory Questionnaire, 6-minute walk test, and symptom-limited endurance exercise test (endurance test to the limit of tolerance [tLim]) at 75%–80% of peak work rate up to a Borg Score of 8–9/10 were performed before and after NH. Patients were equipped with ambulatory inductive plethysmography (LifeShirt®) to evaluate ventilatory pattern and thoracoabdominal coordination (phase angle [PhA]) during tLim. After four supervised sessions, subjects trained at home for 4 weeks – 10 minutes twice a day at 50% of maximal voluntary ventilation. The workload was adjusted during the training period to maintain a Borg Score of 5–6/10. Results Twenty subjects completed the study. After NH, maximal inspiratory pressure significantly increased (81.5±31.6 vs 91.8±30.6 cmH2O, P<0.01); exercise endurance time (+150 seconds, P=0.04), 6-minute walk test (+30 meters, P=0.03), and QoL (−8, P<0.01) all increased. During tLim, the ventilatory pattern changed significantly (lower ventilation, lower respiratory rate, higher tidal volume); oxygen desaturation, PhA, and dyspnea Borg Score were lower for the same work intensity (P<0.01, P=0.02, and P<0.01, respectively; one-way ANOVA). The improvement in tidal volume and oxygen saturation after NH were significantly related (R2=0.65, P<0.01). Conclusion As expected, NH improves inspiratory muscle performance, exercise capacity, and QoL. New results are significant change in ventilatory pattern, which improves oxygen saturation, and an improvement in thoracoabdominal coordination (lower PhA). These two facts could explain the reduced dyspnea during the endurance test. All these results together may play a role in improving exercise capacity after NH training.

Endothelial Function in COPD Is in an Intermediate Position Between Healthy Subjects and Coronary Artery Disease Patients and Is Related to Physical Activity

Patients with chronic obstructive pulmonary disease (COPD) have an increased risk of ischemic heart disease. Endothelial dysfunction may play a role in the onset of cardiovascular event. Previous studies showed an impaired endothelial function (measured by flow-mediated dilation, FMD) in COPD patients compared to healthy subjects. To the best of our knowledge no study has compared FMD in COPD and in cardiac (coronary artery disease, CAD) patients. We aimed to assess FMD in healthy subjects, COPD, CAD, and COPD + CAD. The main result is that FMD in COPD is reduced and is in an intermediate position between healthy subjects and CAD or COPD + CAD; this impairment can contribute to explain the higher prevalence of cardiovascular disease in COPD. The only determinant independently associated with FMD in all subjects is the physical activity level, irrespective of the traditional risk factors (i.e., smoke, dyslipidemia, hypertension).

Residence at Moderate Versus Low Altitude Is Effective at Maintaining Higher Oxygen Saturation During Exercise and Reducing Acute Mountain Sickness Following Fast Ascent to 4559 m

OBJECTIVE To continuously monitor oxygen saturation (SpO2) by pulse oximeter and assess the development of acute mountain sickness (AMS) using the Lake Louise Score (LLS) during ascent from 1154 to 4559 m in 2 groups of subjects: 10 moderate-altitude residents (MAR; ≥1000-≤2500 m) and 34 low-altitude residents (LAR). MAR are reported to have a lower incidence of AMS during ascent to higher altitudes compared with LAR. Whether this is related to higher SpO2 is still open to debate. METHODS Seventy subjects were recruited; 24-hour SpO2 monitoring with finger pulse oximetry was performed. All subjects rode a cable car from 1154 to 3275 m and then climbed to 3647 m, where 60 subjects (LAR) overnighted. The second day, 34/60 LAR reached the highest altitude. Ten subjects who lived permanently at 1100 to 1400 m (MAR) climbed directly to 4559 m without an overnight stop. RESULTS One LAR was excluded from the analysis because he performed a preacclimatization. We compared data of 10 MAR with data of 33 LAR who reached 4559 m. Two MAR had an LLS of 3, and 8 scored <3. Six LAR had an LLS of 3 to 4, 8 scored ≥5, and 19 scored <3. SpO2 monitoring showed higher mean SpO2 in MAR during ascent above 3600 m compared with LAR (MAR, 79±4% vs LAR, 76±5%; analysis of variance, P = .03). CONCLUSIONS The results of this preliminary study suggest that residence at moderate altitude allows maintenance of higher SpO2 and reduces risk of developing AMS during rapid ascent to higher altitude.

Oxygen Uptake Attenuation at Ventilatory Threshold in Men With Coronary Artery Disease.

PURPOSE: Maximal oxygen uptake ( O2) and ventilatory threshold (VT) are widely used to assess cardiorespiratory fitness in healthy people, as well as in patients with various clinical conditions. The aim of this study was to determine whether an attenuation of O2 occurs above the VT in patients with stable coronary artery disease. METHODS: A total of 33 male patients participating in an outpatient cardiac rehabilitation/secondary prevention program underwent maximal incremental cycle ergometry at increasing pedaling cadences up to the limit of tolerance. Ventilatory gas-exchange variables were measured breath by breath while work rate was recorded continuously. Ventilatory threshold was determined by a dual linear regression model (V-slope analysis). RESULTS: Four patients were excluded from the analysis because they were unable to pedal at the increasing cadences required by the protocol. The remaining 29 patients successfully completed the test without complications or evidence of significant ST segment depression. The slope of the O2/work rate relationship above the VT decreased significantly (−44.6% on average) in 23 of the 26 patients in which VT was able to be determined. O2 at the start of O2 attenuation ( O2 att) and at VT were highly correlated and in strong agreement (1637 ± 451 mL/min vs 1650 ± 473 mL/min, r 2 = 0.96, P < .01). CONCLUSIONS: O2att does occur and coincides with the VT in the majority of patients tested with stable coronary artery disease.

Unexplained dyspnea could be ascribable to postural changes

Here we present the cases of 3 females referred to our outpatient clinic complaining dyspnea during daily activity, in particular during walking. A careful history enabled us to determine that dyspnea was significantly reduced when they walked with upper-limb support. Subjects underwent respiratory function tests (FEV1, FVC, DLCO), chest X-ray, echocardiogram with non-invasive PAPs measurement, blood sample testing and ventilatory evaluation by means of portable respiratory inductive plethysmography (LifeShirt System, LS). LS accurately estimates ventilation, ventilatory pattern and the synchrony of rib cage-abdominal motion (phase angle, PhA) at rest and during exercise both in patients and in healthy subjects. Subjects performed six-minute walking tests (6MWT) with and without a rollator while equipped with LS. All exams were normal. LS evaluation during 6MWT showed an higher PhA during 6MWT without rollator: 26±11° and 17±3° without and with rollator respectively. During 6MWT without upper-limb support an evident increase in PhA was observed. This is an indicator of rib cage-abdominal motion asynchrony, which in turn could induce dyspnea. We suggest that postural change during walking without upper-limb support may occur in otherwise elderly subjects and this could explain the dyspnea.