Passive smoking acutely affects the microcirculation in healthy non-smokers.

OBJECTIVE: Acute effects of passive smoking on microcirculation have not been sufficiently studied. The aim of the present study was to detect microcirculatory alterations in healthy non-smokers after passive exposure to cigarette smoke, utilizing the Near Infrared Spectroscopy method combined with the vascular occlusion technique. METHODS: Sixteen (9 females, age: 34 ±â€¯9 years) non-smoking, healthy volunteers were exposed to passive smoking for 30 min in a temperature-controlled environment. Smoke concentration was monitored with a real-time particle counter. The following microcirculatory parameters were estimated: baseline tissue oxygen saturation (StO2); StO2 decrement after vascular occlusion (indicating the oxygen consumption rate); StO2incremental response after vascular occlusion release (reperfusion rate); the time period where the StO2 signal returns to the baseline values after the hyperemic response. RESULTS: Baseline StO2 (79.6 ±â€¯6.4 vs. 79 ±â€¯8%, p = 0.53) as well as the time needed for StO2 to return to baseline levels (138.2 ±â€¯26.5 vs. 142.1 ±â€¯34.6 s, p = 0.64) did not significantly differ before vs. after passive smoking exposure. Oxygen consumption rate decreased after 30 min exposure to passive smoking (from 12.8 ±â€¯4.2 to 11.3 ±â€¯2.8%/min, p = 0.04); Reperfusion rate also significantly decreased (from 5.6 ±â€¯1.8 to 5 ±â€¯1.7%/s, p = 0.04). CONCLUSIONS: Our results suggest that acute exposure to passive smoking delays peripheral tissue oxygen consumption and adversely affects microcirculatory responsiveness after stagnant ischemia in healthy non-smokers.

Left ventricular diastolic dysfunction--an independent risk factor for weaning failure from mechanical ventilation.

The objective of this study was to investigate the contribution of left ventricular (LV) diastolic dysfunction to weaning failure, along with the levels of the currently used cardiac biomarkers. Forty-two mechanically ventilated patients, who fulfilled criteria for weaning from mechanical ventilation (MV), underwent a two-hour spontaneous breathing trial (SBT). Transthoracic echocardiography (TTE) was performed before the start of the SBT. The grade of LV diastolic dysfunction was assessed by pulsed-wave Doppler and tissue Doppler imaging at the level of the mitral valve. Haemodynamic and respiratory parameters were recorded. Blood levels of B-type natriuretic peptide (BNP), troponin I, creatine kinase-MB, and myoglobin were measured on MV and at the end of the SBT. Weaning success was defined as the patient's ability to tolerate spontaneous breathing for more than 48 hours. Fifteen patients failed to wean. LV diastolic dysfunction was significantly associated with weaning failure (P<0.001). The grade of diastolic dysfunction was significantly correlated with BNP levels both on MV and at the end of the SBT (P<0.001, r=0.703 and P<0.001, r=0.709, respectively). BNP levels on MV were lower in patients who successfully weaned compared to those who did not (361±523 ng/l versus 643±382 ng/l respectively, P=0.008). The presence of diastolic dysfunction was independently associated with weaning failure (odds ratio [OR] 11.23, confidence interval [CI] 1.16-109.1, P=0.037) followed by respiratory frequency/tidal volume (OR 1.05, CI 1.00-1.10, P=0.048). Therefore, assessment of LV diastolic function before the start of weaning could be useful to identify patients at risk of weaning failure.

Oxygen consumption and heart rate responses during and after constant load and alternating intensity exercise at 105% of lactate threshold.

AIM: The purpose of this study was a secondary-analysis of previously published data, in order to compare the acute VO2 responses, the time spent at high percentage of VO2max and total VO2 consumed (TVO2) between constant and alternating intensity exercise of the same intensity and duration. This study also aimed to examine VO2 and heart rate (HR) responses one hour after both exercises. METHODS: Ten recreationally trained men (24.7±4.7 years) completed the following two exercise tests lasting an hour each and having the same mean intensity at 105% of lactate threshold (70% VO2max): 1) constant load cycling (CON), and 2) alternating intensity exercise (ALT), during which 40 seconds of light exercise (47% VO2max) were alternated with 20 seconds of supramaximal intensity at 120% of VO2max. RESULTS: TVO2 (69.89±7.02 vs. 58.22±9.13 mL/kg/min, P=0.03) and HR (142±16, 128±12, P=0.04) was higher in CON exercise compared to ALT. All participants reached 70% and 80% of VO2max irrespective of the exercise protocol. In ALT exercise the time spent at 90% was higher compared to CON exercise (70.81±21.37 vs. 36.88±11.88 seconds). Also, TVO2 recovery values after ALT exercise was higher compared to CON (11.1 ±2.93 vs. 9.94±3.54 mL/kg/min). CONCLUSION: ALT exercise allowed participants to spend longer time at 90% of VO2max, even if TVO2 in CON exercise was higher, suggesting that in ALT exercise greater aerobic stress (as based on exercise intensity) is imposed on the athletes. While VO2 recovery values were higher in ALT compared to CON, indicating different substrate utilization during and after exercise.