Tracheal tube obstruction in mechanically ventilated patients assessed by high-resolution computed tomography.

BACKGROUND: Tracheal intubation compromises mucus clearance and secretions accumulate inside the tracheal tube (TT). The aim of this study was to evaluate with a novel methodology TT luminal obstruction in critically ill patients. METHODS: This was a three-phase study: (1) the authors collected 20 TTs at extubation. High-resolution computed tomography (CT) was performed to determine cross-sectional area (CSA) and mucus distribution within the TT; (2) five TTs partially filled with silicone were used to correlate high-resolution CT results and increased airflow resistance; and (3) 20 chest CT scans of intubated patients were reviewed for detection of secretions in ventilated patients' TT. RESULTS: Postextubation TTs showed a maximum CSA reduction of (mean±SD) 24.9±3.9% (range 3.3 to 71.2%) after a median intubation of 4.5 (interquartile range 2.5 to 6.5) days. CSA progressively decreased from oral to lung end of used TTs. The luminal volume of air was different between used and new TTs for all internal diameters (P<0.01 for new vs. used TTs for all studied internal diameters). The relationship between pressure drop and increasing airflow rates was nonlinear and depended on minimum CSA available to ventilation. Weak correlation was found between TT occlusion and days of intubation (R²=0.352, P=0.006). With standard clinical chest CT scans, 6 of 20 TTs showed measurable secretions with a CSA reduction of 24.0±3.9%. CONCLUSIONS: TT luminal narrowing is a common finding and correlates with increased airflow resistance. The authors propose high-resolution CT as a novel technique to visualize and quantify secretions collected within the TT lumen.

Increasing humidity affects thermoregulation during low-intensity exercise in women.

INTRODUCTION: Women increasingly occupy manual labor jobs. However, research examining women working under hot-humid conditions is lacking. Therefore, the purpose of our study was to assess how increasing relative humidity (RH) affects women's thermoregulation during low-intensity exercise characteristic of 8 h self-paced manual labor. METHODS: There were 10 women (age: 23 ± 2 yr; body-surface area: 1.68 ± 0.13 m²; Vo2max: 46 ± 6 ml · kg⁻¹ · min⁻¹) who walked 90 min at 35% Vo2max in 35°C at 55% RH (55RH), 70% RH (70RH), and 85% RH (85RH). Investigators obtained: 1) rectal temperature (Tre), mean-weighted skin temperature (Tsk), and heart rate every 5 min; and 2) respiratory measures every 30 min. RESULTS: Heat production (H) and required rate of evaporative cooling (Ereq) remained constant among trials; each RH increment significantly decreased evaporative heat loss (E), but increased heart rate and sweat rate. All other calorimetric and thermometric variables were similar between 55RH and 70RH, but significantly greater in 85RH. Tre only exceeded 38°C in 85RH after walking ∼80 min. Combined, dry and respiratory heat losses only compensated for <30% of the decreases in E. CONCLUSION: Women exercising at low intensities in 35°C experienced most statistically significant physiological changes after 70RH. As H and Ereq remained constant across trials, heat storage increased with each 15% rise in RH because dry and respiratory heat losses minimally offset decreased E. Higher Tre, Tsk, and resultantly higher sweat rates reflected heat storage increases as E decreased in each trial. Overall, at 35°C Ta, we found women exercising for 90 min at low intensities remained at safe rectal temperatures up to 70% RH.

Influence of rest intervals after assisted jumping on bodyweight vertical jump performance.

Assisted jumping (an overspeed concept) is a method used to improve vertical jump performance. However, research is lacking on the optimal program design to maximize performance outcomes. The purpose of this study was to determine the influence of rest intervals after assisted jumping on bodyweight (BW) vertical jumps. Twenty healthy recreationally trained men (age: 22.85 ± 1.84 years; height: 179.44 ± 5.99 cm; mass: 81.73 ± 9.51 kg) attended 5 sessions. For all sessions, subjects performed the same dynamic warm-up and then executed 1 set of 5 consecutive assisted jumps at 30% BW reduction. They then rested for 30 seconds (C30), 1 minute (C1), 2 minutes (C2), or 4 minutes (C4), followed by 3 BW jumps with no assistance. Baseline (CB) jump height was measured without preceding assisted jumps. Analyses of variance revealed a main effect for takeoff velocity, with 1 and 4 minutes being greater than baseline (C1: 3.36 ± 0.40 m·s(-1); C4: 3.27 ± 0.41 m·s(-1); CB: 3.13 ± 0.32 m·s(-1)). Relative peak power also demonstrated a main effect, with 1 minute being greater than all other conditions (C1: 75.22 ± 10.83 W·kg(-1)). Jump height and relative ground reaction force demonstrated no differences between conditions. These results indicate overspeed jumping acutely enhances explosive BW jumping velocity and power. This acute performance enhancement is probably a result of increased motor neuron excitability and motor unit synchronization.