Effect of residence at altitude on the perception of breathlessness on return to sea level in normal subjects

Timing of return from altitude training for optimal sea level performance

While a number of published studies exist to guide endurance athletes with the best practices regarding implementation of altitude training, a key unanswered question concerns the proper timing of return to sea level prior to major competitions. Evidence reviewed here suggests that, altogether, the deacclimatization responses of hematological, ventilatory, and biomechanical factors with return to sea level likely interact to determine the best timing for competitive performance.

Cardiopulmonary response and body composition changes after prolonged high altitude exposure in women

Weight loss in men is commonly observed during prolonged high altitude exposure as a result of a daily negative energy balance. Its amount depends mainly on duration of exposure, altitude reached, and level of physical activity. This reduction in body weight often comes with a loss of muscular mass, likely contributing to the decreased physical performance generally reported. Limited data is, however, available on body composition, functional capacity, and cardiopulmonary response to exercise after high altitude exposure in women. The aim of this study was to evaluate the effects of prolonged high altitude exposure on body composition and on cardiopulmonary response to maximal exercise in a group of young, moderately active women. Twelve female subjects, aged 21.5 ± 3.1 (mean ± SD), BMI 22.1 ± 1.9 kg · m(-2) and Vo(2max) 33.8 ± 3.5 mL · kg(-1) · min(-1), participated in this study, by residing for 21 days at high altitude (5050 m, Pyramid, EV-K(2)-CNR laboratory). Before and after high altitude exposure, all subjects underwent both a body composition evaluation using two methods (bioimpedance analysis and DEXA) and a functional evaluation based on a maximal exercise test on a cycle ergometer with breath-by-breath gas analysis. After high altitude exposure, data showed a slight, nonsignificant reduction in body weight, with an average 3:2 reduction ratio between fat and fat-free mass evaluated by DEXA, in addition to a significant decrease in Vo(2max) on the cycle ergometer test (p<0.01). Changes in Vo(2max) correlated to changes of leg muscle mass, evaluated by DEXA (r(2) = 0.72; p<0.0001). No changes were observed in the maximal heart rate, work capacity, and ventilatory thresholds, while the Vo(2)/W slope was significantly reduced (p<0.05). Finally, Ve/Vo(2) and VE/Vco(2max) slopes were increased (p<0.01), suggesting a possible long-term modulation of the exercise ventilatory response after prolonged high altitude exposure.

Respiratory and leg muscles perceived exertion during exercise at altitude

We compared the rate of perceived exertion for respiratory (RPE,resp) and leg (RPE,legs) muscles, using a 10-point Borg scale, to their specific power outputs in 10 healthy male subjects during incremental cycle exercise at sea level (SL) and high altitude (HA, 4559 m). Respiratory power output was calculated from breath-by-breath esophageal pressure and chest wall volume changes. At HA ventilation was increased at any leg power output by ∼ 54%. However, for any given ventilation, breathing pattern was unchanged in terms of tidal volume, respiratory rate and operational volumes of the different chest wall compartments. RPE,resp scaled uniquely with total respiratory power output, irrespectively of SL or HA, while RPE,legs for any leg power output was exacerbated at HA. With increasing respective power outputs, the rate of change of RPE,resp exponentially decreased, while that of RPE,legs increased. We conclude that RPE,resp uniquely relates to respiratory power output, while RPE,legs varies depending on muscle metabolic conditions.

The Use of Nebulized Opioids in the Management of Dyspnea: Evidence Synthesis

PURPOSE/OBJECTIVES

To analyze the evidence about the use of nebulized opioids to treat dyspnea using the Priority Symptom Management (PRISM) level-of-evidence framework and to make a practice recommendation.

DATA SOURCES

Computerized database and manual search for articles and abstracts that included experimental trials, chart reviews, and case studies.

DATA SYNTHESIS

20 articles with evaluable evidence were identified. Analysis was complex because of heterogeneous variables and outcome measures. A major limitation is small sample sizes. The majority of PRISM level I and II studies indicated unfavorable evidence.

CONCLUSIONS

Scientific data supporting the use of nebulized opioids to treat dyspnea in patients with chronic pulmonary disease, including malignancy, are lacking.

IMPLICATIONS FOR NURSING

Insufficient data identify a need for further research with random crossover designs involving larger samples that are stratified according to prior opioid use. Consistency of study variables should be emphasized.

Perception of airway narrowing during reduction of inhaled corticosteroids and asthma exacerbation

BACKGROUND

The perception of airway narrowing is reduced in subjects with severe asthma and may be related to the severity of airway inflammation. A study was undertaken to determine if the perception of airway narrowing changes during the reduction of inhaled corticosteroid (ICS) dose or during an asthma exacerbation.

METHODS

Forty two asthmatic subjects with well controlled asthma had their daily ICS dose halved every 2 months until they were weaned off ICS or they developed an exacerbation. Perception was measured at baseline and at monthly intervals during bronchial challenge with mannitol as the slope and intercept of the regression of the Borg score and percentage fall in forced expiratory volume in 1 second (FEV(1)), and as the Borg score at 20% fall in FEV(1) (PS(20)FEV(1)). Sputum was collected for measurement of inflammatory cell numbers.

RESULTS

In 33 subjects who successfully halved their ICS dose without exacerbation there were significant reductions in slope (p = 0.01), intercept (p = 0.01), and PS(20)FEV(1) (p = 0.003). Sputum eosinophils and airway hyperresponsiveness increased significantly but, in 14 subjects from whom sputum was obtained, changes in eosinophils were not correlated with changes in perception. Change in airway hyperresponsiveness correlated with change in PS(20)FEV(1) (r = -0.40, p = 0.025). In 27 subjects who developed an exacerbation, slope decreased (p = 0.02) and intercept increased (p = 0.01) compared with the visit before the exacerbation. Changes in intercept correlated with changes in resting FEV(1) (r = -0.57, p = 0.002).

CONCLUSIONS

Perception of airway narrowing decreases during ICS dose reduction and decreases further during a mild asthma exacerbation. These changes are related to concurrent changes in airway hyperresponsiveness and resting lung function. The effect of changes in airway inflammation on perception is unclear.

Effect of budesonide on the perception of induced airway narrowing in subjects with asthma

The perception of bronchoconstriction may be modulated by airway inflammation. However, the effect of inhaled corticosteroid (ICS) treatment on perception in subjects with asthma has received limited study. The aim of this study was to determine the effect of inhaled budesonide on the perception of breathlessness induced by histamine challenge. Thirty-five subjects with poorly controlled asthma were randomized to receive budesonide (1,600 or 3,200 microg/d) for 8 wk, followed by 8 wk at 1,600 microg/d and subsequent downtitration according to a clinical algorithm. Borg scores were recorded during histamine challenges performed at baseline and at 8, 16, 24, 48, and 72 wk. Perception was estimated as the slope of Borg/% fall FEV(1). The Borg/FEV(1) slope increased significantly after 8 wk of budesonide (0.09 [0.08-0.12] to 0.15 [0.11-0.19], p = 0.002), and remained increased compared with baseline values at all subsequent visits. There were no significant differences in Borg/ FEV(1) slope between subjects who were and were not taking ICS at study entry. The magnitude of change in the Borg/FEV(1) slope did not differ significantly between treatment groups and was not related to changes in baseline FEV(1), airway hyperresponsiveness, blood eosinophils, or serum eosinophil cationic protein (ECP). We conclude that treatment with budesonide enhances the perception of airway narrowing, but the effect is unrelated to budesonide dose, or to changes in circulating eosinophil markers.

Role of airway receptors in altitude-induced dyspnea

PURPOSE

The purpose of this study was to examine the role of airway receptors in respiratory-related sensations after ascent to altitude.

METHODS

Ratings of respiratory-related sensations, perceived exertion and acute mountain sickness, heart rate, and peripheral oxygen saturation were recorded at rest and exercise in male and female subjects who had inhaled either aerosolized saline or saline with tetracaine after acute ascent to an altitude of 3500 m and after prolonged acclimatization of 18 d at altitudes between 4000 and 5000 m.

RESULTS

Tetracaine had no effect on respiratory-related sensations at altitude either at rest or during exercise, and male and female subjects experienced similar respiratory-related sensations. Sensations of rapid breathing were experienced at rest after acute exposure to 3500 m as compared with sea level, but not after acclimatization to 5000 m. Sensations of rapid breathing, air hunger, and heavy breathing were experienced during exercise after acute and prolonged altitude exposure as compared with sea level, with a sensation of chest tightness experienced at 3500 m and a sensation of gasping experienced at 5000 m.

CONCLUSION

These results suggest that airway afferents play no role in the respiratory-related sensations experienced by male and female subjects either during acute ascent to altitude or after prolonged acclimatization at altitude.

Children's perception of breathlessness in acute asthma

AIM

To determine whether asthmatic children who present to hospital with hypoxia perceive breathlessness less well than non-hypoxic presenters.

METHODS

A total of 27 children aged 5-16 years (mean age 10) admitted with acute asthma had recordings of oxygen saturation (SaO(2)), clinical score, forced expiratory volume in one second (FEV(1)), and breathlessness score (HMP) at admission and at 5, 10, 24, 48, and 72 hours after admission. Those defined as hypoxic (SaO(2) <92%) at admission were compared with a non-hypoxic group.

RESULTS

Twelve children were hypoxic at admission. Compared with the non-hypoxic group they were younger (8.6 (SD 2.8) v 11.2 (2. 8) y, p = 0.02), and had greater airway obstruction (FEV(1) 32.5 (10)% v 54.3 (26)%, p = 0.0073, 95% confidence interval (CI) -36.9 to -6.6) yet had a trend towards less breathlessness (median HMP 4 v 3, p = 0.062, CI -0.001 to 2.00) at admission. The hypoxic group had a smaller change in breathlessness from admission to discharge, despite a similar improvement in FEV(1), reflected in a lower ratio of change in HMP to change in FEV(1) (DeltaHMP/DeltaFEV(1)) (median DeltaHMP/DeltaFEV(1) 0.021%(-1) v 0.073%(-1), p = 0.0081, CI -0.075 to -0.016). Linear regression analysis showed a strong relation between DeltaHMP/DeltaFEV(1) and initial SaO(2) (p = 0.004, r = 0. 54).

CONCLUSIONS

Asthmatic children who present to hospital hypoxic tend to perceive themselves as less breathless than non-hypoxic children. This may predispose to a future life threatening attack.

Exercise training decreases dyspnea and the distress and anxiety associated with it. Monitoring alone may be as effective as coaching

STUDY OBJECTIVE

To determine whether exercise training with coaching is more effective than exercise training alone in reducing dyspnea and the anxiety and distress associated with it and improving exercise performance, self-efficacy for walking, and dyspnea with activities of daily living.

DESIGN

Randomized clinical trial of 51 dyspnea-limited patients with COPD assigned to monitored (n = 27) or coached (n = 24) exercise groups.

SETTING

Outpatient area of university teaching hospital.

INTERVENTION

Both groups completed 12 supervised treadmill training sessions (phase 1) over 4 weeks followed by 8 weeks of home walking (phase 2). The CE group also received coaching during training.

MEASUREMENTS

Perceived work of breathing, dyspnea intensity, distress associated with dyspnea, and anxiety associated with dyspnea were rated on a visual analog scale during incremental treadmill testing and after 6-min walks before and after phase 1. Dyspnea with activities of daily living, self-efficacy for walking, state anxiety, and 6-min walks were measured before and after both phases.

RESULTS

Dyspnea and the associated distress and anxiety improved significantly for both groups relative to work performed and in relation to ventilation (p < 0.05). There were no significant differences between groups in any outcomes. The phase 1 improvement in laboratory dyspnea was accompanied by improvements in dyspnea with activities of daily living (p < 0.01) and self-efficacy for home walking (p < 0.01) that were sustained during the home phase.

CONCLUSIONS

Coaching with exercise training was no more effective than exercise training alone in improving exercise performance, dyspnea, and the anxiety and distress associated with it, dyspnea with activities, and self-efficacy for walking.

[Evaluation of Borg's perceived exertion scale in cardiac rehabilitation]

Borg's perceived exertion scale measures the extent of perceived exertion which a person experiences during exercise. The perceived exertion scale is used to adjust exercise intensity (workload) for predictions and prescriptions of exercise intensities in sports and medical rehabilitation (BORG, 1982). In addition, Borg's scale can be used in the athletic arena, space, industry, military settings, or under everyday circumstances. The concept of perceived exertion is a subjective rating, indicating the subject's opinion about the intensity of the work being performed (MORGAN, 1973). The task of exercising subjects is to assign a number (from 1-20) to represent the subjective sensation of the amount of work being performed. This is a valuable tool in human performance setting, where an important consideration is not "what the individual is doing, but what he thinks and is doing" (MORGAN, 1973).

Do voluntary changes in inspiratory-expiratory ratio prevent exercise-induced asthma?

It is often admitted that heat exchange in the airways is a major cause of exercise-induced asthma. Because a decrease in the inspiratory time/expiratory time ratio (TI/TE) decreases these exchanges, we postulated that it might decrease bronchoconstriction as well. Twenty-four asthmatic children, divided into three groups, underwent two exercise provocation tests, 24 hours apart (outdoor running for 6 min). The first test was identical for all the subjects. In the second test, the first group did not receive any instruction concerning breathing pattern. The second group was instructed to adopt equal inspiratory and expiratory times (TI/TE = 1). The third group had to adopt an expiratory time three times longer than inspiratory time (TI/TE = 1/3). The three groups displayed similar pulmonary function tests (FEV1 and FVC), cardiac frequency, and running performances. However, FEV1 significantly improved in the second session. This suggested that familiarization with the task and related psychological factors may influence asthma more than voluntary changes in TI/TE.