Energy expenditure at rest and during walking in patients with chronic respiratory failure: a prospective two-phase case-control study

Accompanied versus unaccompanied walking for continuous oxygen saturation measurement during 6-min walk test in COPD: a randomised crossover study

The aim of this study was to determine if there is a difference in 6-min walk test (6MWT) distance when the assessor accompanies the patient to continuously measure peripheral oxygen saturation (S_pO2) compared to the patient walking unaccompanied.

 We conducted a randomised crossover study to evaluate the impact of the assessor walking with the patient during the 6MWT (6MWT_with) versus the patient walking alone (6MWT_without). At the end of a pulmonary rehabilitation programme, each patient performed two 6MWTs in random order and separated by a 30-min rest.

 49 patients with chronic obstructive pulmonary disease (COPD) (Global Initiative for Obstructive Lung Disease classification II–IV) were included. In a regression model adjusting for period and subject, accompanying the patient resulted in a lower walking distance (mean difference −9.1 m, 95% CI −13.9– −4.3, p=0.0004). Notably, six patients walked more than 30 m farther (minimal important difference) in one of the two conditions (6MWT_with: n=1, 6MWT_without: n=5). There were no between-sequence-group differences in heart rate, dyspnoea, leg fatigue and S_pO2. The median (interquartile range) number and duration of S_pO2 signal artefacts were high but not different between the experimental conditions (6MWT_with: 17 (4–24), 34 s (7–113 s); 6 MWT_without: 11 (3–26), 24 s (4–62 s)).

 At a study population level, we observed a statistically significant difference in 6MWT distance between the two experimental conditions; however, the magnitude of difference was small and may not be clinically relevant. Nevertheless, in a clinical setting, unaccompanied walking resulted in a substantially higher walking distance in individual patients, pointing towards strictly standardised testing methodology, in particular in pre–post study designs.

Accompanied walking during a 6MWT versus unaccompanied walking results in shorter walked distance (mean difference −9.1 m, 95% CI −13.9– −4.3 m). No differences in nadir S_pO2 or oximetry artefacts were noted between accompanied and unaccompanied walking.https://bit.ly/3tBjfCq

The impact of carrying supplemental oxygen on exercise capacity and dyspnea in patients with interstitial lung disease

BACKGROUND

May patients with interstitial lung disease (ILD) require supplementary oxygen (O₂) therapy to maintain normoxia. However, ambulatory O₂ delivery devices are constraining and cumbersome. The physiologic and symptomatic impact of these devices on ILD patients is unknown.

METHODS

We conducted a prospective study of 30 clinically stable ILD patients (with varying disease severity), half of whom used O₂ at baseline. Each subject completed two six-minute walk tests (6MWTs); for O₂ users, one walk was completed while wearing a backpack (weight 7.2 pounds) containing a tank with compressed O₂, and for non-users, one walk was completed with a similarly-weighted backpack. For each subject, during the second walk, no backpack was worn; for the second walk, O₂ users received oxygen via a stationary delivery system. For both walks, O₂ non-users wore a portable metabolic system, which measured variables related to respiratory physiology and gas exchange. Borg dyspnea and exertion ratings were recorded after each walk.

RESULTS

Wearing the O₂-containing backpack resulted in decreased distance covered during the 6MWT, and increased dyspnea and perceived exertion among O₂ users. While wearing the weighted backpack, O₂ non-users had a significantly lower peripheral O₂ saturation and distance-saturation product. Compared with carrying O₂ in the backpack, receiving O₂ via the stationary concentrator resulted in the largest improvement in walk distance for the three subjects with greatest impairment at baseline (6MWT ≤ 300 m).

CONCLUSION

Among ILD patients, carrying portable O₂ versus receiving O₂ via a stationary concentrator results in significantly greater dyspnea and shorter distances covered in timed testing. Patients with the greatest impairment may be affected most. When prescribing O₂, practitioners should alert patients to this effect and help patients decide on the best O₂ delivery mode to meet their needs.

How to carry out a field walking test in chronic respiratory disease

EDUCATIONAL AIMS

To provide recommendations for conducting field walking tests in people with chronic respiratory disease, from the new European Respiratory Society/American Thoracic Society Technical StandardTo provide information to assist in selecting a field walking test in people with chronic respiratory disease.

KEY POINTS

The 6MWT, ISWT and ESWT are valid and reliable tests of functional exercise capacity in people with COPD. The 6MWT is also widely used in other chronic respiratory disorders.There is a learning effect for the 6MWT and ISWT, so two tests must be performed if the tests are being used to measure change over time, with the best distance recorded.The 6MWT is very sensitive to changes in the way it is conducted, including use of encouragement, provision of supplemental oxygen, changes in track layout and length, and use of wheeled walkers. These factors should be held constant when the test is repeated.The 6MWT, ISWT and ESWT are strenuous tests, with cardiorespiratory responses that are similar to those during a maximal incremental exercise test. As a result, the contraindications and precautions for these field walking tests should be the same as for a laboratory-based incremental exercise test.

SUMMARY

The European Respiratory Society (ERS) and American Thoracic Society (ATS) have recently published a Technical Standard which documents the standard operating procedures for the 6-min walk test (6MWT), incremental shuttle walk test (ISWT) and endurance shuttle walk test (ESWT). The Technical Standard shows that all three tests are valid and reliable measures of functional exercise capacity in people with chronic respiratory disease and makes recommendations for standardising their performance. Key findings and recommendations of the Technical Standard include: The 6MWT, ISWT and ESWT are strenuous tests which elicit cardiorespiratory responses that are similar to those observed during a maximal incremental exercise test. As a result, the contraindications and precautions for field walking tests should be consistent with those used for a laboratory-based incremental exercise test.There is strong evidence of a learning effect for the 6MWT and ISWT. Two tests should be performed when the 6MWT or ISWT are used to measure change over time.The 6MWT, ISWT and ESWT are responsive to treatment effects in people with chronic respiratory disease, particularly for rehabilitation.The 6MWT is very sensitive to variations in methodology, including use of encouragement, provision of supplemental oxygen, changes in track layout and length, and use of wheeled walkers. These factors should be documented and held constant on repeat testing.The lowest S pO2 recorded during a 6MWT is an important marker of disease severity and prognosis. Continuous pulse oximetry is recommended during the 6MWT, to ensure that the lowest S pO2 is recorded.In adults with chronic respiratory disease, a change in 6-min walk distance of 30 m or more indicates a clinically significant change has occurred.

An official European Respiratory Society/American Thoracic Society technical standard: field walking tests in chronic respiratory disease

Field walking tests are commonly employed to evaluate exercise capacity, assess prognosis and evaluate treatment response in chronic respiratory diseases. In recent years, there has been a wealth of new literature pertinent to the conduct of the 6-min walk test (6MWT), and a growing evidence base describing the incremental and endurance shuttle walk tests (ISWT and ESWT, respectively). The aim of this document is to describe the standard operating procedures for the 6MWT, ISWT and ESWT, which can be consistently employed by clinicians and researchers. The Technical Standard was developed by a multidisciplinary and international group of clinicians and researchers with expertise in the application of field walking tests. The procedures are underpinned by a concurrent systematic review of literature relevant to measurement properties and test conduct in adults with chronic respiratory disease. Current data confirm that the 6MWT, ISWT and ESWT are valid, reliable and responsive to change with some interventions. However, results are sensitive to small changes in methodology. It is important that two tests are conducted for the 6MWT and ISWT. This Technical Standard for field walking tests reflects current evidence regarding procedures that should be used to achieve robust results.

An official systematic review of the European Respiratory Society/American Thoracic Society: measurement properties of field walking tests in chronic respiratory disease

This systematic review examined the measurement properties of the 6-min walk test (6MWT), incremental shuttle walk test (ISWT) and endurance shuttle walk test (ESWT) in adults with chronic respiratory disease.

Studies that report the evaluation or use of the 6MWT, ISWT or ESWT were included. We searched electronic databases for studies published between January 2000 and September 2013.

The 6-min walking distance (6MWD) is a reliable measure (intra-class correlation coefficients ranged from 0.82 to 0.99 in seven studies). There is a learning effect, with greater distance walked on the second test (pooled mean improvement of 26 m in 13 studies). Reliability was similar for ISWT and ESWT, with a learning effect also evident for ISWT (pooled mean improvement of 20 m in six studies). The 6MWD correlates more strongly with peak work capacity (r=0.59–0.93) and physical activity (r=0.40–0.85) than with respiratory function (r=0.10–0.59). Methodological factors affecting 6MWD include track length, encouragement, supplemental oxygen and walking aids. Supplemental oxygen also affects ISWT and ESWT performance. Responsiveness was moderate to high for all tests, with greater responsiveness to interventions that included exercise training.

The findings of this review demonstrate that the 6MWT, ISWT and ESWT are robust tests of functional exercise capacity in adults with chronic respiratory disease.

Impact of treatment with continuous positive airway pressure (CPAP) on weight in obstructive sleep apnea

STUDY OBJECTIVE

To determine the impact of continuous positive airway pressure (CPAP) on weight change in persons with obstructive sleep apnea (OSA).

DESIGN SETTING AND PARTICIPANTS

The Apnea Positive Pressure Long-term Efficacy Study (APPLES) was a 6-month, randomized, double-blinded sham-controlled multicenter clinical trial conducted at 5 sites in the United States. Of 1,105 participants with an apnea hypopnea index ≥ 10 events/ hour initially randomized, 812 had body weight measured at baseline and after 6 months of study.

INTERVENTION

CPAP or Sham CPAP.

MEASUREMENTS

Body weight, height, hours of CPAP or Sham CPAP use, Epworth Sleepiness Scale score.

RESULTS

Participants randomized to CPAP gained 0.35 ± 5.01 kg, whereas those on Sham CPAP lost 0.70 ± 4.03 kg (mean ± SD, p = 0.001). Amount of weight gain with CPAP was related to hours of device adherence, with each hour per night of use predicting a 0.42 kg increase in weight. This association was not noted in the Sham CPAP group. CPAP participants who used their device ≥ 4 h per night on ≥ 70% of nights gained the most weight over 6 months in comparison to non-adherent CPAP participants (1.0 ± 5.3 vs. -0.3 ± 5.0 kg, p = 0.014).

CONCLUSIONS

OSA patients using CPAP may gain a modest amount of weight with the greatest weight gain found in those most compliant with CPAP.

COMMENTARY

A commentary on this article appears in this issue on page 995.

CITATION

Quan SF; Budhiraja R; Clarke DP; Goodwin JL; Gottlieb DJ; Nichols DA; Simon RD; Smith TW; Walsh JK; Kushida CA. Impact of treatment with continuous positive airway pressure (CPAP) on weight in obstructive sleep apnea.