Pulse oximetry oxygen saturation during the 6-min walk test: a limit for stopping the test without resuming it

Limitations of the dichotomized 6-minute walk distance when computing lung allocation score for cystic fibrosis: a 16-year retrospective cohort study

PURPOSE

The 2010 Lung Allocation Score (LAS) version considers the estimated survival benefit offered by lung transplantation (LTx) and uses 6-minute Walk Test (6MWT) distance as a dichotomous covariate of whether an individual can walk more than 150 ft or 45.7 m in 6 min. This study aimed to provide evidence that 6MWT gives no clinically meaningful information to be used in the current LAS for candidates to LTx with cystic fibrosis (CF).

MATERIALS AND METHODS

We collected data from 6MWTs performed since 2003 at our CF centre. A joint model was fitted to describe the effect of changes in walked distance on the hazard of LTx or death.

RESULTS

Up to 2019, 552 6MWTs were performed on 163 individuals with CF. None of the individuals included walked for less than 45.7 m during the 6MWT. Based on the joint modelling, the association of walked distance with the hazard ratio (HR) of LTx or death was significant (HR 0.99, 95% Credible Interval [CI]: 0.99 to 1.00).

CONCLUSIONS

When adopted dichotomously for LAS calculation, walked distance does not add any useful information about exercise capacity. Longitudinal trajectories of walked distance may provide complementary information about prognosis in individuals with CF.Implications for rehabilitationDichotomized walked distance does not contribute to lung allocation score in candidates to lung transplantation with cystic fibrosisChanges in the longitudinal trajectory of walked distance can be clinically meaningful for prognostication.Sensitive outcomes to be incorporated in the lung allocation scoring system for individuals with CF are yet needed to catch rapid falls in functional capacity.

Should the 6-Minute Walk Test Be Stopped If Oxyhemoglobin Saturation Falls Below 80%?

OBJECTIVE

To examine the occurrence of adverse events in patients undergoing assessment for pulmonary rehabilitation when a 6-minute walk test (6MWT) continues despite desaturation below 80%.

DESIGN

Retrospective audit following REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) Statement.

SETTING

Large teaching hospital.

PARTICIPANTS

All patients (N=549) (55% men, mean age 69±11y) assessed for pulmonary rehabilitation (September 2005 to January 2016).

INTERVENTIONS

The standardized tests were conducted by experienced cardiorespiratory physiotherapists. Oxyhemoglobin saturation was monitored continuously using a pulse oximeter (lowest value used for analysis). Medical records were reviewed, and adverse events defined as tachycardia, bradycardia, chest pain, or other sign/symptom necessitating cessation.

MAIN OUTCOME MEASURE

6MWT.

RESULTS

Data from 672 walk tests were included with mean distance 369 (124) meters. The main diagnoses were chronic obstructive pulmonary disease (70%), interstitial lung disease (14%), and bronchiectasis (8%). Sixty individuals (11%) recorded desaturation below 80% without adverse events. Two adverse events were recorded during tests without desaturation; in 1 instance, chest pain with no evidence of cardiorespiratory compromise and in another, the patient stopped due to concern regarding blood sugar levels (11.5 mmol/L when tested). Independent predictors of desaturation to less than 80% were resting oxyhemoglobin saturation <95% (odds ratio [OR] 3.82, 95% confidence interval [CI] 2.06-7.08) and a diagnosis of interstitial lung disease or pulmonary arterial hypertension (OR 5.24, 95% CI 2.59-10.58).

CONCLUSIONS

This study found that desaturation to less than 80% during a 6MWT was not associated with adverse events in a large cohort of patients referred to pulmonary rehabilitation and assessed by experienced physiotherapists, suggesting that test cessation due to desaturation in stable patients may be unwarranted.