A Predictive Score to Reduce the Use of Hypoxic-altitude Simulation Test (HAST) in Patients With Chronic Respiratory Disease Planning Air Travel - an External Validation Prospective Study
Trial Snapshot
- Phase
- Not Applicable
- Status
- Completed
- Sponsor
- Enrollment
- 96
- Locations
- 1
- Primary Endpoint
- ROC AUC for Model 1 (3*SaO2 - HCO3 - 4 if ILD - 4 if F -3 if COPD), and the relative sensitivity, specificity, positive and negative predictive value of the threshold identified for negative and positive HAST
Study Overview
Brief Summary
Patients with chronic lung diseases travelling by plane often suffer with symptoms related to lower oxygen levels they are exposed to while flying.
Therefore, patients with respiratory conditions are routinely assessed to establish if they need supplemental oxygen in flight. A hypoxic altitude simulation test (HAST) is often part of this assessment and consists in having patients breathe a oxygen/nitrogen blend with a lower oxygen concentration compared to normal room air, simulating in-flight conditions. Oxygen levels are measured before and after the test through a blood sample (from the earlobe or an artery in the wrist) and with a finger probe. In-flight oxygen is required if the oxygen level in the blood is lower than 6.6 kPa. HASTs are time consuming, costly, and require a dedicated hospital appointment.
Using historical data, the Investigators developed scores based on capillary blood gas (blood sample from the earlobe), diagnosis and sex to predict the outcome of the HASTs. The Investigators validated the proposed scores in a separate historic cohort of patients and showed it had good concordance with the HASTs results.
In this study, the Investigators want to confirm prospectively if the score, based on blood results (venous and/or earlobe), can predict the outcome of the HASTs and therefore reduce the number of tests performed, travel time for patients, and costs for the NHS.
All patients, aged 18 or older, who are having a HAST for clinical purposes at the cardio-respiratory lab at Leeds Teaching Hospital NHS Trust will be invited to take part in the study. The Investigators will record diagnosis, results of HAST and previous spirometry from the medical notes, perform a spirometry if not done in the previous 12 months and collect a blood sample (one tube, 4 mls). With these data, the Investigators will calculate the score and assess its agreement with the outcome of the HAST.
Each participant's involvement in the study will last for approximately 90-120 minutes, which is the normal duration of a HAST.
The Investigators aim to include up to 280 subjects in the study.
Detailed Description
Over the last two decades, there has been a significant increase in the number of people flying on a regular basis. As a result, more individuals with chronic respiratory disease are being referred for formal assessment to assess if they require inflight oxygen.
At cruising altitude, passengers are exposed to reduced atmospheric pressure equivalent to an altitude of 8000 ft, corresponding to a reduction of oxygen from 21% to approximately 15%. National and International recommendations on air travel suggest screening patients with chronic lung diseases for the need of in-flight oxygen supplementation. However, due to the paucity of available evidence, there is no consensus on which investigation should be performed and the precise risk factors associated with in-flight complications.
The British Thoracic Society, which published the most recent and comprehensive recommendations on this topic, recommends that patients with respiratory diseases should be assessed clinically, and in specific situations, a hypoxic altitude simulation tests (HAST) should be performed. Unfortunately, the vast majority of these recommendations are level C at best, as current evidence is limited to a handful of prospective or retrospective analyses.
A standard hypoxic altitude simulation test requires the patients to breathe a blend of 15% oxygen in nitrogen for 20 minutes. This simulates the oxygen tension at 8000 ft, the equivalent cabin pressure. Blood gas measurements are taken before and after the test. A fall in the pO2 below 6.6 kPa is considered indicative for use of in-flight oxygen.
Often the HASTs yield negative results (i.e. no inflight oxygen required). These tests are heavy on resources, time consuming, costly, not widely available and require dedicate hospital appointment. Thus, predictors of outcomes of HASTs are needed to reduce the number of HASTs performed.
Study Design
- Study Type
- Observational
- Observational Model
- Case Only
- Time Perspective
- Cross Sectional
Eligibility Criteria
- Ages
- 18 Years to — (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- No
Inclusion Criteria
- •Age ≥18 years old (at the time of HAST)
- •Clinically stable
- •Hypoxic altitude simulation test, scheduled as part of the clinical care
Exclusion Criteria
- •Inability to provide informed consent
- •Being part of a clinical trial, which would exclude patients who are taking part in other studies including observational studies.
Outcomes
Primary Outcomes
ROC AUC for Model 1 (3*SaO2 - HCO3 - 4 if ILD - 4 if F -3 if COPD), and the relative sensitivity, specificity, positive and negative predictive value of the threshold identified for negative and positive HAST
Time Frame: Up to 36 months
The score based on Model 1 will be computed for all subjects and ROC curve analyses will be used to assess predictive value. Sensitivity, specificity, PPV and NPV for criteria previously identified in a historic cohort will be assessed.
Secondary Outcomes
- ROC AUC for the simplified score (3*SpO2 - sHCO3 - 4 if ILD - 4 if F - 3 if COPD)(Up to 36 months)
- ROC AUC for Model 2, and Model 3 and for baseline pO2 and relative sensitivity, specificity, positive and negative predictive value of the previously identified thresholds.(Up to 36 months)