The study was a quality assurance project with prospectively collected data on the implementation of and results of a sit-stand test on patients with suspected COVID-19 receiving an ambulance in the Central Denmark Region during the intial pandemic wave (from 6th April 2020 to 6th July 2020). According to Danish ethical and legal regulations, informed consent from the patients was not required for data-collection for this quality assurance project (this waiver was approved by the Central Denmark Region Committees on Health Research Ethics).
Setting and implementation
Central Denmark Region covers an area of 13,053 km2 and 1.3 million inhabitants corresponding to 23% of the Danish population [14]. Patients were triaged for ambulance transport either by GP via telephone interview, visit in GP clinic or GP home visit or following a citizen call to the emergency 1–1-2 number where medical personnel at the emergency medical communication center (EMCC) undertook criteria-based triage [15].
According to guidelines implemented before the COVID-19 pandemic, patients who had been triaged for ambulance transport after physical examination by a GP were not to be treated and released on-scene by ambulance personnel, whereas patients triaged after a telephone consultation only (GP or 1–1-2 call) could be treated and released after consultation with a physician [16].
During the initial pandemic wave, when GP’s were prevented from physically examining suspected COVID-19 patients due to lack of personal protective equipment, a new guideline for prehospital management of telephone triaged patients was implemented. According to this guideline, patients with known risk factors for progression to serious disease (i.e. age > 70, significant comorbidities and/or unstable vital parameters) were to be taken to hospital for further evaluation [17]. In stable patients < 70 years of age with no risk factors for serious disease, the one-minute sit-stand test was implemented as precautionary security measure before considering treating and releasing the patient on-scene (English translation of decision-support flow-chart in Fig. 1). Implementation of this new guideline was conducted according to organizational routines, as a written guideline distributed throughout the organisation. The guideline was supplemented by an instructional video describing which patients should be tested and how to perform the one-minute sit-stand test. Patients could at any time deny participation in exercise test.
Exercise testing and clinical decision-making
The one-minute sit-stand test was conducted by the ambulance personnel on-scene according to Fig. 1. Prior to the test, all patients had to have two sets of normal resting vital signs (pulse, respiration rate, blood pressure and oxygen saturation) measured within a five-minute interval. The one-minute sit-stand test began with placing the patient on a chair without armrest, with the legs in a 90-degree bend. The patient was asked to sit and stand as many times as possible during one minute without supporting with the arms. The oxygen saturation was monitored by pulse oximetry during the test and continuously one minute after completion of the test. The one-minute sit-stand test was considered to indicate decompensation (i.e. positive test) if the oxygen saturation decreased > 3 percentage points and/or if the patient could not perform more than 12 sit-stand repetitions in one minute. The test was terminated and also considered positive if saturation fell below < 90% or if the patient was unable to continue the test [10, 18, 19].
Following completion of the sit-stand test, ambulance personnel telemedically consulted with a physician for patient triage. The decision on whether to admit the patient to hospital or not was made by the physician.
Data collection
We collected data for this quality assurance project on all patients with suspected COVID-19 triaged to an ambulance response by a GP in the Central Denmark Region during the study period. Patients were identified through the electronic prehospital patient record (PPJ). Patient related data (age, gender, COVID-symptoms, comorbidities, vital parameters, prehospital and hospital treatment, COVID-19 status and final diagnosis) were collected by the primary investigator from PPJ and from electronic in-hospital patient records. For patients tested with the sit-stand test, the result of the test was entered into PPJ by ambulance personnel on-scene. Study data were collected and managed by the primary investigator using REDCap electronic data capture tools (REDCap, 10.0.10, Vanderbilt University).
Outcome measurements
The primary outcome for this study was the proportion of patients treated with oxygen within 7 days among patients decompensating vs patients not decompensating during the test. Secondary outcomes were 1) the proportion of patients admitted to intensive care unit within 7 days in patients decompensating during the one-minute sit-stand test vs patients not decompensating, 2) the proportion of patients sit-stand tested before being treated and released on-scene and 3) the proportion of patients treated and released on-scene who were subsequently admitted to hospital, treated with supplementary oxygen, and/or were admitted to an intensive care unit.
Statistical analysis
We lacked key knowledge on the patient group, size of the group, number of patients decompensating and number of these who would need oxygen supplement. Thereby, the study was exploratory and sample size calculation was not performed. Patients were included during the ongoing pandemic and duration of the study depended on the duration of the initial pandemic wave.
Binary data were analyzed by Chi2-tests and continuous data were examined for normal distribution and analyzed with students t-test. The level of significance was set at 0.05. Analyzes were performed using Stata 15 (StataCorp LCC, College Station, TX, USA).