In this study, the hypercapnic ventilatory response (HCVR) was measured, defined as the ventilation response to carbon dioxide tension (PCO2). We investigated which method, rebreathing or steady-state, is most suitable for measurement of the HCVR in healthy subjects, primarily based on reproducibility. Secondary outcome parameters were subject experience and duration.20 healthy adults performed a rebreathing and steady-state HCVR measurement on two separate days. Subject experience was assessed using numeric rating scales (NRS). The intraclass correlation coefficient (ICCs) of the sensitivity to carbon dioxide above the ventilatory recruitment threshold and the projected apnoea threshold were calculated to determine the reproducibility of both methods.The ICCs of sensitivity were 0.89 (rebreathing) and 0.56 (steady-state). The ICCs of the projected apnoea threshold were 0.84 (rebreathing) and 0.25 (steady-state). The steady-state measurement was preferred by 16 out of 20 subjects; the differences in NRS scores were small.The hypercapnic ventilatory response measured using the rebreathing setup provided reproducible results, while the steady-state method did not. This may be explained by high variability in end-tidal PCO2. Differences in subject experience between the methods are small.
Background The Hexoskin is a smart shirt that can take continuous and objective measurements and could be part of a potential telemonitoring system. Objective The aim of this study was to determine the accuracy of the calibrated Hexoskin in measuring tidal volumes (TVs) in comparison to spirometry during various tasks. Methods In a cross-sectional study, the TV of 15 healthy subjects was measured while performing seven tasks using spirometry and the Hexoskin. These tasks were performed during two sessions; between sessions, all equipment was removed. A one-time spirometer-based calibration per task was determined in session 1 and applied to the corresponding task in both sessions. Bland-Altman analysis was used to determine the agreement between TV that was measured with the Hexoskin and that measured with spirometry. A priori, we determined that the bias had to be less than ±5%, with limits of agreement (LOA) of less than ±15%. Lung volumes were measured and had to have LOA of less than ±0.150 L. Results In the first session, all tasks had a median bias within the criteria (±0.6%). In the second session, biases were ±8.9%; only two tasks met the criteria. In both sessions, LOA were within the criteria in six out of seven tasks (±14.7%). LOA of lung volumes were greater than 0.150 L. Conclusions The Hexoskin was able to correctly measure TV in healthy subjects during various tasks. However, after reapplication of the equipment, calibration factors were not able to be reused to obtain results within the determined boundaries. Trial Registration Netherlands Trial Register NL6934; https://www.trialregister.nl/trial/6934
Home monitoring of patients with chronic obstructive pulmonary disease can increase quality of life and decrease health care costs. Despite the existence of an important relationship between lung hyperinflation (LH) and patient outcomes, LH is often ignored in home monitoring as it difficult to assess at home. A smart shirt containing respiratory inductance plethysmography (RIP, which measures thoracic and abdominal cross-sectional area changes) is a promising tool for home monitoring of LH. This study investigates the feasibility of a smart shirt to monitor LH. We aimed to describe the relationship between temperature and the output, and between the circumference and output of the smart shirt and to correct for temperature dependency. To do so, the smart shirt was applied to a custom-made torso model. Ambient temperature was increased and decreased in 15 tests, while maintaining a constant torso circumference to derive a temperature correction. Additionally, sensor output was monitored with varying circumference. The results revealed a linear relation between temperature and RIP output. Nine of the twelve shirts showed a linear output to changes in circumference. A median temperature drift of −34.7 mL/ • C was observed and corrected to a minimum drift of −0.5 mL/ • C. In conclusion, RIP is a promising method for measuring LH in home monitoring. Patients will not be falsely diagnosed with LH due to temperature changes.Sensor output can easily be corrected for temperature. Furthermore, the relationship between circumference and output is linear, confirming the ease of implementing the calibration procedure for obtaining lung volumes.
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