Patients with Chronic Obstructive Pulmonary Disease Can Accurately Perform Home-Based Measurements of Inspiratory Capacity and Dynamic Hyperinflation.

Home-based lung function measurements can be used to capture day-to-day variations in symptoms in patients with chronic obstructive pulmonary disease (COPD). Although dynamic hyperinflation (DH) is clinically relevant, existing home-based measurements do not include its assessment. DH can be measured through inspiratory capacity (IC) measurements before and after metronome-paced tachypnea test (MPT). The goal of this study is to determine the accuracy of unsupervised home-based IC and DH measurements in COPD.Sixteen COPD patients performed IC and DH measurements during 4 home visits. Visit 1 was considered a training session. During all visits supervised and unsupervised IC at rest (ICREST) and after MPT (ICMPT) were measured. DH was calculated as the difference between ICREST and ICMPT, and as a percentage of ICREST. Bland-Altman analyses and ANOVA tests were performed to determine the effect of supervision and repeated measures over time.The biases between supervised and unsupervised ICREST, ICMPT, ΔIC and ΔIC% were 0.007 L, 0.007 L, 0 mL and -0.09% in the last visit, respectively. Limits of agreement of ICREST and ΔIC% decreased from ±0.261 mL to ±0.201 mL, and from ±13.84% to ±10.81% between visit 1 and 4, respectively. No significant effect of supervision or over time was found.After a robust training and a learning phase, COPD patients are able to perform IC measurements in an accurate manner in both rest and after MPT. This yield accurate assessment of DH, in an unsupervised home-based setting.

Is the Metronome-Paced Tachypnea Test (MPT) Ready for Clinical Use? Accuracy of the MPT in a Prospective and Clinical Study.

BACKGROUND: A simple technique to measure dynamic hyperinflation (DH) in patients with chronic obstructive pulmonary disease (COPD) is the metronome-paced tachypnea test (MPT). Earlier studies show conflicting results about the accuracy of the MPT compared to cardiopulmonary exercise testing (CPET). OBJECTIVES: The focus was to investigate the diagnostic accuracy of MPT to detect DH in a prospective and clinical study. METHODS: COPD patients were included; all underwent spirometry, CPET, and MPT. DH (ΔIC) was calculated as the difference in % between inspiratory capacity (IC) at the start and end of the test divided by IC at the start. A subject was identified as a hyperinflator, if ΔIC (% of ICrest) was smaller than -10.2 and -11.1% in CPET and MPT, respectively. With these values, sensitivity and specificity were calculated. Bland-Altman plots were made of ΔIC (% of ICrest). RESULTS: In the prospective and clinical study, 107 and 48 patients were included, respectively. Sensitivity of the MPT was 85% in both studies. The specificities were 33 and 27%, respectively. In the prospective study, B = +2.6%, L = 30.6, and -25.6%. In the clinical study, B = +0.8%, L = 31.0, and -29.1%. CONCLUSION: MPT seems to be a good replacement for CPET in group studies. The mean amount of DH was not different between CPET and MPT. On an individual level, MPT cannot be used to identify hyperinflators; it should be kept in mind that MPT overdiagnoses DH. The amount of DH should not be interchanged between CPET and MPT.

The Accuracy of Tidal Volume Measured With a Smart Shirt During Tasks of Daily Living in Healthy Subjects: Cross-sectional Study.

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.

Telemonitoring Techniques for Lung Volume Measurement: Accuracy, Artifacts and Effort.

Telemonitoring becomes more important in pulmonary research. It can be used to decrease the pressure on the health care system, to lower the costs of health care and to increase quality of life of patients. Previous studies show contradictory results regarding the effectiveness of telemonitoring. According to multiple researchers, inefficiency can be a result of poor study design, low data quality and usability issues. To counteract these issues, this review proves for an in-depth explanation of four (potential) telemonitoring systems in terms of work principle, accuracy, disturbing factors and usability. The evaluated systems are portable spirometry/breath-by-breath analyzers, respiratory inductance and magnetic plethysmography and electrical impedance tomography. These insights can be used to select the optimal technique for a specific purpose in future studies.

Reproducibility of hypercapnic ventilatory response measurements with steady-state and rebreathing methods.

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.