Remote monitoring of spirometry and oximetry in patients with connective tissue disease related interstitial lung disease: a prospective observational cohort study

Background: Remote monitoring of forced vital capacity (FVC) and oximetry (Spo2) in patients with idiopathic pulmonary fibrosis (IPF) is emerging as an adjunct to routine in-person ambulatory care. Patients with connective tissue diseases (CTD) commonly have impaired hand function, diminished oral aperture and Raynaud's phenomenon, which can uniquely impair the user’s ability to use these devices. We aimed to assess the acceptability, usability and adherence to home monitoring in patients with CTD associated interstitial lung disease (CTD-ILD) compared to patients with IPF. Methods: Patients were recruited to a prospective observational cohort study (NCT06702228), provided with a portable handheld spirometer and finger pulse oximeter connected to a smart phone application (app), received training in their use, asked to use these at least once a week, and were reviewed at 6-months. Results: 97 patients completed the 6-month study. Patients in the CTD-ILD group were slightly younger than those with IPF with a mean and standard deviation (SD) of 62.44 (15.25) compared to 70.21 (9.39) years (p = 0.005). The number of days the devices were used was lower in the CTD-ILD (69.2 versus 99.4, p = 0.028), however, in line with study instructions, there was no significant difference in weekly adherence with FVC or SpO2 measurement (71.5% versus 75%, p = 0.65). We found a strong correlation between home and hospital-based FVC (r = 0.76, p < 0.0001). Both groups reported finding the devices and app easy to use (77% versus 72%, p = 0.65), but more patients with CTD-ILD reported difficulty obtaining SpO2 readings compared to patients with IPF (33.33% versus 12.77%, p = 0.02). Six (16.7%) patients from the CTD-ILD group experienced difficulty using the devices due to hand function impairment (p = 0.004), 3 (8.3%) were unable to use a finger probe at all and required an ear oximeter. We found no differences in the correlation of FVC adherence with age, ILD-GAP score, or patient reported symptom scores between the groups. Conclusions: While patients with CTD-ILD had lower device use than those with IPF, they did have high adherence, satisfaction and reported ease of use despite Raynaud's phenomenon and impaired hand function. Therefore, remote monitoring has potential as an adjunct to routine care in CTD-ILD.