Home monitoring of breathing rate in people with chronic obstructive pulmonary disease: observational study of feasibility, acceptability, and change after exacerbation

Figures & data

Table 1 Monitors’ technical characteristics

Monitor	Output	Size	Position	Technology
Monitor 1: Impedance	ECG, HR, BR, and PAL	7.5×5.0×2.0 cm, weight 60 g	Attached to the chest and upper abdomen	Electrode array (impedance)
Monitor 2: PPG	BR	56×36×62 mm, weight 54 g	Worn on the wrist with a finger probe	PPG
Monitor 3: Camera	BR and HR	N/A	Participant was videoed while in sitting position	Distance PPG algorithm
Monitor 4: Accel	BR and PAL	4.5×3.5×1.3 cm, weight 18 g	Attached to the upper abdomen just below the ribs and taped to the skin	Accelerometer
Monitor 5: Chest-band	HR, R-R Interval, BR, ECG, posture, PAL • Posture • Activity level • Peak Accel	2.8×0.7 cm, weight 89 g (including the chest strap)	Chest strap and an electronics module that attaches to the strap	Pressure sensor pad and accelerometer

Abbreviations: BR, breathing rate; ECG, electrocardiogram; HR, heart rate; PAL, physical activity level; PPG, photoplethysmography; N/A, not applicable; R-R, distance between 2 R peaks on ECG; Accel, accelerometer.

Table 2 Protocol followed to assess BR variations during the phase 1 of the study

Type of activity	Time (min)
Lying	4
Sitting	2
Standing	1
Slow 6MWT	6
Sitting	3
Fast 6MWT	6
Sitting	5
Sweeping	4
Sitting	2
Lifting objects	3
Sitting	2
Standing and walking	1
Climbing stairs	1
Sitting	5
Standing and walking	1
Treadmill (flat walking)	4
Treadmill (4% slope)	4
Standing and walking	1
Sitting	2

Abbreviations: BR, breathing rate; 6MWT, 6 minutes walking test.

Table 3 Patients characteristics

	COPD patients phase I	COPD patients phase II	COPD patients phase III
n	21	23	18
Men (%)	13 (62)	13 (65)	9 (69)
Age (years)	68.7, SD 7.9	68.8, SD 7.6	71.5, SD 10.4
Height (cm)	166.3, SD 8.4	165.4, SD 11.9	165.5, SD 9.9
Weight (kg)	71.1, SD 17	76.2, SD 22.1	75.5, SD 15.8
BMI (kg/m^2)	25.6, SD 5.7	28.6, SD 9.5	27.5, SD 5.1
Pack/year	37.0, SD 18.0	46.5, SD 19.6	53, SD 20.7
mMRC		1.15, SD 1	3.3, SD 0.7
FEV1 (L)	1.4, SD 0.5	1.24, SD 0.5	1.2, SD 0.5
FEV1 (% pred)	47 (59%)	42 (53%)	42 (53%)
FVC (L)	3.0, SD 1.0	2.6, SD 0.7	2.7, SD 1.1
FVC (% pred)	81 (101%)	71 (88%)	75 (94%)
FEV1/FVC	0.5, SD 0.47	0.48, SD 0.45	0.44, SD 0.45
SpO2 (%)		92.0, SD 3.7	91.1, SD 4.6
6MWD (m)	432.8, SD 124.7
QMVC (kg)	31.6, SD 9.2
PAL (steps)	4,368, SD 2,270

Abbreviations: 6MWD, 6 minutes walking distance; BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in the first second; % pred, percent of predicted; FVC, forced vital capacity; mMRC, modified Medical Research Council dyspnea score; pack/year, cumulative history of smoking; PAL, physical activity level; QMVC, quadriceps maximal voluntary contraction; SpO₂, oxygen saturation; SD, standard deviation.

Table 4 Bias and limits of agreement of the five monitors

Monitors	Bias	Limit of agreement
Monitor 1 (Impedance)	−1.18	−20.07 to 17.72
Monitor 2 (PPG)	3.01	−11.17 to 17.19
Monitor 3 (Camera)	−3.21	−12.71 to 6.30
Monitor 4 (Accel)	−2.18	−8.63 to 4.27
Monitor 5 (Chest-band)	−1.60	−9.99 to 6.80

Abbreviation: PPG, photoplethysmography.

Figure 1 Validation of BR in a laboratory setting for five monitors.

Notes: Bland and Altman plots between Oxicon^® BR output and different monitors BR outputs. Solid lines represent the bias, and dotted lines represent 95% limits of prediction.
Abbreviations: Accel, accelerometer; bpm, breath per minute; BR, breathing rate; PPG, photoplethysmography.

Figure 2 Plots of the mean Oxicon^® BR output against the mean output for the other monitors when comparing resting (sitting) with combined activities (fast 6MWT, slow 6MWT, sweeping, and lifting).

Abbreviations: 6MWT, 6 minute walking test; bpm, breath per minute; PPG photoplethysmography; BR, breathing rate.

Figure 3 Evolution of BR shows the overall patient evolution of the BR during the recovery.

Abbreviation: BR, breathing rate.

Figure 4 Example of patients during the monitoring period.

Notes: Panel (A) shows patients 6 and 9 who showed improvements during the recovery process in BR and Panel (B) is an example of a patient who did not show improvements.
Abbreviations: bpm, breath per minute; BR, breathing rate.

Figure 5 Monitored patients 3 and 4 during two cycles of AECOPD.

Abbreviations: bpm, breath per minute; BR, breathing rate; AECOPD, exacerbations of chronic obstructive pulmonary disease; RR, respiratory rate.