Table 2.

Respiratory measurements according to different techniques—retrospective phase

Number of patients with reference values
Manual-RR n-(%)	199/201 (99.0)
Ventilator-RR n-(%)	128/128 (100)
PPG-RR n-(%)	193/201 (96.0)

Measurements (c/min)
Reference RR	Estimated RR-PPG	R	ICC	p
22 ± 4	22 ± 5	0.955	0.931	< 0.0001

Reference RR under MV	Estimated RR-PPG under MV
21.9 ± 5.4	21.8 ± 5.6	0.952	0.793	< 0.0001
With VT > median	With VT > median
20.1 ± 3.9	20.0 ± 4.1	0.947	0.969	< 0.0001
With VT ≤ median	With VT ≤ median
22.6 ± 6.1	22.5 ± 6.2	0.974	0.886	< 0.0001

Reference RR under SB	Estimated RR-PPG under SB
23.2 ± 5.8	22.9 ± 5.9	0.940	0.963	< 0.0001

Reference RR without AF	Estimated RR-PPG without AF
22.1 ± 5.6	22.0 ± 5.8	0.954	0.973	< 0.0001

Reference RR with AF	Estimated RR-PPG with AF
20.6 ± 3.7	20.5 ± 4.0	0.916	0.689	< 0.0001

Values are provided as n-(%) or mean ± SD (b/mn), unless specified otherwise. R, Pearson’s correlation coefficient; ICC, intraclass correlation coefficient for average measurements, was assessed to evaluate the reliability of measurements; a p value < 0.01 was considered statistically significant for a bilateral test

Reference RR values are provided as the chronometric measurement measured over 30 s under spontaneous ventilation or as the ventilatory rate for patients under ventilatory assistance

RR, respiratory rate; PPG, plethysmographic measurement; Manual-RR, chronometric evaluation of the RR, over a 30-s period; Ventilator-RR, RR value provided by the ventilator in case of mechanical ventilation; PPG-RR, estimated respiratory rate using the plethysmographic curve analysis; MV, mechanical ventilation; SN, spontaneous breathing; AF, atrial fibrillation; VT, tidal volume (median tidal volume = 475 mL)