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Table 1 Physiological characteristics of the patients—retrospective phase

From: Photoplethysmographic determination of the respiratory rate in acutely ill patients: validation of a new algorithm and implementation into a biomedical device

General characteristics (n = 201)

 Age (mean ± SD)

61.7 ± 14.5

 Sex ratio (F/M)

62/137

 BMI (kg/m2; mean ± SD)

27 ± 6

 SAPS II (mean ± SD)

51.7 ± 18.8

 Chronic respiratory disorder n-(%)

49 (24.3)

 Immunodepression n-(%)

14 (7.1)

 Admission diagnosis

  Respiratory failure n-(%)

83 (41.1)

  Cardiovascular failure n-(%)

56 (27.7)

  Neurological failure n-(%)

36 (17.8)

  Other n-(%)

27 (13.4)

 ICU length of stay (day; mean ± SD)

12.8 ± 14.1

 Hospital length of stay (day; mean ± SD)

28.7 ± 31.4

 Overall survival rate n-(%)

135 (67.8)

Respiratory conditions

 Respiratory rate (c/min; mean ± SD)

22 ± 6

 SpO2 (%; mean ± SD)

95 ± 4

 PaO2/FIO2 or SpO2/FIO2 (mean ± SD)

269 ± 126

 Invasive MV n-(%)

128 (63.7)

  IV sedation n-(%)

87 (43.3)

  Paralysing agents n-(%)

31 (15.4)

  Tidal volume (mL/kg IBW; mean ± SD)

7.1 ± 2.0

  PEEP (cm H2O; mean ± SD)

5.3 ± 2.6

  FIO2 (%; mean ± SD)

38 ± 19

  Patient/ventilator asynchrony n-(%)

28 (21.9)

 Spontaneous breathing n-(%)

73 (36.3)

  Standard oxygen

66 (32.8)

  Non-invasive ventilation

7 (3.5)

  HFNO n-(%)

5 (2.5)

Hemodynamic conditions

 Heart rate (b/min; mean ± SD)

95 ± 22

 Mean arterial blood pressure (mmHg; mean ± SD)

83 ± 16

 Lactate (mmol/L; mean ± SD)

2.8 ± 3.4

 Atrial fibrillation

32 (16.8)

 Vasopressive agent

57 (28.4)

 Hemodynamic instability

29 (14.4)

  1. Values are provided as n-(%) or mean ± SD, unless specified otherwise
  2. Respiratory rate is provided as the reference method (chronometric measurement measured over 30 s under spontaneous ventilation or ventilatory rate for patients under ventilatory assistance)
  3. Chronic respiratory disorders are considered for a previous medical history of COPD, OSA and chronic respiratory insufficiency
  4. Oxygenation parameters are provided as PaO2/FIO2 for patients under mechanical ventilation or as SpO2/FIO2 for patients under spontaneous ventilation
  5. Hemodynamic instability was defined as a need for fluid challenge (≥ 500 mL) and/or vasopressive agent increase during the past 2 h of care
  6. BMI, body mass index; SAPS II, Simplified Acute Physiology Score version 2; ICU, intensive care unit; SpO2, pulse oximetry saturation; PaO2, partial pressure of oxygen in arterial blood; FIO2, inspiratory fraction of oxygen; IV, intravenous; PEEP, positive end-expiratory pressure; HFNO, high-flow nasal oxygen