End-tidal to arterial PCO2 ratio: a bedside meter of the overall gas exchanger performance

Intensive Care Medicine Experimental

Table 3 Respiratory mechanics and hemodynamics across P_ETCO₂/PaCO₂ ratio quartiles

P_ETCO₂/PaCO₂ quartiles	I	II	III	IV	p value
Range	[0.416,0.709]	(0.709,0.796]	(0.796,0.886]	(0.886,1.16]
Number of patients	N = 52	N = 51	N = 48	N = 49
Respiratory variables
E_rs, cmH₂O/L	27.9 [21.4; 33.5]	23.6 [20.4; 30.0]	25.7 [20.1; 30.1]	22.3 [18.1; 27.4]	0.015
Tidal volume, mL	480 [420; 550]	520 [455; 598]	510 [451; 600]	540 [485; 598]	0.064
RR, bpm	18.0 [14.8; 20.0]	16.0 [13.0; 19.0]	16.0 [13.0; 18.0]	15.0 [14.0; 18.0]	0.414
MAP, cmH₂O	12.0 [10.0; 13.0]	11.0 [9.00; 13.0]	11.0 [10.0; 12.0]	10.0 [9.83; 11.5]	0.130
V_A L/min	3.18 [2.74; 4.75]	3.99 [2.86; 5.12]	4.25 [3.44; 5.60]	4.72 [3.33; 5.74]	0.003
VCO₂, mL/min	117 [81.2; 137]	144 [112; 174]	164 [129; 189]	180 [144; 200]	< 0.001
Hemodynamics
HR, bpm	87.0 [71.0; 105]	89.0 [70.5; 96.0]	89.0 [81.0; 106]	96.0 [82.0; 108]	0.245
Mean arterial pressure, mmHg	77.0 [69.5; 86.7]	83.0 [73.7; 90.3]	79.0 [72.0; 87.5]	81.7 [73.2; 89.2]	0.210
CVP, mmHg	11.0 [9.00; 14.0]	11.0 [9.00; 13.0]	12.0 [9.50; 14.0]	12.0 [9.00; 14.0]	0.822

Variables are expressed in medians and IQR. P for Mann–Whitney test. E_rs respiratory system elastance, RR respiratory rate, PEEP end-expiratory pressure, MAP mean airway pressure, V_A alveolar ventilation, HR heart rate, CVP central venous pressure