Flow Index: a novel, non-invasive, continuous, quantitative method to evaluate patient inspiratory effort during pressure support ventilation

Table 2 Inspiratory effort and breathing pattern at PS_min, PS_base and PS_max

	PS_min	PS_base	PS_max	P value
Set pressure support level (cmH₂O)	4 ± 1	10 ± 3	18 ± 5	< 0.001
Tidal volume (ml)	440 ± 132	511 ± 146	671 ± 217	< 0.001
Tidal volume/IBW (ml kg⁻¹)	6.6 (1.7)	7.9 (1.9)	10.5 (2.4)	< 0.001
Respiratory rate (min⁻¹)	31 ± 10	26 ± 10	20 ± 6	< 0.001
RSBI	78 ± 36	58 ± 31	34 ± 19	< 0.001
Minute ventilation (l min⁻¹)	11.6 ± 4.0	11.7 ± 4.3	11.7 ± 3.9	0.98
PTP_pt,minute (cmH₂O⋅s min⁻¹)	83 ± 93	32 ± 94	8 ± 26	< 0.001
PTP_pt,breath (cmH₂O⋅s)	4.0 (2.9)	2.3 (2.2)	0.9 (1.4)	< 0.001
PTP_ratio,breath	0.76 ± 0.3	0.29 ± 0.28	0.06 ± 0.09	< 0.001
P_musc (cmH₂O)	7.5 (4.4)	4.3 (3.6)	1.9 (2.6)	< 0.001
Flow Index	4.6 ± 3.3	3.3 ± 2.5	1.9 ± 1.3	< 0.001

All pairwise comparisons between the three PS levels were significant (p < 0.05), except for minute ventilation
PS_min = minimal pressure support, PS_base = baseline pressure support, PS_max = maximal pressure support, RSBI = Rapid Shallow Breathing Index obtained by the ratio of respiratory rate and V_T, PTP_pt,minute = Pressure–time product for the patient in one minute, PTP_pt,breath = Pressure–time product for the patient in a single breath, PTP_ratio,breath = PTP_pt,breath/(PTP_{pt, breath} + PTP_{vent, breath}), P_musc = pressure generated by respiratory muscles

ISSN: 1364-8535