Changes of Respiratory Mechanics in COPD Patients from Stable State to Acute Exacerbations with Respiratory Failure

Figures & data

Table 1. Demographic, anthropometric and blood gases values of study patients at the enrollment.

Patients, n	18
Age, years	70.3 ± 16.6
Males, n	13
BMI	21±2.1
LTOT, n	18/18
Arterial blood gases
PaO2/FiO2	222.5 ± 56.7
PaCO2, mmHg	76.4 ± 18.3
pH	7.31 ± 0.01
Pulmonary function test ^*
FEV^1 (% predicted value)	0.80 ± 0.19
FVC (% predicted value)	30 ± 8
FEV^1/FVC (%)	39 ± 10
TLC (% predicted value)	79 ± 23
RV (% predicted value)	115 ± 43
RV/TLC (%)	53 ± 11

BMI: body mass index; LTOT: number of patients under long term oxygen during stable state; FiO₂: inspiratory fraction of oxygen; PaO₂: arterial partial pressure of oxygen; PaCO₂: arterial partial pressure of carbon dioxide; FEV¹: forced expiratory volume at first second; FVC: forced vital capacity; TLC: total lung capacity; RV: residual volume.

^* Full pulmonary function test obtained in the stable phase.

Table 2. Patients' respiratory mechanics during EXCOPD (T0) and stable conditions (T1).

	T0	T1	p
Patients, n	18	18
Pes,swing(cm H20)	19.4 ± 6	11.7 ± 6	<0.0001
Pdi,swing (cmH20)	19.3 ± 6	13.3 ± 6	<0.001
Pga,exp(cmH2O)	4.9 ± 3	1.4 ± 2	<0.001
Pes,max,(cm H20)	40.6 ± 12	60 ± 15	<0.0001
Pdi,max(cmH20)	43.3 ± 15	57.8 ± 16	<0.001
PEEPidyn, (cmH20)	2.8 ± 2	1.8 ± 1	<0.001
Rawe cmH20/L/s	17.1 ± 5	10.28 ± 4	<0.000
ΔPga/ΔPes	0.075 ± 0.2	−0.95 ± 0.5	< NS
PTPdi/b(cmH2O/s)	369 ±119	280 ± 114	<0.001
PaO2/FiO2	223 ± 57	297 ± 53	<0.001
PaCO2,(mmHg)	76.4 ± 18	48.3 ± 7	<0.0001
pH	7.31 + 0.0	7.42 + 0.0	<0.0001

Pes,swing: esophageal swing; Pdi,swing: transdiafragmatic swing; Pes,max: maximal negative esophageal swing; Pdi-max: maximal positive diaphragmatic pressure; PTPdi/b: pressure time product of diaphragm calculated per breath; PEEPidyn: intrinsic positive end expiratory pressure; Cldyn: dynamic lung compliance; Rawe: inspiratory resistance. NS: not statistically significant.

Figure 1. PTPdi change during exacerbation (T0) and stable state (T1); ^*p < 0.001.

Table 3. Patients' breathing pattern and dynamic lung volumes during EXCOPD (T0) and stable conditions (T1).

	T0	T1	p
Patients, n	18	18
RR	27.5 ± 0.4	22.9 ± 6.6	<0.0011
VT (L)	0.33 ± 0.1	0.47 ± 0.17	<0.0000
RR/VT	99.8 ± 50.2	59.5 ± 29.1	<0.0001
V'E (l/min)	8.7 ± 2.3	9.95 ± 2.14	<0.001
TI/TTOT	0.35 ± 0.05	0.37 ± 0.04	NS
FEV^1 (L)	0.58 ± 0.16	0.80 ± 0.19	<0.0001
FVC (L)	1.44 ± 0.41	2.12 ± 0.63	<0.000

RR: respiratory rate; VT: tidal volume; VE: minute ventilation; Ti: inspiratory time; T_tot: total time; FEV

¹ forced expiratory volume at first second; FVC: forced vital capacity.

Figure 2. TTdi change during exacerbation (T0) and stable state (T1). Continuous line indicates the threshold of 0.15; ^*p < 0.001.