Can patients with moderate to severe acute respiratory failure from COPD be treated safely with noninvasive mechanical ventilation on the ward?

Figures & data

Figure 1 Consort diagram showing patient enrollment.

Abbreviation: ICU, intensive care unit.

Figure 2 Data recording times of arterial blood gases.

Abbreviations: ABG, arterial blood gas; NIMV, noninvasive mechanical ventilation.

Figure 3 Definition of respiratory acidosis.

Abbreviation: NIMV, noninvasive mechanical ventilation.

Table 1 Characteristics of COPD patients with ARF admitted to emergency room

Variable	7.20≤pH≤7.25 (n=59)	7.26≤pH≤7.30 (n=171)	P-value
Age, mean ± SD (years)	70±10	67±11	0.12
Female (%)	30.5	28.7	0.79
BMI, median (IQR) (kg/m^2)	25 (23–30)	24 (20.2–30)	0.09
Smoking history (%)
Current	25.4	29.4	0.64
Ex-smoker	45.8	45.3	0.80
Systolic arterial pressure (mmHg), mean ± SD	120±23.3	130±12.4	0.33
Diastolic arterial pressure (mmHg), mean ± SD	75±12.4	70±12.2	0.47
Biomass (%)	28.8	25.3	0.33
COPD duration, mean ± SD (years)	11±8	12±9	0.75
LTOT (%)	71.2	78.4	0.27
NIMV at home (%)	49.2	46.8	0.75
Comorbidities (%)
Diabetes mellitus	32.2	23.4	0.19
Arrhythmia	6.8	5.3	0.74
Hypertension	57.6	49.7	0.29
Cardiac disease	55.9	48.5	0.33
Reasons of ARF (%)
Pneumonia	18.6	15.2	0.13
COPD exacerbation due to infection	78.0	82.5	0.45
Congestive right heart failure	3.4	2.3	0.66

Notes: Data with respect to BMI value was missing for 14 patients in group 1 and for 42 patients in group 2. COPD duration data was missing for one patient in group 2.

Abbreviations: ARF, acute respiratory failure; SD, standard deviation; BMI, body mass index; IQR, interquartile range; LTOT, long-term oxygen therapy; NIMV, noninvasive mechanical ventilation.

Table 2 The comparison baseline results of COPD patients with acute respiratory failure at emergency room

Variable	7.20≤pH≤7.25 (n=59)	7.26≤pH≤7.30 (n=171)	P-value
Baseline complete blood count, mean ± SD
White blood cell (×10^9/L)	10,442±5,205	10,854±4,977	0.59
Hemoglobin (g/dL)	13.7±2.3	13.6±2.1	1.26
Hematocrit (%)	42.6±6.6	42±6.9	0.57
Platelet count (×10^9/L)	242±98	264±109	0.17
Baseline blood biochemistry
Glucose (mmol/L) mean ± SD	168±66	153±60	0.12
Blood urea nitrogen, mean ± SD (mmol/L)	27.3±20.6	21.7±12.6	0.051
Creatinine, median (IQR) (mg/dL)	0.95 (0.73–1.26)	0.83 (0.72–1.03)	0.035
Sodium, mean ± SD (mmol/L)	139±4	138±5	0.32
Potassium, mean ± SD (mmol/L)	5±1	5±1	0.34
Albumin, mean ± SD (g/dL)	3.3±0.4	3.3±0.5	0.07
Baseline arterial blood gases
pH, mean ± SD	7.23±0.02	7.28±0.01	0.001
PaCO2, mean ± SD (mmHg)	78.09±16.47	68.28±10.14	0.001
PaO2/FiO2, median (IQR)	345 (225–483)	315 (230–443)	0.52

Abbreviations: SD, standard deviation; IQR, interquartile range; PaCO₂, partial arterial blood carbon dioxide pressure; PaO₂/FiO₂, partial arterial blood oxygen pressure over inspired oxygen fractionation.

Table 3 The outcome of the COPD patients with acute respiratory failure admitted to the ward from emergency room

Variable	7.20≤pH≤7.25	7.26≤pH≤7.30	P-value
	(n=59)	(n=171)
Control ABG after NIMV
pH, mean ± SD	7.33±0.05	7.34±0.04	0.14
PaCO2, mean ± SD (mmHg)	58.68±13.87	58.45±11.26	0.91
PaO2/FiO2, median (IQR)	156 (123–189)	161 (133–211)	0.12
ABG on the last day of ward	n=55	n=168
pH, mean ± SD	7.38±0.06	7.38±0.07	0.84
PaCO2, mean ± SD (mmHg)	57.9±14.9	59.2±12.9	0.53
PaO2/FiO2, median (IQR)	166 (139–212)	169 (140–217)	0.78
Complete blood count on the last day of ward
White blood cell, mean ± SD (×10^9/L)	9,356±3,737	9,946±7,578	0.59
Hematocrit, mean ± SD (%)	40±6.5	39.5±6.5	0.63
Platelet, mean ± SD (×10^9/L)	221±88	252±104	0.056
Peak C-reactive protein, median (IQR) (mg/L)	21 (7.8–54.5)	21.8 (6.0–57.4)	0.73
Outcome of ward
Length of ward stay, median (IQR) (days)	7 (5–8)	6 (5–9)	0.43
Referred to ICU, n (%)	9 (15.3)	26 (15.3)	0.99
Hospital mortality, n (%)	4 (6.8)	4 (2.3)	0.11
Delta pH (control–baseline), mean ± SD	0.11±0.05	0.06±0.04	0.001

Abbreviations: ABG, arterial blood gas; NIMV, noninvasive mechanical ventilation; PaCO₂, partial arterial blood carbon dioxide pressure; SD, standard deviation; PaO₂/FiO₂, partial arterial blood oxygen pressure over inspired oxygen fractionation; IQR, interquartile range; ICU, intensive care unit.

Table 4 The comparison of ABG and blood samples according to the outcome of the patients at the ward

Variable	NIMV success	NIMV failure*	P-value
	(n=193)	(n=37)
Age, mean ± SD (years)	65.86±13.17	68.38±9.69	0.18
Female (%)	29	29.7	0.93
BMI, median (IQR) (kg/m^2)	25 (22–30)	24 (20–28)	0.28
Reasons of ARF (%)
Pneumonia	16.1	16.2	0.98
COPD exacerbation due to infection	81.3	81.1	0.97
Congestive right heart failure	2.6	2.7	0.97
Baseline complete blood count, mean ± SD
White blood cell (×10^9/L)	10,826.3±5,180.2	10,343.7±4,183.8	0.59
Hematocrit (%)	42.09±6.82	42.60±6.74	0.68
Platelet count (×10^9/L)	259.7±107.02	251.5±105.4	0.67
Baseline blood biochemistry
Blood urea nitrogen, mean ± SD (mmol/L)	22.34±14.72	27.14±17.10	0.08
Creatinine, median (IQR) (mg/dL)	0.85 (0.73–1.1)	0.83 (0.7–1.27)	0.81
Albumin, mean ± SD (g/dL)	3.3±0.5	3.2±0.47	0.33
Peak C-reactive protein (mg/dL), median (IQR)	20.4 (6–52.4)	35.2 (15.2–64.9)	0.73
Baseline arterial blood gases
pH, mean ± SD	7.27±0.027	7.26±0.03	0.27
PaCO2, mean ± SD (mmHg)	69.64±12.05	76.80±14.89	0.002
PaO2/FiO2<200, n (%)	25 (13)	13 (35.1)	0.001
Control ABG after NIMV
pH, mean ± SD	7.35±0.04	7.31±0.04	0.001
PaCO2, mean ± SD (mmHg)	56.99±11.72	66.46±9.90	0.001
PaO2/FiO2<200, n (%)	144 (74.6)	24 (64.9)	0.22
Delta pH≤0.3 (control–baseline ABG), n (%)	33 (17.1)	15 (40.5)	0.001
pH≤7.31 at control ABG, n (%)	28 (14.5)	14 (37.8)	0.001

Note:

* Patients passing away at the ward or sent to ICU.

Abbreviations: ABG, arterial blood gas; NIMV, noninvasive mechanical ventilation; SD, standard deviation; ARF, acute respiratory failure; BMI, body mass index; IQR, interquartile range; PaCO₂, partial arterial blood carbon dioxide pressure; PaO₂/FiO₂, partial arterial blood oxygen pressure over inspired oxygen fractionation; ICU, intensive care unit.

Table 5 Binary logistic regression of the risk predictors for NIMV failure (sent to ICU or death) in COPD patients with ARF

Predictors	Odds ratio	95% confidence interval	P-value
		Lower–Upper
pH<7.31 on control ABG after NIMV in ER	2.84	1.09–7.39	0.032
Delta pH<0.30 between baseline and control	1.60	0.59–4.35	0.36
Peak C-reactive protein	1.02	1.01–1.00	0.016
PaO2/FiO2 ratio <200 on control ABG after NIMV	0.66	0.29–1.53	0.34
PaO2/FiO2 ratio <200 on baseline ABG at the ER	3.09	1.28–7.44	0.012

Abbreviations: ABG, arterial blood gas; NIMV, noninvasive mechanical ventilation; ER, emergency room; ARF, acute respiratory failure; PaO₂/FiO₂, partial arterial blood oxygen pressure over inspired oxygen fractionation; ICU, intensive care unit.

Figure 4 Long-term mortality of COPD patient groups according to their pH values on admission to the hospital and after discharge from the hospital.

Figure 5 12-month mortality of COPD patients groups according to the discharge place.

Abbreviation: ICU, intensive care unit.