One-Year Readmission Following Undifferentiated Acute Hypercapnic Respiratory Failure

Figures & data

Figure 1. Flow chart of patients included in the study.

Table 1. Patients baseline and in-hospital characteristics.

	Patients (N = 212)	Not readmitted (n = 64)	Readmitted	P value
			(n = 148)
Baseline characteristics
Age, years	67.6 (57.6;77.6)	68.3 [54.3;77.4]	67.2 [58.5;77.6]	0.678
Male sex	127 (59.9%)	38 (59.4%)	89 (60.1%)	1.000
BMI (n = 164)	25.8 (21.7;31.6)	29.1 [23.9;34.2]	25.2 [20.7;30.5]	0.035
Smoking history (previous or current)	136 (64.1%)	37 (57.8%)	99 (66.9%)	0.267
Alcohol abuse	31 (14.6%)	11 (17.2%)	20 (13.5%)	0.629
Recreational drugs use	35 (16.5 %)	8 (12.5%)	27 (18.2%)	0.405
Followed by respirologist	84 (39.6%)	19 (29.7%)	65 (43.9%)	0.073
Pulmonary function test available	82 (38.7%)	19 (29.7%)	63 (42.6%)	0.106
Polysomnography available	11 (5.2%)	1 (8.33%)	10 (34.5%)	0.128
FEV1/FVC (n = 74)	0.59 (0.39;0.67)	0.61 [0.53;0.65]	0.55 [0.38;0.68]	0.456
FEV1 %predicted (n = 82)	41.5 (30.0;57.8)	45.0 [31.0;61.5]	40.0 [30.0;57.5]	0.696
FEV1% predicted, GOLD categories, (n = 82)				0.706
>80	7 (8.54%)	1 (5.26%)	6 (9.52%)
50–80	21 (25.6%)	6 (31.6%)	15 (23.8%)
<50	54 (65.9%)	12 (63.2%)	42 (66.7)
Echocardiography available	124 (58.5%)	28 (43.8%)	96 (64.9%)	0.007
Reduced EF (<50%) (n = 124)	31 (25.0%)	9 (32.1%)	22 (22.9%)	0.457
Charlson Comorbidity index	2.00 (1.00;3.00)	1.00 [1.00;2.00]	2.00 [1.00;3.00]	0.013
Comorbidities:
Cardiovascular	141 (66.5%)	35 (54.7%)	106 (71.6%)	0.025
Psychiatric disorders	67 (31.6%)	17 (26.6%)	50 (33.8%)	0.380
Diabetes	49 (23.1%)	11 (17.2%)	38 (25.7%)	0.243
Moderate to severe renal insufficiency	23 (10.8%)	3 (4.69%)	20 (13.5%)	0.098
Main chronic disease:
COPD	127 (59.9%)	34 (53.1%)	93 (62.8%)	0.241
Asthma	46 (21.7%)	15 (23.4%)	31 (20.9%)	0.824
OSA/OHS	41 (19.3%)	12 (18.8%)	29 (19.6%)	1.000
CHF	76 (35.8%)	23 (35.9%)	53 (35.8%)	1.000
Home oxygen therapy	27 (12.7%)	8 (12.5%)	19 (12.8%)	1.000
Home CPAP or BIPAP	17 (8.02%)	3 (4.69%)	14 (9.46%)	0.369
Home medications
Short acting bronchodilators	110 (51.9%)	27 (42.2%)	83 (56.1%)	0.087
Long acting bronchodilators	108 (50.9%)	25 (39.1%)	83 (56.1%)	0.034
Inhaled steroids	91 (42.9%)	22 (34.4%)	69 (46.6%)	0.133
Anti-hypertensive drugs	111 (52.4%)	32 (50.0%)	79 (53.4%)	0.762
Benzodiazepines/antidepressants/antipsychotics	78 (36.8%)	20 (31.2%)	58 (39.2%)	0.344
Opioids	31 (14.6%)	8 (12.5%)	23 (15.5%)	0.716
Hospital admission previous year	86 (40.6%)	11 (17.2%)	75 (50.7%)	<0.001
ICU admission previous year	15 (7.08%)	0 (0.00%)	15 (10.1%)	0.006
NIV previous year	18 (8.49%)	1 (1.56%)	17 (11.5%)	0.035
IMV previous year	8 (3.77%)	0 (0.00%)	8 (5.41%)	0.109
Hospital characteristics
Admitted from home	169 (80.1%)	53 (82.8%)	116 (78.9%)	0.582
Length of stay in ED—hours	10.7 (6.62;17.6)	10.4 [6.73;16.6]	10.7 [6.62;17.7]	0.840
Length of stay as inpatient—days (n = 158)	5.72 (2.89;8.58)	4.81 [2.79;6.93]	5.78 [3.03;9.30]	0.239
Venous blood gas at ED admission (n = 209):
vpH at ED admission,	7.29 (7.25;7.32)	7.31 [7.25;7.33]	7.29 [7.25;7.32]	0.191
vpCO2 at ED admission,	62.0 (55.0;72.0)	61.5 [54.0;71.0]	62.0 [55.0;72.5]	0.707
vHCO3 at ED admission	32.0 (29.0;35.0)	31.0 [29.0;34.2]	32.0 [29.0;35.0]	0.708
Arterial blood gas at ED admission (n = 25):
apH at ED admission,	7.26 (7.19;7.30)	7.22 [7.18;7.29]	7.26 [7.19;7.30]	0.587
apCO2 at ED admission,	64.0 (47.0;72.0)	60.0 [51.0;70.5]	64.0 [46.0;72.5]	0.679
aHCO3 at ED admission,	30.0 (24.0;36.0)	26.5 [24.5;33.0]	30.0 [23.5;37.0]	0.609
DNR (n = 150)	21 (14%)	6 (9.38%)	15 (10.1%)	0.053
Type of ventilatory support
none	150 (70.7%)	44 (68.8%)	106 (71.6%)	0.797
NIV only	44 (20.7%)	18 (28.1%)	26 (17.6%)	0.120
IMV	18 (8.5%)	2 (3.12%)	16 (10.8%)	0.115
Hospital location
ED only	54 (25.4%)	21 (32.8%)	33 (22.3%)	0.149
Ward only	122 (57.5%)	37 (57.8%)	85 (57.4%)	1.000
ICU	36 (16.9%)	6 (9.38%)	30 (20.3%)	0.082
Referrals	75 (35.4%)	24 (37.5%)	51 (34.5%)	0.788

CCI = Charlson Comorbidity Index, FEV1 = expiratory volume in the first second, EF = ejection fraction, RAA = renin-angiotensin system, NIV = noninvasive ventilation, IMV = invasive mechanical ventilation. ED = emergency department, ICU = intensive care unit, pCO2 = partial pressure of CO2, HCO3 = bicarbonates, DNR = do not reanimate, IMV = invasive mechanical ventilation, NIV = noninvasive ventilation. Cardiovascular comorbidities include hypertension, arrhythmias, coronary artery disease and pulmonary hypertension. Moderate to severe renal insufficiency = on dialysis, status post kidney transplant, uremia, creatinine >3 mg/dL. Referrals = after-discharge visit to a pneumologist, cardiologist or sleep laboratory.

Figure 2. Main diseases that can lead to AHRF in our population (n = 212). Each oval figure represents a disease; overlapping of figures indicates the presence of more than one disease. Areas in the figures represent the prevalence of the diseases. COPD = chronic obstructive pulmonary disease, CHF = congestive heart failure, OSA = obstructive sleep apnea, OHS = obesity-hypoventilation syndrome. Numbers in bold represent the total number in a given category.

Table 2. Cumulative number of patients readmitted and deceased due to all causes at different times after discharge from index event (n = 212).

Time (days)	Deceased patients, N (%)	Admitted patients, N (%)	ED visit patients, N (%)	Total admitted patients (inpatients or ED visit), N (%)	Number of admissions or ED visits, median (IQR)
30	3 (1.4%)	51 (24.1%)	34 (16%)	73 (34.4%)	1 (1–2)
90	5 (2.4%)	77 (36.3%)	59 (27.8%)	113 (53.3%)	1 (1–3)
180	10 (4.7%)	94 (44.3%)	70 (33%)	128 (60.4%)	2 (1–3)
365	19 (8.96%)	117 (55.2%)	95 (42.5%)	150 (70.8%)	2 (1–4.8)

Table 3. Predictors of adverse outcomes (readmissions and death) at one year.

Variables	Univariate HR (CI 95%);	Model 1	Model 2
	P-value	HR (CI 95%); P-value	HR (CI 95%); P-value
Age	1 (1–1); p = 0.053	0.99 (0.98–1.01); p = 0.471	1.0 (0.98–1.01); p = 0.881
COPD	1.3 (0.93–1.8); p = 0.12	1.13 (0.70–1.83); p = 0.597	1.03 (0.65–1.63); p = 0.906
Asthma	0.9 (0.61–1.3); p = 0.6	0.85 (0.55–1.31); p = 0.458	0.85 (0.55–1.29); p = 0.443
OSA/OHS	0.99 (0.66–1.5); p = 0.95	0.75 (0.48–1.17); p = 0.209	0.87 (0.57–1.33); p = 0.532
Congestive heart failure	1.1 (0.77–1.5); p = 0.68	0.82 (0.54–1.24); p = 0.361	1.05 (0.71–1.56); p = 0.810
Charlson Comorbidity Index	1.1 (1–1.2); p = 0.004		1.05 (0.94–1.17); p = 0.329
Cardiovascular comorbidities	1.64 (1.15–2.34); p = 0.005	1.82 (1.16–2.87); p = 0.009	–
Psychiatric disorder	1.1 (0.79–1.6); p = 0.57	1.19 (0.83–1.71); p = 0.337	–
Diabetes	1.3 (0.88–1.8); p = 0.21	0.96 (0.64–1.45); p = 0.880	–
Severe renal insufficiency	1.9 (1.2–3.1); p = 0.008	1.62 (0.92–2.85); p = 0.091	–
Long acting bronchodilators	1.5 (1.1–2.1); p = 0.015	1.17 (0.74–1.84); p = 0.504	1.23 (0.79–1.92); p = 0.354
Unplanned admissions previous year	2.5 (1.8–3.5); p < 0.001	2.34 (1.65–3.32); p < 0.001	2.33 (1.65–3.29); p < 0.001
Ventilatory support
NIV only	0.83 (0.54–1.25); p = 0.376	0.78 (0.51–1.21); p = 0.272	0.79 (0.52–1.21); p = 0.281
IMV	1.66 (0.98–2.82); p = 0.058	1.42 (0.82–2.45); p = 0.209	1.36 (0.77–2.39); p = 0.280
Hospital location
Ward only	1.33 (0.89–2.00); p = 0.153	–	–
ICU	1.82 (1.11–2.98); p = 0.018	–	–

Figure 4. Kaplan-Meier curves comparing patients that received ventilatory support to the ones that didn’t receive ventilatory support.

Figure 3. Kaplan-Meier curve of free-event survival at one year in the overall group.

Figure 5. Kaplan-Meier curves comparing patients that received invasive ventilatory support (IMV), received only noninvasive ventilatory support (NIV only) and didn’t receive ventilatory support (no support).