Non-Invasive Ventilation (NIV) in the Clinical Management of Acute COPD in 233 UK Hospitals: Results from the RCP/BTS 2003 National COPD Audit

Figures & data

Table 2 Casemix factors for those patients with a pH less than 7.35 according to the treatment received

	None (n = 1095)	Non-invasive (n = 529)	Invasive (n = 70)
Median (IQR), n: Age in years	72	(64–78), 1093	71
% (n) Male	53 (580/1095)	47 (63–76), 528	70 (62–76), 69
% (n) Living alone	37 (383/1036)	35 (249/528)	47 (33/70)
% (n) Limited self–care/bed or chair bound	30 (289/972)	35 (171/490)	31 (19/61)
% (n) Heart disease	38 (418)	35 (165/470)	20 (11/56)
% (n) Stroke	5 (54)	3 (186)	34 (24)
% (n) Other chest problems	10 (107)	10 (15)	4 (3)
% (n) Diabetes	10 (107)	12 (55)	13 (9)
% (n) Locomotor problems	11 (118)	10 (61)	10 (7)
% (n) Visual impairment	3 (29)	2 (55)	9 (6)
% (n) CXR suspected or definite cancer	3 (26/933)	2 (10)	1 (1)
% (n) CXR pneumonia**^3	16 (150/933)	27 (8/449)	2 (1/62)
% (n) Current smoker	46 (481/1046)	48 (119/449)	24 (15/62)
% (n) 40+ pack-years of smoking (ex/current)	63 (299/475)	58 (242/499)	56 (35/63)
% (n) with a previous COPD admission	68 (697/1027)	70 (120/208)	69 (18/26)
Median (IQR), n: pH level**^3	7.32 (7.27–7.34), 1063	7.28 (356/511)	59 (38/64)
Median (IQR), n: Bic level**^3	27 (24–32), 942	31 (7.21–7.33), 519	7.24 (7.11–7.34), 65
Median (IQR), n: PCO2 level**^3	7.8 (6.5–9.4), 1059 9.8	(26–36), 476	28 (24–33), 58
Median (IQR), n: PO2 level**^3	9.8 (7.6–14.0), 1056	8.8 (7.9–12.0), 515	9.9 (6.8–13.4), 65
Median (IQR), n: Serum Albumin level	38 (35–41), 719	38 (6.8–12.1), 512	10.5 (6.7–15.8), 64
Median (IQR), n: Blood urea level	6.5 (4.7–9.5), 1016	6.4 (34–41), 390	34 (28–38), 55
Median (IQR), n: Blood creatinine level	89 (72–111), 1021	86 (4.7–9.7), 482	6. (4.8–11.6), 64
Median (IQR), n: Respiratory rate**^3	25 (20–30), 934	28 (71–113), 491	86 (71–111), 62
Median (IQR), n: Oxygen saturation (inspired fraction)**^3	94 (90–96), 877	91 (23–32), 456	28 (24–34), 46
Median (IQR), n: FEV1 most recent within past 5 years	0.7 (0.5–1.0), 584	0.7 (87–95), 446	90 (84–96), 48
Median (IQR), n: Predicted FEV1 most recent in past 5 yrs**^3	32 (24–43), 475	28 (0.5–0.9), 299	0.7 (0.5–1.1), 28
% (n) peripheral oedema at any time**^3	39 (337/860)	48 (21–38), 222	26 (20–38), 16

Table 1 Proportion of patients with a pH < 7.35 receiving NIV treatment according to the availability of NIV treatment within their hospital

Organisational audit				Clinical audit
NIV on wards	NIV on HDU	NIV on ICU	Number of units	% (n) patients received NIV	% (n) In patient mortality	% (n) 90 day mortality
NO	NO	NO	19	11 (13/118)	19 (22/117)	27 (31/116)
NO	NO	YES	14	7 (6/82)	9 (8/85)	24 (20/85)
NO	YES	NO	25	26 (50/189)	16 (31/189)	30 (57/188)
NO	YES	YES	27	21 (39/186)	20 (36/182) 32	(59/182)
YES	NO	NO	29	41 (94/230)	22 (49/226)	33 (74/221)
YES	NO	YES	26	38 (69/184)	19 (34/180)	28 (50/179)
YES	YES	NO	19	35 (46/133)	19 (24/129)	27 (34/128)
YES	YES	YES	74	37 (212/572)	20 (113/569)	28 (157/570)

Table 3 Outcomes for patients with a pH level below 7.35 according to the treatment

	None (n = 1095)	Non-invasive (n = 529)	Invasive (n = 70)
Outcomes (all patients):
% (n) Died as inpatient on index admission**^1	14 (150/1068)	26 (135/520)	43 (30/69)
% (n) Died within 90 days of admission**^1	24 (253/1060)	37 (192/520)	45 (31/69)
% (n) of deaths within 90 days due to COPD	85 (190/224)	93 (170/182)	97 (28/29)
Outcomes (discharged patients):
% (n) Readmitted < 90 days of index admission	35 (315/898)	40 (146/369)	18 (7/38)
Median (IQR), n: LOS in days**^2	7 (4–12), 886	9 (6–15), 369	15 (10–24), 38
% (n) LOS > 7 days**^1	46 (408/886)	64 (237/369)	89 (34/38)
% (n) LOS > 14 days**^1	18 (161/886)	26 (97/369)	55 (21/38)
% (n) admitted under a respiratory physician**^3	30 (333/1095)	43 (226/529)	29 (20/70)
% (n) seen any time by respiratory nurse or physician**^3	74 (799/1082)	91 (477/525)	77 (51/66)
% (n) Second blood gases performed**^3	76 (817/1076)	97 (507/523)	96 (65/68)
Median (IQR), n: 2nd pH level during admission**^3	7.34 (7.30–7.38), 810	7.30 (7.25–7.35), 506	7.25 (7.13–7.33), 63

Note: ventilation status unknown for 20 patients.

**¹. p < 0.001 ‘NIV’ Vs ‘None’, random effects logistic regression (binary outcome as dependent). **². p < 0.001 ‘NIV’ vs ‘None’, random effects linear regression (LOG10(los+1) as dependent variable).

**³. p < 0.001 association of factor with NIV treatment, random effects linear regression (binary ‘NIV’ vs ‘None’ as dependent) with quintiles analysed for numerical factors.

Table 4 Outcomes and NIV treatment: comparison using plant trial criteria using statistical summaries as per plant trial

		Plant		National Audit
		NIV	No NIV	NIV	No NIV
	Patients	118	118	110	227
Age	Mean (SD)	69 (7)	69 (8)	69 (11)	71 (10)
Male	% (n)	46 (54)	53 (63)	46 (50)	50 (114)
First PCO2	Mean (SD)	8.82 (1.51)	8.65 (1.70)	9.56 (1.98)	8.03 (1.44)
Second PCO2	Mean (SD)	8.18 (2.00), n = 101	8.45 (1.91), n = 106	10.34 (6.10), n = 106	7.57 (2.15), n = 154
First pH	Median (5-95th centile range)	7.32 (7.25–7.35)	7.31 (7.26–7.35)	7.29 (7.25–7.34)	7.32 (7.26–7.35)
Second pH	Median (5-95th centile range)	7.34 (7.24–7.41), n = 101	7.32 (7.23–7.38), n = 106	7.32 (7.16–7.44), n = 106	7.36 (7.27–7.44), n = 153
First Respiratory rate	Median (5-95th centile range)	28 (24–36)	28 (24–40)	28 (24–40)	28 (24–38)
FEV1 (in L)**	Median (5-95th centile range)	0.71 (0.28–1.47)	0.68 (0.37–2.00)	0.67 (0.31–1.68), n = 61	0.70 (0.29–1.57), n = 126
Mortality ^+ +	% (n)	10 (12)	20 (24)	27 (29/107)^+ +	8 (18/220)^+ +
Mortality if initial pH = 7.25–7.29	% (n)	22 (8/36)	34 (13/38)	20 (11/54)	14 (9/64)
Mortality if initial pH = 7.30–7.35	% (n)	5 (4/82)	14 (11/80)	34 (18/53)	6 (9/156)
Length of stay ***	Median (range)	10 (4–137)	10 (2–119)	9 (0–120)	7 (0–115)

*For Plant trial first PCO₂ was at baseline (before randomisation and at most within 12 hours of admission), the second 1 hour later. For National audit the first was at admission, the second time was within 12 hours of admission.

**For Plant trial FEV at discharge. For National audit most recent recorded within last 5 years.

***Discharges and deaths.

⁺⁺For National audit: p < 0.001 for ‘NIV’ Vs ‘No NIV’, random effects logistic regression.

Table 5 Patients with lowest pH < 7.35, treated or untreated with NIV and grouped by their propensity to receive NIV

	Propensity group 1–3				Propensity group 4				Propensity group 5
	1–31% chance of NIV				32–57% chance of NIV				58–94% chance of NIV
	No NIV		NIV		No NIV		NIV		No NIV		NIV
	%	n	%	n	%	n	%	n	%	n	%	N
Outcomes:
% Death during index admission	12	97/809	26	38/147	18	29/165	23	35/149	26	24/92	28	62/223
% Death < 90 days of index admission	22	173/802	34	50/147	27	45/165	39	58/148	38	35/91	38	84/224
% Readmission < 90 days of index admission	35	241/695	37	38/104	34	46/134	36	40/112	42	28/67	44	67/152
% LOS > 7 days	43	294/689	52	54/103	56	73/130	69	76/110	60	39/65	69	107/155
% LOS > 14 days	16	109/689	22	23/103	25	33/130	25	27/110	28	18/65	30	47/155
Strongest Predictors of Niv:
% 75+ years	39	322/825	38	56/147	41	70/172	34	52/152	30	29/96	25	58/228
% Admitted to hospital under a respiratory physician	26	218/825	33	48/147	39	68/172	39	60/152	49	47/96	51	116/228
% CXR pneumonia	13	94/710	19	23/120	21	30/140	21	29/135	30	25/82	35	67/192
% With oxygen saturation < 92% on inspired fraction	33	210/641	42	52/125	53	77/146	54	68/127	76	67/88	72	138/193
% With lowest documented pH < 7.26	19	146/761	33	46/139	55	92/167	56	83/148	78	75/96	83	188/227
% Second PCO2 > 10.0	7	36/538	8	10/122	20	34/170	25	37/150	55	53/96	68	155/228
% Second Bic > 30	27	132/486	38	43/113	47	74/158	50	69/138	74	66/89	73	156/215
% In units with NIV available on wards	53	433/825	61	90/147	80	138/172	78	119/152	83	80/96	92	210/228
Other Admission Characteristics:
% Male	56	458/825	56	82/147	48	83/172	48	73/152	41	39/96	41	93/228
% Living alone	37	287/781	34	46/137	41	67/163	35	50/142	31	28/90	36	75/209
% Limited self care / bed or chair bound	28	207/728	29	36/124	34	53/155	31	41/132	33	29/87	41	86/212
% Previous COPD admission	68	525/767	68	94/139	66	110/166	71	104/147	66	61/92	70	157/223
% Current smoker	44	349/794	49	69/140	49	80/163	41	60/146	59	51/87	53	113/211
% Serum Albumin level at admission < 34 g/l	17	89/530	24	26/109	21	24/116	19	22/113	24	17/71	21	35/166
% Blood urea level at admission > 7.1 nmol/l	42	318/762	43	55/127	49	78/160	41	58/140	42	39/92	47	100/213
% Respiratory rate at admission 30+	30	209/704	34	42/125	33	48/145	38	49/129	35	29/83	41	82/200
% pH < 7.26 at admission	13	103/806	24	34/143	36	59/163	34	50/148	50	46/92	55	124/226
% Bic > 30 at admission	24	169/709	33	43/131	46	68/147	46	62/134	60	50/84	66	137/209
% PCO2 > 6.0 at admission	81	651/800	83	115/139	94	155/165	93	138/148	95	87/92	96	218/226