Noninvasive ventilation with complex critical care ventilator in the treatment of acute exacerbation of chronic obstructive pulmonary disease

Abstract

Objective

To compare the clinical effect of noninvasive positive-pressure ventilation (NIPPV), delivered via critical care ventilator or miniventilator, in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD).

Methods

Prospective comparison study. Patients with AECOPD underwent NIPPV via: miniventilator with BiLevel positive airway pressure (BiPAP; Group A); critical care ventilator with pressure support ventilation and positive end expiratory pressure (PSV + PEEP; Group B); critical care ventilator with pressure-synchronized intermittent mandatory ventilation (P-SIMV)+PSV + PEEP (Group C). Physiological parameters were recorded before, during and after ventilation.

Results

Patients in Group C (n = 21) showed significantly better improvements in physiological parameters (compared with pretreatment values) than those in Group B (n = 20) or Group A (n = 22).

Conclusion

NIPPV delivered via critical care ventilator has a better treatment effect than miniventilator NIPPV in patients with AECOPD. The use of P-SIMV + PSV + PEEP mode provides a significantly better treatment effect than PSV + PEEP alone.

Keywords

Noninvasive ventilation chronic obstructive pulmonary disease oronasal mask

Introduction

Chronic obstructive pulmonary disease (COPD) is characterized by persistent, usually progressive airflow limitation and is a leading cause of morbidity and mortality worldwide.¹ Acute exacerbations of COPD (AECOPD) are important events in the disease course because they have long-term effects on symptoms and lung function, accelerate lung function decline, and are associated with substantial mortality, particularly in those requiring hospitalization.¹ In addition to pharmacological therapy, hospital management of AECOPD includes respiratory support with oxygen therapy and noninvasive (nasal or facial mask) or invasive (orotracheal tube or tracheostomy) ventilation. Noninvasive positive-pressure mechanical ventilation (NIPPV) delivers positive-pressure support to the lungs without the use of an invasive artificial airway and is more convenient, comfortable, safe and economic than invasive mechanical ventilation. NIPPV also avoids endotracheal intubation and intubation-related complications, allows patients to eat, drink, talk and expectorate, and has become the standard of care in hypercapnic respiratory failure secondary to COPD.² Randomized controlled trials have shown that NIPPV is an effective treatment for acute exacerbations of COPD.^3–5 NIPPV has been shown to improve acute respiratory acidosis (increase pH and decrease arterial carbon dioxide partial pressure [PaCO₂]), and decrease respiratory rate, breathing effort, severity of breathlessness, complications (including ventilator associated pneumonia) and duration of hospital stay.

Conventional NIPPV is generally provided using a miniventilator with BiLevel positive airway pressure mode, and the application and outcome of treatment are limited by factors including machine function and the use of single-limb tubing (which can increase carbon dioxide rebreathing and leaks).⁶ Complex critical care ventilators, on the other hand, provide full function, excellent performance and multiple modes of operation.⁶ The aim of the present study was to compare the treatment outcome of NIPPV with either a complex critical care ventilator or a miniventilator in patients with AECOPD.

Patients and methods

Study population

This prospective study enrolled consecutive patients with AECOPD (diagnosed according to AECOPD diagnostic standards¹) admitted to the Emergency Department, Department of Respiratory Diseases or Surgical Intensive Care Unit (SICU), Tianjin Medical University General Hospital, Tianjin, China, between June 2010 and June 2012. Inclusion criteria were: willing to accept NIPPV with disposable full oronasal mask and gastrointestinal decompression if necessary; initial respiratory rate >23 breaths/min or using ancillary respiratory muscles/paradoxical breath; arterial oxygen partial pressure (PaO₂) < 70 mmHg (1 mmHg= 0.133 kPa), PaO₂/fraction of inspired oxygen (PaO₂/FiO₂) <200, PaCO₂ > 55 mmHg or PaCO₂ > 45 mmHg and pH < 7.35after 6–8 h oxygen therapy with nasal cannula (3–5 /min).

The study was approved by the Ethics Committee of the General Hospital of Tianjin Medical University, and written informed consent was obtained from all patients or their next-of-kin.

Treatment

Patients were assigned randomly to one of three groups by a random-number table at study entry and were ventilated using the study method for 8 h. During ventilation, all patients received standard AECOPD pharmacological therapy (e.g. bronchodilators, corticosteroids and antibiotics), routine secretion drainage and conventional supportive treatment, as required on an individualized basis.

Patients in Group A were ventilated using a traditional miniventilator (BREAS Medical, Mölnlycke, Sweden) with a disposable oronasal mask and auto-BiLevel positive airway pressure (PAP) mode. Ventilator parameters were: 7–8 l/min oxygen (FiO₂ 40–60%); oxygen flow rate increased when PaO₂ < 40 mmHg; high-pressure phase 15 cmH₂O (1cmH₂O = 0.098 kPa); low-pressure phase 5 cmH₂O (triggered at 2–3 cmH₂O).

Patients in Group B were ventilated using a critical care ventilator (Galileo Gold; Hamilton Medical, Bonaduz, Switzerland) with a disposable oronasal mask and spontaneous mode (PSV + PEEP). Ventilator parameters were: FiO₂ 40–60% (increased at PaO₂ < 40 mmHg); PSV 10 cmH₂O, PEEP 5 cmH₂O; trigger-flow rate 3 l/min at anterior extremity; expiratory trigger sensitivity (ETS) 40%; pressure ramp time (Pramp) 25 ms.

Patients in Group C were ventilated using a critical care ventilator (Galileo Gold) with a disposable oronasal mask and pressure-synchronized intermittent mandatory ventilation (P-SIMV) + PSV + PEEP mode. Ventilator parameters were: FiO₂ 40–60% (increased at PaO₂ < 40 mmHg); PSV 10 cmH₂O; PEEP 5 cmH₂O; controlled Pressure (Pcontrol) 25 cmH₂O (30 cmH₂O including PEEP); Pcontrol phase time 1.0 s; mandatory rate 10 ventilations/min; flow rate trigger 3 l/min at anterior extremity; ETS 40%; and Pramp 25 ms.

Before NIPPV, standard physiological parameters were recorded, patients were asked to expectorate (alternatively, suction was used), gastrointestinal decompression was performed (to relieve abdominal distention and prevent digestive tract haemorrhage) and an oropharyngeal tube was used if necessary to prevent the tongue root from falling. Airway aspiration was repeated every 1–2 h throughout ventilation. In group A, clinical parameters were recorded manually following ventilation. In groups B and C, software within the ventilator recorded and analysed additional clinical data regarding oral obstructive pressure at 0.1 s after initiation of inhalation (P0.1), peak expiratory flow (PEF), rapid superficial breath index (RSB), maximal inspiratory resistance (R_in) and maximal expiratory resistance (R_ex).

After 8 h NIPPV, treatment was considered failed under the following circumstances: patient could not tolerate NIPPV; arterial oxygen saturation (SaO₂) < 85%, PaO₂ < 50 mmHg, PaCO₂ remained unchanged and/or pH < 7.20–7.25 during and after ventilation; severe expectoration difficulty; symptoms too severe to allow ventilation (e.g. spontaneous respiratory rate <5 breaths/min, low tidal volume, etc.); artificial airway required; death.

Inflection point was determined via pressure–volume tools in the critical care ventilator. Inflection point improvement was defined as any of the following: lower inflection point disappeared; lower inflection point enlarged to steep inflection fragment; increased slope of line connecting upper and lower inflection point; increased slope of tangent of pressure–volume curve (P–V curve).

After the 8-h study period, improved patients stayed on the same kind of ventilation as used during the study period. Patients classified as treatment failures received adjusted treatment (i.e. a different mode of ventilation, different ventilation parameters, or invasive ventilation).

Statistical analyses

Descriptive data were presented as mean ± SD. Between-group comparisons were made using one-way analysis of variance. Statistical analyses were performed using SPSS® version 11.5 (SPSS Inc., Chicago, IL, USA) for Windows®. P-values < 0.05 were considered statistically significant.

Results

The study included 63 patients with AECOPD (32 male/31 female; mean age 70.14 ± 5.72 years; age range 61–83 years). Baseline physiological parameters of the study cohort, stratified according to treatment group, are shown in Table 1. There were no statistically significant between-group differences in any demographic or baseline physiological parameter.

Table 1.

Baseline demographic and physiological parameters of patients with acute exacerbation of chronic obstructive pulmonary disease, included in a study to compare different types of noninvasive positive-pressure mechanical ventilation.

Characteristic	Group A BiLevelPAP^a n = 22	Group B PSV+PEEP^b n = 20	Group C P-SIMV+PSV +PEEP^b n = 21
Sex, male/female	10/12	11/9	11/10
Age, years	70.91 ± 5.74	70.60 ± 6.36	68.90 ± 5.03
Respiratory rate, breaths/min	32.09 ± 5.57	31.90 ± 6.17	32.62 ± 5.86
PaO₂/FiO₂, mmHg	139.09 ± 35.68	126.35 ± 32.99	139.62 ± 33.22
PaCO₂, mmHg	88.50 ± 25.39	88.40 ± 19.77	85.81 ± 26.59
pH	7.18 ± 0.13	7.17 ± 0.10	7.20 ± 0.08
Glasgow coma score	7.09 ± 1.31	6.95 ± 1.67	6.52 ± 1.21

Data presented as n or mean ± SD.

Miniventilator.

Critical care ventilator.

No statistically significant between-group differences (P ≥ 0.05); one-way analysis of variance.

Data regarding physiological parameters before and after ventilation are shown in Table 2. Ventilation resulted in significant changes in respiratory rate, Glasgow coma score, PaO₂/FiO₂, PaCO₂ and pH in all study groups (P < 0.05 for each comparison). Patients in groups B and C (who were ventilated via critical care ventilator) showed significant postventilation changes in P0.1, PEF, RSB, R_in, R_ex and inflection point (P < 0.05 for each comparison).

Table 2.

Physiological parameters in patients with acute exacerbation of chronic obstructive pulmonary disease, before and after noninvasive positive-pressure mechanical ventilation for 8 h.

Parameter	Group A BiLevelPAP^a n = 22		Group B PSV+PEEP^b n = 20		Group C P-SIMV + PSV + PEEP^b n = 21
Parameter	Before treatment	After treatment	Before treatment	After treatment	Before treatment	After treatment
Respiratory rate, breaths/min	32.09 ± 5.57	29.41 ± 5.30**	31.90 ± 6.17	27.65 ± 7.04**	32.62 ± 5.86	26.38 ± 7.28**
Glasgow coma score	7.09 ± 1.31	9.59 ± 1.62**	6.95 ± 1.67	10.45 ± 2.61**	6.52 ± 1.21	12.00 ± 1.64**
PaO₂/FiO₂, mmHg	139.09 ± 35.68	153.82 ± 37.01**	126.35 ± 32.99	152.30 ± 34.77**	139.62 ± 33.22	172.43 ± 39.80**
PaCO₂, mmHg	88.50 ± 25.93	80.68 ± 24.66**	88.40 ± 19.77	76.90 ± 18.69**	85.81 ± 26.59	64.43 ± 22.24**
pH	7.18 ± 0.13	7.20 ± 0.12**	7.17 ± 0.10	7.22 ± 0.10**	7.20 ± 0.08	7.27 ± 0.10**
Failure rate, n (%)	–	18 (81.8)	–	8 (40.0)	–	3 (14.3)
P0.1, cmH₂O	NA	NA	2.73 ± 3.20	1.59 ± 1.30*	4.79 ± 3.80	2.39 ± 1.54**
PEF, l/min	NA	NA	117.69 ± 52.63	124.10 ± 54.58**	106.91 ± 33.43	128.57 ± 35.34**
RSB, breaths/(min × l)	NA	NA	149.40 ± 48.57	131.25 ± 49.40**	167.62 ± 57.96	139.48 ± 54.97**
R_in, cmH₂O/l per s	NA	NA	27.68 ± 5.30	24.30 ± 6.22**	26.19 ± 4.35	18.48 ± 5.08**
R_ex, cmH₂O/l per s	NA	NA	23.65 ± 4.52	20.47 ± 4.72**	25.76 ± 4.60	19.47 ± 6.22**
Inflection point improvement rate, n (%)	NA	NA	–	10 (50.0)	–	19 (90.5)

Data presented as mean ± SD.

Miniventilator.

Critical care ventilator.

P < 0.05, **P < 0.01 versus before treatment values; one-way analysis of variance.

PAP, positive airway pressure; PSV, pressure support ventilation; PEEP, positive end expiratory pressure; P-SIMV, pressure-synchronized intermittent mandatory ventilation (P-SIMV); PaO₂, arterial oxygen partial pressure; FiO₂, fraction of inspired oxygen; PaCO₂, arterial carbon dioxide partial pressure; P0.1, oral obstructive pressure at 0.1 s after initiation of inhalation; NA, not available (miniventilator cannot measure P0.1, PEF, RSB, R_in, R_ex or inflection point); PEF, peak expiratory flow; RSB, rapid superficial breath index; R_in, maximal inspiratory resistance; R_ex, maximal expiratory resistance.

Table 3 provides data regarding between-group differences in changes in physiological parameters following ventilation (compared with pretreatment values). Patients ventilated via P-SIMV + PSV + PEEP (Group C) showed significantly greater changes in all parameters except PaO₂/FiO₂, pH, and greater failure rate, than those in Group B (PSV + PEEP; P < 0.05 for each comparison, Table 3). In addition, P-SIMV + PSV + PEEP resulted in significantly greater changes in all quantifiable parameters than BiLevel PAP (Group A; P < 0.05 for each comparison). PSV + PEEP (Group B) resulted in significantly greater changes in pH and failure rate when compared with BiLevel PAP (Group A; P < 0.05 for each comparison).

Table 3.

Between-group differences in changes in physiological parameters (compared with pretreatment values) following noninvasive positive-pressure mechanical ventilation for 8 h in patients with acute exacerbation of chronic obstructive pulmonary disease.

Parameter	Group C – Group B	Group C – Group A	Group B – Group A
Respiratory rate, breaths/min	1.99*	3.56**	1.57
Glasgow coma score	1.98**	2.98**	1.00
PaO₂/FiO₂, mmHg	6.86	18.08*	11.22
PaCO₂, mmHg	9.88**	13.56**	3.68
pH	0.016	0.044**	0.028*
Failure rate, %	−25.71	−67.53**	−41.82**
P0.1, cmH₂O	1.262*	NA	NA
PEF, l/min	15.25**	NA	NA
RSB, breaths/(min × l)	9.99*	NA	NA
R_in, cmH₂O/l per s	4.33**	NA	NA
R_ex, cmH₂O/l per s	3.11**	NA	NA
Inflection point improvement rate, %	40.48**	NA	NA

Data presented as absolute values.

P < 0.05, **P < 0.01; one-way analysis of variance.

Group A, miniventilator with BiLevel positive airway pressure (PAP); Group B, critical care ventilator with pressure support ventilation and positive end expiratory pressure (PSV + PEEP); Group C, critical care ventilator with pressure-synchronized intermittent mandatory ventilation (PSIMV) + PSV + PEEP.

PaO₂, arterial oxygen partial pressure; FiO₂, fraction of inspired oxygen; PaCO₂, arterial carbon dioxide partial pressure; P0.1, oral obstructive pressure at 0.1 s after initiation of inhalation; NA, not available (miniventilator cannot measure P0.1, PEF, RSB, R_in, R_ex or inflection point); PEF, peak expiratory flow; RSB, rapid superficial breath index; R_in, maximal inspiratory resistance; R_ex, maximal expiratory resistance.

Discussion

The findings of the present study indicate that NIPPV via critical care ventilator has a better therapeutic effect than a traditional miniventilator in patients with AECOPD. In addition, P-SIMV + PSV + PEEP had a better treatment effect than PSV + PEEP.

The high ventilation pressure provided by critical care ventilators allows the use of complex modes such as P-SIMV. P-SIMV is triggered by the patient’s positive inspiratory effort, and the critical care ventilator can generate pressure support at precisely the moment when the upper airway opens spontaneously. Traditional miniventilators are usually triggered by a posterior pressure sensor, as opposed to the more sensitive anterior flow rate sensor present in the critical care ventilator, which can decrease reaction time⁷ and has adjustable ETS and Pramp.⁸ Miniventilators use single-limb tubing, which can increase the amount of carbon dioxide rebreathing,⁹ but critical care ventilators deliver NIPPV via double-air circuits, allowing patients to breathe more smoothly and constraining carbon dioxide retention.⁹ In addition, critical care ventilators allow for rapid initial inspiration flow rate and patient–ventilator synchronization.¹⁰ Noninvasive ventilation (NIV) algorithms (available in critical care ventilators) have been shown to reduce the incidence of leak-associated asynchronies.¹¹ The ventilator can also lower respiratory work,¹² improve the ventilation/perfusion ratio, open collapsed alveoli and improve the inflection point, resulting in normalization of the respiratory rate.¹³

The use of critical care ventilator NIPPV for treating patients with AECOPD can reduce the rate of endotracheal intubation.^4,5 Early NIPPV treatment of patients with acute hypercapnic respiratory failure can reduce the rate of intubation and severe complications, improve survival and discharge rate, and is associated with low pneumonia incidence and low mortality rate.¹⁴ In addition, mechanical ventilation causes emotional stress for patients since they are unable to communicate their needs, and this stress may negatively impact ventilator weaning and survival.¹⁵ On the other hand, patients treated via NIPPV can eat, drink, talk and expectorate, and have been shown to have shorter duration of ventilation than those treated via conventional mechanical ventilation.¹⁶

In conclusion, NIPPV delivered via a critical care ventilator has a better treatment effect than miniventilator NIPPV in patients with AECOPD. The use of P-SIMV + PSV + PEEP mode provides a significantly better treatment effect than PSV + PEEP alone. Additional, large-scale studies are required to confirm the present findings.

Footnotes

Declaration of conflicting interest

The authors declare that there are no conflicts of interest.

Funding

This study was supported by grants from the National Natural Science Foundation of China (No. 81270144, 30800507, 81170071, 81100060).

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