# Effect of Noninvasive Positive Pressure Ventilation on Prognosis and Blood Gas Level in COPD Patients Complicated with Respiratory Failure

Authors: Xiaoqing Xiong; Wensheng Yuan
Journal: Evidence-Based Complementary and Alternative Medicine
 (2022)

---

## Abstract

Chronic obstructive pulmonary disease (COPD) is a respiratory disease caused by chronic bronchitis, which seriously threatens the life safety of patients. Noninvasive positive pressure ventilation (NIPPV) has great advantages in its treatment. Here, we explore the effect of NIPPV on prognosis and blood gas level in COPD patients complicated with respiratory failure (RF). A case control study was retrospectively analyzed, where 36 COPD patients with RF were regarded as the regular group to carry on the routine treatment, and 42 patients were assigned to the research group to carry out the routine treatment plus NIPPV. The monofactorial analysis showed that the overall response rate, forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and FEV1/FVC in the research group were higher than those in the regular group, while partial pressure of arterial carbondioxide (PaCO2), posttreatment endotracheal intubation (EI), length of stay (LOS), tumor necrosis factor (TNF-α), interleukin (IL)-6, IL-1β, Acute Physiology and Chronic Health Evaluation (APACHE) II score, and modified Medical Research Council (mMRC) scores in the research group were lower than those in the regular group. These results indicated that NIPPV can improve the curative effect of emergency medicine patients with RF, improve BG level and PF, reduce inflammation, and facilitate patient’s recovery.


---

## Body

## 1. Introduction

COPD is characterized by its high prevalence, disability, and mortality, which was a great challenge for the public health [1]. COPD will become the 3rd in global disease mortality rate by 2030, as indicated by the World Health Organization [2]. Compared with the other diseases, COPD has a higher mortality rate, mainly due to its common occurrence in the elderly population and the accompanying acute respiratory failure (RF), which increases the treatment difficulty [3]. Currently, the mainstays for treating COPD complicated with RF are anti-infection, bronchial dilation, and correction of water-electrolyte disturbance, which can effectively control the patient’s condition, but does not improve the clinical symptoms. Invasive mechanical ventilation is often applied clinically with the purpose of enhancing the therapeutic effect on patients. The technique involves creating an artificial airway by inserting a catheter through the patient’s throat so that the airway can be in a relatively unobstructed state. However, when establishing an artificial airway, it may cause certain damage to the human body, such as the lung injury caused by aspiration, ventilator-associated pneumonia, and mental illness due to long-term use of analgesic drugs, which will affect the follow-up treatment effect to varying degrees [4]. In recent years, noninvasive positive pressure ventilation (NIPPV) technology has increasingly evolved. Unlike traditional invasive ventilation, NIPPV is given through an oral-nasal mask, nasal mask or full mask, or helmet connected to the ventilator, without the need for an artificial airway, which can avoid damage to the physiological function of the upper respiratory tract and reduce trauma [5, 6]. It is shown that NIPPV has been widely used in patients with neonatal respiratory distress syndrome, premature infants, muscular dystrophy, and other patient populations, which can not only effectively reduce bronchopulmonary dysplasia and the need for tracheal intubation ventilation but also has significant benefits in improving the patients’ lung defense [7–9]. In this study, COPD patients with RF were divided into the regular group and research group, which were treated with regular treatment and regular treatment + NIPPV, respectively, to evaluate the application value of NIPPV, as well as its influence on the blood gas (BG) level, pulmonary function (PF), and serum inflammatory cytokines (ICs).


## 2. Data and Methods

### 2.1. Research Subjects

From December 2019 to September 2021, 78 COPD patients complicated with RF admitted to the Department of Emergency Medicine of our hospital were retrospectively analyzed. Inclusion criteria included meeting the diagnostic criteria of COPD issued by the Respiratory Society of Chinese Medical Association after clinical examination; acute onset, with manifestations of dyspnea, cough, and expectoration, increased sputum volume or purulent sputum; complicated with RF symptoms; age <80; and complete medical records during the clinical treatment. Exclusion criteria included severe neurological disorders and mental retardation, severe pneumonia, bronchiectasis, tuberculosis, pulmonary malignancy, and other respiratory malignant diseases. Contraindications to the treatment used in this study: severe cardio-cerebrovascular diseases (acute myocardial infarction, stroke, etc.) occurring within 6 months before the enrollment, hospital referrals, and death during the treatment. Informed consent was signed by patients and their families, and the research protocol was ethically ratified by our hospital.


### 2.2. Treatment

The regular group (n = 36) received routine treatment. The medical staff gave all the enrolled patients anti-infection, bronchiectasis, sputum suction, phlegm-dispelling, electrolyte disturbance adjustment, and glucocorticoid treatment. On this basis, patients in the regular group were given nasal catheters for oxygen inhalation therapy, with oxygen flow rate maintained at 2-3 L/min and the inhaled oxygen concentration at 40%–50%.The research group (n = 42) received routine treatment + NIPPV, with the Bipap Vision noninvasive ventilator supplied by Respironics Inc. Before the treatment, the patient’s head was raised about 30°, and a mask matching the patient’s size was selected. The BiPAP was adjusted to the pressure support ventilation mode, with the heart rate maintained at 14–20 beats/min, the initial IPAP at 6–8 cm H2O, and the EPAP at 3–5 cm H2O [10]. Then, the IPAP level was slowly increased within the range of 16–20 cm H2O. Patients’ blood oxygen saturation (SpO2) was observed closely. When SpO2 >90%, the tidal volume was adjusted to 7–10 mL/kg accordingly, and the ventilation duration was 4–6 h/d, for 1–5 days. During the treatment period, the main attention was paid to extending the ventilation time as much as possible when using positive pressure ventilation for the first time and ensuring that the ventilation treatment time exceeded 3 hours. In addition, the administration concentration and ventilation time were adjusted reasonably according to the specific symptoms of patients and their changes in SpO2.


### 2.3. Endpoints

BG and PF indexes of the two cohorts were compared before and 1 week after treatment. PaO2, PaCO2, and CaO2 were measured by the Bayer Rapidlab 840 BG analyzer. Strenuous exercise was prohibited within 2 hours before PF examination. FEV1, FVC, and FEV1/FVC (%) were detected using FGC-A + PF tester.Three milliliters of peripheral venous blood were extracted from patients in both cohorts before and 1 week after treatment and centrifuged (000×g, 4°C) for 15 min to collect serum for the determination of ICs TNF-α, IL-6, and IL-1β using ELISA which were supplied by Wuhan Boster Biological Technology, Ltd.The clinical efficacy was also compared. Markedly effective: clinical symptoms and related signs such as moist rales in the lungs disappeared; effective: clinical symptoms were better than before treatment, and the related signs such as moist rales in the lungs were reduced to less than 50%; ineffective: the above clinical symptoms and related signs showed no obvious improvement and failed to meet the effective standards or even with deterioration.The disease severity before and 1 week after treatment of patients were scored by the APACHE II score [11] (score range: 0–71), with higher scores suggesting more serious illness. In addition, they were scored for the extent of dyspnea using the mMRC score [12] (score range: 0–4), with higher scores indicating more severe dyspnea. The flow chart of this study is shown in Figure 1.Figure 1
Flowchart.


### 2.4. Statistical Processing

Data processing and visualization employed SPSS 19.0 (Shanghai Yijun Information Technology Co., Ltd.) and GraphPad Prism 6, respectively. The comparison of counting data in this study was finished using the chi-square test. An independentt-test was adopted for measurement data comparison, and paired t-test was adopted to compare the results before and after treatment. For multigroup comparisons of measurement data, single-factor analysis was used, and then the post hoc test (Tukey HSD method) was used to verify the correctness of statistical values. P<0.05 represented the significance level.


## 2.1. Research Subjects

From December 2019 to September 2021, 78 COPD patients complicated with RF admitted to the Department of Emergency Medicine of our hospital were retrospectively analyzed. Inclusion criteria included meeting the diagnostic criteria of COPD issued by the Respiratory Society of Chinese Medical Association after clinical examination; acute onset, with manifestations of dyspnea, cough, and expectoration, increased sputum volume or purulent sputum; complicated with RF symptoms; age <80; and complete medical records during the clinical treatment. Exclusion criteria included severe neurological disorders and mental retardation, severe pneumonia, bronchiectasis, tuberculosis, pulmonary malignancy, and other respiratory malignant diseases. Contraindications to the treatment used in this study: severe cardio-cerebrovascular diseases (acute myocardial infarction, stroke, etc.) occurring within 6 months before the enrollment, hospital referrals, and death during the treatment. Informed consent was signed by patients and their families, and the research protocol was ethically ratified by our hospital.


## 2.2. Treatment

The regular group (n = 36) received routine treatment. The medical staff gave all the enrolled patients anti-infection, bronchiectasis, sputum suction, phlegm-dispelling, electrolyte disturbance adjustment, and glucocorticoid treatment. On this basis, patients in the regular group were given nasal catheters for oxygen inhalation therapy, with oxygen flow rate maintained at 2-3 L/min and the inhaled oxygen concentration at 40%–50%.The research group (n = 42) received routine treatment + NIPPV, with the Bipap Vision noninvasive ventilator supplied by Respironics Inc. Before the treatment, the patient’s head was raised about 30°, and a mask matching the patient’s size was selected. The BiPAP was adjusted to the pressure support ventilation mode, with the heart rate maintained at 14–20 beats/min, the initial IPAP at 6–8 cm H2O, and the EPAP at 3–5 cm H2O [10]. Then, the IPAP level was slowly increased within the range of 16–20 cm H2O. Patients’ blood oxygen saturation (SpO2) was observed closely. When SpO2 >90%, the tidal volume was adjusted to 7–10 mL/kg accordingly, and the ventilation duration was 4–6 h/d, for 1–5 days. During the treatment period, the main attention was paid to extending the ventilation time as much as possible when using positive pressure ventilation for the first time and ensuring that the ventilation treatment time exceeded 3 hours. In addition, the administration concentration and ventilation time were adjusted reasonably according to the specific symptoms of patients and their changes in SpO2.


## 2.3. Endpoints

BG and PF indexes of the two cohorts were compared before and 1 week after treatment. PaO2, PaCO2, and CaO2 were measured by the Bayer Rapidlab 840 BG analyzer. Strenuous exercise was prohibited within 2 hours before PF examination. FEV1, FVC, and FEV1/FVC (%) were detected using FGC-A + PF tester.Three milliliters of peripheral venous blood were extracted from patients in both cohorts before and 1 week after treatment and centrifuged (000×g, 4°C) for 15 min to collect serum for the determination of ICs TNF-α, IL-6, and IL-1β using ELISA which were supplied by Wuhan Boster Biological Technology, Ltd.The clinical efficacy was also compared. Markedly effective: clinical symptoms and related signs such as moist rales in the lungs disappeared; effective: clinical symptoms were better than before treatment, and the related signs such as moist rales in the lungs were reduced to less than 50%; ineffective: the above clinical symptoms and related signs showed no obvious improvement and failed to meet the effective standards or even with deterioration.The disease severity before and 1 week after treatment of patients were scored by the APACHE II score [11] (score range: 0–71), with higher scores suggesting more serious illness. In addition, they were scored for the extent of dyspnea using the mMRC score [12] (score range: 0–4), with higher scores indicating more severe dyspnea. The flow chart of this study is shown in Figure 1.Figure 1
Flowchart.


## 2.4. Statistical Processing

Data processing and visualization employed SPSS 19.0 (Shanghai Yijun Information Technology Co., Ltd.) and GraphPad Prism 6, respectively. The comparison of counting data in this study was finished using the chi-square test. An independentt-test was adopted for measurement data comparison, and paired t-test was adopted to compare the results before and after treatment. For multigroup comparisons of measurement data, single-factor analysis was used, and then the post hoc test (Tukey HSD method) was used to verify the correctness of statistical values. P<0.05 represented the significance level.


## 3. Results

### 3.1. Comparison of General Data

As shown in Table1, age, BMI, course of COPD, hypertension, diabetes mellitus, sex, smoking history, and other general data of the two cohorts showed no statistical significance (P>0.05).Table 1
Comparison of general data.
GroupsRegular group (n = 36)Research group (n = 42)χ2/tPAge (years old)65.31 ± 7.5564.19 ± 8.410.6140.541BMI (kg/m2)23.55 ± 1.5522.91 ± 1.701.7260.088Course of COPD (years)8.97 ± 3.089.83 ± 3.141.2170.228Hypertension2.0690.150With14 (38.89)10 (23.81)Without22 (61.11)32 (76.19)Diabetes mellitus0.0940.759With10 (27.78)13 (30.95)Without26 (72.22)29 (69.06)Sex0.2900.590Female21 (58.33)27 (64.29)Male15 (41.67)15 (35.71)Smoking history0.0790.779Yes20 (55.56)22 (50.38)No16 (44.44)20 (47.62)


### 3.2. Comparison of BG Indices

Figure2 showed that there was no distinct difference in PaCO2, PaO2, and CaO2 between groups before treatment (P>0.05), while PaCO2 decreased, and PaO2 and CaO2 increased in both cohorts (P<0.05) after treatment, with more evident changes in the above BG indices in the research group (P<0.05).Figure 2
Comparison of BG analyzer results. Comparison of PaCO2 (a), PaO2 (b), and CaO2 (c). Note. ∗ represents P<0.05 compared with the same group before treatment; # represents P<0.05 compared with the regular group.
(a)(b)(c)


### 3.3. Comparison of PF Indices

According to the results of the BG analyzer, FEV1, FVC, and FEV1/FVC differed insignificantly between two cohorts before treatment (P>0.05), while the above PF indices elevated markedly in both cohorts after treatment (P<0.05), with more obvious increases in the research group (P<0.05) (Figure 3).Figure 3
Blood gas analyzer results. Comparison of FEV1 (a), FVC (b), and FEV1/FVC (c). Note:∗ and # have the same meaning as in Figure 2.
(a)(b)(c)


### 3.4. Comparison of Serum ICs

There was no evident difference between groups in TNF-α, IL-6, and IL-1β before treatment, as indicated by ELISA results (P>0.05). After treatment, the above ICs reduced remarkably in both cohorts (P<0.05) and were lower in the research group than that in the regular group (P<0.05), as shown in Figure 4.Figure 4
ELISA results. Comparison of TNF-α levels (a), IL-6 levels (b), and IL-1β levels (c). Note: ∗ and # have the same meaning as in Figure 2.
(a)(b)(c)


### 3.5. Comparison of APACHE II and mMRC Scores

Figure5 shows that the APACHE II and mMRC scores differed insignificantly between groups before treatment (P>0.05), while declined notably in both cohorts after treatment, with more reductions in the research group (P<0.05).Figure 5
Comparison of APACHE II and mMRC scores. Comparison of APACHE II scores (a) and MMRC scores (b). Note:∗ and # have the same meaning as in Figure 2.
(a)(b)


### 3.6. Comparison of Clinical Efficacy

In the regular group, the cases in markedly effective, effective, and ineffective were 12 (33.33%), 18 (50.00%), and 6 (16.67%), respectively, and the overall response rate (ORR) was 83.33%. In the research group, the cases in markedly effective, effective, and ineffective were 22 (66.67%), 19 (45.24%), and 1 (2.38%), respectively, with an ORR of 97.62% which was obviously better compared to the regular group (P<0.05), as shown in Table 2.Table 2
Comparison of clinical efficacy (n (%)).
GroupsMarkedly effectiveEffectiveIneffectiveTotal effective rateRegular group (n = 36)12 (33.33)18 (50.00)6 (16.67)30 (83.33)Research group (n = 42)22 (66.67)19 (45.24)1 (2.38)41 (97.62)χ2———4.843P———0.028


### 3.7. Comparison of Endotracheal Intubation (EI) Rate, LOS, and Mortality

With equivalent 6-month mortality (P>0.05), the research group was better than the regular group with markedly lower EI rate and shorter LOS (P<0.05) (Table 3).Table 3
Comparison of endotracheal intubation rate, hospitalization time, and mortality.
GroupsTracheal intubationLength of stay (d)MortalityRegular group (n = 36)10 (27.78)20.78 ± 5.035 (16.67)Research group (n = 42)4 (9.52)15.12 ± 4.031 (2.38)χ2/t4.3865.5163.615P0.036<0.0010.057


## 3.1. Comparison of General Data

As shown in Table1, age, BMI, course of COPD, hypertension, diabetes mellitus, sex, smoking history, and other general data of the two cohorts showed no statistical significance (P>0.05).Table 1
Comparison of general data.
GroupsRegular group (n = 36)Research group (n = 42)χ2/tPAge (years old)65.31 ± 7.5564.19 ± 8.410.6140.541BMI (kg/m2)23.55 ± 1.5522.91 ± 1.701.7260.088Course of COPD (years)8.97 ± 3.089.83 ± 3.141.2170.228Hypertension2.0690.150With14 (38.89)10 (23.81)Without22 (61.11)32 (76.19)Diabetes mellitus0.0940.759With10 (27.78)13 (30.95)Without26 (72.22)29 (69.06)Sex0.2900.590Female21 (58.33)27 (64.29)Male15 (41.67)15 (35.71)Smoking history0.0790.779Yes20 (55.56)22 (50.38)No16 (44.44)20 (47.62)


## 3.2. Comparison of BG Indices

Figure2 showed that there was no distinct difference in PaCO2, PaO2, and CaO2 between groups before treatment (P>0.05), while PaCO2 decreased, and PaO2 and CaO2 increased in both cohorts (P<0.05) after treatment, with more evident changes in the above BG indices in the research group (P<0.05).Figure 2
Comparison of BG analyzer results. Comparison of PaCO2 (a), PaO2 (b), and CaO2 (c). Note. ∗ represents P<0.05 compared with the same group before treatment; # represents P<0.05 compared with the regular group.
(a)(b)(c)


## 3.3. Comparison of PF Indices

According to the results of the BG analyzer, FEV1, FVC, and FEV1/FVC differed insignificantly between two cohorts before treatment (P>0.05), while the above PF indices elevated markedly in both cohorts after treatment (P<0.05), with more obvious increases in the research group (P<0.05) (Figure 3).Figure 3
Blood gas analyzer results. Comparison of FEV1 (a), FVC (b), and FEV1/FVC (c). Note:∗ and # have the same meaning as in Figure 2.
(a)(b)(c)


## 3.4. Comparison of Serum ICs

There was no evident difference between groups in TNF-α, IL-6, and IL-1β before treatment, as indicated by ELISA results (P>0.05). After treatment, the above ICs reduced remarkably in both cohorts (P<0.05) and were lower in the research group than that in the regular group (P<0.05), as shown in Figure 4.Figure 4
ELISA results. Comparison of TNF-α levels (a), IL-6 levels (b), and IL-1β levels (c). Note: ∗ and # have the same meaning as in Figure 2.
(a)(b)(c)


## 3.5. Comparison of APACHE II and mMRC Scores

Figure5 shows that the APACHE II and mMRC scores differed insignificantly between groups before treatment (P>0.05), while declined notably in both cohorts after treatment, with more reductions in the research group (P<0.05).Figure 5
Comparison of APACHE II and mMRC scores. Comparison of APACHE II scores (a) and MMRC scores (b). Note:∗ and # have the same meaning as in Figure 2.
(a)(b)


## 3.6. Comparison of Clinical Efficacy

In the regular group, the cases in markedly effective, effective, and ineffective were 12 (33.33%), 18 (50.00%), and 6 (16.67%), respectively, and the overall response rate (ORR) was 83.33%. In the research group, the cases in markedly effective, effective, and ineffective were 22 (66.67%), 19 (45.24%), and 1 (2.38%), respectively, with an ORR of 97.62% which was obviously better compared to the regular group (P<0.05), as shown in Table 2.Table 2
Comparison of clinical efficacy (n (%)).
GroupsMarkedly effectiveEffectiveIneffectiveTotal effective rateRegular group (n = 36)12 (33.33)18 (50.00)6 (16.67)30 (83.33)Research group (n = 42)22 (66.67)19 (45.24)1 (2.38)41 (97.62)χ2———4.843P———0.028


## 3.7. Comparison of Endotracheal Intubation (EI) Rate, LOS, and Mortality

With equivalent 6-month mortality (P>0.05), the research group was better than the regular group with markedly lower EI rate and shorter LOS (P<0.05) (Table 3).Table 3
Comparison of endotracheal intubation rate, hospitalization time, and mortality.
GroupsTracheal intubationLength of stay (d)MortalityRegular group (n = 36)10 (27.78)20.78 ± 5.035 (16.67)Research group (n = 42)4 (9.52)15.12 ± 4.031 (2.38)χ2/t4.3865.5163.615P0.036<0.0010.057


## 4. Discussion

With an increasing incidence, COPD is becoming one of the serious risk factors for global mortality [13]. Restoring the respiratory function of patients was the first in the treatment of COPD patients with RF [14]. Currently, mechanical ventilation is one of the main treatments for such patients, which can be divided into two types, invasive and noninvasive. Compared with invasive ventilation, noninvasive ventilation can not only ensure ventilation effect but also reduce ventilator-related complications, which has a better application value [15, 16].Noninvasive ventilator ventilation includes CPAP ventilation and external CNPV, among which the former is widely used in clinics. Through dual horizontal channels, CPAP provides higher inspiratory pressure during inhalation to help patients overcome airway resistance [17]. Our experimental results identified lower PaCO2, higher PaO2, and CaO2, as well as higher FEV1, FVC, and FEV1/FVC in the research group compared with the regular group after treatment, indicating that NIPPV can effectively improve the BG level and PF of COPD patients with RF based on routine treatment. The reason may be that while reducing the influence of airway resistance and energy consumption and promoting patients to recover spontaneous breathing function, NIPPV can increase ventilation volume and ventilation/blood flow ratio, maintain bronchiectasis, and strengthen air circulation to correct hypoxia and carbon dioxide retention, thus effectively improving BG indexes and PF [18, 19]. In the study of Zheng et al. [20], NIPPV also has a certain protective effect on BG analysis indexes of children after congenital heart disease surgery, mainly manifesting in significantly reduced PaCO2 and obviously increased PaO2 within 48 hours, similar to our study results. Chen et al. [21] also pointed out in their report that NIPPV intervention significantly improved the PF of patients with severe stable COPD, which was consistent with our findings. Then, intergroup comparisons were made in terms of disease severity, dyspnea, treatment efficiency, EI rate, LOS, and mortality. The results determined lower posttreatment APACHE II and mMRC scores, EI rate, shorter LOS, and a higher ORR in the research group compared to the regular group, all of which are closely associated with the improvement of BG level and PF by NIPPV. Previous studies have shown that a high APACHE II score is often significantly associated with poor prognosis in COPD patients with RF, suggesting that a lower APACHE II level under NIPPV intervention may be beneficial to prolonging the survival of patients [22, 23]. Zhan et al. [24] reported that NIPPV also significantly reduced intubation rate and inhospital mortality in patients with the acute lung injury compared with high-concentration oxygen therapy.COPD patients have chronic pulmonary vascular inflammation, which can lead to remodeling of airway structure and further limited respiratory airflow, eventually endangering patients’ life and health [25]. Studies have indicated that ICs play a critical role in the progression of COPD complicated with RF. When the body’s inflammatory cells are activated, the body releases mass inflammatory mediators, which destroy the normal structure of the lungs, induce emphysema, edema, excessive mucus secretion, airway stenosis, and increased airflow resistance, resulting in poor outcomes in patients [26, 27]. TNF-α is one of the most extensively explored cytokines in COPD, with its serum concentration positively correlated with the degree of airway obstruction and COPD severity [28]. IL-6 is a pleiotropic cytokine that acts as a proinflammatory mediator and an inducer of acute-phase responses, and its serum level has a positive connection with the acute exacerbation of COPD [29]. IL-1β is a proinflammatory cytokine closely related to inflammation, and plasma IL-1β is significantly associated with the risk of COPD exacerbation [30]. This study found notably reduced serum TNF-α, IL-6, and IL-1β in these two cohorts after treatment, with more significant reductions in the research group. It suggests that NIPPV can effectively reduce the inflammation degree of COPD patients with RF on the basis of routine treatment. In the study of Dreher et al. [31], NIPPV can inhibit the systemic inflammatory response in patients with COPD by relieving cardiovascular inflammation, which is similar to our results.The main contribution of this study is to reveal the clinical effectiveness of NIPPV in the treatment of COPD combined with RF from multiple dimensions, such as BG, PF, serum ICs, APACHE II, mMRC scores, clinical efficacy, tracheal intubation rate, LOS, and mortality, demonstrating that NIPPV can not only improve BG and PF of patients but also significantly reduce inflammatory responses and improve patient prognosis, providing a reliable basis and a new direction for the selection of clinical treatment for such patients. This study still shows certain room for improvement. First, the influence of NIPPV on patients’ longer-term prognosis cannot be determined due to the short follow-up time. Second, the subjects enrolled are limited, and all come from the same hospital, which may have biased the results to a certain extent. Finally, we did not include the treatment costs of patients, nor did we take into account the medical burden brought by NIPPV. All of these should be considered in future randomized clinical trials.Collectively, based on the conventional treatment scheme, NIPPV is effective in treating COPD complicated with RF, as it can effectively improve patients’ BG level, improve PF, reduce inflammation, and promote patients’ recovery, which can be popularized and applied in clinics.



---

*Source: 3089227-2022-08-05.xml*