Prospective Comparative Evaluation of Noninvasive and Invasive Mechanical Ventilation in Patients of Chronic Obstructive Pulmonary Disease with Acute Respiratory Failure Type II.

INTRODUCTION: Acute respiratory failure is a potential complication of chronic obstructive pulmonary disease (COPD) that severely affects the health of the patient and may require mechanical ventilation. We compared noninvasive and invasive mechanical ventilation in COPD patients with acute respiratory failure type II to validate clinical outcome based on biochemical analysis of arterial blood gases (ABGs) and pulmonary parameters in terms of duration of mechanical ventilation, period spent in intensive care unit (ICU) and mortality.
MATERIALS AND METHODS: After approval of institutional ethical committee 100 patients were selected for randomized prospective controlled trial and divided into two groups of 50 each according to mode of mechanical ventilation. Group-I patients managed with noninvasive ventilation (NIV) Group-ll managed with invasive ventilation.
RESULTS: Demographic data between two groups were comparable. ABG parameters were better at 2 h and 6 h interval in NIV as compared to invasive ventilation (P < 0.05). The duration of ventilation and total time spent in ICU was 106±10 hours and 168±8 hours respectively in NIV group and 218 ± 12 and 280 ± 20 in invasive group. On intergroup comparison these were significantly less in noninvasive group (P < 0.05). Hospital acquired pneumonia occurred in 10% of patients in invasive group whereas no incidence of pneumonia found in noninvasive group. Mortality rate was 12% in invasive groups and 2% in noninvasive groups.
CONCLUSION: NIV leads to significant improvement in ABG and pulmonary parameters and it reduces duration of ventilation and total period of hospital stay so it can be used as an alternative to invasive ventilation as first-line treatment in COPD. Copyright:

INTRODUCTION

Acute respiratory failure is a major complication of chronic obstructive pulmonary disease (COPD) that severely affects the health of the patient with increase in hospital admission and may require mechanical ventilation. It is characterized by airflow limitation not fully reversible, progressive in nature, and usually associated with inflammatory response of lungs to noxious particles in the air, for example, bronchitis and emphysema.[1] These exacerbations increase the workload of breathing beyond the person ability leading to hyperinflation, fatigued diaphragm, intrinsic entrapping of air in lungs), increased respiratory rate and decreased tidal volume.[2] Although it is treated medically with drugs, acute respiratory failure patients require mechanical ventilator support invasive or noninvasive to reduce muscle work load.[23]

The conventional method of mechanical ventilation is associated with major complications like ventilator-associated pneumonia which can be avoided by using noninvasive ventilation (NIV).[4] It does not require tracheal intubation thus avoids complications of tracheal tube like damage to trachea and airway edema. It improves patient's comfort, maintains ciliary reflex, cough reflex and swallow reflex.[5] Moreover, the patient being conscious can communicate. Various complications are also associated with NIV as injuries to face, nose and eyes, risk of aspiration because of gastric distension and claustrophobia.[6]

It was investigated as a method of choice in COPD with respiratory failure by different authors and found decrease in intubation rate, hospital pneumonia, hospital stay, and mortality.[78910]

Although previous studies were performed to compare noninvasive and invasive method of mechanical ventilation in COPD patients with acute respiratory failure clinically but we proposed our study to validate our clinical outcome based on biochemical analysis of arterial blood gases (ABGs) (pH PaCO2, PaO2, HCO3 along with pulmonary parameters tidal volume Vt respiratory rate f, f/Vt. Considering these findings we hypothesized this study of comparative evaluation of noninvasive and invasive mechanical ventilation (IMV) in COPD patients with acute respiratory failure type II in terms of duration of mechanical ventilation, period spent in intensive care unit (ICU), overall outcome, mortality, and complications.

MATERIALS AND METHODS

After due approval of institutional ethical committee this study was conducted on 100 patients in the age group of 40 years and above having COPD with acute hypercapnoic respiratory failure type II requiring mechanical ventilation for more than 24 h after admission in ICU.

Parameters recorded in selecting patients were respiratory rate more than 25/min, dyspnea with the use of accessory muscles, tidal volume less than 5 mL.kg−1 bodyweight, moderate-to-severe hypoxemia (PaO2 <60 mm Hg), hypercapnia (PaCO2 more than 45 mmHg) acidosis (pH < 7.3).

Patients requiring immediate intubation, in coma, cardiac arrest, respiratory arrest, and shock excluded from the study. Patients were divided into two groups of 50 each. Selection of patients was made on clinical basis with even (IMV) and odd (NIV) numbers by closed envelope system only opened by intensivist not taking part in the study.

During NIV, patients were placed with head up position at 45°, Bipap was set at fresh gas flow (FiO2) to get oxygen saturation more than 90%. Face mask was used as interface between patient and Bipap machine (Philips bi-level positive airway pressure respirator). Two levels of pressures, inspiratory pressure inspiratory positive airway pressure was set at 10–25 cm of water and expiratory pressure was set at 5–7cms of water to achieve tidal volume at >5ml/kg body wt., respiratory rate 10–15/min with alarm settings. Pressure support was reduced until mechanical ventilation could be weaned off. Endotracheal intubation was done in patients when respiratory rate was >35/min, loss of consciousness (Glasgow coma scale <8, agitation, hemodynamically unstable, oxygen saturation <85 mm Hg, or Respiratory arrest). It was considered as NIV failure. Invasive ventilation group patients were intubated and put on ventilator with the following settings to achieve saturation more than 90% and PaCO2 <45 mm Hg. Assist control mode with tidal volume of 6–8 ml/kg, respiratory rate: 12–15/min and peep 5 cm of water was initiated.

On admission demographic data, for example, age, gender, length to calculate ideal body weight (for males-50+ (0.91 × length in cm-152.4) and for females-45.5+ (0.91 × length in cm-152.4) apache score, various comorbidities and prior mechanical ventilation history were recorded. Respiratory objective parameters and ABG value were recorded at the start of ventilation and after 2, 6, 12, 24 h interval and before the end of mechanical ventilation support. Duration of mechanical ventilation, time spent in ICU, treatment outcome of noninvasive and invasive ventilation, complications and mortality rate were collected. Sampling size for respective group was calculated using formula continuous outcome and equal sample sizes in both groups assuming: Alpha = 0.05 and power = 0.80 (beta = 0.20) n = 2([a + b]2 deltaSD2)/(u1 − u2)2 based on previous studies to prove our hypothesis with power analysis of 80% approximate total sample size of 100 patients were taken (50 for each group).

For statistical analysis, IBM SPSS Statistics for window version 21 was used. Categorical variables were presented as frequencies and percentage continuous variables presented as mean and standard deviation. Chi-square test was used for categorical variables and independent student t-test for quantitative variables. P < 0.05 was taken as statistically significant.

RESULTS

Demographic data showed mean age 55.5 years in noninvasive and 60.35 years IMV [Table 1]. Increased number of acute respiratory failure in COPD patients were seen in male population as compared to females though not significant (P value 0.41.). Apache score II and comorbidities in both the groups were not statistically significant (0.87). There were two patients in IMV group with a history of previous mechanical ventilation and none in the NIV group (NS).

Table 1

Demographic parameters and associated comorbidities in noninvasive ventilation versus invasive mechanical ventilation group in chronic obstructive pulmonary disease patients

Study population characteristics	Group I NIV (n=50)	Group II IMV (n=50)	Statistical difference between groups (P)
Age (years), mean±SD	55.5±15	62.5±12	0.21
Sex
Male	35	30	0.22
Female	15	20	0.41
Ideal body weight (male)	65	62	0.48
Ideal body weight (female)	50	52	0.46
APACHE II score	18	24	0.34
Comorbidities
Hypertension	34	36	0.87
Ischaemic heart disease	4	6	0.74
Diabetes mellitus	8	6	0.64
Chronic renal disease	2	4	0.68
Prior MV application, n (%)	0	2	0.49

Data given as mean values. SD: Standard deviation, NIV: Noninvasive ventilation, MV: mechanical ventilation, IMV: Invasive MV

In NIV group respiratory parameters, i.e. f/Vt ratio started improving at 2 h and were much better at 6 h intervals as compared to IMV. However at 12 h, 24 h, and outcome results were almost equal and comparable as shown in Table 2.

Table 2

Noninvasive versus invasive ventilation based on respiratory parameters

Duration of ventilation	Vt E (ml)	F (n/min)	F/Vt	P (F/Vt) comparison with baseline
At start of ventilation
NIV	350	30	30/300=100
IMV	320	32	32/320=100
P			>0.05
After 2 h
NIV	380	20	20/380=52.64	<0.05
IMV	350	26	26/350=70.40	>0.05
P			<0.05	<0.0.05
After 6 h
NIV	400	18	18/400=45	<0.03
IMV	380	22	22/380=57.80	<0.05
P			<0.05	<0.05
After 12 h
NIV	450	16	16/450=35.55	<0.05
IMV	420	16	16/420=38.09	<0.05
P			>0.05	>0.05
After 24 h
NIV	470	15	15/470=31.90	<0.05
IMV	480	16	16/480=33.33	<0.05
P			>0.05	>0.05
Outcome
NIV	480	15	15/480=31.25	<0.05
IMV	480	16	16/480=33.33	<0.05
P			>0.05	>0.05

NIV: Noninvasive ventilation, MV=Mechanical ventilation, IMV=Invasive MV

There occurred significant improvement in PaO2 at 2 h and 6 h interval in NIV group. We also noticed increased oxygen saturation more than 92% and improved P/F ratio at 2 h interval in NIV group as shown in Figure 1. We also noticed significant reduction in PaCO2 and improvement in pH at 2 h and 6 h interval in NIV group as compared to IMV [Figure 2] group. However, 12 h, 24 h interval and outcome results of ABG analysis were almost same in both the groups as shown in Table 3.

Figure 1

Variation of PaO2/FiO2 with mechanical ventilation

Figure 2

Variation of PaCO2 and pH with mechanical ventilation

Table 3

Noninvasive versus invasive ventilation based on arterial blood gas

Parameters of arterial blood gas	pH	PaO2 (k Pa)	PaCO2 (k Pa)	PaO2/FiO2 mean±SD	HCO3	SatO2 (%)
At start of ventilation
NIV	7.29	60	68	130±22	28	88
IMV	7.25	58	70	128±24	30	86
P	>0.05	>0.05	>0.05	>0.05	>0.05	>0.05
2 h
NIV	7.35	90	50	220±54	27	94
IMV	7.29	70	60	210±40	28	92
P	<0.05	<0.05	<0.05	>0.05	>0.05	>0.05
6 h
NIV	7.37	95	45	260±44	26	97
IMV	7.31	90	55	220±50	27	92
P	<0.05	<0.05	<0.05	<0.05	>0.05	<0.05
12 h
NIV	7.40	96	42	280±54	24.	97
IMV	7.35	95	45	260±44	24.5	95
P	>0.05	0.05>	>0.05	>0.05	>0.05	>0.05
24 h
NIV	7.40	97	42	280±44	23	97
IMV	7.35	96	44	260±50	20	97
P	>0.05	>0.05	>0.05	>0.05	>0.05	>0.05
Outcome
NIV	7.40	98	40	340±26	22	98
IMV	7.40	97	42	320±16	24	97
P	>0.05	>0.05	>0.05	>0.05	>0.05	>0.05

NIV: Noninvasive ventilation, SD: Standard deviation, MV=Mechanical ventilation, IMV=Invasive MV

In terms of outcome, the mean duration of NIV was 106 ± 10 h while in IMV, 218 ± 12 h was recorded and this was significantly less in NIV group (P < 0. 05) as shown in Table 4. Total time spent in ICU 168 ± 08 h was also significantly less in NIV group as compared to280 ± 20 h in invasive ventilation. Success rate was 92% in NIV method and78% in IMV grouP value < 0.05. Ventilator associated pneumonia incidence was 10% in IMV ventilation. However, no case of pneumonia was reported in NIV ventilation. ICU mortality was 12% in invasive group and 2% in NIV group. Six percent of the patients in NIV group have to be intubated and considered as NIV failure. Tracheostomy was done in 5 cases of IMV (10%).

Table 4

Comparisons of noninvasive mechanical ventilation and invasive mechanical ventilation for patients with chronic obstructive pulmonary disease based on outcome

MV outcome	NIV (n=50)	IMV (n=50)	Statistical difference between groups P
Duration of MV (h), mean±SD	106±10	218±12	<0.05
Duration in ICU (h), mean±SD	168±8	280±20	<0.05
Success rate, n (%)	92	78	<0.05
Need for intubation, n (%)	6	100	<0.001
Ventilator associated pneumonia, n (%)	0	10	<0.05
Tracheostomy, n (%)	0	10	<0.05
Mortality, n (%)	2	12	<0.05

Data given as mean±SD and percentage. NIV=Noninvasive ventilation, SD=Standard deviation, MV=Mechanical ventilation, IMV=Invasive MV, ICU=Intensive care unit

DISCUSSION

In our study, we found that NIV was associated with lower mortality, shorter duration of mechanical ventilation, and decreased time of hospital stay as compared with IMV. We also found that PACO2 levels and shallow respiration index parameter improved better with NIV as compared to IMV within 24 h.

Our study included 100 patients of COPD with acute respiratory failure type II and divided into two groups of 50 patients each put on either noninvasive or IMV.

Demographic data, Apache score II, comorbidities, and prior intubation were statistically not significant in both groups. There were more male patients in both the groups. This is in accordance with the literature in which it is mentioned that COPD is more common in males.[11]

On the basis of pulmonary mechanics, we found a significant reduction of respiratory rate and improved tidal volume in NIV group resulting in better rapid shallow respiration index parameter within 6 h [Table 2]. In addition, there was significant decrease in arterial blood levels of PaCO2 and improved PaO2 in NIV group [Table 3]. The results of our study were in accordance to the study done by Matic et al. where they found significant improvement in PaCO2 in NIV group as compared to invasive ventilation.[12] Also in the study done by Plant et al. they found rapid improvement in pH within 1 h and decreased respiratory rate after 4 h of NIV.[13] In another study done by Antonelli et al. where they compared NIV and invasive ventilation found that similar initial change in PF ratio in both the groups and also change in PaCO2 was similar in both the groups. Thus, they concluded that NIV was as effective as IMV in improving gas exchange.[14]

Similarly, Bott et al. showed improvement in pH, breathlessness, decreased PaCO2 during NIV treatment. They also observed reduced mortality (10%) in NIV as compared to the control group (30%). Reason for lower mortality may be due to early intervention of NIV mechanical ventilation in acute exacerbations of COPD.[15]

Our results are different from the study done by Devi et al. They found better improvement in PaCO2 in IMV whereas better improvement in PaO2 in NIV group over 24 h.[16] In an another study done by Amri Maleh et al. where they compared the therapeutic efficacy and outcome of NIV and IMV in ARF due to COPD patients admitted to ICU found that though within 24 h of treatment better improvement of respiratory rate, heart rate, pH, PaCO2, PaO2 in IMV group as compared to NIV group. Their results were different from our study but they found that the two methods were comparable in the treatment of ARF and NIV was effective in prevention of intubation and thus avoiding the various complications associated with intubation.[17]

In our study, mean duration of ventilation was significantly less in NIV group 106 ± 10 h (4.41 days) when compared with IMV 9 days (218 ± 12 h) and time spent in ICU was also significantly less in noninvasive than invasive ventilation (168 ± 08 vs. 280 ± 20 h) as shown in Table 4. Success rate was 92% in NIV as 6% patients have to be intubated and this was considered as NIV failure with mortality rate 2% while successful outcome in IMV was 78% as 10% patients have to be tracheostomised and mortality rate was 12%. Our results were similar to the study done by Ali O Abdel Aziz et al. where they studied the effectiveness of noninvasive positive pressure ventilation in hypercapnoic patients of COPD and found success rate of 94%. Success rate was similar to our study. Failure rate was related to older age group patients, septicemia, and comorbidities like cardiovascular disease.[18]

Squadrone et al. compared NIV with IMV in COPD with severe acute respiratory failure and reported high incidence of failure during NIV. However, they found that delay in intubation was not deleterious in patients who failed NIV and observed better outcome in patients who avoided intubation.[19] Mortality and length of stay was reduced in noninvasive positive pressure ventilation in their study which was comparable with our study. Similar results were reported by Peter et al. in which they found decrease mortality and less requirement of ventilation in NIV group in ARF especially in COPD patients.[20]

In contrast to our study, N Ambrosino et al. in their study on 59 patients of ARF found success rate of NIV 78% and overall mortality 8.5%. The failure rate more in patient with higher apache score (>24). They also found decrease in duration of mechanical ventilation during NIV similar to our study.[21]

Meduri et al. advocated NIV as first-line treatment in hypercapnoic and hypoxemic respiratory failure. Non-IMV was effective and blood gas parameters improved in 80%, intubation was avoided in 65% and mortality rate reduced from 43% to 16%. Survival rate was 93% in noninvasive positive-pressure ventilation while it was 79% in IMV. These results were comparable with our study (survival rate 92% vs. 78%).[22]

Similarly, Plant et al. conducted a study and recommended early use of NIV for acute exacerbations of COPD in general wards. They found NIV results in decreased need of IMV and hospital mortality.[13]

In an another study conducted by Matic et al. where they compared invasive and non- IMV in patients of COPD with acute respiratory failure with 38 patients in NIV group and 34 patients in IMV found less duration of mechanical ventilation (102:187) and time spent in ICU (127:233) hours as compared to IMV.[12]

Our results were in contrast to the study done by Conti et al. who compared noninvasive positive pressure ventilation with conventional mechanical ventilation after failure of medical treatment in ICU and had found no difference in the number of days of mechanical ventilation, overall complications and ICU mortality.[23]

Similarly, Venkatram et al. had shown NIV as an effective method in patients of acute respiratory failure with COPD. NIV failure rate was 5.45% and its use was associated with reduced duration of mechanical ventilation, decreased need of endotracheal intubation and less hospital stay and mortality.[24]

In terms of complications, there was no case of hospital-acquired pneumonia observed in NIV group while there was 10% incidence in IMV group. Results were similar to the studies where they compared NIV with IMV in patients with severe acute respiratory failure who failed standard treatment and found that NIV had lowered hospital-acquired pneumonia but it did not reduce mortality or length of stay and had a high rate of NIV failure in their study in contrast to our study.[1225]

In terms of other minor complications, the rate was lower in NIV group as it avoids intubation and hence upper airway remains intact thus preserving airway defense mechanisms. Furthermore, trauma of the teeth, hypopharynx, esophagus, larynx, and trachea could thus be avoided by the application of NIV. It is cost-effective method easy to use, requiring no special expertise, with patient comfort and acceptance easy to wean off from ventilator support.

The strength of our study was that our data comprised of both clinical and laboratory data whereas limitations of our study were that the study sample size was smaller, and data regarding survival rate of the patients post discharge could not be recorded we concluded that NIV resulted in better improvement in respiratory parameters and decrease duration of ventilation and hospital stay as well as less complications and mortality. It should be applied in the early phase of acute respiratory failure in CO as an alternative to Invasive ventilation.

CONCLUSION

Our study shows that early initiation of noninvasive positive pressure ventilation leads to improved patient outcome in terms of pH value, PaO2, reduced respiratory rate and PaCO2 level. It should be used as an alternative to conventional IMV to avoid complications of intubation. It should be used as first-line treatment of acute respiratory failure type II (hypercapnic failure) in COPD patients. It is cost-effective method.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.