This prospective single-blinded, randomized study was conducted over one year from November 2018 to November 2019 at Assiut University Hospital. The study was conducted in accordance with the Declaration of Helsinki. The study was approved by the Faculty of Medicine Ethics Committee, Assiut University. All the patients provided written informed consent before being enrolled in the study.
- Inclusion criteria: COPD patients aged 40–75 years with stable chronic hypercapnia at rest (partial pressure of carbon dioxide [paCO2] <50 mmHg) [6], naive to NIV, ability to provide written informed consent.
- Exclusion criteria: patients with unstable hemodynamic and respiratory conditions (e.g., recent acute heart failure, respiratory exacerbation or infection with worsening symptoms within the last month, malignancies, non-compliance with NIV (average usage of <4 h/night), Pre-existing conditions: severe bullous lung disease, pneumothorax or pneumomediastinum, pulmonary embolism), Sleep- disordered breathing (overlap syndrome, obesity hypoventilation).
Patients characteristics including (age, sex, body mass index [BMI]) smoking habit (current smoker, never smoker, ex-smoker); year of COPD diagnosis were recorded.
Spirometry (VMax 6150, SensorMedics, Yorba Linda, CA) at the time of the study were performed. Lung function parameters (FEV1, FVC, FEV1/FVC) were obtained from all patients. Also, predicted lung volumes and voluntary respiratory muscle strength values) MIP and MEP) were recorded as recommended [7,8].
Arterial blood gas (ABG) (Model 850, Chiron Diagnostics, Medfield, MA) (pH, PaCO2, PaO2, PaO2/FiO2) were performed on room air for all patients. The sample was taken during the initial assessment appointment (after study consent) to ensure that patients were clinically stable before the study.
Randomization and Treatment Settings
During an in-hospital stay of several days, eligible patients were commenced for treatment with Auto-EPAP (Group I) and (Fixed-EPAP) (Group II) during (iVAPS) [(Astral 150, ResMed Corp. iVPAPs device algorithms] treatment for 5 consecutive days. Randomization was performed (1:1) by a laboratory scientist not involved with the study using the technique of shuffled sealed envelopes containing equal numbers of each treatment arm (Figure1).
Using iVAPS with Auto-EPAP, settings were instructed to keep the range ‘open’, so the algorithm could be tested across the full range: Maximum pressure: 25–35 cmH2O, PS maximum: 15–25 cmH2O, PS minimum: 5 cmH2O, EPAP max: 15 cmH2O, EPAP minimum: 5 cmH2O, Rise time: 300 ms, AVAPS rate: 2 cmH2O/min. In both modes, the target tidal volume was set 6-8 ml/kg of the patient's ideal body weight.
NIV- iVAPS was delivered via either a nasal or oronasal mask, and the mask was carefully adjusted as part of routine clinical care.
Additional oxygen at a fixed inspiratory fraction (FiO2) was added when required with the scope to maintain the oxygen saturation (SaO2) level above 90%. (Supplementary material)
Measurements:
- Physiological variables including Exhaled VT, respiratory rate (RR), heart rate, and arterial blood gas (ABG) were recorded at baseline (T0) and then after 3 (T1) and 5 (T2) days of each consecutive period.
- Subjective assessment of dyspnea was determined using a numerical rating scale [9]. NRS consists of a scale numbered (0–10), 0='Not breathless at all' and 10= 'Breathlessness as bad as you can imagine'. A higher score represents greater symptom severity.
- Patient's comfort [10] was assessed at the end of each test period. All patients were asked to grade the comfort of the device (1-10) using the following scale: 1= severe discomfort; and 10= very good level of comfort.
- The overall Patient satisfaction level was assessed in the morning. All subjects have completed a visual analog satisfaction (VAS) questionnaire. Patients scored satisfaction (0–10) of their experience from the previous night. Questions included: (1) How well did you sleep last night? (2) How rested do you feel this morning? (3) How often did you wake during the night? (4) How uncomfortable was your iVAPS pressure? (5) Overall, how satisfied were you with your quality of sleep last night?
- The patient's compliance to iVAPS was recorded using the Encore Pro SmartCard located within the machine and included (number of hours/night of use).
Statistical analysis
Statistical package for the social sciences (SPSS), version 20 (produced by IBM SPSS Statistics for Windows, version 20; IBM Corp., Armonk, New York, USA) software was used for the collected data. Values were presented in mean and standard deviation using the Mann–Whitney U-test for comparison between the two study groups. The qualitative data were compared between the two groups using the χ2-test and the quantitative data were compared using Student's t-test. Changes in gasometrical parameters over time among the two groups were analyzed using the one-way analysis of variance test. A P-value of less than 0.05 was considered significant.