Effect of Body Mass Index on Noninvasive Ventilation Pressures

Abstract

Background:

A person is considered overweight when their body mass index (BMI) is >25 kg/m² and obese when >30 kg/m². Noninvasive ventilation (NIV) by mask has become a popular method of treating respiratory distress and acute respiratory failure. Similar to what is being seen in mechanical ventilation with an increased need for positive end expiratory pressure (PEEP), patients with increased BMI may need additional inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). This study aimed to answer the question: What is the role of BMI when setting EPAP and IPAP? It was hypothesized that BMI does not significantly impact starting level of EPAP and IPAP.

Methods:

This study utilized a retrospective review of the electronic medical record of patients who underwent treatment with NIV between 2/17/19 and 3/31/19. IRB approval was obtained, and patient identifiers were removed after data collection was completed. The respiratory therapists’ assessment of respiratory rate in breaths/min as well as vital signs for SpO₂ and arterial blood gas values were assessed. The final IPAP and EPAP settings were recorded once the patient condition improved.

Results:

136 patients were provided NIV treatment. 129 were placed on Bi-Level Positive Airway Pressure and 7 on continuous positive airway pressure. There were 27 patients with a BMI <25 kg/m² and 109 had BMI >25 kg/m². All data was placed into IBM SPSS software v25 (IBM, Armonk, New York) and an unpaired t-test was used to compare final IPAP and EPAP settings of the two groups. There was a statistically significant difference in final EPAP settings (P = 0.02) between patients that have a recorded BMI of >25 kg/m² and those that are <25 kg/m². There was no significance in setting of IPAP levels (P = 0.25) between the two groups. Patients with a BMI <25 kg/m² required a mean EPAP of 8.30 ± 1.66 cm H₂O and an IPAP of 16.23 ± 2.916 cm H₂O when IPAP was used. Patients with BMI >25 kg/m² required a mean EPAP of 8.78 ± 1.96 cm H₂O and an IPAP of 16.50 ± 3.46 cm H₂O.

Conclusions:

This study shows that patients with an increased BMI (>25 kg/m²) may require increased EPAP when undergoing NIV treatment to improve clinical outcomes. This study also suggests that starting levels of EPAP should be considered based on a patient’s BMI. Disclosures: None