# Inertial Sensors-Based Assessment of Human Breathing Pattern: A Systematic Literature Review
## 2 Methodology
### Data Extraction and Categorization
#### 2.4.6 Findings
[54] successfully detected respiratory frequency and amplitude with accelerometer data, distinguishing various BPs and coughs qualitatively. [PERSON] et al. [65] reported strong correlations between angular rate output and cannula pressure data, minimizing Root Mean Square (RMS) error in respiratory rate estimation, enhancing signal event reliability. [PERSON] et al. [59] indicated a strong correlation and agreement between device and Optoelectronic Plethysmography (OEP) breathing frequency measurements, especially within the healthy adult resting range, whilenoting errors at higher breathing frequencies. [PERSON] and [PERSON] [53] explored IMUs and spirometry signals, highlighting their capabilities in identifying expiration and inspiration onsets and phase shifts during BPs, though potential errors in IMU signal alignment during specific activities were noted. [PERSON] et al. [49] demonstrated the advantages of Acceleration-Derived Respiratory (ADR) measurements over Strain Gauge Respiratory (SGR) belts, particularly in accuracy and robustness across positions and breathing conditions. [PERSON] et al. [50; 51] reported strong correlations between accelerometer and spirometer signals, with generally low MSE values affirming their reliability in capturing respiratory patterns. [PERSON] et al. [61] highlighted a wearable device's accuracy in measuring respiratory rate, even during minimal movements, effectively eliminating motion artifacts and enhancing signal event reliability. By exploring the optimal number of sensors and setup configurations, several studies yielded valuable findings. [PERSON] et al. [48] demonstrated that accelerometers localized on the upper chest were effective in detecting the costal-superior pattern, while accelerometers placed on the lower chest and abdominal wall detected the costal-abdominal pattern. [PERSON] et al. [68] introduced a breath detection method utilizing information from two different IMUs placed on the anterior and posterior sides of the chest, suggesting that incorporating one more IMU on the abdomen could enhance breath activity evaluation. [PERSON] et al. [58] found that the quality of estimation significantly improved with up to eight accelerometers, with no notable enhancement in estimation quality observed beyond eight sensors, often finding right-hand accelerometers providing the optimal Minimum Mean Square Error (MMSE) estimate in various body postures. [PERSON] et al. [65] noted that combining accelerometer and magnetometer data had the potential to improve accuracy but came at the cost of increased power usage and device cost. The impact of changing position and body dynamics on data acquisition was explored in several studies, yielding noteworthy results. [PERSON] et al. [66] observed enhanced performance in the supine position compared with the seated position, possibly due to reduced trunk oscillations in the absence of back support during seating. [PERSON] et al. [67] highlighted the potential for motion artifacts resulting from subject movement, sensor patch disturbance, friction, and slippage. [PERSON] et al. [48] discovered regional differences in tidal breath patterns in the seated position, suggesting the feasibility of measuring such differences using accelerometers. [PERSON] et al. [60] found that the device's sensing capability was unreliable during walking, indicating limitations in capturing data during dynamic activities. [PERSON] et al. [54] successfully captured postural behaviors during sleep using long-term accelerometric recordings in normal subjects. [PERSON] et al. [49] demonstrated that ADR measurements provided superior results for the relative error of breath rates across different positions. [PERSON] et al. [50] noted that body position influenced correlation and time variables but maintained a mean correlation above 0.8 across positions and BPs. [PERSON] et al.