Physiological and clinical effects of trunk inclination adjustment in patients with respiratory failure: a scoping review and narrative synthesis

Abstract

Background: Adjusting trunk inclination from a semi-recumbent position to a supine-flat position or vice versa in patients with respiratory failure significantly affects numerous aspects of respiratory physiology including respiratory mechanics, oxygenation, end-expiratory lung volume, and ventilatory efficiency. Despite these observed effects, the current clinical evidence regarding this positioning manoeuvre is limited. This study undertakes a scoping review of patients with respiratory failure undergoing mechanical ventilation to assess the effect of trunk inclination on physiological lung parameters.

Methods: The PubMed, Cochrane, and Scopus databases were systematically searched from 2003 to 2023.

Interventions: Changes in trunk inclination.

Measurements: Four domains were evaluated in this study: 1) respiratory mechanics, 2) ventilation distribution, 3) oxygenation, and 4) ventilatory efficiency.

Results: After searching the three databases and removing duplicates, 220 studies were screened. Of these, 37 were assessed in detail, and 13 were included in the final analysis, comprising 274 patients. All selected studies were experimental, and assessed respiratory mechanics, ventilation distribution, oxygenation, and ventilatory efficiency, primarily within 60 min post postural change.

Conclusion: In patients with acute respiratory failure, transitioning from a supine to a semi-recumbent position leads to decreased respiratory system compliance and increased airway driving pressure. Additionally, C-ARDS patients experienced an improvement in ventilatory efficiency, which resulted in lower PaCO₂ levels. Improvements in oxygenation were observed in a few patients and only in those who exhibited an increase in EELV upon moving to a semi-recumbent position. Therefore, the trunk inclination angle must be accurately reported in patients with respiratory failure under mechanical ventilation.

Keywords: Acute respiratory distress syndrome; Body position; Driving pressure; End-expiratory lung volume; Respiratory dead space; Tidal volume; Trunk inclination.

Fig. 1

Flow chart

Fig. 2

Forest plot. Mean difference of C_RS with adjustments in trunk inclination from supine-flat to semi-recumbent position. TE (Treatment Effect) represents the difference in mean compliance of respiratory system between the two positions. SE (Standard Error): Uncertainty associated with the estimation of treatment effects. Weight (common/random): The weight that each study contributes to the calculation of the overall effect under the fixed effects model (common) and the random effects model (random). Confidence Intervals (CI): IV, Fixed + Random; 95% CI, 95% confidence interval for the difference in mean Compliance of respiratory system in both models. Tau², Chi², and I² indicate the degree of heterogeneity among studies. Here, I² = 24% indicates moderate heterogeneity. Tests for Overall Effect: Common Effect: Z =  − 6.46 (p < 0.01), indicating a statistically significant combined effect under the fixed effects model. Random Effects: t =  − 6.16 (p < 0.01), indicating a statistically significant effect under the random effects model. Bihari et al.1 evaluated non-obese patients with ARDS. Bihari et al. 2 evaluated obese patients with ARDS

Fig. 3

Forest plot. Forest plot. Mean difference of PaO₂/FIO₂ with adjustments in trunk inclination from supine-flat to semi-recumbent position. TE (Treatment Effect) represents the difference in mean PaO₂/FIO₂ between the two positions. SE (Standard Error): Uncertainty associated with the estimation of treatment effects. Weight (common/random): The weight that each study contributes to the calculation of the overall effect under the fixed effects model (common) and the random effects model (random). Confidence Intervals (CI): IV, Fixed + Random; 95% CI, 95% confidence interval for the difference in mean PaO₂/FIO₂ in both models. Tau², Chi², and I² indicate the degree of heterogeneity among studies. Here, I² = 51% indicates moderate heterogeneity. Tests for Overall Effect: Common Effect: Z = 0.78 (p < 0.43), indicating a significant combined effect under the fixed-effects model. Random Effects: t = 0.70 (p < 0.5), indicating a non-significant effect under the random-effects model

Fig. 4

Forest plot. Forest plot. Mean difference of PaCO₂ with adjustments in trunk inclination from supine-flat to semi-recumbent position. TE (Treatment Effect) represents the difference in mean PaCO₂ between the two positions. SE (Standard Error): Uncertainty associated with the estimation of treatment effects. Weights: Weight (common/random): The weight that each study contributes to the calculation of the overall effect under the fixed effects model (common) and the random effects model (random). Confidence Intervals (CI): IV, Fixed + Random; 95% CI, 95% confidence interval for the difference in mean PaCO₂ in both models. Tau², Chi², and I² indicate the degree of heterogeneity among studies. Here, I² = 37% indicates moderate heterogeneity. Tests for Overall Effect: Common Effect: Z = 4.69 (p < 0.01), indicating a significant combined effect under the fixed-effects model. Random Effects: t = 3.49 (p < 0.01), indicating a significant effect under the random-effects model

Fig. 5

Summarizes the main physiological effects of trunk inclination in patients with C-ARDS