Respiratory motor function in seated and supine positions in individuals with chronic spinal cord injury

Highlights

• We examined changes in pulmonary function in patients with chronic SCI when assessed in seated and supine positions.

• These changes were evaluated using spirometry and maximum air way pressure measurements.

• The results indicate that postural effects on respiratory performance in these patients are specific to the respiratory task depending on severity and neurological level of SCI.

Abstract

This case-controlled clinical study was undertaken to investigate to what extent pulmonary function in individuals with chronic spinal cord injury (SCI) is affected by posture. Forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), maximal inspiratory pressure (PI_max) and maximal expiratory pressure (PE_max) were obtained from 27 individuals with chronic motor-complete (n = 13, complete group) and motor-incomplete (n = 14, incomplete group) C₂–T₁₂ SCI in both seated and supine positions. Seated-to-supine changes in spirometrical (FVC and FEV₁) and airway pressure (PI_max and PE_max) outcome measures had different dynamics when compared in complete and incomplete groups. Patients with motor-complete SCI had tendency to increase spirometrical outcomes in supine position showing significant increase in FVC (p = .007), whereas patients in incomplete group exhibited decrease in these values with significant decreases in FEV₁ (p = .002). At the same time, the airway pressure values were decreased in supine position in both groups with significant decrease in PE_max (p = .031) in complete group and significant decrease in PI_max (p = .042) in incomplete group. In addition, seated-to-supine percent change of PI_max was strongly correlated with neurological level of motor-complete SCI (ρ = −.77, p = .002). These results indicate that postural effects on respiratory performance in patients with SCI can depend on severity and neurological level of SCI, and that these effects differ depending on respiratory tasks. Further studies with adequate sample size are needed to investigate these effects in clinically specific groups and to study the mechanisms of such effects on specific respiratory outcome measures.

Introduction

Respiratory dysfunction is a major cause of morbidity and mortality in patients with SCI (Center, 2013, Garshick et al., 2005). Individuals with SCI are also at increased risk of sleep disordered breathing (Burns et al., 2000). Major causes of such dysfunction are respiratory motor control deficits associated with paresis, paralysis and spasticity of trunk and respiratory muscles (Gracies, 2005, Ovechkin et al., 2010, Schilero et al., 2009, Terson de Paleville et al., 2011). In general clinical practice and research the pulmonary function test (PFT) is used to evaluate respiratory motor function. In people with SCI, this test includes spirometrical and maximum airway pressure measures acquired with the test subject in the seated position (American Thoracic Society/European Respiratory Society, 2002, Brusasco et al., 2005, Jain et al., 2006, Miller et al., 2005, Stolzmann et al., 2008). While normative values are corrected for age, height, gender and race, they may also vary depending on body position (Manning et al., 1999, Segizbaeva et al., 2013) and functional capacity of the respiratory muscles (Rehder, 1998). It has been shown that healthy individuals exhibit significantly lower spirometrical and airway pressure outcomes in supine compared to seated position (Badr et al., 2002, Meysman and Vincken, 1998, Navajas et al., 1988, Vilke et al., 2000). It is not clear how postural changes affect respiratory function in individuals with SCI. In contrast to healthy controls, individuals with chronic SCI showed higher FVC and FEV₁ outcomes in supine compared to seated position (Chen et al., 1990, Estenne and De Troyer, 1987, Maeda et al., 1990). However, it has been shown that paraplegic patients with thoracic SCI can reach higher spirometrical values in seated position (Baydur et al., 2001). The dynamics of the maximum airway pressure measures in response to the seated-to-supine postural change in SCI population are less known. Compared to supine position, individuals with acute tetraplegic injury exhibited higher PE_max and PI_max outcomes in the semirecumbent position (Alvisi et al., 2012). At the same time, significant seated-to-supine decrease in PE_max has been found in the group of patients with motor-complete and incomplete cervical SCI (Sankari et al., 2014). Therefore, since postural factors may have differential impacts in healthy individuals and persons with SCI, it suggests that neurological level and severity of SCI may have complex effects on postural variations in spirometrical and maximum airway pressure measures. This study was undertaken to investigate the impact of postural changes on spirometrical and maximum airway pressure measures in patients with motor-complete and motor-incomplete chronic SCI.