Influence of respiratory loading on left‐ventricular function in cervical spinal cord injury
Bibliographic record
Abstract
Abstract Cervical spinal cord injury (C‐SCI) negatively impacts cardiac and respiratory function. As the heart and lungs are linked via the pulmonary circuit these systems are interdependent. Here, we utilized inspiratory and expiratory loading to assess whether augmenting the respiratory pump improves left‐ventricular (LV) filling and output in individuals with motor‐complete C‐SCI. We hypothesized LV end‐diastolic volume (LVEDV) would increase and decrease with inspiratory and expiratory loading, respectively. Participants (C‐SCI: 7M/1F, 35 ± 7 years; able‐bodied: 7M/1F, 32 ± 6 years) were assessed under five conditions during 45° head‐up tilt; unloaded, inspiratory loading with −10 and −20 cmH2O oesophageal pressure (Poes) on inspiration, and expiratory loading with +10 and +20 cmH2O Poes on expiration. An oesophageal balloon catheter monitored Poes, and LV structure and function were assessed by echocardiography. In C‐SCI only, (1) +20 cmH2O reduced LVEDV vs. unloaded (81 ± 15 vs. 88 ± 11 ml, P = 0.006); (2) heart rate was higher during +20 cmH2O compared to unloaded (P = 0.001) and +10 cmH2O (P = 0.002); (3) cardiac output was higher during +20 cmH2O than unloaded (P = 0.002); and (4) end‐expiratory lung volume was higher during +20 cmH2O vs. unloaded (63 ± 10 vs. 55 ± 13% total lung capacity, P = 0.003) but was unaffected by inspiratory loading. In both groups, −10 and −20 cmH2O had no significant effect on LVEDV. These findings suggest greater expiratory positive pressure acutely impairs LV filling in C‐SCI, potentially via impaired venous return, mediastinal constraint and/or direct ventricular interaction subsequent to dynamic hyperinflation. Inspiratory loading did not significantly improve LV function in C‐SCI and neither inspiratory nor expiratory loading affected cardiac function or lung volumes in able‐bodied participants. image Key points Cervical spinal cord injury (C‐SCI) alters both the cardiac and the respiratory system, but little is known about how these systems interact following injury. Here, we manipulated inspiratory or expiratory intrathoracic pressure (ITP) to mechanistically test the role of the respiratory pump in circulatory function in highly trained individuals with C‐SCI and an able‐bodied reference group. In individuals with C‐SCI, greater ITP during expiratory loading caused dynamic hyperinflation that was associated with impaired left‐ventricular filling. More negative ITP during inspiratory loading did not significantly alter left‐ventricular volumes in either group. Interventions that prevent dynamic hyperinflation and/or enhance the ability to generate expiratory pressures may help preserve left‐ventricular filling in individuals with C‐SCI.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".