The reliability of inspiratory resistive load magnitude and detection testing.

OBJECTIVES: To assess the test-retest reliability of inspiratory load detection and load magnitude perception tests in healthy volunteers. DESIGN: Cohort of convenience. SETTING: Respiratory physiology laboratory. PARTICIPANTS: Twenty healthy adults. INTERVENTIONS: On two separate occasions participants performed tests of inspiratory loading. Participants breathed through custom made resistive tubing and were asked to indicate when they detected a different resistance during inspiration. In a second test participants rated the magnitude of presented inspiratory loads using the modified Borg score. MAIN OUTCOME MEASURES: Intra-class Correlation Coefficient (ICC2,1) values for repeated tests of inspiratory load detection threshold and load magnitude rating. RESULTS: ICC2,1 values ranged from 0.657-0.786 for load detection testing and 0.739 to 0.969 for rating of load magnitude. CONCLUSIONS: The tests are simple and reliable measures of inspiratory load detection and magnitude rating. They can be used in future research to determine the effectiveness of interventions to reduce the effort of breathing in health and disease.

Impact of respiratory muscle training on respiratory muscle strength, respiratory function and quality of life in individuals with tetraplegia: a randomised clinical trial.

BACKGROUND: Respiratory complications remain a leading cause of morbidity and mortality in people with acute and chronic tetraplegia. Respiratory muscle weakness following spinal cord injury-induced tetraplegia impairs lung function and the ability to cough. In particular, inspiratory muscle strength has been identified as the best predictor of the likelihood of developing pneumonia in individuals with tetraplegia. We hypothesised that 6 weeks of progressive respiratory muscle training (RMT) increases respiratory muscle strength with improvements in lung function, quality of life and respiratory health. METHODS: Sixty-two adults with tetraplegia participated in a double-blind randomised controlled trial. Active or sham RMT was performed twice daily for 6 weeks. Inspiratory muscle strength, measured as maximal inspiratory pressure (PImax) was the primary outcome. Secondary outcomes included lung function, quality of life and respiratory health. Between-group comparisons were obtained with linear models adjusting for baseline values of the outcomes. RESULTS: After 6 weeks, there was a greater improvement in PImax in the active group than in the sham group (mean difference 11.5 cmH2O (95% CI 5.6 to 17.4), p<0.001) and respiratory symptoms were reduced (St George Respiratory Questionnaire mean difference 10.3 points (0.01-20.65), p=0.046). Significant improvements were observed in quality of life (EuroQol-Five Dimensional Visual Analogue Scale 14.9 points (1.9-27.9), p=0.023) and perceived breathlessness (Borg score 0.64 (0.11-1.17), p=0.021). There were no significant improvements in other measures of respiratory function (p=0.126-0.979). CONCLUSIONS: Progressive RMT increases inspiratory muscle strength in people with tetraplegia, by a magnitude which is likely to be clinically significant. Measurement of baseline PImax and provision of RMT to at-risk individuals may reduce respiratory complications after tetraplegia. TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trials Registry (ACTRN 12612000929808).

High-intensity interval training for patients with coronary artery disease: Finding the optimal balance.

BACKGROUND: The optimal characteristics of high-intensity interval training (HIIT) for patients with coronary artery disease (CAD) within cardiac rehabilitation (CR) are unclear. We assessed a HIIT protocol designed to balance patient safety, efficacy and enjoyment. METHODS: Twenty-nine patients with CAD completed 6-weeks (× 2 sessions per week) of HIIT within outpatient (phase 2) CR. HIIT comprised 15 repetitions × 30-seconds cycling at ∼85-90% maximum heart rate, interspersed with 30-seconds of active recovery. Key outcomes covered patient safety, efficacy (peak aerobic capacity, body composition, blood pressure and vascular function), and patient adherence and enjoyment. RESULTS: No cardiovascular-related adverse events were reported in relation to HIIT sessions. Patients showed significant improvement in peak aerobic capacity (mean +12%, p < 0.001, effect size d = 0.38), blood pressure (brachial systolic -7mmHg, p < 0.001, d = -0.59) and total body fat (-4%, p < 0.001, d = -0.49). Central adaptations were prominent (aortic systolic BP -5mmHg, p = 0.001, d = -0.50; visceral fat -10%, p = 0.001, d = -0.41). Patient enjoyment of training was high (5.5 out of 7 using the Exercise Enjoyment Scale) and measures of affective state improved following training (assorted p < 0.018). CONCLUSIONS: This HIIT protocol appears safe, effective and enjoyable for patients with CAD within CR. Improved aerobic fitness, blood pressure and body fat levels were observed indicating improved cardiovascular-risk. High patient enjoyment and improved mood suggest the HIIT could be sustainable for patients in the longer-term.

A randomised controlled trial of nasal decongestant to treat obstructive sleep apnoea in people with cervical spinal cord injury.

STUDY DESIGN: Prospective, double-blind, randomised, placebo-controlled, cross-over trial of nasal decongestion in tetraplegia. OBJECTIVES: Tetraplegia is complicated by severe, predominantly obstructive, sleep apnoea. First-line therapy for obstructive sleep apnoea is nasal continuous positive airway pressure, but this is poorly tolerated. High nasal resistance associated with unopposed parasympathetic activation of the upper airway contributes to poor adherence. This preliminary study tested whether reducing nasal decongestion improved sleep. SETTING: Participants' homes in Melbourne and Sydney, Australia. METHODS: Two sleep studies were performed in participants' homes separated by 1 week. Participants were given a nasal spray (0.5 mL of 5% phenylephrine or placebo) in random order and posterior nasal resistance measured immediately. Outcomes included sleep apnoea severity, perceived nasal congestion, sleep quality and oxygenation during sleep. RESULTS: Twelve middle-aged (average (SD) 52 (12) years) overweight (body mass index 25.3 (6.7) kg/m2) men (C4-6, AIS A and B) participated. Nasal resistance was reduced following administration of phenylephrine (p = 0.02; mean between treatment group difference -5.20: 95% confidence interval -9.09, -1.32 cmH2O/L/s). No differences were observed in the apnoea hypopnoea index (p = 0.15; -6.37: -33.3, 20.6 events/h), total sleep time (p = 0.49; -1.33: -51.8, 49.1 min), REM sleep% (p = 0.50; 2.37: -5.6, 10.3), arousal index (p = 0.76; 1.15: -17.45, 19.75), 4% oxygen desaturation index (p = 0.88; 0.63: -23.5, 24.7 events/h), or the percentage of mouth breathing events (p = 0.4; -8.07: -29.2, 13.0) between treatments. The apnoea hypopnoea index did differ between groups, however, all except one participant had proportionally more hypopnoeas than apnoeas during sleep after decongestion. CONCLUSIONS: These preliminary data found that phenylephrine acutely reduced nasal resistance but did not significantly change sleep-disordered breathing severity.

High nasal resistance is stable over time but poorly perceived in people with tetraplegia and obstructive sleep apnoea.

Obstructive sleep apnoea (OSA) is highly prevalent in people with tetraplegia. Nasal congestion, a risk factor for OSA, is common in people with tetraplegia. The purpose of this study was to quantify objective and perceived nasal resistance and its stability over four separate days in people with tetraplegia and OSA (n=8) compared to able-bodied controls (n=6). Awake nasal resistance was quantified using gold standard choanal pressure recordings (days 1 and 4) and anterior rhinomanometry (all visits). Nasal resistance (choanal pressure) was higher in people with tetraplegia versus controls (5.3[6.5] vs. 2.1[2.4] cmH2O/L/s, p=0.02) yet perceived nasal congestion (modified Borg score) was similar (0.5[1.8] vs. 0.5[2.0], p=0.8). Nasal resistance was stable over time in both groups (CV=0.23±0.09 vs. 0.16±0.08, p=0.2). These findings are consistent with autonomic dysfunction in tetraplegia and adaptation of perception to high nasal resistance. Nasal resistance may be an important therapeutic target for OSA in this population but self-assessment cannot reliably identify those most at risk.