Maximal Static Inspiratory Mouth Pressure Research Articles

Effects of Pulmonary Rehabilitation Including Inspiratory Muscle Training in Patients with Chronic Obstructive Pulmonary Disease after Stratification by the Degree of Static Hyperinflation

Inspiratory muscle training (IMT) improves inspiratory muscle strength, exercise capacity and health status in patients with chronic obstructive pulmonary disease (COPD). However, there is no additional effect on top of comprehensive pulmonary rehabilitation (PR). It is unclear whether patients with different baseline degrees of static hyperinflation respond differentially to IMT as part of a PR program. Therefore, the aim was to study the effects of IMT as an add-on on PR after stratification for baseline degrees of static hyperinflation. In this single center retrospective study data were extracted between June 2013 and October 2020 of COPD patients who participated in a comprehensive PR program including IMT. IMT was performed twice daily, one session consisted of 3 series of 10 breaths and training intensity was set initially at a load of approximately 50% of patients' maximal static inspiratory mouth pressure (MIP). The primary outcome measure was MIP. Secondary outcomes were the distance achieved on the 6-min walk test (6MWD), endurance cycling exercise capacity at 75% of the peak work rate (CWRT) and disease-specific health status using the COPD assessment test. 754 patients with COPD were screened for eligibility and 328 were excluded because of repeated PR programs, missing data or baseline residual volume (RV) > 350%. In total, 426 COPD patients were categorized into RV categories 50-130% (n = 84), 131-165% (n = 86), 166-197% (n = 86), 198-234% (n = 85) and 235-349% (n = 85). In the whole sample, MIP, endurance exercise capacity and health status improved significantly. The change in 6MWD was higher in the lowest baseline degree of static hyperinflation [+ 39 (9-92) m] compared with the baseline highest degree of static hyperinflation [+ 11 (- 18-54) m] (p < 0.05). IMT as part of a PR program in patients with COPD with different baseline degrees improved MIP irrespective of the degree of static lung hyperinflation. Improvement in functional exercise capacity was significantly higher in the group with the lowest degree of static hyperinflation compared with the patients with the highest degree of static hyperinflation.

Respiratory muscle training extends exercise tolerance without concomitant change to peak oxygen uptake: Physiological, performance and perceptual responses derived from the same incremental exercise test

There is conjecture over the efficacy of respiratory muscle training (RMT). The aim of this study was to establish whether or not exercise tolerance, physical performance and effort perceptions are influenced by RMT. Thirty-six healthy males (age 24 ± 4) agreed to participate (experimental group (EXP) n = 18, control (CON) n = 18). RMT was performed using an inspiratory pressure-threshold training device at either 55% (EXP) or 10% (CON) of maximal inspiratory effort. Measurements of spirometry and maximal static inspiratory mouth pressure were taken before and after 4 weeks of RMT in addition to an incremental test to volitional exhaustion for the determination of: (i) V˙O(2) peak; (ii) maximal velocity at volitional exhaustion (vV˙O(2) peak)); (iii) time to volitional exhaustion; and (iv) effort perceptions. There were no differences in spirometry, but mean maximal static inspiratory mouth pressure increased significantly in EXP (P < 0.01). V˙O(2) peak was unchanged following the 4-week intervention for both EXP and CON, although the proportion of EXP attaining the criteria for a V˙O(2) plateau significantly increased (P < 0.05). Both time to volitional exhaustion (P < 0.05) and vV˙O(2) peak were significantly improved for EXP (P < 0.05), while effort perceptions were reduced (P < 0.05). EXP tolerated higher running velocities during incremental exercise and demonstrated a significant flattening (plateau) of V˙O(2) after training. This suggests that RMT may promote an improved performance outcome vV˙O(2) peak probably as a result of blunted afferent sensations reducing the perceived discomfort of exercise at high ventilatory loads.

Respiratory muscle strength in rheumatic mitral stenosis improves after balloon valvotomy

Dyspnea is a common symptom in a patient with valvular heart disease. The mechanism underlying this disease is still uncertain. Respiratory muscle weakness has been proposed to be one of the mechanisms underlying dyspnea in heart failure, but this has not been adequately studied in valvular heart disease. We prospectively studied 20 patients with rheumatic mitral valve stenosis who were candidates for percutaneous balloon mitral valvotomy. Respiratory muscle strength assessment by maximal static inspiratory mouth pressure and maximal static expiratory mouth pressure was done on all patients at baseline and at 1 week after the procedure. The severity of dyspnea in study participants was also studied by the 6-min walk test and visual analog scale. Balloon valvotomy was followed by a significant improvement in the 6-min walking distance (from 219 +/- 30.15 to 237.55 +/- 32.25 m, P < 0.001), visual analog scale as a measure of dyspnea (from 60.95 +/- 12.16 to 44.4 +/- 13.71 mm, P < 0.001), inspiratory muscle strength (from 51.9 +/- 10.28 to 56.55 +/- 11.87 cmH2O, P < 0.001) and expiratory muscle strength (from 62.15 +/- 19.68 to 67.20 +/- 21.91 cmH2O, P < 0.001). Improvement in dyspnea in mitral stenosis after balloon valvotomy is associated with significant improvement in respiratory muscle strength.

Effect of Home Mechanical Ventilation on Inspiratory Muscle Strength in COPD

The mechanism responsible for chronic hypercapnic respiratory failure (HRF) in patients with COPD remains unclear. In this study, we tested the hypothesis that chronic HRF in patients with COPD is associated with low-frequency fatigue (LFF) of the diaphragm. To test this hypothesis, we measured the twitch transdiaphragmatic pressure (Tw Pdi) elicited by stimulation of the phrenic nerves in 25 patients with chronic HRF (mean [+/- SD] Paco(2), 55.2 +/- 5.2 mm Hg) due to COPD before and 2 months after the initiation of noninvasive mechanical ventilation (NIV) [pressure-cycled ventilation with inspiratory positive airway pressure of 19.0 +/- 2.5 cm H(2)O]. We reasoned that had LFF been present, Tw Pdi should rise after effective NIV. The treatment compliance with NIV was good (median of machine usage was 7.1 h per night). Paco(2) decreased from 55.2 +/- 5.2 to 48.8 +/- 5.9 mm Hg (p < 0.001), and Pao(2) increased from 53.1 +/- 5.9 to 57.7 +/- 7.0 mm Hg (p = 0.007). Mean Tw Pdi at baseline was 11.1 +/- 6.6 cm H(2)O and after treatment was 11.7 +/- 7.2 cm H(2)O (not significant). Also, maximal static inspiratory mouth pressure did not change significantly (44.3 +/- 15.9 cm H(2)O vs 46.5 +/- 19.7 cm H(2)O). LFF of the diaphragm does not accompany chronic HRF in patients with COPD.

Effect of Inspiratory Muscle Training on Muscle Strength and Quality of Life in Patients With Chronic Airflow Limitation: a Randomized Controlled Trial

Chronic airflow limitation (CAL) is a significant cause of illness and death. Inspiratory muscle training has been described as a technique for managing CAL. The aim of the present study was to evaluate the effectiveness of inspiratory muscle training on improving physiological and functional variables. Randomized controlled trial in which 35 patients with CAL were assigned to receive either an experimental (n=17) or control (n=18) intervention. The experimental intervention consisted of 2 months of inspiratory muscle training using a device that administered a resistive load of 40% of maximal static inspiratory mouth pressure (PImax). Inspiratory muscle strength, exercise tolerance, respiratory function, and quality of life were assessed. Significant improvement in inspiratory muscle strength was observed in the experimental training group (P=.02). All patients improved over time in both groups (P<.001). PImax increased by 8.9 cm H2O per month of training. Likewise, the health-related quality of life scores improved by 0.56 points. Use of a threshold loading device is effective for strengthening inspiratory muscles as measured by PImax after the first month of training in patients with CAL. The long-term effectiveness of such training and its impact on quality of life should be studied in a larger number of patients.

Treatment of chronic respiratory failure in kyphoscoliosis: oxygen or ventilation?

Patients with kyposcoliosis and chronic respiratory insufficiency are treated either with home oxygen therapy or ventilation. Kyphoscoliotic patients demonstrate impaired ventilatory mechanics, consequently ventilation seems to be the treatment of choice. Yet, no randomised controlled trials (CRT) exist to prove it. Most investigators find it difficult to ethically justify a CRT. Therefore, the current authors performed the following retrospective study: survival and pulmonary function were analysed in all consecutive kyphoscoliotic patients who started long-term oxygen therapy (LTO group; n=15, aged 62+/-11 yrs (mean+/-SD)) or LTO plus nocturnal nasal intermittent positive pressure ventilation (nNIPPV group; n=18, aged 61+/-7 yrs) in the Dept of Pulmonology (University Hospital Gasthuisberg, Leuven) between 1990-2002. Prior to treatment partial pressure of oxygen (PO2) was lower, partial pressure of carbon dioxide (PCO2) tended to be higher and vital capacity (VC) tended to be lower in the nNIPPV group than in the LTO group (PO2 5.9+/-1 versus 6.7+/-0.9 kPa (44+/-8 versus 50+/-7 mmHg), PCO2 8+/-1 versus 7.3+/-0.9 kPa (60+/-8 versus 55+/-7 mmHg), VC 32+/-12 versus 40+/-16% predicted, or 645+/-244 versus 970+/-387 mL). In the nNIPPV group the 1-yr survival was higher (100% versus 66%). nNIPPV patients demonstrated an improvement in PO2 (breathing air) +54%, PCO2 (breathing air) -21%, VC +47% and maximal static inspiratory mouth pressure +33%; these improvements were absent in the LTO group. In conclusion, nocturnal nasal intermittent positive pressure ventilation, plus long-term oxygen therapy results in more favourable survival and changes in blood gases and respiratory function than long-term oxygen therapy alone.

Evaluation of an inspiratory muscle trainer in healthy humans

The Powerbreathe®is an inspiratory muscle trainer promoted as improving inspiratory muscle strength (and consequently exercise performance) in athletes and patients with respiratory disease. No published evidence supports its efficacy. We performed a prospective randomized controlled study in which 12 normal subjects received either Powerbreathe®training or sham training for a 6-week period. The primary outcome measure was diaphragm strength evaluated as twitch transdiaphragmatic pressure (Tw Pdi) but secondary outcome measures were provided by full respiratory muscle assessment and cardiopulmonary exercise testing. An advantage to training was observed when outcome was assessed by maximal static inspiratory mouth pressure (mean advantage 14·5 cm H2O, 95% CI 2·2–26·9 cm H2O, P=0·025). However, no significant difference was observed between the groups in any other parameter. In particular the Δ Tw Pdi was not different between groups (mean ‘advantage’−0·7 cmH2O, 95% CI–7·0–+5·5 cmH2O,P =0·8). The continued sale and use of the Powerbreathe®device is not justified by our data. A sample size calculation showed that 234 subjects would need to be randomized to definitively refute the hypothesis that Powerbreathe®improves Tw Pdi and we argue that such a study is required.

Respiratory Muscle Strength and Hemodynamics in Chronic Heart Failure

To examine whether respiratory muscle weakness is associated with cardiac function and/or exercise capacity in chronic heart failure (CHF), 23 patients with CHF were evaluated with respiratory muscle strength, pulmonary function tests, cardiac catheterization, and exercise test. The subjects were divided into three groups on their New York Heart Association (NYHA) functional class. Group A consisted of 13 patients with NYHA functional classification class 3 or 4, group B consisted of 10 patients with NYHA classification class 2, and group C consisted of 15 age-matched normal controls. Respiratory muscle strength was assessed with maximal static inspiratory mouth pressure at residual volume level and expiratory mouth pressure at total lung capacity level (PImax, PEmax, respectively). Pulmonary functions in patients with CHF showed almost normal. PImax in group A was significantly less than that in group B or C, although PImax in group B was not significantly different from that in group C. In the patients with CHF, PImax correlated positively with cardiac index and maximal oxygen consumption (r = 0.460 and r = 0.503, p < 0.05, respectively). These findings suggest that inspiratory muscle strength, which was impaired in patients with severe CHF, may be dependent on cardiac function and may be one of the limiting factors on impaired exercise capacity in the patients with CHF.

Salbutamol, a β2-adrenoceptor agonist, increases skeletal muscle strength in young men

1. beta 2-Adrenoceptor agonists have been shown to increase rapidly lean body mass and reverse muscle wasting in several animal models of human illness. However, no published information is available for humans. In the present study, we investigated the effects of a slow-release preparation of salbutamol or a placebo on skeletal muscle functional capacity in 12 healthy men. The strength of different muscle groups was measured on two occasions before and after 14 and 21 days of treatment. 2. No significant changes in muscle strength were observed with placebo during the trial. In contrast, the strength of both quadriceps muscles increased significantly (12 +/- 3%) after 14 days on salbutamol, and remained elevated at 21 days. Whereas the strength of the hamstring muscles of the dominant leg significantly increased after 21 days on salbutamol (22 +/- 6%), the strength of the non-dominant hamstring muscles returned to baseline values. 3. There was no significant change in the grip strength of either hand in these subjects during the trial. The maximal static inspiratory mouth pressure increased significantly (7 +/- 2%) after 14 days on salbutamol, and increased further after 21 days (15 +/- 4%); the expiratory mouth pressure remained constant. No significant changes in body weight, skinfold thickness, lean body mass or limb circumferences were measured in either group. 4. These data demonstrate that short-term administration of salbutamol increases voluntary muscle strength in man. However, the magnitude and duration of this effect vary between muscle groups. This study implies that the beta 2-adrenoceptor agonists may be of therapeutic potential in altering skeletal muscle function in humans.

Assessment of Diaphragm Weakness

Thirty patients with breathlessness and diaphragm weakness were studied by measuring transdiaphragmatic pressures during maximal inspirations to total lung capacity, maximal static inspiratory efforts from residual volume, and maximal sniffs from functional residual capacity. Maximal static respiratory mouth pressures were also recorded, and rib cage and abdominal movements were monitored with pairs of magnetometers. Sniff transdiaphragmatic pressure was abnormally low in all patients and was correlated with transdiaphragmatic pressure during other maneuvers, and with maximal static inspiratory mouth pressures. There was no relationship between the severity of dyspnea and transdiaphragmatic pressure in the group as a whole. The weakest patients had orthopnea and paradoxical inward inspiratory motion of the anterior abdominal wall; measurements suggested that at least 30 cm H2O transdiaphragmatic pressure was required to overcome the hydrostatic pressure of the abdominal contents. By contrast, patients with mild diaphragm weakness had neither orthopnea nor abdominal paradox. Thus, patients with breathlessness and diaphragm dysfunction may have varying degrees of diaphragm weakness that may be difficult to detect clinically; the diagnosis and quantification of diaphragm weakness requires the measurement of transdiaphragmatic pressure.