Static Inspiratory Research Articles

Исследование силы дыхательных мышц у больных, перенесших COVID-19

Respiratory muscles (RM) are a very important part of the respiratory system that enables pulmonary ventilation. This study aimed to assess the post-COVID-19 strength of RM by estimating maximum static inspiratory (MIP or PImax) and expiratory (MEP or PEmax) pressures and to identify the relationship between MIP and MEP and the parameters of lung function. We analyzed the data of 36 patients (72% male; median age 47 years) who underwent spirometry, and body plethysmography, diffusion test for carbon monoxide (DLCO) and measurement of MIP and MEF. The median time between the examinations and onset of COVID-19 was 142 days. The patients were divided into two subgroups. In subgroup 1, as registered with computed tomography, the median of the maximum lung tissue damage volume in the acute period was 27%, in subgroup 2 it reached 76%. The most common functional impairment was decreased DLCO, detected in 20 (55%) patients. Decreased MIP and MEP were observed in 5 and 11 patients, respectively. The subgroups did not differ significantly in MIP and MEP values, but decreased MIP was registered in the second subgroup more often (18%). There were identified no significant dependencies between MIP/MEP and the parameters of ventilation and pulmonary gas exchange. Thus, in patients after COVID-19, MIP and MEP were reduced in 14 and 31% of cases, respectively. It is reasonable to add RM tests to the COVID-19 patient examination plan in order to check them for dysfunction and carry out medical rehabilitation.

Maximal Respiratory Pressures, their Association with Spirometric Parameters, Swimming Skills and Changes Due to Immersion in Water

Research background and hypothesis. We checked hypothesis that swimming skill improvement is more dependent on inspiratory muscle strength than endurance volume to be ventilated.Research aim was to determine associations between maximal static inspiratory (MIP) and expiratory (MEP) pressures, swimming skills, parameters of forced spirometry. Research methods. Investigation involved 62 female students (age 22.13 ± 1.3 years, height 168.4 ± 6.6 cm, and weight 61.3 ± 7.0 kg) of the Latvian Academy of Sports Education. All of them were non-smokers. Swimming skills in four strokes were evaluated by a swimming coach. MIP and MEP were measured at the mouth level outside the swimming pool and repeated in the swimming pool while the subject was immersed up to the neck level. Forced spirometry was performed according ATS guidelines outside the water. Research results. Average value for MIP outside the water was 109 ± 30 cm H 2 0 and for MEP it was 147 ± 33 cm H 2 0. There was positive correlation between peak expiratory flow and MIP, MEP, and the rate of increase of both pressures (p < 0.05). Forced vital capacity was not related to maximal pressures. Faster rate of inspiratory pressure increase was positively related to forced inspiratory volume in one second (p < 0.05). There was a significant decrease of MIP and the rate of increase of inspiratory pressure in the immersion state while no changes of expiratory parameters were observed. Discussion and conclusions. Swimming skill improvement is more dependent on inspiratory muscle strength than volume to be ventilated. Students with higher PEF have higher respiratory pressure parameters. Immersion in water decreases MIP, IMRPD and increases IMMRR. Changes of these parameters due to immersion are not related to swimming skills.Keywords: maximal inspiratory pressure, maximal expiratory pressure, swimming education, immersion in water.

Effects of inspiratory muscle training on exercise responses in Paralympic athletes with cervical spinal cord injury

We asked whether specific inspiratory muscle training (IMT) improves respiratory structure and function and peak exercise responses in highly trained athletes with cervical spinal cord injury (SCI). Ten Paralympic wheelchair rugby players with motor-complete SCI (C5-C7) were paired by functional classification then randomly assigned to an IMT or placebo group. Diaphragm thickness (B-mode ultrasonography), respiratory function [spirometry and maximum static inspiratory (PI ,max ) and expiratory (PE ,max ) pressures], chronic activity-related dyspnea (Baseline and Transition Dyspnea Indices), and physiological responses to incremental arm-crank exercise were assessed before and after 6 weeks of pressure threshold IMT or sham bronchodilator treatment. Compared to placebo, the IMT group showed significant increases in diaphragm thickness (P = 0.001) and PI ,max (P = 0.016). There was a significant increase in tidal volume at peak exercise in IMT vs placebo (P = 0.048) and a strong trend toward an increase in peak work rate (P = 0.081, partial eta-squared = 0.33) and peak oxygen uptake (P = 0.077, partial eta-squared = 0.34). No other indices changed post-intervention. In conclusion, IMT resulted in significant diaphragmatic hypertrophy and increased inspiratory muscle strength in highly trained athletes with cervical SCI. The strong trend, with large observed effect, toward an increase in peak aerobic performance suggests IMT may provide a useful adjunct to training in this population.

Changes in Lung Function and Respiratory Muscle Strength after Sternotomy vs. Laparotomy in Patients without Ventilatory Limitation

A relevant ventilatory defect occurs after sternotomy, a very common thoracic surgical opening. The mechanism of the ventilatory impairment is unclear. Moreover, until now, the effect of sternotomy on pulmonary gas exchange has scarcely been investigated. We evaluated the time-course up to recovery and changes in spirometry, maximum static inspiratory (PI_max) and expiratory (PE_max) mouth pressures and pulmonary gas exchange in 6 patients after sternotomy and in 8 patients after laparotomy. All patients were free of cardiopulmonary diseases and had normal preoperative lung function. Sternotomy and laparotomy decreased forced vital capacity (FVC) by 67 and 49%, respectively. Moreover, the percent decreases in PI_max, PE_max and PaO₂ after sternotomy vs. laparotomy were respectively 54 vs. 57%, 54 vs. 60%, and 22.6 vs. 7.5% (p < 0.05). Following sternotomy, the percent decreases in FVC correlated with the percent decreases in PI_max (p < 0.05) and PE_max (p < 0.01). The return to baseline values occurred after approximately 2 weeks. The present study shows that sternotomy can induce greater respiratory effects than laparotomy and suggests a relevant involvement of respiratory muscle weakness after surgical opening of the thorax. The study also supports the view that the evaluation of patient’s lung function before sternotomy can be clinically relevant.

Pulmonary Function in Uremic Patients on Long‐term Hemodialysis

Twenty patients with end‐stage renal failure who were on maintenance hemodialysis (HD) underwent pulmonary function testing (PFT) before and shortly after an HD session. On pre‐HD PFT, the mean values of all parameters except residual volume (RV) were in the normal range. Mean RV was high (152.9%), and mean diffusing capacity of the lung for carbon monoxide (DLCO) was high‐normal (110.4%). The pre‐HD static inspiratory (PImax) and expiratory pressures (PEmax) were much lower than normal (67.4% and 36.3%, respectively). After the HD session, repeat PFT revealed a small increase in expiratory flow rates, and a significant drop in PImax. There was a strong correlation between PImax and PEmax (r = 0.567, p < 0.01) at the pre‐ and post‐HD stages, indicating that common mechanism(s) are responsible for impairment of both inspiratory and expiratory muscle strength. The well‐preserved DLCO was thought to be due to the use of biocompatible dialyzer membranes. Chronic vascular congestion might be the other explanation of high DLCO.

Effect of digoxin on global respiratory muscle strength after cholecystectomy: a double blind study

BACKGROUNDUpper abdominal surgery has been shown to impair the function of the respiratory muscles. In addition, controversial results have been reported concerning the effect of digoxin on the diaphragm. The...

Influence of body weight on the severity of dyspnea in chronic obstructive pulmonary disease.

A substantial number of patients with COPD are underweight (UW); they comprise the clinical subtype of "dyspneic" or emphysematous. To determine whether these patients are more dyspneic than normal weight (NW) patients with COPD, we quantitated the severity of dyspnea, using a modified Medical Research Council (MRC) dyspnea scale, in 33 UW and 57 NW patients and compared their pulmonary function tests (PFTs), arterial blood gases (ABGs), and respiratory muscle strength as estimated by maximum static inspiratory (PI(max)) and expiratory (PE(max)) mouth pressures (all as means +/- SEM). Body mass index was 18.7 +/- 1.2 and 24.5 +/- 1.8 kg/m(2) in UW and NW patients, respectively (p < 0.0001). The MRC dyspnea scale was 3. 1 +/- 0.9 in UW and 2.5 +/- 1.2 in NW groups (p = 0.035). All PFT and ABG parameters were similar in the two groups except for DCO (36 +/- 11% in UW and 57 +/- 17% in NW, p < 0.001) and PI(max) (55 +/- 18 mm Hg in UW and 66 +/- 19 mm Hg in NW, p = 0.020). In a stepwise multiple regression model, %DCO and %MVV combined were the best predictors of dyspnea severity (R(2) = 0.30, p = 0.001). We conclude that UW patients with COPD are more dyspneic than NW patients. Although the origin of dyspnea in COPD is multifactorial, changes in DCO and respiratory muscle strength may contribute to its intensity.

Dyspnea in Obese Healthy Men

To determine whether obese, apparently healthy individuals experience dyspnea at rest and, if so, whether their pulmonary function test (PFT) profile and maximal respiratory pressures are different from obese, healthy subjects without dyspnea. Prospective, open. Pulmonary function test laboratory, Veterans Administration Medical Center. Twenty-three obese male subjects (each with a body mass index [BMI] of > 28 kg/m2) with an FEV1 level and an FEV1/FVC ratio > or = 80% of predicted and no coexisting conditions. Fifteen complained of dyspnea, where eight denied having it, at rest. Standard PFT parameters and maximum static inspiratory (P(Imax)) and expiratory (P(Emax)) mouth pressures were determined. Subjects with dyspnea had similar age and height but larger body weight (113.9+/-5.0 vs 97.4+/-2.6 kg, p = 0.03) and BMI (37.4+/-1.6 vs 31.8+/-0.7 kg/m2, p = 0.02) than subjects without dyspnea, and a greater number of them were current or previous smokers. Forced expiratory flow at 75% vital capacity (54.9+/-6 vs 75.5+/-7% predicted, p = 0.05), maximum voluntary ventilation (MVV; 90.2+/-3.8 vs 107.8+/-9.3% predicted, p = 0.05), and P(Emax) (77+/-2 vs 97.8% predicted, p = 0.007) were significantly reduced in the group of subjects with dyspnea. Large airway function (FVC, FEV1, and FEV1/FVC ratio), lung volumes, and gas exchange parameters were similar between the two groups. Some obese, but otherwise healthy, individuals experience dyspnea at rest. Reduced P(Emax) and MVV combined with greater body mass and peripheral airway disease are most likely responsible for the sensation of dyspnea in these individuals.

Pulmonary Function in Obese Subjects With a Normal FEV1/FVC Ratio

To determine pulmonary function test (PFT) profile and respiratory muscle strength (RMS) of a group of obese individuals who did not have evidence of obstructive airway disease or other underlying diseases affecting their respiratory system. Prospective, open. PFT laboratory, VA Medical Center. Sixty-three consecutive obese (body mass index greater than 27.8 kg/m2) male subjects without overt obstructive airway disease (FEV1/FVC ratio greater than 80%). Standard PFTs and maximum static inspiratory (PImax) and expiratory (PEmax) mouth pressures were determined. RMS was calculated from the following formula: (PImax+PEmax):2. Two distinct groups were identified, those with normal maximum voluntary ventilation (MVV) (> 80% predicted) and those with low MVV. Both inspiratory and expiratory flow rates (FVC, FEV1, forced expiratory flow at 50% vital capacity [V50], maximum inspiratory flow rate [MIFR]), lung volumes (vital capacity [VC], inspiratory capacity [IC], expiratory reserve volume), PImax, and RMS were significantly lower, and residual volume/total lung capacity (RV/TLC) ratio was significantly higher in obese subjects with low MVV compared with those in whom MVV was normal. MVV correlated significantly with FVC, FEV1, V50, MIFR, TLC, VC, IC, RV/TLC, and RMS; the strongest correlation was with MIFR (r = 0.76, p < 0.0001). Standard PFTs allow recognition of a subgroup of obese subjects without overt obstructive airway disease who have more severe lung dysfunction, the marker of which is a low MVV. Peripheral airway abnormalities may be responsible for these observations.

Alterations in inspiratory and leg muscle force and recovery pattern after a marathon

We measured lung mechanics and metabolic parameters, first in a series of 15 marathon (M) and 12 half-marathon (H) runners, before and 2.5 h after the race, in order to assess the running effect on respiratory muscles. Maximal static inspiratory (Pi) and expiratory (Pe) pressures, maximal voluntary ventilation (MVV), blood lactate (LAC), arterialized blood gases (ABG), plasma glucose (GLU), and, with a visual analog scale, subjective tiredness were assessed. Pi decreased in M and H without change in Pe, MVV, or lung mechanics; it was still abnormal 2.5 h after the race and did not correlate with LAC, ABG, training parameters, running times, or subjective tiredness. A second study of six other M compared Pi, Pe, adductor pollicis longus (Ppol), and triceps surae (Ptri) forces, aiming to: 1) assess the reproducibility of the prolonged Pi decrease without Pe change, 2) prove that such a decrease corresponded to a real reduction in inspiratory muscle force and was not due to a poor collaboration of the subjects, 3) correlate Pi decrease with the force loss of a potentially tired leg muscle: the triceps surae. We observed a significant and similar decrease in Pi and Ptri, but no change in Ppol and Pe. Moreover, the high correlation between Pi and Ptri diminutions suggested a similar recovery pattern for inspiratory and leg muscles. In conclusion, the prolonged decrease in Pi after such races is compatible with inspiratory muscle fatigue, which, as well as its recovery, is similar to leg muscle tiredness.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of posture and abdominal binding on respiratory pressures

We examined the effect of posture on the generation of respiratory pressures in 6 highly trained subjects. Transdiaphragmatic pressure was measured at FRC during bilateral percutaneous phrenic nerve stimulation (twitch Pdi) and maximal sniffs (sniff Pdi), with the abdomen bound and unbound. Maximum static inspiratory (PImax) and expiratory (PEmax) mouth pressures were measured with the abdomen unbound. Three postures were examined: seated (Se), semi-supine (30s), and supine (Su). Changes of posture did not significantly alter twitch Pdi. By contrast, sniff Pdi and static mouth pressures were significantly reduced in the Su posture. Abdominal binding significantly increased twitch Pdi only. We conclude that voluntary respiratory manoeuvres requiring activation, recruitment and coordination of different muscle groups are performed better in the Se position. We suggest that posture be standardised for serial comparative measurements of voluntary respiratory pressures in a given subject.

1214 RESPIRATORY MUSCLE FUNCTION IN IDIOPATHIC SCOLIOSIS

Patients with mild idiopathic scoliosis occasionally complain of exercise intolerance even in the presence of normal standard pulmonary function tests. We postulated that respiratory muscle compromise, possibly due to distortion of rib cage and diaphragm, might be a factor. With the technique of Black and Hyatt (Am Rev Resp Dis 99:696, 1969), we measured maximal static inspiratory (PImax) and expiratory (PEmax) pressures, which in the absence of intrinsic lung disease reflect respiratory muscle function. We studied 25 girls of mean age 18 years (range: 10-30 y) who had normal lung volumes (> 80% predicted) and were free from neuromuscular and intrinsic lung disease. Primary thoracic curves averaged 500 (range: 17-900). For comparison we also measured PImax and PEmax in 25 healthy girls, matched for age and body surface area. PImax for the study group averaged 89 cm H2O (SD:± 13 cm H2O) and that for the control group 115 ± 22 cm H2O. PEmax for the study group averaged 131 ± 26 cm H2O and for the control group 166 ± 8 cm H2O. Both differences were statistically significant (P < 0.01). There was no relationship between PImax or PEmax and the angle of thoracic curvature. We conclude that respiratory muscle compromise is frequently demonstrable in girls with mild idiopathic scoliosis and may be a factor in their symptoms. (J.R.M. is the recipient of a Parker B. Francis Foundation Fellowship).