Biomedical subjects
J Gea
Publications and source records attributed to J Gea.
[Muscle function in other obstructive pulmonary diseases, in malnutrition and in sepsis].
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[Basic structure of respiratory and peripheral muscles in the beagle dog].
BACKGROUND: The dog is one of the most widely used animals in studies of respiratory physiopathology, mainly because of its physiological characteristics. However, ethical and legal constraints are placed on the use of some species in our context. OBJECTIVE: We studied the underlying structural features of respiratory and peripheral muscles in the beagle dog in order to suggest reference values for future studies. METHOD: Fourteen young beagles were selected. Samples were taken from the costal diaphragm (DFG), external intercostal (EI) and vastus medialis (VM) muscles. We analyzed fiber percentages and sizes (immunohistochemistry, using myosin heavy chain [MyHC (monoclonal antibodies), percentages and absolute number of MyHC isoforms (electrophoresis and ELISA), and level of membrane damage (immunohistochemistry, using anti-fibronectin monoclonal antibodies). RESULTS: In the EI muscle, type I fibers were larger (by 20%) than type II fibers. Fibers resistant to fatigue (type I) predominated greatly over fast contraction fibers (type II) in all three muscles analyzed (DFG 57% 11% vs. 45% 12%; EI 58% 5% vs. 43% 5%; and VM 70% 8% vs. 34% 7 %). Few hybrid fibers (co-expression of fast and slow MyHC) were found and their percentages were similar in all three muscles. The absolute expression of MyHC was greater in the VM than in the respiratory muscles, with a relative predominance of the MyHC I isoform in the DFG and VM muscles and a similar tendency in the EI muscle. Membrane damage was very slight in all three muscles. CONCLUSIONS: The phenotype characteristics of respiratory and peripheral muscles in the beagle correspond to what we would expect functionally for a breed initially selected for hunting, with minimal lesions under normal circumstances, a predominance of fibers and proteins that are resistant to fatigue, and larger fibers in the EI, a muscle that plays a role in respiration in dogs.
[Interleukin 10 and tumor necrosis factor alpha gene expression in respiratory and peripheral muscles. Relation to sarcolemmal damage].
BACKGROUND: Tumor necrosis factor alpha (TNF-alpha) has been implicated in loss of muscle mass in chronic obstructive pulmonary disease and other consumptive processes. TNF-alpha production would be related to inflammation arising from pulmonary disease itself or, alternatively, from smoking, and would be carried to the muscle through the blood stream. However, it has also been suggested that TNF-alpha may be expressed directly in muscle tissue. Regardless the site of production of TNF-alpha, its relation to subsequent muscle damage is unclear. OBJECTIVE: We studied the expression of TNF-alpha and an interleukin inhibitor of its production (IL-10) in the main respiratory muscles and a peripheral muscle in the dog. METHOD: Nine young, male Beagle dogs were included. From all animals we obtained a biopsy of the diaphragm (Dph) and external intercostal (ExtI) muscles and a leg muscle (internal vastus of the quadriceps, IntV). TNF-alpha and IL-10 gene expressions were measured through the analysis of messenger RNA levels, using reverse transcription and polymerase chain reaction. We also assessed sarcolemmal damage using intracellular fibronectin detection (immunohistochemistry). RESULTS: The expression of both cytokines showed wide interindividual variability. On the one hand, TNF-alpha (was very low in Dph and ExtI (0.02 0.03 and 0.05 0.06 a.u., respectively), but relatively high in the IntV (0.14 0.08 a.u.). IL-10 expression, on the other hand was low in the Dph (0.06 0.05 a.u.) and slightly higher in the ExtI (2.7 1.9 a.u., p < 0.01) and IntV (1.6 1.7 a.u.). Sarcolemmal damage was minimal in all three muscles and was related to TNF-alpha expression in the peripheral muscle (r = 0.682, p < 0.05). CONCLUSIONS: 1) TNF-alpha and IL-10 appear to be constitutively expressed within the skeletal muscle in dogs. 2) Basal TNF-alpha expression is lower in respiratory muscles than in peripheral muscles. 3) The expression in the latter is related to membrane damage.
[Low-weight syndrome associated with COPD in our setting].
UNLABELLED: The high prevalence of chronic obstructive pulmonary disease (COPD) has considerable economic and health-related impact. The consequences arise largely from limitations on a patient's activity and shortened life expectancy. Low body weight has recently been implicated as a factor affecting limitations. Although the reason is not clear, weight loss appears to affect many patients (from 25 to 35% in different series), at least in Europe and North America. However, the situation is thought to be different in the Mediterranean area. OBJECTIVE: To estimate the prevalence of the low weight syndrome in patients with COPD in our area. METHODS: COPD patient characteristics monitored by our laboratory over the last two years (2000 and 2001) were reviewed. RESULTS: The prevalence of a body mass index (BMI) less than 20 kg/m2 was only 6.6% among the 3,126 patients studied. That percentage fell to 3.1% with a cutoff of 18 kg/m2. The figure was even more striking if we consider that half the patients had severe disease (FEV1 < 50% of reference). BMI was directly related to FEV1/FC and CO transfer. CONCLUSIONS: These results suggest that COPD patients in our geographic area have characteristics that distinguish them from those previously described in other countries. Specifically, the prevalence of low weight syndrome in our area appears to be lower. However, larger studies should be performed to confirm this finding.
Procion orange tracer dye technique vs. identification of intrafibrillar fibronectin in the assessment of sarcolemmal damage.
BACKGROUND: The use of Procion orange dye (POD) is one of the most widely accepted techniques to assess sarcolemmal damage. This phenomenon has been related to functional adaptation in skeletal muscles. The POD method includes intravenous injection of this colorant in vivo, enabling its identification inside those fibres with membrane leaks (fluorescence). However, the safety of the use of POD has not been proven. AIM: This study was designed to compare POD with a safer alternative, involving the identification of intracellular fibronectin using specific antibodies. METHOD: Eight Swiss mice were submitted to electrical stimulation of the lower limbs at different frequencies (10-80 Hz). Subsequently, the POD solution was infused, and samples from the vastus medialis muscle were obtained 24 h later. Samples were processed and serial sections were analysed using immunohistochemistry (monoclonal antibodies against fibronectin) and epifluorescence microscopy. RESULTS: Ninety-eight per cent of the fibres were equally classified by both techniques, which in addition showed good correlation (percentages of damaged fibres, r = 0.998, P < 0.001) and concordance (R1 = 0.82) in quantitative terms. CONCLUSIONS: Although the two techniques compared here are based on different principles, both are comparable in assessing sarcolemmal damage. This would facilitate comparisons between human and experimental studies. In addition, the fibronectin technique appears to be a suitable alternative for long-term studies including repeated biopsies.
Expiratory muscle endurance in chronic obstructive pulmonary disease.
BACKGROUND: A reduction in expiratory muscle (ExM) endurance in patients with chronic obstructive pulmonary disease (COPD) may have clinically relevant implications. This study was carried out to evaluate ExM endurance in patients with COPD. METHODS: Twenty three patients with COPD (FEV(1) 35 (14)% predicted) and 14 matched controls were studied. ExM endurance was assessed using a method based on the use of an expiratory threshold valve which includes two steps. In step 1 the load is progressively increased (50 g every 2 minutes) until task failure is reached, and the pressure generated against the highest tolerated load is defined as the maximal expiratory sustainable pressure (Pthmax). In step 2 subjects breathe against a submaximal constant load (80% of Pthmax) and the time elapsed until task failure is termed the expiratory endurance time (Tth(80)). In addition, the strength of peripheral muscles (handgrip, HGS) and respiratory muscles (maximal inspiratory and expiratory pressures, PImax and PEmax, respectively) was evaluated. RESULTS: Patients with COPD had lower ExM strength and endurance than controls: PEmax 64 (19)% predicted v 84 (14)% predicted (mean difference 20%; 95% confidence intervals (CI) 14 to 39); Pthmax 52 (27) v 151 (46) cm H(2)O (mean difference 99, 95% CI 74 to 123); and Tth(80) 9.4 (6.3) v 14.2 (7.4) min (mean difference 4.8, 95% CI 1.0 to 10.4; p<0.01 for all). Interestingly, ExM endurance directly correlated with both the severity of airways obstruction (Pthmax with FEV(1), r=0.794, p<0.01) and the reduction in strength observed in different muscle groups (Pthmax with HG, PImax or PEmax, r=0.550, p<0.05; r=0.583, p<0.001; and r=0.584, p<0.001, respectively). CONCLUSIONS: ExM endurance is decreased in patients with COPD. This impairment is proportional to the severity of the disease and is associated with lower strength in different muscle groups. This suggests that systemic effects are implicated in the impairment observed in ExM function.
Injury of the human diaphragm associated with exertion and chronic obstructive pulmonary disease.
Injury of the diaphragm may have clinical relevance having been reported in cases of sudden infant death syndrome or fatal asthma. However, examination of diaphragm injury after acute inspiratory loading has not been reported. The purpose of this study was to determine whether an acute inspiratory overload induces injury of the human diaphragm and to determine if diaphragm from chronic obstructive pulmonary disease (COPD) is more susceptible to injury. Eighteen patients with COPD and 11 control patients with normal pulmonary function (62 +/- 10 yr) undergoing thoracotomy or laparotomy were studied. A threshold inspiratory loading test was performed prior to surgery in a subset of seven patients with COPD and five control patients. Samples of the costal diaphragm were obtained during surgery and processed for electron microscopy analysis. Signs of sarcomere disruption were found in all diaphragm samples. The range of values of sarcomere disruption was wide (density: 2-45 abnormal areas/100 microm(2); area fractions: 1.3-17.3%), significantly higher in diaphragm from patients with COPD (p < 0.05) and with the greatest injury after inspiratory loading. We conclude that sarcomere disruption is common in the human diaphragm, is more evident in patients with COPD, and is higher after inspiratory loading, especially in the diaphragm of those with COPD.
Expiratory muscle endurance in middle-aged healthy subjects.
To evaluate expiratory muscle endurance in middle-aged healthy subjects using incremental as well as constant expiratory loads, 14 healthy volunteers (51 +/- 16 years) were submitted to a specific endurance test, which was performed breathing against a threshold valve, and was divided into two parts. In part I, the load was progressively increased (50 g each 2 min) until task failure occurred. The mean mouth pressure generated against the highest load held for at least 60 sec was defined as the maximal expiratory sustainable pressure (Pth(max)). In part II, each subject breathed against a constant submaximal expiratory load (80% Pth(max)) until task failure occurred (expiratory endurance time or Tth(80)). Both parts of the test were repeated 24-48 h later. Progressive expiratory loading induced a linear increase in mouth expiratory pressure and the Pth(max) obtained was 141 +/- 43 cm H(2)O, representing 74 +/- 28% of the maximal expiratory pressure (PE(max)). Under constant loads, the Tth(80) was 17 +/- 9 min. At the end-point of both parts, the tension time index for expiratory muscles was dramatically increased (>0.25), and both EMG central frequency and PE(max) were decreased with no changes in maximal inspiratory pressure or inspiratory capacity. Extreme dyspnea was present in most of the subjects but no complications were observed. The endurance of expiratory muscles can be easily assessed in healthy subjects using this method, which has acceptable reproducibility and tolerance.
[Metabolic activity of the external intercostal muscle of patients with COPD].
INTRODUCTION: The external intercostal muscle is a relevant contributor to ventilatory work in situations of overloading. Like other respiratory muscles, the external intercostal muscle seems to undergo a process of structural remodeling to adapt to a situation of functional disadvantage. However, findings from published studies of morphology have differed to a certain degree. On the one hand, the proportion of fibers involved in anaerobic metabolism increases; on the other hand, the number of capillaries also increases, an occurrence that would facilitate aerobic metabolism. OBJECTIVE: This study was designed to analyze the activity of several key enzymes involved in the principal metabolic pathways in the external intercostal muscles of patients with COPD. METHODOLOGY: We studied 6 patients with COPD (65 +/- 8 years, BMI 23 +/- 3 kg/m2, FEV1 51 +/- 9% ref, RV 184 +/- 38% ref, PaO2 81 +/- 10 mmHg) and 6 control subjects matched for age and anthropometric variables but with normal lung function. External intercostal muscle samples were taken from each patient (fifth intercostal space, non-dominant side). The samples were treated by conventional spectrophotometry to determine enzyme activity as follows: citrate synthase (CS, Krebs cycle), phosphofructokinase (PFK, by common glycolysis), lactate dehydrogenase (LDH, anaerobic glycolysis) and creatine phosphokinase (CPK, use of energy reserves). RESULTS: Patients with COPD showed greater PFK enzyme activity (93 +/- 25 versus 44 +/- 9 micromol/min/g of fresh weight; p = 0.001) and LDH (308 +/- 42 versus 231 +/- 29 micromol/min/g; p < 0.01) than did control subjects. However, CS and CPK activity was similar in both groups (82 +/- 31 versus 90 +/- 20 micromol/min/g and 4017 +/- 1734 versus 3048 +/- 464 micromol/min/g, respectively), although the latter displayed noteworthy dispersion of values among COPD patients, with levels in some patients being three-fold greater than in controls. RV was directly related to glycolytic enzyme activity (with PFK, r = 0.716, p < 0.01; with LDH r = 0.697, p < 0.05) and PFK and LDH also correlated with each other (r = 0.737, p < 0.01). CONCLUSIONS: Based on the enzyme activity studied, oxidative activity seems to be conserved in the external intercostal muscle of patients with COPD. Activity in the glycolytic pathway seems to increase and the increase is proportional to the severity of COPD. These findings are probably the expression of a combination of adaptive structural factors.
Structural and functional changes in the skeletal muscles of COPD patients: the "compartments" theory.
This review focuses on the structural and functional changes occurring in respiratory as well as peripheral muscles in COPD patients. These changes are particular for each muscle territory or compartment. Respiratory muscles predominantly undergo structural adaptive changes. However, they have to do their job in unfavourable mechanical conditions and thus their function is impaired. Peripheral muscles have to be grouped in at least two different compartments: upper and lower limb muscles. The structure and function are relatively preserved in the former, due to the maintenance of some daily activities involving the arms or even the use of some of these muscles in the ventilatory effort. Lower limb muscles in contrast undergo involute structural changes which result in an impairment in their function and in the global exercise capacity of the individual. Deconditioning due to a reduction in daily activities secondary to ventilatory impairment is probably the driving factor for these changes. Although the level of activity appears to be the main determining factor in changes occurring in different territories, this would be modulated by other local and systemic factors, such as inflammation, oxidative stress, drugs and nutritional abnormalities.
[Mechanical and metabolic reproducibility of resistance test of expiratory muscles with incremental threshold loading].
BACKGROUND: The study of respiratory muscle endurance has mainly focused on inspiratory muscles. A new method to measure expiratory muscle endurance, through incremental threshold loading using a weighted plunger valve, has recently been described. OBJECTIVES: To evaluate the mechanical features of the plunger valve and the reproducibility of the method from the standpoint of both mechanics and metabolism. METHODS: Four untrained healthy subjects performed an incremental test with expiratory threshold loading (50 g every 2 min) on each of three non-consecutive days; each test continued until the subject could no longer open the valve. Mouth pressure was recorded continuously during each test; on the first two test days, oxygen consumption (VO2) was also measured. RESULTS: Opening and closing pressures were the same and were independent of expiratory flow, with a linear load-pressure relationship (4 cmH2O) for every 10 g of weight). The maximal tolerated load (MTL) in the three tests was stable for two of the subjects, whereas the maximal load was reached by the other two subjects in the second and third tests, respectively. When MTL was reached in the third test, mean and peak mouth pressures (the latter expressed as percent of maximal expiratory pressure [MEP]) were 49 +/- 4% and 71 +/- 4%, respectively; the expiratory tension-time index measured at the mouth ([PMEANmouth/MEP] x [TE/Ttot]) was 0.25 +/- 0.02 (TE: expiratory time; Ttot: total time). In the first and second tests, we also measured oxygen consumption of the recruited muscles, which were mainly the expiratory muscles (VO2respmax); consumption in the last test was 213 +/- 65 ml O2/min (2.9 +/- 1.1 ml O2/kg/min). The intraindividual coefficient of variation ranged from 6.3% to 19.5% for the mechanical parameters and from 14% to 21% for the metabolic ones. CONCLUSIONS: The expiratory endurance test using a threshold valve allows quantification of muscle and metabolic reserve under incremental expiratory loads. The valve has appropriate mechanical characteristics for this purpose and reproducibility is acceptable, through the precise determination of the may require up to three tests.
[Features of patients with bronchial asthma seen at the emergency department of a referral hospital in a semirural area].
UNLABELLED: Bronchial asthma is a chronic disease whose prevalence and severity is increasing. Appropriate treatment of exacerbation seems to affect the subsequent course of disease. OBJECTIVES: To assess the extent of application of guidelines for treating exacerbations of asthma and to describe the clinical and epidemiological characteristics of patients. PATIENTS AND METHODS: All patients presenting with exacerbations to the emergency room of a referral hospital in a semi-rural area of Catalonia were enrolled consecutively. We recorded symptoms, function and treatment variables during the emergency and when the patient was stable, at which time we also administered the Asthma Quality of Life Questionnaire (AQLQ). RESULTS: Forty-seven percent of patients resided in rural villages. Seventy-one percent lived in the area served by our hospital. Of the remaining patients, 57% came from municipalities in the Baix Empordà area, 29% in Alt Empordà area and 14% in La Selva area. Seventy-one percent went to the hospital directly from home, 66% of them were in the province of Girona; 75% of those homes were within urban areas. Of the 29% who had been sent to the emergency room by a physician, 71% were from a rural area. The 119 asthma exacerbations treated (114 patients, 71 females, 42 +/- 23 years) accounted for 0.3% of all emergency room visits. The exacerbation was considered severe in 31%, moderate in 47% and mild in all remaining cases. Eighty-eight percent of patients had experienced an exacerbation before. Symptoms were often present before the attack, but nearly half the patients were receiving relatively inadequate medication. Peak expiratory flow and oxygen saturation were recorded in 70% of cases and both variables improved after initial treatment (250 +/- 97 to 349 +/- 92 l/min, p < 0.001; and 92 +/- 7 to 96 +/- 2%, p < 0.01, respectively). All patients received inhaled salbutamol, 44% inhaled corticosteroids and 73% intravenous corticosteroids. A quarter of the patients were admitted to the ward (0.4% of all admissions) and 4% were admitted to the intensive care unit. Patients stayed 8.8 +/- 1.4 h in the emergency room. When patients were stable, asthma was severe in 14%, moderate in 42%, mild but persistent in 27%, and occasional in 17%. The total score on the AQLQ was 13.8 +/- 11.1, with mood being the dimension with the highest score (5.1 +/- 4.9). This score, along with social restriction, were lowest in the group of patients with chronic airflow obstruction. CONCLUSIONS: Nearly half the patients were from rural villages most of which were located outside the zone served directly by our hospital. The preference for specialized medical attention would explain the percentage of patients seen who did not belong to the assigned area. Difficulty of access to the hospital from certain rural areas would account for the greater number of rural patients who had been referred by a physician. Clinical management and monitoring of asthmatic patients with exacerbation could be improved by greater diffusion and application of guidelines. It would be interesting to incorporate come sort of questionnaire on quality of life while taking a patient's history.
[The characteristics of the mechanical activity of the respiratory muscles during the diaphragmatic respiration technic].
UNLABELLED: Noteworthy among breathing training techniques is so-called diaphragmatic breathing. In spite of the technique's name, however, little is known of the functional characteristics of this ventilatory method. OBJECTIVE: To asses the mechanics of respiratory muscles, particularly diaphragm muscles, during diaphragmatic breathing in patients with severe chronic obstructive pulmonary disease (COPD). METHODS: Ventilatory pattern and respiratory pressures (abdominal [Pga], intrathoracic [Pes] and transdiaphragmatic [Pdi]) were studied in 10 patients with severe COPD in stable phase (age 69 +/- 6 years, FEV1 33 +/- 12% ref) at baseline and during deep breathing with spontaneous muscle recruitment (SMR) and during breathing training. Measurements were taken with the patient seated and in supine decubitus position. RESULTS: In seated position ventilatory pattern was similar with SMR and during breathing training. Mean Pdi during airflow, however, was greater during breathing training than with SMR (34.8 +/- 8.0 and 29.3 +/- 9.3 cmH2O, respectively, p < 0.05) for similar levels of Pes. Mechanical effectiveness of the diaphragm expressed as Vt/Pdi) was less during breathing training, however (36.1 +/- 10.4 and 49.5 +/- 15.8 cc/cmH2O, p < 0.05), with no changes in overall efficacy of respiratory muscles (Vt/Pes). In supine decubitus position, ventilatory patterns of SMR and breathing training were similar, although Vt and T1 were slightly higher in the latter (1,065 +/- 305 vs. 1,211 +/- 314 cc, p < 0.01; and 2.76 +/- 1.32 vs. 3.07 +/- 1.23 sec, p < 0.05). Pdi was also higher during breathing training (29.7 +/- 10.2 and 38.0 +/- 10.5 cmH2O, p < 0.05), although accompanied in this case by a higher Pes (21.2 +/- 7.5 to 26.4 +/- 8.4 cmH2O, p < 0.005). In supine decubitus position, the effectiveness of both diaphragm muscles and respiratory muscles overall was similar for both ventilatory modes. CONCLUSIONS: Breathing training truly involves greater use of the diaphragm, both in seated and supine decubitus positions. Breathing training does not provide greater ventilatory efficacy than SMR, however, in COPD patients.
[Obtaining samples of the human diaphragm during upper laparotomy. A structural analysis].
UNLABELLED: The diaphragm seems to undergo adaptive structural change in chronic obstructive pulmonary disease. The possibility of obtaining muscle specimens is limited, however, particularly when respiratory function is severely affected. OBJECTIVE: To assess the viability of a new technique for obtaining diaphragm muscle samples appropriate for structural assessment even from patients with severe functional change, and to study the size of fibers in relation to severity of disease. METHODS: Fifteen muscle specimens were obtained from patients (aged 57 +/- 15 years) by abdominal laparotomy. All had undergone full lung function testing. Muscle samples were taken during surgery using a new technique involving formation of a tobacco pouch with dome biopsy. The method had been previously validated in animal models. Later, the biopsies were processed to evaluate fiber proportions and sizes (ATPase dyes at different levels of pH). RESULTS: The 15 patients had a wide range of lung function results (FEV1 22-120% ref); 4 were severely affected (FEV1 < or = 50% ref). Nutritional status was normal in all cases; FEV1/FVC was 67 +/- 13%, RV was 134 +/- 55% ref, maximal mouth pressure (PImmax) was -75 +/- 27 cmH2O, transdiaphragmatic pressure (PIdimax) was 96 +/- 26 cmH2O, DLCO was 87 +/- 26% ref and PaO2 was 89 +/- 14 mmHg. We were able to obtain specimens valid for structural analysis from all patients with no complications. Light type I fibers predominated (54 +/- 9%) and size was normal overall (57 +/- 9 microns minimum diameter [Dm] atrophy index 195 +/- 243, and hypertrophy index 66 +/- 78), with no differences between the two fiber subtypes (Dm 58 +/- 8 microns for type I and 61 +/- 8 microns for type II). Overall size correlated inversely with static volumes (e.g. Dm with RV, r = -0.729, p < 0.01). CONCLUSIONS: The laparoscopic technique described is simple and safe for use in humans to obtain diaphragm muscle specimens that are valid for morphometric analysis, allowing us to enlarge the range of subjects that can be enrolled for this type of study. The fiber muscles studied are smaller when functional involvement is greater in chronic obstructive pulmonary disease.
Expression of myosin heavy-chain isoforms in the respiratory muscles following inspiratory resistive breathing.
We investigated the effect of inspiratory resistive breathing (IRB) on the expression of the genes encoding fast and slow isoforms of myosin heavy chain (MyHC) in respiratory muscles. Eleven mongrel dogs were studied for baseline MyHC messenger RNA (mRNA) expression, seven of which were also used to study the effects of IRB. For this latter objective, awake and spontaneously breathing animals were subjected to 2 h of IRB (80 cm H(2)O/L/s) per day for four consecutive days. mRNA expression was assessed in the diaphragm, external intercostal muscle, and a limb muscle, using both slot- blot and in situ hybridizations with isoform-specific probes. A current semiquantitative scoring method (from 0 to 4) was used to quantify the in situ mRNA expression levels, and slot-blot data were analyzed with densitometry. Prior to IRB, slow- and fast-MyHC mRNA expression was moderate, similar, and homogeneous throughout the different regions of the diaphragm, with scores of 1.50 +/- 0.54 (mean +/- SD) for slow and 2.13 +/- 0.35 for fast mRNAs in the costal region of the diaphragm, and of 1.81 +/- 0.37 for slow and 2. 13 +/- 0.64 for fast mRNAs in the crural region of the diaphragm. Although expression of fast-MyHC mRNA remained unchanged after IRB, the relative expression of the mRNA for the slow isoform increased in costal (+30%), crural (+12%), and external intercostal (+27%) muscles. MyHC mRNA expression did not change in limb muscles. We conclude that breathing with a moderate inspiratory resistance for a short period induces the expression of slow MyHC in respiratory muscles.
[Capillary density and respiratory function in the external intercostal muscle].
UNLABELLED: Changes in lung function have been related to adaptive structural modifications in respiratory muscles. OBJECTIVE: To evaluate the capillary density (Dcap) of the external intercostal muscle in patients with chronic obstructive pulmonary disease (COPD), and its possible relation to respiratory function. METHODS: Forty-two individuals (61 +/- 9 years old) underwent conventional lung function testing and evaluation of respiratory muscles (maximum pressures at rest and a tolerance test using Martyn's technique). The sample included 10 subjects with normal lung function and 32 COPD patients (FEV1 between 13 and 78% of reference), in stable phase and with no respiratory insufficiency (PaO2 > 60 mmHg). A local biopsy of the external intercostal muscle was taken from all subjects at the fifth intercostal space (anterior axillary [correction of axile]) on the non-dominant side. The sample was processed for morphometry and fiber typing with ATPase staining and for quantifying capillarity with Gomori's trichrome staining. RESULTS: The mean diameter was 61 +/- 10 micrograms, with type I fibers predominating (56 +/- 11%). Dcap was 2.8 +/- 0.6 capillaries/fiber (equivalent to 1.02 +/- 0.37 capillaries/mm2 of fibrillary surface). The number of capillaries/fiber was significantly higher in patients with severe COPD (FEV1 < 50% ref) than in controls (3.0 +/- 0.6 versus 2.3 +/- 0.5, p < 0.01) and was inversely related to FEV1 (r = -0.395, p < 0.01). Muscle capillarity was unrelated to other function variables, including markers of respiratory muscle function and gas exchange. CONCLUSION: The structural remodelling of external intercostal muscles in COPD patients also includes an increase in density of interfibrillary capillaries. This increase is proportional to the severity of obstruction and probably reflects an adaptive phenomenon.
[Respiratory muscle force and resistance in patients with SAHS. The effect of using nighttime CPAP].
UNLABELLED: During nighttime episodes of obstructive apnea in patients with sleep apnea-hypopnea syndrome (SAHS), repeated and progressive inspiratory efforts are made. Such intense nighttime activity can have a deleterious effect on daytime function of respiratory muscles. OBJECTIVE: The objective of this study was to evaluate daytime respiratory muscle function in a group of SAHS patients before and after two months of treatment with nighttime continuous positive airway pressure (CPAP). METHODS: We enrolled 12 patients with SAHS and 10 normal subjects (control group). To evaluate respiratory muscle strength we measured maximum esophageal pressure (Pesmax), transdiaphragmatic pressure (Pdimax) and inspiratory pressure in the mouth (PM). Respiratory muscle resistance was assessed using peak pressure in the mouth (PMPeak), time of tolerance (Tlim) and maximum inspiratory pressure-time index (PTimax). We also analyzed the nighttime function of respiratory muscles during apneic episodes in 10 of the 12 SAHS patients. We propose and define an index of nighttime respiratory muscle activity (RMian) as the product of the tension-time index for the diaphragm observed at the end of nighttime apneic episodes (TTdiapnea) and the apnea-hypopnea index (AHI). RESULTS: Respiratory muscle strength was similar in the two groups and no changes were observed in SAHS patients after treatment with nighttime CPAP. However, tolerance was lower in SAHS patients (PMpeak--30%, Tlim--31% and PTimax--49%). Two months of nighttime CPAP normalized all three variables in these patients. MRian was related to percent improvement in PMpeak after treatment with nighttime CPAP in SAHS patients (r = 0.66, p < 0.04). CONCLUSION: SAHS has an adverse effect on the daytime endurance of respiratory muscles that is proportional to the increase of nighttime mechanical muscle activity. The application of nighttime CPAP is restorative, probably because it allows respiratory muscles to rest.