Prevalence and outcome of pulmonary fibrosis in microscopic polyangiitis.

We sought to determine the type of pulmonary involvement in microscopic polyangiitis (MPA), primarily focusing on pulmonary fibrosis (PF), its prevalence, temporal relationship with other disease manifestations and outcome. 33 patients (16 males) with biopsy proven perinuclear anti-neutrophilic cytoplasmic antibody-positive MPA (age 63.5 yrs) participated in the study. Pulmonary involvement was assessed using standard methods, including radiographic imaging (chest radiographs and high-resolution computed tomography), pulmonary function testing, bronchoscopy and bronchoalveolar lavage, and, if indicated, lung biopsy. All-cause mortality was analysed by the Kaplan-Meier method and was compared between MPA patients with and without PF. At the time of diagnosis, renal involvement was detected in all patients, with renal biopsies being consistent with segmental necrotising glomerulonephritis in all patients. The most common respiratory symptom was haemoptysis, which was found in nine (27%) patients. PF was present in 12 (36%) patients at the time of diagnosis, whereas one patient developed PF while on therapy approximately 10 yrs after disease diagnosis. In seven patients with PF, respiratory symptoms related to fibrosis preceded other disease manifestations by a median (range) period of 13 (5-120) months. Patients were followed up for a period of 38+/-30 months. Presence of PF was associated with increased mortality (p = 0.02), with six deaths occurring in the fibrotic group and one in the nonfibrotic group. In the fibrotic group most deaths were related to PF. PF occurs frequently in MPA, may precede other disease manifestations by a variable length of time and has a poor prognosis.

Thoracoabdominal motion in ankylosing spondylitis: association with standardised clinical measures and response to therapy.

OBJECTIVES: To assess the relationship between thoracoabdominal motion during quiet breathing and standardised indices of disease severity in patients with ankylosing spondylitis (AS); also to evaluate whether thoracoabdominal motion improves after institution of biological agents in these patients. METHODS: Displacement of the rib cage (RC) and abdomen (Abd) during quiet breathing in the sitting, standing and supine position were recorded by impedance plethysmography in 60 patients (mean (SD) age 41 (10) years, 56 men) and 21 healthy men (mean (SD) 36 (7) years). x-y plots of RC versus Abd displacement during quiet breathing were constructed, and the angle of the slope of the RC-Abd loop was calculated and averaged for five consecutive breaths. In 13 patients treated with anti-tumour necrosis factor alpha (TNFalpha), measurements were made before and at 3, 6 and 12 months after the start of treatment. RESULTS: In the entire AS group, the angle of the slope of the RC-Abd loop correlated with Bath Ankylosing Spondylitis Functional Index (BASFI) in the sitting (R = -0.50, p<0.0001), standing (R = -0.36, p = 0.004) and supine (R = -0.47, p = 0.0001) position, but not with Bath Ankylosing Spondylitis Disease Activity (BASDAI), Bath Ankylosing Spondylitis Metrology Index (BASMI) or the modified Schober's test. In 13 patients treated with anti-TNFalpha, the angle of the RC-Abd slope improved significantly (35-69% over baseline at 3 months) in all body positions and in a nearly parallel fashion with the improvements in standardised clinical measurements. CONCLUSIONS: The pattern of thoracoabdominal motion during quiet breathing correlates with BASFI, and its response to anti-TNFalpha treatment is large. This variable may be an appropriate target for evaluating potential usefulness in monitoring thoracic spine involvement and response to treatment in AS.

Myocardial performance and aortic elasticity are impaired in patients with ankylosing spondylitis.

OBJECTIVE: To measure aortic stiffness and global left ventricular (LV) function in patients with ankylosing spondylitis (AS) and no clinical evidence of heart disease. METHODS: Fifty-seven consecutive patients with AS (54 males, three females, mean age 41.78+/-10.02 years) without clinical evidence of cardiac involvement and 78 healthy subjects (73 males, five females, mean age 39.92+/-9.11 years) underwent complete echocardiographic study. Aortic stiffness was determined non-invasively by aortic distensibility (AoD) and the global LV function was evaluated by the myocardial performance index (the Tei index). RESULTS: AoD in patients with AS [(2.21+/-0.24)x10(-6) cm(2) dyn(-1)] was decreased compared to controls [(2.58+/-0.19) )x10(-6) cm(2) dyn(-1), p<0.01], confirming that aortic stiffness is increased in AS. The LV Tei index was significantly increased in the patient group compared to the control group (0.392+/-0.031 vs. 0.370+/-0.034, p<0.01). The ejection fraction (EF) did not differ between the two groups (p>0.05). In multivariate linear regression analysis, AoD was significantly associated with the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and LV isovolumic relaxation time (IVRT) whereas the LV Tei index was associated with BASDAI and the LV mass index. CONCLUSIONS: Patients with AS and no clinical evidence of cardiac disease have increased stiffness of the aorta and decreased global myocardial performance and both of these abnormal measurements correlate with disease activity. The abnormal Tei index may reflect an early manifestation of cardiac dysfunction in these patients.

Occult connective tissue diseases mimicking idiopathic interstitial pneumonias.

In patients with interstitial lung disease (ILD), the diagnosis of idiopathic interstitial pneumonia is usually made after excluding, among other conditions, connective tissue diseases (CTDs). Although in most patients with a CTD and respiratory symptoms, the systemic nature of the disease is obvious, the ILD-related manifestations in CTDs may often dominate the clinical picture or precede systemic findings and thus mimic idiopathic interstitial pneumonia. With the exception of systemic lupus erythematosus, all CTDs may imitate chronic idiopathic interstitial pneumonias. In this setting, clues to an underlying CTD may be entirely absent or include subtle findings from various systems, including skin, vascular and musculoskeletal system or internal organs. Since nonspecific interstitial pneumonia is a relatively frequent histological pattern in CTDs, biopsy reports of nonspecific interstitial pneumonia should also prompt a search for an underlying CTD. Ultimately, diagnosis of a CTD requires confirmation with immunological testing; interpretation of the various laboratory tests should always be carried out in conjunction with clinical findings. The present article reviews specific clinical aspects of connective tissue disease-related interstitial lung disease that may help differentiate it from idiopathic interstitial pneumonia, especially when interstitial lung disease is the predominant or sole manifestation of an occult connective tissue disease.

Candiduria in intensive care units: association with heavy colonization and candidaemia.

Candiduria is increasingly detected in intensive care unit (ICU) patients and often coexists with candidal colonization at other anatomical sites. Studies involving surgical and medical ICU patients have consistently reported a relationship between candiduria and heavy colonization. This suggests that candiduria could be considered as a marker for heavy colonization. Risk factors that predispose to heavy colonization are generally similar to those predisposing to candidaemia. Candiduria in ICU patients is characterized by a high mortality, largely through a significant relationship with candidaemia, which in some patients may reach 50%. Therapeutic interventions should be strongly considered in the critically ill patient who presents with candiduria and concurrent clinical risk factors predisposing to dissemination.

Determinants of pulmonary function improvement in patients with scleroderma and interstitial lung disease.

BACKGROUND: In patients with scleroderma-related interstitial lung disease (ILD), improvements of pulmonary function have been reported after treatment with cyclophosphamide (CYC) alone or CYC and high-dose steroids. The study objective was to identify therapeutic regimen that alone or in combination with laboratory or clinical characteristics were associated with pulmonary function improvement in these patients. METHODS: Scleroderma patients with ILD and serial pulmonary function measurements were retrospectively analyzed. We recorded forced vital capacity (FVC, % predicted), diffusion capacity (DLCO, % predicted), type of therapy, and various clinical and laboratory parameters. Treatment with IV CYC was recorded as cumulative dose (grams) and treatment with steroids as high or low dose; outcome was defined as a sustained increase in FVC (% predicted) >or= 10 points. RESULTS: Of the 59 patients who were included in the study, 29 (49 %) patients received IV CYC (cumulative dose 13.9 +/-6.2, range 5.2-26.2 gr) for 3.3 +/- 2.4 years (range 5-60 months). Eighteen out of 59 (30 %) patients received high-dose prednisolone and 41 (70 %) received low-dose prednisolone. In an ordinal logistic model, patients receiving > 12 gr of CYC were 6 times more likely to improve FVC than to decrease or maintain FVC, compared to those who did not receive CYC (p = 0.02). In multivariate analysis, the effect of high dosage CYC on FVC persisted (OR 10.82, p = 0.02). Steroid dosage (high or low) was not associated with FVC improvement (p < 0.05). CONCLUSION: In patients with scleroderma and ILD, treatment with CYC is the only variable that is independently associated with pulmonary function improvement and that prolonged (> 1 year) CYC therapy increases the probability of pulmonary function improvement more than shorter CYC courses.

Unilateral absence of the diaphragm in an asymptomatic adult.

An asymptomatic 22-year-old man was evaluated for a persistent left lower lobe infiltrate. Barium enema and upper gastrointestinal series revealed colon and small bowel freely mobile in the left thorax. CT confirmed absence of the left hemidiaphragm. This is the first reported case of total absence of a hemidiaphragm in an adult, and extends the clinical spectrum of diaphragmatic defects where strangulation of hernia contents may occur , the asymptomatic presentation of complete absence of the hemidiaphragm with the unimpeded movement of abdominal contents suggests that no treatment is necessary.

Respiratory complications after coronary artery bypass surgery with unilateral or bilateral internal mammary artery grafting.

BACKGROUND AND STUDY OBJECTIVE: Use of bilateral internal mammary artery (IMA) grafts during coronary artery revascularization procedures carries the potential for increased incidence of postoperative respiratory complications compared with use of unilateral IMA grafts. The purpose of this study was to compare the incidence of respiratory complications such as hypoxemia, atelectasis, pleural effusion, and diaphragmatic dysfunction in patients who received one or both IMAs as conduit grafts. DESIGN: Prospective, comparative study. SETTING: Surgical ICU at a tertiary teaching hospital. PATIENTS: Seventy-five patients with bilateral and 75 patients with unilateral IMA grafts. MEASUREMENTS: Serial postoperative PaO2/fraction of inspired oxygen measurements, radiographic scores of atelectasis and pleural effusion, duration of mechanical ventilation, length of ICU and hospital stay, and incidence of pneumothorax, pneumonia, and wound infection. RESULTS: There was a higher incidence (51% vs 25%; p=0.002) and severity (0.48+/-0.09 vs 0.15+/-0.05 on the first postoperative day, 0.39+/-0.07 vs 0.27+/-0.07 on the fourth postoperative day, mean+/-SEM; p=0.004) of postoperative right lower lobe atelectasis in the group who received bilateral IMA grafts than in those who received left IMA grafts. This finding probably reflects the effects of additional surgical intervention on the right side of the chest. Incidence and severity of pleural effusion, gas exchange impairment, duration of mechanical ventilation, ICU and hospital stay, and incidence of pneumothorax, pneumonia, and wound infection were not influenced by use of bilateral IMA grafts (p>0.05). CONCLUSION: We conclude that use of bilateral IMA grafts during coronary artery revascularization does not increase the incidence of postoperative respiratory complications compared with unilateral IMA grafting.

Unexpected cardiac arrest after cardiac surgery: incidence, predisposing causes, and outcome of open chest cardiopulmonary resuscitation.

STUDY OBJECTIVES: To assess the incidence of acute mechanical causes precipitating sudden cardiac arrest in cardiac surgery patients during the immediate postoperative period. In addition, we report the success rate of cardiopulmonary resuscitation (CPR) in which open-chest CPR was employed at an early stage of the resuscitation effort. METHODS: Data on all cardiac surgical patients who suffered a sudden cardiac arrest during the first 24 h after surgery were collected prospectively. CPR consisted of conventional closed-chest CPR initially and was followed within 3 to 5 min, if needed, by open-chest CPR. RESULTS: Of 3,982 patients undergoing cardiac surgery over a 30-month period, 29 patients (0.7%) had a sudden cardiac arrest. Of these, 13 patients (45%) were successfully resuscitated with closed-chest CPR, 14 (48%) with open-chest CPR, and 2 (7%) died despite closed- and open-chest CPR. Four CPR survivors died subsequently in the ICU, yielding an overall hospital discharge rate of 79%. Perioperative myocardial infarction was the underlying cause of sudden cardiac arrest in 14 patients (48%), and mechanical impediments to cardiac function (tamponade or graft malfunction) in another 8 (28%) patients; in the remaining 7 patients (24%), no underlying cause was found. The length of ICU stay was 6+/-1 (mean+/-SE) days. None of the patients developed wound infection and all were neurologically intact at hospital discharge. CONCLUSION: Mechanical factors account for a substantial portion (28%) of causes of sudden cardiac arrest occurring in hemodynamically stable patients during the immediate postoperative period. This high incidence, in conjunction with the high survival rate achieved by open CPR, supports an early approach to open-chest CPR in this group of patients.

Preferential fatigue of the rib cage muscles during inspiratory resistive loaded ventilation.

Because the inspiratory rib cage muscles are recruited during inspiratory resistive loaded breathing, we hypothesized that such loading would preferentially fatigue the rib cage muscles. We measured the pressure developed by the inspiratory rib cage muscles during maximal static inspiratory maneuvers (Pinsp) and the pressure developed by the diaphragm during maximal static open-glottis expulsive maneuvers (Pdimax) in four human subjects, both before and after fatigue induced by an inspiratory resistive loaded breathing task. Tasks consisted of maintaining a target esophageal pressure, breathing frequency, and duty cycle for 3-5 min, after which the subjects maintained the highest esophageal pressure possible for an additional 5 min. After loading, Pinsp decreased in all subjects [control, -128 +/- 14 (SD) cmH2O; with fatigue, -102 +/- 18 cmH2O; P less than 0.001, paired t test]. Pdimax was unchanged (control, -192 +/- 23 cmH2O; fatigue, -195 +/- 27 cmH2O). These data suggest that 1) inability to sustain the target during loading resulted from fatigue of the inspiratory rib cage muscles, not diaphragm, and 2) simultaneous measurement of Pinsp and Pdimax may be useful in partitioning muscle fatigue into rib cage and diaphragmatic components.

Transmission of pressure within the abdomen.

The extent to which transmission of pressure within the abdomen is accomplished in accordance with the laws of fluid mechanics, i.e., homogeneous transmission to all portions of the abdomen, is controversial. To examine the cranial-to-caudal as well as side-to-side transmission of pressure within the abdomen in humans, we measured intra-abdominal pressure at four sites in five subjects undergoing colonoscopy. Liquid-filled catheters were inserted into the colon, and intracolonic pressure was measured in the rectum and in transverse, descending, and sigmoid colon. Differences in intracolonic pressure were recorded during breaths to total lung capacity and brief expulsive maneuvers. Measurements were taken in the supine, right lateral, and seated position. Comparison of pressure swings at all sites showed that the pressure changes were nearly equal during both inspiratory and expulsive maneuvers. The changes in pressure were uniform in the cephalocaudal axis as from side to side. We conclude that transmission of abdominal pressure in humans is nearly homogeneous. Our findings provide support for the hydraulic model of abdominal mechanics.

Oxygen cost of breathing during fatiguing inspiratory resistive loads.

When a subject breathes against an inspiratory resistance, the inspiratory pressure, the inspiratory flow, and the lung volume at which the breathing task takes place all interact to determine the length of time the task can be sustained (Tlim). We hypothesized that the mechanism actually limiting tasks in which these parameters were varied involved the rate of energy utilization by the inspiratory muscles. To test this hypothesis, we studied four experienced normal subjects during fatiguing breathing tasks performed over a range of pressures and flows and at two different lung volumes. We assessed energy utilization by measuring the increment in the rate of whole body O2 consumption due to the breathing task (VO2 resp). Power and mean esophageal pressure correlated with Tlim but depended also on lung volume and inspiratory flow rate. In contrast, VO2 resp closely correlated with Tlim, and this relationship was not systematically altered by inspiratory flow or lung volume. The shape of the VO2 resp vs. Tlim curve was approximately hyperbolic, with high rates of VO2 resp associated with short endurance times and lower rates of VO2 resp approaching an asymptotic value at high Tlim. These findings are consistent with a mechanism whereby a critical rate of energy utilization determines the endurance of the inspiratory pump, and that rate varies with pressure, flow, and lung volume.

Lung volume specificity of inspiratory muscle training.

We examined the extent to which training-related increases of inspiratory muscle (IM) strength are limited to the lung volume (VL) at which the training occurs. IM strength training consisted of performing repeated static maximum inspiratory maneuvers. Three groups of normal volunteers performed these maneuvers at one of three lung volumes: residual volume (RV), relaxation volume (Vrel), or Vrel plus one-half of inspiratory capacity (Vrel + 1/2IC). A control group did not train. We constructed maximal inspiratory pressure-VL curves before and after a 6-wk training period. For each group, we found that the greatest improvements in strength occurred at the volume at which the subjects trained and were significantly greater for those who trained at low (36% for RV and 26% for Vrel) than at high volumes (13% for Vrel + 1/2IC). Smaller increments in strength were noted at volumes adjacent to the training volume. The range of vital capacity (VC) over which strength was increased was greater for those who trained at low (70% of VC) than at high VL (20% of VC). We conclude that the greatest improvements in IM strength are specific to the VL at which training occurs. However, the increase in strength, as well as the range of volume over which strength is increased, is greater for those who trained at the lower VL.

Effect of fatigue on maximal inspiratory pressure-flow capacity.

The inspiratory muscles can be fatigued by repetitive contractions characterized by high force (inspiratory resistive loads) or high velocities of shortening (hyperpnea). The effects of fatigue induced by inspiratory resistive loaded breathing (pressure tasks) or by eucapnic hyperpnea (flow tasks) on maximal inspiratory pressure-flow capacity and rib cage and diaphragm strength were examined in five healthy adult subjects. Tasks consisted of sustaining an assigned breathing frequency, duty cycle, and either a "pressure-time product" of esophageal pressure (for the pressure tasks) or peak inspiratory flow rate (for the flow tasks). Esophageal pressure was measured during maximal inspiratory efforts against a closed glottis (Pesmax), maximal transdiaphragmatic pressure was measured during open-glottis expulsive maneuvers (Pdimax), and maximal inspiratory flow (VImax) was measured during maximal inspiratory efforts with no added external resistance before and after fatiguing pressure and flow tasks. The reduction in Pesmax) with pressure fatigue (-25 +/- 7%) was significantly greater than the change in Pesmax with flow fatigue (-8 +/- 8%, P less than 0.01). In contrast, the reductions in Pdimax (-11 +/- 8%) and VImax (-16 +/- 3%) with flow fatigue were greater than the changes in Pdimax (-0.6 +/- 4%, P less than 0.05) or VImax (-3 +/- 4%, P less than 0.05) with pressure fatigue. We conclude that respiratory muscle performance is dependent not only on the presence of fatigue but whether fatigue was induced by pressure tasks or flow tasks. The specific impairment of Pesmax and not of Pdimax or flow with pressure fatigue may reflect selective fatigue of the rib cage muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Pressure-flow specificity of inspiratory muscle training.

The inspiratory muscles (IM) can be trained by having a subject breathe through inspiratory resistive loads or by use of unloaded hyperpnea. These disparate training protocols are characterized by high inspiratory pressure (force) or high inspiratory flow (velocity), respectively. We tested the hypothesis that the posttraining improvements in IM pressure or flow performance are specific to training protocols in a way that is similar to force-velocity specificity of skeletal muscle training. IM training was accomplished in 15 normal subjects by use of three protocols: high inspiratory pressure-no flow (group A, n = 5), low inspiratory pressure-high flow (group B, n = 5), and intermediate inspiratory pressure and flow (group C, n = 5). A control group (n = 4) did no training. Before and after training, we measured esophageal pressure (Pes) and inspiratory flow (VI) during single maximal inspiratory efforts against a range of external resistances including an occluded airway. Efforts originated below relaxation volume (Vrel), and peak Pes and VI were measured at Vrel. Isovolume maximal Pes-VI plots were constructed to assess maximal inspiratory pressure-flow performance. Group A (pressure training) performed 30 maximal static inspiratory maneuvers at Vrel daily, group B (flow training) performed 30 sets of three maximal inspiratory maneuvers with no added external resistance daily, and group C (intermediate training) performed 30 maximal inspiratory efforts on a midrange external resistance (7 mm ID) daily. Subjects trained 5 days/wk for 6 wk. Data analysis included comparison of posttraining Pes-VI slopes among training groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary function and respiratory muscle strength in chronic heart failure: comparison between ischaemic and idiopathic dilated cardiomyopathy.

OBJECTIVE: To compare pulmonary function and respiratory muscle strength in patients with ischaemic and idiopathic dilated cardiomyopathy, well matched for indices of heart failure. METHODS: The study involved 30 patients with ischaemic cardiomyopathy and 30 with idiopathic dilated cardiomyopathy. The groups were well matched for age, weight, and clinical severity of cardiac dysfunction as assessed by ejection fraction and the New York Heart Association functional class. There were more smokers in the ischaemic group (p < 0.05), but indices of pulmonary function were comparable. RESULTS: Mean (SD) maximum static inspiratory pressure was lower in dilated cardiomyopathy than in ischaemic cardiomyopathy (73 (20) v 84 (22) cm H2O, p < 0.05), as was the maximum static expiratory pressure (90 (20) v 104 (21) cm H2O, p < 0.05). CONCLUSIONS: For a given degree of cardiac dysfunction, the respiratory muscles are weaker in patients with idiopathic dilated cardiomyopathy than in those with ischaemic cardiomyopathy.

Effects of severity of long-standing congestive heart failure on pulmonary function.

To investigate the effects of severity of long-standing congestive heart failure (CHF) on pulmonary function, we studied 53 (47 men) consecutive patients, all heart transplant candidates. Their mean (+/- SD) age and ejection fraction were 47 +/- 12 years and 23 +/- 7%, respectively. All patients underwent spirometry, lung volume, diffusion capacity (DLCO), maximum inspiratory (PImax) and expiratory pressure (PEmax) measurement. Maximum cardiopulmonary exercise test on a treadmill was also performed to determine maximum oxygen consumption (VO2max). On the basis of VO2max, the patients were then divided into those with a VO2max > 14 ml min-1 kg-1 (group 1, n = 30) and those with a VO2max < or = 14 ml min-1 kg-1 (group 2, n = 23). In comparison with group 1, group 2 patients had lower FEV1/FVC (70 +/- 8% vs 75 +/- 7%, P = 0.008), lower FEF25-75 (46 +/- 21 vs 70 +/- 26%pred, P < 0.001), lower TLC (76 +/- 15 vs 85 +/- 13%pred, P = 0.02) and lower PImax (68 +/- 20 vs 87 +/- 22 cmH2O, P = 0.003), but comparable DLCO (84 +/- 15 vs 88 +/- 20%pred, P = N.S.), and PEmax (99 +/- 25 vs 96 +/- 22 cmH2O, P = N.S.). In conclusion, our data suggest that respiratory abnormalities, such as restrictive defects, airway obstruction, and inspiratory muscle weakness, are more pronounced in patients with severe CHF than in those with mild-to-moderate disease. Further studies are required to investigate the extent to which these abnormalities contribute to dyspnoea during daily activities in patients with heart failure.

Pattern of breathing during progressive exercise in chronic heart failure.

This descriptive study analyzed serial, individual changes in the exercise pattern of breathing (POB) of patients with stable chronic heart failure (CHF). Twenty-two CHF patients underwent maximal, symptom-limited cardiopulmonary exercise test on a treadmill. Minute ventilation (VE), tidal volume (VT), breathing frequency (f), the ventilatory equivalent for carbon dioxide (VE/VCO2) and estimated dead-space to tidal volume ratio (VD/VT) were continuously recorded. The VE/VCO2 slope was calculated in every subject as the slope of the regression line relating VE to VCO2 during exercising testing. Pattern of breathing was investigated by constructing the individual VT-f relationship for each patient separately. In 16 (73%) patients (group 1), the VT-f plot was initially linear, but subsequently exhibited an inflection point at which VT stopped increasing with further increases in f. In six (27%) patients (group 2) no inflection point was evident on the VT-f relation; in four of these patients the VT-f relation remained linear but shifted to the right throughout testing, and two patients decreased VT before peak exercise achieving high breathing frequencies. Comparing group 1 to group 2 patients, they had higher VEmax (68+/-23 vs. 44+/-10 l/min, P=0.02) and VO2max (17+/-5 vs. 12+/-3 ml/min/kg, P=0.01). In contrast, the two groups did not differ in terms of age, weight, height, diagnosis, ejection fraction or VE/VCO2 slope. In conclusion, patients with CHF adopt variable breathing patterns during exercise; specific patterns are associated with greater impairment in functional capacity.

Inspiratory muscle training in the patient with neuromuscular disease.

Pulmonary complications due to respiratory muscle dysfunction are commonly a source of morbidity and mortality in patients with neuromuscular diseases. This review discusses the adverse effects of respiratory muscle weakness on pulmonary mechanics and examines the role that inspiratory muscle training may play in reversing pulmonary dysfunction in these individuals. In asymptomatic persons, it is well established that the inspiratory muscles can be trained to increase both force and endurance. In patients with neuromuscular diseases, the effects of training protocols on force and endurance are more controversial. This article reviews seven studies that have evaluated respiratory muscle training in a total of 75 patients with varied neuromuscular disorders. Training regimens included breathing through inspiratory resistive loads and isocapnic hyperpnea. Despite methodologic differences among studies, investigators have generally shown that the inspiratory muscles are similar to other skeletal muscle groups in that they can be trained for both force and endurance in these patients. The training-related improvements in inspiratory muscle performance are more pronounced in patients who are less severely affected by their disease. In those patients who have disease to the extent that they are already retaining carbon dioxide, there is little change in force or endurance with training. In these individuals, the inspiratory muscles may already be working at a level sufficiently severe to provide a training stimulus with each breath. No adverse effects of inspiratory muscle training were reported. Inspiratory muscle training can improve force and endurance in patients with neuromuscular weakness.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory muscle performance with stretch-shortening cycle manoeuvres: maximal inspiratory pressure-flow curves.

AIM: To test the hypothesis that the maximal inspiratory muscle (IM) performance, as assessed by the maximal IM pressure-flow relationship, is enhanced with the stretch-shortening cycle (SSC). METHODS: Maximal inspiratory flow-pressure curves were measured in 12 healthy volunteers (35 +/- 6 years) during maximal single efforts through a range of graded resistors (4-, 6-, and 8-mm diameter orifices), against an occluded airway, and with a minimal load (wide-open resistor). Maximal inspiratory efforts were initiated at a volume near residual lung volume (RV). The subjects exhaled to RV using slow (S) or fast (F) manoeuvres. With the S manoeuvre, they exhaled slowly to RV and held the breath at RV for about 4 s prior to maximal inspiration. With the F manoeuvre, they exhaled rapidly to RV and immediately inhaled maximally without a post-expiratory hold; a strategy designed to enhance inspiratory pressure via the SSC. RESULTS: The maximal inspiratory pressure-flow relationship was linear with the S and F manoeuvres (r2 = 0.88 for S and r2 = 0.88 for F manoeuvre, P < 0.0005 in all subjects). With the F manoeuvre, the pressure-flow relationship shifted to the right in a parallel fashion and the calculated maximal power increased by approximately 10% (P < 0.05) over that calculated with the S manoeuvre. CONCLUSION: The maximal inspiratory pressure-flow capacity can be enhanced with SSC manoeuvres in a manner analogous to increases in the force-velocity relationship with SSC reported for skeletal muscles.