Reliability and Validity of Maximal Respiratory Pressures.

BACKGROUND: Maximal respiratory pressure is used to assess the inspiratory and expiratory muscles strength by using maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax). This study aimed to summarize and evaluate the reliability and validity of maximal respiratory pressure measurements. METHODS: This systematic review followed the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) recommendations and was reported by using the PRISMA checklist. Studies published before March 2023 were searched in PubMed and EMBASE databases. RESULTS: A total of 642 studies were identified by using the online search strategy and manual search (602 and 40, respectively). Twenty-three studies were included. The level of evidence for test-retest reliability was moderate for PImax and PEmax (intraclass correlation coefficient > 0.70 for both), inter-rater reliability was low for PImax and very low for PEmax (intraclass correlation coefficient > 0.70 for both), and the measurement error was very low for PImax and PEmax. In addition, concurrent validity presented a high level of evidence for PImax and PEmax (r > 0.80). CONCLUSIONS: Only concurrent validity of maximal respiratory pressure measured with the manometers evaluated in this review presented a high level of evidence. The quality of clinical studies by using maximal respiratory pressure would be improved if more high-quality studies on measurement properties, by following well established guidelines and the COSMIN initiative, were available.

Chest physiotherapy for pneumonia in children.

BACKGROUND: Pneumonia is an inflammatory lung disease and it is the greatest cause of deaths in children younger than five years of age worldwide. Chest physiotherapy is widely used in the treatment of pneumonia because it can help to eliminate inflammatory exudates and tracheobronchial secretions, remove airway obstructions, reduce airway resistance, enhance gas exchange and reduce the work of breathing. Thus, chest physiotherapy may contribute to patient recovery as an adjuvant treatment even though its indication remains controversial. OBJECTIVES: To assess the effectiveness of chest physiotherapy in relation to time until clinical resolution in children (from birth up to 18 years old) of either gender with any type of pneumonia. SEARCH METHODS: We searched CENTRAL 2013, Issue 4; MEDLINE (1946 to May week 4, 2013); EMBASE (1974 to May 2013); CINAHL (1981 to May 2013); LILACS (1982 to May 2013); Web of Science (1950 to May 2013); and PEDro (1950 to May 2013).We consulted the ClinicalTrials.gov and the WHO ICTRP registers to identify planned, ongoing and unpublished trials. We consulted the reference lists of relevant articles found by the electronic searches for additional studies. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that compared chest physiotherapy of any type with no chest physiotherapy in children with pneumonia. DATA COLLECTION AND ANALYSIS: Two review authors independently selected the studies to be included in the review, assessed trial quality and extracted data. MAIN RESULTS: Three RCTs involving 255 inpatient children are included in the review. They addressed conventional chest physiotherapy, positive expiratory pressure and continuous positive airway pressure. The following outcomes were measured: duration of hospital stay, time to clinical resolution (observing the following parameters: fever, chest indrawing, nasal flaring, tachypnoea and peripheral oxygen saturation levels), change in adventitious sounds, change in chest X-ray and duration of cough in days. Two of the included studies found a significant improvement in respiratory rate and oxygen saturation whereas the other included study failed to show that standardised respiratory physiotherapy and positive expiratory pressure decrease the time to clinical resolution and the duration of hospital stay. No adverse effects related to the interventions were described. Due to the different characteristics of the trials, such as the duration of treatment, levels of severity, types of pneumonia and the techniques used in children with pneumonia, as well as differences in their statistical presentation, we were not able to pool data. Two included studies had an overall low risk of bias whereas one included study had an overall unclear risk of bias. AUTHORS' CONCLUSIONS: Our review does not provide conclusive evidence to justify the use of chest physiotherapy in children with pneumonia due to a lack of data. The number of included studies is small and they differed in their statistical presentation.

Maximal respiratory pressures: Measurements at functional residual capacity in individuals with different health conditions using a digital manometer.

BACKGROUND: Measuring maximal respiratory pressure is a widely used method of investigating the strength of inspiratory and expiratory muscles. OBJECTIVES: To compare inspiratory pressures obtained at functional residual capacity (FRC) with measures at residual volume (RV), and expiratory pressures obtained at FRC with measures at total lung capacity (TLC) in individuals with different health conditions: post-COVID-19, COPD, idiopathic pulmonary fibrosis (IPF), heart failure (CHF), and stroke; and to compare the mean differences between measurements at FRC and RV/TLC among the groups. METHODS: Inspiratory and expiratory pressures were obtained randomly at different lung volumes. Mixed factorial analysis of covariance with repeated measures was used to compare measurements at different lung volumes within and among groups. RESULTS: Seventy-five individuals were included in the final analyses (15 individuals with each health condition). Maximal inspiratory pressures at FRC were lower than RV [mean difference (95% CI): 11.3 (5.8, 16.8); 8.4 (2.3, 14.5); 11.1 (5.5, 16.7); 12.8 (7.1, 18.4); 8.0 (2.6, 13.4) for COVID-19, COPD, IPF, CHF, and stroke, respectively] and maximal expiratory pressures at FRC were lower than TLC [mean difference (95% CI): 51.9 (37.4, 55.5); 60.9 (44.2, 77.7); 62.9 (48.1, 77.8); 58.0 (43.9, 73.8); 57.2 (42.9, 71.6) for COVID-19, COPD, IPF, CHF, and stroke, respectively]. All mean differences were similar among groups. CONCLUSION: Although inspiratory and expiratory pressures at FRC were lower than measures obtained at RV/TLC for the five groups of health conditions, the mean differences between measurements at different lung volumes were similar among groups, which raises the discussion about the influence of the viscoelastic properties of the lungs on maximal respiratory pressure.

Acute effects of expiratory positive airway pressure on exercise tolerance in patients with COPD.

OBJECTIVE: To evaluate the acute effects of expiratory positive airway pressure (EPAP) on exercise tolerance, dyspnea, leg discomfort, and breathing pattern in patients with COPD. METHODS: Fifteen patients with COPD were assessed with the following three different protocols: EPAP of 7.5 cmH2O used during a constant cycle ergometer exercise test (Protocol-1); EPAP of 7.5 cmH2O used for 15 minutes before the test (Protocol-2); and a sham system without pressure used for 15 minutes before the test (Protocol-3). Dyspnea and leg discomfort were assessed using Borg scale, whereas breathing pattern by optoelectronic plethysmography. Statistical analyses were performed using generalized estimating equations and Bonferroni tests (α = 5%), considering the protocols (1, 2, and 3) and moment (resting and the end of exercise). RESULTS: Exercise tolerance was lower in protocol 1: 108 ± 45 seconds compared to protocols 2: 187 ± 99 seconds (p= .011) and 3: 183 ± 101 seconds (p= .021). No difference was observed between protocols 2 and 3 (p> .999). Dyspnea in protocol 1: 7.0 ± 2.08 was higher than protocols 2: 4.10 ± 2.45 (p= .001) and 3: 3.90 ± 2.21 (p< .001), but no differences were observed between protocols 2 and 3 (p> .999). No significant difference was observed for leg discomfort among the protocols (p= .137). There were no statistically significant differences for most variables of breathing pattern among the protocols. CONCLUSION: A reduction on exercise tolerance and an increase in dyspnea were found with EPAP of 7.5 cm H2O during a constant cycle ergometer exercise test in patients with COPD.

Inspiratory muscular training in chronic stroke survivors: a randomized controlled trial.

OBJECTIVE: To assess the effectiveness of inspiratory muscular training (IMT) on measures of strength, resistance, functional performance, and quality of life (QOL) for chronic stroke survivors. DESIGN: Double-blinded randomized controlled trial. SETTING: Research laboratory. PARTICIPANTS: Subjects (N=21) with stroke (11 men, 10 women; maximal inspiratory pressure [MIP] <90% of predicted values) were randomly assigned to the experimental (n=11) and control groups (n=10); 18 participants completed all testing and training. INTERVENTIONS: Interventions were based on home-based training, with resistance adjusted biweekly to 30% of MIP for the experimental group. The control group underwent the same protocol without the threshold resistance valve. Both groups received home training 30 minutes a day 5 times a week for 8 weeks. MAIN OUTCOME MEASURES: MIP, inspiratory muscular endurance (IME), functional performance, and QOL. RESULTS: There were significant between-group differences for the MIP and IME measures. Significant changes were observed for only the experimental group for MIP (67.8±14.6 at baseline to 102.2±26.0cmH(2)O at posttraining) and IME (31.8±19.3 to 49.2±21.1cmH(2)O). No statistically significant differences were observed for measures of functional performance and QOL. CONCLUSIONS: Significant short-term effects of the IMT program for inspiratory strength and endurance were observed in chronic stroke survivors. These findings gave some indications that IMT may benefit people with stroke, and it is feasible to be included in rehabilitation interventions with this population.

New method for evaluating maximal respiratory pressures: Concurrent validity, test-retest, and inter-rater reliability.

BACKGROUND: Maximal respiratory pressures (MRP) obtained at functional residual capacity (FRC) may reflect the real respiratory muscle pressure. OBJECTIVES: To evaluate concurrent validity, test-retest, and inter-rater reliability of MRP performed with a new instrument in healthy individuals, and to compare values obtained at different volumes in healthy individuals and individuals with COPD. METHODS: MRP of 100 healthy individuals were obtained using the TrueForce and the MicroRPM® at residual volume (RV) and total lung capacity (TLC) to evaluate concurrent validity. MRP were obtained at FRC using the TrueForce to evaluate reliability. Comparisons of inspiratory pressure values (FRC compared to RV) and expiratory pressure values (FRC compared to TLC) were performed with 100 healthy individuals and 15 individuals with COPD. RESULTS: The intraclass correlation coefficient (ICC) was 0.77 and 0.86 for concurrent validity for inspiratory and expiratory pressures, respectively. Test-retest reliability showed an ICC of 0.87 for inspiratory pressure, and 0.78 for expiratory pressure; inter-rater reliability showed an ICC of 0.91 for inspiratory pressure, and 0.84 for expiratory pressure. Measurements performed at RV and TLC were higher when compared to FRC [mean difference (95%CI)= -8.30 (-11.82, -4.78) cmH2O; -37.29 (-42.63, -31.96) cmH2O] in healthy individuals, and -11.09 (-15.83, -6.35) cmH2O; -57.14 (-71.05, -43.05) cmH2O in COPD, for inspiratory and expiratory pressures, respectively. CONCLUSION: MRP performed with the TrueForce presented good concurrent validity, good test-retest reliability, excellent inter-rater reliability for inspiratory pressure and good inter-rater reliability for expiratory pressure. MRP were lower when obtained at FRC for healthy individuals and with COPD.

Inspiratory muscle training reduces dyspnea during activities of daily living and improves inspiratory muscle function and quality of life in patients with advanced lung disease.

Aim: To evaluate the effects of an inspiratory muscle training (IMT) program on dyspnea during activities of daily living, inspiratory muscle function, functional capacity, and quality of life in patients with advanced lung disease (ALD).Methods: Pre-post interventional study in which patients with ALD from the Advanced Lung Disease and Pre Lung Transplantation Ambulatory Clinic were included. Patients performed home-based high-intensity interval IMT for 8 weeks (two sessions per day, daily). In each session, patients performed two sets of 30 breaths, with a 2-min rest between sets. Dyspnea during activities of daily life, primary outcome - assessed by the London Chest Activity of Daily Living scale-LCADL, inspiratory muscle function (MIP and endurance test), distance on the 6-min walking test [6MWD], and quality of life (St George Respiratory Questionnaire [SGRQ]) were measured pre-IMT, post-IMT, and 3 months after the intervention (follow-up).Results: Dyspnea during activities of daily living significantly decreased after 8 weeks of IMT (LCADLpre = 31.5 [IQR = 23-37.25], LCADLpost = 26 [IQR = 20.75-32], LCADLfollow-up = 30.5 [IQR = 20-35]; p < .03). After IMT, there was an improvement in inspiratory muscle strength (p < .001) and endurance (p < .001). Functional capacity evaluated using the 6MWD increased but did not reach significance (p = .79) There was also a significant improvement in quality of life, as demonstrated by the SGRQ (p < .004).Conclusions: Our results suggest that IMT was able to reduce dyspnea during activities of daily living, as well as improve inspiratory muscle function, and quality of life in patients with ADL, and these benefits were sustained for 3 months.

Effects of inspiratory muscle training on resting breathing pattern in patients with advanced lung disease.

AIM: The aim of this study was to evaluate the effects of interval high intensity inspiratory muscle training (IMT) on resting breathing pattern in patients with advanced lung disease. METHODS: IMT was performed daily and training load set at 50 % of the maximal inspiratory pressure. Participants were evaluated at pre-IMT, post 8 weeks of IMT and follow-up (3 months after the end of IMT). Breathing pattern (volume and time variables as well as percentages of contribution to tidal volume) was evaluated by Optoelectronic Plethysmography at rest. Friedman test was used to verify the differences between the three time-points (p < 0.05). RESULTS: Nineteen patients (54 ± 16 years old; 5 males) were evaluated at pre-IMT and post-IMT and fourteen were assessed at follow-up. There was no significant difference (p > 0.05) in any comparison for all evaluated breathing pattern variables at the three time-points. CONCLUSION: Resting breathing pattern was not significantly changed after 8 weeks of IMT in patients with advanced lung disease.

Early CPAP protocol in preterm infants with gestational age between 28 and 32 weeks: experience of a public hospital.

BACKGROUND: The use of continuous positive airway pressure (CPAP) applied early after birth improves several outcomes when compared with intubation and invasive mechanical ventilation. "Early CPAP" protocols vary in relation to the pressure level, type of interface used, and studied sample. OBJECTIVE: This study compared intubation rate, exogenous surfactant use, and hospitalization length (among other variables) prior to and after adopting an "early CPAP" protocol in preterm infants with gestational age between 28 and 32 weeks, using intermediate pressures and short binasal prongs. METHODS: This was a retrospective study conducted in a public university hospital in Brazil. All preterm infants with gestational age between 28 and 32 weeks were included in the study. The newborns born between January 2011 and December 2012, prior to the protocol being implemented, were considered the historical control group, and those born after implementation, between February 2013 and August 2014 were considered the intervention group. RESULTS: The participants in both groups had similar baseline characteristics (p > 0.05). There were significant reductions in intubation rate (89% versus 73%, p = 0.02), exogenous surfactant use (86% versus 67%, p = 0.02), and median (Q1 - Q3) days of invasive mechanical ventilation [4 (2 - 14) versus 1 (0.15-9), p = 0.01] and length of hospital stay in days [56 (42-77) versus 42 (35-71), p = 0.02]. CONCLUSIONS: The findings demonstrate positive outcomes of the early CPAP protocol. This protocol used simple and affordable equipment available in the hospital which could easily be reproduced in other centers, generating better outcomes for preterm infants and reducing hospital expenses.

Rib cage distortion and dynamic hyperinflation during two exercise intensities in people with COPD.

BACKGROUND: The relationship between rib cage (RC) motion abnormalities, dynamic hyperinflation (DH), and exercise capacity in people with COPD is controversial. AIM: To investigate RC distortion and operational chest wall volumes during moderate and high constant-rate exercises in people with COPD. METHODS: Seven male participants [median(Q1-Q3) age: 63(60.0-66.0) years; FEV1: 39.0(38.0-63.0)% of predicted] performed a symptom-limited incremental exercise testing on cycle ergometer, followed by constant-rate tests (60 % and 80 % of peak work rate). Optoelectronic plethysmography was used to evaluate RC distortion: phase angle-PhAng, inspiratory phase ratio-PhRIB, expiratory phase ratio-PhREB; and chest wall volumes: end-inspiratory volume-Vei and end-expiratory volume-Vee. RESULTS: PhRIB and PhREB significantly increased during both constant-rate exercise tests, without difference between them. In general, Vei of the chest wall significantly increased in both exercise intensities while Vee did not change. CONCLUSIONS: The occurrence of RC distortion seemed not to limit the exercise capacity in people with COPD evaluated, and it was present even in the absence of DH.

Reference values of sniff nasal inspiratory pressure in healthy children.

OBJECTIVE: To determine reference values of sniff nasal inspiratory pressure (SNIP) in healthy children. METHODS: This cross-sectional observational study included healthy children aged 6 to 11 years of both sexes. The volunteers underwent a pulmonary function test to rule out respiratory disorders. Respiratory muscle strength was measured using maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP), respectively, with MIP close to functional residual capacity (FRC) and residual volume, while MEP to total lung capacity. SNIP was performed through the nostril contralateral to the occlusion, close to FRC. Two 6-minute walk tests were performed to assess functional exercise capacity. RESULTS: The sample comprised 121 healthy children (62 girls); 54% presented body mass index (BMI) percentile less than 85th and 46% more than equal to 85th percentile, higher than expected. SNIP values were similar between sexes (91.1 ± 21.0 cmH2 O in girls and 87.7 ± 19.4 cmH2 O in boys; P = .36) as well as the means of lower limits of normal (56.88 cmH2 O for girls and 56.66 cmH2 O for boys). Girls presented SNIP measurements larger than those of the MIP of FRC (P < .0001), while boys presented similar mean values for both. We found a positive correlation between SNIP and BMI percentile (r = .25, P = .04) in girls, unlike boys, in whom no correlation was observed. CONCLUSIONS: SNIP reference values and mean lower limits of normal were defined for healthy children aged 6 to 11. BMI percentile seems to positively influence the inspiratory muscle strength measured by SNIP in girls only.

Sustained maximal inspiration has similar effects compared to incentive spirometers.

PURPOSE: To compare the effects of flow incentive spirometer (FIS), volume incentive spirometer (VIS), and sustained maximal inspiration exercise (SMI) on breathing pattern, chest wall motion, and thoracoabdominal asynchrony. METHODS: Sixteen healthy adults aged 27.63 ± 5.26 years were evaluated by optoelectronic plethysmography in the supine position with trunk inclination of 45° during quiet breathing and during exercise performance. RESULTS: In the comparisons among exercises, VIS promoted a significantly higher inspiratory time and lower mean inspiratory flow compared with FIS. The rating of perceived exertion according to the Borg Scale was significantly higher after the performance of FIS compared with VIS. Regarding asynchrony, none of the exercises caused changes in thoracoabdominal synchrony between the rib cage and abdomen. However, both devices significantly reduced the asynchrony between the pulmonary and abdominal rib cage compared with quiet breathing. CONCLUSION: SMI exercise was equivalent to incentive spirometers and may be an interesting alternative for clinical use in cases in which it is not possible to acquire the devices.

Effects of Diaphragmatic Breathing With and Without Pursed-Lips Breathing in Subjects With COPD.

BACKGROUND: Breathing exercises, such as diaphragmatic breathing and pursed-lips breathing, play a role in some individuals with COPD and might be considered for those patients who are unable to exercise. However, in the literature are reports of some adverse effects of diaphragmatic breathing in patients with COPD. Thus, the purpose of this study was to assess the effects of diaphragmatic breathing and diaphragmatic breathing combined with pursed-lips on chest wall kinematics, breathlessness, and chest wall asynchrony in subjects with COPD, and also to assess whether the combination of both exercises reduces the adverse effects of diaphragmatic breathing while maintaining its benefits. METHODS: Seventeen subjects with COPD, mean ± SD, 65 ± 7 y of age, with a history of smoking and clinical stability without hospitalization or symptoms of exacerbation in the past 4 wk, were evaluated. On day 1, participants' characteristics were collected, and they learned diaphragmatic breathing and its combination with pursed-lips breathing. On day 2, the participants were evaluated by optoelectronic plethysmography with the participants in the seated position while performing breathing exercises. RESULTS: Diaphragmatic breathing and diaphragmatic breathing plus pursed-lips breathing promoted a significant increase in chest wall tidal volume and its compartments as well as a reduction in breathing frequency compared with quiet breathing. No significant changes were observed in dyspnea or end-expiratory volume of the chest wall. A significant increase in asynchrony (inspiratory-expiratory phase ratio) was observed during diaphragmatic breathing and diaphragmatic breathing plus pursed-lips breathing compared with quiet breathing, with no differences observed between the exercises. CONCLUSIONS: Despite the increase in asynchrony, both breathing exercises were able to improve chest wall volumes without affecting dyspnea. The combination of exercises maintained the benefits but did not reduce the adverse effects of diaphragmatic breathing.

The effects of inspiratory muscle training based on the perceptions of patients with advanced lung disease: a qualitative study.

BACKGROUND: Advanced lung disease is a chronic non-neoplastic disease that compromises activities of daily living. Treatment includes pulmonary rehabilitation and inspiratory muscle training. Studies have shown the effectiveness of inspiratory muscle training in lung disease patients, but literature is scarce on the patients' perceptions about this topic. OBJECTIVE: To explore the perceptions of patients with advanced lung disease about inspiratory muscle training. METHODS: Qualitative study. Interviews were conducted using a semi-structured questionnaire regarding topics on the participation of patients in inspiratory muscle training and on daily activities performed before and after training. Interviews were transcribed and analyzed according to thematic content analysis. RESULTS: Ten patients (eight women and 2 men, ranging in age from 27 to 89 years) with inspiratory muscle weakness (maximal inspiratory pressure=44±13.9cmH2O) were included. Five patients were diagnosed with Chronic Obstructive Pulmonary Disease, two with bronchiectasis and three with pulmonary fibrosis. All patients completed at least 80% of the total training sessions. The reports were grouped into four thematic categories: (1) impact of inspiratory muscle training on breathlessness (e.g., "I wasn't feeling as tired as I previously felt."); (2) change in daily activities (e.g., "I needed to go to the supermarket, I felt less tired doing it."); (3) improved mobility (e.g., "I could not stand for long periods […] walking, for example […] Now I stand more, I have more capability."); and (4) increased communication (e.g., "More power, right? Even in speaking […] When I could, I felt my voice coming out better."). CONCLUSION: There were improvements in breathlessness, daily activities, mobility, and communication, which positively affected the psychological and social aspects of the patients.

Nebulization associated with bi-level noninvasive ventilation: analysis of pulmonary radioaerosol deposition.

UNLABELLED: Nebulization associated with noninvasive ventilation is used in emergency services and intensive care units. PURPOSES: To compare pulmonary radioaerosol deposition during jet nebulization associated to noninvasive ventilation versus spontaneous breathing nebulization; to measure the rate of lung depuration and the correlation between lung deposition, inspiratory flow and tidal volume (V(t)) using scintigraphy. SUBJECTS: Thirteen healthy volunteers (with normal spirometry), mean age (23.3+/-1.49) years, body mass index 21.2+/-2.3 kg/m(2). METHODS: Nebulization was performed in spontaneous breathing and associated with bi-level noninvasive ventilation (inspiratory pressure=12 cm H(2)O, expiratory pressure=5 cm H(2)O). The radioaerosol used in the nebulization was technetium (Tc99m) with diethylene triamine penta acetic acid, generated over a period of 9 min in a jet nebulizer. Analysis was performed through scintigraphy. Statistical analysis was performed by analysis of variance (for repeated measures), Bonferroni method, Student's t-test and Person's correlation. RESULTS: There was a decrease in radioaerosol lung deposition with nebulization associated to noninvasive ventilation (mean counts in spontaneous breathing 200,510+11,012 and mean counts in noninvasive ventilation 106,093+2811 (P<0.001). During spontaneous breathing nebulization there was a significant correlation between V(t) and radioaerosol deposition (r=0.565, P<0.05), also between inspiratory flow and radioaerosol deposition in the lungs (r=0.141, P<0.05). However, there was no correlation between V(t) and pulmonary deposition of radioaerosol in bi-level noninvasive ventilation nebulization (r=0.082). CONCLUSION: During nebulization with noninvasive ventilation in healthy volunteers, there was an increase in V(t) associated to a higher inspiratory flow rate, without resulting in a significant increase in pulmonary radioaerosol deposition.

Effects of non-invasive ventilation and posture on chest wall volumes and motion in patients with amyotrophic lateral sclerosis: a case series.

BACKGROUND: The effects of non-invasive ventilation (NIV) on the breathing pattern and thoracoabdominal motion of patients with amyotrophic lateral sclerosis (ALS) are unknown. OBJECTIVES: 1) To analyze the influence of NIV on chest wall volumes and motion assessed by optoelectronic plethysmography in ALS patients and 2) to compare these parameters in the supine and sitting positions to those of healthy individuals (without NIV). METHOD: Nine ALS patients were evaluated in the supine position using NIV. In addition, the ALS patients and nine healthy individuals were evaluated in both sitting and supine positions. Statistical analysis was performed using the paired Student t-test or Wilcoxon test and the Student t-test for independent samples or Mann-Whitney U test. RESULTS: Chest wall volume increased significantly with NIV, mean volume=0.43 (SD=0.16)L versus 0.57 (SD=0.19)L (p=0.04). No significant changes were observed for the pulmonary rib cage, abdominal rib cage, or abdominal contribution. The index of the shortening velocity of the diaphragmatic muscle, mean=0.15 (SD=0.05)L/s versus 0.21 (SD=0.05)L/s (p<0.01), and abdominal muscles, mean=0.09 (SD=0.02)L/s versus 0.14 (SD=0.06)L/s (p<0.01), increased during NIV. Comparisons between the supine and sitting positions showed similar changes in chest wall motion in both groups. However, the ALS patients presented a significantly lower contribution of the abdomen in the supine position compared with the controls, mean=56 (SD=13) versus 69 (SD=10) (p=0.02). CONCLUSIONS: NIV improved chest wall volumes without changing the contribution of the chest wall compartment in ALS patients. In the supine position, ALS patients had a lower contribution of the abdomen, which may indicate early diaphragmatic dysfunction.

Muscle impairment in neuromuscular disease using an expiratory/inspiratory pressure ratio.

BACKGROUND: Neuromuscular diseases (NMDs) lead to different weakness patterns, and most patients with NMDs develop respiratory failure. Inspiratory and expiratory muscle strength can be measured by maximum static inspiratory pressure (PImax) and maximum static expiratory pressure (PEmax), and the relationship between them has not been well described in healthy subjects and subjects with NMDs. Our aim was to assess expiratory/inspiratory muscle strength in NMDs and healthy subjects and calculate PEmax/PImax ratio for these groups. METHODS: Seventy (35 males) subjects with NMDs (amyotrophic lateral sclerosis, myasthenia gravis, and myotonic dystrophy), and 93 (47 males) healthy individuals 20-80 y of age were evaluated for anthropometry, pulmonary function, PImax, and PEmax, respectively. RESULTS: Healthy individuals showed greater values for PImax and PEmax when compared with subjects with NMDs. PEmax/PImax ratio for healthy subjects was 1.31 ± 0.26, and PEmax%/PImax% was 1.04 ± 0.05; for subjects with NMDs, PEmax/PImax ratio was 1.45 ± 0.65, and PEmax%/PImax% ratio was 1.42 ± 0.67. We found that PEmax%/PImax% for myotonic dystrophy was 0.93 ± 0.24, for myasthenia gravis 1.94 ± 0.6, and for amyotrophic lateral sclerosis 1.33 ± 0.62 when we analyzed them separately. All healthy individuals showed higher PEmax compared with PImax. For subjects with NMDs, the impairment of PEmax and PImax is different among the 3 pathologies studied (P < .001). CONCLUSIONS: Healthy individuals and subjects with NMDs showed higher PEmax in comparison to PImax regarding the PEmax/PImax ratio. Based on the ratio, it is possible to state that NMDs show different patterns of respiratory muscle strength loss. PEmax/PImax ratio is a useful parameter to assess the impairment of respiratory muscles in a patient and to customize rehabilitation and treatment.

Non-invasive ventilation and sleep.

In this paper, we review the effects of nocturnal mechanical ventilation on sleep. Indeed, although non-invasive assisted ventilation during sleep has been applied extensively, the exact effects of this treatment on sleep quality have not been thoroughly studied. In patients with severe chronic obstructive pulmonary disease and severe restrictive ventilatory defects, the resulting respiratory failure is aggravated by the specific effects of sleep on respiration. Non-invasive mechanical ventilation can lead to improvements in both ventilation and sleep quality. However, this is not always the case. Moreover, sleep-related leaks may jeopardize the efficiency of the ventilatory assistance which in turn may result in a deterioration in sleep quality. Non-invasive mechanical ventilation, if applied during sleep, should require a monitoring procedure during sleep with the aim of obtaining the best possible effects both on ventilation and on sleep quality.

Effects of hypocapnic hyperventilation on the response to hypoxia in normal subjects receiving intermittent positive-pressure ventilation.

OBJECTIVE: To confirm the hypothesis that the ventilatory response to hypoxia (VRH) may be abolished by hypocapnia. METHODS: We studied four healthy subjects during intermittent positive-pressure ventilation delivered through a nasal mask (nIPPV). Delivered minute ventilation (Ed) was progressively increased to lower end-tidal carbon dioxide pressure (PETCO(2)) below the apneic threshold. Then, at different hypocapnic levels, nitrogen was added to induce falls in oxygen saturation, a hypoxic run (N(2) run). For each N(2) run, the reappearance of a diaphragmatic muscle activity and/or an increase in effective minute ventilation (E) and/or deformations in mask-pressure tracings were considered as a VRH, whereas unchanged tracings signified absence of a VRH. For the N(2) runs eliciting a VRH, the threshold response to hypoxia (TRh) was defined as the transcutaneous oxygen saturation level that corresponds to the beginning of the ventilatory changes. RESULTS: Thirty-seven N(2) runs were performed (7 N(2) runs during wakefulness and 30 N(2) runs during sleep). For severe hypocapnia (PETCO(2) of 27.1 +/- 5.2 mm Hg), no VRH was noted, whereas a VRH was observed for N(2) runs performed at significantly higher PETCO(2) levels (PETCO(2) of 34.0 +/- 2.1 mm Hg, p < 0.001). Deep oxygen desaturation (up to 64%) never elicited a VRH when the PETCO(2) level was < 29.3 mm Hg, which was considered the carbon dioxide inhibition threshold. For the 16 N(2) runs inducing a VRH, no correlations were found between PETCO(2) and TRh and between TRh and both Ed and E. CONCLUSION: During nIPPV, VRH is highly dependent on the carbon dioxide level and can be definitely abolished for severe hypocapnia.

Effects of intermittent negative pressure ventilation on effective ventilation in normal awake subjects.

RATIONALE: Previous studies have shown that an increase in inspiratory pressure during nasal intermittent positive pressure ventilation (IPPV) does not result in increased effective minute ventilation (E) due to glottic interference. STUDY OBJECTIVES: To test the consequences of increases in negative pressure ventilation (NPV) on V(E). MATERIAL AND METHODS: Eight healthy awake subjects underwent NPV delivered by an iron lung. First, NPV was started at a respirator frequency (f) of 15 cycles per minute with an inspiratory negative pressure (INP) of - 15 cm H(2)O (F15-P15). Then, f was increased to 20 cycles per minute and INP was kept at - 15 cm H(2)O. Next, f was kept at 20 cycles per minute and INP was reduced to - 30 cm H(2)O (F20-P30). Finally, f was decreased to 15 cycles per minute and INP was kept at - 30 cm H(2)O. At each step and for each breath, effective tidal volume (VT), V(E), and end-tidal carbon dioxide pressure were measured. In three subjects, the glottis width was assessed using fiberoptic bronchoscopy. RESULTS: From spontaneous breathing to the first step of NPV (F15-P15), we observed an inhibition of the phasic inspiratory diaphragmatic electromyogram concomitant to a significant increase in V(E) (p < 0.0005). For the group as a whole, the increase in mechanical ventilation (from F15-P15 to F20-P30) resulted in significant increases in VT and V(E) leading to hypocapnia (p < 0.0005). Moreover, the glottis width did not decrease with the increase in mechanical ventilation. CONCLUSIONS: We conclude that in normal awake subjects, NPV allowed a significant increase in V(E). These results differ from those previously obtained with nasal IPPV in which the glottic width interferes with the delivered mechanical ventilation.