Respiratory pressures and function in young adults

Cerebral Arterial and Venous Air Embolism Following Removal of Percutaneous Sheath Introducer

Cerebral air embolism after removal of central venous catheter (CVC) is a rare complication but can lead to fatal outcomes. We report a rare case of both cerebral venous and arterial embolism occurring in a patient with underlying scleroderma-related interstitial lung disease (SSc-ILD) and pulmonary hypertension following removal of percutaneous introducer sheath for pulmonary artery catheterization. We discuss the mechanisms, pathophysiology, management and prevention of cerebral air embolism.

Methods and Applications in Respiratory Physiology: Respiratory Mechanics, Drive and Muscle Function in Neuromuscular and Chest Wall Disorders

Individuals with neuromuscular and chest wall disorders experience respiratory muscle weakness, reduced lung volume and increases in respiratory elastance and resistance which lead to increase in work of breathing, impaired gas exchange and respiratory pump failure. Recently developed methods to assess respiratory muscle weakness, mechanics and movement supplement traditionally employed spirometry and methods to evaluate gas exchange. These include recording postural change in vital capacity, respiratory pressures (mouth and sniff), electromyography and ultrasound evaluation of diaphragmatic thickness and excursions. In this review, we highlight key aspects of the pathophysiology of these conditions as they impact the patient and describe measures to evaluate respiratory dysfunction. We discuss potential areas of physiologic investigation in the evaluation of respiratory aspects of these disorders.

Pulmonary function testing in neuromuscular disease

Neuromuscular disorders frequently compromize pulmonary function and effective ventilation, and a thorough respiratory evaluation often can assist in diagnosis, risk assessment, and prognostication. Since many of these disorders can be progressive, serial assessments may be necessary to best define a trajectory of impairment or improvement with therapy. Patients with neuromuscular diseases may have few respiratory symptoms and limited signs of skeletal muscle weakness, but can have significant respiratory muscle weakness. A single testing modality may fail to elucidate true respiratory compromise, and often a combination of tests is recommended to fully evaluate these patients. Common tests performed in this population include measurement of flow rates, lung volumes, maximal pressures, and airways resistance. This review covers the major respiratory testing modalities available in the evaluation of these patients, emphasizing both the benefits and shortcomings of each approach. The majority of parameters are available in a standard pulmonary laboratory (flows, volumes, static pressures), although referral to a specialized center may be necessary to conclusively evaluate a given patient.

How Many Maneuvers Should We Do for Maximal Inspiratory and Expiratory Muscle Pressure Testing in Children: A Retrospective Review in Children with Cystic Fibrosis

OBJECTIVES

Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) could be useful clinical parameters in monitoring many conditions including cystic fibrosis (CF). However, current protocols for undertaking the measurements lack standardization including the number of repeated attempts to achieve best values. We aimed to (a) determine the optimum number of attempts to achieve best MIP/MEP values, and (b) evaluate if the number of attempts is consistent across two different test days.

METHODS

We analyzed data of a previous randomized controlled trial involving the effect of singing on respiratory muscle strength in 35 children with CF. On two different days (T1, T2) children performed MIP/MEP with at least ten attempts each to achieve < 10% repeatability.

RESULTS

All children achieved repeatable MIP/MEP values within 10-11 attempts with 24 (68.6%) and 26 (74.3%) of these achieving best values of MIP and MEP, respectively, at attempts 6-11. Median values of the pressures by three, five, eight and all attempts significantly increased with more attempts (all p < 0.05). At T2, 56% required fewer attempts to achieve best values, but 32% required more attempts, indicating that the number of attempts required was inconsistent between test days.

CONCLUSION

It is likely that at least ten attempts (best two within < 10% variability) is required to achieve best and reliable MIP/MEP in children with CF. A larger sample size in children with CF and various conditions is required to consolidate these findings.

Predictive equations of maximum respiratory mouth pressures: A systematic review

BACKGROUND

Maximum inspiratory (Pimax) and expiratory (Pemax) mouth pressures are commonly used to detect respiratory muscle weakness resorting to predictive equations established for healthy people. There are several predictive equations, but they are widespread in the literature. This study aimed to review the existent predictive equations of maximum inspiratory (Pimax) and expiratory (Pemax) mouth pressures for adults. Additionally, we aimed to identify which ones were generated based on international standards.

METHODS

A systematic review of predictive equations of Pimax and Pemax for healthy adults was conducted. A comprehensive search was performed of Cochrane Library, EBSCO, PubMed, Scopus and Web of Science to identify studies that presented at least one equation for Pimax or Pemax developed for healthy adults. The quality of studies was assessed by two reviewers with the Quality Assessment of Diagnostic Accuracy Studies (Quadas-2).

RESULTS

Risk of bias was high in 8 of the 20 studies included. Forty-two Pimax and 34 Pemax equations were found, mostly using the variables age (n=39), weight (n=20) and height (n=8). These equations explained 3 to 96% of the Pimax/Pemax variance. They were developed with individuals from 11 countries (Portugal not included). Twelve Pimax and eight Pemax equations complied with international standards.

CONCLUSIONS

This review gathered the predictive equations that have been developed for both Pimax and Pemax, however most were generated from unstandardized procedures. Future studies should explore the suitability of these equations for populations for which specific ones are not available, such as the Portuguese population, and develop new equations if necessary.

Utility of maximum inspiratory and expiratory pressures as a screening method for respiratory insufficiency in slowly progressive neuromuscular disorders

The aim of this study was to assess whether different cut-offs of maximum inspiratory and/or expiratory pressure (MIP/MEP) are valuable screening parameters to detect restrictive respiratory insufficiency. Spirometry, MIP, MEP and capillary blood gas analysis were obtained from patients with confirmed neuromuscular disorders. We calculated regression analysis, sensitivity, specificity and predictive values. We enrolled 29 patients with myotonic dystrophy type 1 (DM1), 19 with late-onset Pompe disease (LOPD), and 24 with spinal muscular atrophy type 3. Moderate to high reduction in manometry was exclusively found in LOPD and DM1 patients. Significant associations were found between manometry and spirometry. Highest adjusted r² was found for MIP % predicted and forced vital capacity (FVC) % predicted. Manometry predicted abnormal FVC and forced expiratory volume 1 s (FEV1). MEP > 80 cmH₂O predicted normal FVC and FEV1, regardless of cut-off values. MIP and MEP did not positively predict alterations in capillary blood gas analysis. Disease-specific cut-offs of manometry did not increase the prediction rate of patients with abnormal FVC and FEV1. Predicted values should be calculated for a more comprehensive interpretation of manometry results. MIP and MEP can serve as a screening parameter for patients with neuromuscular disorders, but parallel testing of both MIP and MEP needs to be performed to increase the positive prediction probability across disease groups.

Maximal Static Respiratory and Sniff Pressures in Healthy Children. A Systematic Review and Meta-Analysis

RATIONALE

Respiratory muscle strength in children can be assessed by maximal inspiratory pressures (MIP), maximal expiratory pressures (MEP), and sniff nasal inspiratory pressures (SNIP). However, previous studies involved small cohorts of healthy children and reported wide reference ranges.

OBJECTIVES

To perform a systematic review to summarize existing reference ranges for MIP, MEP, and SNIP tests in healthy children and to conduct a meta-analysis to develop comprehensive prediction equations.

DATA SOURCES

Five databases were searched for relevant studies from database inception to May 29, 2017.

DATA EXTRACTION

Study inclusion was limited to publications that evaluated MIP, MEP, and SNIP values in healthy children aged 18 years or younger. Studies were also excluded if testing methodology differed greatly from the 2002 American Thoracic Society Statement on Respiratory Muscle Testing. Requests for raw data were made to authors via e-mail.

SYNTHESIS

A total of 18 studies including 3,509 children were systematically reviewed. Diagnostic accuracy of the included studies was assessed using the QUADAS-2 tool, which revealed a high risk of bias for flow and timing and for applicability that may influence the generalizability of our findings. All 18 studies evaluated respiratory pressures in children in seated position. MIP tests were conducted from residual volume, MEP tests from total lung capacity, and SNIP tests from functional residual capacity. The MIP and MEP values in three age groups for boys and girls were summarized using meta-analysis based on individual participant data from five studies containing 1,709 healthy children. Further analyses showed that MIP and MEP were significantly greater in boys than in girls (P < 0.0001). In both sexes, MEP values were always greater than MIP values (P < 0.05). Multivariable random effects models were then performed to establish sex-specific prediction equations. These equations found age, height, and weight to be significant predictor variables. Only two studies with SNIP values from healthy children were included in the review, but they were not part of the meta-analysis.

CONCLUSIONS

We summarized the available reference ranges for MIP, MEP, and SNIP tests based on existing literature, especially for three age groups, and developed prediction equations that can be used in pulmonary function laboratories to aid clinicians. Existing literature on SNIP tests is limited, and future studies are encouraged to explore their use in children. Systematic review registered with the International Prospective Register of Systematic Reviews (PROSPERO; CRD42017072004).

Pulmonary Function Testing in Neuromuscular and Chest Wall Disorders

Neuromuscular and chest wall disorders frequently compromise pulmonary function, and thorough respiratory evaluation often can assist in diagnosis, risk assessment, and prognosis. Because many of these disorders can be progressive, serial assessments are necessary to best define a trajectory of impairment (or improvement with therapy). This article covers the major respiratory testing modalities available in the evaluation of these patients, emphasizing both the benefits and shortcomings of each approach. Most parameters are available in a standard pulmonary laboratory (flows, volumes, static pressures), although referral to a specialized center may be necessary to conclusively evaluate a given patient.

Association between inspiratory muscle weakness and slowed oxygen uptake kinetics in patients with chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) may have poor inspiratory muscle function, which reduces minute and alveolar ventilation, leading to increased hypoxemia and slow pulmonary oxygen uptake kinetics. However, little is known about the effect of inspiratory muscle weakness (IMW) on oxygen uptake kinetics in patients with COPD. Thus, we tested the hypothesis that COPD patients with IMW have slowed oxygen uptake kinetics. An observational study was conducted that included COPD patients with moderate to severe airflow limitation and a history of intolerance to exercise. Participants were divided into 2 groups: (IMW+; n = 22) (IMW–; n = 23) of muscle weakness. The maximal inspiratory, expiratory, and sustained inspiratory strength as well as the maximal endurance of the inspiratory muscles were lower in IMW+ patients (36 ± 9.5 cm H2O; 52 ± 14 cm H2O; 20 ± 6.5 cm H2O; 94 ± 84 s, respectively) than in IMW– patients (88 ± 12 cm H2O; 97 ± 28 cm H2O; 82.5 ± 54 cm H2O; 559 ± 92 s, respectively; p < 0.05). Moreover, the 6-min walk test and peak oxygen uptake were reduced in the IMW+ patients. During the constant work test, oxygen uptake kinetics were slowed in the IMW+ compared with IMW– patients (88 ± 29 vs 61 ± 18 s, p < 0.05). Our findings demonstrate that inspiratory muscle weakness in COPD is associated with slowed oxygen uptake kinetics, and thus, reduced functional capacity.

Determining the relationship of kinesiophobia with respiratory functions and functional capacity in ankylosing spondylitis

Ankylosing spondylitis (AS) is a common inflammatory rheumatic disease that affects the axial skeleton, causes inflammatory lower back pain, and structural and functional disorders, which affect quality of life negatively.The purpose of this study is to investigate the effects of kinesiophobia in AS on pulmonary function tests (PFTs) and functional performance.Thirty-one individuals with AS (n = 19 male, n = 12 female) who were suitable on the basis of the Modified New York (MNY) criteria were included in the study. The participants were given the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the Bath Ankylosing Spondylitis Functional Index (BASFI), the Bath Ankylosing Spondylitis Metrology Index (BASMI), in addition to the Tampa Scale for Kinesiophobia (TKS), PFTs, respiratory muscle strength, pain evaluation, and 6-minute walking test (6MWT).The mean values were found as the following: TKS, 41.65 ± 7.59; pain visual analog scale (VAS) score, 6.23 ± 2.86; forced vital capacity (%) (FVC), 75.35% ± 17.92%; forced expiratory volume in first second (%) (FEV1), 73.45% ± 17.20%; FEV1/FVC (%), 75.58% ± 15.99%; peak expiratory flow (%) (PEF), 54,90% ± 20.21%; forced expiratory flow at 25% to 75% (FEF25-75), 77.71% ± 27.05%; maximal inspiratory pressure (MIP), 62.06 ± 31.68; maximal expiratory pressure (MEP), 95.94 ± 36.60; 6MWT, 445.88 ± 99.48. The scores obtained in TKS were found related to the values of FVC (%), FEV1 (%), chest expansion, BASFI, modified Schober test, lumbar lateral flexion, cervical rotation, and total BASMI score (r = -0.43, -0.36, -0.41, 0.42, -0.49, -0.56, -0.52, 0.56, respectively; P < .05).Kinesiophobia is a condition that may arise in individuals with AS, which has negative effects. Physiotherapists have a responsibility to eliminate kinesiophobia beliefs and prefer therapy method in line with this responsibility.

Maximal respiratory pressure in healthy Japanese children

[Purpose] Normal values for respiratory muscle pressures during development in Japanese children have not been reported. The purpose of this study was to investigate respiratory muscle pressures in Japanese children aged 3–12 years. [Subjects and Methods] We measured respiratory muscle pressure values using a manovacuometer without a nose clip, with subjects in a sitting position. Data were collected for ages 3–6 (Group I: 68 subjects), 7–9 (Group II: 86 subjects), and 10–12 (Group III: 64 subjects) years. [Results] The values for respiratory muscle pressures in children were significantly higher with age in both sexes, and were higher in boys than in girls. Correlation coefficients were significant at values of 0.279 to 0.471 for each gender relationship between maximal respiratory pressure and age, height, and weight, respectively. [Conclusion] In this study, we showed pediatric respiratory muscle pressure reference value for each age. In the present study, values for respiratory muscle pressures were lower than Brazilian studies. This suggests that differences in respiratory muscle pressures vary with ethnicity.

Diaphragm Dysfunction: Diagnostic Approaches and Management Strategies

The diaphragm is the main inspiratory muscle, and its dysfunction can lead to significant adverse clinical consequences. The aim of this review is to provide clinicians with an overview of the main causes of uni- and bi-lateral diaphragm dysfunction, explore the clinical and physiological consequences of the disease on lung function, exercise physiology and sleep and review the available diagnostic tools used in the evaluation of diaphragm function. A particular emphasis is placed on the clinical significance of diaphragm weakness in the intensive care unit setting and the use of ultrasound to evaluate diaphragmatic action.

Effects of bariatric surgery on inspiratory muscle strength

Background

The respiratory function is affected by obesity due to an increased deposition of fat on the chest wall. The objective of this study was to investigate the strength of the inspiratory respiratory muscles of obese individuals and the possible influence of bariatric surgery on it by measuring the maximum inspiratory pressure (MIP).

Methods

Patients referred to a bariatric centre between the 3rd of October 2011 and the 3rd of May 2012 were screened preoperatively by a multidisciplinary team. Their MIP was measured at screening and 3, 6 and 9 months postoperative. In case of a preoperative MIP lower than 70% of predicted pressure training was provided supervised by a physiotherapist.

Results

The mean age of 124 included patients was 42.9 ± 11.0 years and mean BMI was 43.1 ± 5.2 kg/m². The mean predicted MIP preoperatively was 127 ± 31 in cm H₂O and the mean measured MIP was 102 ± 24 in cm H₂O. Three patients (2.4%) received training. Three months after surgery the MIP was 76 ± 26 cm H₂O, after 6 months 82 ± 28 cm H₂O and after 9 months 86 ± 28 cm H₂O. All postoperative measurements were significant lower than preoperatively (P < 0.05). The only influencing factor for the preoperative MIP was age (p = 0.014).

Conclusion

The preoperative MIP values were significantly lower than the predicted MIP values, probably due to altered respiratory mechanics.

Maximal respiratory pressures of healthy children: comparison between obtained and predicted values

PURPOSE

To compare maximal inspiratory and expiratory pressures (PImax and PEmax, respectively) obtained in Brazilian children who are healthy with reference and predicted values from previous studies.

METHODS

Respiratory muscle strength of 144 children (63 boys), aged 7 to 11 years, was assessed. A digital manovacuometer was used to measure PImax and PEmax from residual volume and total lung capacity, respectively. Children were assessed in the sitting position while wearing a nose clip.

RESULTS

Mean values of PImax for boys and girls were 81.6 ± 20.2 and 66.1 ± 19.5 cmH2O, respectively. Mean values of PEmax in boys and girls were 95.6 ± 21.1 and 78.9 ± 19.7 cmH2O, respectively.

CONCLUSIONS

Published reference values demonstrated a wide diversity across age groups studied, and published equations were not successful in predicting maximal respiratory pressures; thus, the assessment of respiratory muscle strength of children should consider the minimization of ethnic and methodological differences.

Reference values for maximal inspiratory pressure: a systematic review

BACKGROUND

Maximal inspiratory pressure (MIP) is the most commonly used measure to evaluate inspiratory muscle strength. Normative values for MIP vary significantly among studies, which may reflect differences in participant demographics and technique of MIP measurement.

OBJECTIVE

To perform a systematic review with meta-analyses to synthesize MIP values that represent healthy adults.

METHODS

A systematic literature search was conducted using Medline, EMBASE, Cochrane, Cumulative Index to Nursing and Allied Health (CINAHL) and Sport Discus databases. Two reviewers identified and selected articles, and abstracted data. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool. A random-effects model was used to calculate overall means and 95% CIs.

RESULTS

Of 22 included articles, MIP data were synthesized according to age group and sex from six reports (n=840) in the meta-analyses. The mean QUADAS score was 3.5 of 7. The age range was between 18 and 83 years (426 men, 414 women). MIP began to decrease with age in the 40 to 60 years age range and continued to fall progressively with age. For the same age group, men tended to have higher MIPs than women. Sensitivity analysis of withdrawing studies from the meta-analysis identified one study that contributed more to heterogeneity in some age groups.

DISCUSSION

MIP was higher in men and decreased with age, which was initially apparent in middle age. Several characteristics of participants and MIP technique influence values in healthy individuals.

CONCLUSIONS

The present meta-analysis provides normative MIP values that are reflective of a large sample (n=840) and likely represents the broadest representation of participant characteristics compared with previous reports of normative data.

Effects of body positions on respiratory muscle activation during maximal inspiratory maneuvers

We evaluated the maximal mouth inspiratory pressure and the EMG patterns of major respiratory and accessory muscles used in the generation of voluntary inspiratory maneuvers during different body positions. Ten healthy subjects (F/M-4/6), the mean age 22.000B10.6 years, participated in the study. The maximal inspiratory mouth pressure (MIP) during Müller's maneuver was measured from residual volume in the standing, sitting, right-sided (RSL) and left-sided lying (LSL), supine, and head-down-tilt (HDT) (3000B0; relatively horizon) positions. EMG of the diaphragmatic (D), parasternal (PS), sternocleidomastoid (SM), and genioglossus (GG) muscles were assessed in each body position. The baseline MIP was 105.3 00B1; 12.0 in men and 59.9 00B110.1 cmH(2)O in women in the standing position and did not appreciable differ in the other positions, except the HDT where it was lower by 23 and 27% in men and women, respectively (P003C0.05). During Müllers maneuver, diaphragmatic EMG activity also was similar in all the body positions, but it was significantly enhanced in the HDT. In contrast, PS EMG showed the highest level of activation in the standing position, taken as the control, reference level, and was lower in the HDT. Activation of SM during the maneuver was near the control in the sitting position, lower in the supine (79%), RSL (85%), LSL (80%), and HDT (72%) positions (P 003C0.05). GG EMG was significantly greater during maximal inspiratory effort in the supine and HDT positions (125and 130%, respectively), while it was lower in the sitting, LRS, and LLS positions (76, 57, and 43%) compared with standing (P 003C; 0.05). We conclude that the inspiratory pressure generated during Muller maneuver is a reflection of complex interactions between several muscle groups during changes in body positions.

Characterization of maximal respiratory pressures in healthy children

BACKGROUND

Measurements of maximal voluntary inspiratory (PI(max)) and expiratory (PE(max)) pressures are used in the management of respiratory muscle disease. There is little data on the appropriate reference range, success rates, or repeatability of PI(max) and PE(max) in children or on methodological factors affecting test outcomes.

OBJECTIVES

To determine PI(max) and PE(max) in healthy children and examine which published reference equations are best suited to a contemporary population. Secondary objectives were to assess within-test repeatability and the influence of lung volumes on PI(max) and PE(max).

METHODS

Healthy children were prospectively recruited from the community on a volunteer basis and underwent spirometry, static lung volumes, and PI(max) and PE(max) testing.

RESULTS

Acceptable and repeatable (to within 20%) PI(max) and PE(max) were obtained in 156 children, with 105 (67%) children performing both PI(max) and PE(max) measurements to within 10% repeatability. The reference equations of Wilson et al. [Thorax 1984;39:535-538] best matched our healthy Caucasian children. There was an inverse relationship between PI(max) and the percent of total lung capacity (TLC) at which the measurement was obtained (beta coefficient -0.96; 95% CI -1.52 to -0.39; p = 0.001), whereas at lung volumes of >80% TLC PE(max) was independent of lung volume (p = 0.26).

CONCLUSION

We demonstrated that the Wilson et al. [Thorax 1984;39:535-538] reference ranges are most suited for contemporary Caucasian Australasian children. However, robust multiethnic reference equations for maximal respiratory pressures are required. This study suggests that 10% within-test repeatability criteria are feasible in clinical practice, and that the use of lung volume measurements will improve the quality of maximal respiratory pressure measurements.

Oral magnesium supplementation in children with cystic fibrosis improves clinical and functional variables: a double-blind, randomized, placebo-controlled crossover trial

BACKGROUND

Magnesium is one of the most important minerals in the body. Although some studies reported that patients with cystic fibrosis (CF) lack magnesium, no international study has assessed the importance of oral magnesium supplementation in CF patients.

OBJECTIVE

We prospectively investigated the long-term effect of oral magnesium supplementation on respiratory muscle strength by using manuvacuometry and the Shwachman-Kulczycki (SK) score among children and adolescents with CF.

DESIGN

This double-blind, randomized, placebo-controlled crossover study included 44 CF patients (aged 7-19 y; 20 males) who were randomly assigned to receive magnesium (n = 22; 300 mg/d) or placebo (n = 22) for 8 wk with a 4-wk washout period between trials. All patients were undergoing conventional treatment of CF. The experimental protocol included clinical evaluation, assessment of urinary concentration of magnesium, and manuvacuometric measurements [maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP)]. MIP was the primary outcome.

RESULTS

Urinary magnesium increased after the administration of magnesium (change: 36.38 mg/d after magnesium compared with 0.72 mg/d after placebo; P < 0.001). Moreover, MIP and MEP significantly improved only after magnesium administration (change in MIP: 11% predicted after magnesium compared with 0.5% predicted after placebo; change in MEP: 11.9% predicted after magnesium compared with 0.8% predicted after placebo; P < 0.001 for both). Magnesium administration had a beneficial effect on clinical variables assessed by the SK score (change: 4.48 points after magnesium compared with -1.30 points after placebo; P < 0.001).

CONCLUSION

Oral magnesium supplementation helped improve both the SK score and respiratory muscle strength in pediatric patients with CF.

Equações preditivas e valores de normalidade para pressões respiratórias máximas na infância e adolescência

OBJETIVO: Pesquisar equações preditivas e valores de normalidade para pressões respiratórias máximas disponíveis na literatura para a faixa etária compreendida entre a infância e a adolescência. FONTES DE DADOS: Estudos publicados em inglês e em português no período entre 1980 e 2009. As bases de dados eletrônicas Lilacs e Medline foram consultadas utilizando-se as palavras-chave "capacidade respiratória máxima", "músculos respiratórios", "valores de referência", "adolescente" e "criança". SÍNTESE DOS DADOS: Foram incluídos oito artigos na revisão, totalizando 1.463 crianças e adolescentes avaliados. A faixa etária da população estudada variou de sete a 18 anos. Geralmente o indivíduo é avaliado na posição sentada e com um clipe nasal. Os esforços máximos são realizados a partir do volume residual e da capacidade pulmonar total e sustentados por um a três segundos. Valores de normalidade e equações de predição foram propostos em oito e dois estudos, respectivamente. Nestes, demonstra-se incremento nas pressões respiratórias máximas desde a infância à adolescência e a ocorrência de maiores valores de pressão expiratória máxima quando comparados à pressão inspiratória máxima em crianças e adolescentes de ambos os sexos. CONCLUSÕES: As pressões respiratórias máximas constituem um meio efetivo para avaliar a força muscular respiratória e diversos fatores contribuem para a grande variedade de equações preditivas e de valores de normalidade disponíveis. É preciso buscar um consenso para normatizar os métodos requeridos ao avaliar a força muscular respiratória em crianças e adolescentes.

Normative values for maximal respiratory pressures in an Indian Mangalore population: A cross-sectional pilot study

Objective:

The objective of the pilot study is to obtain normal maximal inspiratory and expiratory pressures for individuals in the age group 20-70 years in the Mangalore population and to predict normal values according to age, sex, height, and weight using the regression equation.

Materials and Methods:

Two hundred and fifty subjects were selected through a convenient method of sampling. Fifty subjects each were enrolled in the following age groups: 20 to 29, 30 to 39, 40 to 49, 50 to 59, and 60 to 70. Each group had 50 subjects (males-25 and females-25). Baseline data such as height, weight, body mass index were recorded. Maximal inspiratory pressure (PI) and expiratory pressure (PE) were determined following standardized protocol.

Result:

With regard to PI max and PE max, the measured values were significantly lower than those recorded in previous studies for both males (30%) and females (20%). We found that age served as the best factor for the prediction of PI max and PE max in both genders.

Conclusion:

The results of this study can be used to predict respiratory muscle strength in healthy adult subjects, and the strategy employed in this study will serve as a useful, simple, reproducible, rapid assessment of respiratory muscle function and also aid the planning of treatment.

New reference values for maximal respiratory pressures in the Brazilian population

OBJECTIVE

To compare MIP and MEP determined in healthy subjects with those predicted using the equations proposed in another study, and, if necessary, to suggest new equations for MIP and MEP to be used in the Brazilian population.

METHODS

The study sample comprised 60 healthy males and 60 healthy females, 20-80 years of age (20 subjects per ten-year age bracket). Maximal respiratory pressures were determined following a standardized protocol.

RESULTS

Regarding MIP, the measured values were significantly lower than those predicted for both males (31%) and females (24%). There were no significant differences between measured and predicted MEP in either gender. We found that age presented the greatest power to predict MIP and MEP in both genders. New equations were proposed.

CONCLUSIONS

The previously proposed equations were unable to predict MIP and MEP for all of the subjects in our sample. Therefore, the results of this study can facilitate the prediction of respiratory muscle strength in healthy adult subjects in Brazil. Further studies, involving subjects from different regions of the country, could lead to the development of better tables or equations for maximal respiratory pressures in the Brazilian population.

Reference values for respiratory pressures in a general adult population--results of the Study of Health in Pomerania (SHIP)

BACKGROUND AND OBJECTIVE

Respiratory muscle pressures have been gaining increasing interest because of prognostic value. The study aim was to acquire reference values for respiratory pressures in a large-scale population-based survey--the Study of Health in Pomerania (SHIP).

METHODS

One thousand eight hundred and nine participants (885 men) of a cross-sectional epidemiologic survey, called 'Study of Health in Pomerania--SHIP', underwent lung function and respiratory muscle pressure measurements. After excluding individuals with cardiopulmonary disorders, prediction equations for men and women were established by quantile regression analysis.

RESULTS

The final study population comprised 912 individuals (432 men), aged 25-80 years. The study provides a representative set of sex-specific prediction equations of respiratory muscle strength. Respiratory pressures are decreasing with age and are lower in women when compared to men.

CONCLUSIONS

Prediction equations for relevant respiratory pressures are given. Based on this well-described population-based survey with extensive cardiopulmonary investigations to exclude relevant interfering disorders a sufficient comprehensive set of reference values was obtained.

Respiratory muscle pressures in non-CF bronchiectasis: Repeatability and reliability

Background: Respiratory muscle strength is used diagnostically in clinical practice and as an outcome measure in clinical trials in various chronic lung diseases. There is limited data on its repeatability in people with non-CF bronchiectasis. The aim of the present study was to assess the repeatability of maximal inspiratory (P Imax) and expiratory pressures (PEmax) in a group of patients with stable, moderate-to-severe non-CF bronchiectasis. Methods: Twenty participants with stable moderate-to-severe non-CF bronchiectasis were recruited. Respiratory muscle strength measurements (three maximal inspiratory and expiratory pressures) were made on 2 separate days. A standard protocol was used, including practice tests, before obtaining three technically acceptable and reproducible readings with a difference of 10% or less between values. Clinical trial registration number: ClinicalTrials.gov: NCT00487149. Results: The mean (SD) age of the non-CF bronchiectasis group was 63 (9) years. Maximal inspiratory pressures were repeatable with mean (SD) for highest PImax, Test 1 and Test 2, 75.90 (20) and 79.40 (19) cmH2O, and limits of agreement (mean difference ± 2SD) —3.50 ± 20 cmH2O, (p = 0.14). Maximal expiratory pressures differed significantly with mean (SD) for highest PEmax, Test 1 and Test 2, 102.25 (27) and 112.30 (32) cmH 2O, and limits of agreement (mean difference ± 2SD) —10.10 ± 35 cmH2O, (p = 0.02). The intraclass correlation coefficient (95% CI) for highest PImax and PEmax was 0.93 (95% CI 0.82 to 0.97) and 0.90 (95% CI 0.76 to 0.96), respectively. Conclusion: Maximal inspiratory pressure measurements were repeatable during a period of clinical stability in moderate-to-severe non-CF bronchiectasis, suggesting this may be a useful outcome measure in non-CF bronchiectasis. Once a baseline has been established, a second visit is not required. PEmax was not a repeatable measure and further study is necessary to ascertain how much practice testing is required to obtain an accurate value.

Passage of pathogenic microorganisms through breathing system filters used in anaesthesia and intensive care

SUMMARY

Invasive ventilation poses a risk of respiratory infection that can be drug-resistant. One means of reducing transmission of infection is the use of a breathing system filter. Filters are intended to be used with dry gas. Current international standards do not require that filters prevent bacterial transfer when wet. It is not known whether microorganisms pass through wet filters, but theory predicts that this might occur. We tested six filters from three different manufacturers. We passed a suspension of microorganisms through the filters using the least pressure necessary, and incubated a sample of the filtrate on blood agar. All the filters tested allowed free passage of both Candida albicans and coagulase-negative staphylococci. The median (IQR [range]) pressure required for fluid to flow across the filter varied greatly between different filter types (20 (0-48 [0-138]) cmH(2)O). We conclude that even large microorganisms pass across moist breathing system filters in conditions that are found in clinical practice.

Evaluation of maximal inspiratory pressure, tracheal airway occlusion pressure, and its ratio in the weaning outcome

PURPOSE

The objective of this study is to evaluate the predictive performance of maximal inspiratory pressure (Pimax), airway occlusion pressure (P 0.1), and its ratio (P 0.1/Pimax) in the weaning outcome.

MATERIALS AND METHODS

Seventy patients on mechanical ventilation for more than 24 hours, who fulfilled weaning criteria, were prospectively evaluated. Pimax less than -25 cm H(2)O, P 0.1 less than 4.2 cm H(2)O, and P 0.1/Pimax less than 0.14 were evaluated in all patients before spontaneous breathing trials. The receiver operating characteristic (ROC) curve was calculated to evaluate the predictive performance of each index.

RESULTS

Pimax presented the area under the ROC curves smaller than those for P 0.1 and P 0.1/Pimax (0.52 x 0.76 and 0.52 x 0.78; P = .004 and P = .0006, respectively), being the criteria of worst performance. P 0.1/Pimax presented excellent predictive performance in weaned patients, with sensitivity of 98.08, but with the area under the ROC curves only slightly larger than those for P 0.1 (0.78 x 0.76, respectively; P = .69).

CONCLUSION

In our study, P 0.1 and P 0.1/Pimax ratio were moderately accurate, whereas Pimax was less accurate in predicting the weaning outcome.

Longitudinal association of body mass index with lung function: the CARDIA study

BACKGROUND

Lung function at the end of life depends on its peak and subsequent decline. Because obesity is epidemic in young adulthood, we quantified age-related changes in lung function relative to body mass index (BMI).

METHODS

The Coronary Artery Risk Development in Young Adults (CARDIA) study in 1985-86 (year 0) recruited 5,115 black and white men and women, aged 18-30. Spirometry testing was conducted at years 0, 2, 5 and 10. We estimated 10 year change in FVC, FEV1 and FEV1/FVC according to baseline BMI and change in BMI within birth cohorts with initial average ages 20, 24, and 28 years, controlling for race, sex, smoking, asthma, physical activity, and alcohol consumption.

MEASUREMENTS AND MAIN RESULTS

Participants with baseline BMI < 21.3 kg/m2 experienced 10 year increases of 71 ml in FVC and 60 ml in FEV1 and neither measure declined through age 38. In contrast, participants with baseline BMI > or = 26.4 kg/m2 experienced 10 year decreases of 185 ml in FVC and 64 ml in FEV1. FEV1/FVC increased with increasing BMI. Weight gain was also associated with lung function. Those who gained the most weight over 10 years had the largest decrease in FVC, but FVC increased with weight gain in those initially thinnest. In contrast, FEV1 decreased with increasing weight gain in all participants, with maximum decline in obese individuals who gained the most weight during the study.

CONCLUSION

Among healthy young adults, increasing BMI in the initially thin participants was associated with increasing then stable lung function through age 38, but there were substantial lung function losses with higher and increasing fatness. These results suggest that the obesity epidemic threatens the lung health of the general population.

Maximal respiratory static pressures in patients with different stages of COPD severity

BACKGROUND

In this study, we analyzed maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) values in a stable COPD population compared with normal subjects. We evaluated the possible correlation between functional maximal respiratory static pressures and functional and anthropometric parameters at different stages of COPD. Furthermore, we considered the possible correlation between airway obstruction and MIP and MEP values.

SUBJECT AND METHODS

110 patients with stable COPD and 21 age-matched healthy subjects were enrolled in this study. Patients were subdivided according to GOLD guidelines: 31 mild, 39 moderate and 28 severe.

RESULTS

Both MIP and MEP were lower in patients with severe airway impairment than in normal subjects. Moreover, we found a correlation between respiratory muscle function and some functional and anthropometric parameters: FEV1 (forced expiratory volume in one second), FVC (forced vital capacity), PEF (peak expiratory flow), TLC (total lung capacity) and height. MIP and MEP values were lower in patients with severe impairment than in patients with a slight reduction of FEV1.

CONCLUSION

The measurement of MIP and MEP indicates the state of respiratory muscles, thus providing clinicians with a further and helpful tool in monitoring the evolution of COPD.

Diabetic polyneuropathy is associated with respiratory muscle impairment in type 2 diabetes

AIMS/HYPOTHESIS

Diabetes has a major negative effect on intensive care unit outcome. This has been partly attributed to impaired respiratory neuromuscular function. However, data on respiratory neuromuscular involvement in diabetes are lacking. This study therefore aimed to assess respiratory neuromuscular function related to diabetic polyneuropathy in patients with type 2 diabetes.

METHODS

Respiratory neuromuscular function was assessed by the use of volitional tests and twitch mouth (TwPmo) and twitch transdiaphragmatic (TwPdi) pressures during non-volitional bilateral anterior magnetic phrenic nerve stimulation in 21 male type 2 diabetic patients without pulmonary disease and in 23 healthy, well-matched controls (forced expiratory volume in 1 s 103 +/- 11 vs 103 +/- 12% predicted; p = 0.9).

RESULTS

Both volitionally assessed maximal inspiratory and expiratory mouth pressures, and sniff nasal and transdiaphragmatic pressures were comparable between diabetic patients and controls (p > 0.1 for all). TwPmo was reduced in diabetic patients compared with controls (1.3 +/- 0.5 vs 1.0 +/- 0.4 kPa; p = 0.04), while TwPdi was comparable (1.7 +/- 0.5 vs 1.6 +/- 0.7 kPa; p = 0.6). Following subgroup analysis, patients with no or mild polyneuropathy (n = 10) as assessed by neurological disability scoring had normal respiratory neuromuscular function, whereas patients with moderate or severe polyneuropathy (n = 11) presented with markedly impaired respiratory neuromuscular function as indicated by TwPmo (1.3 +/- 0.4 vs 0.8 +/- 0.3 kPa; p = 0.01) and TwPdi (1.9 +/- 0.6 vs 1.1 +/- 0.4 kPa; p < 0.01).

CONCLUSIONS/INTERPRETATION

With regard to volitional tests, diabetes does not affect respiratory neuromuscular function. In contrast, the application of non-volitional phrenic nerve stimulation provides strong evidence that diabetic polyneuropathy, as simply assessed by neurological disability scoring, is associated with substantially impaired respiratory neuromuscular function in type 2 diabetic patients.

Impairment of respiratory muscle function in pulmonary hypertension

It has been suggested that impaired respiratory muscle function occurs in patients with PH (pulmonary hypertension); however, comprehensive investigations of respiratory muscle function, including the application of non-volitional tests, needed to verify impairment of respiratory muscle strength in patients with PH have not yet been performed. In the present study, respiratory muscle function was assessed in 31 patients with PH (20 females and 11 males; mean pulmonary artery pressure, 51±20 mmHg; median World Health Organization class 3.0±0.5; 25 patients with pulmonary arterial hypertension and six patients with chronic thromboembolic PH) and in 31 control subjects (20 females and 11 males) well-matched for gender, age and BMI (body mass index). A 6-min walking test was performed to determine exercise capacity. Volitionally assessed maximal inspiratory (7.5±2.1 compared with 6.2±2.8 kPa; P=0.04) and expiratory (13.3±4.2 compared with 9.9±3.4 kPa; P<0.001) mouth pressures, sniff nasal (8.3±1.9 compared with 6.6±2.2 kPa; P=0.002) and transdiaphragmatic (11.3±2.5 compared with 8.7±2.5 kPa; P<0.001) pressures, non-volitionally assessed twitch mouth (1.46±0.43 compared with 0.97±0.41 kPa; P<0.001) and transdiaphragmatic (2.08±0.55 compared with 1.47±0.72 kPa; P=0.001) pressures during bilateral anterior magnetic phrenic nerve stimulation were markedly lower in patients with PH compared with control subjects. Maximal inspiratory mouth (r=0.58, P<0.001) and sniff transdiaphragmatic (r=0.43, P=0.02) pressures were correlated with the 6-min walking distance in patients with PH. In conclusion, the present study provides strong evidence that respiratory muscle strength is reduced in patients with PH compared with well-matched control subjects. Furthermore, the 6-min walking distance is significantly linked to parameters assessing inspiratory muscle strength.

The value of multiple tests of respiratory muscle strength

BACKGROUND

Respiratory muscle weakness is an important clinical problem. Tests of varying complexity and invasiveness are available to assess respiratory muscle strength. The relative precision of different tests in the detection of weakness is less clear, as is the value of multiple tests.

METHODS

The respiratory muscle function tests of clinical referrals who had multiple tests assessed in our laboratories over a 6-year period were analysed. Thresholds for weakness for each test were determined from published and in-house laboratory data. The patients were divided into three groups: those who had all relevant measurements of global inspiratory muscle strength (group A, n = 182), those with full assessment of diaphragm strength (group B, n = 264) and those for whom expiratory muscle strength was fully evaluated (group C, n = 60). The diagnostic outcome of each inspiratory, diaphragm and expiratory muscle test, both singly and in combination, was studied and the impact of using more than one test to detect weakness was calculated.

RESULTS

The clinical referrals were primarily for the evaluation of neuromuscular diseases and dyspnoea of unknown cause. A low maximal inspiratory mouth pressure (Pimax) was recorded in 40.1% of referrals in group A, while a low sniff nasal pressure (Sniff Pnasal) was recorded in 41.8% and a low sniff oesophageal pressure (Sniff Poes) in 37.9%. When assessing inspiratory strength with the combination of all three tests, 29.6% of patients had weakness. Using the two non-invasive tests (Pimax and Sniff Pnasal) in combination, a similar result was obtained (low in 32.4%). Combining Sniff Pdi (low in 68.2%) and Twitch Pdi (low in 67.4%) reduced the diagnoses of patients with diaphragm weakness to 55.3% in group B. 38.3% of the patients in group C had expiratory muscle weakness as measured by maximum expiratory pressure (Pemax) compared with 36.7% when weakness was diagnosed by cough gastric pressure (Pgas), and 28.3% when assessed by Twitch T10. Combining all three expiratory muscle tests reduced the number of patients diagnosed as having expiratory muscle weakness to 16.7%.

CONCLUSION

The use of single tests such as Pimax, Pemax and other available individual tests of inspiratory, diaphragm and expiratory muscle strength tends to overdiagnose weakness. Combinations of tests increase diagnostic precision and, in the population studied, they reduced the diagnosis of inspiratory, specific diaphragm and expiratory muscle weakness by 19-56%. Measuring both Pimax and Sniff Pnasal resulted in a relative reduction of 19.2% of patients falsely diagnosed with inspiratory muscle weakness. The addition of Twitch Pdi to Sniff Pdi increased diagnostic precision by a smaller amount (18.9%). Having multiple tests of respiratory muscle function available both increases diagnostic precision and makes assessment possible in a range of clinical circumstances.

The cortico-diaphragmatic pathway involvement in amyotrophic lateral sclerosis: neurophysiological, respiratory and clinical considerations

Cortico-diaphragmatic pathway was investigated by means of transcranial magnetic stimulation (TMS), in 14 patients affected by definite amyotrophic lateral sclerosis (ALS) without clinical signs of respiratory impairment. Spirometry, gas analysis, and measurement of static inspiratory and expiratory pressures were performed in all patients. Forced vital capacity, forced expiratory volume at the first and second peak expiratory flow, sniff effort from FRC level (SNIP), maximal inspiratory and expiratory pressure at mouth (MIP/MEP), maximal transdiaphragmatic pressure (Pdimx) were considered. TMS was performed, recording by surface electrodes from hemidiaphragm, bilaterally. Latency of cortical and spinal motor-evoked potentials (Cx-MEP/Sp-MEP) and central motor conduction time (CMCT) were measured. None of the patients showed altered spirometry and gas levels. Seven patients showed decreased Pdimx and eight of MEP values. Four patients showed a delayed Sp-MEP. In one patient the Cx-MEP was abolished while the mean values of both Cx-MEP and CMCT were significantly increased (19.2+/-4.1 ms, P<0.0001; 10.8+/-4.8 ms, P<0.0001). Cx-MEP and CMCT did not show significant correlations with any of the respiratory measures. The patients with prolonged Sp-MEP, showed longer disease duration, lower Norris score, lower Pdimx and MEP values. In conclusion, cortico-diaphragmatic study is a sensitive measure to reveal subclinical diaphragmatic impairment although not correlated to respiratory measures.

Which pulmonary volume should be used in physiotherapy to obtain higher maximal inspiratory pressure in COPD patients?

BACKGROUND AND PURPOSE

Patients with chronic obstructive pulmonary disease (COPD) present pulmonary hyperinflation as the main cause of mechanical disadvantages in respiratory muscles. Measurement of the force generated by those muscles is converted into pressure changes. The aim of the present study was to evaluate the maximal inspiratory pressure (MIP) from the residual volume (RV) and from the functional residual capacity (FRC), in patients with COPD, and to determine which pulmonary volume should be used in physiotherapy so as to obtain higher MIP results.

METHOD

An investigation of 18 male patients with stable COPD. Patients were examined using a manual vacuometer to measure the MIP of 20 daily manoeuvres. Ten measurements were taken from the RV and 10 from the FRC, taken alternately with an interval of 1 minute between each measurement, for five consecutive days.

RESULTS

Increases in MIP were obtained from the RV measurements (mean +/- SE) from 59.7 (+/- 5.2) to 66.6 (+/- 5.3) cm H2O (F(4,64) = 3.34; p < 0.015) and from the FRC measurements, from 55.4 (+/- 4.9) to 64.4 (+/- 4,8) cm H2O (F(4,64) = 6.72; p < 0.001). Post hoc analysis showed an increase, over consecutive days, in both RV and FRC. For FRC, an increase was revealed on the second and third days, a fall was found on the fourth day and a new increase was found on the last day. MIP reached different levels, between RV and FRC, on the first (t = 2.888; p = 0.010) and fourth (t = 2.165; p = 0.045) days.

CONCLUSION

In the present study, MIP reached higher levels at FRC during the five days of evaluation, and a learning effect occurred in the patients. Motor units from the respiratory muscles may have been recruited in order to perform the manoeuvres during the days of evaluation. The study suggests that there is good evidence for the use of the FRC as a parameter to find the major MIP value.

Assessing inspiratory muscle strength by sniff nasal inspiratory pressure

The sniff nasal inspiratory pressure (SNIP) consists in the measurement of pressure through an occluded nostril during sniffs performed through the controlateral nostril. It is an accurate and noninvasive approximation of esophageal pressure swing during sniff maneuvers. However SNIP can underestimate esophageal pressure swing in subjects with nasal obstruction, patients with chronic obstructive pulmonary disease and severe neuromuscular patients. Nevertheless, since SNIP maneuver has predicted normal values, is noninvasive and is easier to perform than maximal inspiratory pressure (MIP) maneuver, it could be considered as the first simple test to use in order to assess inspiratory muscle weakness. In addition, because it is as reproducible as MIP, it can be suitable to follow inspiratory muscle function in chronic neuromuscular patients. Because, of the important limit of agreement between SNIP and MIP, these two methods are not interchangeable but complementary.

Childhood predictors of smoking in adolescence: a follow-up study of Montreal schoolchildren

BACKGROUND

The factors that cause children to become smokers in adolescence remain unclear. Although parental smoking and peer pressure may play a role, physiological factors such as lung volume have also been identified.

METHODS

To investigate these and other possible childhood predictors of teenage smoking, we gathered follow-up data on 191 Montréal schoolchildren, aged 5-12 years (average 9.2 yr) when first examined. At an average age of 13.0 years, they answered further questions on their health and smoking behaviour and provided a second set of spirometric measurements.

RESULTS

At the second survey, 80% of the children had entered high school and 44% had become smokers. Reaching puberty between the surveys was the most significant determinant of becoming a smoker: 56.4% of the 124 children postpubertal at the second survey had taken up smoking, versus 17.9% of the 67 who were still prepubertal (p = 0.001). We found salivary cotinine level, a measure of uptake of environmental tobacco smoke, to be an independent predictor of becoming a teenage smoker; even after adjustment for sex, socioeconomic status of parents, a crowding index, and the numbers at home of siblings, adult smokers and cigarettes smoked, it remained significant for both groups: postpubertal (odds ratio [OR] 1.2, 95% confidence interval [CI] 1.2-3.0) and prepubertal (OR 2.1, 95% CI 1.0- 4.5). The influence of forced vital capacity was marginally significant only in the postpubertal group (OR 5.0, 95% CI 0.88-28.3).

INTERPRETATION

The proportion of nicotine absorbed from that available in environmental tobacco smoke during childhood is associated with subsequent smoking in adolescence. The more efficient absorption of nicotine seen in some children may be related to physiological factors such as lung capacity.

Pressions respiratoires maximales chez l’enfant : les exigences méthodologiques

INTRODUCTION

Measurement of maximal respiratory pressures against an occlusion has been used for a long time to assess respiratory muscle strength in the follow up of children with respiratory disease. In the early stage of disease this is the main test for diagnosing respiratory muscle involvement and the degree of that involvement. STATE OF KNOWLEDGES: The interpretation of the results is difficult on account of variability of the measurements and of the reference values. The aim of this article is to present, in the form of a literature review, the normal values available and the different determining factors as well as the advantages and limitations of these measurements.

PERSPECTIVES

The use by all the centres undertaking maximal respiratory pressure measurements in children of methodological techniques similar to those presented in this revue could be the starting point for obtaining an identical range of reference values for all.

CONCLUSION

Age, sex and the level of physical aptitude seem to be the most important determinants of maximal respiratory pressures. However, other methodological factors such as co-operation, training of the child in the performance of the manoeuvres and the type of device and protocol used, will all influence the results. These factors must be taken into consideration in order to diminish, as much as possible, the variability of the maximal pressures obtained.

Maximal static respiratory pressures in children and adolescents

This study was designed to establish reference values of maximal static respiratory pressures in children and adolescents in our community, and compare them with previous studies. Participants were recruited from three schools (randomly chosen from those located in the metropolitan area of the city of Valencia) after appropriate consent. None of the participants had a previous history of pulmonary, cardiac, and/or skeletal abnormalities, and all of them had normal spirometry. Forced spirometry (Spirotrac III, Vitalograph) and maximal inspiratory (P(ImaxRV)) and expiratory (P(EmaxTLC)) pressure values (Sibelmed 163) were obtained by the same investigator, following national guidelines (SEPAR 1990).We studied 392 subjects (185 males, 207 females) whose ages ranged from 8-17 years. The reproducibility of measurements was investigated in a subgroup of 88 participants (randomly selected from the total sample, and stratified for age and gender) by means of the intraclass correlation coefficient (P(EmaxTLC), 0.98; P(ImaxRV), 0.95). P(EmaxTLC) and P(ImaxRV) values were significantly different between males and females (P < 0.0001) and were normally distributed. A stepwise, linear multiple regression model was built in each gender group (male/female) for the prediction of P(ImaxRV) and P(EmaxTLC) values. Independent variables (weight, height, and age) and their potential interactions were forced to enter the model in order to maximize the square of the multiple correlation coefficient of the resultant equation. This model turned out to be applicable (homoscedasticity, independence, and normality requirements) for P(ImaxRV) (in males and females) and for P(EmaxTLC) (in males but not in females). Variables included in the model were age and the product of weight and height. Their predictive power ranged between 0.21-0.51. In conclusion, P(ImaxRV) and P(EmaxTLC) values increase with age from 8 until 17 years. In all age groups, values were higher in males than in females. Weight, height, and age are included in the predictive equations for P(ImaxRV) (in males and females) and P(EmaxTLC) (in males). Their predictive value is similar to that reported by other authors and ranges between 0.21-0.51. This model is not suitable for the prediction of P(EmaxTLC) in females; the observed mean and range should be used instead.

Pulmonary complications of chronic neuromuscular diseases and their management

Chronic neuromuscular diseases may affect all major respiratory muscles groups including inspiratory, expiratory, and bulbar, and respiratory complications are the major cause of morbidity and mortality. Untreated, many of these diseases lead inexorably to hypercapnic respiratory failure, precipitated in some cases by chronic aspiration and secretion retention or pneumonia, related to impairment of cough and swallowing mechanisms. Many measures are helpful including inhibition of salivation, cough-assist techniques, devices to enhance communication, and physical therapy. In addition, ventilatory assistance is an important part of disease management for patients with advanced neuromuscular disease. Because of its comfort, convenience, and portability advantages, noninvasive positive pressure ventilation (NPPV) has become the modality of first choice for most patients. Patients to receive NPPV should be selected using consensus guidelines, and initiation should be gradual to maximize the chances for success. Attention should be paid to individual preferences for interfaces and early identification of cough impairment that necessitates the use of cough-assist devices. For patients considered unsuitable for noninvasive ventilation, invasive mechanical ventilation should be considered, but only after a frank but compassionate discussion between the patient, family, physician, and other caregivers.

Normal values for maximal static inspiratory and expiratory pressures in healthy children

Maximal static respiratory pressures are a simple measure of respiratory muscle strength. In order to construct a set of equations describing normal values, we measured maximal inspiratory (P(Imax)) and expiratory (P(Emax)) pressures in 296 children (144 boys and 152 girls), aged 7-14 years, in sitting and standing positions. The boys reached higher values in sitting and standing positions for P(Imax) (-8.29 +/- 2.69 and -8.19 +/- 2.73 kPa, respectively) and P(Emax) (8.02 +/- 2.32 and 7.94 +/- 2.32 kPa, respectively) than girls (-6.53 +/- 1.99 and -6.60 +/- 2.03 kPa for P(Imax) and 6.91 +/- 1.79 and 7.13 +/- 1.81 kPa for P(Emax) for sitting and standing positions, respectively); the differences between boys and girls were highly significant (P < 0.001 in all instances). There were no differences regarding body position during measurements in both genders. Multiple correlation analysis showed significant correlations of pressures to age in boys in all cases, but in girls only for P(Imax) in standing position. Therefore, equations describing reference values were constructed with respect to age as the independent variable. Maximal pressures also correlated with maximal inspiratory and expiratory flows. The measurements of P(Imax) and P(Emax) are useful in assessing respiratory muscle strength despite their relatively large variability. P(Imax) and P(Emax) also correlate with maximum peak expiratory and inspiratory flows. Children generate lower pressures and lower maximal flows than adolescents and adults.

Pulmonary function testing in neuromuscular disease

Pulmonary function testing is useful in the diagnosis and management of patients with neuromuscular disease. It is important, however, to keep in mind that certain tests commonly used to assess these patients, such as MIPs and MEPs, although useful, are fraught with potential error and rigorous attention should be paid to technical details when performing them. In addition, many studies have shown that pulmonary impairment does not always parallel generalized muscle impairment and thorough testing therefore should be done in any patient with neuromuscular disease to assess the level of respiratory compromise accurately. In addition, the clinician should be aware that the pattern of involvement-bulbar versus inspiratory, versus expiratory muscle weakness-may vary markedly among patients, even with the same diagnosis, so testing should be tailored to detect these patterns. Furthermore, serial follow-up examinations should be performed to track the rate of deterioration so that therapeutic interventions can be initiated before respiratory crises occur.