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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.

Patients with obstructive sleep apnea (OSA) may experience apneas and hypopneas primarily during stage R (REM) sleep when end-expiratory lung volume (EELV) reaches its nadir. The purpose of this study was to determine if REM-related reductions in EELV persist in the presence of continuous positive airway pressure (CPAP) prescribed during non-stage REM (NREM) sleep. We prospectively recruited 17 subjects referred to the sleep laboratory for CPAP titration. CPAP was titrated per AASM protocol to control respiratory events. The change in EELV was measured using magnetometry. Of the 17 subjects, 12 (71%) had moderate to severe OSA. Despite the application of CPAP, there was a significant reduction in EELV between NREM and REM sleep (− 105.9 ± 92.2 to − 325.0 ± 113.1 mL, respectively, p

Pathologic processes that involve the central nervous system, phrenic nerve, neuromuscular junction, and skeletal muscle can impair diaphragm function. When these processes are of sufficient severity to cause diaphragm dysfunction, respiratory failure may be a consequence. This article reviews basic diaphragm anatomy and physiology and then discusses diagnostic and therapeutic approaches to disorders that result in unilateral or bilateral diaphragm dysfunction. This discussion provides a context in which disorders of the diaphragm and their implications on respiratory function can be better appreciated.

The change in vital capacity from the seated to supine position (∆VC-supine) is used to screen for diaphragm dysfunction (DD), but some individuals are unable to tolerate the supine position. Since expiratory muscle function is often preserved in patients with isolated DD and inspiratory strength is reduced, the purpose of this study was to examine if the ratio of maximal expiratory pressure to maximal inspiratory pressure (MEP/MIP) may provide an alternative to ∆VC-supine when screening patients for DD. We performed a cross-sectional analysis on 76 patients referred for evaluation of unexplained dyspnea and possible DD. MEP and MIP were measured in the seated position as well as the percent change in VC from the seated to supine position (∆VC-supine %). The presence of unilateral diaphragm paralysis (UDP), bilateral diaphragm paralysis (BDP), or normal diaphragm function (N) was confirmed by ultrasound. Of the 76 patients, 23 had N, 40 had UDP, and 13 had BDP. MEP/MIP was significantly greater for UDP compared to N (2.1(1.2–5.7) and 1.5(0.7–2.2), respectively) (median and interquartile range) and for BDP compared to UDP (4.3(2.3–7.5) and 2.1(1.2–5.7), respectively) (p

ObjectiveThe prevalence of obstructive sleep apnea (OSA) in women increases significantly after menopause. However, identifying at-risk women is difficult because they tend to underreport symptoms and their complaints may differ from those traditionally associated with OSA. We investigated whether OSA risk factors are associated with the presence of a "nontraditional" complaint, such as nocturnal enuresis, in postmenopausal women.MethodsA cross-sectional study of postmenopausal women aged 50 to 79 years who participated in the Women's Health Initiative Observational Study and clinical trials (1993-2005) at 40 clinical centers in the United States was performed. Multiple variable logistic regression analysis was used to determine the association of OSA risk factors with nocturnal enuresis.ResultsA cohort of 2,789 women (1.7%) reported having nocturnal enuresis. Obesity (odds ratio [OR], 2.29; 95% CI, 2.00-2.62), snoring (OR, 2.01; 95% CI, 1.74-2.32), poor sleep quality (OR, 1.70; 95% CI, 1.52-1.91), sleep fragmentation (OR, 2.44; 95% CI, 2.14-2.79), daytime sleepiness (OR, 1.50; 95% CI, 1.33-1.68), and hypertension (OR, 1.13; 95% CI, 1.01-1.26) were associated with nocturnal enuresis. Each additional OSA risk factor in a predefined OSA score significantly increased the odds of having nocturnal enuresis in a dose-response fashion (OR of 1.38, 2.00, 2.80, 3.87, 5.10, and 7.02 for scores of 1-6, respectively) compared with no risk factors.ConclusionsOSA risk factors are associated with nocturnal enuresis in postmenopausal women. Mechanisms relating nocturnal enuresis to OSA may include apnea-associated changes in intrathoracic pressure, leading to increased urine output. Questioning at-risk postmenopausal women presenting with nocturnal enuresis about other OSA risk factors should be considered.

Changes in end-expiratory lung volume (∆EELV) in response to changes in PEEP (∆PEEP) have not been reported in mechanically ventilated patients with ARDS. The purpose of this study was to determine the utility of measurements of ∆EELV in determining optimal PEEP in ARDS patients. Nine patients with ARDS were prospectively recruited. ∆EELV was measured using magnetometers during serial decremental PEEP trials. Changes in PaO2 (∆PaO2) were simultaneously measured. Static respiratory system compliance (CRS), ∆PaO2/∆PEEP, and ∆EELV/∆PEEP were calculated at each level of PEEP. For the group, ∆EELV decreased by 1.09 ± 0.13 L (mean ± SD) as PEEP was reduced from 20 to 0 cm H2O with the greatest changes in ∆EELV occurring over the mid range of the decremental PEEP curve. Optimal values for CRS, ∆EELV/∆PEEP, and ∆PaO2/∆PEEP could be identified for each patient and occurred at PEEP levels ranging from 10 to 17.5 cm H2O. There was a significant correlation (r = 0.712, p = 0.047) between ∆PaO2/∆PEEP and ∆EELV/∆PEEP. ∆EELV can be measured from a decremental PEEP curve. Since ∆EELV is highly correlated with ∆PaO2, measures of ∆PaO2/∆PEEP may provide a surrogate for measures of ∆EELV/∆PEEP. Combining measures of ∆EELV/∆PEEP with measures of CRS may provide a novel means of determining optimal PEEP in patients with ARDS.

Diaphragm dysfunction is defined as the partial or complete loss of diaphragm muscle contractility. However, because the diaphragm is one of only a few skeletal muscles that is not amenable to direct examination, the tools available for the clinician to assess diaphragm function have been limited. Traditionally, measures of lung volume, inspiratory muscle strength, and radiographic techniques such as fluoroscopy have provided the major method to assess diaphragm function. Measurement of transdiaphragmatic pressure provides the most direct means of evaluating the diaphragm, but this technique is not readily available to clinicians. Diaprhragm ultrasonography is new method that allows for direct examination of the diaphragm.

An incisional hernia is a common complication after abdominal surgery. Complaints of dyspnea in this population may be attributed to cardiopulmonary dysfunction or deconditioning. Large abdominal incisional hernias, however, may cause diaphragm dysfunction and result in dyspnea, which is more pronounced when standing (platypnea). The use of an abdominal binder may alleviate platypnea in this population. We discuss the link between diaphragm dysfunction and the lack of abdominal wall integrity and how abdominal wall support partially restores diaphragm function.

Background Given high rates of obesity, hypertension, and diabetes mellitus, black persons are at risk to develop heart failure. The association of moderate to vigorous physical activity ( MVPA ) and heart failure in black adults is underresearched. The purpose of this study was to explore whether greater MVPA was associated with lower risk of heart failure hospitalizations (HFHs) among black adults with normal ejection fractions. Methods and Results We performed a prospective analysis of 4066 black adults who participated in the Jackson Heart Study and who had physical activity measured, had normal ejection fraction on 2‐dimensional echocardiograms, and were followed for 7 years for incident HFH. We used Cox proportional regression analyses adjusted for age, sex, body mass index, smoking status, hypertension, diabetes mellitus, chronic obstructive pulmonary disease, coronary heart disease, atrial fibrillation, and chronic kidney disease and examined effect modification by sex and body mass index. Of the eligible population, 1925 participants, according to the duration of MVPA , had poor health (0 minutes/week), 1332 had intermediate health (1–149 minutes/week), and 809 had ideal health (≥150 minutes/week). There were 168 incident HFHs . MVPA for intermediate and ideal health was associated with decreasing risk of incident HFH (hazard ratio: 0.70 [95% confidence interval, 49–1.00] and 0.35 [95% confidence interval, 0.19–0.64], respectively; P trend =0.003). The full model revealed hazard ratios of 0.74 [95% confidence interval, 0.52–1.07] and 0.41 [95% confidence interval, 0.22–0.74], respectively. There was no effect modification between MVPA and body mass index or sex on incident HFH . Conclusions A dose‐response relationship between increasing levels of MVPA and protection from incident HFH was found in black men and women with normal ejection fractions.

"Optimal" mean airway pressure (MAP) during high-frequency oscillatory ventilation (HFOV) can be defined as the pressure that allows for maximal alveolar recruitment while minimizing alveolar overdistension. Choosing a MAP near or just below the point of maximal curvature (PMC) of the volume-pressure characteristics of the lung can serve as a guide to avoid overdistention during HFOV, while simultaneously preventing derecruitment. The purpose of this study was to assess whether optimal MAP at the PMC can be determined by using measures of PaO(2) in patients with acute respiratory distress syndrome (ARDS) undergoing HFOV.We prospectively studied seven patients with ARDS who underwent HFOV after failed conventional ventilation. In addition, 11 healthy subjects were studied to validate measurements of changes in end-expiratory lung volume (∆EELV) using magnetometers. Using this validated method, plots of ∆EELV and MAP were constructed during decremental changes in MAP following a recruitment maneuver in seven ventilated patients with ARDS. The PMC was defined as the point where the slope of the ∆EELV versus MAP curve acutely changed. The MAP at the PMC was compared to that determined from plots of PaO(2) versus MAP.In the healthy cohort, measurements of ∆EELV obtained by magnetometry approximated the line of identity when compared to those obtained by spirometry. The MAP determined using either the ∆EELV or PaO(2) techniques were identical in all seven HFOV ventilated patients. Additionally, there was a significant correlation between the MAP associated changes in PaO2 and the MAP associated changes in ∆EELV (p 0.001).The finding that MAP at the PMC is the same whether determined by measures of ∆EELV or PaO(2) suggest that bedside measures PaO(2) may provide an acceptable surrogate for measures of EELV when determining "optimal" MAP during HFOV.

As lung volume decreases radial traction on the upper airway is reduced, making it more collapsible. The purpose of this study was to measure change in end-expiratory lung volume (EELV) following sleep onset and to evaluate the relationship between change in EELV and sleep-disordered breathing.Twenty subjects underwent overnight polysomnography, of whom 14 (70%) had obstructive sleep apnea (OSA). Change in EELV was measured throughout the night using magnetometry. Sleep was staged and respiratory events scored using American Academy of Sleep Medicine criteria. An additional 10 subjects had change in EELV measured simultaneously by magnetometer and spirometer while awake.In the subjects studied while awake, change in EELV calculated from magnetometer data correlated very strongly (Magnetometry provides a precise, unobtrusive, and continuous means to study lung volume changes during sleep. EELV declines from sleep onset, reaching its nadir during stage R sleep. The reduction in EELV in stage R sleep was associated with lower mean oxygen saturation but was not associated with greater sleep-disordered breathing.

Ultrasonographic assessment of diaphragm function with patients on low levels of pressure support (PS) predicts extubation outcomes, but similar information regarding extubation success under other conditions is lacking. The purpose of this study was to determine whether ultrasound (US) measurements of the diaphragm made on various levels of PS can predict time until successful extubation. Fifty-six intubated patients underwent ultrasound of the right hemidiaphragm during a PS wean at varying levels of pressure support (PS 5/5 cm of H2O, 10/5 cm of H2O, and 15/5 cm of H2O). The diaphragm was visualized using a 7.5–10 mHz transducer in the zone of apposition of the diaphragm to the lower rib cage. The percent change in diaphragm thickness between end-expiration and end-inspiration (∆tdi%) was calculated at each level of PS. ∆tdi% >20 is a robust predictor of extubation success within 48 h of US at PS 5/5 cm of H2O and 10/5 cm of H2O (sensitivity 84.6 and 88.9 % and specificity 79.0 and 75.0 %, respectively). At PS greater than 10/5 cm of H2O, its predictive power was greatly diminished. Of nine patients who were extubated with ∆tdi% below the cutoff, 66.6 % required emergent reintubation in the next two days. Diaphragm US is a valid predictor of extubation success at some but not all PS settings. Using a ∆tdi% of 20 % on PS levels up to 10/5 cm of H2O may reduce both unnecessarily prolonged intubations and prevent emergent reintubations.

Introduction: Diastolic dysfunction (DD) with normal ejection fraction is prevalent in the African-American population due to a higher prevalence of associated risk factors. The potential benefit of moderate to vigorous physical activity (MVPA) to prevent heart failure admissions in African-American adults with normal ejection fraction is under-researched. The purpose of this study is to investigate the associations of DD and MVPA with heart failure hospitalizations (HFH). Hypothesis: We hypothesized that MVPA reduces the risk of HFH among African-American adults with normal ejection fraction. Methods: We performed a prospective analysis of 2,427 African-American adults who participated in the Jackson Heart Study and who had 2D echo and physical activity data and normal ejection fraction. MVPA per week is defined as the following: poor health [[Unable to Display Character: –]] 0 minutes; intermediate health [[Unable to Display Character: –]] 1-149 minutes; and ideal health [[Unable to Display Character: –]] ≥ 150 minutes. DD is defined as using ratio of the early to late ventricular filling velocities, ratio of pulmonary venous systolic to diastolic velocities, and pulmonary venous atrial reversal velocity. We employed multiple variable logistic and cox proportional regression analyses adjusted for age, gender, BMI, smoking, hypertension, DM, COPD, CKD, and CHD to determine the associations of DD and MVPA with HFH. Results: Of the eligible population, 1,209 (50%) have DD. There were 171 HFH. DD is associated with HFH in the crude analysis (OR=2.24, 95% CI 1.40-3.57). The association was markedly attenuated after adjusting for age (OR=1.03, CI 0.63-1.71). Intermediate and ideal health MVPA in the crude analysis were associated with lower risk of HFH (HR=0.50, 95% CI 0.35-0.71 and HR=0.18, 95% CI 0.09-0.36, respectively), and full models revealed HR=0.71, 95% CI 0.49-1.04 and HR=0.31, 95% CI 0.16-0.63, respectively. There was no interaction between physical activity level and DD on HFH. Conclusion: In conclusion, ideal health MVPA is associated with reduced risk of HFH, whereas, intermediate health MVPA revealed a trend in risk reduction in African-American with normal ejection fraction.

Dysfunction of one or both hemidiaphragms is an underdiagnosed cause of dyspnea. Weakness or paralysis may be seen during mechanical ventilation, after surgery or trauma, with metabolic or inflammatory disorders, and with myopathy, neuropathy, or diseases causing lung hyperinflation.

Study Objectives Idiopathic diaphragm paralysis is probably more common and responsible for more morbidity than generally appreciated. Bell’s palsy, or idiopathic paralysis of the seventh cranial nerve, may be seen as an analogous condition. The roles of zoster sine herpete and herpes simplex have increasingly been recognized in Bell’s palsy, and there are some data to suggest that antiviral therapy is a useful adjunct to steroid therapy. Thus, we postulated that antiviral therapy might have a positive impact on the course of acute idiopathic diaphragm paralysis which is likely related to viral infection. Methods Three consecutive patients with subacute onset of symptomatic idiopathic hemidiaphragm paralysis were empirically treated with valacyclovir, 1,000 mg twice daily for 1 week. Prior to therapy, diaphragmatic function was assessed via pulmonary function testing and two-dimensional B-mode ultrasound, with testing repeated 1 month later. Diaphragmatic function pre- and post-treatment was compared to that of a historical control group of 16 untreated patients. Results All three subjects demonstrated ultrasound recovery of diaphragm function 4–6 weeks following treatment with valacyclovir. This recovery was accompanied by improvements in maximum inspiratory pressure (PImax) and vital capacity (VC). In contrast, in the untreated cohort, diaphragm recovery occurred in only 11 subjects, taking an average of 14.9 ± 6.1 months (mean ± SD). Conclusions The results of this small, preliminary study suggest that antiviral therapy with valacyclovir may be helpful in the treatment of idiopathic diaphragm paralysis induced by a viral infection.

Advancing age is associated with a decline in the strength of the skeletal muscles, including those of respiration. Respiratory muscles can be strengthened with nonrespiratory activities. We therefore hypothesized that regular exercise in the elderly would attenuate this age-related decline in respiratory muscle strength. Twenty-four healthy subjects older than 65 years were recruited (11 males and 13 females). A comprehensive physical activity survey was administered, and subjects were categorized as active (n = 12) or inactive (n = 12). Each subject underwent testing of maximum inspiratory and expiratory pressures (PI(max) and PE(max)). Diaphragmatic thickness (tdi) was measured via two-dimensional B-mode ultrasound. There were no significant differences between the active and inactive groups with respect to age (75 vs. 73 years) or body weight (69.1vs. 69.9 kg). There were more women (9) than men (3) in the inactive group. Diaphragm thickness was greater in the active group (0.31 +/- 0.06 cm vs. 0.25 +/- 0.04 cm; p = 0.011). PE(max) and PI(max) were also greater in the active group (130 +/- 44 cm H(2)O vs. 80 +/- 24 cm H(2)O; p = 0.002; and 99 +/- 32 cm H(2)O vs. 75 +/- 14 cm H(2)O; p = 0.03). There was a positive association between PI(max )and tdi (r = 0.43, p = 0.03). Regular exercise was positively associated with diaphragm muscle thickness in this cohort. As PE(max) was higher in the active group, we postulate that recruitment of the diaphragm and abdominal muscles during nonrespiratory activities may be the source of this training effect.

Diaphragm dysfunction is an increasingly recognized consequence of critical illness and mechanical ventilation. Ultrasound of the diaphragm is a convenient, noninvasive modality for assessing diaphragm function at the bedside in the intensive care unit and can be used to determine the presence of diaphragm paralysis, dysfunction, and atrophy. Ultrasound can be used to visualize either the dome of the diaphragm or the diaphragm muscle where it abuts the rib cage (zone of apposition of the diaphragm to the rib cage (ZAP)). Either the M- or B-mode can be used to image the diaphragm dome or diaphragm muscle in the ZAP. The motion of the dome during the breathing cycle is best appreciated using the M-mode, whereas the thickening of the diaphragm muscle during inspiration is best appreciated using the B-mode in the ZAP. The advantages of visualizing the diaphragm in the ZAP include measuring the degree to which it contracts during inspiration and its thickness prior to inspiration. These measures have been used to determine whether a diaphragm is paralyzed, if atrophy is present, and suitability of a patient to wean from mechanical ventilation. This chapter will review technical features of imaging the diaphragm dome and the diaphragm in the ZAP and discuss functional correlates of these measures. The capability of ultrasound to specifically evaluate diaphragm function provides the clinician with valuable and immediate information on a traditionally inaccessible organ system which may be used on daily rounds.

Objective: The anatomy and neurophysiology of cough has been reviewed in the preceding section. The objective of this section is to describe how the varied anatomic components of the respiratory system work in concert to produce an effective cough. Methods: This was accomplished by reviewing (1) the factors needed to produce effective cough pressures and gas velocity in the airways, and (2) the salient features of the interaction between the airflow generated during a cough and the mucus that lines the tracheobronchial tree. The MEDLINE database was searched for this review, and the search consisted of studies published in English between 1960 and April 2004. Search terms were "cough mechanics" and "cough physiology." Results: Inhaling to high lung volumes and glottic closure prior to the expiratory phase of cough facilitate the generation of high intrathoracic pressures. These high intrathoracic pressures (1) provide the driving force for airstream flow during cough and (2) dynamically compress the central airways, which further enhances the cough airstream velocity. Conclusions: High intrathoracic pressures are needed to generate the requisite cough expiratory flows and airstream velocities. However, cough may be effective in individuals with mild-to-moderate degrees of respiratory muscle weakness, as only modest increases in intrathoracic pressure are needed to dynamically compress the large intrathoracic airways and increase cough flow velocity.

Background: Airway clearance may be impaired in disorders associated with abnormal cough mechanics, altered mucus rheology, altered mucociliary clearance, or structural airway defects. A variety of interventions are used to enhance airway clearance with the goal of improving lung mechanics and gas exchange, and preventing atelectasis and infection. Method: A formal systematic review of nonpharmacologic protussive therapies was performed and constitutes the basis for this section of the guideline. In addition, the articles reviewed were found using the same methodology but were not limited to those that focused only on cough as a symptom. The MEDLINE database was searched for this review and consisted of studies published in the English language between 1960 and April 2004. The search terms used were “chest physiotherapy,” “forced expiratory technique,” “positive expiratory pressure,” “high frequency chest compression,” “insufflation,” and “exsufflation.” Results: In general, studies of nonpharmacologic methods of improving cough clearance are limited by methodological constraints, and most were conducted only in patients with cystic fibrosis. Chest physiotherapy, including postural drainage, chest wall percussion and vibration, and a forced expiration technique (called huffing), increase airway clearance as assessed by sputum characteristics (ie, volume, weight, and viscosity) and clearance of the radioaerosol from the lung, but the long-term efficacy of these techniques compared with unassisted cough alone is unknown. Other devices that allow patients to achieve the same benefits derived from chest physiotherapy without the assistance of a caregiver appear to be as effective as chest physiotherapy in increasing sputum production. Conclusions: Some nonpharmacologic therapies are effective in increasing sputum production, but their long-term efficacy in improving outcomes compared with unassisted cough alone is unknown. (CHEST 2006; 129:250S–259S)

Recognition of the importance of cough in clinical medicine was the impetus for the original evidence-based consensus panel report on “Managing Cough as a Defense Mechanism and as a Symptom,” published in 1998,1 and this updated revision. Compared to the original cough consensus statement, this revision (1) more narrowly focuses the guidelines on the diagnosis and treatment of cough, the symptom, in adult and pediatric populations, and minimizes the discussion of cough as a defense mechanism; (2) improves on the rigor of the evidence-based review and describes the methodology in a separate section; (3) updates and expands, when appropriate, all previous sections; and (4) adds new sections with topics that were not previously covered. These new sections include nonasthmatic eosinophilic bronchitis (NAEB); acute bronchitis; nonbronchiectatic suppurative airway diseases; cough due to aspiration secondary to oral/pharyngeal dysphagia; environmental/occupational causes of cough; tuberculosis (TB) and other infections; cough in the dialysis patient; uncommon causes of cough; unexplained cough, previously referred to as idiopathic cough; an empiric integrative approach to the management of cough; assessing cough severity and efficacy of therapy in clinical research; potential future therapies; and future directions for research. To mitigate future diagnostic confusion, two new diagnostic terms have been introduced to replace two older terms that may represent misnomers. The committee unanimously recommends that the term upper airway cough syndrome (UACS) be used in preference to postnasal drip syndrome (PNDS) when discussing cough that is associated with upper airway conditions because it is unclear whether the mechanism of cough is postnasal drip, direct irritation, or inflammation of the cough receptors in the upper airway. The committee also recommends using the term unexplained cough rather than idiopathic cough because it is likely that more than one unknown cause of chronic cough will be discovered. The term idiopathic implies that one is dealing with only one disease. For managing adult patients with cough, the committee recommends an empiric, integrative diagnostic approach, which is presented in the section entitled “An Empiric Integrative Approach to the Management of Cough”.3 Guidelines for managing acute, subacute, and chronic cough are presented in algorithmic form (Fig 1–3). Guidelines with algorithms for evaluating chronic cough in pediatric patients < 15 years of age are presented in the section entitled “Guidelines for Evaluating Chronic Cough in Pediatrics”2,4 [Fig 4, ​,5].5]. For a full discussion on how to use the algorithms, please refer to these sections. Figure 1 Acute cough algorithm for the management of patients ≥ 15 years of age with cough lasting < 3 weeks. For diagnosis and treatment recommendations refer to the section indicated in the algorithm. PE = pulmonary embolism; Dx = diagnosis; ... Figure 3 Chronic cough algorithm for the management of patients ≥ 15 years of age with cough lasting > 8 weeks. ACE-I = ACE inhibitor; BD = bronchodilator; LTRA = leukotriene receptor antagonist; PPI = proton pump inhibitor. See the legend of ... Figure 4 Approach to a child 6 years of age and in some children ... Figure 5 Approach to a child ≤ 14 years of age with chronic specific cough (ie, cough associated with other features suggestive of an underlying pulmonary and/or systemic abnormality). Children > 14 years of age should be managed as outlined in ...

Peak expiratory flow (PEF) has previously been considered an effort-dependent, non flow-limited parameter that is constrained by the force-velocity relationship of the respiratory muscles. It has also been assumed that, if the muscles were able to augment the expiratory pressure, the PEF would increase. We tested the validity of this notion in normal volunteers who were able to enhance their expiratory pressure with maneuvers utilizing the stretch-shortening cycle (greater force when contractions were immediately preceded by eccentric contractions). Five healthy volunteers [35 (2) years] performed two successive maximal expiratory flow-volume maneuvers (MEFV) in rapid sequence. MEFV1 was a standard maneuver, whereas MEFV2 included a forceful inspiration to total lung capacity; a strategy designed to augment expiratory pressure via the stretch-shortening cycle. Neither maneuver included a post-inspiratory pause. We measured PEF, esophageal pressure (P(es)), and the electromyographic activity of the abdominal muscles. Compared to MEFV1, MEFV2 produced greater activation of the abdominal muscles during inspiration (eccentric contraction), greater peak expiratory P(es), greater rate of rise of P(es), shorter time to PEF, but similar PEF. Our findings directly demonstrate the inability of the augmented expiratory effort to increase PEF and thus support the notion that PEF is determined by a flow-limiting mechanism and not by the velocity of muscle shortening.

The diaphragm and abdominal muscles can be recruited during nonrespiratory maneuvers. With these maneuvers, transdiaphragmatic pressures are elevated to levels that could potentially provide a strength-training stimulus. To determine whether repeated forceful nonrespiratory maneuvers strengthen the diaphragm, four healthy subjects performed sit-ups and biceps curls 3-4 days/wk for 16 wk and four subjects served as controls. The maximal transdiaphragmatic pressure was measured at baseline and after 16 wk of training. Maximum static inspiratory and expiratory mouth pressures and diaphragm thickness derived from ultrasound were measured at baseline and 8 and 16 wk. After training, there were significant increases in diaphragm thickness [2.5 ± 0.1 to 3.2 ± 0.1 mm (mean ± SD) ( P < 0.001)], maximal transdiaphragmatic pressure [198 ± 21 to 256 ± 23 cmH2O ( P < 0.02)], maximum static inspiratory pressure [134 ± 22 to 171 ± 16 cmH2O ( P < 0.002)], maximum static expiratory pressure [195 ± 20 to 267 ± 40 cmH2O ( P < 0.002)], and maximum gastric pressure [161 ± 5 to 212 ± 40 cmH2O ( P < 0.03)]. These parameters were unchanged in the control group. We conclude that nonrespiratory maneuvers can strengthen the inspiratory and expiratory muscles in healthy individuals. Because diaphragm thickness increased with training, the increase in maximal pressures is unlikely due to a learning effect.

Study objectives: To determine the accuracy of a portable magnetometer designed to measure tidal volume (VT), inspiratory time (TI), and expiratory time (TE). Participants: Fourteen healthy subjects. Design: Subjects breathed over a sixfold range of VTs while at rest (sitting and standing) and during treadmill exercise. We then compared VT ,T I, and TE measured by magnetometry (VTmag, TImag, and TEmag) with VT ,T I, and TE measured by spirometry (VTspiro, TIspiro, and TEspiro, respectively). Setting: Pulmonary function and exercise physiology laboratories. Measurements and results: The sternal-umbilical distance and the anteroposterior displacements of the rib cage and abdomen were measured with two pairs of magnetometer coils. VT was calculated from the sum of these three signals, and was simultaneously measured using a spirometer or flow meter. A total of 1,111 breaths were analyzed for the resting condition, and 1,163 breaths were analyzed for the exercise condition. We found that VTmag was highly correlated with VTspiro at rest (R 2 0.90) and during exercise (R 2 0.79) for pooled data. The slope of this relationship approached the line of identity. The mean percentage differences between VTmag and VTspiro were 10.1 6.6% at rest and 13.5 8.6% with exercise. By Bland-Altman analysis, the mean differences between VTmag and VTspiro were 38 mL at rest with changes in posture, and 182 mL during exercise. TImag and TIspiro values and TEmag and TEspiro values also were highly correlated (R 2 0.97 and R 2 0.95, respectively) for pooled data. Conclusion: A portable magnetometer system can give useful measures of VT ,T I, and TE over a wide range of VTs in sitting, standing, and exercising subjects. (CHEST 2002; 122:684 – 691)

This review presents clinically relevant issues regarding the assessment of respiratory muscles in individuals with neuromuscular disorders, and discusses the advantages and disadvantages of methods generally available to the clinician. Vital capacity (VC) and total lung capacity (TLC) are routinely measured in pulmonary function laboratories and are typically reduced in the context of severe respiratory muscle weakness, but the sensitivity and specificity of these measures are limited. Better measures of respiratory muscle weakness are maximal static inspiratory and expiratory pressures (PI max and PE max). PI max is reduced even with mild or moderate degrees of inspiratory muscle weakness, but low values also may be related to submaximal effort. To circumvent this problem, pressures can be measured using simpler maneuvers such as a maximal sniff. Specific tests of diaphragm function such as measurements of maximal transdiaphragmatic pressure are invasive and not routinely available to the clinician. Recently, noninvasive methods that specifically assess diaphragm function, such as diaphragm ultrasound of the zone of apposition and magnetic or electrophrenic nerve stimulation, have shown promise as new techniques for clinical use.

Respiratory dysfunction frequently occurs in patients with advanced multiple sclerosis (MS), and may manifest as acute or chronic respiratory failure, disordered control of breathing, respiratory muscle weakness, sleep disordered breathing, or neurogenic pulmonary edema. The underlying pathophysiology is related to demyelinating plaques involving the brain stem or spinal cord. Respiratory complications such as aspiration, lung infections and respiratory failure are typically seen in patients with long-standing MS. Acute respiratory failure is uncommon and due to newly appearing demyelinating plaques extensively involving areas of the brain stem or spinal cord. Early recognition of MS patients at risk for respiratory complications allows for the timely implementation of care and measures to decrease disease associated morbidity and mortality.

Introduction The purpose of this study was to evaluate if ultrasound derived measures of diaphragm thickening, rather than diaphragm motion, can be used to predict extubation success or failure. Methods Sixty-three mechanically ventilated patients were prospectively recruited. Diaphragm thickness (tdi) was measured in the zone of apposition of the diaphragm to the rib cage using a 7–10 MHz ultrasound transducer. The percent change in tdi between end-expiration and end-inspiration (Δtdi%) was calculated during either spontaneous breathing (SB) or pressure support (PS) weaning trials. A successful extubation was defined as SB for >48 h following endotracheal tube removal. Results Of the 63 subjects studied, 27 patients were weaned with SB and 36 were weaned with PS. The combined sensitivity and specificity of Δtdi%≥30% for extubation success was 88% and 71%, respectively. The positive predictive value and negative predictive value were 91% and 63%, respectively. The area under the receiver operating characteristic curve was 0.79 for Δtdi%. Conclusions Ultrasound measures of diaphragm thickening in the zone of apposition may be useful to predict extubation success or failure during SB or PS trials.

Cohn, David, Joshua O. Benditt, Scott Eveloff, and F. Dennis McCool. Diaphragm thickening during inspiration. J. Appl. Physiol. 83(1): 291–296, 1997.—Ultrasound has been used to measure diaphragm thickness ( T di) in the area where the diaphragm abuts the rib cage (zone of apposition). However, the degree of diaphragm thickening during inspiration reported as obtained by one-dimensional M-mode ultrasound was greater than that predicted by using other radiographic techniques. Because two-dimensional (2-D) ultrasound provides greater anatomic definition of the diaphragm and neighboring structures, we used this technique to reevaluate the relationship between lung volume and T di. We first established the accuracy and reproducibility of 2-D ultrasound by measuring T diwith a 7.5-MHz transducer in 26 cadavers. We found that T di measured by ultrasound correlated significantly with that measured by ruler ( R 2 = 0.89), with the slope of this relationship approximating a line of identity ( y = 0.89 x + 0.04 mm). The relationship between lung volume and T di was then studied in nine subjects by obtaining diaphragm images at the five target lung volumes [25% increments from residual volume (RV) to total lung capacity (TLC)]. Plots of T di vs. lung volume demonstrated that the diaphragm thickened as lung volume increased, with a more rapid rate of thickening at the higher lung volumes [ T di = 1.74 vital capacity (VC)2 + 0.26 VC + 2.7 mm] ( R 2= 0.99; P < 0.001) where lung volume is expressed as a fraction of VC. The mean increase in T di between RV and TLC for the group was 54% (range 42–78%). We conclude that 2-D ultrasound can accurately measure T di and that the average thickening of the diaphragm when a subject is inhaling from RV to TLC using this technique is in the range of what would be predicted from a 35% shortening of the diaphragm.

Background Chronic obstructive pulmonary disease (COPD) is a progressive, debilitating disease associated with significant clinical burden and is estimated to affect 15 million individuals in the US. Although a large number of individuals are diagnosed with COPD, many individuals still remain undiagnosed due to the slow progression of the disorder and lack of recognition of early symptoms. Not only is there under-diagnosis but there is also evidence of sub-optimal evidence-based treatment of those who have COPD. Despite the development of international COPD guidelines, many primary care physicians who care for the majority of patients with COPD are not translating this evidence into effective clinical practice. Method/Design This paper describes the design and rationale for a randomized, cluster design trial (RCT) aimed at translating the COPD evidence-based guidelines into clinical care in primary care practices. During Phase 1, a needs assessment evaluated barriers and facilitators to implementation of COPD guidelines into clinical practice through focus groups of primary care patients and providers. Using formative evaluation and feedback from focus groups, three tools were developed. These include a computerized patient activation tool (an interactive iPad with wireless data transfer to the spirometer); a web-based COPD guideline tool to be used by primary care providers as a decision support tool; and a COPD patient education toolkit to be used by the practice team. During phase II, an RCT will be performed with one year of intervention within 30 primary care practices. The effectiveness of the materials developed in Phase I are being tested in Phase II regarding physician performance of COPD guideline implementation and the improvement in the clinically relevant outcomes (appropriate diagnosis and management of COPD) compared to usual care. We will also examine the use of a patient activation tool - ‘MyLungAge’ - to prompt patients at risk for or who have COPD to request spirometry confirmation and to request support for smoking cessation if a smoker. Discussion Using a multi-modal intervention of patient activation and a technology-supported health care provider team, we are testing the effectiveness of this intervention in activating patients and improving physician performance around COPD guideline implementation. Trial registration ClinicalTrials.gov, NCT01237561

The incorporation of airways conductance/resistance is a rare feature in clinical methacholine challenge test (MCT) protocols, and the majority of pulmonary laboratories rely solely on the spirometric parameters. The importance and interpretation of an MCT demonstrating a significant decline in specific airway conductance specific airway conductance (sGaw), but not forced expiratory volume in one second (FEV(1)), remains undefined. This study sought to elucidate the clinical and physiologic phenotypes of individuals with a ≥40% sGaw decline but20% FEV(1) change.All subjects completed the Asthma Quality of Life Questionnaire (AQLQ), followed by standard MCT, with measurements of sGaw and an additional independent measurement of resistance and reactance by impulse oscillation system (IOS) before and after MCT.Of 201 subjects, 47(23.4%) were in Group 1 (FEV(1) declined by ≥20%), 45(22.4%) were in Group 2 (non-significant FEV(1) drop, sGaw declined ≥40%), and 109(54.2%) were in Group 3 (no significant decline in FEV(1)/sGaw). There was a nearly identical change in all oscillometric parameters and sGaw for Groups 1 and 2 versus Group 3. There were no differences between Groups 1 and 2 in any AQLQ category, and Groups 1 and 2 were statistically different from Group 3.Our prospective study suggests that patients with a significant sGaw decline alone during MCT are a clinically and physiologically important hyper-reactivity phenotype--whose hyper-reactivity independently was confirmed to be nearly identical to those with an FEV(1) decline. By failing to assess airways conductance/resistance, asthma may be inappropriately "ruled out" in ∼20% of the patients referred for MCT. Based on this, standardized incorporation of body plethysmography and/or IOS to MCT protocols should be considered.

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

Pulmonary hypertension (PH) is a comorbidity associated with increased mortality in chronic obstructive pulmonary disease (COPD) patients. It is not known which clinical markers are predictive of PH in COPD. The goal of this study was to develop a clinical tool to identify patients who should be sent for initial screening with echocardiography.Of 127 patients screened, 94 primary-care patients with COPD were enrolled. All underwent full pulmonary function testing, 6-minute walk distance (6MWD), exercise oximetry, Saint George's Respiratory Questionnaire, and transthoracic echocardiography. Eighty-six patients had measurable pulmonary artery pressures (PAP) on echocardiography. Elevated PAP was defined as a systolic PAP35 mmHg.Pre- and post-bronchodilator FEV(1) (P = 0.04 and P = 0.03, respectively), exercise oxyhemoglobin desaturation (P = 0.003), and 6MWD (P = 0.004) were associated with elevated PAP on univariate analysis. Diffusion capacity was lower but did not reach statistical significance (P = 0.07). In multivariate analysis, statistically significant independent variables were3% decrease in exercise oxyhemoglobin saturation and decline in prebronchodilator FEV(1) (P = 0.01 and P = 0.04, respectively). A composite prediction model was developed that assigned one point for each of the following: age55 years, oxyhemoglobin desaturation3%, prebronchodilator FEV(1)50% predicted, and 6MWD1175 ft. Prevalence rates of elevated PAP were 32% for a score of 0-1 (low risk), 68% for a score of 2 (moderate risk), and 78% for a score of 3-4 (high risk). The composite score exhibited a strong trend with elevated PAP prevalence (Cochrane-Armitage trend statistic P = 0.001).A simple prediction tool using routine office-based parameters can be used to identify COPD patients at high risk for elevated PAP and initiate the first step in screening for PH with echocardiography. It is important that right heart catheterization be performed to confirm the diagnosis and guide treatment decisions.

The etiology and prevalence of pulmonary hypertension (PH) in patients with stable chronic obstructive pulmonary disease (COPD) is uncertain. This study was done to determine the prevalence of PH in stable COPD outpatients and to evaluate the relationship between PH and indices of pulmonary function. The study was a retrospective review of outpatients with COPD and PH defined as a history of cigarette smoking, pulmonary function tests (PFTs) that met GOLD criteria for airway obstruction, an echocardiogram within 6 months of PFTs, and a left ventricular ejection fraction (LVEF) >55%. Of the 159 individuals who met all inclusion criteria, 105 had a sufficient tricuspid regurgitant jet to measure systolic pulmonary artery pressure (sPAP). PH was defined as sPAP ≥36 mmHg. The prevalence of PH was 60% (63/105) in the study group. The mean sPAP in patients with PH was 45 ± 6 mmHg. COPD patients with PH were older (71.1 ± 11.8 vs. 63.7 ± 10.2 years, P = 0.001), had lower FEV1% predicted (51.8 ± 18.8 vs. 62.7 ± 20.5%, P = 0.006), a higher RV/TLC (0.55 ± 0.10 vs. 0.48 ± 0.11, P = 0.001), and a lower % predicted DLCO (59.6 ± 19.5% vs. 71.9 ± 24.9%, P = 0.006). Only age (P