Respiratory abdominal muscle recruitment and chest wall motion in myotonic muscular dystrophy.

Abdominal muscles are selectively active in normal subjects during stress and may increase the potential energy for inspiration by reducing the end-expiratory lung volume (EELV). We hypothesized that a similar process would occur in subjects with myotonic muscular dystrophy (MMD), but would be less effective, because of to their weakness and altered chest wall mechanics. Fine-wire electromyography (EMG) of the transversus abdominis (TA), internal oblique (IO), external oblique, and rectus abdominis was recorded in 10 MMD and 10 control subjects. EMG activity, respiratory inductive plethysmography, and gastric pressure were recorded during static pressure measurement and at increasing levels of inspiratory resistance breathing. EELV was reduced and chest wall motion was synchronous only in controls. Although the TA and IO were selectively recruited in both groups, EMG activity of the MMD group was twice that of controls at the same inspiratory pressure. In MMD subjects with mildly reduced forced vital capacity, significant differences can be seen in abdominal muscle recruitment, wall motion, work of breathing, and ventilatory parameters.

Predictors of loss of lung function in the elderly: the Cardiovascular Health Study.

Pulmonary function, as measured by spirometry (FEV1 or FVC), is an important independent predictor of morbidity and mortality in elderly persons. In this study we examined the predictors of longitudinal decline in lung function for participants of the Cardiovascular Health Study (CHS). The CHS was started in 1990 as a population-based observational study of cardiovascular disease in elderly persons. Spirometry testing was conducted at baseline, 4 and 7 yr later. The data were analyzed using a random effects model (REM) including an AR(1) error structure. There were 5,242 subjects (57.6% female, mean age 73 yr, 87.5% white and 12.5% African-American) with eligible FEV1 measures representing 89% of the baseline cohort. The REM results showed that African-Americans had significantly lower spirometry levels than whites but that their rate of decline with age was significantly less. Subjects reporting congestive heart failure (CHF), high systolic blood pressure (> 160 mm Hg), or taking beta-blockers had significantly lower spirometry levels; however, the effects of high blood pressure and taking beta-blockers diminished with increasing age. Chronic bronchitis, pneumonia, emphysema, and asthma were associated with reduced spirometry levels. The most notable finding of these analyses was that current smoking (especially for men) was associated with more rapid rates of decline in FVC and FEV1. African-Americans (especially women) had slower rates of decline in FEV1 than did whites. Although participants with current asthma had a mean 0.5 L lower FEV1 at their baseline examination, they did not subsequently experience more rapid declines in FEV1.

Pursed lips breathing improves ventilation in myotonic muscular dystrophy.

OBJECTIVE: To determine the effects of pursed lips breathing on ventilation, chest wall mechanics, and abdominal muscle recruitment in myotonic muscular dystrophy (MMD). DESIGN: Before-after trial. SETTING: University hospital pulmonary function laboratory. PARTICIPANTS: Eleven subjects with MMD and 13 normal controls. INTERVENTION: Pursed lips breathing. OUTCOME MEASURES: Electromyographic (EMG) activity of the transversus abdominis, external oblique, internal oblique, and rectus abdominis was recorded with simultaneous measures of gastric pressure, abdominal plethysmography, and oxygen saturation. Self-reported sensations of dyspnea, respiratory effort, and fatigue were recorded at the end of each trial. RESULTS: Pursed lips breathing and deep breathing led to increased tidal volume, increased minute ventilation, increased oxygen saturation, reduced respiratory rate, and reduced endexpiratory lung volume. Dyspnea, respiratory effort, and fatigue increased slightly with pursed lips breathing. EMG activity of the transversus abdominis and internal oblique muscles increased in MMD only and was associated with an increase in gastric pressure. CONCLUSIONS: Pursed lips breathing and deep breathing are effective and easily employed strategies that significantly improve tidal volume and oxygen saturation in subjects with MMD. Abdominal muscle recruitment does not explain the ventilatory improvements, but reduced end-expiratory lung volume may increase the elastic recoil of the chest wall. Further clinical studies are needed to ascertain if the ventilatory improvements with pursed lips breathing and deep breathing improve pulmonary outcomes in MMD.

Noninvasive ventilation in neuromuscular disease.

The treatment of respiratory failure in patients who have NMD continues to be an evolving process. Negative-pressure ventilation, once prominent in the 1940s and 1950s, gave way to intermittent positive-pressure ventilation with tracheostomy or endotracheal tubes in the 1960s. Now there is a resurgence of noninvasive ventilation, brought about by innovative modes of positive pressure delivered through nasal and facial masks. Although frequently relegated to second-line choices, negative-pressure devices still offer a practical treatment alternative as patient preference still plays a role in selecting a proper mode of ventilation. Studies have shown that noninvasive ventilation can prevent or reverse respiratory failure and improve quality of life and longevity. Despite the seemingly widespread acceptance of noninvasive ventilation in the treatment of respiratory failure, physicians still appear reluctant to use ventilatory assistance in the neuromuscular arena. In 1985, a survey found that respiratory support systems were utilized routinely in only 33% of the 132 responding Muscular Dystrophy Association (MDA) clinics. Bach recently surveyed 273 MDA clinic directors and co-directors from 167 clinics, to evaluate their current use of mechanical ventilation. Ventilatory assistance was recommended and used electively in only 43 (26%) of the 167 clinics. Furthermore, it was the policy in 68 of the clinics to discourage the use of mechanical ventilation. Even more importantly, only 2 physicians who discouraged the use of mechanical ventilation were familiar with the newest noninvasive methods of ventilatory support. Sadly, although our methodologies in the treatment of respiratory failure continue to improve, physician practice has lagged behind. Physicians who treat patients who have NMD need to become cognizant of these new techniques and incorporate them into their present therapeutic armamentarium.

Successful pregnancies in the presence of spinal muscular atrophy: two case reports.

We report two cases of successful pregnancy in women with chronic, infantile onset, or type II spinal muscular atrophy, both of whom delivered healthy, unaffected babies. The patients required concurrent management by a physiatrist, pulmonologist, and perinatologist throughout the pregnancy. Complications included recurrent urinary tract infections, dyspnea and worsening of pulmonary function, wheelchair seating and positioning problems, and musculoskeletal and low back pain. These problems resolved postpartum. One woman had vaginal delivery, the other had caesarean section, both of which were well-tolerated. Because of severe musculoskeletal deformity, pelvic assessment is necessary to determine the mode of delivery. The uterus has normal contractility and effective labor patterns can be established. Spinal/epidural anesthesia may be contraindicated because of spine deformity. The pregnancies had no deleterious effect on the progression of the disease in our patients, both of whom reported a positive experience with great personal fulfillment.

Laryngeal diversion in the treatment of intractable aspiration in motor neuron disease.

Motor neuron disease/amyotrophic lateral sclerosis (MND/ALS) often causes bulbar palsy with subsequent aspiration. Laryngeal diversion procedures are not commonly mentioned in the literature. However, they are viable but infrequently used surgical treatment options that have several advantages over a routine tracheostomy. We report a case of a 67-year-old man with MND/ALS and severe aspiration. He underwent a laryngeal diversion procedure with complete relief of signs and symptoms of aspiration. Laryngeal diversion, unlike tracheostomy, completely eliminates the possibility of aspiration as well as the need for suctioning. The primary disadvantage is complete loss of phonation. These procedures appear worthy of trial in patients with MND/ALS, and may ultimately be the preferred treatment in this setting.

Evaluation of phrenic nerve and pulmonary function in hereditary motor and sensory neuropathy, type I.

Phrenic nerve and diaphragmatic dysfunction has been assumed to be the cause of respiratory failure in hereditary motor and sensory neuropathy, type 1 (HMSN I). In order to determine the relationship between phrenic nerve and pulmonary function in this disease, 25 patients underwent a 4-step evaluation process consisting of: (1) bilateral phrenic nerve conduction study; (2) median, peroneal, and tibial motor conduction studies; (3) measurement of forced vital capacity (FVC) and maximal inspiratory and expiratory pressures (MIP, MEP); and (4) pulmonary-focused history and physical. Phrenic nerve motor latency was abnormally prolonged in 22 of the 23 (96%) subjects when a response was obtained. All had slowed velocity or absent peripheral motor conduction responses. Vital capacity was abnormally reduced in 6 of the 25 (24%) subjects. Eight (32%) had an abnormally reduced MIP, while 19 (76%) had an abnormally reduced MEP. Only 2 (8%) subjects had clinical evidence of pulmonary dysfunction. None of the dependent variables (FVC, MIP, MEP, peripheral nerve conduction, or clinical examination) correlated with phrenic nerve latencies. Although phrenic nerve latencies are markedly prolonged in HMSN I, these values are not useful in predicting respiratory dysfunction.

Obstructive disordered breathing during sleep in patients with spinal cord injury.

Little is known about respiration and sleep in spinal cord injured (SCI) patients, and yet they frequently have complaints related to sleep. Four SCI patients with various sleep complaints were evaluated with nocturnal polysomnography. All 4 had evidence of obstructive sleep apnea (disordered breathing). These findings suggest that obstructive sleep apnea may be contributing to disruptive sleep in SCI patients and may be responsible for many of their daytime symptoms.

Age and fitness effects on EEG, ERPs, visual sensitivity, and cognition.

Measures of EEG, event-related potentials (ERPs), visual sensitivity, and cognition were obtained from 30 young (20-31 years) and 30 older (50-62 years) healthy men. Age groups were evenly divided between subjects with low and high fitness levels documented by VO2max during a maximal exercise test. Age comparisons revealed that, compared to young adults, the older men had reduced visual sensitivity, delayed ERP latencies, greater homogeneity of EEG activity across recording sites, more positive visual-evoked potential (VEP) amplitude-intensity (A/I) slope, and poorer performance on a battery of neurocognitive tests. The EEG and VEP A/I slope findings are believed to reflect weakened central inhibition for the older men. In general, the measures that differentiated groups on the basis of age were also sensitive to differences in aerobic fitness. Compared to low fit men, the physically active men had shorter ERP latencies, stronger central inhibition, better neurocognitive performance, and better visual sensitivity. We speculate the performance superiority of the physically active men was, at least in part, the result of more oxygen being available for cerebral metabolism.

Diagnosis of obstructive sleep apnea.

The diagnosis of obstructive sleep apnea is frequently made by taking a meticulous history coupled with a high index of suspicion. Snoring and hypersomnolence are clinical features common to individuals with sleep apnea. Since snoring is said to be a "disease of listeners," it is not uncommon that bed partners reported an increased incidence of depression and marital displeasure. It is for this reason that the spouse or bed partner should be interviewed, since the patient may not be aware of any sleeping problems. Physicians should also be alert to complaints of excessive daytime somnolence, because studies have shown that patients with obstructive sleep apnea are at increased risk for automobile crashes. It has been estimated that approx 58,000 motor vehicle accidents involving people with sleep apnea will occur in the US each yr. By proper diagnosis and treatment, the physician is in a unique position to prevent at least some of the automobile accidents that result from falling asleep while driving. Polysomnography is the only definitive way to obtain a diagnosis of sleep apnea. This allows the physician not only to diagnosis the disorder, but also helps in the evaluation of the severity of the syndrome and selection of therapy. An ENT evaluation is also important in ruling out anatomic disorders that can cause upper airway obstruction. Certain factors, such as alcohol and sedative ingestion, may aggravate the condition in a person predisposed to sleep apnea, and subtle changes, such as unexplained hypertension, polycythemia, and cor pulmonale, should lead one to investigate the possibility of sleep apnea as the etiology.

Smoking and cough syncope: follow-up in 45 cases.

A follow-up review of 45 patients with cough syncope was performed to ascertain the effect of therapy in relieving symptoms. These patients constituted 2.5% of all Mayo Clinic patients evaluated over a 3-year period for syncope. Cough syncope patients were predominantly male (43:2), the average weight was 96.1 kg, and the average age was 53.2 years. Eighty-two percent were current or ex-smokers at the time of the initial evaluation and 86% of those having pulmonary function tests demonstrated findings consistent with obstructive lung disease. Treatment was determined by their primary physician and, in general, was aimed at decreasing the cough. Cough-related symptoms were abolished or improved in 97% of patients. Smoking cessation was closely associated with decreased symptoms. Although felt by both patient and physician to be a benign disorder, cough syncope can result in severe bodily injury. Patients with a vigorous cough, especially smokers, should be questioned thoroughly about cough syncope. Treatment of cough is effective in relieving symptoms.

Exercise performance and ventilatory response in the menstrual cycle.

We investigated the effects of the luteal phase of the menstrual cycle, as compared with the follicular phase, on ventilatory response (VR) and exercise performance in eight normally menstruating, non-athletic women. Subjects were studied near the predicted mid-point of each phase which was later documented by serum progesterone level. Resting VR to hypercapnia was greater, and VR to hypoxia tended to be greater in the luteal phase than in the follicular phase, but the increases in VRs were unrelated to progesterone level. There were no differences in maximal oxygen uptake, maximal duration of exercise, maximal heart rate, work efficiency, maximal ventilation (VE), anaerobic (ventilatory) threshold, gas exchange, cardiac output, or oxygen delivery. The PaCO2 was lower, and pHa tended to be higher during exercise. VE per unit CO2 output (VE/VCO2) was increased. R values (VCO2/VO2) were less, and maximal lactate values tended to be less, suggestive of increased dependence on fat for energy metabolism. At a given workload, exercise VE was unchanged due to the effect of less CO2 output at a given VO2 (lower R), balancing increased VE/VCO2. We conclude that, although ventilatory parameters are altered by the menstrual cycle, there is no overall effect on maximal exercise performance.

Progesterone-induced changes in exercise performance and ventilatory response.

To further study the relationship between ventilatory response (VR) and exercise performance, and to investigate to what extent progesterone is responsible for ventilatory changes in the luteal phase of the menstrual cycle, we administered medroxyprogesterone acetate (MPA) to 10 normal males (20 mg three times a day for 5 doses) and compared results with those obtained in a similar study of females. With MPA, there was an increase in the resting VR to hypercapnia; the resting VR to hypoxia was not changed. There was a respiratory alkalosis at rest. During exercise, the PaCO2 remained lower but the pHa was not different because of a tendency toward lower bicarbonate concentration with MPA. Ventilation, when related to CO2 output, was increased at all exercise loads, indicating increased VR to endogenous CO2. However, ventilation was only minimally (3%) increased when related to oxygen uptake or workload. This apparent disparity is because of slightly lower CO2 output at a given oxygen uptake with MPA. As in females, maximal duration of exercise and maximal oxygen uptake were unchanged. Except for degree, MPA induced all the ventilatory changes seen in the menstrual cycle. Increased VR does not adversely affect exercise performance.

Concomitant pulmonary thromboembolism and metallic mercury embolism. A diagnostic dilemma.

The concomitant occurrence of mercury emboli and thromboemboli of the lung has not been previously reported. We describe the case of an intravenous drug abuser with chest pain and newly discovered mercury emboli in the lung who was found to have a thromboembolus in the right pulmonary artery. An echocardiogram showed metallic density in the right ventricle, which has not been demonstrated previously.

Direct and indirect blood pressure during exercise.

In 27 subjects, we compared rest and exercise blood pressure (BP) measurements determined directly by catheterization of the radial artery with simultaneous values obtained indirectly by auscultation of the brachial artery. As work increased, the systolic BP increased, whereas the diastolic BP did not change. Considering all comparisons, direct BP was greater than indirect BP by a mean of 29.0 mm Hg for systolic BP and 12.3 mm Hg for diastolic BP. As exercise level increased, the difference between direct and indirect systolic BP decreased whereas the difference between direct and indirect diastolic BP did not change. Both methods have advantages for assessment of BP response to exercise: normality of BP response is best assessed by auscultation, whereas beat-by-beat trends in BP are more accurately defined by the direct method.

Disinfection of the flexible fibreoptic bronchoscope against Mycobacterium tuberculosis and M gordonae.

In view of recent reports of contamination of the fibreoptic bronchoscope by tuberculous and non-tuberculous mycobacteria, we evaluated the disinfecting properties of aqueous glutaraldehyde (Cidex) and an iodophor (Prepodyne) against Mycobacterium tuberculosis and M gordonae. We found that a 15 minute disinfection procedure with either agent, coupled with initial vigorous mechanical cleaning of the bronchoscope and its accessories, is a quick and reliable method for preventing the contamination of the bronchoscope with mycobacteria.

Chest wall motion in sleep apnea.

Patterns of rib cage (RC) and abdomen (ABD) motion obtained from a respiratory inductive plethysmograph were studied during disordered breathing events - obstructive apnea, obstructive hypopnea, mixed apnea, and central apnea - in 54 patients with sleep apnea. The type of disordered breathing event was verified by esophageal pressure and bias-flow mask recordings. Obstructive apnea occurred to a variable extent in all patients and was characterized by stereotyped paradoxical motion of the RC or ABD or both in 49 patients (91%). There was no paradox in 2 patients with "feeble" inspiratory effort during obstructions and in 3 patients with normal inspiratory effort during obstructed breaths. The more obese patients displayed paradox of the ABD rather than of the RC. Paradox did not occur in central apnea or in the central component of mixed apnea. Obstructive hypopnea was characterized by paradox during part of the breath. We conclude that RC and ABD motion can adequately characterize apnea in most patients and thus avoid invasive monitoring techniques that can adversely affect sleep. However, if chest wall motion suggests that all apneas are central, a direct measurement of respiratory effort is necessary to exclude obstruction.

Factitious methemoglobinemia caused by hyperlipemia.

Hyperlipemia in an acyanotic patient with diabetic ketoacidosis, alcoholism, and pancreatitis produced a falsely elevated concentration of methemoglobin (19 percent) and a lower-than-expected oxygen saturation measured with an automated spectrophotometer (IL-282 CO-Oximeter). In addition, there was a "normal" hemoglobin level despite a low hematocrit reading. In vitro studies showed that hyperlipemia corresponding to triglyceride levels of 500 mg/100 ml and greater produced erroneously high values for methemoglobin and total hemoglobin and "negative" values for carboxyhemoglobin. These abnormalities disappeared when the excessive lipids were removed by washing the erythrocytes in physiologic saline solution.

Aerobic exercise training and improved neuropsychological function of older individuals.

The effects of a four month aerobic exercise conditioning program on neuropsychological test performance, depression indices, sensory thresholds, and visual acuity of 55-70 year old sedentary individuals were evaluated. Aerobically trained subjects were compared with two age-matched control groups of subjects: those who trained with strength and flexibility exercises and others who were not engaged in a supervised exercise program. The aerobically trained subjects demonstrated significantly greater improvement on the neuropsychological test battery than did either control group. Depression scores, sensory thresholds, and visual acuity were not changed by aerobic exercise. The pattern of results suggests that the effect of aerobic exercise training was on central rather than on peripheral function. We speculate that aerobic exercise promoted increased cerebral metabolic activity with a resultant improvement in neuropsychological test scores.