[Respiratory disorders in type-1 hereditary motor and sensory neuropathy]

Type-1 hereditary motor and sensory neuropathy (HMSN I) is a slowly progressive disease resulting in distal muscle weakness with atrophy, and in sensory disturbance. Restrictive lung disease and respiratory muscle failure, common in many advanced neuromuscular disorders, is not a predominant feature of HMSN-I. Recently, there have been several reports of respiratory dysfunction in patients with HMSN I, complicated by diaphragmatic weakness. In five patients with HMSN I (3 men and 2 women, mean age 55.4 yrs), we measured spirometric variables, maximal inspiratory pressure, and maximal expiratory pressure, in both sitting and supine positions. We also studied phrenic nerve conduction by cutaneous stimulation at the posterior border of the sternocleidomastoid muscle. Four of five patients had low maximal inspiratory pressure and abnormally long phrenic nerve latency. Two patients showed evidence of a restrictive lung disorder and daytime alveolar hypoventilation. All-night polysomnography in those two patients revealed periodic decreases in arterial blood oxygen saturation, and episodes of central apnea. We conclude that diaphragmatic dysfunction is not rare in HMSN I, and that maximal inspiratory pressure and phrenic nerve conduction may be useful in the early detection of phrenic nerve involvement.

Temporal relationships of ventilatory failure, pump failure, and diaphragm fatigue

The time course of ventilatory failure, pump failure, and diaphragm peripheral fatigue was determined during the application of external inspiratory resistive loads (IRL) in anesthetized rabbits. Pump failure is defined as the inability of the diaphragm to sustain the expected force under IRL. To assess contractile fatigue, transdiaphragmatic pressures (Pdi) generated by bilateral phrenic nerve stimulation at 75 Hz (Pdi-75) and 20 Hz (Pdi-20) were measured. The amplitude of evoked diaphragm electromyographic (EMG) signals was measured to assess neurotransmission failure. The rate of rise of spontaneous diaphragm EMG was used as an index of respiratory drive. Ventilation was evaluated together with arterial blood gases. During IRL the rate of rise of spontaneous diaphragm EMG increased, and there was a progressive hypercapnic acidosis and hypoxemia, indicating ventilatory failure. In contrast, Pdi-75 and Pdi-20 were stable until the time of respiratory arrest (apnea), when they decreased by 34 and 45%, respectively. The amplitude of evoked diaphragm EMG signals remained unchanged throughout the IRL and decreased only slightly at the time of apnea. We conclude that IRL induces progressive ventilatory failure long before any contractile fatigue of the diaphragm or pump failure occurs. This suggests that ventilatory failure is due to central fatigue, whereas pump failure (apnea) is attributable to multiple factors.

Hypothyroid-mediated changes in adult rat diaphragm muscle contractile properties and MHC isoform expression

The purpose of the present study was to examine the effect of acute hypothyroidism on myosin heavy chain (MHC) isoform composition and contractile properties in the adult rat diaphragm muscle. Hypothyroidism was induced by the addition of propylthiouracil (0.05%) in the drinking water for a period of 3 wk. MHC isoform composition of control and hypothyroid diaphragm muscles was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In vitro isometric contractile properties of midcostal diaphragm muscle segements were measured at 26 degrees C, whereas the maximal unloaded shortening velocity was measured at 15 degrees C with the "slack test" method. Serum triiodothyronine and thyroxine values were significantly lower in the hypothyroid compared with the control group. A small but significant increase in the percentage of slow MHC isoform in the diaphragm was observed with acute hypothyroidism, whereas the percentage of the fast MHC isoforms (2A, 2X, and 2B) did not significantly differ between groups. Peak twitch force did not differ between groups. However, twitch contraction and half-relaxation times were significantly prolonged in the hypothyroid group compared with control. Maximal specific force was reduced in the hypothyroid compared with the control group, averaging 15.7 and 19.8 N/cm2, respectively (P < 0.05). The maximal unloaded shortening velocity averaged 4.3 and 8.2 muscle lengths/s in the hypothyroid and control groups, respectively (P < 0.05). We conclude that acute hypothyroidism results in alterations in adult diaphragm muscle contractile properties that cannot be attributed solely to changes in MHC isoform composition.

N-acetylcysteine inhibits loss of diaphragm function in streptozotocin-treated rats

We examined whether streptozotocin (STZ)-induced diabetic rats have an impairment in diaphragm contractility, and if so, whether N-acetylcysteine (NAC), a nonspecific antioxidant, prevents this impairment. First, diaphragm contractility, assessed by tension-frequency relationships and twitch kinetics in in vitro diaphragm strip preparations of Wistar rats, was obtained on Days 3 and 7 after administration of STZ of 30 or 60 mg/kg body weight, and compared with that of the control group. Second, NAC at 500 mg/kg body weight or vehicle solution was administered orally every day in rats treated with STZ at 60 mg/kg body weight, and diaphragm function on Day 7 after starting NAC treatment was compared between vehicle control and STZ-treated groups. We found that diaphragm function in STZ-treated rats, which had hyperglycemia, decreased in a dose- and time-dependent manner. NAC inhibited the decrease in diaphragm contractility in STZ-treated rats without reducing blood glucose. These findings suggest that the loss of diaphragm function in STZ-induced diabetic rats is not directly related to hyperglycemia. The data are consistent with secondary alterations of normal cytokine signaling or changes in the redox state of the cell, both of which could be affected by NAC treatment.

Diaphragm function in patients with cervical cord injury or prior poliomyelitis infection

Diaphragm function was evaluated in cervical cord injury patients (CCI), 1-3 years after injury (CCI(1-3)) and 10 years or more after injury (CCI(> or = 10)), as well as in a group of prior poliomyelitis infection patients (PPI), requiring intermittent positive pressure ventilation (IPPV) for about 6 h per night. Measurements included transdiaphragmatic pressure swings (delta Pdi) at rest, during maximal inspiratory efforts against closed airways (delta Pdi(max)) and during sniff manoeuvres (ie maximal inhalation through the nose, delta Pdi(sniff)), vital capacity normalized to age and height (VC(%pred)), tidal volume (Vt), relative inspiratory time (Ti/Ttot), breathing frequency (f(b)), and the tension-time index of the diaphragm (TTdi = delta Pdi/delta Pdi(max) x Ti/Ttot). The median VC(%pred) was 50% in the CCI(1-3) group and 57% in the CCI (> or = 10) group, but only 28% in the PPI group. Delta Pdi(max) values were similar for the CCI(1-3) (11.8 kPa) and CCI(> or = 10) (11.9 kPa) groups but were lower (71. kPa) in the PPI group. Due to the reduction in delta Pdi(max), the PPI group had higher delta Pdi/delta Pdi(max) values than the CCI groups, however, the TTdi was similar amongst the different groups studied. A submaximal exercise test in five cervical cord injury patients and in five polio patients with similar delta Pdi(max), delta Pdi(sniff) and TTdi values at rest revealed clear group differences with respect to force development, in that CCI patients showed significant increases in TTdi, while PPI demonstrated only minor changes. In CCI patients, an increase in ventilation was accompanied by an increase in delta Pdi/delta Pdi(max) while in contrast, the PPI patients showed no increase in delta Pdi/delta Pdi(max). We conclude that CCI patients, both recently and previously injured, have a similar maximal inspiratory force and are less impaired than the PPI patients. The TTdi at rest is similar in all groups, but the PPI patients react to inspiratory loads with little increases in TTdi, while the CCI patients increase their TTdi above fatiguing (0.15) levels. The different behaviours may be linked to loss of sensory pathways in the CCI patients.

The tension-time index of the diaphragm revisited in quadriplegic patients with diaphragm pacing

The fatigue threshold of the human diaphragm, index of its endurance and fatigability, corresponds, during spontaneous breathing, to a tension-time index (TTdi = Pdi/Pdimax x T1/Ttot (i.e., the inspiratory time over the total breath duration) of 0.15 to 0.18. We studied three quadriplegic patients with diaphragm pacing in order to reassess this threshold in patients in whom the contribution of the other respiratory muscles is lacking. Transdiaphragmatic pressure (Pdi) was obtained from the difference between gastric (Pga) and esophageal (Pes) pressures while the electromyograms (EMG) of both hemidiaphragms were recorded with surface electrodes. Four runs at different TTdi were performed on different days in each subject, varying either the Pdi developed per breath, changing the frequency of stimulation, or the T1/Ttot. The time of fatigue was defined when Pdi decreased during the trials by 35% from baseline. No evidence of transmission fatigue (i.e., decline in action potential amplitude) was observed. The TTdi at which fatigue occurred in all the quadriplegic patients was around 0.10 to 0.12, well below the values previously described. After fatigue had occurred, the force recovery during the force-frequency curve was not complete after 2 h at low frequencies, whereas at high frequencies it was fully complete at 30 min. We conclude that when respiration is accomplished only by the diaphragm, without the contribution of the other respiratory muscles, the fatigue threshold is lower than previously reported.

Congenital diaphragmatic eventration: treatment and postoperative evaluation

Three patients with congenital diaphragmatic eventration have been reported. The diagnosis was established by chest radiography which showed an abnormally elevated diaphragm. Additionally fluoroscopy, ultrasonography and pulmonary function tests were used. Diaphragmatic plication was performed in order to restore normal pulmonary parenchymal volume and the diaphragm was replaced in its normal localization. All the patients had been discharged in good condition following uneventful postoperative courses. In this study we discussed the etiology, diagnosis, treatment and postoperative courses of diaphragmatic eventration.

[Epidural buprenorphine does not improve diaphragmatic function after upper abdominal surgery]

We investigated the effect of epidural buprenorphine on diaphragmatic function using respiratory inductive plethysmography (RIP) in seven healthy patients after upper abdominal surgery. After surgery, changes of rib cage contribution to tidal volume (%RC) increased significantly from 25.3 +/- 7.3 (mean +/- SD) to 50.7 +/- 14.8% (P < 0.05). After the injection of epidural buprenorphine, visual analogue scale (VAS) score decreased significantly from 8.3 to 3.3 (P < 0.05). But, %RC was unchanged compared to the value before the injection. These results indicate that pain relief by epidural buprenorphine does not improve diaphragmatic function after upper abdominal surgery.

[A quantitative study on the effect of breathing exercises in improving respiratory muscle contration]

To study quantitatively the effect of breathing exercises on the prevention of progression in chronic obstructive pulmonary disease (COPD), 324 patients with stable COPD were randomly assigned to either breathing exercises (BE) or placebo medicine as control. The maximum respiratory pressure (320 cases) and transdiaphragmatic pressure (129 cases) were monitored with RMS-1 and Type-2 gastrointestinal pressure measuring instrument. BE were taught and checked by experienced specialists periodically. Patients in BE group were compared with those in the control group by measuring MIP, MEP, Pdi, and Pdimax after one to 20 months. In BE group MIP increased by 30.42%, MEP 32.10%, Pdi 30.94%, and Pdimax 65.59% (P < 0.001). No significant change was observed in the control group. MIP, MEP, Pdi, and Pdimax increased by 6.95%, 2.92%, 14.63% and 9.05% respectively (P < 0.05) in the control group. It is shown preliminarily that BE had potent and lasting effect on respiratory muscle contraction after studying large number of cases. The methods mentioned above can be used as quantitative indices for the contractile properties of respiratory muscle.

Electromyographical and motor performance studies in the pmn mouse model of neurodegenerative disease

The mouse autosomal recessive mutation progressive motor neuronopathy (pmn) results in early onset motor neuron disease with rapidly progressive hindlimb paralysis, severe muscular wasting, and death at around 6 weeks of age. This mutant provides opportunities for testing novel therapeutic strategies, including the administration of trophic factors, to prevent the degeneration of diseased neurons. The construction of a strain expressing the pmn and the Extra-toe (Xt) phenotypes allows the detection, and therefore the treatment, of affected progeny before the onset of the clinical weakness. Electromyography is the most appropriate technique for a longitudinal study in which a given individual is examined repeatedly. We present the results of an electrophysiological and behavioral exploration of the pmn disease and show that electromyography is a powerful tool for following the course of the disease and evaluating potential therapies relevant to motor neuron diseases.

Effects of assisted ventilation on the work of breathing: volume-controlled versus pressure-controlled ventilation

During assisted ventilation, the same tidal volume can be delivered in different ways, with the possibility for the physician to vary the ventilatory target (pressure or volume) and the peak flow setting. We compared the effects on the respiratory work rate of assisted ventilation, delivered either with a square wave flow pattern (assist control ventilation [ACV]) or with a decelerating flow pattern and a constant pressure (assisted pressure-control ventilation [APCV]). In the first part of the study where seven patients were studied, inspiratory time and tidal volume were similar in the two modes of ventilation. High and moderate levels of tidal volume (VT) were studied (12 ml/kg and 8 ml/kg, respectively). To obtain moderate VT, inspiratory time was kept constant and, therefore, mean inspiratory flow was reduced. At high VT, no difference between ACV and APCV was noted for breathing pattern, respiratory drive indexes, respiratory muscle work, or arterial blood gases. All patients exhibited respiratory alkalosis. At moderate VT, normal pH was achieved. In this situation significantly lower levels were observed during APCV than during ACV for the power of breathing (10 +/- 2 versus 19 +/- 5 J/min, p<0.05), transdiaphragmatic pressure swing (7 +/- 1 versus 11 +/- 2 cm H2O, p<0.05), and pressure-time index (252 +/- 43 versus 484 +/- 114 cm H2O.s, p<0.05), even though breathing pattern and gas exchange were similar. In the second part of the study where six additional patients were studied, tidal volume was kept constant at a moderate level (8 ml/kg), and we studied the effect of shortening inspiratory time and increasing mean inspiratory flow. At moderate VT and high inspiratory flow, no significant differences could be found between ACV and APCV, and although pressure-time index tended to be lower during APCV, absolute levels of effort were of small magnitude (56 +/- 55 versus 76 +/- 55 cm H2O.s). We conclude that at moderate VT and low flow rates only, inspiratory assistance delivered at a constant pressure reduces the respiratory work rate more effectively than assist control ventilation.

Respiratory motor nerve activities during experimental seizures in cats

We evaluated respiratory motor nerve activities during experimental seizures induced with subcortical penicillin. The activities of the phrenic (PH), nasolabial (NL), and hypoglossal (HG) nerves and the recurrent laryngeal motor branches to the thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles were analyzed in 13 anesthetized, vagotomized, paralyzed, and ventilated cats. During ictal and interictal phases of seizures, nerve activities became irregular and peak integrated nerve activities increased, particularly in the case of the PH nerve. The ictal phase of seizures was associated with increased tonic activity and decreased phasic respiratory discharges, particularly in the cases of the HG, NL, and PCA nerves. During some prolonged ictal discharges, entrainment of nerve activities by cortical spiking was associated with irregular uncoordinated activation, particularly in the TA nerve. These studies help explain respiratory impairment during seizures by providing evidence of impaired coordination between activation of muscles that regulate upper airway patency and activation of the diaphragm.

Effect of alpha-adrenoreceptor stimulation on the diaphragmatic oxygen delivery-consumption relationship

PURPOSE

In the vascularly isolated canine hemidiaphragm, we tested the hypothesis that alpha-adrenoreceptor stimulation may influence diaphragmatic function and O2 extraction during reductions in O2 delivery (QO2di).

METHODS

The diaphragm was perfused using a constant flow pump with blood diverted from the left femoral artery. QO2di was reduced in a stepwise fashion by progressive reductions in pump flow. The tension generated by the contracting diaphragm (3 Hz), the critical O2 delivery (QO2di,c) below which O2 consumption (VO2di) becomes dependent on O2 supply and the oxygen extraction ratio at this critical point (ERc) were assessed in two groups of animals. Phenylephrine (10(-5) mol/L) was infused into the phrenic artery in one group and saline was infused in another group.

RESULTS

In the contracting diaphragm, VO2di was higher in the phenylephrine infused group than in the control group (5.2 +/- 0.5 vs 2.11 +/- 0.3 mL/min/100 g). QO2di,c and ERc were also higher in the phenylephrine group than in the control group (6.16 +/- 0.43 vs 3.1 +/- 0.5 mL/min/100 g and 0.87 +/- 0.035 vs 0.63 +/- 0.05, respectively). In the resting diaphragm, VO2di was not significantly different between the two groups and no critical oxygen delivery could be identified in either group.

CONCLUSIONS

These results indicate that alpha-adrenoreceptor activation may increase the tension generated by the diaphragm as well as its oxygen consumption and oxygen extraction. Although this may be beneficial during moderate reductions in oxygen delivery, in more severe shock states, activation of these receptors by endogenous or exogenously administered catecholamines may hasten the development of delivery limitation of VO2di and compromise the ability to sustain ventilation.

Interaction between hypoxia and hypercapnia in regulating canine diaphragm arteriolar diameter

In alpha-chloralose-anesthetized mongrel dogs, the microvascular responses to hypoxia and hypercapnia were studied in the vascularly isolated ex vivo left hemidiaphragm. The diaphragm was perfused with arterial blood diverted from the femoral artery by a pump. A series of membrane oxygenators was used to adjust the blood gas composition of the blood perfusing the diaphragm. Arteriolar diameters were measured by intravital microscopy during an infusion of sodium nitroprusside, moderate hypoxia (phrenic venous PO2 25 Torr), severe hypoxia (phrenic venous PO2 13 Torr), hypercapnia (phrenic venous PCO2 100 Torr), and a simultaneous presentation of hypoxia and hypercapnia. Recordings were made after 15 min under each condition when a steady state had been established for vessel diameter and flow. Pump speed was adjusted manually under each condition to ensure that the steady-state perfusion pressure was the same as that under the control condition. Moderate hypoxia generally resulted in dilation; however, vasoconstriction was seen in some arterioles. Severe hypoxia caused vasodilation that was inversely related to baseline vessel diameter and paralleled the response to sodium nitroprusside. Hypercapnia resulted in vasodilation of the diaphragmatic circulation at values of phrenic venous PCO2 > 80 Torr. The arteriolar response to hypercapnia was also inversely related to baseline vessel diameter. Hypoxia and hypercapnia in combination exerted an additive effect on arteriolar diameter but produced a greater than additive effect on blood flow. Both PO2 and PCO2 may contribute to the local regulation of diaphragmatic blood flow. The vasodilator effects of both hypoxia and hypercapnia are greater in smaller than in larger arterioles. The interaction between PO2 and PCO2 on arteriolar diameter is additive. An apparent synergistic effect on blood flow results from the power function relating diameter to flow.

The effects of serotonin antagonists in an animal model of sleep-disordered breathing

Recent studies have shown excitatory effects of serotonin on upper airway motoneurons. This excitatory effect is normally present and arises from cells in the caudal raphe nuclei. The firing of these serotonergic neurons is reduced during sleep. To determine the importance of serotonin in the maintenance of patient airways and normal respiration in waking in obstructive sleep apnea, we studied the effects of two serotonin antagonists on upper airway dilator muscle activity, diaphragm activity, Sao2, and upper airway cross-sectional area in an animal model of sleep-disordered breathing, the English bulldog. Systemic administration of both antagonists resulted in significant reductions in the peak amplitudes of upper airway muscle respiratory bursts (range, 39 to 62% suppression; p < 0.05). Lesser reductions in diaphragm activity were noted (range, 10 to 33% suppression; p < 0.05). Oxyhemoglobin saturations also fell (p < 0.05), coinciding with suppressions in upper airway muscle activity. With reductions in dilator muscle activity, upper airway cross-sectional areas, as measured with cine CT, showed significant inspiratory collapse. These results support the hypothesis that serotonin is important in the maintenance of patent upper airways in obstructive sleep apnea.

Exhaustive exercise slows inspiratory muscle relaxation rate in chronic obstructive pulmonary disease

The excessive load placed on inspiratory muscles when patients with COPD exercise could lead to fatigue and contribute to exercise limitation. Slowing of maximal relaxation rate (MRR) of skeletal muscle is an early index of the fatiguing process. We investigated whether inspiratory muscle MRR slows when patients with COPD walk to exhaustion. We studied nine well-trained and motivated patients with stable severe COPD (mean FEV1: 0.7 L, 28% predicted). Each subject performed sniff maneuvers before and after walking on a treadmill until they were forced to stop because of dyspnea. Esophageal (Pes), gastric, and transdiaphragmatic pressures were measured using balloon-tipped catheters. MRR was calculated as the percent Pes drop/10 ms. In the first minute after exercise there was a mean decrease of Pes MRR of 42% (range, 21 to 65%) (p < 0.01), which returned to baseline within 3 to 5 min. The fall in MRR indicates that the inspiratory muscles of patients with COPD walking to exhaustion are sufficiently heavily loaded to initiate the fatiguing process.

Hydroxocobalamin vs cobalt toxicity on rat cardiac and diaphragmatic muscles

BACKGROUND

Hydroxocobalamin has been shown to be a rapid and powerful antidote in acute cyanide poisoning and to prevent cyanide poisoning during sodium nitroprusside administration. This cobalt-containing compound has been shown to be devoid of significant immediate side effects during acute administration. However, its potential delayed toxicity related to cobalt accumulation in tissue remains unknown. Therefore, we evaluated the toxicity of hydroxocobalamin as compared with that of cobalt salts on rat cardiac and diaphragmatic muscles.

METHODS

For a 21-day period, rats were treated intraperitoneally with either hydroxocobalamin (70 mg kg-1 per day, n = 14), cobalt chloride hexahydrate (12 mg kg-1 per day, n = 14) or saline (n = 10). Hydroxocobalamin and cobalt chloride groups received equimolar doses of cobalt. We studied: (1) the mechanical properties of isolated left ventricular papillary muscles and diaphragmatic strips, (2) the cardiac and diaphragmatic cobalt tissue concentrations, and (3) the myocardial histological aspect.

RESULTS

During the study period, no significant increase in body weight was noted in the cobalt-treated group (-4 +/- 1%), which was in contrast to the hydroxocobalamin-treated group (+21 +/- 2%) and the saline-treated group (22 +/- 2%). Compared with controls, the mechanical properties of cardiac and diaphragmatic muscles were unchanged after either hydroxocobalamin or cobalt salt treatments, and myocardial histological characteristics were similar in all groups. Conversely, large amounts of cobalt deposit were observed in the cobalt-treated group in both the diaphragm (41.90 +/- 16.30 vs 0.70 +/- 0.40 mu mol mu g-1 in the control group, P < 0.001) and the myocardium (16.90 +/- 6.40 vs 0.14 +/- 0.01 mu mol mu g-1 in the control group, P < 0.001). After hydroxocobalamin administration, cobalt concentrations were significantly lower in the diaphragm (25.10 +/- 16.50 mu mol mu g-1, P < 0.001 vs cobalt-treated group) and the myocardium (4.50 +/- 1.20 mu mol mu g, P < 0.001 vs cobalt-treated group).

CONCLUSION

These results indicate that repeated administration of hydroxocobalamin was devoid of significant diaphragmatic and cardiac muscle toxicity and therefore remains a safe antidote for acute cyanide poisoning.

Development of the respiratory diaphragm in childhood: diaphragmatic contraction band necrosis in sudden death

The authors studied the respiratory diaphragm in 50 normally grown infants and children aged 1 to 16 years at the time of sudden death. By comparing the weights of both costal diaphragm and heart with age and height, the authors found that the diaphragm grows proportionately to the body as a whole and to the heart in particular. Diaphragmatic contraction band necrosis was found in 15 cases (30%). The incidence was similar in subjects dying of asphyxia (five of 21) to that in those dying of trauma (five of 20). It was present in two of 15 of those that died at once, and 13 of 35 of those who survived for varying periods with or without cardiopulmonary resuscitation. Myocardial contraction band necrosis was more common than diaphragmatic contraction band necrosis, being present in five of 11 of those who died at once, and 16 of 26 of those that survived for a period. Among individual subjects, the authors found no correlation of the presence of the diaphragmatic lesion with either cause or mode of death. Based on a comparison with the morphologically similar myocardial lesion, the etiopathogenesis of diaphragmatic contraction band necrosis may concern a local catecholamine effect.

Application of electrical impedance principle in the diagnosis of diaphragm fatigue

The chest and abdomen impedance respirographs (IRG), including the one dimensional IRG and the two dimensional IRG were designed and produced by applying the principle of bioelectrical impedance. Using IRG the non-synchronized chest and abdomen respiratory motions occurring in diaphragmatic fatigue were measured. The results showed that all 203 normal controls showed synchronized style of chest and abdomen respiratory motions. In 189 COPD patients 117 (61.9%) showed non-synchronized respiratory motions which could be further divided into three types: type I showed complete contra-directional respiratory movements of chest and abdomen respiration, with M > 24 % and alpha angel > 120 degrees; type II showed staggered peak of the chest and abdomen motion curves (13% < M < 24%), 50 degrees < alpha angle < 120 degrees; type III showed double peaks of abdomen trace in the one dimensional IRG and "8"-shaped double circles on the two dimensional IRG, (M < 13%, 50 degrees < alpha angle < 120 degrees. When compared with trans-diaphragmatic pressure (Pdi) and diaphragm myoelectricity frequency spectrum, the rates of conformity were 81.8% and 90%, respectively, suggesting that IRG could be reliably used for diagnosing diaphragmatic fatigue. This technique is simple, easy to use, cheap and pain-free.

[Effect of shengmai san on diaphragmatic function in rabbits]

After stimulation of the bilateral phrenic nerves of the rabbits, the effect of Shengmai San (SMS) on their normal function and the diaphragmatic fatigue was observed with the measuring of diaphragm evoked potential (DEP), and the analysis of the power spectrum of diaphragmatic electromyogram (EMGdi) at spontaneous breathing. The results were as follows: (1) After the administration of 2 ml/kg of SMS, amplitude of DEP, central frequency, and the high/low frequency ratio were markedly increased. (2) Injecting SMS in 2 ml/kg in 30 minutes before injury could protect significantly against diaphragmatic fatigue following electrical stimulation of the phrenic nerves. (3) Injecting SMS in 2 ml/kg after fatigue could enhance the recovery of the diaphragmatic fatigue.

Percutaneous magnetic coil stimulation of the phrenic nerve roots and trunk

We describe a technique of percutaneous magnetic coil (MC) stimulation of the phrenic nerve trunk on one side of the neck and phrenic roots over the upper cervical vertebral column in 10 normal subjects and 2 patients. We were able to obtain compound muscle action potentials (CMAPs) from the diaphragm at two sites (xiphoid process and 7th intercostal space) after stimulation of the phrenic nerve trunk and roots. We noted that the onset latencies after phrenic root stimulation remained fixed despite increasing the stimulus intensity from 50% to 100% and on moving the MC vertically or laterally, suggesting that stimulation of the fastest conducting fibers was occurring at a fixed site, most likely at the intervertebral foramina. Absent responses unilaterally in one and prolonged latencies to diaphragmatic CMAPs in another patient confirmed phrenic neuropathy in these patients.

Sympathetic skin response in patients with Duchenne muscular dystrophy

To verify an eventual disfunction of the palmar sympathetic skin activity in Duchenne Muscular Dystrophy, we studied the sympathetic skin response (SSR) with endogenous, Deep Breathing (DB-SSR), exogenous Startle (SE-SSR) and Electric type stimuli (EE-SSR) in a group of patients and a control group. At the same time as the SSR, the heart rate (HR) and the basic R-R interval variation (RRIV) as well as the EMG diaphragmatic activity were checked. In this way, significant differences in the latency (p = 0.02) and amplitude (p = 0.009) values of the EE-SSR and in the amplitude values of the SE-SSR (p = 0.001) and of the DB-SSR (p = 0.02) were noted in the DMD group compared to the control group. In the group of patients the rise in latency of the EE-SSR correlates with the age (p = 0.0001) and with the reduction of its amplitude (p = 0.03). This last parameter correlates with the stage of the illness (p = 0.02). In the control group the mean amplitude of the EE-SSR is approximately 30% greater than that of startle and 50% of deep breathing. Although with amplitudes homogeneously reduced, these ratios are also conserved in the DMD group. Moreover the HR is greater (p = 0.0001) whilst the RRIV is reduced (p = 0.02) in the group of the patients. However these parameters do not correlated either to the cardiac involvement or to the stage of the illness. The presence of the SSR for all the modalities of stimulation indicates the substantial integrity of the afferent and the efferent paths of the ANS. The alterations in latency and amplitude of the SSR in the patients could be the consequence of a lack of dystrophin at the level of the sudoriparous myopithelium in analogy to what has been demonstrated in the mdx mouse.

Involvement of respiratory muscles in adult-onset dystonia: a clinical and electrophysiological study

Involvement of respiratory muscles is unusual in dystonia, but its occurrence may be underestimated either because it is not conspicuous or because it is improperly imputed to another cause. Three patients who had adult-onset dystonia and who were exhibiting respiratory problems were examined clinically and electrophysiologically. In the three patients the onset was focal-cervical in two and blepharospasm in one. The respiratory problems appeared later. The first patient had involuntary deep and loud inspirations combined with spasms of axial dystonia, the second complained of breathing arrests, and the third had deep inspirations mainly on speaking or reading aloud, thus causing broken speech. Electromyographic findings, including of the diaphragm, were quite consistent with a respiratory involvement in these three cases of dystonia. Assuming that respiratory troubles could be in the first sign of a focal dystonia, electrophysiological studies of respiratory muscles could be used to confirm this.