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PubMed1986

Effects of hypercapnia and hypoxemia on fetal breathing after decortication.

The effects of hypercapnia and hypoxemia on breathing movements were studied in 12 chronically decorticated fetal sheep, 127-140 days gestation. The fetal state of consciousness was defined in terms of activity of the lateral rectus and nuchal muscles. Arterial blood pressure was monitored. Fetal breathing was determined by integrated diaphragmatic electromyogram (EMG) and analyzed in terms of inspiratory time (TI), expiratory time (TE), electrical equivalent of tidal volume (EVT), breath interval (TT), duty cycle (TI/TT), mean inspiratory flow equivalent (EVT/TI), and instantaneous ventilation equivalent (EVT/TT). Fetal breathing occurred only during episodes of rapid-eye movements, and the response to hypercapnia consisted of an increase in EVT, TI, EVE, and EVT/TI and a decrease in the coefficient of variation of all measured parameters. Induction of hypoxia during episodes of spontaneous fetal breathing produced a decrease in the rate of breathing and an increase in EVT and TI with no change in the variability of all parameters studied. Since similar responses to hypercapnia and hypoxemia are seen in the intact fetus, we conclude that the cerebral cortex has no obvious effect on the chemical control of fetal breathing.

Animals↗

PubMed2002

Mask proportional assist vs pressure support ventilation in patients in clinically stable condition with chronic ventilatory failure.

OBJECTIVE: To compare the short-term physiologic effects of mask pressure support ventilation (PSV) and proportional assist ventilation (PAV) in patients in clinically stable condition with chronic ventilatory failure (CVF). DESIGN: Randomized, controlled physiologic study. SETTING: Lung function units of two pulmonary rehabilitation centers. PATIENTS: Eighteen patients with CVF caused by COPD (11 patients) and restrictive chest wall diseases (RCWDs) [7 patients]. METHODS: Assessment of breathing pattern and minute ventilation (E), respiratory muscles and lung mechanics, and patient/ventilator interaction during both unassisted and assisted ventilation. After baseline assessment during spontaneous breathing (SB), mask PSV and PAV were randomly applied at the patient's comfort, with the addition of the same level of continuous positive airway pressure (2 cm H2O or 4 cm H2O in all patients), for 30 min each, with a 20-min interval of SB between periods of assisted ventilation. RESULTS: A longer time was spent to set PAV than PSV (663 +/- 179 s and 246 +/- 58 s, respectively; p < 0.001). Mean airway opening pressure (Pao) computed over a period of 1 min, but not peak Pao, was significantly lower with PAV than with PSV (151 +/- 45 cm H2O/s/min and 207 +/- 73 cm H2O/s/min, respectively; p < 0.002). Tidal volume (VT) exhibited a greater variability with PAV than with PSV (variation coefficient, 16.3% +/- 10.5% vs 11.6% +/- 7.7%, respectively; p < 0.05). Compared with SB, both modalities resulted in a significant increase in VT (by 40% and 36% with PAV and PSV, respectively, on average) and E (by 37% and 35%) with unchanged breathing frequency and duty cycle. Both modalities significantly reduced esophageal (by 39% and 51%) and diaphragmatic (by 42% and 63%) pressure-time products, respectively. Ineffective efforts were observed with neither modes of assistance in any patient. CONCLUSIONS: In resting, awake patients in clinically stable condition with CVF caused by either COPD or RCWD, noninvasive application of PAV, set at the patient's comfort, was not superior to PSV either in increasing VT and E or in unloading the inspiratory muscles. We failed to find any difference in patient/ventilator interaction between ventilatory modes.

Aged↗

PubMed1994

Phonomyogram of the diaphragm during unilateral and bilateral phrenic nerve stimulation and changes with fatigue.

As previously demonstrated in humans, contracting skeletal muscles vibrate laterally and generate sound. The amplitude of this acoustic signal, called the phonomyogram (PMG), is related to muscle force production. As in limb muscles, the diaphragm might produce mechanical tissue vibrations and a PMG. We recorded diaphragm twitches during phrenic nerve stimulation in normal subjects at FRC. Diaphragmatic compound motor action potentials (CMAP) were recorded on each side of the chest by surface electrodes over the eighth intercostal space. Condenser microphones were fixed to the skin close to the electrodes, and esophageal and gastric balloons employed to measure transdiaphragmatic pressure (Pdi). For unilateral and bilateral supramaximal single shocks (0.1 ms), PMG onset latencies from either side (12.4 +/- 0.6 ms) were intermediate between those of CMAP (7.3 +/- 0.7 ms) and of Pdi (20.3 +/- 2.8 ms). By varying stimulation intensity, significant linear relationships were obtained between CMAP and PMG amplitudes on each side. A significant linear relationship was also found between PMG for each side and Pdi peak values. PMG and Pdi both decreased with fatigue of the diaphragm. We conclude that PMG in response to single phrenic nerve shocks is a noninvasive index of electromechanical coupling, recruitment, and transdiaphragmatic pressure generation by the diaphragm.

Action Potentials↗

PubMed1976

Left ventricular performance in coronary artery disease evaluated with systolic time intervals and echocardiography.

Simultaneous determinations of systolic time intervals (preejection period index [PEPI], left ventricular ejection time index [LVETI] and ratio of preejection period to left ventricular ejection time [PEP/LVET]) and echographic measures of left ventricular performance (percent change in minor axis diameter [%delta D], circumferential shortening rate [Vcf] and end-diastolic diameter [Dd]) were obtained in 25 normal subjects and 37 patients with previously documented transmural myocardial infarction. The group with previous infarction demonstrated significant (P less than 0.001) differences from the normal group in each of the noninvasive measures. PEP/LVET and %deltaD were the most sensitive measures of left ventricular dysfunction. Deviation from the normal range in these measures occurred, respectively, in 70 and 65 percent of patients without dyspnea or fatigability (20 patients) and 85 percent of those without angina pectoris (13 patients). Abnormalities in systolic time interval and echocardiographic measures were related to the severity of dyspnea and fatigability but not to that of angina. Neither the presence of phonocardiographically documented third or fourth sound gallops nor an abnormal cardiothoracic ratio by chest roentgenogram reliably detected patients with abnormal left ventricular performance. The range of abnormality in left ventricular performance did not differ between patients with prior anterior or diaphragmatic myocardial infarction. The frequency of abnormal performance was greatest among patients with combined sites of prior infarction. Among 26 patients studied by coronary arteriography, abnormal left ventricular performance as determined by values for PEP/LVET and %deltaD occurred in fewer than 30 percent of those with 70 percent or greater obstruction of one coronary artery and in more than 80 percent of those with two or three vessel involvement. There was a high correlation between systolic time intervals, %delta D and Vcf, the closest correlation occurring between PEP/LVET and %deltaD (r = -0.93). These data document the sensitivity of the noninvasive systolic time intervals and echographic measures and their superiority over current clinical bedside methods in evaluating left ventricular performance in patients with prior myocardial infarction.

Adult↗

PubMed2001

Cardiac and respiratory activity at arousal from sleep under controlled ventilation conditions.

Arousal from sleep is associated with elevated cardiac and respiratory activity. It is unclear whether this occurs because of homeostatic mechanisms or a reflex activation response associated with arousal. Cardiorespiratory activity was measured during spontaneous arousals from sleep in subjects breathing passively on a ventilator. Under such conditions, homeostatic mechanisms are eliminated. Ventilation, end-tidal PCO2, mask pressure, diaphragmatic electromyograph, heart rate, and blood pressure were measured in four normal subjects under two conditions: assisted ventilation and a normal ventilation control condition. In the control condition, there was a normal, sleep-related fall in ventilation and rise in end-tidal PCO2. Subsequently, at an arousal, there was an increase in respiratory and cardiac activity. In the ventilator condition, a vigorous cardiorespiratory response to a spontaneous arousal from sleep remained. These results indicate that sleep-related respiratory stimuli are not necessary for the occurrence of elevated cardiorespiratory activity at an arousal from sleep and are consistent with the hypothesis that such activity is at least in part due to a reflex activation response.

Adult↗

PubMed1995

[How urgent is an operation in enterothorax?].

The emergency treatment of the enterothorax is problematic due to weak lung functions and unstable hemodynamics, and because it does not influence the stage of maturity of the lungs. By delayed operation children with a critical starting position have a greater chance to survive, after their condition has been stabilised by intensive care treatment. During the stabilising period we managed to decrease the FiO2 level below 50% and to decrease the pCO2 level to 43 +/- 13 mm Hg in our patients (n = 10). Furthermore we succeeded to raise the O2 degree of saturation from 72 +/- 13 to 89 +/- 9%. The pH level went up from 7,238 +/- 0,181 to 7,394 +/- 0,060. If the condition of the patients worsens during the stabilising period--in our patients the stabilising period was between 12 and 24 hours--immediate operation is indicated. We have no experience so far in using ECMO in such situations.

Carbon Dioxide↗

PubMed1992

Monocyte inflammatory mediators impair in vitro hamster diaphragm contractility.

Sepsis has been shown to impair ventilatory muscle function. To determine whether this can be attributed to direct effects of inflammatory mediators on muscle fibers, we carried out in vitro studies on hamster costal diaphragm. Baseline measurements included supramaximal peak twitch (Pt) and tetanic tension (Po), twitch half relaxation time (1/2RT) and time-to-peak tension (TTP), and force frequency response (15 to 80 Hz). Fatigability was evaluated using 60-Hz stimulations at a duty cycle of 0.4 until tension fell to 50% of baseline. Preparations were then incubated in one of the following for 60 min: (1) Krebs solution (n = 5), (2) nonstimulated monocyte supernatant (n = 5), or (3) lipopolysaccharide-stimulated monocyte supernatant (n = 5). Baseline Pt, Po, 1/2RT, TTP, force frequency response, and fatigue profile were similar between groups. After incubation there was a significant fall in Pt (mean +/- SD, 538 +/- 65 to 288 +/- 13 g/cm2, p < 0.05) and Po (1,268 +/- 132 to 921 +/- 64 g/cm2, p < 0.05) in the LPS group, with no change in the other groups. There was no change in TTP; however, 1/2RT was lower in the LPS-stimulated group after incubation (p < 0.05). There was a rightward shift in the force frequency response for the LPS-stimulated group (p < 0.05). When normalizing for initial Po, there was no significant change in the time to fatigue for any of the three groups. This study demonstrated that monocyte secretory products impair diaphragmatic contractility in vitro by a direct effect on muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1981

Diaphragmatic EMG and transdiaphragmatic pressure measurements with a single catheter.

A single gastroesophageal catheter was used for simultaneous measurements of diaphragmatic electromyogram (EMGdi), esophageal, and gastric pressures in 10 normal volunteers. The catheter consisted of 2 polyethylene tubes, each with an outer diameter of 1.70 mm and an inner diameter of 1.19 mm, 2 platinum wire coils, and esophageal and gastric latex balloons. In all subjects studied, the increase in EMGdi, quantified as the average rate of rise of inspiratory moving average activity, and transdiaphragmatic pressure (Pdi) were linearly related to the increase in end-tidal PCO2 during CO2 rebreathing (range of r, 0.88 to 0.99 and 0.85 to 0.99, respectively). The relation between changes in EMGdi and that of Pdi, mean inspiratory flow, and occlusion pressure were also linear (range of r, 0.83-0.99, 0.73-0.99, and 0.84-0.99, respectively), indicating reliable recordings of EMGdi and Pdi during CO2 rebreathing in upright normal humans.

Carbon Dioxide↗

PubMed1991

Effects of PGF2 alpha on the EMG of costal and crural parts of the diaphragm of the newborn pig.

We investigated the effects of PGF2 alpha on the breathing patterns and electric activity of costal and crural parts of the diaphragm in 9 anesthetized newborn pigs. The change in diaphragmatic tension was evaluated as the change in transdiaphragmatic pressure. Because PGF2 alpha induces bronchoconstriction and an increase in respiratory resistances, the changes induced by prostaglandin were evaluated as differences between bronchoconstriction after PGF2 alpha and resistive load obtained by applying gradual occlusion to the inspiratory line of the breathing circuit. Our results show that PGF2 alpha decreased respiratory frequency with lengthening of expiratory time, while the resistive load increased both respiratory phases. The changes in breathing pattern were associated with different electrical activities of the diaphragm. While resistive load did not significantly change the EMG power spectrum, PGF2 alpha recruited new motor units. Furthermore, resistive load induced synchronization of the inspiratory time discharge of the costal and crural parts of the diaphragm, while after PGF2 alpha infusion there was an early inspiratory discharge of the crural part.

Animals↗

PubMed1992

Effect of negative pressure ventilation on ventilatory muscle endurance in patients with severe chronic obstructive pulmonary disease.

We studied five men with chronic obstructive pulmonary disease (COPD) (mean age, 65 +/- SEM 2 yr; FEV1, 0.68 +/- 0.08 L; and FEV1/FVC, 38 +/- 2%) to determine the relationship between ventilatory muscle endurance (VME) and ventilatory muscle rest (VMR) elicited by negative-pressure ventilation (NPV). VME was measured as the maximal sustainable ventilation (MSVC) that the subjects could maintain for 12 min. Prior to therapy, MSVC for the subjects was 25.0 +/- 3.6 L/min. During the therapy phase, subjects received 4 wk of daily "in-hospital-supervised" NPV therapy (4 h/day). While subjects received therapy, we quantified VMR by (1) the percentage of breaths that were "in synchrony" and by (2) the percentage of breaths showing "turn-off" of the diaphragmatic EMG signal (EMGdl). During the therapy sessions, 93 +/- 2% of breaths were in synchrony, whereas 66 +/- 11% showed EMGdl turn-off. During post-therapy testing, an increase in MSVC was noted in each of the subjects; the mean increase was 4.0 +/- 1.3 L/min (p less than 0.05), which represented an increase of 16 +/- 4% over pretherapy values. Increases in MSVC were highly correlated with both the percentage of in-synchrony breaths (r = 0.96, p less than 0.01) and the percentage of breaths showing EMGdl turn-off (r = 0.92, p less than 0.02). However, NPV therapy elicited no other improvements in either clinical or laboratory measurements. Moreover, patients exhibited marked dyspnea with initiation and termination of daily NPV therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗

PubMed1978

[Clinical significance of hiatal hernia].

A careful clinical investigation of 245 patients with hiatus hernia was performed. (History and physical examination, x-ray tests, oesophago-gastroscopy with biopsies, 3-point-manometry, rapid pull-through manometry with pentagastrintest). Classification of hiatus hernia was performed by x-ray test. (222 axial hiatus hernia, 14 mixed hiatus hernia, 9 paraoesophageal hiatus hernia) 3-point-manometry and rapid pull-through manometry with Pg-test were used to differentiate the function of the cardia. In spite of a strong selection in 84 out of 245 patients examined in our hospital, a sufficient cardia could be seen. 161 cases showed a gastro-oesophageal reflux which has been in accordance with a decompensated reflux disease in 97 patients. Solely in these 97 patients an operative correction of the gastro-oesophageal reflux seemed convenient. 84 patients showed a considerable variability of oesophageal disorders. In a final correlation between endoscopy, manometry and x-ray tests our opinion was confirmed that hiatus hernia must not lead inevitably to an insufficiency of the cardia. In the above investigations it could be shown that any therapeutic proceeding in the treatment of hiatus hernia first needs a careful analysis of the cardiac and oesophageal activity and second requires a careful indication for the surgical treatment of hiatus hernia.

Cardia↗

PubMed1995

Expiratory supraglottic obstruction during muscular relaxation.

Some reports have suggested occurrence of expiratory upper airway narrowing in patients with obstructive sleep apnea (OSA) during sleep and in awake humans during respiratory muscles relaxation. This is compatible with the hypothesis that upper airway muscles are activated during expiration. We studied five healthy volunteers and four patients with OSA in a tank respirator (Emerson; Cambridge, Mass). Supraglottic pressure (Psg) was measured with a catheter with the tip at the retroepiglottic level, tidal volume with an inductance plethysmograph and airflow with a pneumotachograph at the mouth. Diaphragmatic electromyogram was recorded with an esophageal bipolar electrode. Measurements were done at -30 cm H2O. Subjects were asked to breathe in phase with the respirator and then asked to breathe in phase with the respirator and then to relax their muscles. During muscular relaxation, there was supraglottic obstruction and flow limitation. This was observed during both inspiration and expiration. Upper airway obstruction was more severe in patients with OSA than in healthy subjects. In two healthy volunteers, fiberoptic bronchoscopy showed a wide-open oropharyngeal isthmus during active breathing that narrowed during muscular relaxation. This was true during both inspiration and expiration. We conclude that muscular relaxation is associated with upper airway narrowing and flow limitation occurring during both inspiration and expiration. We suggest that to preserve an open upper airway, airway muscles have to be activated during both inspiration and expiration.

Adult↗

PubMed2003

Subdiaphragmatic murine electrophysiological studies: sequential determination of ventricular refractoriness and arrhythmia induction.

Programmed electrical stimulation (PES) is a crucial aspect of the evaluation of the risk of arrhythmias in cardiac patients and provides a powerful tool for understanding the mechanisms of arrhythmia in experimental models. Whereas PES in the mouse is well characterized, the procedures allowing for follow-up studies in the same animal have not been developed. In this report, we describe a novel subdiaphragmatic approach that allows for repeat electrophysiological studies in the mouse. Under inhaled anesthesia, PES was performed in 36 wild-type mice via a stimulating electrode introduced through an epigastric incision and placed directly into the diaphragmatic surface of the heart. The procedure was repeated 7 days later. Ventricular effective refractory periods (VERP) did not change significantly between the initial and follow-up trials. Chronic treatment with amiodarone, however, was associated with a 70% prolongation in VERP from initial to follow-up studies (P < or = 0.001). In addition, PES of a genetically modified strain with sudden cardiac death, the connexin43 conditional knockout mouse consistently induced lethal polymorphic ventricular tachycardia. Thus sequential PES in mice is feasible with the use of a subdiaphragmatic approach, yields reproducible VERP values, and can be used to follow pharmacologically induced changes in VERP and identify mice at risk of lethal ventricular arrhythmias.

Action Potentials↗

PubMed1975

Respiratory function in esophageal hiatus hernia. I. Spirometry, gas distribution, and arterial blood gases.

As a part of a preoperative investigation, spirometry and blood gas tensions were studied in 64 subjects with X-ray-verified hiatus hernia (34 sliding, 22 mixed, and 8 of paraesophageal variety). According to the transverse diameter of the hernia. They were divided into 3 groups, small (2-5.9 cm), medium (6-9.9 cm), and large (10-17 cm) hernias. No correlation between the size of the hernia, reflux incidence, and spirometric findings could be demonstrated. A significant reduction of the arterial oxygen tension was found in small hernias and in vital capacity and maximal voluntary ventilation (MVV) in medium-sized hernias. Significant reduction in MVV was noted in the large hernia group. A common spirometric finding in all groups was a significant increase in residual volume and wash-out volume. The incidence of restrictive or obstructive pulmonary impairment was high in large (39%) and small (32%) hernias and relatively low in medium-sized hernias (8%). Roentgenological fibrosis was not found in any of the patients, while 4 showed emphysematous changes.

Adult↗

PubMed1977

Prospective study of controlled oxygen therapy. Poor prognosis of patients with asynchronous breathing.

Thirty-two patients were evaluated within 24 hours of admission for 36 episodes of acute respiratory failure (arterial oxygen pressure less than or equal to 50 mm Hg). Clinical data, spirometric determinations, blood gas analysis, and synchronization of chest (rib cage) and abdominal (diaphragmatic) breathing movements were studied. All patients were initially treated with controlled oxygen therapy. In 25 episodes the patients recovered without intubation (successes). In nine episodes the patients required intubation and assisted ventilation; two of these patients died. Two patients died without intubation. The 25 successful episodes were compared with the 11 requiring intubation or associated with death (failures). The breathing pattern proved to be the best single factor for predicting success or failure (77 percent correct prediction). The breathing pattern plus the arterial carbon dioxide tension on admission was the best two-factor guide (86 percent correct prediction). Patients with asynchronous breathing and severe hypercapnia are so unlikely to do well with a program of controlled oxygen therapy that preparations for intubation and assisted ventilation should be made on admission and such measures should be instituted at the first sign of deterioration.

Airway Obstruction↗

PubMed1976

Gastro-oesophageal reflux disease: correlation of subjective symptoms with 7 objective oesophageal function tests.

Seven tests which have been recommended for the diagnosis of gastro-esophageal reflux were applied in 24 healthy controls and in 48 patients with symptoms of reflux disease. The correlation coefficient of test results with the subjective symptoms of the patient decreased in the following order: 1) acid clearance from the distal esophagus (r = 0.558, p less than 0.001), 2) suction biopsy 5 cm above lower esophageal sphincter (LES) with evaluation of granulocytic infiltrates (r = 0.450, p less 0.001), 3) radiological demonstration of hiatal hernia (r = 0.435, p less than 0.001), 4) reflux provocation test (r = 359, p less than 0.01), 5) modified Bernstein test (r = 0.322, p less than 0.01), 6) acid relux test (r = 0.252, p less than 0.05), 7) resting pressure of LES (r = 0.246, p less than 0.05). Results of the Maudsley Personality Inventory were not correlated with subjective symptoms (r = 0.188, p greater than 0.1). By stepwise multiple regression analysis it was shown that optimal diagnosis of reflux is achieved by combination the following 4 procedures: 1) acid clearance, 2) modified Bernstein test, 3) suction biopsy, and 4) radiology.

Biopsy↗

PubMed2005

Aging of phrenic nerve conduction in the elderly.

OBJECTIVE: We elucidated the possible relationship between age and conduction parameters of phrenic nerve in subjects above the sixth decade, comparing with the data from middle-age controls. METHODS: Diaphragmatic action potentials (DAPs) were recorded on bilateral hemithoraces of 41 volunteers aged 60-101 years (old group) and 25 volunteers aged 35-55 years (middle-age group). Statistical analyses were performed to assess the effects of aging on latency, latency corrected by size (Lat/Dist), amplitude, and the right-left difference of these DAP parameters. RESULTS: In all 61 subjects, age showed a significant quadratic correlation with latency and with Lat/Dist, and a linear correlation with amplitude. The right-left differences ranged from 0.0 to 14.5% for latency and from 6.5 to 112.4% for amplitude in the elderly. CONCLUSIONS: The normal ranges of DAP parameters should be determined according to age. The left-right difference may be a useful reference in diagnosing unilateral phrenic nerve lesion. SIGNIFICANCE: The precise normal ranges of phrenic nerve conduction parameters presented will encourage investigations of neuropathies in subjects aged above 60.

Action Potentials↗

PubMed1983

[Evaluation of the functional modifications of the lower esophageal sphincter after use of the Angelchik prosthesis].

The manometric recording of Lower Esophageal Sphincter (LES) has been made in 8 patients who have undergone surgical apposition of Angelchik prosthesis for hiatal hernia. The patients underwent an esophageal manometric study in the preoperative period, one month and one year after the intervention. In the preoperative patients, the mean LES pressure was 10,3 +/- 0,5 mmHg and there was sphincterial incoordination to peristaltic waves after swallow. In one month postoperative patients the LESP was 20,1 +/- 1,0 mmHg (p less than 0,001), and one year after the LESP was 17,0 +/- 0,3 (p less than 0,001) with an ameliorated coordination of the LES activity in response to swallow. Therefore, during postoperative manometric controls the Authors identified a high pressure subdiaphragmatic zone unmodified by deglutitory acts which was not present in the preoperative investigation. Probably the presence of this zone would been explained as a consequence of mechanical action of the prosthesis and the postsurgical fibrino-reaction around the prosthesis. The Authors discussed the results obtained and their importance to Angelchik prosthesis employment for surgical correction of hiatal hernia.

Esophagogastric Junction↗