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Biomedical subjects

M Estenne

Publications and source records attributed to M Estenne.

At least 37 records · Page 2Linked to original sources
PubMed1998

Respiratory mechanics and gas exchange during one-lung ventilation for thoracic surgery: the effects of end-inspiratory pause in stable COPD patients.

OBJECTIVE: To examine the effects of end-inspiratory pause (EIP) of different durations on pulmonary mechanics and gas exchange during one-lung ventilation (OLV) for thoracic surgery. DESIGN: A prospective clinical study. SETTING: A university hospital. PARTICIPANTS: Eleven patients undergoing elective pulmonary resection with pulmonary hyperinflation on their preoperative pulmonary function studies. INTERVENTIONS: Patients were anesthetized, paralyzed, and intubated with a double-lumen endotracheal tube. Their lungs were ventilated with a Siemens 900C ventilator (Siemens; Solna, Sweden), with constant inspiratory flow. Tidal volume, respiratory rate, and inspiratory time were kept constant during the study. MEASUREMENTS AND RESULTS: During one-lung ventilation in the lateral decubitus position, three levels of EIP (0%, 10%, and 30%) were applied to the dependent lung in random order. After 15 minutes on the given ventilatory pattern, end-inspiratory and end-expiratory occlusions of at least 5 seconds were performed to obtain respiratory mechanics data. Arterial blood gas samples were drawn to assess gas exchange. Altering the duration of end-inspiratory pause from 0% to 30% resulted in a significant increase in intrinsic positive end-expiratory pressure (PEEPi) from 4.1 cm H2O to 7.0 cm H2O. Arterial oxygenation was significantly decreased from 109.7 to 80.5 mmHg and there was a significant negative correlation between the value of partial pressure of arterial oxygen (PaO2) and PEEPi by altering the duration of end-inspiratory pause. From the preoperative pulmonary function studies, the value of functional residual capacity (FRC) (% predicted) showed a significant negative correlation with the PaO2 changes. Partial pressure of arterial carbon dioxide (PaCO2) was not altered significantly by increasing the duration of end-inspiratory pause. CONCLUSION: During the period of OLV in the lateral position of patients with preexisting pulmonary hyperinflation, the magnitude of PEEPi increased and oxygenation decreased significantly, whereas the efficacy of ventilation was not changed by the addition of an end-inspiratory pause to the ventilatory pattern. Because arterial oxygenation is affected by the presence of pulmonary hyperinflation, the method of ventilation should take into account the magnitude of preoperative pulmonary hyperinflation.

Aged↗
PubMed1998

Chest wall mechanics in sustained microgravity.

We assessed the effects of sustained weightlessness on chest wall mechanics in five astronauts who were studied before, during, and after the 10-day Spacelab D-2 mission (n = 3) and the 180-day Euromir-95 mission (n = 2). We measured flow and pressure at the mouth and rib cage and abdominal volumes during resting breathing and during a relaxation maneuver from midinspiratory capacity to functional residual capacity. Microgravity produced marked and consistent changes (Delta) in the contribution of the abdomen to tidal volume [DeltaVab/(DeltaVab + DeltaVrc), where Vab is abdominal volume and Vrc is rib cage volume], which increased from 30.7 +/- 3. 5 (SE)% at 1 G head-to-foot acceleration to 58.3 +/- 5.7% at 0 G head-to-foot acceleration (P < 0.005). Values of DeltaVab/(DeltaVab + DeltaVrc) did not change significantly during the 180 days of the Euromir mission, but in the two subjects DeltaVab/(DeltaVab + DeltaVrc) was greater on postflight day 1 than on subsequent postflight days or preflight. In the two subjects who produced satisfactory relaxation maneuvers, the slope of the Konno-Mead plot decreased in microgravity; this decrease was entirely accounted for by an increase in abdominal compliance because rib cage compliance did not change. These alterations are similar to those previously reported during short periods of weightlessness inside aircrafts flying parabolic trajectories. They are also qualitatively similar to those observed on going from upright to supine posture; however, in contrast to microgravity, such postural change reduces rib cage compliance.

Abdomen↗
PubMed1998

Effects of abdominal strapping on forced expiration in tetraplegic patients.

Patients with traumatic transection of the lower segments of the cervical cord contract the clavicular portion of the pectoralis major during forced expiration and cough, and the rise in intrathoracic pressure resulting from this contraction produces dynamic airway compression in many patients. Because the abdominal muscles are paralyzed, however, there is paradoxical expansion of the abdomen, which may reduce the rise in intrathoracic pressure and the degree of airway collapse. To evaluate the magnitude of this effect, we measured expiratory flow rate (Vexp) and esophageal pressure (Pes) during a series of forced expiratory vital capacity maneuvers and constructed isovolume-pressure flow (IVPF) curves before and after abdominal strapping in eight C5-8 tetraplegic subjects. Strapping produced small and inconsistent changes in maximal Vexp and Pes and resulted in the development of small flow plateaus in only four patients. In tetraplegic subjects, abdominal strapping thus has small effects on forced expiration and is unlikely, therefore, to improve the efficiency of cough.

Abdominal Muscles↗
PubMed1998

Neck and abdominal muscle activity in patients with severe thoracic scoliosis.

Patients with severe chronic obstructive pulmonary disease (COPD) do not use the sternocleidomastoid muscles when breathing at rest, but have a greater than normal neural drive to the rib-cage inspiratory muscles, the abdominal muscles, and the diaphragm. Yet the increased activation of the abdominal muscles and diaphragm in such patients has only limited mechanical effects, and this has led to the suggestion that the overall increase in neural drive is simply an automatic response of the respiratory system to a greater than resting stimulation. To test this hypothesis, we examined the pattern of respiratory-muscle activation in eight patients with severe thoracic scoliosis (Cobb angle between 100 degrees and 136 degrees). We recorded electromyograms of the sternocleidomastoid, scalene, rectus abdominis, external oblique, and transversus abdominis muscles; esophageal (Pes) and gastric (Pga) pressures; and the anteroposterior (AP) diameter of the abdomen during resting breathing in the seated posture. All patients had invariable phasic inspiratory activity in the scalenes; and five patients had invariable phasic expiratory activity in the transversus; intermittent expiratory activity in the transversus was also recorded in three patients. In contrast, only one patient had invariable phasic inspiratory activity in the sternocleidomastoid, and only one patient had invariable phasic expiratory activity in the external oblique. The decrease in abdominal AP diameter during expiration was commonly associated with a rise in Pga. These observations therefore indicate that the pattern of respiratory-muscle activation in patients with severe thoracic scoliosis is essentially similar to that seen in patients with severe COPD. This supports the concept that the order of recruitment of the respiratory muscles during breathing is an automatic response of the central controller.

Abdominal Muscles↗
PubMed1997

Lung rejection occurs in lung transplant recipients with blood chimerism.

BACKGROUND: It has been postulated that chimerism after transplantation might promote graft acceptance. In the present study, we prospectively assessed blood chimerism in 10 lung transplant recipients during the first posttransplant year and investigated whether chimerism was associated with an immunologically stable situation of the graft. METHODS: The recipients' peripheral blood mononuclear cells were obtained before transplantation and at various time points during the first postoperative year. Donor cells were detected using nested polymerase chain reaction amplification of a donor-specific HLA-DRB1 allele. Clinical graft acceptance was determined by the number of rejection episodes. RESULTS: The incidence of blood chimerism was high during the first 3 postoperative months and then decreased over time. All patients experienced at least one acute rejection episode, and three patients developed chronic rejection. CONCLUSION: We, thus, conclude that rejection of the lung allograft may occur in the presence of blood chimerism.

Adolescent↗
PubMed1997

Role of pulmonary function in the detection of allograft dysfunction after heart-lung transplantation.

BACKGROUND: Lung function is altered by infection and rejection in patients who undergo heart-lung transplantation. The sensitivity, specificity, and positive/negative predictive values (PPV and NPV) of lung function for the detection of allograft dysfunction in these patients were measured. METHODS: Thirty three patients who underwent heart-lung transplantation were followed for a mean period of 16.3 months. On 123 occasions functional measurements were obtained at the time a transbronchial biopsy specimen and/or bronchoalveolar lavage fluid was taken, which were used as gold standards. Optimal sensitivity (the value for which sensitivity equals specificity) was computed for each functional test from receiver-operator characteristic (ROC) curves. RESULTS: Acute rejection was present on 31 occasions and infection on 36 occasions; 56 samples were normal. Infection and rejection were accompanied by airflow obstruction, a rise in the slopes of the alveolar plateaus for nitrogen, hexafluoride sulphur and helium (SN2, SSF6, and SHe), and a decrease in the difference between SSF6 and SHe (delta S), total lung capacity (TLC), and lung transfer factor (TLCO). Optimal sensitivities for SHe, mid forced expiratory flow (FEF25-75), TLC, and forced expiratory volume in one second (FEV1) were 68%, 67%, 66%, and 60%, respectively; they were not different for infection and rejection and did not change over the study period. For infection and rejection together, PPV ranged from 72% to 88% and NPV from 27% to 52% according to the functional test and the postoperative period considered. CONCLUSIONS: Indices of ventilation distribution, FEF25-75, and TLC have the best optimal sensitivity for the diagnosis of infection and rejection after heart-lung transplantation. The high PPV of pulmonary function in detecting allograft dysfunction observed in this study suggests that a diagnostic procedure should be performed whenever one or more functional tests deteriorate; conversely, the low NPV indicates that a stable pulmonary function does not rule out allograft dysfunction.

Adolescent↗
PubMed1997

Three-dimensional reconstruction of human diaphragm with the use of spiral computed tomography.

We developed a technique of diaphragm imaging by using spiral computed tomography, and we studied four normal subjects who had been previously investigated with magnetic resonance imaging (A. P. Gauthier, S. Verbanck, M. Estenne, C. Segebarth, P. T. Macklem, and M. Paiva. J. Appl. Physiol. 76: 495-506, 1994). One acquisition of 15- to 25-s duration was performed at residual volume, functional residual capacity, functional residual capacity plus one-half inspiratory capacity, and total lung capacity with the subject holding his breath and relaxing. From these acquisitions, 20 coronal and 30 sagittal images were reconstructed at each lung volume; on each image, diaphragm contour in the zone of apposition and in the dome was digitized with the software Osiris, and the digitized silhouettes were used for three-dimensional reconstruction with Matlab. Values of length and surface area for the diaphragm, the dome, and the zone of apposition were very similar to those obtained with magnetic resonance imaging. We conclude that satisfactory three-dimensional reconstruction of the in vivo diaphragm may be obtained with spiral computed tomography, allowing accurate measurements of muscle length, surface area, and shape.

Adult↗
PubMed1997

Chest wall motion during tidal breathing.

We have used an automatic motion analyzer, the ELITE system, to study changes in chest wall configuration during resting breathing in five normal, seated subjects. Two television cameras were used to record the x-y-z displacements of 36 markers positioned circumferentially at the level of the third (S1) and fifth (S2) costal cartilage, corresponding to the lung-apposed rib cage; midway between the xyphoid process and the costal margin (S3), corresponding to the abdomen-apposed rib cage; and at the level of the umbilicus (S4). Recordings of different subsets of markers were made by submitting the subject to five successive rotations of 45-90 degrees. Each recording lasted 30 s, and three-dimensional displacements of markers were analyzed with the Matlab software. At spontaneous end expiration, sections S1-3 were elliptical but S4 was more circular. Tidal changes in chest wall dimensions were consistent among subjects. For S1-2, changes during inspiration occurred primarily in the cranial and ventral directions and averaged 3-5 mm; displacements in the lateral direction were smaller (1-2 mm). On the other hand, changes at the level of S4 occurred almost exclusively in the ventral direction. In addition, both compartments showed a ventral displacement of their dorsal aspect that was not accounted for by flexion of the spine. We conclude that, in normal subjects breathing at rest in the seated posture, displacements of the rib cage during inspiration are in the cranial, lateral outward, and ventral directions but that expansion of the abdomen is confined to the ventral direction.

Adult↗
PubMed1997

Effect of chronic hyperinflation on diaphragm length and surface area.

We have used three-dimensional reconstructions obtained with spiral computed tomography to measure total diaphragm length (Ldl) and surface area (Adl), the length (Ldo) and surface area (Ado) of the dome, and the length (Lap) and surface area (Aap) of the zone of apposition in 10 hyperinflated patients with severe chronic obstructive pulmonary disease, or COPD (FEV1 = 27% predicted: FRC = 225% predicted) and 10 normal subjects matched for age, sex, and height. Measures of Ldl, Adl, Lap, and Aap decreased linearly between FRC and TLC in the two groups, but Ldo and Ado did not change. On average, patients' Adl and Aap at FRC were reduced to 73% and 54% of normal values, whereas Ado was unaffected. When compared at similar absolute lung volumes, mean diaphragm dimensions were similar in patients with COPD and normal subjects, but individual values were very variable in both groups. This variability was partly accounted for by differences in body weight: i.e., the greater the weight, the longer the diaphragm. We conclude that (1) patients with COPD have marked reductions in Adl and Aap at FRC but have diaphragm dimensions similar to those of normal subjects when compared at similar absolute lung volumes, and (2) normal subjects and patients with COPD show substantial intersubject variability in diaphragm dimensions that is partly explained by differences in body weight.

Aged↗
PubMed1996

Sternomastoid muscle size and strength in patients with severe chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) imposes a major strain on the respiratory muscle pump, and it is conventionally thought that the inspiratory muscles of the neck adapt to this chronic overload by developing hypertrophy. Yet previous anthropometric studies have shown atrophy of the sternomastoid muscles. To solve this discrepancy, we have measured the cross-sectional area of these muscles by computed tomography. Ten stable patients with severe airflow obstruction (FEV1 = 0.76 +/- 0.12 L) and hyperinflation (FRC = 210 +/- 29% of predicted) and 10 control subjects matched for age, sex, and height were studied. The sternomastoid cross-sectional area in the patients averaged (mean +/- SD) 4.29 +/- 1.48 cm2, and that in the control subjects was 3.96 +/- 0.82 cm2. This small difference could be entirely accounted for by hyperinflation, and it was not statistically significant. Sternomastoid muscle torque in patients was also similar to that in the control subjects. In patients with severe COPD, therefore, the sternomastoid muscles are essentially normal. As a corollary, their frequent prominence on clinical examination is only apparent.

Aged↗
PubMed1996

Rib cage dimensions in hyperinflated patients with severe chronic obstructive pulmonary disease.

Using computed tomography we assessed rib cage dimensions at the levels of Th4, Th6, Th8, and Th10 in seven supine patients with COPD who were severely obstructed (FEV1, 25 +/- 7% of predicted) and hyperinflated (FRC, 234 +/- 34% of predicted) and seven matched normal control subjects. The midsagittal anteroposterior (AP) diameter, the maximal AP diameter of the right and left hemithorax, and the maximal transverse (T) diameter were measured on scans obtained at relaxed TLC, FRC, and RV. At each volume, AP diameters were invariably 2 to 3 cm greater in patients with COPD than in normal subjects, but no significant differences in T diameters were found. When compared at a given absolute lung volume, T diameters at all thoracic levels and AP diameters at Th4-6 were smaller in patients with COPD than in normal subjects; in contrast, at Th8-10, AP diameters were similar in the two groups. We conclude that the marked hyperinflation of patients with severe COPD produces complex changes in rib cage dimensions: (1) there is an increase in AP but not in T diameters such that the rib cage adopts a more circular shape; (2) at a given absolute lung volume, AP diameters are smaller in patients with COPD than in normal subjects in the upper but not in the lower portion of the rib cage. These differences in rib cage dimensions may have implications regarding respiratory muscle length and function in patients with COPD.

Adult↗
PubMed1996

[Functional respiratory physiology and physiopathology of lung transplant patients].

Lung transplantation results in dramatic improvement in pulmonary function which allows the patients to resume a normal lifestyle. When the lung allograft is free of infection and rejection, lung volumes and gas exchange are within normal limits after heart-lung and double lung transplantation, both at rest and during exercise. After single lung transplantation, lung volumes remain below predicted values and some patients show mild oxygen desaturation with exercise. Infection, acute rejection, and chronic rejection (bronchiolitis obliterans) produce an obstructive ventilatory defect. In addition, there is a bronchial hyperreactivity to cholinergic stimulation; this hyperreactivity might be related to airway denervation and upregulation of muscarinic receptors or might be triggered by the bronchial inflammation induced by rejection. Control of breathing is normal at rest, during exercise, in response to CO2 rebreathing, and during sleep. This indicates that pulmonary afferents play a negligible role in the control of breathing in adult humans. Most transplanted patients show a significant reduction in maximum oxygen consumption and have an early anaerobiosis during exercise; this response may be accounted for, at least in part, by a persistent state of physical deconditioning, and by an inadequate adaptation of cardiac output in heart-lung transplant recipients.

Adult↗
PubMed1995

Effects of increased +Gz on chest wall mechanics in humans.

We studied the effects of head-to-foot acceleration (+Gz) on chest wall mechanics in five normal subjects seated in a human centrifuge. Results were compared with those previously obtained in the same subjects in microgravity during parabolic flights. In all subjects, end-expiratory abdominal pressure (Pga) and volume (Vab) increased with Gz. On average, end-expiratory Pga increased from 7.4 +/- 1.7 cmH2O at + 1 Gz to 14.9 +/- 2.8 cmH2O at + 3 Gz and end-expiratory Vab increased by 0.32 +/- 0.06 liter between + 1 and + 3 Gz. On the other hand, the abdominal contribution to tidal volume (Vab/VT) and abdominal compliance decreased from 34.7 +/- 5.9% and 52 +/- 6 ml/cmH2O at + 1 Gz to 29.3 +/- 5.1% and 26 +/- 4 ml/cmH2O at + 3 Gz, respectively. Changes in end-expiratory Pga were linear between 0 and + 3 Gz, but changes in end-expiratory Vab, Vab/VT, and abdominal compliance were greater in microgravity than in hypergravity. In contrast to weightlessness, which did not alter minute ventilation and tidal changes in Pga and transdiaphragmatic pressure, these variables increased with increasing Gz. These results indicate that, although changes in Gz have a linear effect on abdominal transmural pressure, hypergravity and weightlessness do not have symmetrical effects on chest wall mechanics.

Abdomen↗
PubMed1995

Persistent hyperinflation after heart-lung transplantation for cystic fibrosis.

We have measured static lung volumes after heart-lung transplantation (HLT) in seven patients with cystic fibrosis (CF) (Group 1), three patients with chronic hyperinflation due to diseases other than CF (Group 2), and six patients with primary pulmonary hypertension (PPH) (Group 3). Total lung capacity was within normal limits at 1 yr after surgery in all patients. Similarly, FRC was within the normal range in Groups 2 and 3. On the other hand, patients with CF showed a persistent increase in FRC; at 1 yr after HLT, FRC averaged 4.13 +/- 0.52 L compared with a predicted value of 3.20 +/- 0.23 L (p < 0.01). The postoperative static pressure-volume curve of the lung in the patients with CF was superimposed on the predicted one, suggesting that the increased FRC originated in the chest wall. Additional studies with computerized tomographic scans demonstrated that the rib cage anteroposterior diameter at FRC averaged 12.1 +/- 1.6 cm in patients with CF, 9.5 +/- 1.2 cm in patients with PPH, and 9.4 +/- 0.7 cm in a group of healthy subjects matched with the patients with CF (p < 0.01). We conclude that after HLT, patients with CF show persistent hyperinflation due to rib cage expansion along the anteroposterior dimension. This shape change may represent a structural adaptation that occurs in response to chronic pulmonary hyperinflation acquired during rib cage growth.

Adolescent↗
PubMed1995

Regulation of breathholding time and sensation after heart-lung transplantation.

To assess whether pulmonary vagal afferents affect the duration of breathholding, the associated respiratory distress and their dependence on lung volume, we studied seven heart-lung transplant (HLT) patients with chronic pulmonary denervation and seven matched control subjects. Voluntary breathholds were performed at 20% and 80% vital capacity (VC) after rebreathing a 7% CO2-93% O2 gas mixture. Time to breakpoint, oxygen saturation, and end-tidal PCO2 were measured. All subjects were questioned on their sensations during breathholding; in addition, quantitative assessment of the sensations was obtained using a visual analog scale (VAS) in the seven control subjects and four HLT subjects. Breathholding time was comparable in both groups at each lung volume but was invariably shorter (p < 0.0005) at 20% VC (mean +/- SD; HLT versus control subjects: 68 +/- 29 versus 79 +/- 29 s) than at 80% VC (corresponding values: 92 +/- 35 versus 103 +/- 30 s). Similar results were obtained after anesthesia of intact tracheal and upper airway receptors in five HLT subjects. Six subjects from each group spontaneously reported air hunger and found it easier to perform breathholding at 80% than at 20% VC. The VAS ratings generally showed a maximum score at breakpoint, which implies that the distress increased more rapidly at low than at high lung volume. We conclude that in the absence of vagal afferent innervation from the lungs: (1) the air hunger form of dyspnea is maintained; (2) the duration of breathholding is not substantially modified; and (3) breathholding time and sensations still vary as a function of lung volume.

Adult↗