Alain Boussuges

Diaphragmatic Motion Studied by M-Mode Ultrasonography: Methods, Reproducibility, and Normal Values

BACKGROUND Although diaphragmatic motion is readily studied by ultrasonography, the procedure remains poorly codified. The aim of this prospective study was to determine the reference values for diaphragmatic motion as recorded by M-mode ultrasonography. METHODS Two hundred ten healthy adult subjects (150 men, 60 women) were investigated. Both sides of the posterior diaphragm were identified, and M-mode was used to display the movement of the anatomical structures. Examinations were performed during quiet breathing, voluntary sniffing, and deep breathing. Diaphragmatic excursions were measured from the M-mode sonographic images. In addition, the reproducibility (inter- and intra-observer) was assessed. RESULTS Right and left diaphragmatic motions were successfully assessed during quiet breathing in all subjects. During voluntary sniffing, the measurement was always possible on the right side, and in 208 of 210 volunteers, on the left side. During deep breathing, an obscuration of the diaphragm by the descending lung was noted in subjects with marked diaphragmatic excursion. Consequently, right diaphragmatic excursion could be measured in 195 of 210 subjects, and left diaphragmatic excursion in only 45 subjects. Finally, normal values of both diaphragmatic excursions were determined. Since the excursions were larger in men than in women, the gender should be taken into account. The lower limit values were close to 0.9 cm for women and 1 cm for men during quiet breathing, 1.6 cm for women and 1.8 cm for men during voluntary sniffing, and 3.7 cm for women and 4.7 cm for men during deep breathing. CONCLUSIONS We demonstrated that M-mode ultrasonography is a reproducible method for assessing hemidiaphragmatic movement.

Original ResearchUltrasonographyDiaphragmatic Motion Studied by M-Mode Ultrasonography: Methods, Reproducibility, and Normal Values

BACKGROUND Although diaphragmatic motion is readily studied by ultrasonography, the procedure remains poorly codified. The aim of this prospective study was to determine the reference values for diaphragmatic motion as recorded by M-mode ultrasonography. METHODS Two hundred ten healthy adult subjects (150 men, 60 women) were investigated. Both sides of the posterior diaphragm were identified, and M-mode was used to display the movement of the anatomical structures. Examinations were performed during quiet breathing, voluntary sniffing, and deep breathing. Diaphragmatic excursions were measured from the M-mode sonographic images. In addition, the reproducibility (inter- and intra-observer) was assessed. RESULTS Right and left diaphragmatic motions were successfully assessed during quiet breathing in all subjects. During voluntary sniffing, the measurement was always possible on the right side, and in 208 of 210 volunteers, on the left side. During deep breathing, an obscuration of the diaphragm by the descending lung was noted in subjects with marked diaphragmatic excursion. Consequently, right diaphragmatic excursion could be measured in 195 of 210 subjects, and left diaphragmatic excursion in only 45 subjects. Finally, normal values of both diaphragmatic excursions were determined. Since the excursions were larger in men than in women, the gender should be taken into account. The lower limit values were close to 0.9 cm for women and 1 cm for men during quiet breathing, 1.6 cm for women and 1.8 cm for men during voluntary sniffing, and 3.7 cm for women and 4.7 cm for men during deep breathing. CONCLUSIONS We demonstrated that M-mode ultrasonography is a reproducible method for assessing hemidiaphragmatic movement.

Evaluation of left ventricular filling pressure by transthoracic Doppler echocardiography in the intensive care unit.

Objective To determine whether Doppler transmitral and pulmonary venous flow pattern is related to left ventricular filling pressures in critically ill patients. Design Prospective clinical investigation. Setting Medical intensive care unit of a university hospital. Patients Fifty-four mechanically ventilated patients (age, 63 ± 16 yrs) were investigated via transthoracic echocardiography and Doppler. Main diagnoses were pneumonia (31%), acute exacerbation of chronic obstructive pulmonary disease (24%), congestive heart failure (11%), and poisoning (11%). Interventions Doppler examinations were performed simultaneously with measurements of pulmonary artery occlusion pressure via a right heart catheter. Measurements and Main Results Pulmonary artery occlusion pressure correlated with transmitral peak E-wave velocity (r = .46) and E/A ratio (r = .55). Pulmonary artery occlusion pressure inversely correlated with deceleration time of the transmitral E-wave (r = −.52), pulmonary venous peak S-wave velocity (r = −.37), and systolic fraction of the pulmonary forward flow (r = −.56). An E/A ratio >2 predicted a pulmonary artery occlusion pressure >18 mm Hg with a positive predictive value of 100%. A duration of pulmonary venous A-wave reversal flow exceeding the duration of the transmitral A-wave forward flow predicted a pulmonary artery occlusion pressure >15 mm Hg with a positive predictive value of 83%. A systolic fraction of the pulmonary venous forward flow <0.4 predicted a pulmonary artery occlusion pressure >12 mm Hg with a positive predictive value of 100%. Conclusion Transmitral and pulmonary venous flow patterns measured by transthoracic Doppler echocardiography can be used to estimate the left ventricular filling pressure in critically ill patients.

Characteristics of Arterial Stiffness in Very Low Birth Weight Premature Infants

Premature birth is a factor of increased blood pressure in adulthood. Little is known about the physiologic characteristics of the arterial bed in neonates. The aim of this study was to characterize in vivo the arterial compliance in neonates and its maturation profile in very low birth weight (VLBW) premature infants. A group of stable, VLBW premature infants was compared with a control group of near term neonates. The abdominal aortic wall distensibility coefficient (DC) and whole-body arterial compliance (WBAC) were determined using specifically designed noninvasive methods, based on ultrasonic measurements in combination with synchronous, beat-to-beat recording of aortic pulse pressure (PP). On the fifth day of life, WBAC and the CD were lower in VLBW premature infants than in controls. Furthermore, WBAC and the DC remained unchanged in VLBW premature infants 7 wk after birth. In conclusion, VLBW premature infants are characterized as early as the fifth day of life by high arterial stiffness, which persists when they reach their theoretical term. It can be speculated that early alteration of arterial elastic properties may pave the way for long-term elevation of arterial pressure in VLBW premature infants.

Respective Roles of Preterm Birth and Fetal Growth Restriction in Blood Pressure and Arterial Stiffness in Adolescence

PURPOSE Recent studies show that low birth weight infants are at a risk of increased arterial blood pressure (BP) in adulthood. This study aimed to distinguish the influence of low birth weight either as a result of fetal growth restriction or preterm birth on arterial properties in adolescents. METHODS The effect of low birth weight on BP and arterial stiffness was examined among 90 adolescents aged 14 years who were either born at term with an appropriate birth weight for gestational age (controls, n = 41); born preterm with an appropriate birth weight for gestational age (n = 25); or born at term and small for gestational age (SGA) (n = 24). The pulse wave velocity between the carotid and radial arteries was measured to assess arterial stiffness. RESULTS As compared with control subjects, adolescents born with low birth weight as a result of preterm birth were found to have increased systolic BP and carotid-radial pulse wave velocity (117 ± 11 mm Hg vs. 123 ± 11 mm Hg, p = .04 and 7.0 ± .9 m/s vs. 7.7 ± 1.0 m/s, p = .01, respectively), whereas those who were born at term and SGA exhibited values similar to the controls (114 ± 15 mm Hg and 6.8 ± .9 m/s). CONCLUSION Preterm birth, rather than being SGA at term, increases BP and arterial stiffness in adolescents.

Use of heliox in patients with severe exacerbation of chronic obstructive pulmonary disease.

Objective To assess whether patients with chronic obstructive pulmonary disease treated with heliox have a better prognosis than those treated with standard therapy. Design Retrospective analysis over 18 months. Setting Academic emergency department. Patients Eighty-one patients admitted with exacerbation of chronic obstructive pulmonary disease and respiratory acidosis. Interventions Use of helium-oxygen mixture as an adjunctive therapy. Measurements and Main Results The following data were collected: age, gender, medical history, vital signs, arterial blood gas at admission, emergency room treatment, requirement for intubation, admission in intensive care unit, length of stay, and evolution. Patients were classified into two groups according to whether heliox was used as a therapeutic agent (heliox group) or not (standard group). Chi-square test and Student’s t-test were used for statistical analysis (significant at p < .05). In both groups, the following data were similar: age, gender, medical history, vital signs, initial arterial blood gas, and emergency room treatment. Significant decreases in intubation, and mortality rate were identified in the heliox group. Significant decreases in intensive care unit stay and in-hospital stay were observed for survivors in the heliox group. Conclusion Use of heliox seems to improve prognosis in patients with severe acute exacerbation of chronic obstructive pulmonary disease. Prospective randomized studies are needed to confirm these results.

Haemodynamic changes induced by submaximal exercise before a dive and its consequences on bubble formation

Objectives: To evaluate the effects of a submaximal exercise performed 2 h before a simulated dive on bubble formation and to observe the haemodynamic changes and their influence on bubble formation. Participants and methods: 16 trained divers were compressed in a hyperbaric chamber to 400 kPa for 30 min and decompressed at a rate of 100 kPa/min with a 9 min stop at 130 kPa (French Navy MN90 procedure). Each diver performed two dives 3 days apart, one without exercise and one with exercise before the dive. All participants performed a 40 min constant-load submaximal and calibrated exercise, which consisted of outdoor running 2 h before the dive. Circulating bubbles were detected with a precordial Doppler at 30, 60 and 90 min after surfacing. Haemodynamic changes were evaluated with Doppler echocardiography. Results: A single bout of strenuous exercise 2 h before a simulated dive significantly reduced circulating bubbles. Post-exercise hypotension (PEH) was observed after exercise with reductions in diastolic and mean blood pressure (DBP and MBP), but total peripheral resistance was unchanged. Stroke volume was reduced, whereas cardiac output was unchanged. Simulated diving caused a similar reduction in cardiac output independent of pre-dive exercise, suggesting that pre-dive exercise only changed DBP and MBP caused by reduced stroke volume. Conclusion: A single bout of strenuous exercise 2 h before a dive significantly reduced the number of bubbles in the right heart of divers and protected them from decompression sickness. Declining stroke volume and moderate dehydration induced by a pre-dive exercise might influence inert gas load and bubble formation.

Haemodynamic effects of hyperbaric hyperoxia in healthy volunteers: an echocardiographic and Doppler study

In the present study, we observed the haemodynamic changes, using echocardiography and Doppler, in ten healthy volunteers during 6 h of compression in a hyperbaric chamber with a protocol designed to reproduce the conditions as near as possible to a real dive. Ambient pressure varied from 1.6 to 3 atm (1 atm=101.325 kPa) and partial pressure of inspired O2 from 1.2 to 2.8 atm. Subjects performed periods of exercise with breathing through a closed-circuit self-contained underwater breathing apparatus (SCUBA). Subjects did not eat or drink during the study. Examinations were performed after 15 min and 5 h. After 15 min, stroke volume (SV), left atrial (LA) diameter and left ventricular (LV) end-diastolic diameter (LVEDD) decreased. Heart rate (HR) and cardiac output (CO) did not vary, but indices of the LV systolic performance decreased by 10% and the LV meridional wall stress increased by 17%. After 5 h, although weight decreased, the serum protein concentration increased. Compared with values obtained after 15 min, SV and CO decreased, but LV systolic performance, LA diameter, LVEDD and LV meridional wall stress remained unchanged. Compared with the reference values obtained at sea level, total arterial compliance decreased, HR remained unchanged and CO decreased. In conclusion, hyperbaric hyperoxia results in significant haemodynamic changes. Initially, hyperoxia and the SCUBA system are responsible for reducing LV preload, increasing LV afterload and decreasing LV systolic performance, although CO did not change. Prolonged exposure resulted in a further decrease in LV preload, because of dehydration, and in a further increase in LV afterload, due to systemic vasoconstriction, with the consequence of decreasing CO.

Peripheral arterial disease: an underestimated aetiology of exercise intolerance in chronic obstructive pulmonary disease patients:

Objective To assess the prevalence of peripheral arterial disease and its implications for exercise limitation in chronic obstructive pulmonary disease (COPD) patients. Method One hundred and fifty-one moderate-to-severe COPD patients (forced expiratory volume in 1s: 37 ± 6 SD% predicted) and 73 healthy age-matched control individuals (divided into 31 smokers and 42 nonsmokers) participated in this study. All COPD patients were either exsmokers or current smokers and their tobacco-smoking history was similar to that of healthy smokers. To evaluate the existence of arterial disease, lower limb perfusion pressure impairment was assessed using the ankle brachial index, whereas arterial stiffness was assessed by the pulse wave velocity (PWV). The definition of peripheral arterial disease required an ankle brachial index value of 0.90 or less, whereas the PWV increment was considered to be a direct witness of arterial stiffness increase. A 6-min walk test was performed to assess physical exercise capacity. Results Prevalence of peripheral arterial disease was higher in COPD patients than in healthy participants (81 ±3 SD; 49 ± 5 SD and 9 ± 2 SD%, respectively, in COPD, healthy smokers and nonsmokers). PWV mean values were significantly higher in COPD patients compared with healthy smokers and nonsmokers (10.3 ±2.1 SD m/s; 9.2 ±1.3 SD m/s and 8.7 ± 2.2 SD m/s, respectively). The distance covered during the 6-min-walk test was associated positively with the degree of peripheral arterial disease (r = 0.78; P = 0.05) and negatively with the PWV values (r = –0.74; P = 0.05). Not only tobacco-smoking history but also COPD severity was shown to influence these associations. Conclusion The effect of peripheral arterial disease on exercise intolerance in COPD seems to be considerable. Therefore, COPD patients participating in a pulmonary rehabilitation programme should profit from a systematic search for arterial disease. Arterial dysfunction has to be taken into account in the multidisciplinary treatment of these patients.

Haemodynamic changes after prolonged water immersion

Abstract Thermoneutral water immersion increases cardiac preload and changes the neuroendocrine settings of blood volume regulation. The resulting marked diuresis may lead to significant haemodynamic changes after the end of a prolonged water immersion. Ten volunteers underwent 6 h of complete thermoneutral water immersion. Changes in cardiovascular status were assessed 1 h and 16 h after water immersion. Haemodynamic changes were assessed by Doppler echocardiography. Arterial wall distensibility was estimated by pulse wave velocity analysis. One hour after water immersion, mean weight loss was 1.78 kg and urine volume amounted to 1.5 litres. Echocardiographic measurements evidenced a significant decrease in dimensions of the left cardiac chambers and inferior vena cava. The decreased cardiac preload was paralleled by a lower stroke volume and cardiac output. A peripheral vasoconstriction associated with a relative decrease in the lower limb blood flow was evidenced by an increase in carotid-pedal pulse wave velocity and by a decrease in ankle brachial index. Sixteen hours after water immersion, cardiac preload and cardiac output remained below baseline values and peripheral vascular tone was still higher than at baseline. Marked haemodynamic changes had not returned to baseline 16 h after water immersion. There is a need to design fluid-replacement protocols to improve this recovery.