Vascular Effects of Noise
Francesco Tomei, M.D. Enrico Tomao, M.D. Tiziana Paola Baccolo, M.D. Bruno Papaleo, M.D. and Pasquale Alfi, M.D.
ROME, ITALY
Abstract The possible vascular effects of noise were studied. A study of the carotid vessels was made with Doppler ultrasonography in two groups of subjects exposed to various intensity of noise. The following data were studied: age, blood pressure, serum cholesterol, blood glucose, smoking habits, excess weight, electrocardiographic anomalies, family history of vascular disease, connection with duration of exposure and the type of noise and with audiometric deficits, and cerebrovascular modifications after postural changes and after a stress test. The control group comprised subjects not exposed to noise. The findings confirm that noise does play a role in causing vascular modifications that can be detected early by use of Doppler ultrasonography. This technique is predictive and could be useful in screening campaigns, following the method suggested here. Introduction In the past decade much attention has been paid to noise as a possible vascular risk factor. It &dquo;-’9 seems to influence vascular peripheral resistance heart rate~ 8-10 and blood pressure. Elec-
trocardiographic modifications, particularly in subjects with coronary disease&dquo; 18, 20-23 have also been reported. This study was designed to assess whether noise actually has vascular effects and to establish whether Doppler ultrasonography (usl4-JO can detect them. To clarify whether Doppler US is useful and predictive in screening campaigns, we used a simple and rapid method and determined whether a quantitative study was possible. Many studies have employed the Doppler method on asymptomatic patients,24.31,32 but the only trials covering a suffiFrom the Universita’
Degli Studi di Roma
"La
Sapienza," Facolta’ 904
di Medicina
e
Chirurgia
905 TABLE I
Velocitometric Values in
Noise-Exposed Subjects,
in Control
Group and of Other Authors
Velocity, SV=Systolic Velocity, IR=Index of Resistance, PPI=Perfusion Pressure Index, CDI=Carotid Distensibility Index, R=Right, L=Left, *p < 0.001, nc=number of cases, nv=norDV=Diastolic mal values.
number of people are those by Franceschi (300 subjects) 2’5 Gauch-Vedel (300 subjects),33 and Bourgeois et al (135 subjects).&dquo;’ Their aim was to find the average value and ranges in cm/sec. While recognizing that continuous-wave Doppler US does not give a true measure of speed, since the angle of incidence is known only approximately, we set out to assess whether this quantitative approach could nevertheless serve for screening working populations.
ciently large
Materials and Methods The study comprised two groups of male subjects with various exposure to noise (Table I) while doing the same type of work. The noise was variable and fluctuated widely, particularly at the beginning and end of each shift. Group A (80 subjects) was exposed to a continuous noise of 93 dBA Leq distributed over all frequencies with a few phases (two to four in a shift), each shorter than ten minutes, when the intensity rose 10 dBA or more, reaching 104-106
906
dBA. The noise of some main sources was harmonic and low frequency. Workers in group B were exposed to noise 10-15 % less intense than that of group A. Besides age, certain cardiovascular risk factors were taken into account: serum cholesterol, blood glucose, smoking habits, and family history of cardiovascular diseases. We evaluated the body mass index BMI (weight in kg/[height in meters]2), and we classified the subjects as: exact weight, full weight, obesity of middle degree, and obesity of high degree. The relationship with the duration (in hours) of exposure to noise and with audiometric deficits (in subjects at acoustic rest for at least sixteen hours), according to Merluzzi’s classification,35 was also investigated. In subjects at rest we recorded heart rate, blood pressure (BP) in clinostatic and orthostatic position (fifteen seconds after erect position), and electrocardiogram (ECG). ECG anomalies were classified as repolarization anomalies; myocardial damage; left-as fascicular block-and right axis deviation; anomalous atrioventricular and intraventricular conduction; right and left bundle branch block; atrial and ventricular sporadic or multiple arrhythmias; serious rhythm anomalies; right and left ventricular involvement; and myocardial infarction. Ultrasonography (US) was done using a continuous-wave Doppler unit with a 4 MHz probe, chart speed 25 mm/sec. The Doppler formula gives v=c*(~f f ]l[2f cos A]), where v velocity of blood particles, c velocity of sound in tissues (1540 m/s), f emission frequency, f reception frequency, A angle of incidence between the US ray and the blood vessel axis. The calibration impulse corresponds to a frequency difference (f -f,) of 1 kHz. When a 4 MHz probe is used at an angle A=45 ° the amplitute of the analog signal corresponds to a speed v (1540 m/s)*([lkHz]/2[4 MHz] cos 45) 27.22 cm/sec. In our study the 1 kHz calibration impulse corresponds to an analog width of 15 mm-. Therefore, in working with a 4 MHz probe, this corresponds to a speed of 27.22 cm/sec. Every mm equals 1.81 cm/sec. Comparisons are correct only if the sonogram was obtained by keeping the US ray at an angle of 45 ° to the axis of the blood vessel. Some reports give the results in terms of frequency. Though at first glance this appears more esoteric, it may in actual fact be more objective. The handheld bidirectional Doppler probe was positioned over the third lower segment of the right and left common carotid artery and angled at about 45 ° to the skin surface and was adjusted until an optimal flow signal was elicited. The workers were lying down resting, and at least fifteen minutes had elapsed since they had last smoked. =
=
=
=
=
=
=
907 Velocitometric Values in
*p
Francesco Tomei, M.D. Enrico Tomao, M.D. Tiziana Paola Baccolo, M.D. Bruno Papaleo, M.D. and Pasquale Alfi, M.D.
ROME, ITALY
Abstract The possible vascular effects of noise were studied. A study of the carotid vessels was made with Doppler ultrasonography in two groups of subjects exposed to various intensity of noise. The following data were studied: age, blood pressure, serum cholesterol, blood glucose, smoking habits, excess weight, electrocardiographic anomalies, family history of vascular disease, connection with duration of exposure and the type of noise and with audiometric deficits, and cerebrovascular modifications after postural changes and after a stress test. The control group comprised subjects not exposed to noise. The findings confirm that noise does play a role in causing vascular modifications that can be detected early by use of Doppler ultrasonography. This technique is predictive and could be useful in screening campaigns, following the method suggested here. Introduction In the past decade much attention has been paid to noise as a possible vascular risk factor. It &dquo;-’9 seems to influence vascular peripheral resistance heart rate~ 8-10 and blood pressure. Elec-
trocardiographic modifications, particularly in subjects with coronary disease&dquo; 18, 20-23 have also been reported. This study was designed to assess whether noise actually has vascular effects and to establish whether Doppler ultrasonography (usl4-JO can detect them. To clarify whether Doppler US is useful and predictive in screening campaigns, we used a simple and rapid method and determined whether a quantitative study was possible. Many studies have employed the Doppler method on asymptomatic patients,24.31,32 but the only trials covering a suffiFrom the Universita’
Degli Studi di Roma
"La
Sapienza," Facolta’ 904
di Medicina
e
Chirurgia
905 TABLE I
Velocitometric Values in
Noise-Exposed Subjects,
in Control
Group and of Other Authors
Velocity, SV=Systolic Velocity, IR=Index of Resistance, PPI=Perfusion Pressure Index, CDI=Carotid Distensibility Index, R=Right, L=Left, *p < 0.001, nc=number of cases, nv=norDV=Diastolic mal values.
number of people are those by Franceschi (300 subjects) 2’5 Gauch-Vedel (300 subjects),33 and Bourgeois et al (135 subjects).&dquo;’ Their aim was to find the average value and ranges in cm/sec. While recognizing that continuous-wave Doppler US does not give a true measure of speed, since the angle of incidence is known only approximately, we set out to assess whether this quantitative approach could nevertheless serve for screening working populations.
ciently large
Materials and Methods The study comprised two groups of male subjects with various exposure to noise (Table I) while doing the same type of work. The noise was variable and fluctuated widely, particularly at the beginning and end of each shift. Group A (80 subjects) was exposed to a continuous noise of 93 dBA Leq distributed over all frequencies with a few phases (two to four in a shift), each shorter than ten minutes, when the intensity rose 10 dBA or more, reaching 104-106
906
dBA. The noise of some main sources was harmonic and low frequency. Workers in group B were exposed to noise 10-15 % less intense than that of group A. Besides age, certain cardiovascular risk factors were taken into account: serum cholesterol, blood glucose, smoking habits, and family history of cardiovascular diseases. We evaluated the body mass index BMI (weight in kg/[height in meters]2), and we classified the subjects as: exact weight, full weight, obesity of middle degree, and obesity of high degree. The relationship with the duration (in hours) of exposure to noise and with audiometric deficits (in subjects at acoustic rest for at least sixteen hours), according to Merluzzi’s classification,35 was also investigated. In subjects at rest we recorded heart rate, blood pressure (BP) in clinostatic and orthostatic position (fifteen seconds after erect position), and electrocardiogram (ECG). ECG anomalies were classified as repolarization anomalies; myocardial damage; left-as fascicular block-and right axis deviation; anomalous atrioventricular and intraventricular conduction; right and left bundle branch block; atrial and ventricular sporadic or multiple arrhythmias; serious rhythm anomalies; right and left ventricular involvement; and myocardial infarction. Ultrasonography (US) was done using a continuous-wave Doppler unit with a 4 MHz probe, chart speed 25 mm/sec. The Doppler formula gives v=c*(~f f ]l[2f cos A]), where v velocity of blood particles, c velocity of sound in tissues (1540 m/s), f emission frequency, f reception frequency, A angle of incidence between the US ray and the blood vessel axis. The calibration impulse corresponds to a frequency difference (f -f,) of 1 kHz. When a 4 MHz probe is used at an angle A=45 ° the amplitute of the analog signal corresponds to a speed v (1540 m/s)*([lkHz]/2[4 MHz] cos 45) 27.22 cm/sec. In our study the 1 kHz calibration impulse corresponds to an analog width of 15 mm-. Therefore, in working with a 4 MHz probe, this corresponds to a speed of 27.22 cm/sec. Every mm equals 1.81 cm/sec. Comparisons are correct only if the sonogram was obtained by keeping the US ray at an angle of 45 ° to the axis of the blood vessel. Some reports give the results in terms of frequency. Though at first glance this appears more esoteric, it may in actual fact be more objective. The handheld bidirectional Doppler probe was positioned over the third lower segment of the right and left common carotid artery and angled at about 45 ° to the skin surface and was adjusted until an optimal flow signal was elicited. The workers were lying down resting, and at least fifteen minutes had elapsed since they had last smoked. =
=
=
=
=
=
=
907 Velocitometric Values in
*p
