Prevalence and clinical associations of wheezes and crackles in the general population: the Tromsø study.

BACKGROUND: Wheezes and crackles are well-known signs of lung diseases, but can also be heard in apparently healthy adults. However, their prevalence in a general population has been sparsely described. The objective of this study was to determine the prevalence of wheezes and crackles in a large general adult population and explore associations with self-reported disease, smoking status and lung function. METHODS: We recorded lung sounds in 4033 individuals 40 years or older and collected information on self-reported disease. Pulse oximetry and spirometry were carried out. We estimated age-standardized prevalence of wheezes and crackles and associations between wheezes and crackles and variables of interest were analyzed with univariable and multivariable logistic regressions. RESULTS: Twenty-eight percent of individuals had wheezes or crackles. The age-standardized prevalence of wheezes was 18.6% in women and 15.3% in men, and of crackles, 10.8 and 9.4%, respectively. Wheezes were mostly found during expiration and crackles during inspiration. Significant predictors of expiratory wheezes in multivariable analyses were age (10 years increase - OR 1.18, 95%CI 1.09-1.30), female gender (1.45, 1.2-1.8), self-reported asthma (1.36, 1.00-1.83), and current smoking (1.70, 1.28-2.23). The most important predictors of inspiratory crackles were age (1.76, 1.57-1.99), current smoking, (1.94, 1.40-2.69), mMRC ≥2 (1.79, 1.18-2.65), SpO2 (0.88, 0.81-0.96), and FEV1 Z-score (0.86, 0.77-0.95). CONCLUSIONS: Nearly over a quarter of adults present adventitious lung sounds on auscultation. Age was the most important predictor of adventitious sounds, particularly crackles. The adventitious sounds were also associated with self-reported disease, current smoking and measures of lung function. The presence of findings in two or more auscultation sites was associated with a higher risk of decreased lung function than solitary findings.

Tracheal sounds in upper airway obstruction.

A boy with subglottic narrowing secondary to laryngotracheitis presented with noisy breathing. Acoustic measurements of tracheal sounds at standardized air flows correlated well with the clinical course and with spirometric assessments. This indicates the potential value of respiratory sound characterization in patients with upper airway obstruction.

Subjective assessment vs computer analysis of wheezing in asthma.

To determine if wheezing is a reproducible clinical sign, we presented recorded breath sounds from asthmatic patients to four groups of health professionals: pediatric residents, nurses, pediatricians, and physiotherapists. Their subjective assessments included scores of wheezing severity and estimates of wheezing duration. All participants repeated the test at least two weeks later. Results were compared to computer aided spectral analysis of the recorded breath sounds. Interobserver and intraobserver variability fell somewhat between chance and total agreement. In contrast, the computer analysis allowed an objective and reproducible characterization of wheezing in asthma.

Nomenclature used by health care professionals to describe breath sounds in asthma.

We studied the spontaneous, uninstructed description by 40 health care professionals of breath sounds in asthmatic patients, and their use of lung sound terminology following current recommendations. Tape play-back auscultation of recorded tracheal and lung sounds was performed by ten observers in each group of residents, nurses, staff physicians and physiotherapists. They repeated the test after two weeks to three months. Individual descriptions were compared to computer-aided characterization of the breath sound recordings. We found significant differences in the preferred terms for description of adventitious lung sounds between the groups of health care professionals. There was considerable intraobserver variability, with less agreement when suggestions for a more complex characterization were followed. Our observations indicate the importance of teaching a standardized nomenclature for lung sounds to health care professionals, using only terms which are clearly informative of pulmonary disease.

Arterial oxygen desaturation following salbutamol inhalation in acute asthma.

The practicality and accuracy of a new ear oximeter was evaluated. The SaO2 measured with this instrument correlated significantly with simultaneous SaO2 measurements with another ear oximeter in 12 children (age three months to 20 years) with chronic pulmonary or cardiac diseases (r = 0.93, p less than 0.001), and also correlated significantly (r = 0.96, p less than 0.001) with calculated SaO2 based on blood gas measurements of blood from the left side of the heart obtained during cardiac catheterization. The SaO2 was then measured continuously and readings were taken before and five, 15, and 30 minutes after salbutamol inhalation by face mask in 18 children. Following treatment, mean PEFR increased significantly, and mean SaO2 was significantly lower than preinhalation values at five and 15 minutes postinhalation. At 30 minutes, SaO2 had returned to control values. In nine of 18 subjects, SaO2 fell greater than or equal to 5 percent. This response was not predictable on the basis of different parameters (treatment, heart rate, PEFR). The findings suggest that supplemental O2 may be required during the first 30 minutes posttreatment.

Obstructive sleep apnea leading to increased intracranial pressure in a patient with hydrocephalus and syringomyelia.

Rises in intracranial pressure from normal baseline values up to 50 cm H2O occurred shortly after the onset of obstructive sleep apnea in a patient with myelomeningocele, hydrocephalus, Arnold-Chiari malformation, and syringomyelia. Tonsillar hypertrophy caused the airway obstruction during sleep, because the obstructive sleep apnea and also the periodic elevation of intracranial pressure disappeared after tonsillectomy. Only one report from Japan has previously described three patients with elevated cerebrospinal fluid pressures during obstructive sleep apnea. It is conceivable that episodic airway obstruction and concurrent intracranial hypertension may have contributed to the development of syringomyelia in our patient.

Posture-dependent change of tracheal sounds at standardized flows in patients with obstructive sleep apnea.

BACKGROUND: The ability of awake subjects with obstructive sleep apnea (OSA) to dilate their pharynx during inspiration may be defective. Airflow through a relatively more narrow pharyngeal passage should lead to increased flow turbulence and hence to louder respiratory sounds. We therefore studied the increase of tracheal sound intensity (TSI) in the supine position as an indicator of abnormal pharyngeal dynamics in patients with documented OSA. SUBJECTS AND METHODS: Sound was recorded with a contact sensor at the suprasternal notch in 7 patients with OSA (age, 52 +/- 8 years; body mass index, 29.0 +/- 3; apnea-hypopnea index, 58 +/- 17; means +/- SD), and in 8 control subjects, including obese subjects and snorers (age, 39 +/- 8 years; body mass index, 28.6 +/- 4). Subjects breathed through a pneumotachograph and aimed at target flows of 1.5 to 2 L/s, first sitting, then supine. Flow and sound signals were digitized at a 10-KHz rate. Fourier analysis was applied to sounds within the target flow range and average power spectra were obtained. Spectral power was calculated for frequency bands 0.2 to 1, 1 to 2, and 2 to 3 KHz. RESULTS: In the supine position, OSA patients had a significantly greater increase of inspiratory TSI than control subjects: 7.5 +/- 1.2 dB vs 1.7 +/- 3.4 dB (p < 0.001); 6.6 +/- 1.7 dB vs 1.3 +/- 3.9 dB (p < 0.005); and 12.2 +/- 3.2 dB vs 5.6 +/- 3.1 dB (p < 0.001) at low, medium, and high frequencies, respectively. Expiratory TSI also increased in supine subjects, but the change was significantly greater in OSA subjects only at high frequencies. These findings confirm our earlier observations that did not include obese subjects or snorers among control subjects. SUMMARY: Measuring posture effects on tracheal sounds is noninvasive and requires little time and effort. The greater increase of inspiratory TSI in supine OSA patients compared to subjects without OSA suggests a potential value for daytime acoustic screening.

Acoustic imaging of the human chest.

STUDY OBJECTIVES: A novel method for acoustic imaging of the human respiratory system is proposed and evaluated. DESIGN: The proposed imaging system uses simultaneous multisensor recordings of thoracic sounds from the chest wall, and digital, computer-based postprocessing. Computer simulations and recordings from a life-size gelatin model of the human thorax are used to evaluate the system in vitro. Spatial representations of thoracic sounds from 8-microphone and 16-microphone recordings from five subjects (four healthy male adults and one child with lung consolidation) are used to evaluate the system in vivo. RESULTS: Results of the in vitro studies show that sound sources can be imaged to within 2 cm, and that the proposed algorithm is reasonably robust with respect to changes in the assumed sound speed within the imaged volume. The images from recordings from the healthy volunteers show distinct patterns for inspiratory breath sounds, expiratory breath sounds, and heart sounds that are consistent with the assumed origin of the respective sounds. Specifically, the images support the concept that inspiratory sounds are produced predominantly in the periphery of the lung while expiratory sounds are generated more centrally. Acoustic images from the subject with lung consolidation differ substantially from the images of the healthy subjects, and localize the abnormality. CONCLUSIONS: Acoustic imaging offers new perspectives to explore the acoustic properties of the respiratory system and thereby reveal structural and functional properties for diagnostic purposes.

Digital respirosonography. New images of lung sounds.

We used tape recordings from normal subjects and from patients with lung disease to generate spectrographic images of respiratory sounds on a personal computer. These digital respirosonograms presented timing and frequency content of lung sounds, with the sound intensities displayed on a color scale. Respiratory sounds during inspiration and expiration could be recognized by their association with concurrent respiration curves. Contributions of low-frequency cardiac sounds were visually identified by their relationship to simultaneously recorded ECGs. Typical characteristics of normal and adventitious lung sounds were documented and displayed both in the time and the frequency domain. Digital respirosonography provides an easy way to assess lung sound amplitudes, frequencies and timing over several breaths.

Auditory detection of simulated crackles in breath sounds.

BACKGROUND: Computerized analysis of breath sounds has relied on human auditory perception as the reference standard for identifying crackles. In this study, we tested the human audibility of crackles by superimposing artificial clicks on recorded breath sounds and having physicians listen to the recordings to see if they could identify the crackles. OBJECTIVES: To establish the audibility of simulated crackles introduced in breath sounds of different intensity, to study the effects of crackle characteristics on their audibility, and to investigate crackle detection within and between observers. METHODS: Fine, medium, and coarse crackles with large and small amplitude were synthesized by computer software. Waveform parameters were based on published characteristics of lung sound crackles. The amplitude for small crackles was defined as just above the threshold of audibility for simulated crackles inserted in sound recorded during breath hold. Simulated crackles were then superimposed on breath sounds recorded at 0 L/s (breath hold), 1 L/s, and 2 L/s airflow. Five physicians listened during playback on two separate occasions to determine if crackles could be heard and to calculate the interobserver and intraobserver variations. RESULTS: Failed detection of crackles was significantly more common in the following conditions: (1) background breath sounds had higher intensity (2 L/s airflow) compared to lower intensity (1 L/s), (2) crackle type was coarse or medium compared to fine, and (3) crackle amplitude was small compared to large. Both intraobserver and interobserver agreements were high (kappa > 0.6). RELEVANCE: The validation of automated techniques for crackle detection in lung sound analysis should not rely on auscultation as the only reference. Detection of crackles is facilitated when patients take slow, deep breaths that generate little breath sounds.

Measurement of respiratory acoustical signals. Comparison of sensors.

We assessed the performance of three air-coupled and four contact sensors under standardized conditions of lung sound recording. Recordings were obtained from three of the investigators at the best site on the posterior lower chest as determined by auscultation. Lung sounds were band-pass filtered between 100 and 2,000 Hz and sampled simultaneously with calibrated airflow at a rate of 10 kHz. Fourier techniques were used for power spectral analysis. Average spectra for inspiratory sounds at flows of 2 +/- 0.5 L/s were referenced against background noise at zero flow. Air-coupled and contact sensors had comparable maximum signal-to-noise ratios and gave similar values for most spectral parameters. Unexpectedly, less sensitivity (lower signal-to-noise ratio) at high frequencies was observed in the air-coupled devices. Sensor performance needs to be characterized in studies of lung sounds. We suggest that lung sound spectra should be averaged at known airflows over several breaths and that all measurements should be reported relative to sounds recorded at zero flow.

Measurement of respiratory acoustic signals. Effect of microphone air cavity width, shape, and venting.

STUDY OBJECTIVE: We have previously investigated the effects of microphone type and coupler air chamber depth on lung sound characteristics. We now report the results of experiments exploring the effects of air chamber width, shape, and venting on lung sounds. DESIGN: We used a single electret microphone with a variety of plastic couplers. The couplers were identical except for the diameter and shape of the air chamber. We used cylindrical chambers of 5, 10, and 15 mm in diameter at the skin and conical chambers of 8, 10, and 15 mm in diameter. We compared the inspiratory lung sound spectra obtained using each of the couplers. We also examined the tendency of various needle vents to transmit ambient noise into the microphone chamber. SETTING: Anechoic chamber. MEASUREMENTS AND RESULTS: The shape and diameter had little important effect on the lung sound spectrum below 500 Hz. From approximately 500 to 1,500 Hz, the 5-mm diameter couplers showed slightly less sensitivity than the 10- and 15-mm diameter couplers. All conical couplers provided approximately 5 to 10 decibel more sensitivity than the cylindrical couplers. All vents allowed some ambient noise to enter the chamber but the amount was trivial using the narrowest, longest vent. CONCLUSIONS: These data suggest that the optimal electret microphone coupler chamber for lung sound acquisition should be conical in shape, between 10 and 15 mm in diameter at the skin, and either not vented or vented with a tube no wider than 23-g or shorter than 20 mm.

Measurement of respiratory acoustic signals. Effect of microphone air cavity depth.

The use of electret microphones to measure lung sounds is widespread because of their small size, high fidelity, and low cost. Typically, an air cavity is placed between the skin surface and the microphone to convert the chest wall vibrations into a measurable sound pressure. The importance of air cavity depth on this transduction process was investigated in this study. An acoustic model of chest wall--air cavity--microphone interface was developed and the predicted effects of depth were compared with measurements performed using an artificial chest wall and lung sounds from a healthy subject. Model predictions are in general agreement with both in vitro and in situ measurements and indicate that the overall high-frequency response of the transduction diminishes with increasing cavity depth. This finding suggests that smaller cavity depths are more appropriate for detection of lung sounds over a wide band width and stresses the importance of coupler size on microphone measurements.

Endogenous opiates and response to exercise in asthmatic children and adolescents.

Whether endorphins secreted during stressful exercise may play a role in the physiologic response of asthmatics was investigated. Thirteen asthmatic subjects were studied: seven (mean age 16 years +/- 2.8 SEM) had perennial asthma and exercise-induced bronchospasm (EIB), and six (mean age 18 years +/- 2) had mild seasonal asthma without EIB. Each subject performed two matched progressive exercise challenges on consecutive days. Baseline lung function was measured before each challenge and was measured again after exercise at regular intervals for 30 minutes. One minute before exercise each subject received intravenously either i.v. naloxone (0.04 mg/kg), an opiate receptor blocker, or saline, in a double-blind crossover fashion. Heart rate, oxygen consumption, minute ventilation, tidal volume, and arterial oxygen saturation were recorded throughout the tests. During the two challenges these parameters were not significantly different for all 13 patients. The mean percentage reduction in FEV1 after exercise for the seven subjects with EIB was slightly but not significantly less with naloxone (25% +/- 7 SEM) than with placebo (32% +/- 7) during the first 10 minutes after exercise. Naloxone had no obvious effect on EIB or the other parameters measured in association with strenuous exercise in asthmatic patients.

Relationship between response to inhaled salbutamol and methacholine bronchial provocation in children with suspected asthma.

Fifty children (27 females, 23 males) ages 6-15 years who were referred for evaluation of suspected asthma had baseline FEV1 and FEF25-75 of greater than or equal to 80% and FEF50 greater than or equal to 70% of predicted values. All had these tests repeated on the same day, after inhaling salbutamol. On a subsequent day PC-20 (methacholine) was determined as an index of bronchial hyperreactivity (BH). Fourteen age-matched healthy children (6 females, 8 males) were studied in a similar manner. There was no significant relationship between the PC20 and the change in FEF25-75 or FEF50 following salbutamol. There was a negative correlation between the initial FEV1 (% predicted) and the percent change in FEV1 following salbutamol (P less than 0.01). An increase in FEV1 of greater than 6% occurred in 7/12 (58.3%) patients with PC20 less than or equal to 0.25 mg/mL (Group I); in 7/24 (29.2%) patients with PC20 = 0.26-2.0 mg/mL (Group II); in only 1/14 (7.1%) patients with PC20 greater than 2.1 mg/mL (Group III) and in none of those asymptomatic (control) children with PC20 greater than 8.0 mg/mL (Group IV). All subjects who had a change in FEV1 greater than 6% after salbutamol had a PC20 less than 8 mg/mL and this test detected the majority of patients with severe BH. However, although the sensitivity of the test was 100%, the predictive value was only 36%. We conclude that in the presence of a normal baseline FEV1 a change of greater than 6% following salbutamol inhalation is indicative of bronchial hyperreactivity.

Acoustic vs. spirometric assessment of bronchial responsiveness to methacholine in children.

To study wheezing as an indicator of bronchial responsiveness during methacholine challenge (MC) in children, we used computer analysis of respiratory sounds and compared wheeze measurements to routine spirometry. MC was performed in 30 symptomatic subjects (sympt), age 11 +/- 3.1 years (mean +/- SD), with suspected asthma and in 12 controls (contr), age 10 +/- 3.4 years. Respiratory rate (RR), spirometry, arterial oxygen saturation (SaO2), and cough were registered until the concentration provoking a > or = 20% fall in forced expiratory flow in 1 second (FEV1;PC20), or the end point (8 mg/mL) was reached. For 1 min after each inhalation, sounds over the trachea and posterior right lower lobe were recorded together with calibrated airflow. Computer analysis of respiratory sounds was used for objective wheeze quantification. Wheezing was measured as its duration relative to inspiration (Tw/Ti) and expiration (Tw/Te). Seventeen of the sympt group developed wheezing (sympt/W) with > or = 5% Tw/Ti or > or = 5% Tw/Te. Thirteen of the sympt did not wheeze (sympt/no W). Three contr developed wheeze (contr/W) while 9 did not (contr/no W). In sympt/W, RR increased from 20 +/- 6.2 per min at baseline to 25 +/- 9.2 (P < 0.05) at the MC concentration provoking wheeze (PCw), and SaO2 decreased from 97.4 +/- 1.2% to 95.3 +/- 2.4 (P < 0.05). In contr/W, RR did not change, but SaO2 decreased from 97.3 +/- 1.5% to 95.7% +/- 1.2% (P < 0.05). Wheezing occurred at both recording sites and was as common during inspiration as during expiration.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of terfenadine on the response to exercise and cold air in asthma.

To assess the role of histamine as a mediator in the response to exercise and isocapnic hyperventilation of cold air (IHCA) in asthma, we studied nine asthmatic subjects, age 13 to 25 years. All had exercise induced asthma (EIA) and positive responses to IHCA. Baseline lung function was measured before standardized challenges with histamine, exercise and IHCA. On separate days, these tests were repeated 3 h after a single oral dose of 120 mg terfenadine (TF). Histamine responsiveness decreased significantly, with a provocative concentration, producing a greater than or equal to 20% fall in FEV1 (PC20), of 1.1 +/- 0.8 mg/ml (mean +/- SEM) before and 12.0 +/- 4.9 mg/ml after the antihistamine. EIA was significantly less after TF, with 53 +/- 5% mean maximal falls in FEV1 from baseline before, and 29 +/- 9% after treatment (P less than 0.01, paired t-test). In contrast, the effect of TF on the response to IHCA was insignificant, with mean maximal falls of 45 +/- 7% in FEV1 before, and 41 +/- 7% after treatment. There was a correlation between PC20 and lowest FEV1 (% predicted) for EIA (r = 0.56, P less than 0.05), but not for IHCA (r = 0.34, NS). This study indicates a role of histamine as a mediator in EIA but not in IHCA, supporting different mechanisms for both stimuli.

Chest surface mapping of lung sounds during methacholine challenge.

Wheeze as an indicator of airway obstruction during bronchoprovocation lacks sensitivity. We therefore studied whether induced airway narrowing is revealed by changes in normal (vesicular) lung sounds. Fifteen subjects with asthma and nine healthy controls, aged 8-16 years, performed a standardized methacholine challenge. Respiratory sounds were recorded with eight contact sensors, placed posteriorly over the right and left superior and basal lower lobes, and anteriorly over both upper lobes, the right middle lobe, and the trachea. Average spectra of normal inspiratory and expiratory sounds, excluding wheeze, were characterized in 12 asthmatics and 9 controls at flows of 1 +/- 0.2 L/sec. Airway narrowing was accompanied by significant changes in lung sounds, but not in tracheal sounds. Lung sounds showed a decrease in power at low frequencies during inspiration and an increase in power at high frequencies during expiration. These changes already occurred at a decrease in forced expiratory volume in 1 sec of less than 10% from baseline and were fully reversed after inhalation of salbutamol. Thus, lung sounds were sensitive to changes in airway caliber, but were not specific indicators of bronchial hyperresponsiveness.

Home measurement of oxygen saturation during sleep in patients with cystic fibrosis.

Feasibility and reproducibility of home measurement of arterial oxygen saturation (SaO2) were evaluated in 14 clinically stable patients with cystic fibrosis (CF). Changes in SaO2 during sleep were compared to the clinical status and pulmonary function while awake to identify predictors of nocturnal oxyhemoglobin desaturation. Each patient was assessed by clinical score, spirometry, and arterial blood gas analysis within 72 hours of the overnight study. Eight patients were studied on more than one occasion to assess dependence of SaO2 on position and reproducibility of overnight studies. A pulse oximeter stored up to 8 hours of nocturnal SaO2 measurements in its memory. Off-line analysis of trend data provided the proportion of sleep with SaO2 less than 90% and less than 85%. We found that patients with daytime PaO2 less than 60 mm Hg spent greater than 80% of their sleep with SaO2 less than 90%, while those with PaO2 greater than 70 mm Hg spent less than 20% of the night with SaO2 less than 90%. Patients with daytime PaO2 of 67-70 mm Hg were desaturated to less than 90%, from 0 to 98% of the night. No consistent body position dependence of daytime SaO2 was found. Home measurement of SaO2 during sleep was reproducible, with a difference on two repeat occasions of 4% +/- 2 (mean +/- SEM) for %time with SaO2 less than 90% and 3% +/- 2 for %time with SaO2 less than 85%. The severity of hemoglobin desaturation during sleep could not be reliably predicted from clinical scores or awake pulmonary function.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a Soft Boston Orthosis on pulmonary mechanics in severe cerebral palsy.

Spinal braces such as the Soft Boston Orthosis (SBO) help stabilize scoliosis and improve sitting, positioning, and head control in individuals with cerebral palsy. However, their impact on pulmonary mechanics in this population has not been studied. We examined the effect of a Soft Boston Orthosis on the pulmonary mechanics and gas exchange in 12 children and young adults (5-23 years of age) with severe cerebral palsy. Pulmonary resistance, compliance, tidal volume, minute ventilation, work of breathing, oxygen saturation, and end-tidal CO2 tension were measured with the subjects seated both with and without the orthosis and in the supine position without the orthosis. There were no significant differences in the measured parameters when comparing subjects with and without their orthoses in the sitting or in the supine position. As would be expected in individuals with severe cerebral palsy, pulmonary resistance was increased (7.33 cm H2O/L/s) and compliance was decreased (0.12 L/cm H2O) compared to reported normal values. Work of breathing was greatest in the sitting position without the orthosis (1.2 dynes/cm), suggesting that the improved positioning achieved with the orthosis may decrease the work of breathing. We conclude that the application of a Soft Boston Orthosis does not impact negatively on pulmonary mechanics and gas exchange in young people with severe cerebral palsy.