Asynchronous breathing movements in patients with chronic obstructive pulmonary disease

Physical signs in patients with chronic obstructive pulmonary disease

We reviewed the various physical signs of chronic obstructive pulmonary disease, their pathogenesis, and clinical importance. We searched PubMed, EMBASE, and the CINAHL from inception to March 2018. We used the following search terms: chronic obstructive pulmonary disease, physical examination, purse-lip breathing, breath sound intensity, forced expiratory time, abdominal paradox, Hoover's sign, barrel-shaped chest, accessory muscle use, etc. All types of studies were chosen. Globally, history taking and clinical examination of the patients is on the wane. One reason can be a significant development in the field of medical technology, resulting in overreliance on sophisticated diagnostic machines, investigative procedures, and medical tests as first-line modalities of patient's management. In resource-constrained countries, detailed history taking and physical examination should be emphasized as one of the important modalities in patient's diagnosis and management. Declining bedside skills and clinical aptitude among the physician is indeed a concern nowadays. Physical diagnosis of chronic obstructive pulmonary disease (COPD) is the quickest and reliable modalities that can lead to early diagnosis and management of COPD patients. Bedside elicitation of physical signs should always be the starting point for any diagnosis and therapeutic approach.

The effect of body position on pulmonary function, chest wall motion, and discomfort in young healthy participants

OBJECTIVE

The purpose of this study was to investigate the effect of different recumbent positions on pulmonary function, chest wall motion, and feelings of discomfort in young nonobese healthy volunteers.

METHODS

Twenty healthy volunteers (age, 28.0±1.4 years; height, 167.5±10.1 cm; weight, 62.3±10.2 kg) were studied in the sitting position and in the following 6 recumbent positions: supine, left retroversion at a 45° tilt, left anteversion at a 45° tilt, right retroversion at a 45° tilt, right anteversion at a 45° tilt, and prone. After 5 minutes of a selected position, pulmonary functions, including vital capacity (VC), forced expiratory volume in 1 second, maximal inspiratory and expiratory mouth pressures (MIP and MEP, respectively), and breathing pattern components at the chest wall were assessed. Discomfort was assessed using a modified Borg scale.

RESULTS

When participants changed position from sitting to each of the 6 recumbent positions, forced expiratory volume in 1 second values decreased significantly (P < .05). None of the participants showed changes in the MIP or MEP in any of the 6 recumbent positions. Rib cage motion was restricted in all recumbent positions except supine, left anteversion at a 45° tilt, and prone. In all 6 recumbent positions, discomfort was experienced during the pulmonary tests. However, in the left retroversion at a 45° tilt position, no discomfort was experienced during the MIP and MEP assessments.

CONCLUSION

In young, nonobese, healthy volunteers, recumbent positions caused diminished pulmonary functions and induced feelings of discomfort.

Influence of posture on the ventilatory pattern and the thoraco-abdominal kinematics of patients with chronic obstructive pulmonary disease (COPD)

OBJECTIVE

Evaluate the influence of posture on ventilatory pattern, compartmental distribution of volume of chest wall and thoraco-abdominal kinematics of patients with severe chronic obstructive pulmonary disease (COPD).

DESIGN

Cross-sectional study.

METHODS

Twelve, male patients with severe COPD (Forced Expiratory Volume in the first second (FEV1) = 24.35 ± 4.52%, Forced Vital Capacity% (FVC%) = 60 ± 13.39% and relationship FEV1/FVC = 53.42 ± 14.47). The distribution of the volume of the ribcage [pulmonary rib cage (Rcp), abdominal ribcage (Rca) and abdomen (Ab)] during quiet breathing in a sitting position without back support (SWB), sitting with backrest (SB) and supine position (SUP) was determined using an opto-electronic plethysmograph.

RESULTS

The following differences were observed: a greater tidal volume in the SWB position when compared to the SB position (p = 0.01); greater expiratory time in the SUP position in relation to the SWB (p = 0.03) and SB (p = 0.01); and increased abdominal contribution to the tidal volume in the SUP position in relation to the SWB (p < 0.01) and SB (p < 0.001). No difference was found in the thoraco-abdominal synchrony among the positions.

CONCLUSION

Sitting position without back support enhances the activation of respiratory muscles by increasing the tidal volume and supine position seems to favor lung deflation by increasing the expiratory time. It seems appropriate to adopt these positions to optimize the ventilation/perfusion relationship and physiotherapeutic intervention in different clinical conditions.

Respiratory dysfunction in unsedated dogs with golden retriever muscular dystrophy

Golden retriever muscular dystrophy (GRMD) is a well-established model of Duchenne muscular dystrophy. The value of this model would be greatly enhanced with practical tools to monitor progression of respiratory dysfunction during treatment trials. Arterial blood gas analysis, tidal breathing spirometry, and respiratory inductance plethysmography (RIP) were performed to determine if quantifiable abnormalities could be identified in unsedated, untrained, GRMD dogs. Results from 11 dogs with a mild phenotype of GRMD and 11 age-matched carriers were compared. Arterial blood gas analysis was successfully performed in all dogs, spirometry in 21 of 22 (95%) dogs, and RIP in 18 of 20 (90%) dogs. Partial pressure of carbon dioxide and bicarbonate concentration were higher in GRMD dogs. Tidal breathing peak expiratory flows were markedly higher in GRMD dogs. Abnormal abdominal motion was present in 7 of 10 (70%) GRMD dogs. Each technique provided objective, quantifiable measures that will be useful for monitoring respiratory function in GRMD dogs during clinical trials while avoiding the influence of sedation on results. Increased expiratory flows and the pattern of abdominal breathing are novel findings, not reported in people with Duchenne muscular dystrophy, and might be a consequence of hyperinflation.

Nonlinear model for estimating respiratory volume based on thoracoabdominal breathing movements

BACKGROUND AND OBJECTIVE

Respiratory inductive plethysmography is a non-invasive technique for measuring respiratory function. However, there are challenges associated with using linear methods for calibration of respiratory inductive plethysmography. In this study, we developed two nonlinear models, artificial neural network and adaptive neuro-fuzzy inference system, to estimate respiratory volume based on thoracoabdominal movements, and compared these models with routine linear approaches, including qualitative diagnostic calibration and multiple linear regression.

METHODS

Recordings of spirometry volume and respiratory inductive plethysmography were obtained for 10 normal subjects and 10 asthmatic patients, during asynchronous breathing for 7 min. The first 5 min of recording were used to develop the models; the remaining data were used for subsequent validation of the results.

RESULTS

The results from the nonlinear models fitted the spirometry volume curve significantly better than those obtained by linear methods, particularly during asynchrony (P < 0.05). On a breath-by-breath analysis, estimates of tidal volume, total cycle time and sigh values using the artificial neural network model were accurate by comparison with qualitative diagnostic calibration. In contrast to the artificial neural network model, there was a significant correlation between values for thoracoabdominal asynchrony and increased error of qualitative diagnostic calibration (P < 0.05).

CONCLUSIONS

These results indicate that the nonlinear methods can be adapted to closely simulate variable conditions and used to study the patterns of volume changes during normal and asynchronous breathing.

Lower-limb endurance training program influences thoracoabdominal motion of patients with COPD?

INTRODUCTION: Thoracoabdominal-TA asynchrony is an important sign of Chronic Obstructive Pulmonary Disease (COPD). Studies investigating the influence of endurance training on TA asynchrony have not been found. OBJECTIVE: To analyze lower-limb endurance training effects on TA asynchrony in patients with COPD. MATERIALS AND METHODS: Two patients with severe COPD were evaluated in a single-subject design AB (A-baseline for six weeks, B-training on cycle ergometer with intensity of 70% of baseline peak load, for 12 weeks) with repeated measures of variables: phase inspiratory relation (PhRIB), phase expiratory relation (PhREB) and phase angle (PhAng). These variables were assessed by respiratory inductive plethysmography during incremental exercise tests on a cycle ergometer (same load and peak load of each test). Statistical methods included visual analysis, two-standard deviation band test and split middle line test, considering significant p < 0.05. It was considered the results for variables with agreement of at least two analyses. Data are presented as mean ± SD for phases A and B. RESULTS: During phase B, Patient 1 presented significant decrease of PhRIB (22.7 ± 3.4 x 17.0 ± 4.9) and PhAng (16.5 ± 5.1 x 13.2 ± 2.1) for same load and PhREB (16.8 ± 3.1 x 13.3 ± 3.1) and PhAng (23.4 ± 1.7 x 20.1 ± 2.3) at peak load. Patient 2 showed significant decrease of PhRIB for same load and (14.4 ± 3.8 x 13.9 ± 3.9) at peak load (19.1 ± 2.5 x 15.7 ± 2.7). CONCLUSIONS: These results suggest that lower-limb endurance training reduced TA asynchrony in patients with severe COPD. The findings may be related, according to the literature, to the lower ventilatory demand and greater exercise capacity of patients with COPD undergoing endurance training.

The effect of posture on asynchronous chest wall movement in COPD

Chronic obstructive pulmonary disease (COPD) patients often show asynchronous movement of the lower rib cage during spontaneous quiet breathing and exercise. We speculated that varying body position from seated to supine would influence rib cage asynchrony by changing the configuration of the respiratory muscles. Twenty-three severe COPD patients (forced expiratory volume in 1 s = 32.5 ± 7.0% predicted) and 12 healthy age-matched controls were studied. Measurements of the phase shift between upper and lower rib cage and between upper rib cage and abdomen were performed with opto-electronic plethysmography during quiet breathing in the seated and supine position. Changes in diaphragm zone of apposition were measured by ultrasounds. Control subjects showed no compartmental asynchronous movement, whether seated or supine. In 13 COPD patients, rib cage asynchrony was noticed in the seated posture. This asynchrony disappeared in the supine posture. In COPD, upper rib cage and abdomen were synchronous when seated, but a strong asynchrony was found in supine. The relationships between changes in diaphragm zone of apposition and volume variations of chest wall compartments supported these findings. Rib cage paradox was noticed in approximately one-half of the COPD patients while seated, but was not related to impaired diaphragm motion. In the supine posture, the rib cage paradox disappeared, suggesting that, in this posture, diaphragm mechanics improves. In conclusion, changing body position induces important differences in the chest wall behavior in COPD patients.

A telemedicine instrument for Internet-based home monitoring of thoracoabdominal motion in patients with respiratory diseases

Changes in thoracoabdominal motion are highly prevalent in patients with chronic respiratory diseases. Home care services that use telemedicine techniques and Internet-based monitoring have the potential to improve the management of these patients. However, there is no detailed description in the literature of a system for Internet-based monitoring of patients with disturbed thoracoabdominal motion. The purpose of this work was to describe the development of a new telemedicine instrument for Internet-based home monitoring of thoracoabdominal movement. The instrument directly measures changes in the thorax and abdomen circumferences and transfers data through a transmission control protocol∕Internet protocol connection. After the design details are described, the accuracy of the electronic and software processing units of the instrument is evaluated by using electronic signals simulating normal subjects and individuals with thoracoabdominal motion disorders. The results obtained during in vivo studies on normal subjects simulating thoracoabdominal motion disorders showed that this new system is able to detect a reduction in abdominal movement that is associated with abnormal thoracic breathing (p < 0.0001) and the reduction in thoracic movement during abnormal abdominal breathing (p < 0.005). Simulated asynchrony in thoracoabdominal motion was also adequately detected by the system (p < 0.0001). The experimental results obtained for patients with respiratory diseases were in close agreement with the expected values, providing evidence that this instrument can be a useful tool for the evaluation of thoracoabdominal motion. The Internet transmission tests showed that the acquisition and analysis of the thoracoabdominal motion signals can be performed remotely. The user can also receive medical recommendations. The proposed system can be used in a spectrum of telemedicine scenarios, which can reduce the costs of assistance offered to patients with respiratory diseases.

Comparative analysis of phase difference estimation methods quantifying asynchronies between compartmental chest wall volume signals

Asynchronous breathing movements may be observed in the presence of pulmonary disease, such as chronic obstructive pulmonary disease (COPD). This study was undertaken in an attempt to propose a reliable methodology to quantify this asynchrony. Five methods for estimating phase differences between two signals, based on the phase angle of the Fourier Transform (PhD(FT)), paradoxical motion (PhD(PM)), the Lissajous figure (PhD(LF)), maximal linear correlation (PhD(P)) and least-squares filtering (PhD(LS)), were compared. Frequency-modulated signals, simulating compartmental chest wall volumes, were used to evaluate the methods. Breathing asynchrony was quantified in two ways; by estimating (a) a single PhD value for the entire recording and (b) time-varying PhDs, representing non-stationarities of human breathing. PhD(PM) and PhD(LF) had the lowest average errors (4%), and PhD(LS) had a slightly higher error. PhD(FT) had zero error when estimating a single PhD value but a considerable error when estimating time-varying PhDs. PhD(P) presented the highest errors in all cases. An application of this methodology is proposed in real compartmental chest wall volume signals of normal and COPD subjects. Preliminary results indicate that the methodology is promising in quantifying differences in asynchronous breathing between thoracic volumes of COPD patients and healthy controls.

[The characteristics of the mechanical activity of the respiratory muscles during the diaphragmatic respiration technic]

Noteworthy among breathing training techniques is so-called diaphragmatic breathing. In spite of the technique's name, however, little is known of the functional characteristics of this ventilatory method.

OBJECTIVE

To asses the mechanics of respiratory muscles, particularly diaphragm muscles, during diaphragmatic breathing in patients with severe chronic obstructive pulmonary disease (COPD).

METHODS

Ventilatory pattern and respiratory pressures (abdominal [Pga], intrathoracic [Pes] and transdiaphragmatic [Pdi]) were studied in 10 patients with severe COPD in stable phase (age 69 +/- 6 years, FEV1 33 +/- 12% ref) at baseline and during deep breathing with spontaneous muscle recruitment (SMR) and during breathing training. Measurements were taken with the patient seated and in supine decubitus position.

RESULTS

In seated position ventilatory pattern was similar with SMR and during breathing training. Mean Pdi during airflow, however, was greater during breathing training than with SMR (34.8 +/- 8.0 and 29.3 +/- 9.3 cmH2O, respectively, p < 0.05) for similar levels of Pes. Mechanical effectiveness of the diaphragm expressed as Vt/Pdi) was less during breathing training, however (36.1 +/- 10.4 and 49.5 +/- 15.8 cc/cmH2O, p < 0.05), with no changes in overall efficacy of respiratory muscles (Vt/Pes). In supine decubitus position, ventilatory patterns of SMR and breathing training were similar, although Vt and T1 were slightly higher in the latter (1,065 +/- 305 vs. 1,211 +/- 314 cc, p < 0.01; and 2.76 +/- 1.32 vs. 3.07 +/- 1.23 sec, p < 0.05). Pdi was also higher during breathing training (29.7 +/- 10.2 and 38.0 +/- 10.5 cmH2O, p < 0.05), although accompanied in this case by a higher Pes (21.2 +/- 7.5 to 26.4 +/- 8.4 cmH2O, p < 0.005). In supine decubitus position, the effectiveness of both diaphragm muscles and respiratory muscles overall was similar for both ventilatory modes.

CONCLUSIONS

Breathing training truly involves greater use of the diaphragm, both in seated and supine decubitus positions. Breathing training does not provide greater ventilatory efficacy than SMR, however, in COPD patients.

Respiratory muscle function in patients with chronic obstructive pulmonary disease

Respiratory muscle (RM) dysfunction is a progressive process, including both RM weakness and fatigue, that may advance to the point of respiratory failure. It occurs as a result of increased RM workloads, altered length-tension relationship of respiratory muscles, malnourished states, and altered cellular environment in chronic obstructive pulmonary disease (COPD). Consideration of multiple patient factors is necessary when identifying patient risk for RM dysfunction and designing plans of care. This article discusses the RM pump, including its measurement, in patients with COPD.

Asynchronous chest wall movements during non-rapid eye movement and rapid eye movement sleep in children with bronchopulmonary dysplasia

The aim of this study was to assess whether age-related changes in thoracic shape modify patterns of thoracoabdominal asynchrony (TAA) or applicability of phase angle analysis during sleep in young children with increased respiratory loads. We assessed TAA during polysomnographic monitoring in 14 young children (mean age 32 months, range 19 to 46; mean weight 12.5 kg, range 9.3 to 17) with severe bronchopulmonary dysplasia (BPD). Of the patients 10 were severely enough affected to require tracheostomy. We measured asynchrony of rib cage (RC) and abdominal (AB) movements at midinspiration and the corresponding phase angle from oscillographic recordings during both non-REM and REM sleep. We measured the amplitude of "paradoxical" displacement of either RC or AB during inspiration and expressed this as a percentage of the total displacement of the compartment. Of 9 children who manifested early inspiratory AB paradox during non-REM sleep, 7 showed a figure eight on the Konno-Mead diagram. The magnitude of abdominal paradox during non-REM sleep was significantly positively correlated with age (n = 14, r = 0.68; p < 0.01). Phase angle was significantly negatively correlated with dynamic lung compliance (n = 14, r = -0.66; p < 0.01). During REM sleep, expiratory abdominal muscle activity was abolished and all patients with abdominal paradox "converted" to an open loop with RC paradox during inspiration. Graphic assessment of the Lissajous figure on the Konno-Mead diagram indicated when midinspiratory phase angle analysis did not reflect the severity of TAA and can be used to infer patterns of respiratory muscle recruitment. We conclude that young children manifest patterns of TAA that differ from the early inspiratory RC paradox commonly observed in infants. Comparison of RC-AB loops between non-REM and REM sleep in the same child can assess increased thoracic inspiratory efforts and expiratory muscle activity as potential mechanisms for abdominal paradox, as distinct from diaphragm ineffectiveness.

The effect of hyperinflation on rib cage-abdominal motion

Abnormalities of rib cage-abdominal motion are common in patients with chronic obstructive pulmonary disease (COPD), but the basis of the abnormal motion has not been completely determined. Although airway obstruction has been shown to be a major factor in causing abnormal chest wall motion, the effect of hyperinflation (which has numerous adverse effects on respiratory muscle function) has not been systematically examined. We induced graded levels of hyperinflation in six healthy volunteers using continuous positive airway pressure (CPAP) levels of 10, 20, and 30 cm H2O. Chest wall motion was measured by a calibrated inductive plethysmograph. Rib cage-abdominal asynchrony and paradox were quantitated by the Konno-Mead method of analysis. CPAP levels of 10, 20, and 20 cm H2O produced increases in end-expiratory lung volume of 0.98 +/- 0.14 (SE), 1.90 +/- 0.31, and 2.42 +/- 0.37 L, respectively (p < 0.0001). This corresponded to an increase in the ratio of functional residual capacity to predicted total lung capacity from 0.38 +/- 0.08 at baseline to 0.74 +/- 0.14 at 30 cm H2O CPAP-comparable to that seen in patients with COPD. Hyperinflation induced an increase in inspiratory abdominal paradox, 1.0 +/- 0.7% at baseline versus 3.6 +/- 1.7% at 30 cm H2O (p < 0.05), but this is unlikely to be clinically significant. A significant increase in asynchrony or rib cage paradox did not develop with hyperinflation. In conclusion, the primary factor contributing to abnormal chest wall motion in patients with COPD is likely to be increased airway resistance, and hyperinflation makes only a minor contribution.

The control of breathing during weaning from mechanical ventilation

Using the recruitment threshold technique, we measured the CO2 responsiveness of the unloaded respiratory pump in 14 mechanically ventilated patients prior to weaning. The CO2 recruitment threshold (CO2RT) was compared with the arterial CO2 tension during unassisted breathing (CO2SB) and with the PaCO2 during mechanical ventilation (CO2MV) at machine settings determined by the primary physician. Based on these comparisons, we tested the hypotheses that (1) patients without weaning-induced respiratory distress (group 1) maintain CO2SB near CO2RT, (2) patients with weaning-induced respiratory distress (group 2) retain CO2SB above CO2RT, thereby manifesting incomplete load compensation, and (3) CO2MV is ventilator setting dependent and provides insufficient information about the ventilatory requirement during weaning. Respiratory distress was prospectively defined as sustained tachypnea (rate greater than or equal to 30) or intense dyspnea (Borg scale rating) and limited weaning in nine of 14 patients. The average CO2RT was 40 mm Hg in both groups. All patients in group 1 maintained CO2SB near CO2RT (p greater than 0.1). Seven of nine patients in group 2 retained CO2 by greater than or equal to 3 mm Hg above CO2RT (p less than 0.01). There was no significant difference between CO2MV and CO2SB in either group. We conclude that CO2RT provides a better reference of the adequacy of ventilatory load compensation during weather than CO2MV.

Chronic lung disease in the sleep apnea syndrome

Several well controlled epidemiologic and hemodynamic studies suggest that about 20% of sleep apnea syndrome (SAS) patients will have chronic obstructive pulmonary disease (COPD), and the majority of these patients (with combined diseases) will have pulmonary hypertension. Indeed it has been suggested that only patients with underlying hypoxemia, such as that from COPD, will develop right heart failure in the OSA setting. Experience shows that apnea/COPD patients will have severe hypersomnolence associated with the OSA, cough and dyspnea with the airways disease, and edema and plethora related to chronic hypoxemia. Many patients present with respiratory failure and are diagnosed at the time of initial intubation and mechanical ventilation. Episodic nocturnal hypoxemia may be worsened by a steeper rate of desaturation due to lower alveolar and blood oxygen stores, and longer apneas perhaps contributed to by depressed chemosensitivity. Daytime hypoxemia may also add to the severe hemodynamic disturbances. Since COPD cannot be cured, aggressive treatment of SAS is critical. Past studies have shown that tracheostomy or nasal CPAP in this setting not only leads to resolution of episodic nocturnal desaturation but may lead to rapid improvement in daytime oxygenation in many patients. Pulmonary hypertension and other measures of cardiopulmonary function improve when apnea is cured. Elimination of the SAS may disclose nonapneic REM related desaturation that could require supplemental oxygen therapy in addition to tracheostomy or nasal CPAP. Pulmonary function testing in SAS patients with smoking histories, followed by aggressive treatment of SAS, is recommended.

Factors influencing ventilatory muscle recruitment in patients with chronic airflow obstruction

Patients with chronic airflow obstruction (CAO) frequently develop abnormal thoraco-abdominal excursion, but the patterns described are inconsistent and the factors that relate to their development remain unknown. We studied 45 stable patients with FEV1 ranging from 0.36 to 2.1 L. A pattern of ventilatory muscle recruitment (VMR) was established by simultaneously measuring gastric (Pg) and pleural (Ppl) pressures and rib cage (Vrc) and abdominal (Vab) volume displacement with inductance plethysmography. From these tracings, Pg-Ppl plots were constructed and the delta Pg/delta Ppl values were calculated. The delta Pg/delta Ppl was validated in 15 patients with simultaneous analysis of Vab-Pg plots. Pearson's test and multiple regression analyses were used to correlate delta Pg/delta Ppl to factors thought to influence respiratory muscle function such as age, sex, nutritional status (weight/height, albumin), hyperinflation, airflow obstruction, and arterial blood gases. We found a direct correlation between a more positive delta Pg/delta Ppl value and increasing hyperinflation (r = 0.69, p less than 0.0001), increasing airflow obstruction (r = -0.55, p less than 0.001), and decreasing diaphragmatic strength (r2 = 0.32, p less than 0.001). We also found that expiratory Ppl became more positive with decreasing FEV1 (r2 = 0.33, p less than 0.001). This change in VMR was independent of age, sex, nutritional status, and arterial blood gas determinations.(ABSTRACT TRUNCATED AT 250 WORDS)

The reduction of weaning time from mechanical ventilation using tidal volume and relaxation biofeedback

We sought to determine if biofeedback could reduce weaning time for the hard-to-wean patient by improving important weaning factors that are not effectively dealt with by present weaning methods. These include respiratory muscle electromyograph (EMG) efficiency, respiratory drive, and the anxiety of the ventilator-dependent patient. After the patient had received mechanical ventilation for 7 days and the day weaning began (start), the patient was randomly assigned to biofeedback or to the control group. There were 20 patients assigned to each group, with mean ages of 60.2 (biofeedback) and 59.3 (control) yr. The patients assigned to the biofeedback group received daily, until extubation or being placed on no resuscitation status (termination), frontalis electromyographic (EMG) relaxation feedback for anxiety reduction and improved respiratory muscle EMG efficiency, tidal volume/diaphragm EMG (VT/DAP), and VT feedback for increasing VT and respiratory drive defined as tidal volume/inspiratory time (VT/TI). The control group was visited daily to control for attention and reassurance. The results showed a significant (p less than 0.01) reduction in mean ventilator days for the biofeedback group of 20.6 +/- 8.9 SD compared with 32.6 +/- 17.6 SD mean days for the control group. From start to termination, there was a significant (p less than 0.01) increase in baseline VT, from 295 +/- 41 to 415 +/- 45 ml, and a significant (p less than 0.02) increase in VT/DAP, from 0.33 +/- 0.09 to 0.94 +/- 0.22 L/mV for the biofeedback group but no significant change in these parameters for the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive detection of respiratory failure in the intensive care unit

We investigated the utility of a noninvasive respiratory inductive plethysmograph (RIP) to continuously monitor and record the breathing pattern of 44 patients who had been mechanically ventilated. Seven patients deteriorated on intermittent mandatory ventilatory rate of zero; seven deteriorated within 48 h following extubation; 30 were successfully extubated. Respiratory alternans was documented by RIP in 11 patients who failed whereas it was absent in all other patients. Respiratory rates in the 14 failure patients increased when compared with rates one hour before clinical deterioration and with rates of 30 patients who were successfully extubated. Total compartmental displacement/tidal volume increased in every patient who developed respiratory failure. Changes in the breathing pattern, specifically onset of rib cage-abdominal asynchrony, can be diagnosed noninvasively, thus alerting the clinical staff prior to onset of overt respiratory failure and arrest.

Diaphragmatic fatigue and breathing pattern during weaning from mechanical ventilation in COPD patients

The medium-term outcome of weaning from mechanical ventilation in COPD patients is not easy to anticipate because a respiratory fatigue may eventually develop. We evaluated the diaphragmatic function and the breathing pattern during 40 weaning trials on 15 patients ventilated after acute respiratory failure. We formed two groups according to the success (group B, n = 18) or failure (group A, n = 19) of the medium-term attempt (group A/less than 10 hours; group B/more than 12 hours). Provided the patients showed the classic weaning criteria (tidal volume greater than 5 ml/kg, respiratory frequency less than 30 breaths per minute, PaO2 greater than 50 mm Hg), the study of the breathing pattern did not allow differentiation between the groups. However, the transdiaphragmatic pressure (Pdi) and the Pdimax, which gave an indication of the power of diaphragm contraction, dropped early in the group that could not stand weaning, with an increase in the Pdi/Pdimax ratio. In addition, this same group showed a diaphragmatic dysfunction attested for by a frequent negative gastric pressure associated with or shortly preceded by an abdominal paradoxic motion.

Bilateral diaphragmatic paralysis complicating local cardiac hypothermia during open heart surgery

Filling the pericardial sac with ice and saline during open heart surgery protects the myocardium during periods of ischemic arrest. Bilateral diaphragmatic paralysis complicated intense local hypothermia in five patients undergoing coronary artery bypass surgery. All complained of severe orthopnea, exertional dyspnea, insomnia, and excessive daytime somnolence. All exhibited paradoxic inward movement of the abdominal wall with inspiration. The diagnosis of bilateral diaphragmatic paralysis was confirmed with upright and supine spirometry and, in one patient, with transdiaphragmatic pressure measurements. Although paralysis has resolved in four patients, all experienced months of disabling impairment. One patient required four months of mechanical ventilatory support prior to her recovery. Alternative methods of intraoperative myocardial preservation that avoid this complication should be developed.

Abnormalities of chest wall motion in patients with chronic airflow obstruction

Forty patients with severe chronic stable airflow obstruction and hyperinflation were studied to assess patterns of abnormal chest wall motion and their frequency. Dimensional changes were measured during tidal breathing, four pairs of magnetometers being used to record anteroposterior diameters of ribcage and abdomen and two lateral diameters of the ribcage. Chest wall movements were qualitatively normal in only five patients. Three main types of abnormality were found and 13 subjects had two or more abnormal patterns. Lateral ribcage paradox was present in 31 of the 40 patients and was recognised clinically in all except one. Inspiratory indrawing of the lower sternum was recorded in 12 patients, paradoxical inspiratory motion of the abdomen was present in four patients and in six there was a biphasic expiratory pattern of abdominal movement. Analysis of variance showed no significant group differences in severity of airflow obstruction or hyperinflation between the patients with qualitatively normal motion and those with different types of abnormal motion. Relationships between the tidal displacement of each dimension and severity of airflow obstruction and hyperinflation were examined. In general, patients with more severe hyperinflation showed less abdominal movement and those with severe airflow obstruction had less lateral expansion of the ribcage, but the correlations were weak. It is concluded that abnormal motion of the chest wall is very common in patients with airflow obstruction and hyperinflation, that clinical recognition of abnormal motion other than lateral ribcage paradox is easily overlooked, and that quantitative relationships between abnormal motion and disease severity are weak.

Respiratory failure following intercostal nerve blockade

A case of respiratory failure following postoperative intercostal nerve blockade is described. A possible mechanism is postulated and the evidence in favour of intercostal blockade in patients with chronic airways disease is questioned. The need for caution when managing such patients with regional blockade is emphasised.

Measurement of chest wall movement; design, performance and clinical use of a four-channel magnetometer instrument

A four-channel magnetometer instrument is described. It has been developed to measure changes in diameters of the chest and abdomen during respiration. A linearisation correction allows for the magnetic field strength detected by the receiver being proportional to the inverse cube of the diameter being measured. Diameters and changes in diameter are measured to an accuracy of 4% (1 SD) over the working range (15-50 cm). The effects of non-ideal positioning and extraneous movements of the magnetometer coils, cross-channel interference and the influence of nearby metals are described. With minimal care in positioning the coils, these effects are negligible. The instrument has been in use for one year, assessing chest wall movement in patients with abnormal lung function. Recordings are presented illustrating typical normal and abnormal chest wall movements.

Effects of an increase in end-expiratory volume on the pattern of thoracoabdominal movement

Changes in end-expiratory lung volume can alter the mechanical function of the muscles of inspiration and may affect the pattern of thoracoabdominal movements. The present study examined the effect of increasing end-expiratory lung volume on the motion of the rib cage and abdomen during inspiration. In six seated subjects, end-expiratory volume was increased by expiratory threshold loading. The end-expiratory thoracoabdominal configuration shifted to the left of the relaxation curve presumably as a result of the activation of the abdominal expiratory muscles. There was outward displacement of both the rib cage and the abdomen with inspiration at the elevated volume but the relative volumetric contribution of abdominal displacement to the inspired volume was significantly less than during breathing from FRC. When at an enlarged lung volume subjects were constrained to initiate inspiration from a point on the thoracoabdominal relaxation configuration, there was inward movement of the abdomen and a decrease in abdominal dimensions during inspiration. Inward abdominal movement occurred despite large increases in diaphragm electrical activity and was associated with an inspiratory fall in gastric pressure. These results suggest that at large lung volumes, the function of the diaphragm as an agonist is lost and its function as a fixator may be impaired unless there is an activation of the abdominal muscles and the diaphragm is appropriately lengthened.

Breathing patterns. 2. Diseased subjects

We measured the breathing pattern of normal subjects, asymptomatic smokers, asymptomatic and symptomatic asthmatic patients, and patients with chronic obstructive pulmonary disease, restrictive lung disease, primary pulmonary hypertension and anxiety state utilizing respiratory inductive plethysmography. Respiratory rate was increased above the normal in smokers and in patients with COPD, restrictive lung disease and pulmonary hypertension, but remained normal in asthmatic patients. Inspiratory times (T1) of one second or less often occurred in patients with COPD, restrictive lung disease, and pulmonary hypertension. Smokers and patients with symptomatic asthma, COPD, restrictive lung disease and pulmonary hypertension showed heightened respiratory center drive as reflected by elevated mean inspiratory flow (VT/TI). Fractional inspiratory time was reduced to a variable extent in smokers, symptomatic asthmatic patients and patients with COPD, and was a weak indicator of airways obstruction. Patients with COPD often had major fluctuations of expiratory timing, periodic fluctuations of end-expiratory level, and asynchrony between rib cage and abdominal movements. Chronic anxiety was characterized by frequent sighs; episodic rapid rates alternating with apneas were less common. We conclude that analysis of breathing patterns provides diagnostic discrimination among normal subjects and disease states.

Validation of respiratory inductive plethysmography in patients with pulmonary disease

The assumption that the respiratory system behaves with 2 df of motion in healthy persons allows calibration of respiratory inductive plethysmography (RIP) with spirometry (SP). To ascertain whether RIP could be calibrated by the same assumption in patients with lung disease, even though at least 3 df of motion are visualized (ie, upper and lower rib cage and upper and lower abdomen move out of phase), RIP was calibrated by a two-position calibration procedure and validated satisfactorily by simultaneous SP in the erect, semirecumbent, supine, and lateral decubitus positions. In lung disease, the contribution to tidal volume of regions moving independently of the combined rib cage and abdominal movements either is small or remains relatively constant with change of body posture. For clinical monitoring of the resting breathing pattern where patient movements cannot be restricted, respiratory inductive plethysmography can serve as a reliable semiquantitative, noninvasive ventilatory monitoring device.

Thoracoabdominal mechanics during tidal breathing in normal subjects and in emphysema and fibrosing alveolitis

Thoracoabdominal motion and intrathoracic (oesophageal), intra-abdominal (gastric), and transdiaphragmatic pressures were measured during tidal breathing in 20 erect subjects--six normal, seven, with emphysema, and seven with fibrosing alveolitis. In normal subjects all diameters increased synchronously during inspiration and were accompanied by rises in abdominal and transdiaphragmatic pressures. Five patients with fibrosing alveolitis showed a reduction in upper ribcage motion, but normal lower ribcage and abdominal motion; stiff fibrotic lungs may sometimes impair the ability of the diaphragm to expand the upper ribcage and result in proportionally more expansion of the bases. Four emphysematous patients showed increased anteroposterior motion of the ribcage and four showed paradoxical inward motion of the lower ribcage during inspiration. These changes apparently result from increased activity of intercostal and accessory muscles and altered configuration of the diaphragm. The muscles of patients with large, overinflated lungs are at a greater disadvantage than those with small fibrosed lungs.

Increased exercise performance in patients with severe COPD following inspiratory resistive training

Six patients with severe chronic obstructive pulmonary disease underwent a six-week outpatient program to train their respiratory muscles with an inspiratory resistive device. Exercise performance was measured using a cycle ergometer. Maximum exercise capacity, represented by VO2 max, increased 15 percent. The maximum work rate increased 37 percent, and the minute ventilation attained during exercise increased 17 percent after training. Respiratory muscle endurance increased 56 percent. All patients reported an increased ability to perform the activities of daily living. No changes were reported in three patients who underwent sham training.