Chest Wall Motion Research Articles

SU‐E‐T‐476: 4‐Dimensional Dosimetric Comparison of Stereotactic Body Radiation Therapy for Lung Tumor With Versus Without Tumor Tracking Technique

Purpose: Recently a new treatment device capable of gimbal‐based tumor tracking (Vero, BrainLAB AG, Feldkirchen, Germany) was installed at our institution. The purpose of this study is to compare dose‐volume and radiobiological parameters associated with treatment efficacy and normal tissue toxicity for lung SBRT using a conventional linac with and without tumor tracking. Methods: A digital torso phantom having the capability to simulate respiratory and cardiac motion was used for this work. Spherical targets having a diameter of 20mm were centrally located within the right lung. 12 non‐coplanar, non‐opposing conformal beams were designed for linac planning with and without tumor tracking to deliver 60Gy in 3 fractions, prescribed to cover 95% of the target. 4D dose calculations were performed using the Monte Carlo algorithm in iPlan™ using a voxel tracking technique for the moving target and surrounding tissue. Diaphragm motion was varied from 10–30 mm in the superior‐inferior direction to simulate different motion amplitudes while limiting chest wall motion to 10mm in the anterior‐posterior direction. Dose‐volume analysis was performed using parameters previously shown to correlate with normal tissue toxicity for lung SBRT. Results: All indices used to assess normal tissue toxicity were reduced for the tumor tracking model compared with non‐tracking delivery. Mean lung dose, equivalent ipsilateral lung dose delivered in 2Gy fractions, and V13 were reduced by 17%, 21%, and 22% and 27%, 30%, and 36% for small and large diaphragm motion, respectively. The maximum heart dose was reduced by 7% for small diaphragm motion and by 9% for larger diaphragm motion. Conclusion: This work validates the ability of tumor tracking techniques to increase the dose to moving targets while reducing dose to surrounding normal tissues. It is expected that SBRT dose escalation using tumor tracking techniques will improve local control while reducing rates of normal tissue toxicity.

Bioimpedance-based respiratory gating method for oncologic positron emission tomography (PET) imaging with first clinical results

Respiratory motion may cause significant image artefacts in positron emission tomography/computed tomography (PET/CT) imaging. This study introduces a new bioimpedance-based gating method for minimizing respiratory artefacts. The method was studied in 12 oncologic patients by evaluating the following three parameters: maximum metabolic activity of radiopharmaceutical accumulations, the size of these targets as well as their target-to-background ratio. The bioimpedance-gated images were compared with non-gated images and images that were gated with a reference method, chest wall motion monitoring by infrared camera. The bioimpedance method showed clear improvement as increased metabolic activity and decreased target volume compared to non-gated images and produced consistent results with the reference method. Thus, the method may have great potential in the future of respiratory gating in nuclear medicine imaging.

Airway management using a supraglottic airway device without endotracheal intubation for positive ventilation of anaesthetized rats

Endotracheal intubation is often necessary for positive pressure ventilation of rats during open thoracic surgery. Since endotracheal intubation in rats is technically difficult and is associated with numerous complications, many techniques using various devices have been described in the scientific literature. In this study, we compared the effectiveness of airway management of a home-made supraglottic airway device (SAD), which is cheap to fabricate and easy to place with that of an endotracheal intubation tube in enflurane-anaesthetized rats. Twenty male Sprague-Dawley rats (200-300 g) were randomly assigned to two equal groups for positive pressure mechanical ventilation using either the SAD or an endotracheal intubation tube. The carotid artery of each rat was cannulated for continuous blood pressure measurements and obtaining blood samples for determination of oxygen tension, carbon dioxide tension, and blood acidity before, during and after SAD placement or endotracheal intubation. Proper placement of the SAD was confirmed by observing chest wall movements that coincided with the operation of the mechanical ventilator. No complications and adverse events were encountered in the rats in which the SAD was placed, during SAD placement and immediate removal, during their mechanical ventilation through the SAD, and one week after SAD removal. From the results of blood gas analyses, we conclude that anaesthetized rats can be successfully ventilated using an SAD for open thoracic surgery.

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.

Infant Cardiac Magnetic Resonance Imaging Using Oscillatory Ventilation: Safe and Effective

Cardiac magnetic resonance imaging (CMR) for infants and young children typically requires sedation. General anesthesia with controlled ventilation can eliminate motion artifact with breath-holds during imaging to limit respiratory artifact, but these may lead to atelectasis or other complications. High-frequency oscillatory ventilation (HFOV) provides ventilation with near-constant mean airway pressure and minimal movement of chest wall and diaphragm, thus obviating the need for breath-holding. Clinical data were collected for 8 infants who underwent CMR with HFOV and 8 controls who underwent CMR with conventional ventilator and breath-hold technique. Data included demographic information, adverse events, and scan-acquisition time. Studies were reviewed for image quality by two cardiologists who were blinded to type of ventilation. There were no significant differences in patient characteristics between the two groups. There was no significant difference in average image quality for cine short-axis or black blood imaging. Total CMR scan time was not significantly different between groups, but the short-axis cine stack was acquired more quickly in the HFOV group (1.8 ± 0.8 vs. 5.0 ± 3.6 min). There were no adverse events in the HFOV group, but scans were terminated early for two patients in the conventional ventilator group. HFOV during CMR is feasible and well tolerated. Image quality is equivalent to that obtained with conventional ventilation with breath-holding technique and allows shorter cine scan times for some sequences.

An Impulse Radio Ultrawideband System for Contactless Noninvasive Respiratory Monitoring

We design a impulse radio ultrawideband radar monitoring system to track the chest wall movement of a human subject during respiration. Multiple sensors are placed at different locations to ensure that the backscattered signal could be detected by at least one sensor no matter which direction the human subject faces. We design a hidden Markov model to infer the subject facing direction and his or her chest movement. We compare the performance of our proposed scheme on 15 human volunteers with the medical gold standard using respiratory inductive plethysmography (RIP) belts, and show that on average, our estimation is over 81% correlated with the measurements of a RIP belt system. Furthermore, in order to automatically differentiate between periods of normal and abnormal breathing patterns, we develop a change point detection algorithm based on perfect simulation techniques to detect changes in the subject's breathing. The feasibility of our proposed system is verified by both the simulation and experiment results.

Noninvasive Monitoring during Interhospital Transport of Newborn Infants

The main indications for interhospital neonatal transports are radiographic studies (e.g., magnet resonance imaging) and surgical interventions. Specialized neonatal transport teams need to be skilled in patient care, communication, and equipment management and extensively trained in resuscitation, stabilization, and transport of critically ill infants. However, there is increasing evidence that clinical assessment of heart rate, color, or chest wall movements is imprecise and can be misleading even in experienced hands. The aim of the paper was to review the current evidence on clinical monitoring equipment during interhospital neonatal transport.

Comparison of Acoustic Respiration Rate, Impedance Pneumography and Capnometry Monitors for Respiration Rate Accuracy and Apnea Detection during GI Endoscopy Anesthesia

Study Objective: To assess the accuracy of respiration rate measurements and the ability to detect apnea by capnometry, impedance pneumography and a new method, acoustic respiration rate monitoring, in anesthetized patients undergoing gastrointestinal endoscopy procedures. Design: Prospective observational study. Setting: Endoscopy procedures laboratory. Patients: 98 patients scheduled for upper gastrointestinal endoscopy with propofol-based anesthesia. Interventions: Patients were monitored for respiration rate with acoustic respiration rate monitoring, capnometry and impedance pneumography and values were compared to the manual counting of breaths by observation of chest wall movements. Additionally, when any respiration rate monitor indicated a cessation of breathing for 30 seconds or greater, the presumed apnea was confirmed by direct observation of the patient for absence of chest wall movements. Measurements and Main Results: Bias and precision for respiration rate measurement was 0 ± 1.0 bpm for acoustic monitoring, 4.8 ± 15.1 bpm for capnometry and 0.4 ± 5.9 bpm for impedance pneumography. Sensitivity and specificity for detection of apnea was 73% and 93% for acoustic monitoring, 73% and 12% for capnometry and 45% and 93% for impedance pneumography. Conclusions: Acoustic respiration rate monitoring was found to be accurate for assessment of respiration rate and to have similar or better sensitivity and specificity for detection of apnea compared to capnometry and impedance pneumography in the setting of upper GI endoscopy.

Pseudomesotheliomatous Adenocarcinoma of Lung: A Diagnostic Dilemma

A 52 years old farmer developed left-sided chest pain 4 months prior to admission that was dull aching, episodic, lasting for 1 to 2 minutes, relieved of its own and increased on deep inspiration. He was found to have left-sided pleural effusion. Pleural fluid analysis revealed straw colored fluid with positive stain for acid fast bacilli at Civil Hospital, Rupnagar. He was enrolled under Revised National Tuberculosis Control Programme (RNTCP) for directly observed antitubercular treatment (DOTS) as a new case. Despite 2 months of treatment, there was no symptomatic improvement and repeat evaluation showed a persistent large pleural effusion. Therapeutic thoracocentesis (2-3 times) was done followed by intercostal chest tube insertion 2 months prior to admission with drainage of approximately 200 to 300 ml of hemorrhagic fluid per day. Over a period of 2 weeks preceding admission, severity of chest pain gradually increased. Six days prior to admission, he developed high grade fever associated with rigors and chills. Breathlessness started 4 days prior to admission, was acute in onset, progressing during this time period to being present at rest and not associated with orthopnea or wheeze. There was no history of cough, expectoration, hemoptysis, swelling of feet, decreased urine output or altered sensorium. There was no significant illness in the past. He was a nonsmoker with no addictions. On initial evaluation, he was conscious and oriented. He had tachycardia (130/min), normal blood pressure (130/70 mm Hg) and tachypnea (40/min) with use of accessory muscles of respiration. Pallor, bilateral pitting pedal edema and small right supraclavicular lymph nodes were noted. Examination of the chest revealed presence of a chest tube, reduced chest wall movements with signs of volume loss on the left side, dull note on percussion with reduced intensity of breath sounds in the left infraclavicular and left mammary areas. The clinical findings were consistent with those of pleural effusion. Per abdomen, the liver was palpable 2 cm below right subcostal margin with no other specific features. Spleen was not palpable, there was no tenderness or free fluid and bowel sounds were present. Rest of the systemic examination was unremarkable.

Hemodynamics during piston based mechanical chest compressions with and without lateral support – A randomized, cross-over experimental study.Status: PendingCategory: CPR Quality

Purpose of the study: Chest compressions generate blood flow by directly squeezing the heart between the sternum and the spine. In the flexible rib cage much force will be diverted laterally. Force could be concentrated by limiting the lateral deformation of the chest wall allowing improved forward blood flow. Conversely, limiting lateral chest wall movement could represent “lateral leaning”, where increased right atrial pressure (RAP) would lead to decreased coronary perfusion pressure (CPP). We studied the effect on hemodynamics with piston based mechanical chest compressions with or without lateral support in a randomized, cross-over animal experiment.

A very complex congenital heart anomaly: diagnosis through cardiac CT

A 30-year-old male patient was referred to our institute by a private cardiologist for cardiac computed tomography (CT) due to atypical chest pain and wall motion abnormality on echocardiography. He had a history of hypercholesterolaemia and smoking, whereas his family history was unremarkable. Rest ECG was entirely normal. Multislice …

Effects of an opioid on respiratory movements and expiratory activity in humans during isoflurane anaesthesia

Opioids increase abdominal muscle activity during anaesthesia. We proposed that opioid activity during anaesthesia would change chest wall size and movement, and contribute to ventilation. Using an optical system to measure chest wall volume, we studied 10 patients during isoflurane anaesthesia, first under the influence of an opioid and then after reversal with naloxone. Measurements were made during quiet breathing and with carbon dioxide stimulation. Airway occlusion pressure was measured to assess inspiratory and expiratory muscle activity. Chest wall volume decreased with the onset of spontaneous breathing, and decreased further when breathing was stimulated by carbon dioxide. Reversal of opioid activity increased chest wall volume. Breathing movements were predominantly abdominal. Opioid action affected the timing and amplitude of breathing but the pattern of abdominal movement was not affected. Since opioids augment abdominal muscle action during expiration, the unchanged pattern of movement can be attributed to both diaphragm and abdominal activity displacing the abdominal wall reciprocally, in the inspiratory and expiratory phases of the respiratory cycle, respectively.

Treatment with Gabapentin Associated with Resolution of Apnea in Two Infants with Neurologic Impairment

Infants with neurologic impairment (NI) as a result of injury to the central nervous system have a significant rate of pain. Problems associated with pain in children with NI include increased tone. This secondary hypertonia may contribute to apnea as a result of alterations in airway tone and chest wall movement. Infants are at greatest risk given their smaller airways, lower functional residual capacity, and the high rate of unrecognized pain at this age. We report two cases of infants with NI, identified to have significant improvement in apnea following empiric treatment with gabapentin for presumed central pain and/or visceral hyperalgesia. This correlation between pain and apnea, with resolution in apnea following effective treatment of these presumed sources, has not been previously reported in the literature. Infants with NI and apnea should have careful pain assessment and treatment, when considering other causes and interventions for apnea.

Ventilation heterogeneity: small length scales, big challenges

the distribution of regional ventilation is heterogeneous in normal lung and increases dramatically under pathological conditions. This has been demonstrated both in humans and in animal models using a number of different imaging techniques. General anesthesia and mechanical ventilation can

SU-E-J-126: Generation of Fluoroscopic 3D Images Using Single X-Ray Projections on Realistic Modified XCAT Phantom Data.

To simulate the process of generating fluoroscopic 3D treatment images from 4DCT and measured 2D x-ray projections using a realistic modified XCAT phantom based on measured patient 3D tumor trajectories. First, the existing XCAT phantom is adapted to incorporate measured patient lung tumor trajectories. Realistic diaphragm and chest wall motion are automatically generated based on input tumor motion and position, producing synchronized, realistic motion in the phantom. Based on 4DCT generated with the XCAT phantom, we derive patient-specific motion models that are used to generate 3D fluoroscopic images. Patient-specific models are created in two steps: first, the displacement vector fields (DVFs) are obtained through deformable image registration of each phase of 4DCT with respect to a reference image (typically peak-exhale). Each phase is registered to the reference image to obtain (n-1) DVFs. Second, the most salient characteristics in the DVFs are captured in a compact representation through principal component analysis (PCA). Since PCA is a linear decomposition method, all the DVFs can be represented as linear combinations of eigenvectors. Fluoroscopic 3D images are obtained using the projection image to determine optimal weights for the eigenvectors. These weights are determined through iterative optimization of a cost function relating the projection image to the 3D image via the PCA lung motion model and a projection operator. Constructing fluoroscopic 3D images is thus reduced to finding optimal weights for the eigenvectors. Fluoroscopic 3D treatment images were generated using the modified XCAT phantom. The average relative error of the reconstructed image over 30 sec is 0.0457 HU and the standard deviation is 0.0063. The XCAT phantom was modified to produce realistic images by incorporating patient tumor trajectories. The modified XCAT phantom can be used to simulate the process of generating fluoroscopic 3D treatment images from 4DCT and 2D x-ray projections.

Adaptation and applications of a realistic digital phantom based on patient lung tumor trajectories

Digital phantoms continue to play a significant role in modeling and characterizing medical imaging. The currently available XCAT phantom incorporates both the flexibility of mathematical phantoms and the realistic nature of voxelized phantoms. This phantom generates images based on a regular breathing pattern and can include arbitrary lung tumor trajectories. In this work, we present an algorithm that modifies the current XCAT phantom to generate 4D imaging data based on irregular breathing. First, a parameter is added to the existing XCAT phantom to include any arbitrary tumor motion. This modification introduces the desired tumor motion but, comes at the cost of decoupled diaphragm, chest wall and lung motion. To remedy this problem diaphragm and chest wall motion is first modified based on initial tumor location and then input to the XCAT phantom. This generates a phantom with synchronized respiratory motion. Mapping of tumor motion trajectories to diaphragm and chest wall motion is done by adaptively calculating a scale factor based on tumor to lung contour distance. The distance is calculated by projecting the initial tumor location to lung edge contours characterized by quadratic polynomials. Data from ten patients were used to evaluate the accuracy between actual independent tumor location and the location obtained from the modified XCAT phantom. The RMSE and standard deviations for ten patients in x, y, and z directions are: (0.29 ± 0.04, 0.54 ± 0.17, and0.39 ± 0.06) mm. To demonstrate the utility of the phantom, we use the new phantom to simulate a 4DCT acquisition as well as a recently published method for phase sorting. The modified XCAT phantom can be used to generate more realistic imaging data for enhanced testing of algorithms for CT reconstruction, tumor tracking, and dose reconstruction.

Nasopharyngeal oxygen with intermittent nose-close and abdomen-compression: A novel resuscitation technique in a piglet model

To evaluate the efficacy of a simple and novel cardiopulmonary resuscitation (CPR) technique, nasopharyngeal oxygen with intermittent nose-close and abdomen-compression (NPO(2) -NC-AC) in an animal model. Prospective piglet study. In an animal physiology laboratory of a medical university. PIGLETS: Six healthy piglets <14 days old. Spontaneous breathing of the anesthetized piglets (n = 6) was medically ceased until severe bradycardia (<20 beat/min). NPO(2) -NC-AC CPR trial was then initiated by delivering NPO(2) at 1.0-1.5 L/kg/min and intermittently performing the NC-AC maneuver: (1) NC for inspiration, occluded nostrils for 1 sec; and (2) AC for expiration, released nostrils, and compressed the abdomen for 1 sec. NC-AC was repeated at a rate of 30/min for 5 min. This CPR trial was repeated three times in each piglet. Cardiopulmonary variables were monitored, recorded, and compared. A total of 18 CPR trials were performed. All of these acute life-threatening asphyxia events rapidly improved within 1 min of CPR. Cardiopulmonary variables recovered to the baseline levels and oxygenation continually increased. The intratracheal pressure (P(tr) ) values of positive end expiratory pressure and peak inspiratory pressure values were 4.3 ± 0.8 cmH(2) O and 26.2 ± 4.1 cmH(2) O, respectively. Chest wall movement was observed when the P(tr) reached 17.5 ± 3.1 cmH(2) O. All six piglets fully recovered after 63.8 ± 7.2 min of experiment without additional support. NPO(2) -NC-AC is a simple and effective CPR technique for severe acute cardiopulmonary asphyxia in piglets. It may be clinically applicable for supportive or rescue use.

Can't Intubate, Can't Ventilate

Stefanutto et al. in this issue of Anesthesia & Analgesia continue the long quest to develop an optimal anesthetic induction protocol. A technique that assures good-to-excellent conditions for tracheal intubation upon loss of consciousness, yet assures that if “can’t intubate, can’t ventilate” (CICV) conditions are encountered, then adequate spontaneous ventilatory exchange will recover before significant arterial oxygen desaturation supervenes. In healthy patients, apneic intervals of 5 to 7 minutes may elapse before desaturation ( 90% arterial saturation) following preoxygenation in the presence of a patent airway, although in patients with decreased functional residual capacity or venous admixture, this interval may be significantly shorter. The protocol of Stefanutto et al. was designed so that their subjects retained the greatest chance of maintaining oxygenation during propofol/opioid-induced apnea: they received optimal preoxygenation (end-tidal oxygen 90%), and a tightly fitted facemask with insufflated oxygen flow at 6 L/min was kept in place. Assuming a patent airway, the authors’ subjects thus benefited from some degree of “apneic oxygenation.” The authors chose to avoid the use of succinylcholine to facilitate intubation because there is convincing evidence that significant arterial hemoglobin desaturation may take place before recovery of adequate respiratory mechanics occurs after a traditional “intubating dose” of this relaxant. For example, Heier et al. were able to demonstrate that, after induction with thiopental and succinylcholine (no opioid), spontaneous recovery from succinylcholine-induced apnea frequently did not occur quickly enough to prevent arterial desaturation. The present authors hypothesized that perhaps substituting a short-acting opioid in lieu of succinylcholine might result in a shorter apneic interval. In the present investigation, they studied an induction dose of propofol (2.0 mg/kg) combined with 2 different doses of remifentanil. The first dose they selected, remifentanil 2 g/kg, resulted in arterial hemoglobin saturations 80% in one-third of subjects, although it offered acceptable intubating conditions in 11 of 12 subjects. This time course of respiratory depression and resulting arterial desaturation is consistent with remifentanil’s pharmacokinetic/pharmacodynamic profile. In another session, they reduced the dose of remifentanil to 1.5 g/kg and successfully shortened the apnea time by approximately 1 minute, but 4 of 12 subjects had unacceptable conditions for tracheal intubation. The present study thus demonstrates the limitations of a relaxant-free intubation technique using what are certainly only modest doses of propofol and remifentanil. As pointed out by Sneyd and O’Sullivan, in the absence of a good clinical reason for doing so, “attempting tracheal intubation without a neuromuscular blocking agent represents substitution of an inferior technique for one with greater efficacy.” In the “real world” of unexpected CICV, a patent airway by definition would not be present, and the adequacy of preoxygenation may be questionable. Thus, the study by Stefanutto et al. probably represents a “best case” scenario. Nevertheless, the arterial O2 saturations in 14 of 24 subjects decreased to 90% at some point. Actual patients would likely experience a faster onset of arterial oxygen desaturation during apnea than the present authors observed. An induction sequence designed to facilitate tracheal intubation ideally should do more than simply induce hypnosis and abet mechanical placement of the endotracheal tube. It should also ensure reflex suppression and cardiovascular stability. Thus, significant reductions in the authors’ doses of propofol/opioid may not be realistic. In young, healthy subjects, perhaps the propofol dosage could be decreased to 1.5 mg/kg, but doses less than remifentanil 1.0 g/kg or fentanyl 2 g/kg are unlikely to suppress the hemodynamic response to intubation. Thus, it appears that muscle relaxant-facilitated intubation is here to stay. An ideal neuromuscular blocker used for intubation should have fast onset and either rapid elimination or the potential for prompt and complete antagonism of its effect. Succinylcholine is still the “gold standard” in this regard. After a 1 mg/kg dose, succinylcholine establishes complete block at the adductor pollicis in 70 20 seconds and first twitch (T1) height recovers to 10% of control in approximately 6 minutes and to 25% of control in 7 minutes. Diaphragmatic recovery takes place approximately 2 minutes earlier, and 50% recovery of this muscle’s strength is seen in 5 to 6 minutes. These data correlate nicely with From the *Department of Anesthesiology, Weill Cornell Medical College, New York, New York; and †Department of Anesthesia, Kyoto University Graduate School of Medicine, Kyoto, Japan.

Pulmonary function in children with idiopathic scoliosis.

Idiopathic scoliosis, a common disorder of lateral displacement and rotation of vertebral bodies during periods of rapid somatic growth, has many effects on respiratory function. Scoliosis results in a restrictive lung disease with a multifactorial decrease in lung volumes, displaces the intrathoracic organs, impedes on the movement of ribs and affects the mechanics of the respiratory muscles. Scoliosis decreases the chest wall as well as the lung compliance and results in increased work of breathing at rest, during exercise and sleep. Pulmonary hypertension and respiratory failure may develop in severe disease. In this review the epidemiological and anatomical aspects of idiopathic scoliosis are noted, the pathophysiology and effects of idiopathic scoliosis on respiratory function are described, the pulmonary function testing including lung volumes, respiratory flow rates and airway resistance, chest wall movements, regional ventilation and perfusion, blood gases, response to exercise and sleep studies are presented. Preoperative pulmonary function testing required, as well as the effects of various surgical approaches on respiratory function are also discussed.

Chest wall dynamics during voluntary and induced cough in healthy volunteers

Coughing both protects the airways from foreign material and clears excessive secretions in respiratory diseases, and therefore requires high expiratory flows. We hypothesised that the volume inspired prior to coughing (operating volume) would significantly influence the mechanical changes during coughing and thus cough flow. Sixteen healthy volunteers (6 female, mean age 31 ± 10 years) performed six single voluntary coughs from four different operating volumes (10%, 30%, 60% and 90% of vital capacity) followed by three peals of voluntary and citric acid-induced coughs. During coughing we simultaneously measured (i) chest and upper abdominal wall motion using opto-electronic plethysmography (OEP), (ii) intra-thoracic and intra-abdominal pressures with a balloon catheter in each compartment and (iii) flow at the mouth. Operating volume was the most important determinant of the peak flow achieved and volume expelled during coughing, but had little influence on the pressures generated. The duration of single coughs increased with operating volume, whereas coughs were much shorter and varied little during peals. Voluntary cough peals were also associated with significant blood shift away from the trunk. In conclusion, this study has shown that operating volume is the most important determinant of cough peak flow and volume expelled in healthy individuals. During peals of coughs, similar mechanical effects were achieved more rapidly, suggesting a modification of the motor pattern with improved efficiency. Future studies investigating cough mechanics in health and disease should control for the influence of operating volume.