DOI: 10.1148/rg.284085035
RadioGraphics 2008;28:919-931
© RSNA, 2008
Quality Initiatives
Respiratory Instructions for CT Examinations of the Lungs: A Hands-on Guide1
Alexander A. Bankier, MD,
Carl R. O’Donnell, PhD, and
Phillip M. Boiselle, MD
1 From the Departments of Radiology (A.A.B., P.M.B.) and Pulmonary and Critical Care Medicine (C.R.O.), Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02215. Received February 27, 2008; revision requested March 27 and received April 14; accepted April 21. All authors have no financial relationships to disclose.
Address correspondence to A.A.B. (e-mail: abankier{at}bidmc.harvard.edu).
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Abstract
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In computed tomographic (CT) examinations of the lung, accurate visualization of the natural contrast between the low attenuation of air and the relatively higher attenuation of vessels, airways, and interstitial structures requires cooperative and coordinated respiratory maneuvers by the patient. Inadequate respiratory maneuvers can influence differences in lung attenuation and lead to misinterpretation by (a) increasing attenuation to simulate disease in normal patients, (b) decreasing attenuation to simulate normal contrast in patients with disease, or (c) creating motion artifacts. For respiratory maneuvers to be effective, patients have to be instructed before the examination and coached during it. However, comprehensive descriptions of such instructions and coaching are lacking in the radiology literature. Therefore, respiratory instructions specifically for use in thoracic CT examinations have been devised. Along with patient coaching, use of these instructions can improve image quality. With this hands-on guide, both radiologists and technologists can optimize the respiratory instructions given to their patients and thereby improve the quality of thoracic CT examinations.
© RSNA, 2008
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Introduction
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The interpretation of computed tomographic (CT) images of the lung parenchyma is based on the inherent contrast between the low attenuation of air and the relatively higher attenuation of vessels, airways, and interstitial structures. Accurate visualization of this contrast and hence of the underlying anatomic structures requires optimal respiratory maneuvers from the patient.
CT examinations of the lung are routinely performed in suspended end-inspiration to maximize the natural contrast between air and pulmonary structures. Additional CT acquisitions at suspended end-expiration can substantially facilitate the detection of diseases of both the large and small airways (1,2). For the large airways, expiratory CT should be performed in suspected tracheal and bronchial malacia. In these cases, expiratory CT will depict excessive expiratory collapse, with a frown-like configuration of the tracheal lumen (1) (Fig 1).
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Figure 1a. Tracheal collapse in a patient suspected to have tracheomalacia. (a) CT scan obtained at maximal inspiration at the level of the aortic arch shows no abnormality. (b) CT scan obtained at submaximal expiratory effort shows that the posterior wall of the trachea is slightly flattened (arrow); however, the trachea has not collapsed. (c) CT scan obtained at maximal expiratory effort after additional breathing instructions shows collapse of the trachea (arrows), a finding that confirms the suspected diagnosis.
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Figure 1b. Tracheal collapse in a patient suspected to have tracheomalacia. (a) CT scan obtained at maximal inspiration at the level of the aortic arch shows no abnormality. (b) CT scan obtained at submaximal expiratory effort shows that the posterior wall of the trachea is slightly flattened (arrow); however, the trachea has not collapsed. (c) CT scan obtained at maximal expiratory effort after additional breathing instructions shows collapse of the trachea (arrows), a finding that confirms the suspected diagnosis.
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Figure 1c. Tracheal collapse in a patient suspected to have tracheomalacia. (a) CT scan obtained at maximal inspiration at the level of the aortic arch shows no abnormality. (b) CT scan obtained at submaximal expiratory effort shows that the posterior wall of the trachea is slightly flattened (arrow); however, the trachea has not collapsed. (c) CT scan obtained at maximal expiratory effort after additional breathing instructions shows collapse of the trachea (arrows), a finding that confirms the suspected diagnosis.
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For the small airways, expiratory CT should be performed in suspected bronchiolitis or for suspected airway involvement in systemic disease. With transmural pressure becoming increasingly positive during expiration, pathologic small airways may tend to collapse earlier than normal bronchioles, thereby "trapping" the air distal to the site of collapse. This air trapping is then seen as regional inhomogeneity, with areas that remain relatively lucent (more black) interspersed with areas of normal higher-attenuation lung (2) (Fig 2). Although expiratory maneuvers for large and small airways are similar, CT acquisition is usually performed during forced exhalation for the detection of malacia and at end-expiration for small airways diseases (1).
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Figure 2a. Small airways disease in a patient suspected to have bronchiolitis. (a) CT scan obtained at maximal inspiration at the level of the upper lobes shows the typically rounded trachea (solid arrow) and subtle areas of low attenuation (open arrows). (b) CT scan obtained at maximal expiration shows typical inward bulging of the posterior tracheal wall (solid arrow) and extensive areas of air trapping (open arrows), findings that confirm the diagnosis of small airways disease.
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Figure 2b. Small airways disease in a patient suspected to have bronchiolitis. (a) CT scan obtained at maximal inspiration at the level of the upper lobes shows the typically rounded trachea (solid arrow) and subtle areas of low attenuation (open arrows). (b) CT scan obtained at maximal expiration shows typical inward bulging of the posterior tracheal wall (solid arrow) and extensive areas of air trapping (open arrows), findings that confirm the diagnosis of small airways disease.
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Beyond diseases of the larger airways and bronchiolitis, adequate respiratory maneuvers are of particular importance in the CT imaging of patients with asthma (3) and emphysema (4), and for both diseases the direct influence of the respiratory status on imaging findings has been shown (3,4). Other studies in the field of chronic obstructive lung diseases have focused on the potential to correct for an inadequate respiratory status during CT examinations (5,6).
In oncologic CT imaging, the diameters, the volume, and the appearance of tumors and nodules do not depend only on section thickness (7) and CT acquisition parameters (8). Indeed, Petkovska et al (9) showed that the volume of pulmonary nodules could vary substantially with different levels of inspiration. These authors also showed that the nodule volumes changed nonuniformly with changes in lung volumes: some nodules were larger at high lung volumes, whereas others were larger at small lung volumes. Finally, the authors found that there was no statistically significant relation between the nodule size and the amount of variation with lung volume (9). Overall, these findings emphasize the importance of sufficient and reproducible respiratory maneuvers in serial thoracic CT examinations, notably in oncologic patients (Figs 3–6).
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Figure 3a. Solitary pulmonary nodule. CT scans obtained at inspiration (a) and expiration (b) show a solitary pulmonary nodule in the right upper lobe. The nodule changes in both size and morphology between inspiration and expiration, measuring 10.9 x 9.3 mm at inspiration (a) and 12.3 x 12.2 mm at expiration (b). Note the difference in the shape of the trachea between inspiration and expiration. (Courtesy of Pierre Alain Gevenois, MD, PhD, Erasmus Hospital, University of Brussels, Belgium.)
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Figure 3b. Solitary pulmonary nodule. CT scans obtained at inspiration (a) and expiration (b) show a solitary pulmonary nodule in the right upper lobe. The nodule changes in both size and morphology between inspiration and expiration, measuring 10.9 x 9.3 mm at inspiration (a) and 12.3 x 12.2 mm at expiration (b). Note the difference in the shape of the trachea between inspiration and expiration. (Courtesy of Pierre Alain Gevenois, MD, PhD, Erasmus Hospital, University of Brussels, Belgium.)
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Figure 4a. Pulmonary nodule in a patient suspected to have peripheral lung carcinoma. CT scans obtained at suboptimal (a) and optimal (b) inspiration show a pulmonary nodule in the right lower lobe. The nodule changes in size and morphology between suboptimal and optimal inspiration, measuring 11.6 x 15.2 mm at suboptimal inspiration (a) and 15.5 x 10.1 mm at optimal inspiration (b).
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Figure 4b. Pulmonary nodule in a patient suspected to have peripheral lung carcinoma. CT scans obtained at suboptimal (a) and optimal (b) inspiration show a pulmonary nodule in the right lower lobe. The nodule changes in size and morphology between suboptimal and optimal inspiration, measuring 11.6 x 15.2 mm at suboptimal inspiration (a) and 15.5 x 10.1 mm at optimal inspiration (b).
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Figure 5a. Pulmonary nodules in a patient with suspected metastases. (a) CT scan obtained at suboptimal inspiration shows nodules in the right upper lobe. Image is blurred, and differentiation between nodules is not possible. (b) On a scan obtained at optimal inspiration, individual nodules can be better differentiated.
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Figure 5b. Pulmonary nodules in a patient with suspected metastases. (a) CT scan obtained at suboptimal inspiration shows nodules in the right upper lobe. Image is blurred, and differentiation between nodules is not possible. (b) On a scan obtained at optimal inspiration, individual nodules can be better differentiated.
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Figure 6a. Pseudonodules in a patient who underwent lung transplantation. (a) CT scan obtained at suboptimal inspiration shows two large pseudonodules in the left major fissure. (b) On a CT scan obtained at optimal inspiration, the nodules have disappeared; only minimal thickening of the fissure is seen.
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Figure 6b. Pseudonodules in a patient who underwent lung transplantation. (a) CT scan obtained at suboptimal inspiration shows two large pseudonodules in the left major fissure. (b) On a CT scan obtained at optimal inspiration, the nodules have disappeared; only minimal thickening of the fissure is seen.
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Inadequate inspiratory and expiratory maneuvers can influence differences in lung attenuation and lead to misinterpretation by either increasing attenuation to simulate disease in normal patients (Figs 7–10) or by decreasing attenuation to simulate normal contrast in diseased patients (Figs 11, 12). Moreover, inadequate inspiratory and expiratory maneuvers can create motion artifacts that compromise image interpretation even further (Fig 7c, 7d) (10–14).
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Figure 7a. Subtle subpleural linear opacity in a patient with dysphagia. Axial CT scans through the lung bases (a, b) and coronal reformatted images of the dorsal lungs (c, d) were obtained. (a, c) Initial images show typical features of submaximal inspiratory effort, including dependent opacities (black solid arrows in a), crowding of vessels (open arrows in a), and motion artifacts at the lung bases (arrows in c). (b, d) On images obtained after additional breathing instructions, image quality is substantially improved and signs of submaximal inspiratory effort have disappeared. The subtle subpleural linear opacity (white solid arrow in a and b) is better seen after additional breathing instructions. Also note the difference in lung volume between submaximal (c) and maximal (d) inspiratory effort, as demonstrated by the increased apicobasal distance in d.
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Figure 7b. Subtle subpleural linear opacity in a patient with dysphagia. Axial CT scans through the lung bases (a, b) and coronal reformatted images of the dorsal lungs (c, d) were obtained. (a, c) Initial images show typical features of submaximal inspiratory effort, including dependent opacities (black solid arrows in a), crowding of vessels (open arrows in a), and motion artifacts at the lung bases (arrows in c). (b, d) On images obtained after additional breathing instructions, image quality is substantially improved and signs of submaximal inspiratory effort have disappeared. The subtle subpleural linear opacity (white solid arrow in a and b) is better seen after additional breathing instructions. Also note the difference in lung volume between submaximal (c) and maximal (d) inspiratory effort, as demonstrated by the increased apicobasal distance in d.
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Figure 7c. Subtle subpleural linear opacity in a patient with dysphagia. Axial CT scans through the lung bases (a, b) and coronal reformatted images of the dorsal lungs (c, d) were obtained. (a, c) Initial images show typical features of submaximal inspiratory effort, including dependent opacities (black solid arrows in a), crowding of vessels (open arrows in a), and motion artifacts at the lung bases (arrows in c). (b, d) On images obtained after additional breathing instructions, image quality is substantially improved and signs of submaximal inspiratory effort have disappeared. The subtle subpleural linear opacity (white solid arrow in a and b) is better seen after additional breathing instructions. Also note the difference in lung volume between submaximal (c) and maximal (d) inspiratory effort, as demonstrated by the increased apicobasal distance in d.
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Figure 7d. Subtle subpleural linear opacity in a patient with dysphagia. Axial CT scans through the lung bases (a, b) and coronal reformatted images of the dorsal lungs (c, d) were obtained. (a, c) Initial images show typical features of submaximal inspiratory effort, including dependent opacities (black solid arrows in a), crowding of vessels (open arrows in a), and motion artifacts at the lung bases (arrows in c). (b, d) On images obtained after additional breathing instructions, image quality is substantially improved and signs of submaximal inspiratory effort have disappeared. The subtle subpleural linear opacity (white solid arrow in a and b) is better seen after additional breathing instructions. Also note the difference in lung volume between submaximal (c) and maximal (d) inspiratory effort, as demonstrated by the increased apicobasal distance in d.
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Figure 8a. Apparent abnormalities in a patient with chronic obstructive pulmonary disease who was suspected to have pneumonia. (a) Initial CT scan obtained at submaximal inspiratory effort at the level of the lung bases shows subtle bilateral opacities in the lower lobes (arrows). (b) On a CT scan obtained after additional breathing instructions, the middle lobe and the lingula are better inflated (white arrowheads), the azygoesophageal recess is deployed (curved arrow), the intersegmental septum has become visible (small straight arrow), and the previously seen opacities have partially disappeared (large straight arrows).
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Figure 8b. Apparent abnormalities in a patient with chronic obstructive pulmonary disease who was suspected to have pneumonia. (a) Initial CT scan obtained at submaximal inspiratory effort at the level of the lung bases shows subtle bilateral opacities in the lower lobes (arrows). (b) On a CT scan obtained after additional breathing instructions, the middle lobe and the lingula are better inflated (white arrowheads), the azygoesophageal recess is deployed (curved arrow), the intersegmental septum has become visible (small straight arrow), and the previously seen opacities have partially disappeared (large straight arrows).
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Figure 9a. Apparent abnormalities in a patient with parenchymal scars who was suspected to have pneumonia. CT scans through the right (a, b) and left (c, d) lung bases were obtained. The initial images (a, c) show the typical effects of submaximal inspiratory effort. On the images obtained at maximal inspiratory effort after additional breathing instructions (b, d), overall lung attenuation is decreased. (a, b) In the right lung, between submaximal (a) and maximal (b) inspiration, the courses of vessels become stretched (white arrow), the azygoesophageal recess unfolds (curved arrow), pre-existing ground-glass opacities in the recess disappear (straight black arrow), and the extent of subtle parenchymal opacities in the right lower lobe is substantially reduced (arrowhead). (c, d) In the left lung, between submaximal (c) and maximal (d) inspiration, vessels become thinner (large white arrow) and stretched (small white arrow), the orientation of the interlobar fissure becomes straighter (black arrow), and the paraaortic lung region is deployed more (black arrowhead). Subtle interstitial opacities that could be mistaken for true abnormalities at submaximal inspiration disappear (white arrowhead).
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Figure 9b. Apparent abnormalities in a patient with parenchymal scars who was suspected to have pneumonia. CT scans through the right (a, b) and left (c, d) lung bases were obtained. The initial images (a, c) show the typical effects of sub-maximal inspiratory effort. On the images obtained at maximal inspiratory effort after additional breathing instructions (b, d), overall lung attenuation is decreased. (a, b) In the right lung, between submaximal (a) and maximal (b) inspiration, the courses of vessels become stretched (white arrow), the azygoesophageal recess unfolds (curved arrow), pre-existing ground-glass opacities in the recess disappear (straight black arrow), and the extent of subtle parenchymal opacities in the right lower lobe is substantially reduced (arrowhead). (c, d) In the left lung, between submaximal (c) and maximal (d) inspiration, vessels become thinner (large white arrow) and stretched (small white arrow), the orientation of the interlobar fissure becomes straighter (black arrow), and the paraaortic lung region is deployed more (black arrowhead). Subtle interstitial opacities that could be mistaken for true abnormalities at submaximal inspiration disappear (white arrowhead).
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Figure 9c. Apparent abnormalities in a patient with parenchymal scars who was suspected to have pneumonia. CT scans through the right (a, b) and left (c, d) lung bases were obtained. The initial images (a, c) show the typical effects of sub-maximal inspiratory effort. On the images obtained at maximal inspiratory effort after additional breathing instructions (b, d), overall lung attenuation is decreased. (a, b) In the right lung, between submaximal (a) and maximal (b) inspiration, the courses of vessels become stretched (white arrow), the azygoesophageal recess unfolds (curved arrow), pre-existing ground-glass opacities in the recess disappear (straight black arrow), and the extent of subtle parenchymal opacities in the right lower lobe is substantially reduced (arrowhead). (c, d) In the left lung, between submaximal (c) and maximal (d) inspiration, vessels become thinner (large white arrow) and stretched (small white arrow), the orientation of the interlobar fissure becomes straighter (black arrow), and the paraaortic lung region is deployed more (black arrowhead). Subtle interstitial opacities that could be mistaken for true abnormalities at submaximal inspiration disappear (white arrowhead).
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Figure 9d. Apparent abnormalities in a patient with parenchymal scars who was suspected to have pneumonia. CT scans through the right (a, b) and left (c, d) lung bases were obtained. The initial images (a, c) show the typical effects of sub-maximal inspiratory effort. On the images obtained at maximal inspiratory effort after additional breathing instructions (b, d), overall lung attenuation is decreased. (a, b) In the right lung, between submaximal (a) and maximal (b) inspiration, the courses of vessels become stretched (white arrow), the azygoesophageal recess unfolds (curved arrow), pre-existing ground-glass opacities in the recess disappear (straight black arrow), and the extent of subtle parenchymal opacities in the right lower lobe is substantially reduced (arrowhead). (c, d) In the left lung, between submaximal (c) and maximal (d) inspiration, vessels become thinner (large white arrow) and stretched (small white arrow), the orientation of the interlobar fissure becomes straighter (black arrow), and the paraaortic lung region is deployed more (black arrowhead). Subtle interstitial opacities that could be mistaken for true abnormalities at submaximal inspiration disappear (white arrowhead).
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Figure 10a. Apparent abnormality in a patient who was screened for smoking-related lung diseases. (a) CT scan obtained at inspiration shows a ground-glass nodule in the left lower lobe (open arrow). However, incomplete distention of the azygoesophageal recess (solid arrow) suggests submaximal inspiratory effort. (b) On a CT scan obtained at maximal inspiration after additional breathing instructions, the azygoesophageal recess and retrohilar lung are normally expanded (arrows) and the ground-glass nodule has disappeared.
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Figure 10b. Apparent abnormality in a patient who was screened for smoking-related lung diseases. (a) CT scan obtained at inspiration shows a ground-glass nodule in the left lower lobe (open arrow). However, incomplete distention of the azygoesophageal recess (solid arrow) suggests submaximal inspiratory effort. (b) On a CT scan obtained at maximal inspiration after additional breathing instructions, the azygoesophageal recess and retrohilar lung are normally expanded (arrows) and the ground-glass nodule has disappeared.
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Figure 11a. Air trapping in a patient suspected to have small airways disease. (a) CT scan obtained at maximal inspiration at the level of the left atrium shows no abnormality. (b) On a CT scan obtained at submaximal expiratory effort, the bronchi are unchanged in diameter (arrows) and no air trapping is seen. (c) On a CT scan obtained at maximal expiratory effort after additional breathing instructions, bronchial diameters are decreased (solid arrows) and extensive air trapping is apparent (open arrows).
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Figure 11b. Air trapping in a patient suspected to have small airways disease. (a) CT scan obtained at maximal inspiration at the level of the left atrium shows no abnormality. (b) On a CT scan obtained at submaximal expiratory effort, the bronchi are unchanged in diameter (arrows) and no air trapping is seen. (c) On a CT scan obtained at maximal expiratory effort after additional breathing instructions, bronchial diameters are decreased (solid arrows) and extensive air trapping is apparent (open arrows).
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Figure 11c. Air trapping in a patient suspected to have small airways disease. (a) CT scan obtained at maximal inspiration at the level of the left atrium shows no abnormality. (b) On a CT scan obtained at submaximal expiratory effort, the bronchi are unchanged in diameter (arrows) and no air trapping is seen. (c) On a CT scan obtained at maximal expiratory effort after additional breathing instructions, bronchial diameters are decreased (solid arrows) and extensive air trapping is apparent (open arrows).
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Figure 12a. Air trapping after aspiration of a fish bone. (a) CT scan obtained at maximal inspiration at the level of the left atrium shows the fish bone (arrow) in the right lower lobe bronchus. (b) On a CT scan obtained at submaximal expiratory effort, the bronchial diameter is decreased (arrow) but no typical increase in lung attenuation and no air trapping are seen. (c) On a CT scan obtained at maximal expiratory effort after additional breathing instructions, the fish bone (curved arrow) has become occlusive (straight black arrow) and causes air trapping in the entire right lower lobe (straight white arrows).
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Figure 12b. Air trapping after aspiration of a fish bone. (a) CT scan obtained at maximal inspiration at the level of the left atrium shows the fish bone (arrow) in the right lower lobe bronchus. (b) On a CT scan obtained at submaximal expiratory effort, the bronchial diameter is decreased (arrow) but no typical increase in lung attenuation and no air trapping are seen. (c) On a CT scan obtained at maximal expiratory effort after additional breathing instructions, the fish bone (curved arrow) has become occlusive (straight black arrow) and causes air trapping in the entire right lower lobe (straight white arrows).
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Figure 12c. Air trapping after aspiration of a fish bone. (a) CT scan obtained at maximal inspiration at the level of the left atrium shows the fish bone (arrow) in the right lower lobe bronchus. (b) On a CT scan obtained at submaximal expiratory effort, the bronchial diameter is decreased (arrow) but no typical increase in lung attenuation and no air trapping are seen. (c) On a CT scan obtained at maximal expiratory effort after additional breathing instructions, the fish bone (curved arrow) has become occlusive (straight black arrow) and causes air trapping in the entire right lower lobe (straight white arrows).
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Despite the importance of respiratory maneuvers, the radiology literature yields little information on how patients should be instructed to perform them. Most of the available literature comes from pulmonary function testing (15–21), but its applicability to the radiologic context is limited. Therefore, we have devised respiratory instructions dedicated specifically within the context of thoracic CT examinations and formatted them as 10 individual instructions. The aim of these instructions is to provide a hands-on guide for both radiologists and technologists to optimize the respiratory instructions given to their patients and thereby improve the quality of thoracic CT examinations.
1. Be Simple and Figurative
Although a CT examination of the thorax might seem routine to a radiologist or technologist, it is an unusual and potentially alienating experience for most patients. Use brief, simple, and figurative sentences to explain the procedures. A sample is given in Table 1. This is a general guideline aimed to serve as a framework for more individualized phrasing that reflects your bedside manner, the practice setting, and patient characteristics such as personality, physical status, and cognitive capacity.
However, the sample contains five critical elements of information that should be included in any personalized instruction: (a) Explain what will happen, (b) explain why patient cooperation is important, (c) explain the precise maneuvers the patient is expected to perform, (d) reassure that instructions do not have to be memorized and that coaching will be available throughout the entire examination, and (e) encourage patient questions and feedback. In our experience, the inclusion of these five elements increases the potential for a CT examination with diagnostic results.
2. Train the Patient with Attention
A quiet training area will allow the patient to develop a relationship with the technologist or radiologist in an undistracted atmosphere. For continuity, the same person should train the patient and also give breathing instructions during the CT examination. Also, breathing instructions should be performed in the same body position as the CT examination, that is, supine and with the arms extended behind the head. Ideally, training should be performed with the patient positioned on the CT table. If this is not possible, the patient may be positioned on a bed next to the CT suite. Training in the correct position, usually supine, is important in order to accurately simulate the experience in the CT scanner.
Begin by observing several normal breaths to become familiar with the patient’s breathing rhythm and to visualize the abdominal excursions you will later monitor during the CT examination. Instruct the patient to stay as motionless as possible during the training and the CT examination. Some patients distort their body position to maximize respiratory efforts. Such movement will impair image quality and make subsequent comparison of paired inspiratory and expiratory images less precise.
3. Let the Patient Cough
Rapid distentions of the upper airways by deep inspiration often trigger a cough (22). Coughing during CT data acquisition will compromise image quality because of motion artifacts and may necessitate repeat scanning. Before you start training the patient to perform the respiratory maneuvers, encourage the patient to take deep breaths and cough. If voluntary coughing is not possible, ask the patient to make a few rapid deep inspirations in a "staccato" manner. Remember to have tissues or a disposable cup handy in case the cough is productive. After a few voluntary coughs, patients are less likely to cough reflexly during the CT study. An added benefit of this voluntary cough maneuver may be clearance of secretions that could otherwise mimic endobronchial lesions.
4. Be Proactive and Demonstrate
The technologist or radiologist should first demonstrate the breathing maneuver. Do not worry about overacting: exaggeration will give the patient a sense for how much effort is required. Too often patients provide submaximal efforts because they do not understand what is needed. Many patients are not properly instructed or never see a demonstration on how maneuvers are supposed to be performed.
Observe the patient’s use of accessory muscles of respiration and other indicators, like facial expressions, to have a sense of how much effort the patient puts into the maneuver. Accompany the patient to the very end of each maneuver. It is important to continue instructing the patient until the very end of both inspiration and expiration, as patients tend to be less "full" or less "empty" of air than they actually feel they are. When the initial training is completed, praise the patient’s performance but also provide constructive feedback to reinforce the patient’s effort (Table 2).
5. "Pull It!"—the Inspiratory Maneuver
After a few normal breaths, instruct the patient to maximally breathe in. A detailed suggestion for the inspiratory breathing instruction is given in Table 3. Alert the patient of the inspiratory maneuver that will follow while he or she is still breathing normally. It can help to let the patient breathe out hard before taking a deep breath in. Tell the patient to think of the lungs as a big balloon that needs to be filled as much as possible. Encourage the patient with sustained and repeated commands (see Table 3). Start the acquisition of CT data as soon as possible because many patients find it difficult to sustain a prolonged inspiration and may passively "leak" a portion of their air before or during the CT data acquisition.
At end inspiration, when instructed to "hold it," many patients will involuntarily perform a Valsalva maneuver, believing that this will help them to "keep the air in their lungs." Because this involuntary Valsalva maneuver is associated with effort and raises intrathoracic pressure, it can compromise image quality by both introducing motion artifacts and delaying the inflow of contrast material. At the end of inspiration, patients should therefore be instructed to "relax," if possible against the open glottis. Tell the patient to relax, but "without pressing."
A simple method to monitor for a potential Valsalva maneuver is to observe the abdomen. If at the end of inspiration, the contour of the abdomen stays unchanged, a Valsalva maneuver is unlikely. If at the end of inspiration, the contour of the abdomen bulges outward, a Valsalva maneuver is very likely. As soon as data acquisition is completed, instruct the patient to resume normal breathing again.
6. Rest Period
In untrained patients, maximum breathing maneuvers can be tiring. Therefore, you should give patients an opportunity to rest between maneuvers. The pauses do not have to be long; a few normal breaths will usually suffice. In our experience, frequent short pauses are more effective than one long pause. Remember to pause when the patient asks, when you think the patient needs to rest, or when you note a decrease in performance despite sustained patient effort. A pause is imperative when the patient feels "dizzy," that is, at risk of syncope (16).
7. "Push It!"—the Expiratory Maneuver
After a few normal breaths, instruct the patient to maximally breathe out. A detailed suggestion for the expiratory breathing command is given in Table 4. Alert the patient of the upcoming expiratory maneuver while he or she is still breathing normally. It sometimes helps to have the patient take a deep breath in before maximally breathing out. You may tell your patient to think of the lungs as a nearly empty bottle of ketchup, heavily squeezed to get the very last drop.
When instructed to "blow out," some patients tend to purse their lips, as if they are preparing to blow out a candle. This gives them the false impression of performing a maximal expiratory effort due to the increased resistance of air flow, that is, the pursed lips. However, this artificial obstruction only serves to slow down the emptying of their lungs. For patients who have difficulty avoiding pursed lips despite appropriate instructions, this behavior can be prevented by using disposable pulmonary function testing mouthpieces.
Help the patient to "empty the lungs" by sustained and repeated commands (see Table 4). Start data acquisition as soon as the patient is at maximal expiration because it is difficult to sustain a prolonged expiration and patients will tend to inspire small portions of air before or during the CT acquisition. Give the patient enough time for a complete expiration. The time required for such a complete expiration is often underestimated (15). The expiratory maneuver should last at least 6 seconds, and patients with airway obstruction might require even more time before the maneuver is completed. Therefore, it is particularly important to motivate the patient at the end of the expiratory effort. As described in the section on inspiratory breathing, try to prevent the patient from performing a Valsalva maneuver. As soon as data acquisition is completed, instruct the patient to resume normal breathing.
8. Do Not Use Automatic Patient-Instruction Devices
Automatic patient-instruction devices are part of the software on most modern CT scanners. These devices use automatically generated, digitally recorded voice commands that can be selectively defined for different scanning protocols, most often in various languages. The devices are meant to provide an optional alternative to communication by means of intercom devices between the radiology personnel at the console and the patient in the gantry.
Although the convenience of these devices may be appealing, it has been shown that use of automatic patient instruction results in substantially decreased image quality and a substantially increased proportion of CT acquisitions that have to be repeated (23). Automatic patient instruction also dehumanizes the scanning experience for the patient and prevents the opportunity for two-way communication between the patient and the technologist. The only setting in which use of automatic patient instruction could conceivably be acceptable is the case of a patient unfamiliar with the local language and with no interpreter available. We nevertheless emphasize that a translator is strongly preferable to automatic patient instruction for foreign-language speaking patients.
9. Document the Patient’s Performance
The quality of the patient’s inspiratory and expiratory maneuvers during the CT acquisition should be documented. This can be done in a dedicated text field on the electronic requisition, the technical note sheet, or the radiologic report. Whereas the documentation of adequate respiratory maneuvers can potentially be seen as less important than other parameters such as the amount of contrast material administered or the dose of the scan, the documentation of insufficient maneuvers should be mandatory, particularly if the reporting radiologist is not present during the CT examination. Documentation of insufficient maneuvers is diagnostically important information that will help the reporting radiologist understand potential alterations on the images and avoid misinterpretation. Documentation of the quality of the patient’s respiratory maneuvers can thus have a direct influence on the quality of the radiologic report.
10. Be Around and Monitor Quality
Optimizing breathing instruction often requires a change in long-standing habits. This is achieved more successfully by moderate and continuous endeavors than by one big push. In the current high-volume era of radiology practice, few radiologists are available to individually instruct patients for CT examinations, and in most instances technologists have assumed this task. The radiologist is nevertheless responsible for training technologists in how to provide instructions for respiratory maneuvers and for monitoring compliance with respiratory instruction procedures.
Therefore, radiologists should strive to be visible to technologists and patients and to monitor the daily work at the scanner console with interest and attention. Radiologists should also explain to other members of the health care team (technologists, nurses, translators, and referring clinicians) why breathing instructions are important. This task is best accomplished by showing examples of how optimal and suboptimal respiratory maneuvers have positively and negatively influenced scan quality, respectively. Give suggestions for improvement in a balanced and supportive manner.
In our department, we have initiated training sessions for our CT technologists given by both a chest radiologist and an expert in pulmonary function testing. These sessions are part of our department-wide quality assurance and continuing education program aimed to familiarize technologists with a hands-on technique for teaching patients proper breathing instructions. After the sessions, our technologists have reported feeling "empowered" by their new knowledge of how to appropriately coach patients in breathing maneuvers and how to recognize whether scans have been obtained at optimal levels of inspiration and expiration. We have also made the effect of these training sessions on CT image quality a topic of our research and quality assurance measures.
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Conclusions
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Inadequate respiratory maneuvers can effect differences in lung attenuation on thoracic CT images and lead to misinterpretation by increasing attenuation to simulate disease in normal patients, decreasing attenuation to simulate normal contrast in patients with disease, or creating motion artifacts. Therefore, we devised respiratory instructions specifically for thoracic CT examinations. This hands-on guide for both radiologists and technologists aims to optimize the respiratory instructions given to patients and thereby improve the quality of thoracic CT examinations.
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Acknowledgments
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We thank Donna Wolfe for the careful revision of the manuscript.
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Abstract
Introduction
