TMC Practice Exam

1. You notice over a 2-hour period, the plateau pressure of a patient receiving volume controlled ventilation has remained stable, but her peak pressure has steadily increased. Which of the following is most likely the reason for this observation?

2. While auscultating a patient’s lungs, you hear bronchial breath sounds over the left lower lobe area. This would indicate which of the following?

3. A 43-year-old 52 kg patient is admitted to the emergency room after overdosing on heroin. The patient is unconscious and is making minimal respiratory efforts. ABG results on a nonrebreathing mask @ 12 L/min are as follows:
pH 7.28
PCO2 74 torr
HCO3 20 mEq/L
PaO2 315 torr
You should you recommend?

4. You are called to help a nurse in ICU measure a patient’s central venous pressure (CVP) with a strain-gauge pressure transducer. The pressure transducer appears to be positioned well above the middle of the patient’s lateral chest wall. What effect if any would this have on the measurement?

5. Before giving an aerosol treatment, you see a note in the chart that states your patient had pink frothy secretions on admission to the emergency department. This is most likely indicates which of the following:

6. After obtaining a medication history from a patient admitted for asthma, which of the following information would you consider least important?

7. A 54 year-old patient is on a ventilator in the volume control mode. After you perform endotracheal suctioning, which of the following would indicate effective clearance of retained secretions?

8. While establishing initial ventilatory support settings for a new patient, the most important consideration is the:

9. For patients with suspected pulmonary thromboembolism whose ordinary X-rays are negative, which of the following procedures can best help establish the diagnosis?

10. Bedside spirometry performed on a patient reveals the following: Respiratory rate = 21, Tidal volume = 350 mL, Dead space = 155 mL, Vital capacity = 1.0 L. Based on this data, what is the patient’s minute ventilation?

11. Defibrillation should be done immediately in which of the following patient situations?

12. Your patient has a large pneumothorax and also displays hypotension. What is most likely the cause of this finding?

13. A patient with asthma is in acute respiratory distress and presents to the emergency room with diminished breath sounds. After bronchodilator therapy, auscultation of the chest reveals rhonchi and wheezing. This change suggests which of the following?

14. During capnography monitoring of a mechanically ventilated patient, you note that the end-tidal PCO2 (PetCO2) has dropped to 0 mm Hg. This finding may indicate:

15. You are monitoring a mechanically ventilated patient 36 hours post-craniotomy who has an ICP of 20 mmHg but is otherwise stable. The latest ABG results are as follows:
pH 7.39
PaCO2 43 mm Hg
HCO3 24 mEq/L
BE 0
PaO2 88 mm Hg
SaO2 95%
Based on this information, which of the following is the most acceptable action?

16. A patient with a 9-year history of chronic bronchitis and an acute pneumonia exhibits the following ABG results on room air:

pH = 7.21, PCO2 = 64 torr, HCO3 = 25 mEq/L, PO2 = 39 torr, P(A-a)O2 = 41 torr

Which of the following best describes this patient’s condition?

17. The physician calls you over to examine the ABG results of a 52 kg female patient who is receiving volume control A/C ventilation. Currently the patient has a tidal volume of 400 mL, rate of 10/min, and 35% O2. Her blood gas results are as follows:
pH 7.31
PaCO2 49 torr
HCO3 24 mEq/L
BE -2 mEq/L
PaO2 74 torr
SaO2 95%
Based on these values, which of the following changes is appropriate?

18. Which of the following is a prerequisite for discharging a ventilator-dependent patient to the homecare setting?

19. The Respiratory Therapist is called to evaluate a home patient with a nasal CPAP mask for treatment of obstructive sleep apnea. The patient’s wife states that he has been snoring more loudly lately and having periods of apnea. You confirm this after observing the patient’s sleeping and breathing patterns for 2 hours. What would be your first course of action to try to correct the problem?

20. While inspecting an elderly female patient, you note that she has an abnormal anteroposterior (AP) curvature of the spine. This best describes which of the following?

21. Which of the following would you recommend to provide graphic data useful in evaluating the ventilator-patient interface?

22. Which of the following conditions would a ventilation scan appear normal but a perfusion scan reveal areas of absent blood flow?

23. If noted on inspiration, which of the following respiratory signs of an adult patient would be considered abnormal?

24. What is the approximate duration of flow of an oxygen E-cylinder at 1000 psi running at 4 L/min?

25. Your patient who is being mechanically ventilated has thick, mucoid secretions. It is determined that the wick humidifier is producing insufficient humidity. In this case, which of the follow should you do?

26. A physician wants your recommendation on how to monitor the cardiopulmonary status of a patient that is undergoing a bronchoscopy procedure with moderate sedation. You would recommend which of the following:

27. A physician orders a blind bronchoalveolar lavage procedure for a patient in intensive care unit. What is the most likely potential diagnosis that the doctor is trying to confirm with this procedure?

28. A male patient has a lower than normal mixed venous O2 content. Which of the following is the most likely cause of this condition?

29. A patient is being ventilated in the volume-control mode when suddenly the high pressure alarm begins to sound. Which of the following actions would likely correct this problem?

30. You are called to obtain a bedside vital capacity (VC) of 450 ml on a 122 lb female patient receiving ventilatory support in the CMV mode. Which of the following can you draw from this finding?

31. For your patient receiving volume control AC ventilation, you observe a flow-volume loop with a sawtooth pattern on exhalation. Which of the following actions would you consider most appropriate?

32. Which of the following PFT findings are common in patients with chronic bronchitis and also found in those with emphysema?

33. Which of the following are acceptable changes in a patient’s status during a spontaneous breathing trial for weaning from mechanical ventilation?

34. Which of the following is an advantage of SIMV over assist/control ventilation?

35. A 1-year-old child is admitted to the Emergency Department with severe asthmatic symptoms. The doctor orders a bronchodilator that is available in solution and MDI preparations. Which of the following would be the best delivery system for this drug to this patient?

36. After review a patient’s chart, you note that an admission diagnosis of fluid depletion/dehydration. Which of the following findings would be most likely on bedside assessment of this patient?

37. A normal 5-foot 4-inch tall staff member serves as a biologic control for the PFT lab. Her established FVC is 3.81 L with a SD of ±0.13 L. During quality control testing of a spirometer, she produces the following FVC results: FVC #1 = 3.73 L, FVC #2 = 3.88 L, FVC #3 = 3.71 L. You should conclude that the

38. You are called to evaluate a patient’s breathing pattern. You see that the patient’s tidal volumes go from small to large to small and then stop for 10 seconds before starting again and it repeats itself. Which of the following would best describe this breathing pattern?

39. Which of the following should be asked in order to help determine if a patient has orthopnea?

40. Simple spirometry can be used to measure any of the following except:

41. You obtain an expired carbon monoxide (CO) reading of 18 ppm on a COPD patient participating in a pulmonary rehabilitation program. Based on this finding, you can conclude that the patient:

42. A trauma patient has been receiving volume controlled SIMV via an endotracheal tube for the past three days. The attending surgeon anticipates that the patient will likely be on the ventilator for another 4 to 5 days. Which of the following actions would you recommend?

43. In assessing a new admission to the Intensive Care Unit, you note a spontaneous respiratory rate of 37/minute. The most likely cause of this observation is:

44. To provide long-term positive pressure ventilation, a cuffed artificial airway is needed in order to:

45. A patient presents to the emergency room with a depressed level of consciousness and is severely agitated. Which of the following approaches can be used to obtain their medication history?

46. Which of the following would you recommend to help guide a physician in locating the appropriate needle insertion site for thoracentesis performed at the bedside?

47. While performing a routine ventilator check on a patient receiving volume controlled ventilation, you note that the peak airway pressure has decreased from a prior value of 52 cm H2O to 32 cm H2O. There have been no changes to the ventilator settings. Which of the following actions would be appropriate at this time?

48. A patient’s ABG shows respiratory alkalosis. Which of the following problems is most likely?

49. What type of laryngoscope blade would you select when performing an emergency intubation on an infant?

50. Which of the following ventilator graphics displays is the best choice to assess the work of breathing associated with patient triggering?

51. You are called to check on a patient receiving volume controlled A/C ventilation. You note that both the low tidal volume and high pressure limit alarms are sounding on each inspiration. You first action should be which of the following?

52. Which of the following modes of ventilatory support is indicated when a precise I:E ratio must be maintained?

53. While examining a patient, you notice that the patient has greatly diminished breath sounds in the right lower lobe and the trachea has shifted to the right. These signs indicate which of the following conditions?

54. A patient in intensive care unit suddenly start to deteriorate. The attending physician wants to rule out an acute pulmonary embolism as the cause. Which of the following laboratory tests would you recommend?

55. While using a Yankauer device to suction an adult patient, you are unable to remove thick secretions. The regulator attached to the oropharyngeal suctioning device displays a reading of -70 mm Hg. Which of the following actions should you take at this time?

56. What is the primary reason for selecting a high flow nasal cannula system for a patient?

57. Of the following patients undergoing a cardiopulmonary exercise test, for which would you recommend extra precautions?

58. You would need which of the following equipment in order to calibrate a portable bedside spirometer?

59. While analyzing an ABG sample you obtained from a patient breathing room air, you obtain the following values:
pH 7.44
PaCO2 46 torr
PaO2 163 torr
The patient’s blood gas results should be:

60. While educating a 31-year-old patient with asthma, you explain to her how to recognize and respond to episodes of worsening symptoms. To confirm her understanding of this information you should ask:

61. For testing purposes, you instruct a patient to take a deep breath and then exhale as quickly as possible. You then observe the recording of the fastest air movement. Which of the following tests is being measured?

62. Which of the following selections in a patient’s medical history would be least important to consider in evaluating their pulmonary condition?

63. If you were to instruct a patient to take a maximum deep breath and then exhale completely, which maneuver is being measured?

64. A patient’s bedside spirometry results are as follows: FVC decreased, FEV1 normal, FEV1% increased. What is the most likely problem?

65. A 58-year-old postoperative male who weighs 78 kg (172 lb) is receiving volume control A/C ventilation at a rate of 14/min with a tidal volume of 650 mL and an FIO2 of 0.4. Results of arterial blood gas analysis are as follows:
pH 7.51
PaCO2 30 torr
HCO3 23 mEq/L
BE -1
PaO2 117 torr
SaO2 99%
Based on this information, you should recommend which of the following?

66. Before intubation in an emergency situation, injection of air into the pilot line fails to inflate the cuff. Which of the following should you do?

67. A large volume jet nebulizer is operating on 70% oxygen at 12 L/min. You note that the aerosol being delivered is in short rapid puffs and also observe a gurgling sound in the system. Which of the following actions would be most appropriate?

68. While performing posterior thoracic palpation of an adult, you note minimal right-side diaphragmatic movement as the patient takes a deep breath. His left-sided movement is normal. Which of the following conditions would best explain this finding?

69. A ventilator that is being used in the assist/control mode will trigger on in response to which of the following?

70. For a patient receiving positive-pressure ventilation, you should strive to keep the alveolar (plateau) airway pressure below which of the following?

71. A bubble humidifier is not bubbling during oxygen therapy, despite the flowmeter set and running at 5 L/min. Which of the following should you check?

72. A patient is stabilized with adequate oxygenation and ventilation on volume control ventilation (VC) with the following settings: rate = 15/min, tidal volume = 550 mL, peak inspiratory pressure (PIP) = 45 cm H2O, plateau pressure = 30 H2O and PEEP = 10 cm H2O. The doctor orders a changeover to pressure control ventilation (PC). Which of the following settings would you initially use to implement PC in this patient?

73. While feeling a patient’s radial pulse, you note that the pulse feels bounding and full. Which of the following conditions would likely be the cause of this finding?

74. A patient with a normal cardiac output and PaO2 is exhibiting signs and symptoms of tissue hypoxia. Which of the following is the most likely cause?

75. After reviewing the patient’s chart, you note that results of a chest x-ray show: “Complete opacification of the left chest with a shift of the trachea and mediastinum to the left.” These findings are most likely to indicate which of the following?

76. Atelectasis has been diagnosed via a chest x-ray on an unconscious patient who had a recent open heart surgery. Before surgery, the patient’s best FVC value was 55% of the predicted. What would you recommend in order to treat the patient’s atelectasis?

77. While monitoring a patient during a spontaneous breathing trial, which of the following observations would cause you to stop the trial and return the patient to ventilatory support?

78. Which of the following would cause a sudden increase in the peak pressure during volume controlled ventilation?

79. You hear wheezing while auscultating a patient’s chest. This may indicate the presence of which of the following?

80. A 16-year-old patient with cystic fibrosis is receiving pressure control SIMV with pressure support due to a severe bilateral pneumonia. The pulmonologist asks you to administer aerosolized dornase alfa (Pulmozyme) in-line with the ventilator. Which of these devices would you select to administer this therapy?

81. While performing a routine patient-ventilator check, you note the following settings and parameters:
Exhaled tidal volume 650 mL
Peak inspiratory pressure 33 cm H2O
High pressure limit 60 cm H2O
Low pressure alarm 20 cm H2O
Low tidal volume alarm 500 mL
Which of the following change would you make?

82. Which of the following should you do when the reservoir bag of a nonrebreathing mask collapses completely during inspiration?

83. The normal range for the pulmonary capillary wedge pressure (PCWP) as measured via the distal port of a pulmonary artery or Swan-Ganz catheter (with the balloon inflated) is:

84. Of the following statements, which is TRUE regarding capillary blood gas sampling?

85. You are trying to wean an alert intubated patient off full ventilatory support using the CPAP protocol with 40% O2. Early in the initial effort her respiratory rate increases from 24 to 30/min and you start to observe some use of her accessory muscles while breathing. Which of the following would be your first action at this time?

86. A nurse who recently set up a pleural drainage system on a patient with a pneumothorax complains that she doesn’t see any bubbling in the suction control chamber. After checking the suction control regulator to confirm that it is on, which of the following would you recommend that she do next?

87. If you were to hear bronchial breath sounds over the patient’s right middle lobe, what condition would you suspect is probably present?

88. While setting up a 12-lead EKG on a patient, you are unable obtain any electrical signal. The batteries are fully charged and the device was able to power-on. The most likely cause of this problem is which of the following?

89. After assessing an acutely dyspneic and hypotensive patient, you note the following, all on the left side of the chest: reduced chest expansion, hyperresonance to percussion, absent of breath sounds and tactile fremitus, and a tracheal shift to the right. These findings most likely suggest:

90. While reviewing the chest X-ray of a 30-year-old male receiving ventilatory support via an oral endotracheal tube. To assure proper placement of the tube, you would look for its tip to be positioned

91. The attending physician requests that you increase the expiratory time on a patient receiving volume control ventilation, but not alter the minute ventilation. Which of the following settings would you adjust to fulfill this request?

92. Based on an overnight oximetry test, a patient suspected of having sleep disordered breathing exhibits an oxygen desaturation index (ODI) of 48/hr. Which of the following would you recommend?

93. You are called to the NICU. A premature neonate receiving positive pressure ventilation exhibits acute respiratory distress, hypotension, and asymmetrical chest motion. Which of the following procedures would you initially recommend?

94. Your patient is receiving volume control A/C ventilation. She has become increasingly agitated and the end-tidal CO2 has decreased from 38 to 27 torr over the last 3 hours. Which of the following is most likely the cause?

95. You are called to the emergency department to help care for a patient who was in a vehicle accident and has chest injuries including broken ribs. Crepitations are felt while palpitating the patient’s neck. What is most likely the cause of this?

96. A forced expiratory measurement obtained after the administration of a bronchodilator shows an increase in FEV1 from 60% to 80% of predicted. This indicates a:

97. Which of the following imaging procedures is used to evaluate the arteries for abnormalities such as aneurysm, atherosclerosis, embolism, occlusion, stenosis, thrombosis, trauma, or vasculitis?

98. What is the major hazard associated with the use of bag-valve resuscitator?

99. The most likely cause of stridor in an adult patient would be which of the following?

100. While ventilating a child with a manual resuscitator, the pressure relief valve continually activates. Your first action should be which of the following?

101. An unconscious patient was admitted to the ER with an SpO2 of 94% but analysis of an arterial blood sample using a CO-oximeter reveals a SaO2 of 69%. Which of the following is most likely the problem?

102. You are using a portable pressure-cycled ventilator with a heated humidifier and IPPB circuit to temporarily ventilate a post-operative patient who is regaining consciousness in the recovery room. After checking the patient and ventilator, you notice that the inspiratory time is prolonged and the machine does not cycle off without active patient effort. What should you do in order to correct the problem?

103. An asthmatic patient is struggling to initiate inspiration on a ventilator operating in the assist-control mode. Which of the following ventilator settings would you first check in order to resolve of this problem?

104. If the patient complains of difficulty in starting the IPPB treatment, which control should you adjust?

105. The physician orders an increase in PEEP from 10 to 14 cm H2O for a patient receiving mechanical ventilation. After you adjust the PEEP setting, you note a rapid drop in the patient’s blood pressure and a significant rise in heart rate. Which of the following actions would be appropriate?

106. What is the purpose of the pilot balloon on an endotracheal or tracheostomy tube?

107. In order to initiate weaning, you change the patient from volume control A/C ventilation to pressure support. After 30 minutes on pressure support, the high respiratory rate alarm sounds, with the patient breathing at a rate of 25 to 30 per minute. What change should you make to the ventilator settings?

108. When reviewing a chest x-ray, you note that the heart is shifted to the patient’s right. Which of the following is the most likely cause of this finding?

109. A male patient with a smaller than normal trach tube is placed on volume control SIMV at a rate of 8/min. Over the last hour, you note the patient increasing use of his accessory muscles during spontaneous breaths, accompanied by some abdominal paradox. Which of the following would be the best way to overcome this problem?

110. A ventilator operating in the volume controlled A/C mode incorporates an inspiratory time limit control as a safety backup to its normal cycling. If the time needed to deliver the volume increases to the preset limit, which of the following will occur?

111. An ambulatory home oxygen therapy patient complains that her portable liquid system running at 2 L/min doesn’t last long enough for her to visit with her grandchildren. Which of the following would you recommend to overcome this limitation?

112. On inspection of a patient’s EKG strip, you note that there are no identifiable P waves; rapid irregular undulations of the isoelectric line; and an irregular ventricular rhythm. In addition, the precordial cardiac rate is greater than the peripheral pulse rate. What is the most likely problem?

113. The physician orders A/C pressure control for a 55 kg postoperative male patient. Which of the following settings would you choose for this patient?

114. You have a patient that is receiving pressure controlled A/C ventilation. Which of the following changes would you expect to occur if the patient’s lung compliance were to decrease?

115. A patient in intensive care unit develops a supraventricular tachycardia at a rate of 162/min. Which of the following effects would this have on cardiac function?

116. Which of the following valves in a typical high frequency oscillation ventilator is used to regulate the mean airway pressure?

117. While reviewing the chart of a 63-year-old patient diagnosed with COPD and chronic hypoxemia, you would expect to find which of the following?

118. If a patient develops a paradoxical pulse following trauma or cardiothoracic surgery, especially in connection with increasing venous pressure and heart rate, it would suggest which of the following?

119. To continuously monitor the adequacy of ventilation of a patient in ICU being supported by mask BiPAP, you would recommend which of the following?

120. After feeling chest pain and shortness of breath, a 38-year-old female drove herself to the emergency room. After starting oxygen therapy on the patient, the RRT performed a physical exam and noted: a hyperresonant percussion note on the right side and a tracheal shift to the left. What is most likely the cause of these findings?

121. Which of the following would cause an increase in a patient’s peak airway pressure while receiving volume control ventilation?

122. After assessing your patient, they are acutely dyspneic and hypotensive, you note the following (all limited to the left hemithorax): reduced chest expansion, hyperresonance to percussion, absent of breath sounds and tactile fremitus, and a tracheal shift to the right. Which of the following would these findings suggest?

123. A normal vital capacity for a female patient who is five feet three inches tall and weighs fifty kilograms would be approximately:

124. An unconscious apneic patient with a full stomach cannot be orally intubated in the emergency room. Which of the following would your recommend be?

125. Which of the following ECG leads should be placed in the 5th intercostal space?

126. Which of the following is the most common problem encountered when applying assist-control mode during ventilation?

127. A pneumothorax in the clinical setting is classified as which of the following primary disorders?

128. After opening the valve on an E cylinder which has a regulator attached, you hear a hissing noise. The flowmeter/gauge is turned off. Which of the following corrective actions should you take?

129. A doctor orders O2 titration with exercise for a patient with a chief complaint of dyspnea on exertion. The patient’s baseline SpO2 is 84% on room air. You would:

130. Which of the following humidifier devices would you select in order to condition the inspired gas to 100% body humidity?

131. While reviewing the flow sheet of a patient receiving artificial ventilatory support, you note a progressive rise in heart rate over the last two hours. Which of the following actions would you recommend to help identify the cause of this problem?

132. You are called to perform a sputum induction on a trach patient to gather a sample for microbiological identification. The sample is collected using a Lukens trap. When applying suction after entering the airway, the mucus should:

133. Which of the following would you expect to find on the AP chest radiograph of a patient suffering from advanced stages of pulmonary emphysema?

134. A patient is admitted with signs and symptoms, as well as a history consistent with bronchiectasis. You should recommend which of the following to confirm or rule out this diagnosis?

135. While inspecting an EKG rhythm strip from an adult patient, you note the following: rate of 148; regular rhythm; normal P waves, P-R intervals, and QRS complexes. What is most likely the problem?

136. While assessing a patient who is receiving ventilatory support, you note significant weakening of the pulse during the inspiration of machine-given breaths. Which of the following is the most likely cause of this finding?

137. A patient in intensive care unit is suspected of having developed a bacterial ventilator associated pneumonia. Which of the following procedures would you recommend in order to diagnose the cause of this problem?

138. A 53-year-old female patient with chronic bronchitis is receiving volume controlled A/C ventilation. Wheezing is heard over all lung fields and rhonchial fremitus is felt over the central airways. Also, her secretions are very thick. The patient’s peak pressure is 45 cm H2O and plateau pressure is 20 cm H2O. Which of the following would be useful to treat the patient’s condition?

139. Which of the following initial blood gas results would a respiratory therapist expect to find in a patient with a mild flail chest?

140. An apnea monitor alarm is sounding continuously but your initial assessment of the patient reveals that they are breathing normally. You next action should be to:

141. Which of the following will tend to cause false LOW readings when using a pulse oximeter?

142. While doing a normal patient assessment, you note that the arterial pressure monitor of a conscious patient in no apparent distress that the pressure waveform is absent and the alarm is sounding. What should your first action be?

143. A patient is considered to have sufficient respiratory muscle strength to maintain adequate ventilation and prevent secretion retention when the maximum inspiratory pressure (MIP; NIF) is more negative than which of the following?

144. Ventilatory support may be indicated when the pulmonary R-L shunt fraction (Qs/Qt) rises above what level?

145. An intubated adult 65-year-old male patient with severe expiratory airway obstruction requires ventilatory support. Which of the following capabilities would be most important in selecting a ventilator for this patient?

146. In assessing a patient in the acute phase of ARDS, which of the following would you expect to find?

147. You are called and asked to decrease the PaCO2 of a patient receiving high-frequency oscillation ventilation. Which of the following should you consider adjusting?

148. Which of the following would most likely cause a misleading or incorrect pulse oximetry reading?

149. Based on your patient’s smoking history and their physical exam, you immediately suspect them of having bronchogenic carcinoma. You would recommend which of the following tests to confirm or rule-out this diagnosis?

150. Which of the following conditions would most likely be associated with a difficult airway?

151. Which of the following is true regarding synchronous intermittent mandatory ventilation (SIMV)?

152. While comparing previously recorded values to those currently observed on a patient receiving volume control ventilation, you note a decrease in expired volume and a decreased airway pressure. There has been no change in ventilator settings. Which of the following best explains these findings?

153. You are called to assist a physician who is inserting a pulmonary artery catheter. During the procedure, you note a changeover on the monitor from pressures of about 25/5 mm Hg to pressures of 25/15 mm Hg. Which of the following most likely has occurred?

154. While observing the AP chest radiograph of a patient suffering from advanced stages of pulmonary emphysema, which of the following finding would you expect to see?

155. Which of the following is the best bedside measurement for assessing the integrated function of the respiratory muscles and mechanical properties of the lungs and thorax?

156. While at the bedside of a patient receiving volume control ventilation, you suddenly notice the simultaneous sounding of the high pressure and low volume alarms. Which of following is the most likely cause of this problem?

157. You should recommend AGAINST performing a diagnostic bronchoscopy procedure on a patient with which of the following?

158. An AP X-ray of a 4-year-old child with wheezing and stridor shows an area of prominent subglottic edema, but the lateral neck X-ray appears normal. The most likely problem is?

159. Your patient is receiving continuous mechanical ventilation. On auscultation, you suspect that the patient’s endotracheal tube is in the right main stem bronchus. Which action should you take at this time?

160. A 62-year-old male patient with a history of COPD and CHF have arrived in the ER with a complaint of difficulty breathing. To help with the differential diagnosis, the doctor orders the patient’s blood to be tested for bacteremia, CK-MB, cTnI, cTnT, and BNP. All results are negative. What is the most likely cause of the patient’s dyspnea?