US Probe: Unmasking the Lung Pulse

Author: Stephen Alerhand MD (@SAlerhand, Instructor of Emergency Medicine and Ultrasound Fellow, Icahn School of Medicine at Mount Sinai) // Edited by: Alex Koyfman, MD (@EMHighAK), Brit Long, MD (@long_brit), and Manpreet Singh, MD (@MprizzleER)

What is the “lung pulse”?

  • Lung pulse refers to the rhythmic movement of the visceral pleura along the stationary parietal pleura with each cardiac contraction [1].
  • It reflects transmission of heart vibrations through a motionless lung.
  • The lung pulse was first described by Daniel Lichtenstein in the only study to date assessing its accuracy [1].


Video 1: Lung pulse shown by transducer placed on right and left anterolateral chest walls. Notice how the pleural line demonstrates somewhat of a vertical deflection, as opposed to the typical horizontal movement of normal lung sliding. Due to its closer proximity to the pulsating heart, the left-sided pleura shows larger-amplitude deflections than on the right.


Image 1: Lung pulse visualized in M-mode

What does the lung pulse mean?

  • It means that the parietal and visceral pleura are opposing one another.
  • It also means that there is no lung sliding at that focal lung region. The underlying lung pulse has been unmasked.

How does lung pulse evaluate for physiologic atelectasis?

  • Due to lack of local respiratory movement and air flow, there is absent lung sliding with unmasking of the underlying lung pulse [1, 2].
    • Some examples include: mainstem intubation, obstructive bronchial foreign body, temporary voluntary apnea, and pharmacological paralysis.

Can lung pulse thus play a role in detecting mainstem intubation?

  • The classic methods of confirming proper ETT placement are not infallible.
    • Auscultation for bilateral breath sounds may be hindered by ambient noise, patient body habitus, and ongoing resuscitative measures.
      • Endobronchial intubation was missed in up to 55% of cases by first-year anesthesia residents [3].
    • Quantitative end-tidal capnography is not well suited for detecting endobronchial placement of the ETT [4].
  • Single-lung intubation leads to both immediate and downstream complications.
    • Suboptimal ventilation and oxygenation will occur without gas exchange in the contralateral lung.
    • Barotrauma from large volumes may cause pneumothorax (PTX). Unilateral pulmonary edema may also develop [5].
    • Unnecessary thoracostomy for presumed PTX may be performed when simple, slight ETT retraction would have sufficed.
  • In Lichtenstein et al.’s prospective study in patients without history of respiratory disorders, 15 patients requiring intubation were selectively intubated down the right lung (Group 1). Sonographic findings were compared with 30 patients undergoing nonselective intubation (Group 2) and 15 healthy volunteers (Group 3) [1].
    • A left-sided lung pulse was immediately present in 14 of 15 patients in Group 1. Lung pulse was absent in all patients in Groups 2 and 3 during breathing.
    • All patients in Group 3 exhibited a lung pulse during voluntary apnea.
  • Of note, selective intubation may not always yield complete atelectasis if some air is able to enter the contralateral lung.
    • Lung pulse is more likely to be unmasked with a deeper depth of ETT placement past the carina, i.e. greater than 4-6 cm.
    • Similarly, a foreign body that is only partially obstructing the bronchus may not yield a lung pulse if some air is able to pass around the obstruction into the lung.

How do post-intubation lung ultrasound and chest radiography differ in evaluating for physiologic atelectasis?

  • Whereas lung pulse is visualized immediately following selective mainstem intubation, the associated atelectasis only appears on chest x-ray after a delay—once the trapped residual air is progressively absorbed.
  • “Ultrasound should be considered as an alternative finer than auscultation, safer than radiography, lighter than fibroscopy, and quicker than all these procedures (provided the ultrasound is part of the ICU equipment)”—Lichtenstein et al. 2003 [1].
  • Lung ultrasound may also decrease the need for chest radiography [6].

A case series by Michael Blaivas and James Tsung illustrated the clinical utility of lung pulse for detecting endobronchial intubation and obstruction [6].

  1. 32 year-old male BIBEMS after a motor vehicle collision. He was unresponsive and intubated in the field. Vitals were: BP 95/65, HR 112, 91% O2sat on 100% FiO2. There were absent breath sounds on the right. O2 saturation dropped to 89%. A resident prepared for needle thoracostomy. Right lung slowed absent lung sliding with a lung pulse. Left mainstem intubation was suspected, and the ETT was pulled back until lung sliding appeared.
  2. 18 year-old male BIBEMS after a motorcycle collision. He was intubated in the field due to poor respiratory effort and unresponsiveness. There were decreased breath sounds on the right. EMS withdrew the ETT by 2 cm. The decreased breath sounds remained. EMS performed needle thoracostomy. In the ED, ultrasound showed lung pulse on the right. The ETT was pulled back 2 more cm, and then again 2 more cm with a sudden return of lung sliding.
  3. 10 month-old girl with Down syndrome BIBEMS due to respiratory distress. The patient was intubated in the ED. Lung pulse was visualized on the left. The ETT was withdrawn 2 cm. There was slight diaphragmatic movement and persistence of lung pulse. Suctioning was performed. Now diaphragmatic movement on the left equaled that on the right, and lung sliding was visualized on the left.


Figure 1: Point-of-Care Ultrasound Algorithm for Airway Management (courtesy of James Tsung MD)

Could there be a role for lung pulse in pre-hospital medicine for detecting mainstem intubation?

  • Prospective observational studies by Wirtz et al.and Timmermann et al.found that right mainstem intubation occurred in 15% and 10.7% of field intubations, respectively [7, 8].
    • These intubations may remain recognized until admission [9].
  • End-tidal capnography used by Emergency Medical Services (EMS) personnel is accurate for confirming ETT placement into the airway [10-13]. It is affordable and requires little training. However, it does not accurately detect endobronchial intubation [4].
  • The use of a portable handheld ultrasound device for detecting right mainstem intubations was described in a pre-hospital journal [14]:
    • In two trauma patients with right mainstem intubations, ultrasound did not visualize the specific pleural signals (lung sliding, comet-tail artifacts, power Doppler) evident in 13 other patients undergoing elective intubation. Only after ETT repositioning were these signals visualized.
  • Pre-hospital ultrasound literature has also been published on the following related applications:
    • Detection of ETT displacement [15], detection of esophageal intubation on cadavers by military flight meds [16], and detection of PTX [17].
  • Of note, a key distinction between pre-hospital and rapid-sequence intubation in the ED is that EMS personal may not administer pharmacological paralysis.
    • Thus, lung pulse would not be visualized if the patient was subtly breathing around the ETT.

What role does lung pulse play in evaluating for pneumothorax?

  • Diagnosis relies on recognition of four sonographic artifact signs [18]:
  1. Absence of lung sliding
  2. Absence of B-lines
  3. Presence of lung point
  4. Absence of lung pulse
  • “In case of extreme emergency, the absence of lung sliding, lung pulse, and B-lines allows prompt and safe diagnosis of pneumothorax without need to search for the lung point”—Volpicelli et al. 2012 [19].

Can lung pulse be incorporated into cardiac arrest?

  • Since lung pulse may signal a mainstem intubation, the ETT position may be confirmed using additional ultrasound methods such as:
    • Assessment of diaphragmatic excursion, and/or carefully retracting the ETT until the lung pulse is abolished and lung sliding returns.
  • “A sonographic pattern without detectable lung sliding, absent B-lines, and absent lung pulse in the anterior chest of unstable patients should induce the physician to place a chest tube immediately”—Volpicelli et al. 2011 [20].
    • The artifactual signs together make sense. However, when suspicion is present for PTX, time is of the essence. Finger thoracostomies may have already been performed and a chest tube possibly placed empirically. Lung pulse may also be difficult to assess during ongoing chest compressions, unless a second transducer is simultaneously used during pulse checks—though this may distract from the other more pressing tasks in a patient with cardiac arrest.

Can lung pulse play a role in the differentiation between acute respiratory distress syndrome (ARDS) and cardiogenic pulmonary edema?

  • Perhaps, though only a small role. There is much more nuance to it (to be detailed in a future EMdocs post).
    • In a study of 58 consecutive patients with ARDS or acute pulmonary edema (APE) admitted to the Intensive Care Unit, lung pulse was observed in 50% of patients with ARDS versus 0% of patients with APE (p < 0.0001) [21].
    • The investigators theorized that lung pulse in this scenario could be the result of lung consolidations or a critical reduction in pulmonary compliance.

Acknowledgement to Jim Tsung for his lung ultrasound expertise.

References

  1. Lichtenstein, D.A., et al., The “lung pulse”: an early ultrasound sign of complete atelectasis.Intensive Care Med, 2003. 29(12): p. 2187-2192.
  2. Acosta, C.M., et al., Accuracy of transthoracic lung ultrasound for diagnosing anesthesia-induced atelectasis in children.Anesthesiology, 2014. 120(6): p. 1370-9.
  3. Sitzwohl, C., et al., Endobronchial intubation detected by insertion depth of endotracheal tube, bilateral auscultation, or observation of chest movements: randomised trial.BMJ, 2010. 341: p. c5943.
  4. Sim, S.S., et al., Ultrasonographic lung sliding sign in confirming proper endotracheal intubation during emergency intubation.Resuscitation, 2012. 83(3): p. 307-12.
  5. Kramer, M.R., E. Melzer, and C.L. Sprung, Unilateral pulmonary edema after intubation of the right mainstem bronchus.Crit Care Med, 1989. 17(5): p. 472-4.
  6. Blaivas, M. and J.W. Tsung, Point-of-care sonographic detection of left endobronchial main stem intubation and obstruction versus endotracheal intubation.J Ultrasound Med, 2008. 27(5): p. 785-9.
  7. Wirtz, D.D., et al., Unrecognized misplacement of endotracheal tubes by ground prehospital providers.Prehosp Emerg Care, 2007. 11(2): p. 213-8.
  8. Timmermann, A., et al., The out-of-hospital esophageal and endobronchial intubations performed by emergency physicians.Anesth Analg, 2007. 104(3): p. 619-23.
  9. Bissinger, U., G. Lenz, and W. Kuhn, Unrecognized endobronchial intubation of emergency patients.Ann Emerg Med, 1989. 18(8): p. 853-5.
  10. Grmec, S., Comparison of three different methods to confirm tracheal tube placement in emergency intubation.Intensive Care Med, 2002. 28(6): p. 701-4.
  11. Silvestri, S., et al., The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system.Ann Emerg Med, 2005. 45(5): p. 497-503.
  12. Ko, F.Y., K.S. Hsieh, and C.K. Yu, Detection of airway CO2 partial pressure to avoid esophageal intubation.Zhonghua Min Guo Xiao Er Ke Yi Xue Hui Za Zhi, 1993. 34(2): p. 91-7.
  13. Linko, K., M. Paloheimo, and T. Tammisto, Capnography for detection of accidental oesophageal intubation.Acta Anaesthesiol Scand, 1983. 27(3): p. 199-202.
  14. Chun, R., et al., Where’s the tube? Evaluation of hand-held ultrasound in confirming endotracheal tube placement.Prehosp Disaster Med, 2004. 19(4): p. 366-9.
  15. Zadel, S., et al., Point of care ultrasound for orotracheal tube placement assessment in out-of hospital setting.Resuscitation, 2015. 87: p. 1-6.
  16. Hanlin, E.R., et al., Airway ultrasound for the confirmation of endotracheal tube placement in cadavers by military flight medic trainees – A pilot study.Am J Emerg Med, 2018.
  17. Quick, J.A., et al., In-flight ultrasound identification of pneumothorax.Emerg Radiol, 2016. 23(1): p. 3-7.
  18. Volpicelli, G., Sonographic diagnosis of pneumothorax.Intensive Care Med, 2011. 37(2): p. 224-32.
  19. Volpicelli, G., et al., International evidence-based recommendations for point-of-care lung ultrasound.Intensive Care Med, 2012. 38(4): p. 577-91.
  20. Volpicelli, G., Usefulness of emergency ultrasound in nontraumatic cardiac arrest.Am J Emerg Med, 2011. 29(2): p. 216-23.
  21. Copetti, R., G. Soldati, and P. Copetti, Chest sonography: a useful tool to differentiate acute cardiogenic pulmonary edema from acute respiratory distress syndrome.Cardiovasc Ultrasound, 2008. 6: p. 16.

 

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