[version 4; peer review: 2 approved]
No competing interests were disclosed.
One-lung ventilation (OLV) is used to isolate one lung during thoracic surgery, but manipulation and positioning can affect heart-lung interaction. Cardiomegaly may exacerbate these changes, especially in the left lateral decubitus (LLD) position.
To investigate the effect of cardiomegaly on heart-lung interaction during OLV, particularly in the LLD position.
A 20-year-old male with recurrent spontaneous pneumothorax was scheduled for right-sided
Cardiomegaly alters heart-lung interaction during OLV, particularly in the LLD position. The enlarged heart exerts pressure on the left lung, impairing ventilation. When both lungs are ventilated in this position, ventilation is directed toward the right lung, reducing oxygenation and causing desaturation. However, restricting ventilation to the left lung improved oxygenation due to better lung compliance and less interference from the enlarged heart.
Cardiomegaly affects heart-lung interaction during OLV in the LLD position. Oxygenation improves when only the left lung is ventilated, likely due to less compression of the left lung. The supine position may further enhance oxygenation even with bilateral ventilation. This case highlights the importance of considering cardiomegaly in OLV management. This section should be written as per the CARE checklist item 3.
We have revised the manuscript to improve clarity and ensure physiological consistency. Key changes include clarification of ventilatory dynamics during both two-lung and one-lung ventilation, specifically the presence and subsequent cessation of tidal volume loss through the bronchopleural fistula. The description of ventilatory management has been refined to better reflect the rationale for parameter adjustments, emphasizing airway pressure reduction and hemodynamic considerations. In addition, the discussion has been substantially revised to correct the interpretation of oxygenation changes, highlighting the role of cardiomegaly, intrathoracic pressure, pulmonary vascular compression, and right ventricular dysfunction in influencing ventilation–perfusion mismatch. These revisions aim to provide a more accurate and coherent explanation of the clinical findings.
One-lung ventilation (OLV) is a technique used during thoracotomy to selectively ventilate one lung while collapsing the other. This can be achieved using a double-lumen tube (DLT), a single-lumen tube with a bronchial blocker, or an endotracheal tube positioned endobronchially (
Timeline of patient is presented by
| Date/Period | Event | Findings/Intervention | Outcome |
|---|---|---|---|
| March 2022 | Sudden onset shortness of breath | Diagnosed with right spontaneous pneumothorax | Thoracic drain inserted |
| Day 8 | Follow-up | Improvement on chest X-ray | Drain removed |
| Day 9 | Recurrence of dyspnea | Repeat thoracic drain insertion | Symptom relief |
| Following days | Diagnostic imaging | CT scan → bronchopleural fistula (posterior segment, RUL) | Planned thoracotomy |
| Pre-op | Preoperative evaluation | Stable vitals; ABG: pH 7.37, PaO 2 80 mmHg, PaO 2/FiO 2 200; Echo: RA/RV dilatation, pulmonary & tricuspid regurgitation | Intermediate probability of pulmonary hypertension |
| Intra-op | Induction & intubation | Fentanyl, propofol, rocuronium; sevoflurane; double-lumen tube; VC ventilation | Hemodynamically stable |
| Intra-op | Positioning | Patient positioned in left lateral decubitus (LLD); two-lung ventilation maintained | No immediate desaturation |
| Intra-op | Initiation of OLV | One-lung ventilation of left lung initiated | Oxygen saturation began to decrease |
| Intra-op | Hemodynamic event | Hypotension (75/45 mmHg) and SpO 2 decreased to 88% | Suspected RV strain |
| Intra-op | Management | Norepinephrine and milrinone started; ventilator adjusted (TV 300 mL, RR 20, PEEP 8, FiO 2 100%) | SpO 2 improved to 92% |
| Post-op | Supine, two-lung ventilation | Oxygenation stabilized | No further desaturation |
Anesthesia was induced with fentanyl, propofol, and rocuronium. After adequate muscle relaxation, a 37 Fr left-sided double-lumen tube (DLT) was inserted. Correct placement was confirmed clinically by auscultation and selective lung ventilation assessment. Following intubation, mechanical ventilation was initiated in volume-controlled mode with a tidal volume of 360 mL, respiratory rate 18 breaths per minute, PEEP 5 cmH 2O, and FiO 2 0.5. Oxygen saturation improved to 99%, and hemodynamics remained stable.
After surgical preparation, the patient was positioned in the left lateral decubitus (LLD) position. Two-lung ventilation was initially maintained during positioning, and no immediate desaturation occurred. During two-lung ventilation, an unknown portion of tidal volume was leaking through the bronchopleural fistula.
One-lung ventilation (OLV) of the left lung was then initiated to facilitate right thoracotomy. Shortly after initiation of OLV in the LLD position, the patient developed progressive hypotension (blood pressure decreased to 75/45 mmHg) accompanied by oxygen desaturation to 88%. At this time, the volume loss through the bronchopleural fistula stopped; therefore, the ventilatory parameters were reassessed and adjusted. Tidal volume was reduced to 300 mL, respiratory rate increased to 20 breaths per minute, PEEP increased to 8 cmH 2O, and FiO 2 increased to 1.0. Tidal volume was reduced to decrease airway pressure. This strategy helped limit excessive intrathoracic pressure that could worsen hemodynamic compromise.
Vasopressor and inotropic support were initiated with norepinephrine (50 ng/kg/min) and milrinone (0.3 μg/kg/min) to address suspected right ventricular strain and reduced systemic vascular resistance. Following these interventions, oxygen saturation improved gradually to 92%, and blood pressure stabilized.
No major surgical traction or compression events were noted at the time of desaturation. The remainder of the procedure proceeded under careful hemodynamic and ventilatory monitoring.
At the end of surgery, the patient was returned to the supine position and two-lung ventilation was resumed. Oxygenation stabilized, and no further desaturation episodes were observed.
In this case, intraoperative desaturation occurred shortly after initiation of one-lung ventilation (OLV) in the left lateral decubitus (LLD) position, accompanied by hypotension. Several potential mechanisms were considered, including double-lumen tube (DLT) malposition, increased right-to-left intrapulmonary shunt during OLV, atelectasis of the dependent lung, acute right ventricular dysfunction, and mechanical compression of the lung due to severe cardiomegaly.
Several mechanisms may explain the observed cardiopulmonary interaction in this case. One-lung ventilation can increase pulmonary vascular resistance due to hypoxic pulmonary vasoconstriction and altered pulmonary blood flow distribution. In patients with pre-existing cardiomegaly and limited cardiopulmonary reserve, this increase in pulmonary vascular resistance may elevate right ventricular afterload and impair right ventricular output. Furthermore, changes in ventilation–perfusion relationships during lung isolation may worsen gas exchange and contribute to intraoperative oxygen desaturation.
DLT malposition was considered unlikely based on clinical reassessment and selective ventilation findings. The close temporal relationship between positioning, initiation of OLV, hemodynamic instability, and oxygen desaturation suggested a combined cardiopulmonary interaction rather than an isolated ventilatory issue.
The incidence of hypoxemia during OLV has decreased significantly over time, from approximately 25% in the 1970s to less than 10% in modern practice (
The present case deviated from this classical pattern. The patient had severe cardiomegaly (cardiothoracic ratio 75%) with right atrial (RA) and right ventricular (RV) dilation and suspected pulmonary hypertension. Pulmonary hypertension, which may develop in patients with chronic lung disease or post-COVID-19 pulmonary sequelae, increases RV afterload and reduces cardiopulmonary reserve (
Positive pressure ventilation during OLV can further exacerbate these hemodynamic alterations. Increased intrathoracic pressure may reduce venous return and elevate right atrial pressure, thereby compromising RV preload. In addition, excessive alveolar distension may compress pulmonary capillaries and increase PVR, potentially worsening RV afterload and decreasing cardiac output (
The presence of a bronchopleural fistula may also influence intrathoracic pressure dynamics during mechanical ventilation. During two-lung ventilation, the fistula may partially limit excessive increases in intrathoracic pressure by allowing air leakage. However, during one-lung ventilation, the resulting increase in pulmonary vascular resistance may significantly elevate right ventricular afterload. In patients with impaired right ventricular reserve, this may compromise right ventricular output and contribute to hemodynamic instability.
A distinctive feature of this case was better oxygenation when both lungs were ventilated in the LLD position. We hypothesize that during one-lung ventilation, severe cardiomegaly and increased intrathoracic pressure led to compression of the pulmonary vasculature and aggravated right ventricular dysfunction. This may have redirected perfusion toward the non-dependent right lung, which was diseased, thereby worsening ventilation–perfusion mismatch. Conceivably, the combined effects of reduced tidal volume, milrinone, and norepinephrine improved right ventricular performance, increased systemic arterial pressure, and enhanced arterial oxygenation.
After returning the patient to the supine position and resuming two-lung ventilation, oxygenation stabilized. In the supine position, posterior displacement of the enlarged heart may reduce its compressive effect on lung parenchyma, thereby improving regional ventilation. Nonetheless, cardiomegaly may still influence lower-lobe ventilation distribution even in the supine position.
This case suggests that in patients with severe cardiomegaly and suspected pulmonary hypertension, oxygenation behavior during OLV may not follow classical physiological expectations. Unexpected hypoxemia in such patients should prompt evaluation not only of airway devices and ventilatory settings, but also of positional and mediastinal effects on lung mechanics. Awareness of altered heart–lung interaction may help guide intraoperative decision-making and prevent unnecessary escalation of interventions.
This case report has several limitations. Detailed serial intraoperative physiological parameters such as dynamic lung compliance, airway pressure trends, serial arterial blood gas values, and comprehensive echocardiographic indices were not systematically documented, as this case was not initially managed as a prospective physiological study. In addition, the right ventricular systolic pressure (RVSP) could not be quantified from the available echocardiographic report, limiting precise assessment of pulmonary hypertension severity. Therefore, the proposed mechanisms remain inferential and based on available clinical data combined with established heart–lung interaction principles. Future prospective studies incorporating advanced hemodynamic and respiratory monitoring would be valuable to confirm these observations.
This case highlights the complex cardiopulmonary interactions that may occur during one-lung ventilation in patients with impaired cardiopulmonary reserve. Careful anticipation of potential hemodynamic changes and appropriate adjustment of ventilatory parameters are essential to maintain oxygenation and hemodynamic stability in such patients.
Written informed consent for the publication of this case report and any associated images has been obtained from the patient. The patient has given permission for their medical information to be published in this case report. All identifying information has been removed to ensure confidentiality, in accordance with ethical standards and privacy regulations.
All data underlying the results are available as part of the article and no additional source data are required.
The CARE checklist for this case report is available in the Zenodo repository, DOI:
Data are available under the terms of the
The authors extend their deepest gratitude to the staff of the Department of Anesthesiology and Reanimation, Faculty of Medicine, Universitas Airlangga and Dr. Soetomo General Academic Hospital for their invaluable assistance and continuous support in writing and publishing this case report.
The authors have sufficiently addressed all comments and concerns.
Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes?
Partly
Is the case presented with sufficient detail to be useful for other practitioners?
Partly
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?
Partly
Is the background of the case’s history and progression described in sufficient detail?
Partly
Reviewer Expertise:
Anesthesiology; perioperative analgesia; pain neuroscience; neuroimmune mechanisms;
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
The authors have revised the manuscript and is now acceptable.
Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes?
Yes
Is the case presented with sufficient detail to be useful for other practitioners?
Partly
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?
No
Is the background of the case’s history and progression described in sufficient detail?
Partly
Reviewer Expertise:
Cardiovascular physiology; cardiopulmonary bypass, adult and pediatric cardiac anesthesia, thoracic anesthesia,
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
2nd revision
Introduction
Change 'lungs' to lung
Paragraph
After surgical preparation, the patient was positioned in the left lateral decubitus (LLD) position. Two-lung ventilation
was initially maintained during positioning, and no immediate desaturation occurred.
During two-lung ventilation, an unknown portion of tidal volume was leaking through the bronchopleural fistula.
One-lung ventilation (OLV) of the left lung was then initiated to facilitate right thoracotomy. Shortly after initiation of OLV in the LLD position, the patient developed progressive hypotension (blood pressure decreased to 75/45 mmHg) accompanied by oxygen desaturation to 88%. At this time, ventilatory parameters were reassessed and adjusted. Tidal volume was reduced to 300 mL, respiratory rate increased to 20 breaths per minute, PEEP increased to 8 cmH2O, and
FiO2 increased to 1.0. Tidal volume was reduced to decrease airway pressure and minimize air leakage through the
bronchopleural fistula. To maintain adequate minute ventilation, the respiratory rate was increased. This strategy also helped limit excessive intrathoracic pressure that could worsen hemodynamic compromise.
One-lung ventilation (OLV) of the left lung was then initiated to facilitate right thoracotomy. Shortly after initiation of
OLV in the LLD position, the patient developed progressive hypotension (blood pressure decreased to 75/45 mmHg)
accompanied by oxygen desaturation to 88%. At this time, the volume loss through the bronchopleural fistula stopped; therefore, the ventilatory parameters were reassessed and adjusted. Tidal volume was reduced to 300 mL, respiratory rate increased to 20 breaths per minute, PEEP increased to 8 cmH2O, and FiO2 increased to 1.0. Tidal volume was reduced to decrease airway pressure. This strategy helped limit excessive intrathoracic pressure that could worsen hemodynamic compromise.
A distinctive feature of this case was the improvement in oxygenation when only the dependent left lung was ventilated in the LLD position. We hypothesize that severe cardiomegaly altered the usual distribution of ventilation. In the LLD position, gravitational displacement of the mediastinum combined with marked cardiac enlargement may have exerted compressive forces on the dependent left lung, reducing its compliance during two-lung ventilation. This could have redirected ventilation preferentially toward the non-dependent right lung, which was diseased, thereby worsening V/Q mismatch despite ongoing perfusion of the dependent lung.
A distinctive feature of this case was better oxygenation when both the lungs were ventilated in the LLD position. We hypothesize that during one lung ventilation, severe cardiomegaly and increased intrathoracic pressure increased the compression of pulmonary vasculature and aggravated right ventricular dysfunction. This could have
redirected perfusion toward the non-dependent right lung, which was diseased, thereby worsening V/Q mismatch. Conceivably, reduced tidal volume, milrinone and nor-epinephrine combined together improved RV performance, increased the systemic arterial pressure and arterial saturation.
Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes?
Yes
Is the case presented with sufficient detail to be useful for other practitioners?
Partly
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?
No
Is the background of the case’s history and progression described in sufficient detail?
Partly
Reviewer Expertise:
Cardiovascular physiology; cardiopulmonary bypass, adult and pediatric cardiac anesthesia, thoracic anesthesia,
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
Dear Reviewer,
Thank you very much for your careful review and valuable comments on our manuscript. We have revised the manuscript accordingly and addressed each point as follows:
Comment: Change “lungs” to “lung” Response: Revised as suggested.
Comment: Add the sentence regarding tidal volume leakage through the bronchopleural fistula Response: The sentence “During two-lung ventilation, an unknown portion of tidal volume was leaking through the bronchopleural fistula.” has been added to clarify the presence of air leakage during two-lung ventilation.
Comment: Modify the paragraph as suggested Response: The paragraph has been revised accordingly. We have clarified that volume loss through the bronchopleural fistula ceased after initiation of OLV and adjusted the explanation of ventilatory management to focus on reduction of airway pressure and limitation of intrathoracic pressure to mitigate hemodynamic compromise.
Comment: Rewrite the paragraph Response: The paragraph has been substantially revised as suggested. We have corrected the interpretation to reflect improved oxygenation during two-lung ventilation rather than OLV. The discussion now emphasizes the role of severe cardiomegaly, increased intrathoracic pressure, pulmonary vascular compression, and right ventricular dysfunction in worsening ventilation–perfusion mismatch. We also incorporated the contribution of reduced tidal volume, milrinone, and norepinephrine in improving right ventricular performance and systemic oxygenation.
We believe these revisions have significantly improved the clarity and physiological consistency of the manuscript. We sincerely appreciate your insightful comments.
Kind regards,
On behalf of all authors,
Suryanti Chan
The sentence, “The procedure involves both manipulation of the lungs and changes in body positioning, which can affect heart-lung interaction” is not clear, do the authors mean ‘surgical procedure’ please rephrase
In view of continuous oxygen requirement, did you measure peripheral oxygen saturation (SpO2) on room air?
However, OLV also affects cardiac function. Positive pressure ventilation can decrease venous return and systemic vascular resistance. How do you explain a decrease in systemic vascular resistance with positive pressure ventilation? please expand and provide reference.
The patient exhibited desaturation when both lungs were ventilated, but oxygenation improved when only the diseased lung was ventilated. The timeline described in the case report and the sentence do not match; as per the case report, the saturation was normal when both the lungs were ventilated and the patient developed desaturation after the initiation of one lung ventilation.
Transthoracic echocardiography demonstrated right atrial and right ventricular dilatation with evidence of impaired cardiopulmonary reserve, what was the right ventricular systolic pressure (RVSP) measured by TR jet?
Following intubation, mechanical ventilation was initiated in volume-controlled mode with a tidal volume of 360 mL, respiratory rate 18 breaths per minute, PEEP 5cmH2O, and FiO2 0.5. Oxygen saturation improved to 99%, and hemodynamics remained stable. Do you mean two lung ventilation? How did you manage loss of tidal volume through bronchopleural fistula?
Table 1: comment on right ventricular systolic pressure
Timeline-Intraop: describe ventilation parameters in detail. From the timeline it is not clear when the patient deteriorated and developed desaturation and hypotension. In the case report it is mentioned that initially two-lung ventilation was maintained and there was no desaturation. Does it mean that patient developed complications after initiating one lung ventilation?
Tidal volume was reduced to 300 mL, respiratory rate increased to 20 breaths per minute, PEEP increased to 8cmH2O, and FiO2 increased to 1.0. what was the rationale?
The close temporal relationship between positioning, initiation of OLV, hemodynamic instability, and oxygen desaturation suggested a combined cardiopulmonary interaction rather than an isolated ventilatory issue, please expand. What were the possible mechanisms and how did you assess them and finally what was the responsible mechanism?
The hypothesis, ‘The present case deviated from this classical pattern. The patient had severe cardiomegaly…and increase PVR, potentially worsening RV afterload and decreasing cardiac output (Guia et al., 2020). The observed intraoperative hypotension supports the possibility of transient RV compromise in this setting. You should discuss the role of bronchopleural fistula during two lung ventilation, I believe, during two lung ventilation, the bronchopleural fistula prevented excessive increase in intrathoracic pressure and pulmonary vascular resistance. With the initiation of OLV, the pulmonary vascular resistance severely, which increased tricuspid and pulmonary regurgitation and severely compromised right ventricular cardiac output. Consequently, decreasing left ventricular cardiac output and precipitating severe hypotension and desaturation. The vicious cycle was interrupted once tidal volume was decreased. The decrease in right ventricular cardiac output is expected to be pronounced in presence of right ventricular dysfunction.
We hypothesize…thereby worsening V/Q mismatch despite ongoing perfusion of the dependent lung; this is possible, if there is no bronchopleural fistula; however, the effect is expected to be mild in presence of bronchopleural fistula.
When OLV was instituted…explanation is physiologically consistent with known heart–lung interaction principles (Marongiu et al., 2020). This paragraph can be removed
This case suggests that in patients with severe cardiomegaly and suspected pulmonary hypertension, oxygenation behavior during OLV may not follow classical physiological expectations, I do not agree with the statement. The deterioration of hemodynamic and saturation should be anticipated and, perhaps, appropriate adjustments of ventilation parameters would have prevented the deterioration.
Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes?
Yes
Is the case presented with sufficient detail to be useful for other practitioners?
Partly
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?
No
Is the background of the case’s history and progression described in sufficient detail?
Partly
Reviewer Expertise:
Cardiovascular physiology; cardiopulmonary bypass, adult and pediatric cardiac anesthesia, thoracic anesthesia,
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
We sincerely thank the reviewer for the insightful and constructive comments. We have carefully revised the manuscript to address all concerns. Detailed responses to each comment are provided below, and the corresponding revisions have been incorporated into the manuscript.
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initiation of two-lung ventilation transition to one-lung ventilation onset of desaturation and hypotension subsequent ventilatory adjustment
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We thank the reviewer for this important suggestion. The discussion has been expanded to describe possible mechanisms including:
increased pulmonary vascular resistance during OLV right ventricular afterload elevation impaired right ventricular output in the presence of cardiomegaly altered ventilation-perfusion relationships
These mechanisms were considered in explaining the observed intraoperative hemodynamic instability.
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The conclusion has been modified to reflect a more cautious interpretation of the findings.
The background and progress are described to some extent, but not sufficiently:
1) The overall timeline is unclear;
2) There is a lack of description of the preoperative respiratory status;
3) Descriptions of key events are still lacking, such as the specific timing of changes in body position, when one-lung ventilation was started, how the DLT position was confirmed, whether there was surgical traction/compression, re-expansion procedures, changes in ABG, changes in airway pressure/compliance, etc. The text lacks physical examination-related content such as dynamic changes in vital signs, respiratory examination, signs of respiratory distress, and cardiac examination; in terms of diagnostic examinations, it lacks indicators reflecting the severity of cardiopulmonary function, such as key echocardiographic parameters (TR Vmax, estimated PASP, TAPSE), right ventricular function, estimated pulmonary artery pressure, baseline hemodynamics, and exercise tolerance; follow-up is too brief, lacking details on objective endpoints such as postoperative imaging re-examination, ABG/echocardiography, chest tube indwelling time, whether the condition relapsed, and length of hospital stay. The discussion section still has shortcomings.
First, the hypotheses should be discussed based on key objective physiological data (vital signs, ABG, airway pressure/compliance, EtCO₂ trends, etc.). Second, it is recommended to discuss the reasons for the intraoperative oxygen saturation decrease and the basis for exclusion. Finally, it is recommended to elaborate on the clinical significance of this case. Due to the insufficient detail in the case description, it is currently not sufficient to provide guidance for other clinicians in real-world clinical scenarios.
Are enough details provided of any physical examination and diagnostic tests, treatment given and outcomes?
Partly
Is the case presented with sufficient detail to be useful for other practitioners?
Partly
Is sufficient discussion included of the importance of the findings and their relevance to future understanding of disease processes, diagnosis or treatment?
Partly
Is the background of the case’s history and progression described in sufficient detail?
Partly
Reviewer Expertise:
clinical anesthesia; acute pain; chronic pain
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
We sincerely thank the reviewer for the detailed and insightful comments. We fully agree that additional physiological parameters such as serial ABG measurements, detailed airway pressure/compliance trends, comprehensive echocardiographic indices, and extended follow-up data would strengthen the scientific rigor of this report.
However, as this case was retrospectively prepared from routine clinical practice rather than a prospectively designed physiological study, certain detailed intraoperative parameters were not systematically recorded or are no longer retrievable from the medical record.
Nevertheless, we have carefully revised the manuscript to:
Clarify the intraoperative timeline and sequence of events. Expand the description of preoperative cardiopulmonary status based on available data. Provide a more structured physiological interpretation based on the documented vital signs and clinical course. Include a dedicated “Limitations” paragraph in the Discussion acknowledging the absence of detailed serial physiological data. Emphasize that this report is hypothesis-generating and aims to highlight a potentially under-recognized heart–lung interaction phenomenon in patients with severe cardiomegaly undergoing OLV.
We agree that future prospective studies with comprehensive hemodynamic and respiratory monitoring would be necessary to validate the proposed mechanisms.
We sincerely appreciate the reviewer’s comments, which have helped us improve the clarity and transparency of our report.