AUTHOR=Godbole Rohit , Church Sanford B. , Abolhoda Amir , Porszasz Janos , Sassoon Catherine S. H. 

TITLE=Resting Physiologic Dead Space as Predictor of Postoperative Pulmonary Complications After Robotic-Assisted Lung Resection: A Pilot Study

JOURNAL=Frontiers in Physiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.803641

DOI=10.3389/fphys.2022.803641

ISSN=1664-042X

ABSTRACT=<p>Lung resection surgery carries significant risks of postoperative pulmonary complications (PPC). Cardiopulmonary exercise testing (CPET) is performed to predict risk of PPC in patients with severely reduced predicted postoperative forced expiratory volume in one second (FEV1) and diffusion of carbon monoxide (DLCO). Recently, resting end-tidal partial pressure of carbon dioxide (PETCO<sub>2</sub>) has been shown as a good predictor for increased risk of PPC. However, breath-breath breathing pattern significantly affects PETCO<sub>2</sub>. Resting physiologic dead space (VD), and physiologic dead space to tidal volume ratio (VD/VT), may be a better predictor of PPC than PETCO<sub>2</sub>. The objective of this study was to prospectively determine the utility of resting measurements of VD and VD/VT in predicting PPC in patients who underwent robotic-assisted lung resection for suspected or biopsy-proven lung malignancy. Thirty-five consecutive patients were included in the study. Patients underwent preoperative pulmonary function testing, symptom-limited CPET, and a 6-min walk test. In the first 2 min prior to the exercise portion of the CPET, we obtained resting VT, minute ventilation (<inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mi mathvariant="normal">V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math></inline-formula>E), VD (less instrument dead space), VD/VT, PETCO<sub>2</sub>, and arterial blood gases. PPC within 90 days were recorded. Fourteen (40%) patients had one or more PPC. Patients with PPC had significantly elevated resting VD compared to those without (0.318 ± 0.028 L vs. 0.230 ± 0.017 L (± SE), <italic>p</italic> &lt; 0.006), and a trend toward increased VD/VT (0.35 ± 0.02 vs. 0.31 ± 0.02, <italic>p</italic> = 0.051). Area under the receiver operating characteristic (ROC) for VD was 0.81 (<italic>p</italic> &lt; 0.002), VD/VT was 0.68 (<italic>p</italic> = 0.077), and PETCO<sub>2</sub> was 0.52 (<italic>p</italic> = 0.840). Peak <inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mi mathvariant="normal">V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math></inline-formula>O<sub>2</sub>, <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mi mathvariant="normal">V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math></inline-formula>E/ <inline-formula id="inf4"><mml:math id="m4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mover accent="true"><mml:mi mathvariant="normal">V</mml:mi><mml:mo>˙</mml:mo></mml:mover></mml:mrow></mml:math></inline-formula>CO<sub>2</sub> slope, pulmonary function tests, 6-min walk distance and arterial blood gases were similar between the two groups. Intensive care unit and total hospital length of stay was significantly longer in those with PPC. In conclusion, preoperative resting VD was significantly elevated in patients with PPC. The observed increase in resting VD may be a potentially useful predictor of PPC in patients undergoing robotic-assisted lung resection surgery for suspected or biopsy-proven lung malignancy. A large prospective study is needed for confirmation.</p>