Diaphragm Thickening Fraction as a Prognostic Imaging Marker for Postoperative Pulmonary Complications in Robot-Assisted Laparoscopic Prostatectomy Requiring the Trendelenburg Position and Pneumoperitoneum

Abstract

Background. Robot-assisted laparoscopic prostatectomy (RALP) frequently entails postoperative pulmonary complications (PPCs) due to the Trendelenburg position and pneumoperitoneum. Diaphragm thickening fraction (TF) as an imaging marker can offer the advantage of predicting respiratory outcomes. Therefore, we evaluated the effect of diaphragm TF on the occurrence of PPCs in RALP. Methods. We measured the preoperative thickness of the diaphragm at peak inspiration ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:msub> <a:mrow> <a:mi>T</a:mi> </a:mrow> <a:mrow> <a:mtext>pi</a:mtext> </a:mrow> </a:msub> </a:math> ) and end expiration ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:msub> <c:mrow> <c:mi>T</c:mi> </c:mrow> <c:mrow> <c:mtext>ee</c:mtext> </c:mrow> </c:msub> </c:math> ) using ultrasonography. Diaphragm TF was calculated as <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mtext>TF</e:mtext> <e:mo>=</e:mo> <e:mfenced open="(" close=")"> <e:mrow> <e:msub> <e:mrow> <e:mi>T</e:mi> </e:mrow> <e:mrow> <e:mtext>pi</e:mtext> </e:mrow> </e:msub> <e:mo>–</e:mo> <e:msub> <e:mrow> <e:mi>T</e:mi> </e:mrow> <e:mrow> <e:mtext>ee</e:mtext> </e:mrow> </e:msub> </e:mrow> </e:mfenced> <e:mo>/</e:mo> <e:msub> <e:mrow> <e:mi>T</e:mi> </e:mrow> <e:mrow> <e:mtext>ee</e:mtext> </e:mrow> </e:msub> </e:math> . A receiver operating characteristic (ROC) curve analysis of TF was performed. After dividing patients into two groups according to the optimal TF cut-off value, we compared the occurrence of PPCs between the groups. The predictivity of diaphragm TF for the occurrence of PPCs was evaluated. Results. Of 145 patients, 40 patients (27.6%) developed PPCs. Patients with PPCs had a significantly lower TF than those without PPCs ( <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M4"> <i:mn>0.31</i:mn> <i:mo>±</i:mo> <i:mn>0.09</i:mn> </i:math> vs. <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M5"> <k:mn>0.39</k:mn> <k:mo>±</k:mo> <k:mn>0.11</k:mn> </k:math> , <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" id="M6"> <m:mi>P</m:mi> <m:mo>&lt;</m:mo> <m:mn>0.001</m:mn> </m:math> ). In the ROC curve analysis, the optimal TF cut-off value was 0.28. The patients were divided into <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" id="M7"> <o:mtext>TF</o:mtext> <o:mo>≥</o:mo> <o:mn>0.28</o:mn> </o:math> group ( <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" id="M8"> <q:mi>n</q:mi> <q:mo>=</q:mo> <q:mn>114</q:mn> </q:math> ) and <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" id="M9"> <s:mtext>TF</s:mtext> <s:mo>&lt;</s:mo> <s:mn>0.28</s:mn> </s:math> group ( <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" id="M10"> <u:mi>n</u:mi> <u:mo>=</u:mo> <u:mn>31</u:mn> </u:math> ). The incidence of PPCs was significantly higher in the <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" id="M11"> <w:mtext>TF</w:mtext> <w:mo>&lt;</w:mo> <w:mn>0.28</w:mn> </w:math> group than in the <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" id="M12"> <y:mtext>TF</y:mtext> <y:mo>≥</y:mo> <y:mn>0.28</y:mn> </y:math> group (51.6% vs. 21.1%, <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" id="M13"> <ab:mi>P</ab:mi> <ab:mo>=</ab:mo> <ab:mn>0.001</ab:mn> </ab:math> ). Diaphragm <cb:math xmlns:cb="http://www.w3.org/1998/Math/MathML" id="M14"> <cb:mtext>TF</cb:mtext> <cb:mo>&lt;</cb:mo> <cb:mn>0.28</cb:mn> </cb:math> was associated with a higher incidence of PPCs than diaphragm <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" id="M15"> <eb:mtext>TF</eb:mtext> <eb:mo>≥</eb:mo> <eb:mn>0.28</eb:mn> </eb:math> ( <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" id="M16"> <gb:mtext>odds</gb:mtext> <gb:mtext> </gb:mtext> <gb:mtext>ratio</gb:mtext> <gb:mo>=</gb:mo> <gb:mn>4.534</gb:mn> </gb:math> , 95% confidence interval [1.763–11.658], <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" id="M17"> <ib:mi>P</ib:mi> <ib:mo>=</ib:mo> <ib:mn>0.002</ib:mn> </ib:math> ). Conc