Preoperative sleep-disordered breathing and craniofacial abnormalities are risk factors for postoperative sleep-disordered breathing in patients undergoing skin-flap oropharyngeal reconstruction surgery for oral cavity cancer: a prospective case-control study.

PURPOSE: After oropharyngeal reconstruction surgery, excessive flap volume within the oral cavity may increase the risk of pharyngeal obstruction during sleep. This prospective observational study aimed to test a hypothesis that the skin-flap oropharyngeal reconstructive surgery increases nocturnal apnea-hypopnea index (nAHI, primary variable) after surgery. METHODS: Adult patients undergoing oropharyngeal reconstruction surgery participated in this study. The hypothesis was tested by comparing the results of portable type 4 sleep study and craniofacial assessments with lateral head and neck computed tomography scout image before and after surgery. Multiple linear regression analyses were performed to identify predictors for nAHI increase after the surgery. RESULTS: In 15 patients, a postoperative sleep study was performed at 41 (27, 59) (median (IQR)) days after the surgery. nAHI did not increase after the surgery (mean (95% CI), 13.0 (7.2 to 18.7) to 18.4 (10.2 to 26.6) events.hour-1, p = 0.277), while apnea index significantly increased after the surgery (p = 0.026). Use of the pedicle flap for the oropharyngeal reconstruction (p = 0.051), small mandible (p = 0.008), longer lower face (0.005), and larger tongue size (p = 0.008) were independent predictors for worsening of nAHI after surgery. Hospital stay was significantly longer in patients with the pedicle flap (n = 8) than in those with the free flap (n = 7) (p = 0.014), and the period of hospital stay was directly associated with increase of nAHI after surgery (r = 0.788, p < 0.001, n = 15). CONCLUSIONS: Oropharyngeal reconstruction surgery worsens sleep-disordered breathing in some patients with craniofacial and surgical risk factors. TRIAL REGISTRATION: UMIN Clinical Trial Registry (UMIN000036260, March 22, 2019), https://rctportal.niph.go.jp/s/detail/um?trial_id=UMIN000036260.

Assessments of perioperative respiratory pattern with non-contact vital sign monitor in children undergoing minor surgery: a prospective observational study.

PURPOSE: Nurses routinely assess respiration of hospitalized children; however, respiratory rate measurements are technically difficult due to rapid and small chest wall movements. The aim of this study is to reveal the respiratory status of small children undergoing minor surgery with load cells placed under the bed legs, and to test the hypothesis that respiratory rate (primary variable) is slower immediately after arrival to the ward and recovers in 2 h. METHODS: Continuous recordings of the load cell signals were performed and stable respiratory waves within the 10 discriminative perioperative timepoints were used for respiratory rate measurements. Apnea frequencies were calculated at pre and postoperative nights and 2 h immediately after returning to the ward after surgery. RESULTS: Continuous recordings of the load cell signals were successfully performed in 18 children (13 to 119 months). Respiratory waves were appraisable for more than 70% of nighttime period and 40% of immediate postoperative period. There were no statistically significant differences of respiratory rate in any timepoint comparisons (p = 0.448), thereby not supporting the study hypothesis. Respiratory rates changed more than 5 breaths per minute postoperatively in 5 out of 18 children (28%) while doses of fentanyl alone did not explain the changes. Apnea frequencies significantly decreased 2 h immediately after returning to the ward and during the operative night compared to the preoperative night. CONCLUSION: Respiratory signal extracted from load cell sensors under the bed legs successfully revealed various postoperative respiratory pattern change in small children undergoing minor surgery. CLINICAL TRAIL REGISTRATION: UMIN (University Hospital Information Network) Clinical Registry: UMIN000045579 ( https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000052039 ).

Continuous monitoring of activity and vital signs with load cells under the bed legs in advanced cancer patients: a prospective exploratory observational study-can it represent performance status?

BACKGROUND: Activity levels of patients often scaled as performance status (PS) is the most important scale in oncology populations for treatment decisions and prognosis prediction. However, it is usually subjective and open to bias. The need for more objective and reliable assessment tools is mandatory for safe and effective oncology practice. To investigate the reliability of continuous vital and activity evaluation monitored by bed sensor systems in advanced cancer patients, we conducted a cohort pilot study in hospitalized cancer patients under several PS conditions. METHODS: Adult patients, either admitted in the oncology department or palliative care unit, were enrolled in the study after written informed consent. Continuous monitoring for 48 hours from the first night of admission was performed without any restrictions on the patients. Calculated acceleration of movement [activity index (ACI)], % time on bed and number of bed leave in an 8-hour period, as well as other vital signs were monitored. Analysis focused on change of PS to 3, a standard cut-off for curative cancer treatment and PS4, vital for prognosis assessment. RESULTS: Nineteen patients' data were analyzed. In PS4 palliative care patients, ACI was significantly low and % time on bed was high from PS3 palliative care patients. Instabilities of respiratory rate, respiratory tidal weight and heart rate were significantly higher in palliative care patients (PS3, PS4) compared with oncology patients (PS1, PS2). CONCLUSIONS: This result, though in need of larger trials, shows possibilities for continuous objective monitoring of patients in bed for PS assessment in advanced cancer patients.

Postoperative pain and quality of life after lung cancer surgery: a prospective observational study.

BACKGROUND: We aimed to identify the factors associated with postoperative pain, quality of life, and development of chronic pain after lung cancer surgery, including pain sensation threshold, fentanyl sensitivity, and surgical procedures. METHODS: We conducted a single-center prospective observational study involving lung cancer patients. Brief pain inventory, including nine items concerning pain and quality of life, was investigated at 1 week, 1 month, and 3 months postoperatively. Pain sensation threshold and fentanyl sensitivity were assessed preoperatively. RESULTS: Of the 146 patients who were enrolled, 100 who met our criteria were analyzed. Thoracoscopic surgery was performed in 42 patients and minimally invasive thoracotomy in 58 patients. Pain sensation threshold and fentanyl sensitivity were normally distributed among the patients and were not significantly associated with brief pain inventory scores at each postoperative time-point. The average pain score 1 week after the operation was significantly higher in the thoracotomy group than in the thoracoscopic surgery group (P<0.050). The worst pain scores did not differ between the groups at all the examination periods. Pain sensation threshold, fentanyl sensitivity, and surgical procedures were not related to the incidence of post-thoracotomy pain syndrome. CONCLUSIONS: Individual pain sensation threshold and fentanyl sensitivity were not associated with subjective postoperative pain score, quality of life score, or development of post-thoracotomy pain syndrome.

Hypercapnia versus normocapnia for emergence from desflurane anaesthesia: Single-blinded randomised controlled study.

BACKGROUND: Rapid emergence from general anaesthesia is desirable only if safety is not sacrificed. Mechanical hyperventilation during hypercapnia produced by carbon dioxide infusion into the inspired gas mixture or by rebreathing was reported to shorten emergence time from inhalation anaesthesia. OBJECTIVES: To test the hypothesis that hypercapnia produced by hypoventilation before desflurane cessation shortens emergence time from general anaesthesia (primary hypothesis) and reduces undesirable cardiorespiratory events. DESIGN: A single-blinded randomised controlled study. SETTING: A single university hospital. PATIENTS: Fifty adult patients undergoing elective abdominal surgery under general anaesthesia using desflurane inhalation and intra-operative epidural anaesthesia. INTERVENTION: The patients were randomly assigned to either the normocapnia or hypercapnia group. MAIN OUTCOME MEASURES: Emergence time from desflurane anaesthesia and comparison of the incidence of 11 predefined undesirable cardiorespiratory events during and after emergence from anaesthesia between the groups. RESULTS: Forty-six patients were included in the analysis. End-tidal carbon dioxide concentrations at cessation of desflurane were 35 ±â€Š6 mmHg (mean ±â€ŠSD) and 52 ±â€Š6 mmHg in normocapnia (n = 23) and hypercapnia groups (n = 23), respectively. Emergence time was significantly faster in the hypercapnia group than the normocapnia group: 9.4 ±â€Š2.4 min, hypercapnia: 5.5 ±â€Š2.6 min, (P < 0.001) with a difference of 3.8 min on average (95% CI: 2.4 to 5.3). Spontaneous breathing established before recovery of consciousness was more evident in hypercapnia patients (normocapnia: 13%, hypercapnia: 96%, P < 0.001). Hypercapnia patients had more episodes of bradypnoea and apnoea before emergence of consciousness. In contrast, after tracheal extubation, incidences of bradypnoea and hypopnoea were more common in the normocapnia group. Undesirable cardiovascular events were not common, and no group differences were observed during emergence and postextubation periods. CONCLUSION: Hypoventilation-induced hypercapnia before desflurane cessation shortens the emergence time without causing additional clinically significant undesirable events. TRIAL REGISTRATION: UMIN Clinical Trials Registry (UMIN000020143) https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&recptno=R000023266&language=E.

Recovery of lower oesophageal barrier function: a pilot study comparing a mixture of atropine and neostigmine and sugammadex: A randomised controlled pilot study.

BACKGROUND: The lower oesophageal sphincter (LOS) barrier serves to prevent regurgitation of gastric contents. Although general anaesthesia depresses its function, its recovery process during emergence from anaesthesia has not been systematically examined. OBJECTIVE: To explore whether recovery of lower oesophageal barrier function differed between patients receiving a mixture of 1 mg atropine and 2 mg neostigmine and those receiving 2 mg kg-1 sugammadex during emergence from anaesthesia. DESIGN: An unblinded randomised controlled pilot study. SETTING: A single university hospital from January 2016 to December 2018. PATIENTS: A total of 20 non-obese adult females undergoing minor surgery. INTERVENTION: The patients were randomly assigned to a group either receiving atropine and neostigmine or sugammadex for reversal of rocuronium. MAIN OUTCOME MEASURES: Through use of the high-resolution manometry technique, the lower oesophageal barrier pressure (PBAR: primary variable) defined as a pressure difference between pressures at the LOS and the stomach was measured at five distinguishable time points during emergence from total intravenous anaesthesia. A mixed effects model for repeated measures was used to test the hypothesis. RESULTS: In all patients baseline PBAR values were positive even under muscle paralysis and general anaesthesia before administration of reversal agents, and did not differ between the groups (P = 0.299). During recovery from muscle paralysis and general anaesthesia, PBAR (mean ±â€ŠSD) significantly increased (P = 0.004) from 17.0 ±â€Š2.9 to 21.0 ±â€Š5.0 mmHg in the atropine and neostigmine group (n = 8) and from 19.1 ±â€Š9.0 to 24.5 ±â€Š12.7 mmHg in the sugammadex group (n = 11). PBAR significantly increased immediately after return of consciousness in both groups, whereas return of muscle tone, lightening of anaesthesia and tracheal extubation did not change it. CONCLUSION: Recovery of the lower oesophageal barrier function does not differ between patients receiving either atropine and neostigmine or sugammadex and is completed after recovery of consciousness from general anaesthesia. TRIAL REGISTRATION: UMIN Clinical Trials Registry: UMIN000020500: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&recptno=R000023594&type=summary&language=E.

Effects of opioids on respiration assessed by a contact-free unconstraint respiratory monitor with load cells under the bed in patients with advanced cancer.

Nocturnal periodic breathing of chronic opioid users has been predominantly documented by the use of polysomnography. No previous studies have assessed the opioid effects of respiratory rhythms throughout the day without the use of physical restraint. We recently developed a contact-free unconstraint vital sign monitoring system with four load cells placed under the bed legs, which allows continuous measurements of respiratory change at the center of gravity on the bed. We aimed to reveal details of the patient's 24-h respiratory status under a monitoring system and to test the hypothesis that respiratory rhythm abnormalities are opioid dose-dependent and worsen during the night time. Continuous 48-h respiratory measurements were successfully performed in 51 patients with advanced cancer (12 opioid-free patients and 39 opioid-receiving patients). Medians of respiratory variables with minimal body movement artifacts were calculated for each 8-h split time period. Compared with opioid-free patients, opioid-receiving patients had slower respiratory rate with higher respiratory rate irregularity without changing tidal centroid shift regardless of the time period. Irregular ataxic breathing was only identified in opioid-receiving patients (33%, P = 0.023) whereas incidence rate of periodic breathing did not differ between the groups. Multivariate regression analyses revealed that opioid dose was an independent risk factor for occurrence of irregular breathing [odds ratio 1.81 (95% CI: 1.39-2.36), P < 0.001], and ataxic breathing [odds ratio 2.08 (95% CI: 1.60-2.71), P < 0.001]. Females developed the ataxic breathing at lower opioid dose compared with males. We conclude that respiratory rhythm irregularity is a predominant specific feature of opioid dose-dependent respiratory depression particularly in female patients with advanced cancer.NEW & NOTEWORTHY Through usage of a novel contact-free unconstraint vital sign monitoring system with four load cells placed under the bed legs allowing continuous measurements of respiratory changes of center of gravity on the bed, this study is the first to assess detailed respiratory characteristics throughout day and night periods without interference of daily activities in patients with advanced cancer receiving opioids. Respiratory rhythm irregularity is a predominant specific feature of opioid dose-dependent respiratory depression particularly in female patients with advanced cancer.

Propofol versus midazolam for sedation during radiofrequency ablation in patients with hepatocellular carcinoma.

BACKGROUND AND AIM: Standardization of the sedation protocol during radiofrequency ablation (RFA) in patients with hepatocellular carcinoma (HCC) is needed. This randomized, single-blind, investigator-initiated trial compared clinical outcomes during and after RFA using propofol and midazolam, respectively, in patients with HCC. METHODS: Few- and small-nodule HCC patients (≤3 nodules and ≤3 cm) were randomly assigned to either propofol or midazolam. Patient satisfaction was assessed using a 100-mm visual analog scale (VAS) (1 mm = not at all satisfied, 100 mm = completely satisfied). Sedation recovery rates 1, 2, 3, and 4 h after RFA were evaluated based on Modified Observer's Assessment of Alertness/Sedation (MOAA/S) scores; full recovery was defined as a MOAA/S score of 5. RESULTS: Between July 2013 and September 2017, 143 patients with HCC were enrolled, and 135 patients were randomly assigned to the treatment group. Compared with midazolam, propofol exhibited similar median procedural satisfaction (propofol: 73.1 mm, midazolam: 76.9 mm, P = 0.574). Recovery rates 1 and 2 h after RFA were higher in the propofol group than in the midazolam group. Meanwhile, recovery rates observed 3 and 4 h after RFA were similar in the two groups. The safety profiles during and after RFA were almost identical in the two groups. CONCLUSION: Patient satisfaction was almost identical in patients receiving propofol and midazolam sedation during RFA. Propofol sedation resulted in reduced recovery time compared with midazolam sedation in patients with HCC. The safety profiles of both propofol and midazolam sedation during and after RFA were acceptable.

A report of three cancer patients on opioid analgesia receiving spinal anesthesia: abrupt pain elimination without respiratory depression.

BACKGROUND: Complete removal of pain with regional anesthesia has been reported to cause fatal respiratory depression in opioid-dependent patients, which leads us to choose general anesthesia. We hereby report three cases of chronically opioid-treated cancer patients operated under spinal anesthesia without respiratory event. CASE PRESENTATION: Case 1: a 32-year-old female treated with high-dose morphine for her cancer pain was planned for cesarean section. Case 2: a 65-year-old female on moderate dose of oxycodone was planned for surgery of her femoral bone fracture. Case 3: a 65-year-old male on low-dose oxycodone was planned for intramedullary nailing for metastatic femoral bone tumor. In all three cases, spinal anesthesia was chosen. Continuous respiratory monitoring revealed no apnea or bradypnea. CONCLUSION: Spinal anesthesia was safely performed without respiratory depression in chronic opioid users for cancer pain.

Low-dose of olanzapine has ameliorating effects on cancer-related anorexia.

BACKGROUND: Olanzapine (OLZ) has become well-known for its antiemetic effects on chemotherapy-induced nausea and vomiting. However, it remains unclear whether OLZ also has efficacy for treating cancer-related anorexia. This study, therefore, retrospectively examined whether or not OLZ administration affects the food intake in anorexic cancer patients who exhibit neither nausea nor vomiting. METHODS: Eighty patients prescribed OLZ were extracted from 951 inpatients who consulted with our palliative care team at Chiba University Hospital from April 2008 to March 2016. Their food intake described on a nursing record was compared before and after OLZ administration. The observation period was 3 days before and after the start of OLZ treatment, because most inpatients whose food intake increased were discharged in 3 days. RESULTS: In those 80 patients, the average dose of OLZ for 3 days was 2.28±0.87 (mean±SD) mg/day. First, the food intake in 80 patients was significantly higher after than before starting OLZ, and the relative change in food intake was 149% on average (P<0.0001, Student's paired t-test). Second, OLZ increased the food intake even in 40 out of 80 patients without nausea or vomiting, and the relative change in food intake was 143% on average (P<0.001, Student's paired t-test). Third, the average food intake increased in 13 out of 40 patients who were prescribed 1.5 mg/day of OLZ, and the relative change in food intake was 124% on average (P<0.01, Student's paired t-test). There was no significant difference in food intake between a dose of 1.5 mg/day and a dose of >1.5 mg/day of OLZ (P=0.18, Welch's unpaired t-test). CONCLUSION: We have herein reported OLZ's ameliorating efficacy in cancer-related anorexia at the low dose of 1.5 mg/day. Although our study has many limitations, low-dose OLZ can be a promising treatment for cancer-related anorexia.

New approach to relieving pain and distress during high-dose-rate intracavitary irradiation for cervical cancer.

BACKGROUND AND PURPOSE: To relieve the pain and distress experienced by women who undergo high-dose-rate intracavitary radiotherapy (HDR-ICRT) for cervical cancer and to improve the current status of gynecologic brachytherapy in Japan, a new intravenous anesthetic protocol involving the administration of a combination of propofol and ketamine was developed. The primary aim of this study is to investigate the efficacy and safety of this new anesthetic protocol during HDR-ICRT for cervical cancer. METHODS AND MATERIALS: All the patients who were diagnosed with cervical cancer between December 2008 and February 2011, treated with three-channel brachytherapy and subjected to the new sedation protocol, were evaluated. A visual analog scale (VAS) was used to assess the pain during brachytherapy, and we collected VAS score at the next HDR-ICRT. Toxicities were graded using the Common Toxicity Criteria, version 3. RESULTS: A total of 178 sessions of HDR-ICRT were delivered to 57 patients. The patients' median VAS pain score was 0 (range, 0-10). The most frequent side effect was Grade 1-2 nausea, which occurred in 33 sessions (34%). However, 13 of 14 patients received concurrent cisplatin chemotherapy. None of the patients experienced Grade 3 or 4 adverse events. CONCLUSIONS: We have demonstrated that our new intravenous anesthetic protocol produces appropriate effects and can be performed by radiation oncologists who were required to finish training in basic life support and the cooperative system of emergency according to in-house guideline.

Assessment of reasons for referral and activities of hospital palliative care teams using a standard format: a multicenter 1000 case description.

CONTEXT: The many benefits of hospital palliative care teams (PCTs) are well known. However, their specific activities have not been fully clarified, and no standardized methods for reporting PCT activities are available. OBJECTIVES: The aim of this study was to investigate, through the use of a standard format, the activities performed by hospital PCTs in Japan. METHODS: This was a prospective observational study. A total of 21 hospital PCTs were included in this study, and each recruited approximately 50 consecutively referred patients. Participating PCTs filled in a standard form for reporting activities. RESULTS: We obtained data from 1055 patients who were referred to PCTs. Of the 1055 patients, 1005 patients (95%) had cancer. The median number of reasons for referral and problems identified by PCTs was two (0-22) and four (0-18), respectively. The two major reasons for referral were pain (63%) and anxiety/depression/grief/emotional burden (22%). The major recommendations were pharmacological treatment (74%), care for the patient's physical symptoms (49%), and support for patient's decision making (38%). The major activities performed by the PCTs were comprehensive assessment (90%), care for the patient's physical symptoms (77%), and pharmacological treatment (74%). CONCLUSION: The components of hospital PCT activities were successfully measured using the Standard Format for Reporting Hospital PCT Activity. The results of this study and the format for reporting hospital PCT activity could be effective in improving hospital PCT practice and for the education of new hospital PCT members.

Potential utility of peripherally applied loperamide in oral chronic graft-versus-host disease related pain.

Four patients with oral chronic graft-versus-host disease pain were treated with loperamide oral-rinse solution. Two-week continued use of the drug solution improved not only the pain scores but also the pain-causing disabilities associated with eating, drinking and sleeping, with no noticeable side effects. Current results suggest that the mu-opioid agonist, loperamide, has a potential analgesic effect that could be clinically used as a peripheral analgesic agent for stomatitis pain. However, these observations will need to be further confirmed in a randomized-controlled trial.

[Assessment of pain].

Assessment of patient's pain is crucial to effective pain management. It requires not only the knowledge of pain scale, but also a closely listening ear and a sharp eye. It also needs to be constantly re-evaluated by the healthcare team. While taking pain history, encourage the patient to do most of the talking and explain the pain characteristics with his/her own words. This is important when classifying the pain to predominantly nociceptive or neuropathic pain. Since cancer pain is not purely acute pain, assessment of pain needs not only to evaluate pain scores but also to evaluate patients' physical function and the impact of pain on his/her daily activities. Assessing secondary effect of pain, such as anxiety or financial worries, and reducing them may decrease the overall experience of pain.

Spinal and peripheral mu opioids and the development of secondary tactile allodynia after thermal injury.

UNLABELLED: Local thermal injury to the paw leads to an increased sensitivity to a noxious stimulus applied to the site (primary thermal hyperalgesia) and an increased sensitivity to tactile stimuli in skin sites adjacent to the primary injury (secondary tactile allodynia; 2 degrees TA). We sought to define the peripheral and spinal actions of mu opioids in regulating 2 degrees TA. First, a mild thermal injury was induced on one heel, producing 2 degrees TA. This 2 degrees TA was blocked by pretreatment, but not posttreatment, with a topical mu-opioid agonist, loperamide (1.7%-5%). Second, 2 degrees TA was blocked by intrathecal morphine (0.1-10 microg) pre- and postinjury. 2 degrees TA reappeared when systemic naloxone was given before, but not after, injury in intrathecal morphine-pretreated rats. Intrathecal remifentanil, a short-lasting mu-opioid agonist, infused periinjury (3 microg/min), did not block subsequent primary thermal hyperalgesia, but it produced a dose-dependent (0.3-3 microg/min) abolition of 2 degrees TA. Local tissue injury leads to 2 degrees TA by the activation of opiate-sensitive afferents and the initiation of a cascade that persists in the absence of that initiating injury-induced stimulus. IMPLICATIONS: Sensitivity to touch observed in areas adjacent to injury is blocked by opioids applied before, but not after, injury. This suggests that injury-activated opioid-sensitive fibers are responsible for sensitization and reveals a cascade that is diminished by pretreatment but not posttreatment, providing a rationale for adequate analgesia before injury (surgery) has occurred.

Vincristine-induced allodynia in the rat.

The aims of this study were two-fold: first, to simplify the method for creating a recently described neuropathic pain model in the rat, and second, to evaluate the effects of a number of drugs with analgesic or antihyperalgesic properties, in this model. Continuous intravenous vincristine infusion (1-100 microg kg(-1) day (-1)) for 14 days resulted in a dose dependent tactile allodynia (as measured by von Frey filaments) by 7 days at doses between 30 - 100 microg kg(-1) day (-1), with a hindlimb motor deficit observed at doses greater than 50 microg kg(-1) day (-1). No thermal hyperalgesia was observed. Systemic morphine, lidocaine, mexiletine and pregabalin (given intraperitoneally) produced significant reduction of the allodynia, while tetrodotoxin was without effect. Continuous intravenous infusion of vincristine in rats thus provides a reliable model of chemotherapy induced neuropathy which may be used in defining the mechanism and pharmacology of this clinically relevant condition.

Depression of sighing in the first three postoperative days with epidural morphine analgesia.

We have studied the effect of spontaneous sighs on maintaining arterial oxygenation in patients receiving epidural morphine for analgesia after upper abdominal surgery. Sixteen patients scheduled for elective gastrectomy were monitored continuously with pulse oximetry and respiratory inductive plethysmography (RIP) during one night preoperatively and for 60 h postoperatively with repeate arterial blood gas analysis. An average of 3.1±1.2 (±SD) sighs were observed per hour preoperatively during sleep while postoperative sighs were significantly depressed to an average less than one per hour throughout the 60 h of the monitoring period (P<0.05). Although postoperative Pao2 values were significantly lower than preoperative values, there was no correlation between the decreases in Pao2 values and number of sighs. Thus, it is unlikely that the long-term absence of spontaneous sighs observed may serve as a contributing factor for the long-lasting hypoxemia in the postoperative period.