The short-term efficacy of high flow nasal oxygen therapy on cardiovascular surgical patients: a randomized crossover trial.

BACKGROUND: Oxygen therapy after extubation in the intensive care unit (ICU) is essential in order to maintain adequate oxygenation, especially in patients who have undertaken cardiovascular surgery. A Venturi mask (VM) has been routinely used as an oxygen therapy in the ICU. Recently, however, the high flow nasal cannula (HFNC) has become available, and this device can deliver up to 60 L/min of humidified oxygen. The aim of this study is to evaluate the short-term efficacy between HFNC and VM in cardiovascular surgical patients. METHODS: Forty patients who underwent cardiovascular surgery were randomized to either protocol A (HFNC followed by VM) or protocol B (VM followed by HFNC). After 60-minutes of use with either device, arterial blood gas analysis was performed, and the PaO2/FiO2 ratio (PFR) was calculated. Simultaneously, physiological data (respiratory rate, heart rate, mean arterial pressure, continuous cardiac index, and mixed venous oxygen saturation) were recorded. During this procedure, FiO2 and gas flow were maintained at a fixed rate. These variables were compared by using the paired t-test, and a p value < 0.05 was considered significant. All data were expressed as mean (standard deviation). RESULTS: Thirty-five patients (17 from protocol A and 18 from protocol B) were enrolled, and 5 patients were excluded from analysis in accordance with the exit criteria. PaO2 was significantly higher in the HFNC group than in the VM group [101.7 (25.9) vs. 91.8 (23.0), mean difference 9.87 (18.5), 95% confidence interval 3.5 to 16.2, p = 0.003]. Moreover, PFR was significantly higher in the HFNC group than in the VM group [265.9 (81.4) vs. 238.7 (68.5), p = 0.002]. Moreover, PaCO2 was significantly lower in the HFNC group than in the VM group [33.8 (3.5) vs. 34.7 (2.9), p = 0.033]. The respiratory rate was significantly lower in the HFNC group than in the VM group [18 (4) vs. 21 (4), p = 0.006], and no significant differences were seen in any of the other parameters. CONCLUSIONS: Compared to VM, HFNC ameliorated oxygenation function and decreased patients' effort in breathing. The hemodynamic state did not differ between HFNC and VM. Therefore, HFNC can be used safely in cardiovascular surgical patients. TRIAL REGISTRATION: This trial was registered with the UMIN Clinical Trials Registry (ID UMIN000016572).

Evaluation of alveolar recruitment maneuver on respiratory resistance during general anesthesia: a prospective observational study.

BACKGROUND: Alveolar recruitment maneuvers enable easily reopening nonaerated lung regions via a transient elevation in transpulmonary pressure. To evaluate the effect of these maneuvers on respiratory resistance, we used an oscillatory technique during mechanical ventilation. This study was conducted to assess the effect of the alveolar recruitment maneuvers on respiratory resistance under routine anesthesia. We hypothesized that respiratory resistance at 5 Hz (R5) after the maneuver would be decreased after the lung aeration. METHODS: After receiving the ethics committee's approval, we enrolled 33 patients who were classified with an American Society of Anesthesiologists physical status of 1, 2 or 3 and were undergoing general anesthesia for transurethral resection of a bladder tumor within a 12-month period from 2017 to 2018. The recruitment maneuver was performed 30 min after endotracheal intubation. The maneuver consisted of sustained manual inflation of the anesthesia reservoir bag to a peak inspiratory pressure of 40 cmH2O for 15 s, including 5 s of gradually increasing the peak inspiratory pressure. Respiratory resistance was measured using the forced oscillation technique before and after the maneuver, and the mean R5 was calculated during the expiratory phase. The respiratory resistance and ventilator parameter results were analyzed using paired Student's t-tests, and p < 0.05 was considered statistically significant. RESULTS: We analyzed 31 patients (25 men and 6 women). R5 was 7.3 ± 1.6 cmH2O/L/sec before the recruitment maneuver during mechanical ventilation and was significantly decreased to 6.4 ± 1.7 cmH2O/L/sec after the maneuver. Peak inspiratory pressure and plateau pressure were significantly decreased, and pulmonary compliance was increased, although the values were not clinically relevant. CONCLUSION: The recruitment maneuver decreased respiratory resistance and increased lung compliance during mechanical ventilation. TRIAL REGISTRATION: Name of registry: Japan Medical Association Center for Clinical Trials. TRIAL REGISTRATION NUMBER: reference JMA-IIA00136. Date of registration: 2 September 2013. URL of trial registry record: https://dbcentre3.jmacct.med.or.jp/JMACTR/App/JMACTRE02_04/JMACTRE02_04.aspx?kbn=3&seqno=3582.

[A Difficult Airway after Anesthetic Induction in a Patient with Masticatory Muscle Tendon-Aponeurosis Hyperplasia].

We present a case of masticatory muscle tendon- aponeurosis hyperplasia in a patient who underwent general anesthesia for gynecologic surgery. The patient's square-shaped mandible was noticed during preoperative assessment by an anesthesiologist. Further investigation revealed masticatory muscle tendon- aponeurosis hyperplasia. Anesthetic induction agents were administered, and facemask ventilation was initi- ated easily. As the anesthesiologist had predicted, the patient's mouth opening was reduced after administration of muscle relaxants, and keeping her mouth open was more difficult than when she was conscious. Nasotracheal intubation was performed successfully using a bronchoscope. Patients with muscle tendon- aponeurosis hyperplasia do not generally have associated pain, and do not know that they have a limited mouth opening. They are therefore sometimes unaware that they have the condition. Anesthesiologists need to predict that airway intubation will be difficult when the patient has a limited mouth opening associated with a square-shaped mandible.

Perioperative evaluation of respiratory impedance using the forced oscillation technique: a prospective observational study.

BACKGROUND: Intravascular fluid shifts, mechanical ventilation and inhalational anesthetic drugs may contribute to intraoperative lung injury. This prospective observational study measured the changes in respiratory impedance resulting from inhalational anesthesia and mechanical ventilation in adults undergoing transurethral resection of bladder tumors. The components of respiratory impedance (resistance and reactance) were measured using the forced oscillation technique (FOT). METHODS: Respiratory resistance at 5 Hz (R5) and 20 Hz (R20), respiratory reactance at 5 Hz (X5), resonant frequency (Fres) and area of low reactance (ALX) were measured before and immediately after surgery in 30 adults. In addition, preoperative vital capacity (VC), forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1.0) were evaluated using spirometry. All patients were intubated with an endotracheal tube and were mechanically ventilated, with anesthesia maintained with sevoflurane. Pre- and postoperative FOT measurements were compared using Wilcoxon paired rank tests, and the relationships between FOT measurements and preoperative spirometry findings were determined by Spearman's rank correlation analysis. RESULTS: Twenty-six patients were included in the final analysis: postoperative FOT could not be performed in four because of postoperative restlessness or nausea. The mean duration of surgery was 47 min. All components of respiratory resistance deteriorated significantly over the course of surgery, with median increases in R5, R20, and R5-R20 of 1.67 cmH2O/L/s (p < 0.0001), 1.28 cmH2O/L/s (p < 0.0001) and 0.46 cmH2O/L/s (p = 0.0004), respectively. The components of respiratory reactance also deteriorated significantly, with X5 decreasing 1.7 cmH2O/L/s (p < 0.0001), Fres increasing 5.57 Hz (p < 0.0001) and ALX increasing 10.51 cmH2O/L/s (p < 0.0001). There were statistically significant and directly proportional relationships between pre- and postoperative X5 and %VC, %FEV1.0 and %FVC, with inverse relationships between pre- and postoperative Fres and ALX. CONCLUSIONS: All components measured by FOT deteriorated significantly after a relatively short period of general anesthesia and mechanical ventilation. All components of resistance increased. Of the reactance components, X5 decreased and Fres and ALX increased. Pre- and postoperative respiratory reactance correlated with parameters measured by spirometry. TRIAL REGISTRATION: JMA-IIA00136 .

[The Effects of Tracheal Suction on Respiratory Impedance].

BACKGROUND: Tracheal suctioning is performed just before extubation to remove sputum from the trachea. Although it is an invasive procedure, its adverse effect on the airway has not been investigated because this is difficult to achieve using conventional tests or monitoring. We performed a study using the forced oscillation technique to investigate whether tracheal suctioning affects respiratory impedance (consisting of respiratory resistance and respiratory reactance). METHODS: This prospective observational study was conducted in 43 patients undergoing transurethral resection of bladder tumors under general anesthesia. Respiratory impedance (R5, R20, and X5) was measured the day before surgery and just after surgery. R5 and R20 are representative values of respiratory resistance, while X5 is representative of respiratory reactance. Participants were divided into two groups: those with or without tracheal suctioning. RESULTS: There were no significant differences in patient backgrounds or preoperative respiratory impedance parameters. In the suctioning group, post- operative R5 and R20 were significantly higher than in the non-suctioning group (P=0.002 and 0.063, respec- tively). There was no significant difference in postop- erative X5 between the two groups. CONCLUSIONS: Tracheal suctioning caused an increase in respiratory resistance in this cohort of patients, sug- gesting that unnecessary suctioning should be avoided during surgery.

[Successful double-lumen tube insertion using Pentax-AWS Airwayscope with an infant-sized intlock in a rheumatoid arthritis patient with restricted mouth opening and head tilting].

Successful tracheal intubation with a double-lumen tube was achieved using Pentax-AWS Airwayscope (AWS) with an infant-size Intlock in a patient with restricted mouth opening and head tilting. A 78-year-old woman with rheumatoid arthritis was scheduled for extended thymectomy under general anesthesia, with anticipated difficult airway. Sufficient mask ventilation with the jaw-thrust maneuver was achieved. The laryngoscopic view was defined as grade III (Cormack & Lehane's classification)with Macintosh laryngoscope. The AWS with an infant-size Intlock facilitated visualization of the glottis, leading to a successful placement of a 32-Fr double-lumen tube under the guidance of the AWS image. Double-lumen tube insertion assisted by the AWS with an infant-size Intlock may be useful for difficult airway management in patients with restricted mouth opening and head tilting.

[Intubation using the Pentax-AWS Airwayscope with an infant-size Intlock in a patient with increased intracranial pressure due to acute hydrocephalus].

We report our experience with the Pentax-AWS Airwayscope with an infant-size Intlock (AWS-I) in a patient with increased intracranial pressure due to acute hydrocephalus. A 12-month-old female infant with increased intracranial pressure due to acute hydrocephalus was scheduled to undergo emergent ventriculoperitoneal shunting under general anesthesia. She had a clonic convulsion and was sedated with midazolam. As her head was enlarged, head-tilting was difficult. Tracheal intubation while preventing an intracranial pressure increase was needed. After induction of general anesthesia with thiamylal and fentanyl the AWS-I was inserted to obtain a laryngoscopic view without excessive force. Under AWS observation, tracheal intubation was uneventful, and no vital sign change was observed.

[One-lung ventilation using dexmedetomidine in an emphysema patient with pneumothorax due to metastatic lung cancer].

We report a case of double-lumen tube intubation and intraoperative one-lung ventilation under spontaneous breathing with continuous dexmedetomidine administration. A 61-year-old man developed pneumothorax due to multiple metastatic cancer, had multiple bilateral bullae, and underwent bullae resection under general anesthesia. An epidural catheter was placed at T8-9. Under dexmedetomidine sedation and regional anesthesia with lidocaine, a double-lumen tube was inserted with a Macintosh laryngoscope. The patient was under one-lung ventilation with spontaneous breathing during the operation. There were no complications from one-lung ventilation and the patient was extubated in the operating room. One-lung ventilation, which preserves spontaneous breathing, under dexmedetomidine sedation is considered effective for preventing barotrauma in patients with multiple metastatic cancer.

[Successful one-lobe ventilation in a patient combined with multiple bulla and interstitial pneumonia].

Respiratory management of interstitial pneumonia during general anesthesia is challenging, especially for one-lung ventilation. We report the successful left-side one-lung ventilation after left lower lobectomy. A 79-year-old man with interstitial pneumonia was scheduled for right side bulla resection. After epidural anesthesia at T8-9, under dexmedetomidine and propofol sedation and regional anesthesia with lidocaine, a double-lumen tube was inserted with a Macintosh laryngoscope preserving spontaneous breathing. Next, we continuously administered propofol at 1.5-2.0 microg x ml(-1) in target-controlled infusion manner, 0.8 microg x kg(-1) x hr(-1) dexmedetomidine and 50 mg x hr(-1) aminophylline for minimizing hypoxic vasocontriction. The bispectral index was maintained within 40-60 by titrating the dose of propofol. Analgesia was performed with epidural 100 microg fentalyl and 6 ml of 0.375% ropivacaine administration. The lowest Spo2 during one-lobe ventilation was 88% which recovered to 97% by oxygen administration to right lung with no pressure. We could keep about 3-4 l of minute volume and accumulation of Paco2 was acceptable. The patient was under one-lobe (left upper lobe) ventilation with spontaneous breathing during the operation. Open bulla resection was performed uneventfully. There were no complications from one-lobe ventilation and the patient was extubated in the operating room. One-lung ventilation, which preserves spontaneous breathing is considered effective for preventing barotrauma in patients with interstitial pneumonia. Dexmedetomidine as well as propofol or aminophylline may be effective avoiding hypoxic vasoconstriction. Furthermore, we could perform one-lobe ventilation with left-upper lobe with maintaining sufficient oxygenation and ventilation.

[Successful double-lumen endotracheal tube exchange with a soft-tipped extra firm exchange catheter in a patient with severe subcutaneous emphysema].

We report a case of successful double-lumen endotracheal tube exchange with a soft-tipped extra firm exchange catheter in a patient with severe subcutaneous emphysema. A 70-year-old man underwent right lower lobectomy for primary lung cancer under general anesthesia. He developed pneumothorax on postoperative day (POD) 14, which led to subcutaneous emphysema. An emergent operation was performed on POD20 to close the pulmonary fistula under general anesthesia with a single-lumen endotracheal tube and bronchial blocker. Subcutaneous emphysema became worse and pharyngeal emphysema was also suspected; re-operation to close the pulmonary or bronchial fistula was planned. We decided to place a double-lumen tube to precisely detect the fistula. Under the guide of a Pentax-AWS Airwayscope, the single-lumen endotracheal tube was exchanged uneventfully to a 35 Fr double-lumen endotracheal tube with a 110 cm soft-tipped extra firm exchange catheter. The fistula was detected by a leak test and the operation was performed uneventfully, leading to improvement of subcutaneous emphysema.

[Discrepancy in the length of smoking cessation between surgeon's and anesthesiologist's records in relation to hypoxia during one-lung ventilation].

BACKGROUND: Smoking cessation before pulmonary surgery is essential for preventing respiratory complications associated with operation and anesthesia. We compared patients' smoking habits and length of smoking cessation based on respiratory surgeon's and anesthesiologist's records. METHODS: We retrospectively surveyed 68 patients who underwent elective operation under one-lung ventilation (OLV) with respect to the Brinkmann index, smoking cessation period, and incidence of hypoxia during OLV. RESULTS: Of the 68 patients, 38 had a history of smoking, with no difference in the Brinkmann index according to respiratory surgeons and anesthesiologists. Of the 38 patients, 6 had inconsistent records regarding the length of smoking cessation. The smoking cessation period was significantly longer according to respiratory surgeons (17.5 days (median)) compared to that according to anesthesiologists [2.0 days (median), P < 0.05). The incidence of hypoxia (SP(O2) < 90%) was significantly higher in these patients (4 of 6), relative to those with no discrepancy (2 of 32, P < 0.05). CONCLUSIONS: Accurate information regarding the length of smoking cessation before surgery is difficult to obtain. The incidence of hypoxia during OLV was significantly higher in patients with a discrepancy regarding the length of smoking cessation between respiratory surgeon's and anesthesiologist's records.

[Successful tracheal intubation through the air-Q intubating laryngeal airway in a patient with severe pharyngeal edema].

A 68-year-old man was diagnosed with severe pharyngeal edema after neck lymph node dissection for cancer of the external ear canal. He was scheduled for an emergency tracheotomy, but preoperative fiberoptic laryngoscopy revealed airway and glottic obstruction due to severe pharyngeal edema. As difficult mask ventilation and tracheal intubation were anticipated, intubation under spontaneous ventilation was performed to avoid a "can't ventilate, can't intubate" situation. The first attempt to intubate the patient using the Pentax-AWS Airwayscope with a thin Intlock resulted in failure due to hindered visualization of the glottis. Therefore, a size 3.5 air-Q intubating laryngeal airway was inserted using a bronchofiberscope to perform tracheal intubation through a laryngeal mask. Successful tracheal intubation was achieved while maintaining spontaneous ventilation. The air-Q intubating laryngeal airway can be useful in the setting of anticipated difficult mask ventilation and tracheal intubation, as in the case of severe pharyngeal edema.

[General anesthesia in a orthopedic case with the Kommerell's diverticulum of right-sided aortic arch diagnosed on preoperative examination].

Kommerell's diverticulum is a rare anomaly of the aortic arch. A 59-year-old man was scheduled for open reduction and internal fixation of his right proximal tibial fracture under general anesthesia. We diagnosed right-sided aortic arch by the chest X-ray and thoracic computed tomography. His trachea and esophagus were compressed by the aortic arch. He had complained of no dyspnea or dysphagia. Respiratory difficulty might be caused by muscle relaxants, intermittent positive pressure ventilation, change of intrathoracic pressure, postural change and overloaded infusion during general anesthesia in a case of right-sided aortic arch. We performed lumbar epidural anesthesia and inserted an i-gel after general anesthesia induction preserving spontaneous respiration in preparation for controlled ventilation or tracheal intubation via an i-gel. We could accomplish the operation uneventfully and he was discharged on POD 53. A supraglottic airway such as an i-gel was a useful device in the present case of right-sided aortic arch with Kommerell's diverticulum.

Severe dysautonomia in glycine receptor antibody-positive progressive encephalomyelitis with rigidity and myoclonus (PERM): A case report.

Progressive encephalomyelitis with rigidity and myoclonus (PERM) is a severe form of stiff-person spectrum disorder. We report a 59-year-old man who presented with progressive encephalomyelitis causing diplopia, bulbar palsy, severe dysautonomia, followed by stiffness and myoclonic cluster. Laboratory tests showed mild pleocytosis, with markedly elevated plasma levels of norepinephrine, epinephrine, and arginine vasopressin. Glycine-receptor antibodies were identified in both serum and CSF. Despite a poor response to methylprednisolone, immunoglobulins, and plasma exchange, α-blocker stabilized dysautonomia. Dysautonomia is presumed to be due to antibody-mediated disinhibited sympathetic hyperactivity; however, this case suggests that concomitant use of α-blocker with immunotherapy may ameliorate dysautonomia.

Nemaline Myopathy Initially Diagnosed as Right Heart Failure with Type 2 Respiratory Failure.

Nemaline myopathy (NM) is a rare muscle disease with various clinical types. In some cases, NM can lead to type 2 respiratory failure and right heart failure. We herein report a patient with congenital NM with nebulin gene mutation who presented with acute right heart failure and type 2 respiratory failure due to respiratory muscle paralysis after upper respiratory tract infection, needing a permanent ventilator for assistance. However, the limb and trunk muscle strengths were within normal limits. This case showed that NM should be considered as a cause of right heart failure and type 2 respiratory failure.

Establishment of a mouse model for post-inflammatory hyperpigmentation.

Post-inflammatory hyperpigmentation (PIH) is a common cutaneous condition that can cause a disfigured appearance. However, the pathophysiology of PIH remains poorly understood, at least in part, because an appropriate animal model for research has not been established. In order to analyze the pathomechanism of PIH, we successfully induced PIH in a hairless version of transgenic mice (hk14-SCF Tg/HRM) that have a human-type epidermis containing melanin by repeated hapten application of 2,4-dinitrofluorobenzene. Histopathologic observation showed epidermal hyperplasia, predominant infiltrations of inflammatory cells, and melanin-containing cells in the dermis just after elicitation of the atopic dermatitis-like condition. At week 2, the findings were similar to the characteristics of PIH, that is, an increase of melanin without spongiosis or liquid degeneration in the epidermis and an increase in dermal melanophages. Dynamic analysis of melanin showed that the melanin in the dermis remained for a longer duration than in the epidermis. Furthermore, immunohistochemical staining revealed that the majority of cells containing melanin were positive for the anti-CD68 antibody, but negative for the anti-F4/80 antibody. These data suggest that novel treatments of PIH should be targeted against macrophages and should eventually lead to the development of new treatment modalities.

Efficacy of Goreisan in Preventing Transurethral Resection Syndrome in Transurethral Resection of the Prostate: A Randomized-Controlled Study.

Objectives: Nonconductive irrigation fluids used during transurethral resection (TUR) of the prostate can cause fluid overload and dilutional hyponatremia. TUR syndrome is generally defined as serum sodium at or below 125 mmol/L with cardiovascular and neurologic symptoms. The aim of this study was to evaluate the effects of Goreisan, a traditional Japanese Kampo medicine, on serum sodium levels and the occurrence of TUR syndrome in patients undergoing TUR of the prostate. Design: This was a randomized-controlled trial. Settings/Location: This trial was conducted at the Osaka Medical College Hospital and Keneikai Sanko Hospital. Subjects: Fifty patients scheduled for TUR of the prostate were included. Interventions: Patients in the Goreisan group (n = 23) received 2.5 g Goreisan orally on the night before surgery and on the morning of surgery. The control group (n = 27) did not receive Goreisan. Surgical procedures, perioperative management, and patient monitoring were otherwise the same in both groups. Outcome Measures: The primary outcome was occurrence of TUR syndrome. The secondary outcome was serum sodium level. Results: Serum sodium remained above 125 mmol/L in all patients, so none of the patients met the criteria for TUR syndrome. However, the Goreisan group had significantly higher intraoperative sodium levels (p < 0.001) and significantly higher intraoperative (p = 0.008) and postoperative (p = 0.02) hemoglobin levels than the control group. Conclusions: These findings indicate that preoperative Goreisan administration can help maintain serum sodium levels in patients undergoing TUR of the prostate.

Factors Associated with Poor Satisfaction with Anesthesia in Patients Who Had Previous Surgery: A Retrospective Study.

BACKGROUND: As most studies investigating patient satisfaction with anesthesia have some bias, previous results may underrepresent the true level of dissatisfaction with anesthesia. OBJECTIVES: This study aimed to identify factors associated with patient satisfaction with anesthesia. METHODS: Data from patients aged ≥ 20 years who had previous surgery and were scheduled for additional surgery were obtained retrospectively through preoperative interviews conducted. Informed consent for anesthesia was obtained by an anesthesiologist prior to the additional surgery. The patients were assigned to one of four anesthesia satisfaction levels, then were categorized into two groups; a high satisfaction group and a low satisfaction group. After comparing parameters between the two groups, logistic regression analysis was performed to identify factors that were negatively associated with satisfaction with anesthesia. RESULTS: Of 478 patients interviewed subjects, 469 patients were analyzed. Five individuals were excluded because they were unable to provide informed consent, and four subjects were excluded because they were aged < 10 years at the time of their previous surgery. Age < 65 years, previous surgery for malignancy, female sex, estimated operation duration < 3 hours, and American Society of Anesthesiologists Physical Status score 1 or 2 were included in a logistic regression analysis. Age < 65 years, previous surgery for malignancy, and female sex were predictive of poor patient satisfaction with anesthesia. Reasons for poor satisfaction with anesthesia included postoperative shivering and chills, fear of surgery, ineffective spinal anesthesia, and postoperative surgery-related pain. Of the patients awaiting surgery for malignancy, 57.3% had previous surgery for malignancy. CONCLUSIONS: Age < 65 years, previous surgery for malignancy, and female sex were negatively associated with patient satisfaction with anesthesia. These factors should be considered when preparing patients for future procedures to improve postoperative patient satisfaction.

The Effects of Endotracheal Tube and i-gel® Supraglottic Airway Device on Respiratory Impedance: A Prospective Observational Study.

BACKGROUND: The forced oscillation technique (FOT) is a non-invasive means of measuring respiratory resistance and reactance. We tested our hypothesis that endotracheal intubation would cause more substantial preoperative increases in FOT parameters than a supraglottic airway device (SGD). METHODS: Forty patients requiring general anesthesia and mechanical ventilation for transurethral bladder tumor resection underwent spirometry the day before surgery. Forced oscillation was measured using a MostGraph-01 device the day before surgery and immediately after removal of the airway adjunct. Changes in respiratory resistance and reactance were compared between those intubated and those who used SGD. RESULTS: The trachea was intubated in 23 patients and SGD was used in the remaining 17 patients. Both airway adjuncts caused significant increases in preoperative respiratory resistance and reactance; however, the magnitude of the changes was significantly greater in the intubated patients. CONCLUSIONS: The SGD appears to cause less pulmonary injury than tracheal intubation. Further study is needed to illuminate the influence of mechanical ventilation, and longer-term consequences and clinical significance of the changes we found in this study. Spontaneous ventilation through an SGD may be preferable in patients with severe respiratory disease.