Taiga Itagaki

Effect of High Flow Nasal Cannula on Thoraco-abdominal Synchrony in Adult Critically Ill Patients

BACKGROUND: High-flow nasal cannula (HFNC) creates positive oropharyngeal airway pressure and improves oxygenation. It remains unclear, however, whether HFNC improves thoraco-abdominal synchrony in patients with mild to moderate respiratory failure. Using respiratory inductive plethysmography, we investigated the effects of HFNC on thoraco-abdominal synchrony. METHODS: We studied 40 adult subjects requiring oxygen therapy in the ICU. Low-flow oxygen (up to 8 L/min) was administered via oronasal mask for 30 min, followed by HFNC at 30–50 L/min. Respiratory inductive plethysmography transducer bands were circumferentially placed: one around the rib cage, and one around the abdomen. We measured the movement of the rib-cage and abdomen, and used the sum signal to represent tidal volume (VT) during mask breathing, and at 30 min during HFNC. We calculated the ratio of maximum compartmental amplitude (MCA) to VT, and the phase angle. We assessed arterial blood gas and vital signs at each period, and mouth status during HFNC. We used multiple regression analysis to identify factors associated with improvement in thoraco-abdominal synchrony. RESULTS: During HFNC, breathing frequency significantly decreased from 25 breaths/min (IQR 22–27 breaths/min) to 21 breaths/min (IQR 18–24 breaths/min) (P < .001), and MCA/VT (P < .001) and phase angle (P = .047) significantly improved. CONCLUSIONS: HFNC improved thoraco-abdominal synchrony in adult subjects with mild to moderate respiratory failure.

Humidification Performance of Two High-Flow Nasal Cannula Devices: A Bench Study

INTRODUCTION: Delivering heated and humidified medical gas at 20–60 L/min, high-flow nasal cannula (HFNC) creates low levels of PEEP and ameliorates respiratory mechanics. It has become a common therapy for patients with respiratory failure. However, independent measurement of heat and humidity during HFNC and comparison of HFNC devices are lacking. METHODS: We evaluated 2 HFNC (Airvo 2 and Optiflow system) devices. Each HFNC was connected to simulated external nares using the manufacturers standard circuit. The Airvo 2 outlet-chamber temperature was set at 37°C. The Optiflow system incorporated an O2/air blender and a heated humidifier, which was set at 40°C/−3. For both systems, HFNC flow was tested at 20, 40, and 50 L/min. Simulating spontaneous breathing using a mechanical ventilator and TTL test lung, we tested tidal volumes (VT) of 300, 500, and 700 mL, and breathing frequencies of 10 and 20 breaths/min. The TTL was connected to the simulated external nares with a standard ventilator circuit. To prevent condensation, the circuit was placed in an incubator maintained at 37°C. Small, medium, and large nasal prongs were tested. Absolute humidity (AH) of inspired gas was measured at the simulated external nares. RESULTS: At 20, 40, and 50 L/min of flow, respective AH values for the Airvo 2 were 35.3 ± 2.0, 37.1 ± 2.2, and 37.6 ± 2.1 mg/L, and for the Optiflow system, 33.1 ± 1.5, 35.9 ± 1.7, and 36.2 ± 1.8 mg/L. AH was lower at 20 L/min of HFNC flow than at 40 and 50 L/min (P < .01). While AH remained constant at 40 and 50 L/min, at 20 L/min of HFNC flow, AH decreased as VT increased for both devices. CONCLUSIONS: During bench use of HFNC, AH increased with increasing HFNC flow. When the inspiratory flow of spontaneous breathing exceeded the HFNC flow, AH was influenced by VT. At all experimental settings, AH remained > 30 mg/L.

Performance of Leak Compensation in All-Age ICU Ventilators During Volume-Targeted Neonatal Ventilation: A Lung Model Study

BACKGROUND: Volume-targeted ventilation is increasingly used in low birthweight infants because of the potential for reducing volutrauma and avoiding hypocapnea. However, it is not known what level of air leak is acceptable during neonatal volume-targeted ventilation when leak compensation is activated concurrently. METHODS: Four ICU ventilators (Servo-i, PB980, V500, and Avea) were compared in available invasive volume-targeted ventilation modes (pressure control continuous spontaneous ventilation [PC-CSV] and pressure control continuous mandatory ventilation [PC-CMV]). The Servo-i and PB980 were tested with (+) and without (−) their proximal flow sensor. The V500 and Avea were tested with their proximal flow sensor as indicated by their manufacturers. An ASL 5000 lung model was used to simulate 4 neonatal scenarios (body weight 0.5, 1, 2, and 4 kg). The ASL 5000 was ventilated via an endotracheal tube with 3 different leaks. Two minutes of data were collected after each change in leak level, and the asynchrony index was calculated. Tidal volume (VT) before and after the change in leak was assessed. RESULTS: The differences in delivered VT between before and after the change in leak were within ±5% in all scenarios with the PB980 (−/+) and V500. With the Servo-i (−/+), baseline VT was ≥10% greater than set VT during PC-CSV, and delivered VT markedly changed with leak. The Avea demonstrated persistent high VT in all leak scenarios. Across all ventilators, the median asynchrony index was 1% (interquartile range 0–27%) in PC-CSV and 1.8% (0–45%) in PC-CMV. The median asynchrony index was significantly higher in the Servo-i (−/+) than in the PB980 (−/+) and V500 in 1 and 2 kg scenarios during PC-CSV and PC-CMV. CONCLUSIONS: The PB980 and V500 were the only ventilators to acclimate to all leak scenarios and achieve targeted VT. Further clinical investigation is needed to validate the use of leak compensation during neonatal volume-targeted ventilation.

Hyperoxemia in Mechanically Ventilated, Critically Ill Subjects: Incidence and Related Factors

BACKGROUND: Excessive supplemental oxygen causes injurious hyperoxemia. Before establishing the best PaO2 targets for mechanically ventilated patients, it is important to understand the incidence of hyperoxemia and related factors. We investigated oxygenation in mechanically ventilated subjects in our ICU and evaluated factors related to hyperoxemia (PaO2 > 120 mm Hg) at 48 h after initiation of mechanical ventilation. METHODS: We retrospectively reviewed the medical records of patients admitted to our ICU from January 2010 to May 2013. Inclusion criteria were 15 y of age or older and administration of mechanical ventilation for > 48 h. Patients at risk of imminent death on admission or who had received noninvasive ventilation were excluded. We collected subject demographics, reasons for mechanical ventilation, and during mechanical ventilation, we collected arterial blood gas data and ventilator settings on the first day of intubation (T1), 48 h after initiation of mechanical ventilation (T2), and on the day of extubation (T3). Multivariable logistic regression analysis was performed to clarify independent variables related to hyperoxemia at T2. RESULTS: For the study period, data for 328 subjects were analyzed. PaO2 statistically significantly increased over time to 90 (interquartile range of 74–109) mm Hg at T1, 105 (89–120) mm Hg at T2, and 103 (91–119) mm Hg at T3 (P < .001), coincident with decreases in FIO2 of 0.4 (0.3–0.5) at T1, 0.3 (0.3–0.4) at T2, and 0.3 (0.3–0.35) at T3 (P < .001). Hyperoxemia occurred in 15.6% (T1), 25.3% (T2), and 22.4% (T3) of subjects. Multivariable logistic regression analysis revealed that hyperoxemia was independently associated with age of < 40 y (odds ratio 2.6, 95% CI 1.1–6.0), Acute Physiology and Chronic Health Evaluation II scores of ≥ 30 (odds ratio 0.53, 95% CI 0.3–1.0), and decompensated heart failure (odds ratio 1.9, 95% CI 1.1 to 3.5). CONCLUSIONS: During mechanical ventilation of critically ill subjects, PaO2 increased, and FIO2 decreased. One in 4 subjects were hyperoxemic at T2, and hyperoxemia persisted until T3.

Effects of Leak Compensation on Patient-Ventilator Synchrony During Premature/Neonatal Invasive and Noninvasive Ventilation: A Lung Model Study

BACKGROUND: During both nasal noninvasive ventilation (NIV) and invasive ventilation of neonates, the presence of air leaks causes triggering and cycling asynchrony. METHODS: Five ICU ventilators (PB840, PB980, Servo-i, V500, and Avea) were compared in available invasive ventilation and NIV ventilator modes (pressure control continuous spontaneous ventilation [PC-CSV] and pressure control continuous mandatory ventilation [PC-CMV]). The V500 and Avea do not provide PC-CSV and PC-CMV in NIV. The Servo-i and Avea were tested with and without their proximal flow sensor. The ASL 5000 lung model (version 3.5) was used to simulate 4 neonatal scenarios (body weight 0.5, 1, 2, and 4 kg). The ASL 5000 was ventilated via endotracheal tube (invasive ventilation) or nasal cannula (NIV) with 4 different leaks. RESULTS: The Avea (without flow sensor) during invasive ventilation and Servo-i and PB840 during NIV were not triggered by inspiratory efforts of the ASL 5000 at the baseline leak in the 0.5 kg scenario. In invasive ventilation, overall (median) asynchrony index was significantly lower with the PB980 (1%) and V500 (3%) than with the Servo-i (with flow sensor, 50%; without flow sensor, 50%) and Avea (with sensor, 50%; without sensor, 62%) (P < .05 for all comparisons). The PB840 (33%) was significantly different from all ventilators (P < .05). In NIV, the asynchrony index was significantly lower in PB980 (2%) than in the Servo-i (with sensor, 100%; without sensor, 100%) and PB840 (75%) (P < .05 for both). There was no difference in asynchrony index between PC-CSV and PC-CMV in all tested conditions and ventilators. CONCLUSIONS: The ability of leak compensation to prevent asynchronous breathing varied widely between ventilators and lung mechanics. The PB980 and V500 were the only two ventilators to acclimate to all leak scenarios in invasive ventilation, and PB980 was the only ventilator to acclimate to all leak scenarios in NIV.

Performance of the PneuX System: A Bench Study Comparison With 4 Other Endotracheal Tube Cuffs

BACKGROUND: Cuff design affects microaspiration, a risk factor for pneumonia. We questioned whether the PneuX low-volume fold-free cuff design would prevent cuff leakage and maintain the same tracheal wall pressure as high-volume, low-pressure (HVLP) cuffs. METHODS: We evaluated 4 HVLP-cuffed endotracheal tubes (ETTs), Hi-Lo (polyvinyl chloride [PVC]), Microcuff (polyurethane [PU]), SealGuard (PU + tapered), and TaperGuard (PVC + tapered), and the PneuX with its dedicated tracheal seal monitor. In Part 1, we determined tracheal wall pressure using each cuffs capacity to support water columns across recommended intracuff pressures. In Part 2, we evaluated the tracheal seal monitor function at recommended settings. In Part 3, we compared leakage volumes of all ETTs during 30 min of simulated mechanical ventilation or during 8 h if no leak occurred. Parts 1 and 3 were performed with/without lubrication and PEEP. RESULTS: In Part 1, PneuX cuffs exerted an average tracheal wall pressure of 27.4 ± 2.4 cm H2O at the recommended intracuff pressure of approximately 80 cm H2O. Tracheal wall pressure did not differ among HVLP cuffs (19.6 ± 1.4 to 29.5 ± 1.4 cm H2O). In Part 2, preinflation intracuff pressure affected the time to obtain tracheal seal monitor pressure attainment (P < .01). The tracheal seal monitor generated average calculated tracheal wall pressure of 33.4 ± 1.2 cm H2O. In Part 3, PneuX ETT showed no leak across 8 h for all trials. Overall, leakage volume was lower with PU (P < .01) and PneuX (P < .01) than with PVC cuffs, regardless of shape, and lower with lubrication and/or PEEP (all P < .01). In each HVLP cuff, lubrication alone eliminated leak at an intracuff pressure of ≤30 cm H2O. CONCLUSIONS: The PneuX cuff generally exerted acceptable tracheal wall pressure, but the tracheal wall pressure monitor allowed pressures exceeding 30 cm H2O in some trials and was the only ETT to prevent leak in all tests. For HVLP cuffs, leak was reduced by PU and PEEP and eliminated by lubrication.

A novel method of post-pyloric feeding tube placement at bedside

PURPOSE Post-pyloric feeding tube placement is often difficult, and special equipment or peristalsis agents are used to aid insertion. Although several reports have described blind techniques for post-pyloric feeding-tube placement, no general consensus about method preference has been achieved. MATERIALS AND METHODS The technique is performed as follows: via the nostril, a stylet-tipped feeding tube is advanced about 70 cm; to confirm tip location to the right of the epigastric area, towards the right hypochondriac region, 5 mL shots of air are injected to enable touch detection of bubbling; finally, the tube is advanced to a length of 100 cm, during which the strength of bubbling seems to diminish under palpation. RESULTS We prospectively enrolled consecutive patients whose oral intake was expected to be difficult for 48 hours in the intensive care unit. Forty-one patients were enrolled and the rate of successful placement at first attempt was 95.1%. Mean duration for successful placement was 15 minutes. CONCLUSIONS With a novel technique, from the bedside, without special tools or drugs, we successfully placed post-pyloric feeding tubes. Essential points when inserting the tube are confirmation of the location of the tube tip by palpation of injected air, and to avoid deflection and looping.

A recommended solution for avoiding coring of a rubber stopper.

In Response: Drs. Lohser and Brodsky raise the measurement of left mainstem bronchial diameter as an indicator of proper sizing for left-sided doublelumen tubes (DLT), and suggest that use of this technique in our recent study may have yielded different results. While we don’t question the mathematical formulas, none of the clinicians involved in the study practice this method despite over 80 years of cumulative experience successfully placing DLT in an institution where 2000 thoracic procedures are performed each year. Accordingly, our work addressed the prevalent practice at our institution of sizing DLT by height and/or gender. Although the participating anesthesiologists were all initially trained to use conventional methods at a time when fiberoptic bronchoscopy was not readily available, the strength of our study design is that we compared outcomes in a single clinical setting between anesthesiologists whose practice now differs. Our data showed that in regard to intraoperative end-points reflecting the adequacy of lung collapse and preservation of oxygenation, both our “conventional” approach and intentional downsizing are comparable. While we appreciate the interpretation by Drs. Lohser and Brodsky that our observed “failure to isolate” temporarily may well have been due to undersized DLT, we maintain our stated conclusion that malposition was responsible. With respect to the rare event of DLT causing airway damage, the authors cite their own early data indicating that rupture in particular is most frequently associated with small DLT, perhaps due to the need for relative cuff hyperinflation. While we included this citation in our manuscript, we also included references indicating the possibility of trauma from either small or large DLT, a risk also previously noted by Brodsky and Lemmens and cited in our paper. Furthermore, despite use of down-sized DLT we rarely found that more than 3 mL was required to provide an adequate seal. The authors further point to the theoretical increase in auto-PEEP due to downsizing of DLT. While experimental studies have clearly shown differences in the gas flow characteristics between large and small DLT, neither results of the our study nor our extensive clinical experience have given any indication that the 0.6 mm difference between a 35 and 39 FR internal diameter has had any deleterious effects in our patient population. Indeed, our reported incidence of intraoperative hypoxemia and recently published incidence of acute lung injury in 1,428 patients undergoing lung resection are low and consistent with the literature.

The effect of head rotation on efficiency of face mask ventilation in anaesthetised apnoeic adults: A prospective, randomised, crossover study.

BACKGROUND Upper airway obstruction occurs commonly after induction of general anaesthesia. It is the major cause of difficult mask ventilation. OBJECTIVES The aim of this study was to determine whether head rotation improves the efficiency of mask ventilation of anaesthetised apnoeic adults. DESIGN A randomised, crossover study. SETTING Single university teaching hospital. PATIENTS Forty patients, aged 18 to 75 years with a BMI 18.5 to 35.0 kg m−2 requiring general anaesthesia for elective surgery were recruited and randomised into two groups. INTERVENTIONS Once apnoeic after induction of general anaesthesia, face mask ventilation began with pressure controlled ventilation, at a peak inspiratory pressure of 15 cmH2O. Each patient was ventilated for three 1-min intervals with the head position alternated every minute: group A, mask ventilation was performed with a neutral head position for 1 min, followed by an axial head position rotated 45° to the right for 1 min and then returned to the neutral position for another 1 min. In group B, the sequence of head positioning was rotated → neutral → rotated. MAIN OUTCOME MEASURES Expiratory tidal volume, measured with a respiratory inductive plethysmograph. RESULTS Two patients were excluded due to protocol violation; thus, data from 38 patients were analysed. The mean expiratory tidal volume was significantly higher in the rotated head position than in the neutral position (612.6 vs. 544.0 ml: difference [95% confidence interval], 68.6 [46.8 to 90.4] ml, P < 0.0001). CONCLUSION Head rotation of 45° in anaesthetised apnoeic adults significantly increases the efficiency of mask ventilation compared with the neutral head position. Head rotation is an effective alternative to improve mask ventilation if airway obstruction is encountered. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT02755077.

Complete bronchial obstruction by granuloma in a paediatric patient with translaryngeal endotracheal tube: a case report

IntroductionAlthough continuous or frequent stimuli in tracheostomized patients may cause tracheal granulomas, little is known about management of patients with translaryngeal intubation.Case presentationA 1-month-old Japanese boy, weighing 3.5kg, was admitted to our hospital owing to cardiac failure caused by an atrial septal defect and intractable arrhythmia. To treat his unstable cardiovascular status, surgery was performed to close his atrial septal defect. After the operation, stenosis was detected by auscultation and flow limitation worsened. A bronchoscopy revealed granulomas completely obstructing his right bronchus and partially obstructing his left bronchus. Dexamethasone infusion partially reduced the mass, after which removal by yttrium aluminium garnet laser was tried. The airway obstruction was not resolved, however, because of granuloma reproliferation. Budesonide (aerosol liquid) inhalation was started, and tissue was reduced using an yttrium aluminium garnet laser and physically removed using forceps. After continued budesonide inhalation, he was successfully liberated from the ventilator.ConclusionsLife-threatening airway obstruction by granulomas developed in a translaryngeally intubated paediatric patient. The granuloma was detected after a couple of weeks of intubation. A bronchial granuloma is rare in paediatric patients. It should be suspected with evidence of bronchial obstruction. Treatment with corticosteroids and surgery using a laser maybe indicated.