Nao Okuda

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.

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.

Hygrometric Properties of Inspired Gas and Oral Dryness in Patients With Acute Respiratory Failure During Noninvasive Ventilation

BACKGROUND: Because noninvasive ventilation (NIV) delivers medical gas at high flow, inadequate humidification may cause oral dryness and patient discomfort. Heated humidification can be used during NIV, but little has been reported about the effects on the hygrometric conditions inside an oronasal mask and oral dryness during 24 hours on NIV. METHODS: We measured absolute humidity (AH) inside oronasal masks on subjects with acute respiratory failure during 24 hours on NIV. A single-limb turbine ventilator and oronasal mask with an exhalation port were used for NIV. Oral moistness was evaluated using an oral moisture-checking device, and 3 times during the 24 hours the subjects subjectively scored the feeling of dryness on a 0–10 scale in which 10 was the most severe dryness. RESULTS: Sixteen subjects were enrolled. The mean ± SD AH inside the mask was 30.0 ± 2.6 mg H2O/L (range 23.1–33.3 mg H2O/L). The median oral moistness was 19.2% (IQR 4.4–24.0%), and the median oral dryness score was 5.5 (IQR 4–7). AH and inspired gas leak correlated inversely, both within the subjects (r = −0.56, P < .001) and between the subjects (r = −0.58, P = .02). AH and oral moistness correlated within the subjects (r = 0.39, P = .04). Oral breathing was associated with reduced oral moistness (P = .001) and increased oral dryness score (P = .002). CONCLUSIONS: AH varied among the subjects, and some complained of oral dryness even with heated humidifier. Oral breathing decreased oral moistness and worsened the feeling of dryness.

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.

Inspiratory Tube Condensation During High-Flow Nasal Cannula Therapy: A Bench Study

BACKGROUND: High-flow nasal cannula (HFNC) therapy provides better humidification than conventional oxygen therapy. To allay loss of vapor as condensation, a servo-controlled heating wire is incorporated in the inspiratory tube, but condensation is not completely avoidable. We investigated factors that might affect condensation: thermal characteristics of the inspiratory tube, HFNC flow, and ambient temperature. METHODS: We evaluated 2 types of HFNC tubes, SLH Flex 22-mm single tube and RT202. Both tubes were connected to a heated humidifier with water reservoir. HFNC flow was set at 20, 40, and 60 L/min, and FIO2 was set at 0.21. Air conditioning was used maintain ambient temperature at close to either 20 or 25°C. We weighed the tubes on a digital scale before (0 h) and at 3, 6, and 24 h after, turning on the heated humidifier, and calculated the amount of condensation by simple subtraction. The amount of distilled water used during 24 h was also recorded. RESULTS: At 25°C, there was little condensation, but at 20°C and HFNC flow of 20, 40, and 60 L/min for 24 h, the amount of condensation with the SLH was 50.2 ± 10.7, 44.3 ± 17.7, and 56.6 ± 13.9 mg, and the amount with the RT202 was 96.0 ± 35.1, 72.8 ± 8.2, and 64.9 ± 0.8 mg. When ambient temperature was set to 20°C, condensation with the RT202 was statistically significantly greater than with the SLH at all flow settings (P < .001). CONCLUSIONS: Ambient temperature statistically significantly influenced the amount of condensation in the tubes.

Performance of Ventilators Compatible With Magnetic Resonance Imaging: A Bench Study

BACKGROUND: Magnetic resonance imaging (MRI) is indispensable for diagnosing brain and spinal cord abnormalities. Magnetic components cannot be used during MRI procedures; therefore, patient support equipment must use MRI-compatible materials. However, little is known of the performance of MRI-compatible ventilators. METHODS: At commonly used settings, we tested the delivered tidal volume (VT), FIO2, PEEP, and operation of the high-inspiratory-pressure-relief valves of 4 portable MRI-compatible ventilators (Pneupac VR1, ParaPAC 200DMRI, CAREvent MRI, iVent201) and one ICU ventilator (Servo-i). Each ventilator was set in volume control/continuous mandatory ventilation mode. Breathing frequency and VT were tested at 10 breaths/min and 300, 500, and 700 mL, respectively. The Pneupac VR1 has fixed VT and frequency combinations, so it was tested at VT = 300 mL and 20 breaths/min, VT = 500 mL and 12 breaths/min, and VT = 800 mL and 10 breaths/min. FIO2 was 0.6 and 1.0. At the air-mix setting, FIO2 was fixed at 0.5 with the Pneupac VR1, 0.45 with the ParaPAC 200DMRI, and 0.6 with the CAREvent MRI. PEEP was set at 5 and 10 cm H2O, and pressure relief was set at 30 and 40 cm H2O. RESULTS: VT error varied widely among ventilators (−28.1 to 25.5%). As VT increased, error decreased with the Pneupac VR1, ParaPAC 200DMRI, and CAREvent MRI (P < .05). FIO2 error ranged from −13.3 to 25.3% at 0.6 (or air mix). PEEP error varied among ventilators (−29.2 to 42.5%). Only the Servo-i maintained VT, FIO2, and PEEP at set levels. The pressure-relief valves worked in all ventilators. CONCLUSIONS: None of the MRI-compatible ventilators maintained VT, FIO2, and PEEP at set levels. Vital signs of patients with unstable respiratory mechanics should be monitored during transport and MRI.

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.

Incidence of bacterial contamination in infusion set needles

We examined the incidence and types of bacterial contamination in 265 infusion set needles in adult critically ill patients. Bacterial contamination was detected in 15 samples (5.7%), and a total of 17 organisms were isolated. Ten were coagulase-negative staphylococci (CNS) and Staphylococcus aureus, and the remainder were α-Streptococcus, Corynebacterium, and gram-negative rods. Although the contamination was not directly related to catheter-related bloodstream infections exchanging infusion bottles can cause intraluminal contamination and is a possible route of these infections.

Acute Cardiac Failure in a Pregnant Woman due to Thyrotoxic Crisis

Introduction. Cardiac failure during pregnancy is usually related to preeclampsia/eclampsia, rarely to hyperthyroidism. While hyperthyroidism can easily lead to hypertensive cardiac failure and may harm the fetus, it is sometimes difficult to distinguish hyperthyroidism from normal pregnancy. Case Presentation. We encountered a case of 41-year-old pregnant woman with hypertensive cardiac failure. Because we initially diagnosed as pre-eclampsia/eclampsia, Caesarian section was performed. However, her symptoms still persisted after delivery. After thyroid function test results taken on the day of admission were obtained on the fourth day, we could diagnose that her cardiac failure was caused by thyrotoxic crisis. Conclusions. Hypertensive cardiac failure due to hyperthyroidism during pregnancy is rare and difficult to diagnose because of similar presentation of normal pregnancy. However, physicians should be aware of the risks posed by hyperthyroidism during pregnancy.