Non-intubated critically ill patients are often treated by high-flow oxygen for acute respiratory failure. There is no current recommendation for humidification of oxygen devices.
We conducted a prospective randomized trial with a final crossover period to compare nasal airway caliber and respiratory comfort in patients with acute hypoxemic respiratory failure receiving either standard oxygen therapy with no humidification or heated and humidified high-flow oxygen therapy (HHFO(2)) in a medical ICU. Nasal airway caliber was measured using acoustic rhinometry at baseline, after 4 and 24 hours (H4 and H24), and 4 hours after crossover (H28). Dryness of the nose, mouth, and throat was auto-evaluated and assessed blindly by an otorhinolaryngologist. After the crossover, the subjects were asked which system they preferred.
Thirty subjects completed the protocol and were analyzed. Baseline median oxygen flow was 9 and 12 L/min in the standard and HHFO(2) groups, respectively (P = .21). Acoustic rhinometry measurements showed no difference between the 2 systems. The dryness score was significantly lower in the HHFO(2) group at H4 (2 vs 6, P = .007) and H24 (0 vs 8, P = .004). During the crossover period, dryness increased promptly after switching to standard oxygen and decreased after switching to HHFO(2) (P = .008). Sixteen subjects (53%) preferred HHFO(2) (P = .01), especially those who required the highest flow of oxygen at admission (P = .05).
Upper airway caliber was not significantly modified by HHFO(2), compared to standard oxygen therapy, but HHFO(2) significantly reduced discomfort in critically ill patients with respiratory failure. The system is usually preferred over standard oxygen therapy.
"HFNC might also reduce the work of breathing
. HFNC requires active heating and humidification of the respiratory gases in order to prevent damage of the respiratory epithelium and reduces discomfort during therapy
[8,9]. Lastly, HFNC is increasingly used in intensive care and emergency medicine
[Show abstract][Hide abstract] ABSTRACT: Aim of the study was to compare the short-term effects of oxygen therapy via a high-flow nasal cannula (HFNC) on functional and subjective respiratory parameters in patients with acute hypoxic respiratory failure in comparison to non-invasive ventilation (NIV) and standard treatment via a Venturi mask.
Fourteen patients with acute hypoxic respiratory failure were treated with HFNC (FiO2 0.6, gas flow 55 l/min), NIV (FiO2 0.6, PEEP 5 cm H2O Hg, tidal volume 6–8 ml/kg ideal body weight,) and Venturi mask (FiO2 0.6, oxygen flow 15 l/min,) in a randomized order for 30 min each. Data collection included objective respiratory and circulatory parameters as well as a subjective rating of dyspnea and discomfort by the patients on a 10-point scale. In a final interview, all three methods were comparatively evaluated by each patient using a scale from 1 (=very good) to 6 (=failed) and the patients were asked to choose one method for further treatment.
PaO2 was highest under NIV (129 ± 38 mmHg) compared to HFNC (101 ± 34 mmHg, p <0.01 vs. NIV) and VM (85 ± 21 mmHg, p <0.001 vs. NIV, p <0.01 vs. HFNC, ANOVA). All other functional parameters showed no relevant differences. In contrast, dyspnea was significantly better using a HFNC (2.9 ± 2.1, 10-point Borg scale) compared to NIV (5.0 ± 3.3, p <0.05), whereas dyspnea rating under HFNC and VM (3.3 ± 2.3) was not significantly different. A similar pattern was found when patients rated their overall discomfort on the 10 point scale: HFNC 2.7 ± 1.8, VM 3.1 ± 2.8 (ns vs. HFNC), NIV 5.4 ± 3.1 (p <0.05 vs. HFNC). In the final evaluation patients gave the best ratings to HFNC 2.3 ± 1.4, followed by VM 3.2 ± 1.7 (ns vs. HFNC) and NIV 4.5 ± 1.7 (p <0.01 vs. HFNC and p <0.05 vs. VM). For further treatment 10 patients chose HFNC, three VM and one NIV.
In hypoxic respiratory failure HFNC offers a good balance between oxygenation and comfort compared to NIV and Venturi mask and seems to be well tolerated by patients.
German clinical trials register: DRKS00005132.
[Show abstract][Hide abstract] ABSTRACT: Objective: Nasal high flow (NHF) has been shown to increase expiratory pressure and reduce respiratory rate but the mechanisms involved remain unclear. Methods: Ten healthy participants [age 22±2) years; body mass index (BMI) 24±2 kg/m(2)], were recruited for determining ventilatory responses to NHF of air at 37°C and fully saturated with water. We conducted a randomized, controlled, cross-over study consisting of four separate ~60-minute visits, each one week apart, to determine the effect of NHF on ventilation during wakefulness (NHF at 0, 15, 30, 45 L/min) and sleep (NHF at 0, 15 and 30 L/min). In addition, a nasal cavity model was used to compare pressure/air-flow relationships of NHF and continuous positive airway pressure (CPAP) throughout simulated breathing. Results: During wakefulness, NHF led to an increase in tidal volume from 0.7±0.1 L to 0.8±0.2, 1.0±0.2, and 1.3±0.2 L and a reduction in respiratory rate (f(R)) from 16±2 to 13±3, 10±3, and 8±3 breaths/min (baseline to 15, 30, 45 L/min NHF, respectively, P < 0.01). In contrast, during sleep NHF led to a ~20% fall in minute ventilation due to a decrease in tidal volume and no change in f(R). In the nasal cavity model, NHF increased expiratory but decreased inspiratory resistance depending on both the cannula size and the expiratory flow rate. Conclusions: The mechanisms of action for NHF differ from those of CPAP and are sleep/wake-state dependent. NHF may be utilized to increase tidal breathing during wakefulness and to relieve respiratory loads during sleep.
[Show abstract][Hide abstract] ABSTRACT: /st>Respiratory complications after cardiac surgery increase morbidity, mortality, and length of stay. Studies suggest that routine delivery of positive airway pressure after extubation may be beneficial. We sought to determine whether the routine administration of nasal high-flow oxygen therapy (NHF) improves pulmonary function after cardiac surgery.
/st>A pragmatic randomized controlled trial; participants received either NHF (45 litre min(-1)) or usual care from extubation to Day 2 after surgery. The primary outcome was number of patients with / ratio ≥445 on Day 3 after surgery. The secondary outcomes included atelectasis score on chest X-ray; spirometry; intensive care and hospital length of stay; mortality on Day 28; oxygenation indices; escalation of respiratory support; and patient comfort.
/st>We randomized 340 patients over 14 months. The number of patients with a / ratio of ≥445 on Day 3 was 78 (46.4%) in the NHF group vs 72 (42.4%) standard care [odds ratio (OR) 1.18, 95% confidence interval (CI) 0.77-1.81, P=0.45]. was reduced at both 4 h post-extubation and at 9 a.m. on Day 1 in the NHF group (5.3 vs 5.4 kPa, P=0.03 and 5.1 vs 5.3 kPa, P=0.03, respectively). Escalation in respiratory support at any time in the study occurred in 47 patients (27.8%) allocated to NHF compared with 77 (45%) standard care (OR 0.47, 95% CI 0.29-0.7, P=0.001).
/st>Routine use of NHF did not increase / ratio on Day 3 but did reduce the requirement for escalation of respiratory support.Trial RegistrationAustralia New Zealand Clinical Trials Registry www.anzctr.org.au (ACTRN12610000973011).
BJA British Journal of Anaesthesia 08/2013; 111(6). DOI:10.1093/bja/aet262 · 4.85 Impact Factor
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