Ventilator-assisted preoxygenation: Protocol for combining non-invasive ventilation and apnoeic oxygenation using a portable ventilator

Ventilator-assisted preoxygenation in an aeromedical retrieval setting

OBJECTIVE

Ventilator-assisted preoxygenation (VAPOX) is a method of preoxygenation and apnoeic ventilation which has been tried in hospital setting. We aimed to describe VAPOX during intubation of critically unwell patients in aeromedical retrieval setting.

METHODS

Retrospective observational study of VAPOX performed at LifeFlight Retrieval Medicine (LRM) between January 2018 and December 2022 across Queensland, Australia. Demographic and clinical data were recorded. Descriptive statistics and paired Student's t-tests were used to evaluate the efficacy of VAPOX on oxygen saturation (SpO2).

RESULTS

VAPOX was used in 40 patients. Diagnoses included pneumonia (n = 11), COPD (n = 6) and neurological (n = 7). Patients were intubated in hospital (n = 36), in helicopter (n = 2) and ambulance (n = 2). Median VAPOX settings were: positive end-expiratory pressure 6 (IQR 5-9), pressure support 10 (IQR 10-14) and back up respiratory rate 14 (IQR 11-18). Twelve agitated patients underwent delayed sequence induction with ketamine. There was a statistically significant increase in SpO2 after application of VAPOX (P < 0.001), followed by a slight decrease after intubation (P = 0.006). Mean SpO2 were significantly improved after intubation compared with on arrival of LRM (P = 0.016). Hypotension was present prior to VAPOX (n = 13), during VAPOX (n = 2) and post-intubation (n = 15). Two patients had cardiac arrest. Three patients were started on VAPOX but subsequently failed. There were no significant oxygen depletion or aspiration events.

CONCLUSION

VAPOX can be considered for pre-intubation optimisation in the retrieval environment. The incidence of post-intubation critical hypoxia was low, and hypotension was high. Pre-intubation respiratory physiology can be optimised by delivering variable pressure supported minute ventilation, achieving a low incidence of critical hypoxia.

Safety and Risk in Airway Management During Bariatric Air Medical Retrieval

OBJECTIVE

Bariatric anatomy and physiology present added clinical challenges to the provision of safe critical care and patient transport. LifeFlight Retrieval Medicine provides air medical retrieval services in Queensland, Australia, and performs over 6,000 retrieval missions annually using rotary wing, fixed wing, and ground ambulance platforms.

METHODS

Bariatric patient retrievals were identified from the LifeFlight Retrieval Medicine electronic patient database. These cases were interrogated to quantify and describe adverse events during patient transport.

RESULTS

Over the study period from July 2019 to December 2021 11,096 patient retrievals were completed. Of these patients, 816 (7.3%) had a body weight ≥ 120 kg (range, 120-246 kg; median = 146 kg). Bariatric patients were more likely to be male (70%) and to require critical care interventions than nonbariatric patients (25.9% vs. 19.9%). There was an absolute 1.5% increase of high-interest events during patient retrieval, corresponding to a 1.9-fold increased relative risk. Five hundred eleven of 11,096 patients were intubated by the retrieval team, and 61 of these weighed ≥ 120 kg. Bariatric patients undergoing intubation were of similar age and sex, weighed significantly more, had nonsignificant trends toward poorer airway visualization by Cormack-Lehane laryngoscopic grade, and tended toward reduced first-attempt success compared with nonbariatric patients. Rates of airway adverse events (AAEs) were significantly increased for the bariatric group (30/61, 49.2%) compared with the nonbariatric group (135/450, 30.0%) (χ2 likelihood ratio, P = .004). Postintubation desaturation was the most common AAE and was the only criterion significantly increased when comparing bariatric (26%) versus nonbariatric (12%) patients (χ2 likelihood ratio, P = .005). Using patient weight as a continuous variable, nominal logistic regression revealed a significant effect of increasing weight on AAEs (χ2 = 12.9, P = .0003) with a threshold of 105 kg providing an optimal 88% sensitivity for predicting AAEs. The odds of AAEs were increased significantly for those weighing 105 to 119 kg versus those weighing < 105 kg (odds ratio [OR] = 3.4; 95% confidence interval [CI], 1.6-7.5) and for those weighing ≥ 120 kg versus those weighing < 105 kg (OR = 2.5; 95% CI, 1.4-4.3). There was no difference between those weighing ≥ 120 kg versus those weighing 105 to 119 kg (OR = 0.73; 95% CI, 0.3-1.8).

CONCLUSION

Air medical retrieval of bariatric patients is safe despite an increased risk of adverse events. Strategies to optimize emergency anesthesia should be used to maximize safe intubation in bariatric patients.

Unintended consequences: The impact of airway management modifications introduced in response to COVID-19 on intubations in a tertiary centre emergency department

Objective

In response to COVID‐19, we introduced and examined the effect of a raft of modifications to standard practice on adverse events and first‐attempt success (FAS) associated with ED intubation.

Methods

An analysis of prospectively collected registry data of all ED intubations over a 3‐year period at an Australian Major Trauma Centre. During the first 6 months of the COVID‐19 pandemic in Australia, we introduced modifications to standard practice to reduce the risk to staff including: aerosolisation reduction, comprehensive personal protective equipment for all intubations, regular low fidelity simulation with ‘sign‐off’ for all medical and nursing staff, senior clinician laryngoscopist and the introduction of pre‐drawn medications.

Results

There were 783 patients, 136 in the COVID‐19 era and 647 in the pre‐COVID‐19 comparator group. The rate of hypoxia was higher during the COVID‐19 era compared to pre‐COVID‐19 (18.4% vs 9.6%, P < 0.005). This occurred despite the FAS rate remaining very high (95.6% vs 93.8%, P = 0.42) and intubation being undertaken by more senior laryngoscopists (consultant 55.9% during COVID‐19 vs 22.6% pre‐COVID‐19, P < 0.001). Other adverse events were similar before and during COVID‐19 (hypotension 12.5% vs 7.9%, P = 0.082; bradycardia 1.5% vs 0.5%, P = 0.21). Video laryngoscopy was more likely to be used during COVID‐19 (95.6% vs 82.5%, P < 0.001) and induction of anaesthesia more often used ketamine (66.9% vs 42.3%, P < 0.001) and rocuronium (86.8% vs 52.1%, P < 0.001).

Conclusions

This raft of modifications to ED intubation was associated with significant increase in hypoxia despite a very high FAS rate and more senior first laryngoscopist.

Face mask leak with nasal cannula during noninvasive positive pressure ventilation: A randomized crossover trial

BACKGROUND

Nasal cannula can achieve apneic oxygenation during emergency intubation. However, pre-procedure nasal cannula placement may be difficult in patients undergoing non-invasive positive pressure ventilation (NPPV) prior to intubation. Our objective was to compare mask leak during NPPV with versus without simultaneous application of nasal cannula. We hypothesized mask leak would be no worse with concomitant use of nasal cannula (non-inferiority design).

METHODS

We performed a randomized crossover non-inferiority study of healthy volunteers. We randomized subjects undergoing 60s trials of NPPV (10cmH₂O continuous positive airway pressure) to either NPPV alone (NPPV-a) or NPPV with nasal cannula at 15L/min (NPPV-nc). After a brief rest period, all subjects underwent the alternative intervention. The primary outcome was time averaged mask leak over 60s (L/min). We defined a non-inferiority margin of 5L/min.

RESULTS

We enrolled 64 subjects. Mean time-averaged mask leak was 2.2L/min for NPPV-a versus 4.0L/min for NPPV-nc for a difference of 1.7L/min (one-sided 95% CI -∞ to 3.2L/min). NPPV-a resulted in higher mean minute volume received (13.5 versus 12.2L) and higher mean respiratory rates (14.8 versus 13.5 breaths per minute).

CONCLUSION

The addition of nasal cannula during NPPV does not significantly increase mask leak. The simultaneous application of nasal cannula with NPPV may be a useful strategy to streamline airway management among patients undergoing NPPV prior to intubation.