Pneumatic performance of the Boussignac CPAP system in healthy humans

Is disposable continuous positive airway pressure system effective for the management of acute hypercapnic respiratory failure?

AIM

This study aimed to investigate the effectiveness of disposable continuous positive airway pressure (DCPAP) system in decreasing the partial pressure of carbon dioxide (PaCO2) levels in patients with acute hypercapnic respiratory failure (AHRF).

MATERIAL AND METHODS

This retrospective observational study included patients treated in the emergency department (ED) with respiratory distress and PaCO2 > 45 mmHg. Patients were divided into two groups (DCPAP and non-DCPAP), depending on the treatment received to treat AHRF. The difference between the baseline PaCO2 levels in the first blood gas obtained from patients at the time of admission and the follow-up blood gas after treatment. Then, the calculated PaCO2 decrease was divided by the time elapsed to obtain the rate of decrease in PaCO2 levels in mmHg/min. The statistical analyses were performed using SPSS version 18.0 software. A p value of < 0.05 was considered statistically significant.

RESULTS

A total of 61 patients were included in the study, 31 patients in the DCPAP group and 30 patients in the non-DCPAP group. The mean age of the patients was 74.03 ± 10.04, and the male/female was 23/38. The study demonstrated a statistically significant difference between the DCPAP and non-DCPAP groups in terms of PaCO2 decreasing rate, and it was found to be twice higher in the DCPAP group (0.11 ± 0.07 mmHg/min) than in the non-DCPAP group (0.05 ± 0.06 mmHg/min).

CONCLUSION

The study demonstrated that the treatment of AHRF patients with a DCPAP provides a faster decrease in PaCO2 levels in hypercapnic patients compared to standard medical therapy alone.

Positive Expiratory Pressure Oxygen Therapy for Respiratory Distress: A Single-arm Feasibility Trial

Background

Oxygen delivery devices with positive end-expiratory pressure (PEEP) valves have been described, but high inspiratory flows may lead to poor tolerance in tachypneic patients. Positive expiratory pressure oxygen therapy (PEP-OT) using an occlusive face mask, oxygen reservoir, and PEEP valve has not been evaluated in clinical settings.

Materials and methods

In a single-arm intervention trial, patients aged 19-55 years admitted with acute respiratory illness with oxygen support were enrolled. PEP-OT trial was given with PEEP of 5 and 7 cm of water over 45 minutes. Feasibility was assessed as uninterrupted completion of the PEP-OT trial. The effects of PEP-OT on cardiopulmonary physiology and adverse effects of therapy were recorded.

Results

Fifteen patients (6 males) were enrolled. Fourteen patients had pneumonia and one patient had pulmonary edema. Twelve patients (80%) completed the PEP-OT trial. There was significant improvement in respiratory rate (RR) and heart rate (HR) at the end of the 45-minute PEP-OT trial (p-values 0.048 and 0.003, respectively). There was a trend toward improved SpO₂ and perceived dyspnea. None of the patients developed desaturation, shock, or air leaks. Positive expiratory pressure oxygen therapy is a feasible oxygen therapy in patients with acute hypoxia.

Conclusion

Positive expiratory pressure oxygen therapy seems to be safe and has a positive impact on respiratory mechanics in parenchymal respiratory pathology.

How to cite this article

Dhochak N, Ray A, Soneja M, Wig N, Kabra SK, Lodha R. Positive Expiratory Pressure Oxygen Therapy for Respiratory Distress: A Single-arm Feasibility Trial. Indian J Crit Care Med 2022;26(11):1169-1174.

Effects of non-invasive respiratory supports on inspiratory effort in moderate-severe COVID-19 patients. A randomized physiological study

RATIONALE AND OBJECTIVE

Various forms of Non-invasive respiratory support (NRS) have been used during COVID-19, to treat Hypoxemic Acute Respiratory Failure (HARF), but it has been suggested that the occurrence of strenuous inspiratory efforts may cause Self Induced Lung Injury(P-SILI). The aim of this investigation was to record esophageal pressure, when starting NRS application, so as to better understand the potential risk of the patients in terms of P-SILI and ventilator induced lung injury (VILI).

METHODS AND MEASUREMENTS

21 patients with early de-novo respiratory failure due to COVID-19, underwent three 30 min trials applied in random order: high-flow nasal cannula (HFNC), continuous positive airway pressure (CPAP), and non-invasive ventilation (NIV). After each trial, standard oxygen therapy was reinstituted using a Venturi mask (VM). 15 patients accepted a nasogastric tube placement. Esophageal Pressure (ΔPes) and dynamic transpulmonary driving pressure (ΔPLDyn), together with the breathing pattern using a bioelectrical impedance monitor were recorded. Arterial blood gases were collected in all patients.

MAIN RESULTS

No statistically significant differences in breathing pattern and PaCO₂ were found. PaO₂/FiO₂ ratio improved significantly during NIV and CPAP vs VM. NIV was the only NRS to reduce significantly ΔPes vs. VM (-10,2 ±5 cmH20 vs -3,9 ±3,4). No differences were found in ΔPLDyn between NRS (10,2±5; 9,9±3,8; 7,6±4,3; 8,8±3,6 during VM, HFNC, CPAP and NIV respectively). Minute ventilation (Ve) was directly dependent on the patient's inspiratory effort, irrespective of the NRS applied. 14% of patients were intubated, none of them showing a reduction in ΔPes during NRS.

CONCLUSIONS

In the early phase of HARF due to COVID-19, the inspiratory effort may not be markedly elevated and the application of NIV and CPAP ameliorates oxygenation vs VM. NIV was superior in reducing ΔPes, maintaining ΔPLDyn within a range of potential safety.

Knowledge translation tools to guide care of non-intubated patients with acute respiratory illness during the COVID-19 Pandemic

Providing optimal care to patients with acute respiratory illness while preventing hospital transmission of COVID-19 is of paramount importance during the pandemic; the challenge lies in achieving both goals simultaneously. Controversy exists regarding the role of early intubation versus use of non-invasive respiratory support measures to avoid intubation. This review summarizes available evidence and provides a clinical decision algorithm with risk mitigation techniques to guide clinicians in care of the hypoxemic, non-intubated, patient during the COVID-19 pandemic. Although aerosolization of droplets may occur with aerosol-generating medical procedures (AGMP), including high flow nasal oxygen and non-invasive ventilation, the risk of using these AGMP is outweighed by the benefit in carefully selected patients, particularly if care is taken to mitigate risk of viral transmission. Non-invasive support measures should not be denied for conditions where previously proven effective and may be used even while there is suspicion of COVID-19 infection. Patients with de novo acute respiratory illness with suspected/confirmed COVID-19 may also benefit. These techniques may improve oxygenation sufficiently to allow some patients to avoid intubation; however, patients must be carefully monitored for signs of increased work of breathing. Patients showing signs of clinical deterioration or high work of breathing not alleviated by non-invasive support should proceed promptly to intubation and invasive lung protective ventilation strategy. With adherence to these principles, risk of viral spread can be minimized.

Pathophysiological Basis of Acute Respiratory Failure on Non-Invasive Mechanical Ventilation

Noninvasive mechanical ventilation (NIMV) was created for patients who needed noninvasive ventilator support, this procedure decreases the complications associated with the use of endotracheal intubation (ETT). The application of NIMV has acquired major relevance in the last few years in the management of acute respiratory failure (ARF), in patients with hypoxemic and hypercapnic failure. The main advantage of NIMV as compared to invasive mechanical ventilation (IMV) is that it can be used earlier outside intensive care units (ICUs). The evidence strongly supports its use in patients with COPD exacerbation, support in weaning process in chronic obstructive pulmonary disease (COPD) patients, patients with acute cardiogenic pulmonary edema (ACPE), and Immunosuppressed patients. On the other hand, there is poor evidence that supports the use of NIMV in other pathologies such as pneumonia, acute respiratory distress syndrome (ARDS), and during procedures as bronchoscopy, where its use is still controversial because the results of these studies are inconclusive against the decrease in the rate of intubation or mortality.