Static and Dynamic Measurements of Compliance and Driving Pressure: A Pilot Study.

RATIONALE: Monitoring tidal cycle mechanics is key to lung protection. For this purpose, compliance and driving pressure of the respiratory system are often measured clinically using the plateau pressure, obtained after imposing an extended end-inspiratory pause, which allows for relaxation of the respiratory system and redistribution of inflation volume (method A). Alternative methods for estimating compliance and driving pressure utilize the measured pressure at the earliest instance of zero flow (method B), the inspiratory slope of the pressure-time tracing during inflation with constant flow (method C), and the expiratory time constant (method D). METHODS: Ten passive mechanically ventilated subjects, at a large tertiary referral center, underwent measurements of compliance and driving pressure using the four different methods. The inspiratory tidal volume, inspiratory to expiratory ratio, and positive end expiratory pressures were then adjusted from baseline and the measurements re-obtained. RESULTS: Method A yielded consistently higher compliance and lower driving pressure calculations compared to methods B and C. Methods B and C most closely approximated one another. Method D did not yield a consistent reliable pattern. CONCLUSION: Static measurements of compliance and driving pressure using the plateau pressure may underestimate the maximum pressure experienced by the most vulnerable lung units during dynamic inflation. Utilizing the pressure at zero flow as a static measurement, or the inspiratory slope as a dynamic measurement, may calculate a truer estimate of the maximum alveolar pressure that generates stress upon compromised lung units.

Dorsal Push and Abdominal Binding Improve Respiratory Compliance and Driving Pressure in Proned Coronavirus Disease 2019 Acute Respiratory Distress Syndrome.

We describe seven proned patients with coronavirus disease 2019-related acute respiratory distress syndrome in whom a paradoxical decrease in driving pressure reversibly occurred during passive, volume-controlled ventilation when compressing the lower back by a sustained "dorsal push." We offer a potential explanation for these unexpected observations and suggest the possible importance of eliciting this response for lung-protective ventilation of similar patients. DESIGN/SETTING: Case series at a single teaching hospital affiliated with the University of Minnesota. Measurements were recorded from continuously monitored airway pressure and flow data. PATIENTS: Nonconsecutive and nonrandomized sample of coronavirus disease 2019 acute respiratory distress syndrome patients who were already prone and paralyzed for optimized lung protective clinical management while inhaling pure oxygen. INTERVENTIONS: Sustained, firm manual pressure applied over the lower back in all patients, followed by abdominal binding in a subset of these. MEASUREMENTS AND MAIN RESULTS: Respiratory system driving pressure declined and respiratory system compliance improved in seven patients with the dorsal push maneuver. In a subset of four of these, abdominal binding sustained those improvements over >3 hours. CONCLUSIONS: Sustained compressive force applied to the dorsum of the passive and prone patient with severe respiratory failure due to coronavirus disease pneumonia may elicit a paradoxical response characterized by improved compliance and for a given tidal volume, lower plateau, and driving pressures. Such findings, which suggest end-tidal overinflation within the aerated part of the diseased lung despite the already compressed anterior chest wall of prone positioning, complement and extend those observations recently described for the supine position in coronavirus disease 2019 acute respiratory distress syndrome.

Evaluating Yield of 19 Versus 21 G EBUS-TBNA Needles: A Prospective Study.

BACKGROUND: Controversy remains regarding the effect of needle size on the diagnostic yield of endobronchial ultrasound (EBUS)-guided transbronchial needle aspiration. We conducted a prospective study comparing the diagnostic yield of 19 and 21 G EBUS needles and hypothesized that the 19 G have a greater EBUS-guided transbronchial needle aspiration diagnostic yield as compared with the 21 G needle. METHODS: A total of 60 patients undergoing EBUS-guided transbronchial needle aspiration were enrolled with informed consent. Both 19 and 21 G needles were used at each lymph node station in alternating fashion, we randomized which needle, to begin with. Two rapid on-site cytology evaluation stations were present and assigned to one of the 2 needles. They reported sample adequacy and prepared a separate cell block per lymph node sampled for their assigned needle. RESULTS: A total of 141 lymph nodes were analyzed. Diagnosis included 69 benign lymph nodes, 47 malignant lymph nodes, 22 noncaseating granulomas, and 3 infected lymph nodes. Five hundred seventy-three passes (average: 4.1 passes/lymph node) were done with 19 G and 581 passes with 21 G needles (average: 4.1 passes/lymph node). Diagnostic yield was similar between 19 and 21 G needles overall (89.4% vs. 88.7%, P=0.71). The 19 G needles showed higher smear cellularity (32.6% vs. 13.0%, P=0.05), and rapid on-site cytology evaluation adequacy (84.8% vs. 63.0%, P=0.004) in lymph nodes with cancer diagnosis. In 7 of the 141 lymph nodes, samples from only one of the needles provided the final diagnosis. CONCLUSION: There is no difference in the overall diagnostic yield between 19 and 21 G needles. Further studies are needed to confirm the trend of the superiority of 19 G in cancerous lymph nodes.

Clinical and Sociocultural Factors Associated With Failure to Escalate Care of Deteriorating Patients.

In-hospital medical emergencies occur frequently. Understanding how clinicians respond to deteriorating patients outside the intensive care unit (ICU) could improve "rescue" interventions and rapid response programs. This was a qualitative study with interviews with 40 clinicians caring for patients who had a "Code Blue" activation or an unplanned ICU admission at teaching hospitals over 7 months. Four study physicians independently analyzed interview transcripts; refined themes were linked to the transcript using text analysis software. Nine themes were found to be associated with clinicians' management of deteriorating patients. Multiple human biases influence daily care for deteriorating hospitalized patients. A novel finding is that "moral distress" affects escalation behavior for patients with poor prognosis. Most themes indicate that ward culture influences clinicians to wait until the last minute to escalate care despite being worried about the patients' condition.