A Human Factors Approach to Neonatal Positive Pressure Ventilation

Abstract

In the first minutes after birth, a newborn must transition from oxygenation in the fluid-filled womb to pulmonary gas exchange through the lungs. If the neonate is experiencing apnea, bradycardia, or is gasping for air, clinicians will initiate neonatal resuscitation. Neonatal positive pressure ventilation (PPV) is the single most effective step in the resuscitation of compromised newborn infants. PPV is a form of respiratory ventilation that delivers pressurized air from an external source to the lungs through a face mask, typically applied over the mouth and nose of the neonate. Approximately five to ten million newborns receive PPV with a face mask every year. PPV can be administered with a variety of devices, masks, and strategies for holding the face mask. Care must be taken when holding the mask during PPV, as applying too much force has potential to cause an injury, close off the airway, or trigger a trigeminocardiac reflex, inducing apnea and bradycardia. Alternatively, applying insufficient force will contribute to leakage and inadequate air delivery. Prior to this work, there was no quantitative interaction force data to support training and best practices when performing PPV. Healthcare professionals (HCPs) also face a number of ergonomic issues while administering PPV, potentially contributing to fatigue and musculoskeletal injury risk. This dissertation applies human factors engineering methodologies to numerous challenges experienced during neonatal PPV, with the goal of acquiring novel data for applications in training and administration.

An applied force measurement system was developed and implemented for data collection in three human-subjects studies. The system consists of microforce sensors aligned on the face of a full-term infant manikin, a load cell under the manikin's head, and a corresponding software interface to provide real-time force feedback. A novel dataset of applied forces and force symmetry was collected in the first study, when HCPs with varying amounts of experience ventilated the manikin with multiple types of PPV devices and masks. Device type impacted the total applied compressive force, and experts applied forces more symmetrically than novices. The second study expands on these results by drawing a relationship between applied forces and ventilation parameters and by evaluating multiple mask hold strategies. A correlation between increasing force and decreasing leak was identified, indicating that clinicians applied additional force as a strategy to reduce leak. However, low leak was achieved with small applied forces for all PPV conditions tested. HCPs donned wearable sensors in the second study to assess posture and muscle behavior when using different PPV devices and mask hold strategies. These biometric data provide novel insight into clinician fatigue and musculoskeletal injury risk during PPV administration, and results suggest the use of a T-piece resuscitator to support clinician safety. Finally, the third study explores the impact of real-time applied force feedback on PPV training with novices. Though brief exposure to real-time force feedback did not translate to significant changes in applied forces, the implementation of force data into training remains an important topic for further examination. Modifications to the force information format, such as providing a force symmetry index, could reduce cognitive workload and prove beneficial for the learner. This research advances understanding and presents human factors evaluations of neonatal PPV from multiple perspectives. The findings support clinical recommendations and training practices, extending considerations for patient safety and clinician safety during neonatal PPV administration.