Experimental study on the efficiency and safety of the manual hyperinflation maneuver as a secretion clearance technique

Abstract

OBJECTIVE: To evaluate, in a lung model simulating a mechanically ventilated patient, the efficiency and safety of the manual hyperinflation (MH) maneuver as a means of removing pulmonary secretions. METHODS: Eight respiratory therapists (RTs) were asked to use a self-inflating manual resuscitator on a lung model to perform MH as if to remove secretions, under two conditions: as routinely applied during their clinical practice; and after receiving verbal instructions based on expert recommendations. In both conditions, three clinical scenarios were simulated: normal lung function, restrictive lung disease, and obstructive lung disease. RESULTS: Before instruction, it was common for an RT to compress the resuscitator bag two times, in rapid succession. Proximal pressure (Pprox) was higher before instruction than after. However, alveolar pressure (Palv) never exceeded 42.5 cmH2O (median, 16.1; interquartile range [IQR], 11.7-24.5), despite Pprox values as high as 96.6 cmH2O (median, 36.7; IQR, 22.9-49.4). The tidal volume (VT) generated was relatively low (median, 640 mL; IQR, 505-735), and peak inspiratory flow (PIF) often exceeded peak expiratory flow (PEF), the median values being 1.37 L/s (IQR, 0.99-1.90) and 1.01 L/s (IQR, 0.55-1.28), respectively. A PIF/PEF ratio < 0.9 (which theoretically favors mucus migration toward the central airways) was achieved in only 16.7% of the maneuvers. CONCLUSIONS: Under the conditions tested, MH produced safe Palv levels despite high Pprox. However, the MH maneuver was often performed in a way that did not favor secretion removal (PIF exceeding PEF), even after instruction. The unfavorable PIF/PEF ratio was attributable to overly rapid inflations and low VT.

Manual hyperinflation and the role of physical therapy in intensive care and emergency units

“…This promotes increased expiratory flow rate, moving secretions trapped in the lungs and reopening collapsed lung areas. For Ortiz et al [22], the technique is intended to promote removal of bronchial secretions and re-inflation of atelectasis, improving lung compliance and oxygenation of patients receiving mechanical ventilation.…”

Effects of manual hyperinflation in preterm newborns under mechanical ventilation

“…( 23 - 25 ) The disconnection from the mechanical ventilator and, consequently, the withdrawal of PEEP can mainly cause shearing injury related to the cyclic opening and closing of unstable lung units. ( 26 , 27 )…”

Effect of Inspiratory Time and Lung Compliance on Flow Bias Generated During Manual Hyperinflation: A Bench Study

“…32 Although manual hyperinflation may be commonly delivered with short inspiratory times, 6,7,18 there may be additional factors that facilitate mucus movement under these conditions. It is likely that alterations in V T , 32 airway resistance and airway pressure, 17 manual hyperinflation circuit design, [23][24][25][26] and inclusion of an inspiratory hold 17 may also interact with the expiratory flow bias and alter whether the expiratory flow bias thresholds can be exceeded. Furthermore, gravity, 21 mucus layer thickness and consistency, 19 and patient expiratory effort probably interact with the expiratory flow bias generated and impact mucus Values are mean Ϯ SD.…”

“…15 Consequently, it may be necessary for manual hyperinflation to be performed in a way such that the ratio between the peak inspiratory flow (PIF) and peak expiratory flow (PEF) is Ͻ0.9, and this has been used in some manual hyperinflation research as a theoretical benchmark for whether manual hyperinflation may have been effective in moving mucus. [16][17][18] More recent bench and animal studies suggest that threshold values for the absolute difference between the PIF and the PEF (PIF Ϫ PEF) 19 ϽϪ17 L/min (normal mucus simulant 1.5%) and ϽϪ22 L/min (thick mucus simulant 3.0%) and also possibly the difference between the mean inspiratory flow and the mean expiratory flow (MIF Ϫ MEF) 20 ϽϪ7.9 L/min may also be important thresholds for the movement of mucus. However, to the best of our knowledge, the proposed thresholds have not yet been verified in humans, and it remains unclear whether the precise threshold values can be directly extrapolated to the application of manual hyperinflation in the human lung.…”

“…[23][24][25][26] and expiratory release techniques 11,18 By comparison, less attention has been directed to ways in which a slower inspiratory flow can be generated, such as through a prolonged inspiratory time. Furthermore, it appears in practice that the typical inspiratory time taken to deliver a breath during manual hyperinflation may be much shorter than the early recommendations of 3 s. 10 Most studies suggest that 1-2 s of inspiratory time during manual hyperinflation is commonly used, 16,17,27 possibly due to the physiotherapist accommodating to minimize patient…”