The role of mechanical ventilation in primary graft dysfunction in the postoperative lung transplant recipient: A single center study and literature review

Abstract

Background: Primary graft dysfunction (PGD) is still a major complication in patients undergoing lung transplantation (LTx). Much is unknown about the effect of postoperative mechanical ventilation on outcomes, with debate on the best approach to ventilation.

Aim/purpose: The goal of this study was to generate hypotheses on the association between postoperative mechanical ventilation settings and allograft size matching in PGD development.

Method: This is a retrospective study of LTx patients between September 2011 and September 2018 (n = 116). PGD was assessed according to the International Society of Heart and Lung Transplantation (ISHLT) criteria. Data were collected from medical records, including chest x-ray assessments, blood gas analysis, mechanical ventilator parameters and spirometry.

Results: Positive end-expiratory pressures (PEEP) of 5 cm H₂ O were correlated with lower rates of grade 3 PGD. Graft size was important as tidal volumes calculated according to the recipient yielded greater rates of PGD when low volumes were used, a correlation that was lost when donor metrics were used.

Conclusion: Our results highlight a need for greater investigation of the role donor characteristics play in determining post-operative ventilation of a lung transplant recipient. The mechanical ventilation settings on postoperative LTx recipients may have an implication for the development of acute graft dysfunction. Severe PGD was associated with the use of a PEEP higher than 5 and lower tidal volumes and oversized lungs were associated with lower long-term mortality. Lack of association between ventilatory settings and survival may point to the importance of other variables than ventilation in the development of PGD.

Keywords: lung transplant recipients; postoperative mechanical ventilation; primary graft dysfunction; protective lung ventilation.

FIGURE 1

PGD Incidence Correlated to Size Matching of the Graft. Grafts were defined as undersized when the predicted total lung capacity (pTLC) ratio of donor to recipient was less than 0.95. Matched grafts were considered to be those in the ratio range of 0.95–1.05 while values above 1.05 were allocated as oversized. Both undersized and oversized grafts (A) had a trend of slightly PGD grade 1 or 2 and grade 3 relative to matched grafts. The relationship between size matching and graft dysfunction was then also considered specifically among those patients who received a tidal volume less than 6 ml/kg when calculated according to the donor (B). * p < .05, ** p < .01. PGD, primary graft dysfunction

FIGURE 2

Kaplan‐Meier plot. Survival in lung transplant recipients was stratified according to primary grade dysfunction (PGD) classifications and was tracked through a follow up time of July 17, 2020. No PGD, n = 18; PGD grade 1 or 2, n = 50; PGD grade 3, n = 47

FIGURE 3

Survival is Related to Size Matching in COPD/Emphysema/A1ATD Patients. Patients were assessed for their status through July 2020 and classified according to their graft pTLC ratio. Oversized was defined as a graft with a ratio greater than 1.05. The relationship between the size of the graft and survival was then considered with regard to the diagnosis of the recipient, with COPD/emphysema/A1ATD emerging as having a significant relationship. * p < .05, ** p < .01. COPD, chronic obstructive pulmonary disease; A1ATD, alpha‐1 antitrypsin deficiency

FIGURE 4

Correlation of Protective Volumes and PGD Rates. Patient samples (n = 115) were categorized by the ventilation pressures they received and then by the grade of primary graft dysfunction (PGD), being labelled as either having no PGD, PGD grade 1 or 2 or PGD grade 3. Incidence of PGD was determined within the first 72 h following transplantation. The patients with peak expiratory end pressures (PEEP) of 5 cm H₂o were also those who (A) had significantly less grade 3 dysfunction compared to grade 1 or 2. (B) demonstrates the correlations between driving pressure and PGD grades. Tidal volume was calculated according to either donor (C) or recipient (D). PGD grade 3 compared to grade 1 or 2 was found to be correlated with the tidal volume (TV) calculated according to the recipient (D)