INS and diabetes mellitus: All studies were included if they met the following eligibility described as PICOS: 1) P (Population): Type 1 Diabetes Mellitus; 2) I (Interventions): Inhaled insulin; 3) C (Control): Insulin route other than inhaled; 4) O (Outcome): comparison between inhaled insulin and other routes of administration of insulin; 5) S (Studies): Human-based Randomized controlled trials published in English only.